- Recreating the natural evolutionary trend in key microdomains provides an effective strategy for engineering of a thermomicrobial N-demethylase
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N-demethylases have been reported to remove the methyl groups on primary or secondary amines, which could further affect the properties and functions of biomacromolecules or chemical compounds; however, the substrate scope and the robustness of N-demethylases have not been systematically investigated. Here we report the recreation of natural evolution in key microdomains of the Thermomicrobium roseum sarcosine oxidase (TrSOX), an N-demethylase with marked stability (melting temperature over 100 C) and enantioselectivity, for enhanced substrate scope and catalytic efficiency on -C-N-bonds. We obtained the structure of TrSOX by crystallization and X-ray diffraction (XRD) for the initial framework. The natural evolution in the nonconserved residues of key microdomains—including the catalytic loop, coenzyme pocket, substrate pocket, and entrance site—was then identified using ancestral sequence reconstruction (ASR), and the substitutions that accrued during natural evolution were recreated by site-directed mutagenesis. The single and double substitution variants catalyzed the N-demethylation of N-methyl-L-amino acids up to 1800- and 6000-fold faster than the wild type, respectively. Additionally, these single substitution variants catalyzed the terminal N-demethylation of non-amino-acid compounds and the oxidation of the main chain -C-N- bond to a -C=N- bond in the nitrogen-containing heterocycle. Notably, these variants retained the enantioselectivity and stability of the initial framework. We conclude that the variants of TrSOX are of great potential use in N-methyl enantiomer resolution, main-chain Schiff base synthesis, and alkaloid modification or degradation.
- Gu, Zhenghua,Guo, Zitao,Shao, Jun,Shen, Chen,Shi, Yi,Tang, Mengwei,Xin, Yu,Zhang, Liang
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- Highly Stable Zr(IV)-Based Metal-Organic Frameworks for Chiral Separation in Reversed-Phase Liquid Chromatography
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Separation of racemic mixtures is of great importance and interest in chemistry and pharmacology. Porous materials including metal-organic frameworks (MOFs) have been widely explored as chiral stationary phases (CSPs) in chiral resolution. However, it remains a challenge to develop new CSPs for reversed-phase high-performance liquid chromatography (RP-HPLC), which is the most popular chromatographic mode and accounts for over 90% of all separations. Here we demonstrated for the first time that highly stable Zr-based MOFs can be efficient CSPs for RP-HPLC. By elaborately designing and synthesizing three tetracarboxylate ligands of enantiopure 1,1′-biphenyl-20-crown-6, we prepared three chiral porous Zr(IV)-MOFs with the framework formula [Zr6O4(OH)8(H2O)4(L)2]. They share the same flu topological structure but channels of different sizes and display excellent tolerance to water, acid, and base. Chiral crown ether moieties are periodically aligned within the framework channels, allowing for stereoselective recognition of guest molecules via supramolecular interactions. Under acidic aqueous eluent conditions, the Zr-MOF-packed HPLC columns provide high resolution, selectivity, and durability for the separation of a variety of model racemates, including unprotected and protected amino acids and N-containing drugs, which are comparable to or even superior to several commercial chiral columns for HPLC separation. DFT calculations suggest that the Zr-MOF provides a confined microenvironment for chiral crown ethers that dictates the separation selectivity.
- Jiang, Hong,Yang, Kuiwei,Zhao, Xiangxiang,Zhang, Wenqiang,Liu, Yan,Jiang, Jianwen,Cui, Yong
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supporting information
p. 390 - 398
(2021/01/13)
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- Biocatalysts from cyanobacterial hapalindole pathway afford antivirulent isonitriles against MRSA
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Abstract: The emergence of resistance to frontline antibiotics has called for novel strategies to combat serious pathogenic infections. Methicillin-resistant Staphylococcus aureus [MRSA] is one such pathogen. As opposed to traditional antibiotics, bacteriostatic anti-virulent agents disarm MRSA, without exerting pressure, that cause resistance. Herein, we employed a thermophilic Thermotoga maritima tryptophan synthase (TmTrpB1) enzyme followed by an isonitrile synthase and Fe(II)-α-ketoglutarate-dependent oxygenase, in sequence as biocatalysts to produce antivirulent indole vinyl isonitriles. We report on conversion of simple derivatives of indoles to their C3-vinyl isonitriles, as the enzymes employed here demonstrated broader substrate tolerance. In toto, eight distinct L-Tryptophan derived α-amino acids (7) were converted to their bioactive vinyl isonitriles (3) by action of an isonitrile synthase (WelI1) and an Fe(II)-α-ketoglutarate-dependent oxygenase (WelI3) yielding structural variants possessing antivirulence against MRSA. These indole vinyl isonitriles at 10 μg/mL are effective as antivirulent compounds against MRSA, as evidenced through analysis of rabbit blood hemolysis assay. Based on a homology modelling exercise, of enzyme-substrate complexes, we deduced potential three dimensional alignments of active sites and glean mechanistic insights into the substrate tolerance of the Fe(II)-α-ketoglutarate-dependent oxygenase. Graphic abstract: [Figure not available: see fulltext.]
- Bunn, Brittney M,Xu, Mizhi,Webb, Chase M,Viswanathan, Rajesh
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- Protein Engineering of d-Succinylase from Cupriavidus sp. for d-Amino Acid Synthesis and the Structural Implications
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d-Amino acids are important chiral building blocks for pharmaceuticals and agrochemicals. Previously, we have used d-Succinylase (DSA) from Cupriavidus sp. P4-10-C and N-succinyl amino acid racemase (NSAR, EC.4.2.1.113) from Geobacillus stearothermophilus NCA1503 to produce d-amino acids via the dynamic kinetic resolution of N-succinyl-dl-amino acids. However, the use of this bioconversion system remains challenging for industrial application due to the insufficient enantioselectivity of DSA toward N-succinyl-d-amino acids. Therefore, we screened DSA mutants for improved enantioselectivity by directed evolution. Several mutants showed improved enantioseletivity compared to wild-type DSA. L182E mutant had superior enantioselectivity, and the thermal stability was also remarkably improved by this single mutation. We solved the crystal structure of the L182E mutant in complex with succinic acids at a resolution 2.0 ?. The mutated residues in all generated mutants that showed improved enantioselectivity (including the substituted Glu182 in the L182E mutant) are found very close to the active site. The solved crystal structure also provides some rationale to explain the higher thermostability of the L182E mutant compared to wild-type DSA. d-phenylalanine and d-tryptophan were produced in high conversion (approximately 90%) with 98.8% ee and 99.6% ee, respectively, using coupled L182E DSA and NSAR with the one-pot enzymatic method. These data suggested that L182E DSA may be a useful biocatalyst for industrial d-amino acids production. (Figure presented.).
- Azuma, Masayuki,Kumagai, Shinya,Nishiya, Yoshiaki,Sumida, Yosuke,Yamada, Toshihide,Yamasaki, Masayuki
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p. 4770 - 4778
(2021/08/30)
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- Method for photolysis of amido bonds
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The invention discloses a method for photo-splitting amido bonds, wherein the method is mild in reaction condition and can realize splitting of amido bonds by using illumination. The method for photo-splitting the amido bonds comprises the following steps: reacting 2,4-dinitrofluorobenzene with an amino group of a substance which contains alpha amino acid at the tail end and is shown as a structural formula I to generate a compound 1 represented by a structural formula II; and under light irradiation, carrying out amido bond cleavage reaction on the compound 1, wherein R1 is a side chain group of alpha-amino acid, and R2 is aryl, aliphatic hydrocarbon, -CH(R)-COOH or polypeptide.
- -
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Paragraph 0046; 0048-0049; 0110-0113
(2021/06/26)
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- COMPOUNDS AND METHODS FOR SELECTIVE C-TERMINAL LABELING
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The present disclosure relates to compounds and methods for selective C-terminal functionalization of peptides. In certain embodiments, the compounds have improved water-solubility, and are suitable for use in connection with peptide sequencing methodologies.
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-
Paragraph 0033; 0230
(2021/07/24)
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- Three diketomorpholines from a Penicillium sp. (strain G1071)
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Three previously undescribed diketomorpholine natural products, along with the known phenalenones, herqueinone and norherqueinone, were isolated from the mycoparasitic fungal strain G1071, which was identified as a Penicillium sp. in the section Sclerotiora. The structures were established by analyzing NMR data and mass spectrometry fragmentation patterns. The absolute configurations of deacetyl-javanicunine A, javanicunine C, and javanicunine D, were assigned by examining ECD spectra and Marfey's analysis. The structural diversity generated by this fungal strain was interesting, as only a few diketomorpholines (~17) have been reported from nature.
- Al Subeh, Zeinab Y.,Raja, Huzefa A.,Burdette, Joanna E.,Falkinham, Joseph O.,Hemby, Scott E.,Oberlies, Nicholas H.
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- Motobamide, an Antitrypanosomal Cyclic Peptide from a Leptolyngbya sp. Marine Cyanobacterium
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Motobamide (1), a new cyclic peptide containing a C-prenylated cyclotryptophan residue, was isolated from a marine Leptolyngbya sp. cyanobacterium. Its planar structure was established by spectroscopic and MS/MS analyses. The absolute configuration was elucidated based on a combination of chemical degradations, chiral-phase HPLC analyses, spectroscopic analyses, and computational chemistry. Motobamide (1) moderately inhibited the growth of bloodstream forms of Trypanosoma brucei rhodesiense (IC50 2.3 μM). However, it exhibited a weaker cytotoxicity against normal human cells (IC50 55 μM).
- Iwasaki, Arihiro,Jeelani, Ghulam,Kurisawa, Naoaki,Matsubara, Teruhiko,Nozaki, Tomoyoshi,Sato, Toshinori,Suenaga, Kiyotake,Suzuki, Ryota,Takahashi, Hiroki
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p. 1649 - 1655
(2021/05/29)
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- METHODS FOR PRODUCING D-TRYPTOPHAN AND SUBSTITUTED D-TRYPTOPHANS
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Single-module nonribosomal peptide synthetases (NRPSs) and NRPS-like enzymes activate and transform carboxylic acids in both primary and secondary metabolism; and are of great interest due to their biocatalytic potentials. The single-module NRPS IvoA is essential for fungal pigment biosynthesis. As disclosed herein, we show that IvoA catalyzes ATP-dependent unidirectional stereoinversion of L-tryptophan to D-tryptophan with complete conversion. While the stereoinversion is catalyzed by the epimerization (E) domain, the terminal condensation (C) domain stereoselectively hydrolyzes D-tryptophanyl-S-phosphopantetheine thioester and thus represents a noncanonical C domain function. Using IvoA, we demonstrate a biocatalytic stereoinversion/deracemization route to access a variety of substituted D-tryptophan analogs in high enantiomeric excess.
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Page/Page column 6; 10-11; 17
(2021/04/01)
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- Targeted Isolation of Asperheptatides from a Coral-Derived Fungus Using LC-MS/MS-Based Molecular Networking and Antitubercular Activities of Modified Cinnamate Derivatives
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Under the guidance of MS/MS-based molecular networking, four new cycloheptapeptides, namely, asperheptatides A-D (1-4), were isolated together with three known analogues, asperversiamide A-C (5-7), from the coral-derived fungus Aspergillus versicolor. The planar structures of the two major compounds, asperheptatides A and B (1 and 2), were determined by comprehensive spectroscopic data analysis. The absolute configurations of the amino acid residues were determined by advanced Marfey's method. The two structurally related trace metabolites, asperheptatides C and D (3 and 4), were characterized by ESI-MS/MS fragmentation methods. A series of new derivatives (8-26) of asperversiamide A (5) were semisynthesized. The antitubercular activities of 1, 2, and 5-26 against Mycobacterium tuberculosis H37Ra were also evaluated. Compounds 9, 13, 23, and 24 showed moderate activities with MIC values of 12.5 μM, representing a potential new class of antitubercular agents.
- Chao, Rong,Hou, Xue-Mei,Xu, Wei-Feng,Hai, Yang,Wei, Mei-Yan,Wang, Chang-Yun,Gu, Yu-Cheng,Shao, Chang-Lun
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- Modular control ofl-tryptophan isotopic substitutionviaan efficient biosynthetic cascade
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Isotopologs are powerful tools for investigating biological systems. We report a biosynthetic-cascade synthesis of Trp isotopologs starting from indole, glycine, and formaldehyde using the enzymesl-threonine aldolase and an engineered β-subunit of tryptop
- Buller, Andrew R.,Cavagnero, Silvia,McDonald, Allwin D.,Thompson, Clayton M.,Yang, Hanming
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supporting information
p. 4189 - 4192
(2020/06/21)
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- Mild deprotection of the: N-tert -butyloxycarbonyl (N -Boc) group using oxalyl chloride
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We report a mild method for the selective deprotection of the N-Boc group from a structurally diverse set of compounds, encompassing aliphatic, aromatic, and heterocyclic substrates by using oxalyl chloride in methanol. The reactions take place under room temperature conditions for 1-4 h with yields up to 90percent. This mild procedure was applied to a hybrid, medicinally active compound FC1, which is a novel dual inhibitor of IDO1 and DNA Pol gamma. A broader mechanism involving the electrophilic character of oxalyl chloride is postulated for this deprotection strategy. This journal is
- Awuah, Samuel G.,George, Nathaniel,Ofori, Samuel,Parkin, Sean
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p. 24017 - 24026
(2020/07/23)
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- D-Phenylglycine aminotransferase (d-PhgAT)-substrate scope and structural insights of a stereo-inverting biocatalyst used in the preparation of aromatic amino acids
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Enantiopure amines are key building blocks in the synthesis of many pharmaceuticals, so a route to their production is a current goal for biocatalysis. The stereo-inverting d-phenylglycine aminotransferase (d-PhgAT), isolated from Pseudomonas stutzeri ST-201, catalyses the reversible transamination from l-glutamic acid to benzoylformate, yielding α-ketoglutarate and d-phenylglycine (d-Phg). Detailed kinetic analysis revealed a range of amine donor and acceptor substrates that allowed the synthesis of enantiopure aromatic d-amino acids at a preparative scale. We also determined the first X-ray crystal structure of d-PhgAT with its bound pyridoxal 5′-phosphate (PLP) cofactor at 2.25 ? resolution. A combination of structural analysis and site-directed mutagenesis of this class III aminotransferase revealed key residues that are potentially involved in the dual substrate recognition, as well as controlling the stereo-inverting behaviour of d-PhgAT. Two arginine residues (Arg34 and Arg407) are involved in substrate recognition within P and O binding pockets respectively. These studies lay the foundation for further enzyme engineering and promote d-PhgAT as a useful biocatalyst for the sustainable production of high value, aromatic d-amino acids. This journal is
- Akhtar, M. Kalim,Campopiano, Dominic J.,De Cesare, Silvia,Loake, Gary J.,Marles-Wright, Jon,Serpico, Annabel
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p. 6533 - 6543
(2020/11/13)
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- Hydrogen Bond Assisted l to d Conversion of α-Amino Acids
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l to d conversion of unactivated α-amino acids was achieved by solubility-induced diastereomer transformation (SIDT). Ternary complexes of an α-amino acid with 3,5-dichlorosalicylaldehyde and a chiral guanidine (derived from corresponding chiral vicinal diamine) were obtained in good yield as diastereomerically pure imino acid salt complexes and were hydrolysed to obtain enantiopure α-amino acids. A combination of DFT computation, NMR spectroscopy, and crystal structure provide detailed insight into how two types of strong hydrogen bonds assist in rapid epimerization of the complexes that is essential for SIDT.
- Chin, Jik,Fu, Rui,Lough, Alan J.,So, Soon Mog
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p. 4335 - 4339
(2020/02/11)
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- One-Pot Biocatalytic Synthesis of Substituted d -Tryptophans from Indoles Enabled by an Engineered Aminotransferase
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d-Tryptophan and its derivatives are important precursors of a wide range of indole-containing pharmaceuticals and natural products. Here, we developed a one-pot biocatalytic process enabling the synthesis of d-tryptophans from indoles in good yields and high enantiomeric excess (91% to >99%). Our method couples the synthesis of l-tryptophans catalyzed by Salmonella enterica tryptophan synthase with a stereoinversion cascade mediated by Proteus myxofaciens l-amino acid deaminase and an aminotransferase variant that we engineered to display native-like activity toward d-tryptophan. Our process is applicable to preparative-scale synthesis of a broad range of d-tryptophan derivatives containing electron-donating or -withdrawing substituents at all benzene-ring positions on the indole group.
- Parmeggiani, Fabio,Rué Casamajo, Arnau,Walton, Curtis J. W.,Galman, James L.,Turner, Nicholas J.,Chica, Roberto A.
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p. 3482 - 3486
(2019/04/13)
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- Deracemization and stereoinversion to aromatic d-amino acid derivatives with ancestral l-amino acid oxidase
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Enantiomerically pure amino acid derivatives could be foundational compounds for peptide drugs. Deracemization of racemates to l-amino acid derivatives can be achieved through the reaction of evolved d-amino acid oxidase and chemical reductants, whereas deracemization to d-amino acid derivatives has not progressed due to the difficulty associated with the heterologous expression of l-amino acid oxidase (LAAO). In this study, we succeeded in developing an ancestral LAAO (AncLAAO) bearing broad substrate selectivity (13 l-amino acids) and high productivity through an Escherichia coli expression system (50.7 mg/L). AncLAAO can be applied to perform deracemization to d-amino acids in a similar way to deracemization to l-amino acids. In fact, full conversion (>99% ee, d-form) could be achieved for 16 racemates, including nine d,l-Phe derivatives, six d,l-Trp derivatives, and a d,l-phenylglycine. Taken together, we believe that AncLAAO could be a key enzyme to obtain optically pure d-amino acid derivatives in the future.
- Nakano, Shogo,Minamino, Yuki,Hasebe, Fumihito,Ito, Sohei
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p. 10152 - 10158
(2019/10/19)
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- Ultrasound-Controlled Chiral Separation of Four Amino Acids and 2,2,2-Trifluoro-1-(9-anthryl)ethanol
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Chiral separation of 4-hydroxyphenylglycine, phenylglycine, tryptophan, methionine, and 2,2,2-trifluoro-1-(9-anthryl)ethanol (TFAE) was performed under ultrasound reduction at room temperature and high temperature (50 °C). At high temperature (50 °C), both α and Rs were improved slightly under ultrasound reduction as compared to those under non-ultrasonic and ultrasonic irradiation (50 watt/L) conditions. Even at low temperatures, the largest α was observed under ultrasound reduction conditions, except in the case of methionine. However, at low temperature, Rs was reduced under ultrasound (50 watt/L) irradiation, but was improved under ultrasound reduction rather than under the continuous ultrasonic irradiation. Similar to the fact that gradient elution (based on solvent polarity) can improve α, ultrasound reduction can improve α and Rs. Ultrasound reduction is demonstrated to aid the rapid separation of chiral compounds with improved resolution, especially, at high temperatures. Although chromatographic separation using ultrasound has been rarely dealt with until now, ultrasound can be used as an external field in chromatography.
- Lee, Jae Hwan,Ryoo, Jae Jeong
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p. 146 - 149
(2019/02/07)
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- Optogenetic Modulation of a Catalytic Biofilm for the Biotransformation of Indole into Tryptophan
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In green chemical synthesis, biofilms as biocatalysts have shown great promise. Efficient biofilm-mediated biocatalysis requires the modulation of biofilm formation. Optogenetic tools are ideal to control biofilms because light is noninvasive, easily controllable, and cost-efficient. In this study, a gene circuit responsive to near-infrared (NIR) light was used to modulate the cellular level of bis-(3′-5′) cyclic dimeric guanosine monophosphate (c-di-GMP), a central regulator of the prokaryote biofilm lifestyle, which allowed the regulation of biofilm formation by using NIR light. The engineered biofilm was applied to catalyze the biotransformation of indole into tryptophan in submerged biofilm reactors and NIR-light-enhanced biofilm formation resulted in an approximately 30 % increase in tryptophan yield, which demonstrates the feasibility of the application of light to modulate the formation and performance of catalytic biofilms for chemical production. The c-di-GMP-targeted optogenetic approach to modulate catalytic biofilms showcases applications for biofilm-mediated biocatalysis.
- Hu, Yidan,Liu, Xiaobo,Ren, Aloysius Teng Min,Gu, Ji-Dong,Cao, Bin
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p. 5142 - 5148
(2019/11/22)
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- Natural Hydroxamate-Containing Siderophore Acremonpeptides A-D and an Aluminum Complex of Acremonpeptide D from the Marine-Derived Acremonium persicinum SCSIO 115
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Four new hydroxamate-containing natural product cyclopeptides designated acremonpeptides A-D (1-4), together with Al(III)-acremonpeptide D (5) were obtained from the marine fungus Acremonium persicinum SCSIO 115. The planar structures of 1-5 were established on the basis of HRMS as well as 1D and 2D NMR data sets. Moreover, the amino acid absolute configurations were determined using Marfey's method. Compounds 1-5 all feature three 2-amino-5-(N-hydroxyacetamido)pentanoic acid (N5-hydroxy-N5-acetyl-l-ornithine) metal ion chelating moieties. Beyond their discovery and structure elucidation, in vitro bioassays revealed acremonpeptides A (1), B (2), and Al(III)-acremonpeptide D (5) as moderate antiviral agents for herpes simplex virus 1 with EC50 values of 16, 8.7, and 14 μM, respectively.
- Chen, Ziming,Huang, Hongbo,Ju, Jianhua,Luo, Minghe,Song, Xiaoxian,Wang, Xin,Zang, Ruochen
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p. 2594 - 2600
(2019/10/11)
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- Dynamic Kinetic Resolution for Asymmetric Synthesis of L-Noncanonical Amino Acids from D-Ser Using Tryptophan Synthase and Alanine Racemase
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L-Ser is often used to synthesize some significant l-noncanonical α-amino acids(l-ncAAs), which are the prevalent intermediates and precursors for functional synthetic compounds. In this study, threonine aldolase from Escherichia coli k-12 MG1655 has been used to synthesize l-Ser. In contrast to the maximum catalytic capacity (20 g/L) for l-threonine aldolase(LTA), d-Ser was synthesized with high yield (240 g/L) from cheap Gly and paraformaldehyde using d-threonine aldolase (DTA) from Arthrobacter sp ATCC. In order to fully utilize d-Ser and expand the resource of l-Ser, a dynamic kinetic resolution system was constructed to convert d/dl-Ser to l-Ser through combining alanine racemase (Alr) from Bacillus subtilis with l-tryptophan synthase (TrpS) from Escherichia coli k-12 MG1655, and l-ncAAs including l-Trp and l-Cys derivatives were synthesized with excellent enantioselectivity and in high yields. The results indicated l-ncAAs could be efficiently synthesized from d-Ser using this original and green dynamic kinetic resolution system, and the reliable l-Ser resource has been established from simple and achiral substrates.
- Yu, Jinhai,Li, Jing,Gao, Xia,Zeng, Shuiyun,Zhang, Hongjuan,Liu, Junzhong,Jiao, Qingcai
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p. 6618 - 6625
(2019/11/03)
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- Synthesis of 2-D-L-tryptophan by sequential Ir-catalyzed reactions
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Herein, we report a practical synthesis of 2-D-l-tryptophan via sequential Ir-catalyzed C–H borylation, and Ir-catalyzed C-2-deborylative deuteration steps. In this synthetic sequence, deprotection of the Boc and methyl ester groups proved challenging, due to replacement of deuterium with hydrogen. However, mild deprotection conditions were developed to avoid this D/H scrambling. Further, 2-D-L-Tryptophan is stable in many buffers used for biological studies.
- Vallakati, Ravikrishna,Plotnikov, Abel T.,Altman, Ryan A.
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p. 2261 - 2264
(2019/03/04)
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- Complete Stereoinversion of l -Tryptophan by a Fungal Single-Module Nonribosomal Peptide Synthetase
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Single-module nonribosomal peptide synthetases (NRPSs) and NRPS-like enzymes activate and transform carboxylic acids in both primary and secondary metabolism and are of great interest due to their biocatalytic potentials. The single-module NRPS IvoA is essential for fungal pigment biosynthesis. Here, we show that IvoA catalyzes ATP-dependent unidirectional stereoinversion of l-tryptophan to d-tryptophan with complete conversion. While the stereoinversion is catalyzed by the epimerization (E) domain, the terminal condensation (C) domain stereoselectively hydrolyzes d-tryptophanyl-S-phosphopantetheine thioester and thus represents a noncanonical C domain function. Using IvoA, we demonstrate a biocatalytic stereoinversion/deracemization route to access a variety of substituted d-tryptophan analogs in high enantiomeric excess.
- Hai, Yang,Jenner, Matthew,Tang, Yi
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supporting information
p. 16222 - 16226
(2019/10/14)
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- Two novel cyclic depsipeptides Xenematides F and G from the entomopathogenic bacterium Xenorhabdus budapestensis
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Two novel depsipeptides xenematides F and G (1, 2), were isolated from entomopathogenic Xenorhabdus budapestensis SN84 along with a known compound xenematide B. The structures of the two new molecules were elucidated using NMR, MS and Marfey’s method. The xenematide G (2) contains α-aminoheptanoic acid, a non-protein amino acid that is rarely found in secondary metabolites from entomopathogenic bacteria. Xenematides F and G were tested for antibacterial activity. Xenematide G (2) exhibited moderate antibacterial activity.
- Xi, Xuedong,Lu, Xingzhong,Zhang, Xiaodong,Bi, Yuhui,Li, Xiaochun,Yu, Zhiguo
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-
- Enantiomeric separation of β-blockers and tryptophan using heparin as stationary and pseudostationary phases in capillary electrophoresis
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The separation methods of the enantiomers of two β-blockers and tryptophan were studied using capillary electrochromatography with heparin covalently as well as non-covalently, bonded onto the capillary inner wall as stationary phase and electrokinetic chromatography with heparin as pseudostationary phase. In the case of heparin, used as a stationary phase, the method was unable to resolve enantiomers in both cases β-blockers and tryptophan. On the other hand, when heparin was used as a pseudostationary phase, the resolution of the enantiomers was obtained only with 3-aminopropyltriethoxysilane which were immobilised onto the inner phase of the capillary. The results of this study let us infer that the electrostatic, hydrophobic, and steric interactions were involved in the separation mechanisms. The separation was achieved in less than 10?minutes under the optimized conditions: 30?mM phosphate buffer (pH?2.5) with the adding of 15?mg/mL of heparin at 15°C and 10?kV. The usefulness of heparin as a chiral selector both in electrokinetic chromatography using 3-aminopropyltriethoxysilane attached to the capillary was demonstrated for the first time. The developed method was powerful, sensitive, and fast, and it could be considered an important alternative to conventional methods used for chiral separation.
- Liu, Yi,Sombra, Lorena L.,Stege, Patricia W.
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p. 988 - 995
(2018/07/29)
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- A protein-based mixed selector chiral monolithic stationary phase in capillary electrochromatography
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A new mixed selector chiral stationary phase (CSP) was prepared with co-immobilized human serum albumin and cellulase on a poly(glycidylmethacrylate-co-ethylene glycol dimethacrylate) (poly(GMA-co-EDMA)) monolith and the evaluation of its usefulness in chiral separation research was presented. For comparison, two single selector chiral stationary phases (CSPs) were also fabricated with the corresponding proteins. The enantioseparation ability of these CSPs was investigated by capillary electrochromatography (CEC) with various racemates. The mixed selector CSP exhibited a broader range of enantioselectivities than the single selectors and it could separate 10 chiral analytes while the two single selector CSPs resolved 3 and 8 respectively. Moreover, for (±)-warfarin, the enantioresolution was improved on the mixed selector CSP. Meanwhile, compared with the single selector CSPs, no additional preparation stage or reagent consumption was required in the simultaneous immobilization of different proteins, which is more favorable from economical and practical points of view. Consequently, by mixing HSA and cellulase together, the composite column combines the enantioselectivities of both individual proteins, thus expanding their application range practically.
- Xu, Shujuan,Wang, Yuying,Tang, Yixia,Ji, Yibing
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supporting information
p. 13520 - 13528
(2018/08/21)
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- Covalent Organic Frameworks with Chirality Enriched by Biomolecules for Efficient Chiral Separation
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The separation of racemic compounds is important in many fields, such as pharmacology and biology. Taking advantage of the intrinsically strong chiral environment and specific interactions featured by biomolecules, here we contribute a general strategy is developed to enrich chirality into covalent organic frameworks (COFs) by covalently immobilizing a series of biomolecules (amino acids, peptides, enzymes) into achiral COFs. Inheriting the strong chirality and specific interactions from the immobilized biomolecules, the afforded biomolecules?COFs serve as versatile and highly efficient chiral stationary phases towards various racemates in both normal and reverse phase of high-performance liquid chromatography (HPLC). The different interactions between enzyme secondary structure and racemates were revealed by surface-enhanced Raman scattering studies, accounting for the observed chiral separation capacity of enzymes?COFs.
- Zhang, Sainan,Zheng, Yunlong,An, Hongde,Aguila, Briana,Yang, Cheng-Xiong,Dong, Yueyue,Xie, Wei,Cheng, Peng,Zhang, Zhenjie,Chen, Yao,Ma, Shengqian
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supporting information
p. 16754 - 16759
(2018/11/27)
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- N-linoleoylamino acids as chiral probes of substrate binding by soybean lipoxygenase-1
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Lipoxygenases catalyze the oxygenation of polyunsaturated fatty acids and their derivatives to produce conjugated diene hydroperoxides. Soybean lipoxygenase-1 (SBLO-1) has been the subject of intensive structural and mechanistic study, but the manner in which this enzyme binds substrates is uncertain. Previous studies suggest that the fatty acyl group of the substrate binds in an internal cavity near the catalytic iron with the polar end at the surface of the protein or perhaps external to the protein. To test this model, we have investigated two pairs of enantiomeric N-linoleoylamino acids as substrates for SBLO-1. If the amino acid moiety binds external to the protein, the kinetics and product distribution should show little or no sensitivity to the stereochemical configuration of the amino acid moiety. Consistent with this expectation, N-linoleoyl-L-valine (LLV) and N-linoleoyl-D-valine (LDV) are both good substrates with kcat/Km values that are equal within error and about 40% higher than kcat/Km for linoleic acid. Experiments with N-linoleoyl-L-tryptophan (LLT) and N-linoleoyl-D-tryptophan (LDT) were complicated by the low critical micelle concentrations (CMC = 6–8 μM) of these substances. Below the CMC, LDT is a better substrate by a factor of 2.7. The rates of oxygenation of LDT and LLT continue to rise above the CMC, with modest stereoselectivity in favor of the D enantiomer. With all of the substrates tested, the major product is the 13(S)-hydroperoxide, and the distribution of minor products is not appreciably affected by the configuration of the amino acid moiety. The absence of stereoselectivity with LLV and LDV, the modest magnitude of the stereoselectivity with LLT and LDT, and the ability micellar forms of LLT and LDT to increase the concentration of available substrate are all consistent with the hypothesis that the amino acid moiety binds largely external to SBLO-1 and interacts with it only weakly.
- Clapp, Charles H.,Pachuski, Justin,Bassett, Natasha F.,Bishop, Kathleen A.,Carter, Gillian,Young, Megan,Young, Thomas,Fu, Yuhan
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p. 170 - 177
(2018/03/24)
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- Biocatalytic Production of Psilocybin and Derivatives in Tryptophan Synthase-Enhanced Reactions
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Psilocybin (4-phosphoryloxy-N,N-dimethyltryptamine) is the main alkaloid of the fungal genus Psilocybe, the so-called “magic mushrooms.” The pharmaceutical interest in this psychotropic natural product as a future medication to treat depression and anxiety is strongly re-emerging. Here, we present an enhanced enzymatic route of psilocybin production by adding TrpB, the tryptophan synthase of the mushroom Psilocybe cubensis, to the reaction. We capitalized on its substrate flexibility and show psilocybin formation from 4-hydroxyindole and l-serine, which are less cost-intensive substrates, compared to the previous method. Furthermore, we show enzymatic production of 7-phosphoryloxytryptamine (isonorbaeocystin), a non-natural congener of the Psilocybe alkaloid norbaeocystin (4-phosphoryloxytryptamine), and of serotonin (5-hydroxytryptamine) by means of the same in vitro approach.
- Blei, Felix,Baldeweg, Florian,Fricke, Janis,Hoffmeister, Dirk
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p. 10028 - 10031
(2018/07/29)
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- Croissamide, a proline-rich cyclic peptide with an N-prenylated tryptophan from a marine cyanobacterium Symploca sp.
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Croissamide, a proline-rich cyclic peptide that contains an N-prenylated tryptophan, was isolated from a marine cyanobacterium Symploca sp. Its gross structure was determined by spectroscopic analyses, and the absolute configuration was established based on chiral HPLC analyses of acid hydrolysates.
- Iwasaki, Keitaro,Iwasaki, Arihiro,Sumimoto, Shimpei,Sano, Takuya,Hitomi, Yuki,Ohno, Osamu,Suenaga, Kiyotake
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supporting information
p. 3806 - 3809
(2018/09/17)
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- Organocatalytic Enantioselective Addition of α-Aminoalkyl Radicals to Isoquinolines
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With a dual organocatalytic system involving a chiral phosphoric acid and a dicyanopyrazine-derived chromophore (DPZ) photosensitizer and under the irradiation with visible light, an enantioselective Minisci-type addition of α-amino acid-derived redox-active esters (RAEs) to isoquinolines has been developed. A variety of prochiral α-aminoalkyl radicals generated from RAEs were successfully introduced on isoquinolines, providing a range of valuable α-isoquinoline-substituted chiral secondary amines in high yields with good to excellent enantioselectivities.
- Liu, Xiangyuan,Liu, Yang,Chai, Guobi,Qiao, Baokun,Zhao, Xiaowei,Jiang, Zhiyong
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supporting information
p. 6298 - 6301
(2018/10/09)
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- Structure-guided engineering of: Meso -diaminopimelate dehydrogenase for enantioselective reductive amination of sterically bulky 2-keto acids
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meso-Diaminopimelate dehydrogenase (DAPDH) and mutant enzymes are an excellent choice of biocatalysts for the conversion of 2-keto acids to the corresponding d-amino acids. However, their application in the enantioselective reductive amination of bulky 2-keto acids, such as phenylglyoxylic acid, 2-oxo-4-phenylbutyric acid, and indole-3-pyruvic acid, is still challenging. In this study, the structure-guided site-saturation mutagenesis of a Symbiobacterium thermophilum DAPDH (StDAPDH) gave rise to a double-site mutant W121L/H227I, which showed dramatically improved enzyme activities towards various 2-keto acids including these sterically bulky substrates. Several d-amino acids were prepared in optically pure form. The molecular docking of substrates into the active sites of wild-type and mutant W121L/H227I enzymes revealed that the substrate binding cavity of the mutant enzyme was reshaped to accommodate these bulky substrates, thus leading to higher enzyme activity. These results lay a foundation for further shaping the substrate binding pocket and manipulating the interactions between the substrate and binding sites to access highly active d-amino acid dehydrogenases for the preparation of synthetically challenging d-amino acids.
- Cheng, Xinkuan,Chen, Xi,Feng, Jinhui,Wu, Qiaqing,Zhu, Dunming
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p. 4994 - 5002
(2018/10/17)
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- Chromatographic Resolution of α-Amino Acids by (R)-(3,3'-Halogen Substituted-1,1'-binaphthyl)-20-crown-6 Stationary Phase in HPLC
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Three new chiral stationary phases (CSPs) for high-performance liquid chromatography were prepared from R-(3,3'-halogen substituted-1,1'-binaphthyl)-20-crown-6 (halogen = Cl, Br and I). The experimental results showed that R-(3,3'-dibromo-1,1'-binaphthyl)-20-crown-6 (CSP-1) possesses more prominent enantioselectivity than the two other halogen-substituted crown ether derivatives. All twenty-one α-amino acids have different degrees of separation on R-(3,3'-dibromo-1,1'-binaphthyl)-20-crown-6-based CSP-1 at room temperature. The enantioselectivity of CSP-1 is also better than those of some commercial R-(1,1'-binaphthyl)-20-crown-6 derivatives. Both the separation factors (α) and the resolution (Rs) are better than those of commercial crown ether-based CSPs [CROWNPAK CR(+) from Daicel] under the same conditions for asparagine, threonine, proline, arginine, serine, histidine and valine, which cannot be separated by commercial CR(+). This study proves the commercial usefulness of the R-(3,3'-dibromo-1,1'-binaphthyl)-20-crown-6 chiral stationary phase.
- Wu, Peng,Wu, Yuping,Zhang, Junhui,Lu, Zhenyu,Zhang, Mei,Chen, Xuexian,Yuan, Liming
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supporting information
p. 1037 - 1042
(2017/07/25)
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- Processing 2-Methyl- l -Tryptophan through Tandem Transamination and Selective Oxygenation Initiates Indole Ring Expansion in the Biosynthesis of Thiostrepton
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Thiostrepton (TSR), an archetypal member of the family of ribosomally synthesized and post-translationally modified thiopeptide antibiotics, possesses a biologically important quinaldic acid (QA) moiety within the side-ring system of its characteristic thiopeptide framework. QA is derived from an independent l-Trp residue; however, its associated transformation process remains poorly understood. We here report that during the formation of QA, the key expansion of an indole to a quinoline relies on the activities of the pyridoxal-5′-phosphate-dependent protein TsrA and the flavoprotein TsrE. These proteins act in tandem to process the precursor 2-methyl- l-Trp through reversible transamination and selective oxygenation, thereby initiating a highly reactive rearrangement in which selective C2-N1 bond cleavage via hydrolysis for indole ring-opening is closely coupled with C2′-N1 bond formation via condensation for recyclization and ring expansion in the production of a quinoline ketone intermediate. This indole ring-expansion mechanism is unusual, and represents a new strategy found in nature for l-Trp-based functionalization.
- Lin, Zhi,Ji, Jia,Zhou, Shuaixiang,Zhang, Fang,Wu, Jiequn,Guo, Yinlong,Liu, Wen
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p. 12105 - 12108
(2017/09/12)
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- Tetrabutylammonium Fluoride as a Mild and Versatile Reagent for Cleaving Boroxazolidones to Their Corresponding Free α-Amino Acids
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Protection of α-amino acids with 9-borabicyclo[3.3.1]nonane (9-BBN) to give their corresponding boroxazolidones is highly attractive, as it concurrently masks both the amino and the carboxylic acid functionalities. However, the harsh methods required for deprotection of these boroxazolidones have limited their use. Herein, we report that tetrabutylammonium fluoride serves as a mild and versatile reagent that can be used to cleave boroxazolidones to their corresponding free α-amino acids. The reaction conditions were explored, including the use of various nucleophilic fluoride sources, solvents, and reaction temperatures. Nucleophilic fluoride sources comprising an ammonium cation proved superior to other countercations. The scope of the reaction was extended to the cleavage of B,B-diphenyl- and B,B-diethyl boroxazolidone complexes. Furthermore, a wide range of α-amino acid side-chain functionalities were shown to be compatible, including acids, esters, amides, thiols, thioethers, alkynes, phenols, basic heterocycles, and important biorelevant molecules such as glutathione, (S)-adenosyl-l-homocysteine, and l-biocytin.
- Poulie, Christian B. M.,Bunch, Lennart
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supporting information
p. 1475 - 1478
(2017/04/01)
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- Method for Preparing Unnatural Amino Acids
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The present invention relates to a manufacturing method of unnatural amino acids and unnatural amino acids manufactured thereby. Specifically, the present invention relates to an asymmetric synthesis method which can manufacture unnatural amino acids having significantly high optical purity, and to the unnatural amino acids manufactured thereby. A manufacturing method of unnatural amino acids represented by chemical formula 6 or chemical formula 7 comprises the steps of: synthesizing a compound represented by chemical formula 4 or chemical formula 5; manufacturing a diol compound; and manufacturing a carboxylic acid compound.COPYRIGHT KIPO 2016
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Paragraph 0172; 0173; 0218; 0219
(2017/01/09)
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- Thermo-responsive adsorption and separation of amino acid enantiomers using smart polymer-brush-modified magnetic nanoparticles
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Multifunctional magnetic nanoparticles simultaneously possessing thermo-responsive properties and chiral recognition ability show great potential in enantiomeric separation. In this study, a novel type of multifunctional magnetic Fe3O4 nanoparticle, decorated with smart polymer brushes consisting of poly(N-isopropylacrylamide-co-glycidyl methacrylate) chains with pendent β-cyclodextrin (β-CD) units, was fabricated as a chiral nanoselector for the thermo-sensitive selective adsorption and separation of three amino acid enantiomers. These smart polymer brushes were grafted on the surface of Fe3O4 nanoparticles via a combination of surface-initiated atom transfer radical polymerization and ring-opening reaction. The pendent β-CD units can serve as smart receptors for selectively recognizing enantiomeric molecules via formation of stable host-guest inclusion complexes. The thermo-sensitive poly(N-isopropylacrylamide) chains can act as microenvironmental adjustors for tuning the inclusion constants of β-CD toward enantiomeric guest molecules. The prepared multifunctional magnetic nanoparticles exhibit excellent thermo-responsive adsorption and decomplexation performances toward amino acid enantiomers. Via simply changing the operation temperature, the decomplexation of amino acid enantiomers and regeneration of the smart chiral magnetic nanoparticles can be easily achieved. Besides, the magnetic properties of the regenerated smart nanoparticles enable easy recovery under an external magnetic field for reuse. Such multifunctional magnetic nanoparticles with highly chiral recognition capability, excellent thermo-sensitive adsorption and decomplexation properties toward amino acid enantiomers, and recyclability show great potential in chiral separations.
- Song, Ya-Ya,Song, Xiao-Dong,Yuan, Heng,Cheng, Chang-Jing
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p. 3194 - 3207
(2016/05/09)
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- Feed additive method for preparing DL-tryptophan
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The invention provides a method for preparing a feed additive DL-tryptophan. The method comprises the following steps of: 1) preparing indole-3-formaldehyde; 2) preparing aceturic acid; 3) preparing 3-indolyl-2-acetamino acrylic acid; 4) preparing N-acetyltryptophan; 5) preparing the DL-tryptophan. The method for preparing the feed additive DL-tryptophan is easy in acquisition of raw materials, low in raw material cost, high in reaction efficiency, and simple in process; the method can be carried out at the normal temperature and under the normal pressure without environmental pollution.
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-
Paragraph 0027; 0037; 0038
(2016/10/07)
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- New cyclotetrapeptides and a new diketopiperzine derivative from the marine sponge-associated fungus Neosartorya glabra KUFA 0702
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Two new cyclotetrapeptides, sartoryglabramides A (5) and B (6), and a new analog of fellutanine A (8) were isolated, together with six known compounds including ergosta-4, 6, 8 (14), 22-tetraen-3-one, ergosterol 5, 8-endoperoxide, helvolic acid, aszonalenin (1), (3R)-3-(1H-indol-3-ylmethyl)-3,4-dihydro-1H-1,4-benzodiazepine-2,5-dione (2), takakiamide (3), (11aR)-2,3-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepine-5,11(10H,11aH)-dione (4), and fellutanine A (7), from the ethyl acetate extract of the culture of the marine sponge-associated fungus Neosartorya glabra KUFA 0702. The structures of the new compounds were established based on extensive 1D and 2D spectral analysis. X-ray analysis was also used to confirm the relative configuration of the amino acid constituents of sartoryglabramide A (5), and the absolute stereochemistry of the amino acid constituents of sartoryglabramide A (5) and sartoryglabramides B (6) was determined by chiral HPLC analysis of their hydrolysates by co-injection with the D- and L- amino acids standards. Compounds 1-8 were tested for their antibacterial activity against Gram-positive (Escherichia coli ATCC 25922) and Gram-negative (Staphyllococus aureus ATCC 25923) bacteria, as well as for their antifungal activity against filamentous (Aspergillus fumigatus ATCC 46645), dermatophyte (Trichophyton rubrum ATCC FF5) and yeast (Candida albicans ATCC 10231). None of the tested compounds exhibited either antibacterial (MIC > 256 μg/mL) or antifungal activities (MIC > 512 μg/mL).
- Zin, War War May,Buttachon, Suradet,Dethoup, Tida,Fernandes, Carla,Cravo, Sara,Pinto, Madalena M. M.,Gales, Luís,Pereira, José A.,Silva, Artur M. S.,Sekeroglu, Nazim,Kijjoa, Anake
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- Characterization of aromatic aminotransferases from Ephedra sinica Stapf
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Ephedra sinica Stapf (Ephedraceae) is a broom-like shrub cultivated in arid regions of China, Korea and Japan. This plant accumulates large amounts of the ephedrine alkaloids in its aerial tissues. These analogs of amphetamine mimic the actions of adrenaline and stimulate the sympathetic nervous system. While much is known about their pharmacological properties, the mechanisms by which they are synthesized remain largely unknown. A functional genomics platform was established to investigate their biosynthesis. Candidate enzymes were obtained from an expressed sequence tag collection based on similarity to characterized enzymes with similar functions. Two aromatic aminotransferases, EsAroAT1 and EsAroAT2, were characterized. The results of quantitative reverse transcription-polymerase chain reaction indicated that both genes are expressed in young stem tissue, where ephedrine alkaloids are synthesized, and in mature stem tissue. Nickel affinity-purified recombinant EsAroAT1 exhibited higher catalytic activity and was more homogeneous than EsAroAT2 as determined by size-exclusion chromatography. EsAroAT1 was highly active as a tyrosine aminotransferase with α-ketoglutarate followed by α-ketomethylthiobutyrate and very low activity with phenylpyruvate. In the reverse direction, catalytic efficiency was similar for the formation of all three aromatic amino acids using l-glutamate. Neither enzyme accepted putative intermediates in the ephedrine alkaloid biosynthetic pathway, S-phenylacetylcarbinol or 1-phenylpropane-1,2-dione, as substrates.
- Kilpatrick, Korey,Pajak, Agnieszka,Hagel, Jillian M.,Sumarah, Mark W.,Lewinsohn, Efraim,Facchini, Peter J.,Marsolais, Frédéric
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p. 1209 - 1220
(2016/04/26)
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- Stability of His-Phe-Arg-Trp-Pro-Gly-Pro to Leucine Aminopeptidase, Carboxypeptidase Y, and Rat Nasal Mucus, Blood, and Plasma
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The His-Phe-Arg-Trp-Pro-Gly-Pro [ACTH-(6-9)-PGP] peptide was synthesized. Proteolysis of ACTH-(6-9)-PGP and semax (Met-Glu-His-Phe-Pro-Gly-Pro) in the presence of leucine aminopeptidase and carboxypeptidase Y was studied. If the proteolysis of ACTH-(6-9)-PGP is mainly defined by aminopeptidases, the basic metabolite is Trp-Pro-Gly-Pro. Identification of major metabolites of ACTH-(6-9)PGP when incubated with the enzymes in vitro made it possible to evaluate proteolysis pathways of the peptide and prepare necessary amounts of its metabolites for using them as standards. Kinetics of ACTH-(6-9)PGP degradation in the presence of enzyme systems of nasal mucus, blood, and plasma were also explored. It was found that proteolysis of ACTH-(6-9)-PGP in rat blood and plasma occurs mainly under the effect of enzymes whose action is similar to leucine aminopeptidase.
- Shevchenko,Dulov,Andreeva,Nagaev,Shevchenko,Radilov,Myasoedov
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p. 153 - 161
(2016/04/19)
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- Enantiomer separation of propranolol and tryptophan using bovine serum albumin functionalized silica nanoparticles as adsorbents
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The immobilization of popular chiral selectors on the surface of nanomaterials to prepare new chiral adsorbents for preparative chiral separation is a research hotspot in separation science nowadays. In this study, bovine serum albumin (BSA) modified silica nanoparticles were prepared by using polydopamine (PDA) as a versatile multifunctional secondary reaction platform. The preparation method was facile, cost-effective and environmentally friendly. The new chiral adsorbents were then investigated for the separation of representative chiral drug enantiomers. For propranolol and tryptophan, the multi-step adsorption enhanced the chiral performance to a great degree. On increasing the starting percent enantiomeric excess (%, e.e.) of the enantiomeric mixtures, the %, e.e. value of the resulting solution increased to almost 100% under the same operating conditions. For simplicity and rapidness, the results of adsorption were measured by capillary electrophoresis (CE) using carboxymethyl-β-cyclodextrin (CM-β-CD) or α-cyclodextrin (α-CD) as additives into the background electrolyte solution. The experimental results also showed that the thus-prepared nanomaterials could be readily recycled at least three times, demonstrating their great stability and possibility in practical use.
- Li, Wei,Ding, Guo-Sheng,Tang, An-Na
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p. 93850 - 93857
(2015/11/17)
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- t-BUTYLKETONE BINAPHTHOL DERIVATIVES AND PREPARING METHOD THEREOF
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The present disclosure relates to a t-butylketone binaphthol derivative and a method of preparing the same, the t-butylketone binaphthol derivative being a high-efficiency chiral extracting agent which has a very high chiral selectivity enabling to extract an amino acid from an aqueous solution phase to an organic layer and to facilitate its hydrolysis, and enabling a continuous reuse of the organic layer.
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Paragraph 0097
(2017/01/17)
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- Fabrication of mesoporous carbon tube and foam: Application as supports in enantio-selective separation of optically pure amino acid from racemates
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The mesoporous monolithic carbon (MMC) foams and carbon tubes were newly fabricated in cmscale using the mixture of triblock copolymers and phenol/HCHO resin precursors. The regular mesoporosity were formed in the body of MMC foam and carbon fibers. In this work, the organic phases containing chiral ARCA adsorbent and a phase transfer catalyst were coated on the surfaces of mesoporous carbon support, and this ARCA/carbon mixture was adopted for the enantioselective separation of amino acid in the circulation system. (S)-ARCA coated MMC support showed high selcetivity up to 90% for the separation of D-type phenylalanine, serine and tryptophan from racemic mixtures.
- Jeon, Hoon-Gi,Lee, Ju-Hyun,Kim, Gye-Ryung,Park, Da-Min,Kim, Geon-Joong
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p. 334 - 338
(2015/03/18)
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- Immobilization of pepsin on chitosan magnetic nanoparticles and its application in deacetylation of amides
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A core-shell composite of chitosan on Fe3O4 nanoparticles was successfully synthesized and pepsin enzyme was immobilized on it via imine linkages. The supported aspartic protease was characterized by IR spectroscopy and its morphology was studied by X-ray diffraction (XRD) analysis, as well as scanning electron microscopy (SEM) and transmission electron microscopy (TEM), confirming its spheroidal structure. Thermal analysis was carried out by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) methods, revealing its stepwise weight loss. The amounts of Fe3O4, chitosan and enzyme were measured to be 50, 40, and 10 wt%, respectively. The deacetylation of various amides was prosperously accomplished by the immobilized pepsin at room temperature through the suggested mechanism, and the supported enzyme could be separated and reused for at least three cycles. The amount of immobilization was measured to be 99 mg/g of support, and according to vibrating sample magnetometer (VSM) analysis, this magnetic nanocomposite could be proposed for biomedical applications.
- Lakouraj, Moslem Mansour,Maashsani, Azita,Norouzian, Rafieh-Sadat,Mohadjerani, Maryam
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p. 103 - 119
(2015/03/30)
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- Directed evolution of the tryptophan synthase β-subunit for stand-alone function recapitulates allosteric activation
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Enzymes in heteromeric, allosterically regulated complexes catalyze a rich array of chemical reactions. Separating the subunits of such complexes, however, often severely attenuates their catalytic activities, because they can no longer be activated by their protein partners. We used directed evolution to explore allosteric regulation as a source of latent catalytic potential using the β-subunit of tryptophan synthase from Pyrococcus furiosus (PfTrpB). As part of its native αββα complex, TrpB efficiently produces tryptophan and tryptophan analogs; activity drops considerably when it is used as a stand-alone catalyst without the α-subunit. Kinetic, spectroscopic, and X-ray crystallographic data show that this lost activity can be recovered by mutations that reproduce the effects of complexation with the α-subunit. The engineered PfTrpB is a powerful platform for production of Trp analogs and for further directed evolution to expand substrate and reaction scope.
- Buller, Andrew R.,Brinkmann-Chen, Sabine,Romney, David K.,Herger, Michael,Murciano-Calles, Javier,Arnold, Frances H.
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p. 14599 - 14604
(2015/12/05)
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- Enantiospecific C-H Activation Using Ruthenium Nanocatalysts
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The activation of C-H bonds has revolutionized modern synthetic chemistry. However, no general strategy for enantiospecific C-H activation has been developed to date. We herein report an enantiospecific C-H activation reaction followed by deuterium incorporation at stereogenic centers. Mechanistic studies suggest that the selectivity for the α-position of the directing heteroatom results from a four-membered dimetallacycle as the key intermediate. This work paves the way to novel molecular chemistry on nanoparticles.
- Taglang, Céline,Martínez-Prieto, Luis Miguel,Del Rosal, Iker,Maron, Laurent,Poteau, Romuald,Philippot, Karine,Chaudret, Bruno,Perato, Serge,Sam Lone, Ana?s,Puente, Céline,Dugave, Christophe,Rousseau, Bernard,Pieters, Grégory
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supporting information
p. 10474 - 10477
(2015/09/02)
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- Synthesis and Characterization of a Two Stage, Nonlinear Photobase Generator
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Amine photobase generators (PBGs) are uncommon yet useful compounds. Rarer still are examples of PBGs that are active at visible wavelengths. We report the synthesis and characterization of new photolabile amine protecting groups that are active under visible light. The new chromophore, benzothiophene imino-phenylacetonitrile (BTIPA), was synthesized in four steps without use of chromatography and found to release any one of several amines upon exposure to 405 nm light. The chromophore was also demonstrated to be useful as a Merrifield synthesis protecting group. Experimental evidence suggests a sequential, two stage photolysis mechanism which leads to a nonlinear response to dose.
- Hayes, Colin O.,Bell, William K.,Cassidy, Benjamin R.,Willson, C. Grant
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p. 7530 - 7535
(2015/08/18)
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- A thermodynamic insight into the recognition of hydrophilic and hydrophobic amino acids in pure water by aza-scorpiand type receptors
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Interactions of different hydrophilic (His, Asp, Glu,) and hydrophobic (Ala, Phe, Tyr, Trp) amino acids in water with a scorpiand aza-macrocycle (L1) containing a pyridine group in the ring and its derivative (L2) bearing a naphthalene group in the tail have been analysed by potentiometric and calorimetric measurements. Theoretical calculations corroborate that major attractive forces that hold the adduct together are hydrogen bonds and salt-bridges, even though other interactions such as π-stacking or NH+...π may contribute in the case of hydrophobic amino acids and L2. Calorimetric measurements indicate that the interactions between L1 and the different amino acids are principally driven by entropy, often associated with solvation/desolvation processes.
- Blasco, Salvador,Verdejo, Begoa,Bazzicalupi, Carla,Bianchi, Antonio,Giorgi, Claudia,Soriano, Concepcin,Garca-Espaa, Enrique
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supporting information
p. 843 - 850
(2015/02/19)
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- Two-photon sensitive protecting groups operating via intramolecular electron transfer: Uncaging of GABA and tryptophan
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Improved photo-labile protecting groups, with high sensitivity to two-photon excitation, are needed for the controlled release of drugs, as tools in neuroscience and physiology. Here we present a new modular approach to the design of caging groups based on photoinduced electron transfer from an electron-rich two-photon dye to an electron acceptor, followed by scission of an ester to release a carboxylic acid. Three different electron acceptors were tested: nitrobenzyl, phenacyl and pyridinium. The nitrobenzyl system was ineffective, giving only photochemical decomposition and no release of the carboxylic acid. The phenacyl system also performed poorly, liberating the carboxylic acid in 20% chemical yield and 0.2% photochemical yield. The pyridinium system was most successful, and was tested for the release of two carboxylic acids: γ-amino butyric acid (GABA) and tryptophan. The caged GABA undergoes photochemical cleavage with a chemical yield of >95% and a photochemical yield of 1%; it exhibits a two-photon absorption cross section of 1100 GM at 700 nm, corresponding to a two-photon uncaging cross section of 10 ± 3 GM. This journal is
- Korzycka, Karolina A.,Bennett, Philip M.,Cueto-Diaz, Eduardo Jose,Wicks, Geoffrey,Drobizhev, Mikhail,Blanchard-Desce, Mireille,Rebane, Aleksander,Anderson, Harry L.
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p. 2419 - 2426
(2015/03/30)
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- Peptidomimetics comprising N-amino cyclic urea residues and uses thereof
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Novel peptidomimetics comprising N-amino cyclic urea residues are disclosed. Use of such peptidomimetics for modulating the activity of CD36 or IL-1 receptor in a cell, and for treating CD36- or IL-1-related disease, disorder or condition is also described.
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Page/Page column
(2015/04/15)
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