- A facile enantioseparation for amino acids enantiomers using β-cyclodextrins functionalized Fe3O4 nanospheres
-
Herein is presented a strategy for the enantioseparation of amino acids enantiomers using β-CD functionalized Fe3O4 nanospheres, in which β-CD provides the ability to chirally discriminate amino acids enantiomers, while the Fe3O4 nanoparticles serve as magnetic separators.
- Chen, Xin,Rao, Jinan,Wang, Jin,Gooding, J. Justin,Zou, Gang,Zhang, Qijin
-
-
Read Online
- Chiral separation of underivatized amino acids by reactive extraction with palladium-BINAP complexes
-
(Figure Presented) In answer to the need for a more economic technology for the separation of racemates, a novel system for reactive enantioselective liquid-liquid extraction (ELLE) is introduced. Palladium (S)-BINAP complexes are employed as hosts in the separation of underivatized amino acids. The system shows the highest selectivity for the ELLE of tryptophan with metal complexes as hosts reported to date and shows a good selectivity toward a range of natural and unnatural amino acids. Furthermore, the host can be prepared in situ from commerically available compounds. Bulk-membrane transport in the form of U-tube experiments demonstrates the enantioselective and catalytic nature of the transport. The dependency of the system on parameters such as pH, organic solvent, and host-substrate ratio has been established. 31P NMR spectroscopy has been used to confirm the preferred enantiomer in the extraction experiments. The intrinsic selectivity was deduced by determination of the association constants of the palladium complex with the tryptophan enantiomers.
- Verkuijl, Bastiaan J. V.,Minnaard, Adriaan J.,De Vries, Johannes G.,Feringa, Ben L.
-
-
Read Online
- Amino acid ionic liquids as chiral ligands in ligand-exchange chiral separations
-
Recently, amino acid ionic liquids (AAILs) have attracted much research interest. In this paper, we present the first application of AAILs in chiral separation based on the chiral ligand exchange principle. By using 1alkyl-3-methylimidazolium L-proline (L-Pro) as a chiral ligand coordinated with copper(II), four pairs of underivatized amino acid enantiomers - DLphenylalanine (DL-Phe), DL-histidine (DL-His), DL-tryptophane (DL-Trp), and DL-tyrosine (DL-Tyr) - were successfully separated in two major chiral separation techniques, HPLC and capillary electrophoresis (CE), with higher enantioselectivity than conventionally used amino acid ligands (resolution (Rs) = 3.26-10.81 for HPLC; Rs = 1.34-4.27 for CE). Interestingly, increasing the alkyl chain length of the AAIL cation remarkably enhanced the enantioselectivity. It was inferred that the alkylmethylimidazolium cations and L-Pro form ion pairs on the surface of the sta-tionary phase or on the inner surface of the capillary. The ternary copper complexes with L-Pro are consequently attached to the support surface, thus inducing an ion-exchange type of retention for the DL-enantiomers. Therefore, the AAIL cation plays an essential role in the separation. This work demonstrates that AAILs are good alternatives to conventional amino acid ligands for ligand-exchange-based chiral separation. It also reveals the tremendous application potential of this new type of task-specific ILs.
- Liu, Qian,Wu, Kangkang,Tang, Fei,Yao, Lihua,Yang, Fei,Nie, Zhou,Yao, Shouzhuo
-
-
Read Online
- D-Phenylglycine aminotransferase (d-PhgAT)-substrate scope and structural insights of a stereo-inverting biocatalyst used in the preparation of aromatic amino acids
-
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
-
-
Read Online
- Structure elucidation of a new natural diketopiperazine from a Microbispora aerata strain isolated from Livingston Island, Antarctica
-
A new natural diketopiperazine (1) was obtained from the culture broth of Microbispora aerata strain imbas-11A, isolated from penguin excrements collected on the Antarctic Livingston Island. Compound 1 was purified consecutively by solvent extraction, silica gel column chromatography and preparative HPLC. The structure of the compound was elucidated by 1D and 2D NMR experiments and mass spectrometric investigations. The absolute configuration of compound 1 was determined by amino acid analysis and NOESY correlations. A low antiproliferative and cytotoxic effect of trans-cyclo-(D-tryptophanyl-L-tyrosyl) (1) was determined with L-929 mouse fibroblast cells, K-562 human leukemia cells and HeLa human cervix carcinoma. Trans-cyclo-(D-tryptophanyl-L-tyrosyl) (1) did not show antimicrobial activity at a concentration of 50 μg per disc against Bacillus subtilis, Staphylococcus aureus, Streptomyces viridochromogenes, Escherichia coli, Candida albicans and Mucor miehei.
- Ivanova, Veneta,Laatsch, Hartmut,Kolarova, Mariana,Aleksieva, Krasja
-
-
Read Online
- Targeted Isolation of Asperheptatides from a Coral-Derived Fungus Using LC-MS/MS-Based Molecular Networking and Antitubercular Activities of Modified Cinnamate Derivatives
-
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
-
-
Read Online
- Ultrasound-Controlled Chiral Separation of Four Amino Acids and 2,2,2-Trifluoro-1-(9-anthryl)ethanol
-
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
-
-
Read Online
- Coordination properties of 3-functionalised β-cyclodextrins: Thermodynamic stereoselectivity of copper(II) complexes of the 3-histamine derivative and its exploitation in ligand-exchange capillary electrophoresis
-
A histamine derivative of β-cyclodextrin functionalised at the secondary rim was synthesised and characterised by optical and NMR spectroscopy. Its binary systems both with proton and copper(II) were thermodynamically characterised through pH-metric potentiometry. In addition, the ternary systems with the enantiomers of tryptophan, phenylalanine and alanine were investigated. Thermodynamic stereoselectivity was observed for both the tryptophan and phenylalanine enantiomers. The properties of the synthesised cyclodextrin derivative as a chiral selector were verified in chiral ligand-exchange capillary electrophoresis (CLECE) towards the enantiomeric pairs of some amino acids. A β-cyclodextrin histamine-functionalised at the secondary rim was synthesised and characterised as a chiral selector of aromatic amino acids.
- Giuffrida, Alessandro,Cucinotta, Vincenzo,MacCarrone, Giuseppe,Messina, Marianna,Rizzarelli, Enrico,Vecchio, Graziella
-
-
Read Online
- Thermo-responsive adsorption and separation of amino acid enantiomers using smart polymer-brush-modified magnetic nanoparticles
-
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
-
-
Read Online
- Reversal of optical induction in transamination by regioisomeric bifunctionalized cyclodextrins
-
Two isomeric compounds have been synthesized carrying a pyridoxamine on C-6 of β-cyclodextrin and an imidazole unit on C-6 of the neighboring glucose residue. Each one stereoselectively transaminates phenylpyruvic acid to produce phenylalanine, and with opposite stereochemical preferences. Structure determinations by X-ray crystallography and NMR spectroscopy indicate that the imidazole units serve to block proton addition from their side, rather than acting to protonate the transamination intermediates. Related cyclodextrin-pyridoxamine compounds had been reported carrying ethylenediamine units instead of imidazoles, and high enantioselectivities in transamination were claimed. Our work indicates that these claims are incorrect, and that only poor selectivities are seen that are often unrelated to the position of the ethylenediamine units. Neither of these transaminating systems yet approaches the enantioselectivity seen with a pyridoxamine carrying a chirally mounted internal base group. Copyright (C) 1999 Elsevier Science Ltd.
- Fasella, Elisabetta,Dong, Steven D.,Breslow, Ronald
-
-
Read Online
- Protein Engineering of d-Succinylase from Cupriavidus sp. for d-Amino Acid Synthesis and the Structural Implications
-
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
-
-
Read Online
- Separation of tryptophan enantiomers by ligand-exchange chromatography with novel chiral ionic liquids ligand
-
Chiral ionic liquids (CILs) with amino acids as cations have been applied as novel chiral ligands coordinated with Cu2+ to separate tryptophan enantiomers in ligand exchange chromatography. Four kinds of amino acid ionic liquids, including [L-Pro][CF3COO], [L-Pro][NO3], [L-Pro]2[SO4], and [L-Phe][CF3COO] were successfully synthesized and used for separation of tryptophan enantiomers. To optimize the separation conditions, [L-Pro][CF3COO] was selected as the model ligand. Some factors influencing the efficiency of chiral separation, such as copper ion concentration, CILs concentration, methanol ratio (methanol/H2O, v/v), and pH, were investigated. The obtained optimal separation conditions were as follows: 8.0 mmol/L Cu(OAc)2, 4.0 mmol/L [L-Pro][CF3COO],and 20% (v/v) methanol at pH 3.6. Under the optimum conditions, acceptable enantioseparation of tryptophan enantiomers could be observed with a resolution of 1.89. The results demonstrate the good applicability of CILs with amino acids as cations for chiral separation. Furthermore, a comparative study was also conducted for exploring the mechanism of the CILs as new ligands in ligand exchange chromatography.
- Qing, Haiqun,Jiang, Xinyu,Yu, Jingang
-
-
Read Online
- Hydrogen Bond Assisted l to d Conversion of α-Amino Acids
-
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
-
-
Read Online
- N-linoleoylamino acids as chiral probes of substrate binding by soybean lipoxygenase-1
-
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
-
-
Read Online
- Preparative separation of enantiomers based on functional nucleic acids modified gold nanoparticles
-
The preparative-scale separation of chiral compounds is vitally important for the pharmaceutical industry and related fields. Herein we report a simple approach for rapid preparative separation of enantiomers using functional nucleic acids modified gold nanoparticles (AuNPs). The separation of DL-tryptophan (DL-Trp) is demonstrated as an example to show the feasibility of the approach. AuNPs modified with enantioselective aptamers were added into a racemic mixture of DL-Trp. The aptamer-specific enantiomer (L-Trp) binds to the AuNPs surface through aptamer-L-Trp interaction. The separation of DL-Trp is then simply accomplished by centrifugation: the precipitate containing L-Trp bounded AuNPs is separated from the solution, while the D-Trp remains in the supernatant. The precipitate is then redispersed in water. The aptamer is denatured under 95 °C and a second centrifugation is then performed, resulting in the separation of AuNPs and L-Trp. The supernatant is finally collected to obtain pure L-Trp in water. The results show that the racemic mixture of DL-Trp is completely separated into D-Trp and L-Trp, respectively, after 5 rounds of repeated addition of fresh aptamer-modified AuNPs to the DL-Trp mixture solution. Additionally, the aptamer-modified AuNPs can be repeatedly used for at least eight times without significant loss of its binding ability because the aptamer can be easily denatured and renatured in relatively mild conditions. The proposed approach could be scaled up and extended to the separation of other enantiomers by the adoption of other enantioselective aptamers. Chirality 25:751-756, 2013. 2013 Wiley Periodicals, Inc.
- Huang, Rong,Wang, Daifang,Liu, Shuzhen,Guo, Longhua,Wang, Fangfang,Lin, Zhenyu,Qiu, Bin,Chen, Guonan
-
-
Read Online
- Immobilization of HSA on polyamidoamine-dendronized magnetic microspheres for application in direct chiral separation of racemates
-
Magnetic microspheres containing dendrimers and chiral selectivity show great performance for applications in pharmacology and biomedicine. In this study, a novel chiral magnetic nano-selector was prepared by immobilizing human serum albumin (HSA) on polyamidoamine dendrimer (PAMAM)-modified magnetic silica microspheres (PMSMs). The functionalized magnetic microspheres had a core-shell structure, with an average diameter of 600 nm. They exhibited strong magnetic response, with a high magnetization saturation of 46 emu g-1. UV-vis spectrophotometry and confocal laser scanning microscopy indicated that the HSA binding capacity on PMSM increased with increasing PAMAM generation. An immunoaffinity assay indicated that HSA retained a high level of activity, after immobilization on PMSM. HSA-immobilized PMSM (HSA-PMSM) was applied in the direct chiral separation of three biological racemates. The separation results show that HSA-PMSM selectively interacted with the racemates, and exhibited different activity toward each enantiomer. The results obtained by CD and CE indicated that HSA immobilized on third-generation PMSM possessed excellent chiral separation capability and biocompatibility. The chiral recognition capability of HSA-PMSM increased with increasing PAMAM generation. The chiral magnetic nano-selector is effective for the enantiomeric separation of chiral drugs, and has potential application in pharmacological and biomedical research. The 2014 Royal Society of Chemistry.
- Yang, Yi,Wu, Jingwei,Su, Ping,Yang, Ye,Huang, Jun,Wang, Yingying
-
-
Read Online
- ASYMMETRIC SYNTHESIS OF α-AMINO ACIDS BY NONENZYMATIC TRANSAMINATION. VERSATILITY OF THE REACTION AND ENANTIOMERIC EXCESS OF THE PRODUCTS
-
Diverse α-keto acids were transformed into the corresponding α-amino acids enantiomeric excess ranging from 60 to 96percent by the reaction with chiral pyridoxamine analog, (R)- or (S)-15-aminomethyl-14-hydroxy-5,5-dimethyl-2,8-dithia(2,5)pyridinophane (4), and Zn2+ in the molar ratio of 2:1, in methanol.The use of the S enantiomer of 4 gave (R)-α-amino acids, and vice versa.
- Tachibana, Yoji,Ando, Makoto,Kuzuhara, Hiroyoshi
-
-
Read Online
- Structural identification of the degradation products of the antitumor peptide antagonist [Arg6, D-Trp7,9, MePhe8]substance P (6-11)
-
The basic hexapeptide antagonist [Arg6, D-Trp7,9, MePhe8]substance P (6-11) was degraded in acid and alkaline media. In acid solution, only one degradation product is found whereas in alkaline solution at least six products are formed. These compounds were analytically characterized and structurally identified by reversed-phase high-performance liquid chromatography, capillary electrophoresis, liquid chromatography/mass spectrometry, fast atom bombardment tandem mass spectrometry, optical rotation analysis, and chiral gas chromatography. The product formed in acidic solution is the terminally deamidated antagonist [Arg6, D-Trp7,9, MePhe8]substance P (6-11); this product was also found in alkaline degradation mixtures. Other important degradation products originate from racemization of the amino acid residue L-Met, formation of ornithine from Arg, and the oxidation of Met to its sulfoxide form.
- Reubsaet,Beijnen,Bult,Hop,Vermaas,Kellekule,Kettenes-Van Den Bosch,Underberg
-
-
Read Online
- METHODS FOR PRODUCING D-TRYPTOPHAN AND SUBSTITUTED D-TRYPTOPHANS
-
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.
- -
-
Page/Page column 6; 10-11; 17
(2021/04/01)
-
- Highly Stable Zr(IV)-Based Metal-Organic Frameworks for Chiral Separation in Reversed-Phase Liquid Chromatography
-
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
-
supporting information
p. 390 - 398
(2021/01/13)
-
- One-Pot Biocatalytic Synthesis of Substituted d -Tryptophans from Indoles Enabled by an Engineered Aminotransferase
-
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.
-
p. 3482 - 3486
(2019/04/13)
-
- Deracemization and stereoinversion to aromatic d-amino acid derivatives with ancestral l-amino acid oxidase
-
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
-
p. 10152 - 10158
(2019/10/19)
-
- Two novel cyclic depsipeptides Xenematides F and G from the entomopathogenic bacterium Xenorhabdus budapestensis
-
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
-
-
- Complete Stereoinversion of l -Tryptophan by a Fungal Single-Module Nonribosomal Peptide Synthetase
-
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
-
supporting information
p. 16222 - 16226
(2019/10/14)
-
- Structure-guided engineering of: Meso -diaminopimelate dehydrogenase for enantioselective reductive amination of sterically bulky 2-keto acids
-
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
-
p. 4994 - 5002
(2018/10/17)
-
- Enantiomeric separation of β-blockers and tryptophan using heparin as stationary and pseudostationary phases in capillary electrophoresis
-
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.
-
p. 988 - 995
(2018/07/29)
-
- A protein-based mixed selector chiral monolithic stationary phase in capillary electrochromatography
-
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
-
supporting information
p. 13520 - 13528
(2018/08/21)
-
- Covalent Organic Frameworks with Chirality Enriched by Biomolecules for Efficient Chiral Separation
-
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
-
supporting information
p. 16754 - 16759
(2018/11/27)
-
- Chromatographic Resolution of α-Amino Acids by (R)-(3,3'-Halogen Substituted-1,1'-binaphthyl)-20-crown-6 Stationary Phase in HPLC
-
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
-
supporting information
p. 1037 - 1042
(2017/07/25)
-
- Method for Preparing Unnatural Amino Acids
-
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
- -
-
Paragraph 0172; 0173; 0218; 0219
(2017/01/09)
-
- Enantiomer separation of propranolol and tryptophan using bovine serum albumin functionalized silica nanoparticles as adsorbents
-
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
-
p. 93850 - 93857
(2015/11/17)
-
- ｔ-BUTYLKETONE BINAPHTHOL DERIVATIVES AND PREPARING METHOD THEREOF
-
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.
- -
-
Paragraph 0097
(2017/01/17)
-
- SEPARATING AGENT AND MANUFACTURING METHOD THEREOF
-
An embodiment of the present invention is a separating agent wherein a group represented by a chemical formula of: or a group represented by a chemical formula of: is introduced on a surface thereof.
- -
-
Paragraph 0067; 0068; 0069; 0070; 0071; 0072; 0111; 0112
(2015/01/07)
-
- Chiral ligand-exchange resolution of underivatized amino acids on a dynamically modified stationary phase for RP-HPTLC
-
The synthesis of Spi(τ-dec), derived from the selective alkylation of L-spinacine (4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid) at the τ-nitrogen of its heteroaromatic ring, with a linear hydrocarbon chain of 10 carbon atoms, is described here for the first time. Spi(τ-dec) was successfully employed in the past to prepare home-made chiral columns for chiral ligand-exchange high-performance liquid chromatography. In the present article a new method is described, using Spi(τ-dec) as a chiral selector in high-performance thin-layer chromatography (HPTLC): commercial hydrophobic plates were first coated with Spi(τ-dec) and then treated with copper sulfate. The performance of this new chiral stationary phase was tested against racemic mixtures of aromatic amino acids, after appropriate optimization of both the conditions of preparation of the plates and the mobile phase composition. The enantioselectivity values obtained for the studied compounds were higher than those reported in the literature for similar systems. The method employed here for the preparation of chiral HPTLC plates proved practical, efficient, and inexpensive. Chirality 26:313-318, 2014. 2014 Wiley Periodicals, Inc.
- Remelli, Maurizio,Faccini, Stefania,Conato, Chiara
-
p. 313 - 318
(2014/06/09)
-
- Fabrication of meso/macroporous carbon monolith and its application as a support for adsorptive separation of D-amino acid from racemates
-
(S)-Alanine Racemase Chiral Analogue ((S)-ARCA) was used as an efficient adsorbent for the selective separation of D-amino acids (D-AAs), which are industrially important as chiral building blocks for the synthesis of pharmaceutical intermediates. The organic phase, containing (S)-ARCA adsorbent and phase transfer reagents, such as ionic liquid type molecules (Tetraphenylphosphonium chloride (TPPC), Octyltriphenylphosponium bromide (OTPPBr)), were coated on the surfaces of mesoporous carbon supports. For the immobilization of chiral adsorbents, meso/macroporous monolithic carbon (MMC), having bimodal pore structures with high surface areas and pore volumes, were fabricated. The separation of chiral AAs by adsorption onto the heterogeneous (S)-ARCA was performed using a continuous flow type packed bed reactor system. The effects of loading amount of ARCA on the support, the molar ratio of AA to ARCA, flow rates, and the type of phase transfer reagent (PTR) on the isolation yields and the optical purity of product D-AAs were investigated. D-AAs were selectively combined to (S)-ARCA through imine formation reaction in an aqueous basic solution of racemic D/L-AA. The (S)-ARCA coated MMC support showed a high selectivity, up to 95 ee%, for the separation of D-type phenylalanine, serine and tryptophan from racemic mixtures. The ionic liquids TPPC and OTPPBr exhibited superior properties to those of the ionic surfactant Cetyltrimethyl ammonium bromide (CTAB), as a PTR, showing constant optical purities of 95 ee%, with high isolation yields for five repeated reuses. The unique separation properties in this heterogeneous adsorption system should provide for an expansion of the applications of porous materials for commercial processes.
- Park, Da-Min,Jeon, Sang Kwon,Yang, Jin Yong,Choi, Sung Dae,Kim, Geon Joong
-
p. 1720 - 1726
(2014/07/07)
-
- Enantioselective absorption of enantiomers with maleic anhydride-β-cyclodextrin modified magnetic microspheres
-
Multifunctional magnetic microspheres have enormous potential in diverse fields. In this work, surface chiral-modified magnetic microspheres as chiral selectors, are prepared by polymerizing maleic anhydride-β-cyclodextrin (MAH-β-CD) for the enantioselective absorption of four enantiomers. The successful grafting of MAH-β-CD onto the surface of magnetic microspheres is confirmed by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric analysis. The prepared functional microspheres have a three-ply structure with an average particle size of 550 nm and a high saturation magnetization of 60 emu g-1. The amount of MAH-β-CD modified on the P(MBAAm)@Fe3O4 was about 149.1 mg g-1. The analysis results of specific rotation and capillary electrophoresis reveal that the MAH-β-CD-modified Fe3O4 microspheres show stronger complexation of (-)-enantiomers than (+)-enantiomers. In addition, the MAH-β-CD-modified Fe3O4 microspheres have stronger enantioselective absorption for double-ring chiral compounds. These chiral-functionalized magnetic microspheres are therefore expected to be an efficient and economical chiral separation method for use in further research.
- Huang, Jun,Su, Ping,Wu, Jingwei,Yang, Yi
-
p. 58514 - 58521
(2015/02/19)
-
- Characterization of d-amino acid aminotransferase from Lactobacillus salivarius
-
We searched a UniProt database of lactic acid bacteria in an effort to identify d-amino acid metabolizing enzymes other than alanine racemase. We found a d-amino acid aminotransferase (d-AAT) homologous gene (UniProt ID: Q1WRM6) in the genome of Lactobacillus salivarius. The gene was then expressed in Escherichia coli, and its product exhibited transaminase activity between d-alanine and α-ketoglutarate. This is the first characterization of a d-AAT from a lactic acid bacterium. L. salivarius d-AAT is a homodimer that uses pyridoxal-5′-phosphate (PLP) as a cofactor; it contains 0.91 molecules of PLP per subunit. Maximum activity was seen at a temperature of 60 °C and a pH of 6.0. However, the enzyme lost no activity when incubated for 30 min at 30 °C and pH 5.5 to 9.5, and retained half its activity when incubated at pH 4.5 or 11.0 under the same conditions. Double reciprocal plots of the initial velocity and d-alanine concentrations in the presence of several fixed concentrations of α-ketoglutarate gave a series of parallel lines, which is consistent with a Ping-Pong mechanism. The Km values for d-alanine and α-ketoglutarate were 1.05 and 3.78 mM, respectively. With this enzyme, d-allo-isoleucine exhibited greater relative activity than d-alanine as the amino donor, while α-ketobutylate, glyoxylate and indole-3-pyruvate were all more preferable amino acceptors than α-ketoglutarate. The substrate specificity of L. salivarius d-AAT thus differs greatly from those of the other d-AATs so far reported.
- Kobayashi, Jyumpei,Shimizu, Yasuhiro,Mutaguchi, Yuta,Doi, Katsumi,Ohshima, Toshihisa
-
-
- SEPARATING AGENT FOR CHROMATOGRAPHY
-
A separating agent for chromatography is provided that is useful for the separation of specific compounds, e.g., for the optical resolution of amino acids. This separating agent for chromatography provides a higher productivity and contains a crown ether-like cyclic structure and optically active binaphthyl. This separating agent for chromatography containing a crown ether-like cyclic structure and optically active binaphthyl is provided by introducing a substitution group for binding to carrier into a specific commercially available 1,1′-binaphthyl derivative that has substituents at the 2, 2′, 3, and 3′ positions, then introducing a crown ether-like cyclic structure, and subsequently chemically bonding the binaphthyl derivative to the carrier through the substitution group for binding to carrier.
- -
-
Paragraph 0074; 0075
(2013/08/15)
-
- METHOD FOR OBTAINING OPTICALLY PURE AMINO ACIDS
-
This invention relates to a method for obtaining optically pure amino acids, including optical resolution and optical conversion. This method significantly shortens the time taken for optical transformation, and enables the repeated use of an organic solution containing a enantioselective receptor, to thereby obtain optically pure amino acids in a simple and remarkably efficient manner, and to enable the very economical mass production of optically pure amino acids.
- -
-
Page/Page column 7
(2012/02/01)
-
- METHOD FOR OBTAINING OPTICALLY PURE AMINO ACIDS
-
This invention relates to a method for obtaining optically pure amino acids, including optical resolution and optical conversion. This method significantly shortens the time taken for optical transformation, and enables the repeated use of an organic solution containing a enantioselective receptor, to thereby obtain optically pure amino acids in a simple and remarkably efficient manner, and to enable the very economical mass production of optically pure amino acids.
- -
-
Page/Page column 10-11
(2012/02/14)
-
- GADD45BETA TARGETING AGENTS
-
Compounds based around tetrapeptide, tripeptide and dipeptide moeties and corresponding peptiod moeties. Related methods and pharmaceutical compositions for use in treatment of cancer, inflammatory diseases, and other disorders.
- -
-
-
- Enantioseparation of racemic mixtures based on solvent sublation
-
A method of solvent sublation was developed for the enantioseparation of racemic ofloxacin (rac Oflx) and racemic tryptophan (rac Trp). In this method, dibenzoyl-L-tartaric acid (L-DBTA) and di-(2-ethylhexyl) phosphoric acid (D2EHPA) and sodium lauryl sulfate (SDS) were used as chiral coextractants and foamer, respectively. Several important parameters influencing the separation performances, such as pH in aqueous phase, concentrations of rac mixtures, L-DBTA, D2EHPA, and SDS, were investigated. Under the optimal operation conditions, the enantiomeric excess and enantioselectivity were 60.08% and 5.58 for Oflx and 65.09% and 6.31 for Trp, respectively. The yields of D-enantiomer and L-enantiomer were 34.23% and 8.54% for Oflx and 18.59% and 3.93% for Trp, respectively. The results suggest that the enantioselectivities have been enhanced compared with the traditional chiral extraction. This technique is an efficient chiral separation method, with many advantages such as low expenditures of organic solvent, low consumption of chiral extractant, and easy realization of multistage operation. Chirality 24:661-667, 2012. 2012 Wiley Periodicals, Inc. Copyright
- Jiao, Feipeng,Yang, Weijie,Wang, Fen,Tian, Lingxing,Li, Lin,Chen, Xiaoqing,Mu, Kelang
-
experimental part
p. 661 - 667
(2012/10/18)
-
- Aminolytic reaction catalyzed by d-stereospecific amidohydrolases from Streptomyces spp
-
From investigation of 2000 soil isolates, we identified two serine-type amidohydrolases that can hydrolyze d-aminoacyl derivatives from the culture supernatant of Streptomyces species 82F2 and 83D12. The enzymes, redesignated as 82F2-DAP and 83D12-DAP, were purified for homogeneity and characterized. Each enzyme had molecular mass of approximately 40 kDa, and each showed moderate stability with respect to temperature and pH. Among hydrolytic activities toward d-aminoacyl-pNAs, the enzymes showed strict specificity toward d-Phe-pNA, but showed broad specificity toward d-aminoacyl esters. The specific activity for d-Phe-pNA hydrolysis of 82F2-DAP was ten-fold higher than that of 83D12-DAP. As a second function, each enzyme showed peptide bond formation activity by its function of aminolysis reaction. Based on results of d-Phe-d-Phe synthesis under various conditions, we propose a reaction mechanism for d-Phe-d-Phe production. Furthermore, the enzymes exhibited peptide elongation activity, producing oligo homopeptide in a one-pot reaction. We cloned the genes encoding each enzyme, which revealed that the primary structure of each enzyme showed 30-60% identity with those of peptidases belonging to the clan SE, S12 peptidase family categorized as serine peptidase with d-stereospecificity.
- Arima, Jiro,Ito, Hitomi,Hatanaka, Tadashi,Mori, Nobuhiro
-
experimental part
p. 1460 - 1469
(2012/01/12)
-
- The biosynthetic pathway of crucifer phytoalexins and phytoanticipins: De novo incorporation of deuterated tryptophans and quasi-natural compounds
-
Although several biosynthetic intermediates in pathways to cruciferous phytoalexins and phytoanticipins are common, questions regarding the introduction of substituents at N-1 of the indole moiety remain unanswered. Toward this end, we investigated the potential incorporations of several perdeuterated d- and l-1′-methoxytryptophans, d- and l-tryptophans and other indol-3-yl derivatives into pertinent phytoalexins and phytoanticipins (indolyl glucosinolates) produced in rutabaga (Brassica napus L. ssp. rapifera) roots. In addition, we probed the potential transformations of quasi-natural compounds, these being analogues of biosynthetic intermediates that might lead to "quasi-natural" products (products similar to natural products but not produced under natural conditions). No detectable incorporations of deuterium labeled 1′-methoxytryptophans into phytoalexins or glucobrassicin were detected. l-tryptophan was incorporated in a higher percentage than d-tryptophan into both phytoalexins and phytoanticipins. However, in the case of the phytoalexin rapalexin A, both d- and l-tryptophan were incorporated to the same extent. Furthermore, the transformations of both 1′-methylindolyl-3′-acetaldoxime and 1′-methylindolyl-3′-acetothiohydroxamic acid (quasi-natural products) into 1′-methylglucobrassicin but not into phytoalexins suggested that post-aldoxime enzymes in the biosynthetic pathway of indolyl glucosinolates are not substrate-specific. Hence, it would appear that the 1-methoxy substituent of the indole moiety is introduced downstream from tryptophan and that the post-aldoxime enzymes of the glucosinolate pathway are different from the enzymes of the phytoalexin pathway. A higher substrate specificity of some enzymes of the phytoalexin pathway might explain the relatively lower structural diversity among phytoalexins than among glucosinolates.
- Pedras, M. Soledade C.,Okinyo-Owiti, Denis P.,Thoms, Ken,Adio, Adewale M.
-
experimental part
p. 1129 - 1138
(2010/06/21)
-
- Enantioselective scavenging using homogenate of Rhodotorula graminis: a facile preparation of d-amino acid derivatives in enantiopure form
-
An enantioselective scavenger (ES) comprised homogenate of Rhodotorula graminis containing multiple enzymes can enantioselectively remove l-enantiomer in a racemic mixture of amino acid derivatives (AADs), yielding d-enantiomer in high ee. Thirteen non-proteinogenic AADs were produced in enantiopure d form. The method appears to be an efficient cleaning and preparative strategy which can be applied to the production of d-AADs in high ee by enantioselectively scavenging the 'l-contaminants'.
- Zhang, Zizhang
-
body text
p. 6468 - 6470
(2009/04/06)
-
- Capillary electrophoretic separation of enantiomers of amino acids and amino acid derivatives using crown ether and cyclodextrin
-
The capillary zone electrophoresis using (+)-18-crown-6-tetracarbonic acid as a chiral selector was a suitable method for the enantiomeric separation of racemates of amino acids and of some amino acid derivatives (esters, dipeptides). The influence of the chemical structure of the compounds on the separation was investigated. After optimization of the separation conditions, baseline separations were obtained for most racemates. The addition of acetonitrile and TBAB yielded an improvement of the separation. Improved selectivity was further observed by the application of a cyclodextrin, HP-β-CD, in combination with the crown ether.
- Salami,Jira,Otto, Hans-Hartwig
-
p. 181 - 185
(2007/10/03)
-
- Apicidin-derived cyclic tetrapeptides
-
Cyclic tetrapeptide compounds derived from apicidin therapeutically inhibit histone deacetylase activity, are represented by Formula I: and are useful in the treatment of protozoal infections.
- -
-
-
- Analysis of underivatized amino acids and their D/L-enantiomers by sheathless capillary electrophoresis/electrospray ionization-mass spectrometry
-
Capillary electrophoresis/electrospray ionization-mass spectrometry (CE/ESI-MS) was applied to the analysis of underivatized amino acids and the separation of their D/L-enantiomers. Under full-scan mode, all standard protein amino acids were separated and detected at low-femtomole levels using a 130-cm-long, 20-μm-i.d., 150-μm-o.d. underivatized fused-silica capillary with 1 M formic acid as the background electrolyte. The CE/ESI-MS technique was also applied to the separation of L-arginine from L-canavanine (a close analogue of arginine where the terminal methylene linked to the guanidine group of arginine is replaced by an oxygen atom) in a complex mixture containing all standard protein amino acids. The utility of CE/ESI-MS in the analysis of real-world samples was demonstrated by the identification of two metabolic diseases (PKU and tyrosinemia) through blood analysis with minimal sample preparation. In addition, the on-line separation of 11 underivatized L-amino acids from their D-enantiomers was achieved by using a 30 mM solution of (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid as the background electrolyte.
- Schultz, Casey L.,Moini, Mehdi
-
p. 1508 - 1513
(2007/10/03)
-
- Amine-boranes: Effective reducing agents for the deracemisation of DL-amino acids using L-amino acid oxidase from Proteus myxofaciens
-
The deracemisation of DL-α-amino acids using L-amino acid oxidase from Proteus myxofaciens and amine-boranes as chemical reducing agents has been investigated. Amine-boranes were found to be of particular interest in terms of reactivity and chemoselectivity compared to sodium borohydride and cyanoborohydride. Starting from the racemate, a range of D-amino acids were obtained in yields of up to 90% and e.e. >99%.
- Alexandre, Fran?ois-René,Pantaleone, David P.,Taylor, Paul P.,Fotheringham, Ian G.,Ager, David J.,Turner, Nicholas J.
-
p. 707 - 710
(2007/10/03)
-
- Mapping the substrate selectivity of new hydrolases using colorimetric screening: Lipases from Bacillus thermocatenulatus and Ophiostoma piliferum, esterases from Pseudomonas fluorescens and Streptomyces diastatochromogenes
-
Recent advances in biochemistry and molecular biology have simplified the discovery and preparation of new hydrolases. Although these hydrolases might solve problems in organic synthesis, measuring their selectivity, especially enantioselectivity, remains tedious and time consuming. Recently, we developed a colorimetric screening method to measure the enantioselectivity of hydrolases. Here we apply this rapid screening method to map the substrate selectivity of four new hydrolases: lipases from the thermophilic Bacillus thermocatenulatus (DSM 730, BTL2) and a filamentous fungus Ophiostoma piliferum (NRRL 18917, OPL) and esterases from two bacteria, Pseudomonas fluorescens (SIK-W1, esterase I, PFE) and Streptomyces diastatochromogenes (Tue 20, SDE). We screened a general library of 29 substrates and a chiral library of 23 pairs of enantiomers. All four hydrolases catalysed the hydrolysis of unnatural substrates, but the two lipases accepted a broader range of substrates than the two esterases. As expected, the two lipases favoured more hydrophobic substrates, while the two esterases showed a preference for smaller substrates. Several moderately enantioselective reactions were identified for the solketal esters: BTL2, butyrate, E = 7.9 (R); octanoate, E = 4.9 (R) and 3-bromo-2-methyl propionate methyl esters, PFE, E = 12 (S); SDE, E = 5.6 (S). OPL showed low enantioselectivity toward all substrates tested. The current colorimetric screen could not measure the selectivity for several slow-reacting substrates. Traditional screening identified high enantioselectivity of BTL2 and PFE toward one of these slow substrates, 1-phenylethyl acetate (E>50).
- Liu, Andrew Man Fai,Somers, Neil A.,Kazlauskas, Romas J.,Brush, Terry S.,Zocher, Frank,Enzelberger, Markus M.,Bornscheuer, Uwe T.,Horsman, Geoff P.,Mezzetti, Alessandra,Schmidt-Dannert, Claudia,Schmid, Rolf D.
-
p. 545 - 556
(2007/10/03)
-
- Permucous preparation
-
A composition for permucosal administration characterized by containing Antago-3 or a physiologically acceptable salt thereof, and a sucrose fatty acid ester. With the composition for permucosal administration of the invention there is provided a long-term stable preparation having the high permucosal absorption of physiologically active peptide Antago-3 without irritation.
- -
-
-
- Retention and selectivity of teicoplanin stationary phases after copper complexation and isotopic exchange
-
Teicoplanin is a macrocyclic glycopeptide that is highly effective as a chiral selector for LC enantiomeric separations. Two possible interaction paths were investigated and related to solute retention and selectivity: (1) interactions with the only teicoplanin amine group and (2) role of hydrogen bonding interactions. Mobile phases containing 0.5 and 5 mM copper ions were used to try to block the amine group. In the presence of copper ions, it was found that the teicoplanin stationary phase has a decreased ability to separate most underivatized racemic amino acids. However, it maintained its ability to separate enantiomers that were not α - amino acids. It is established that there is little copper - teicoplanin complex formation. The effect of Cu2+ on the enantioseparation of some α - amino acids appears to be due to the fact that these solutes are good bidentate ligands and form complexes with copper ions in the mobile phase. Isotopic exchange with deuterium oxide was performed using acetonitrile - heavy water mobile phases. It was found that the retention times of all amino acids were lower with deuterated mobile phases. The retention times of polar or apolar molecules without amine groups were higher with deuterated mobiles phases. In all cases, the enantio-selectivity factors were unaffected by the deuterium exchange. It is proposed that the electrostatic interactions are decreased in the deuterated mobile phases and the solute-accessible stationary-phase volume is somewhat swollen by deuterium oxide. The balance of these effects is a decrease in the amino acid retention times and an increase in the apolar solute retention time. The enantio-selectivity factors of all of the molecules remain unchanged because all of the interactions are changed equally. We propose a new global quality criterion (the E factor) for comparing and evaluating enantiomeric separations.
- Berthod,Valleix,Tizon,Leonce,Caussignac,Armstrong
-
p. 5499 - 5508
(2007/10/03)
-
