- Coupling-Reagent-Free Synthesis of Dipeptides and Tripeptides Using Amino Acid Ionic Liquids
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A general method for the synthesis of dipeptides has been developed, which does not require any coupling reagents. This method is based on the reaction of readily available HCl salts of amino acid methyl esters with tetrabutylphosphonium amino acid ionic liquids. The isolation procedure of stepwise treatment with AcOH is easy to carry out. The method was extended to the synthesis of tripeptide, tyrosyl-glycyl-glycine, present in IMREG-1, also.
- Furukawa, Shinya,Fukuyama, Takahide,Matsui, Akihiro,Kuratsu, Mai,Nakaya, Ryotaro,Ineyama, Takashi,Ueda, Hiroshi,Ryu, Ilhyong
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supporting information
p. 11980 - 11983
(2015/08/18)
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- Synthesis of an enkephalin analogue containing an α,α- disubstituted heterocyclic aminophosphonic acid
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Synthesis of a phosphonopentapeptide enkephalin analogue was achieved from heterocyclic aminophosphonates via the coupling of Boc-Tyr-Gly-Gly-OH with phosphonodipeptide. The latter was formed by coupling Boc-Phe-OH with N-terminal α,α-disubstituted hetero
- Rabasso, Nicolas,Fadel, Antoine
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experimental part
p. 1811 - 1819
(2011/10/08)
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- Thioamides: Synthesis, stability, and immunological activities of thioanalogues of imreg. Preparation of new thioacylating agents using fluorobenzimidazolone derivatives
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Imreg (Tyr1-Gly2-Gly3) is a well-known immunostimulant. However, it possesses a short half-life. Stabilized analogues of Imreg were prepared by a regioselective insertion in which peptide bonds at position 1,2 or 2,3 were
- Zacharie, Boulos,Lagraoui, Mouna,Dimarco, Marika,Penney, Christopher L.,Gagnon, Lyne
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p. 2046 - 2052
(2007/10/03)
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- Effects of three peptidase inhibitors, amastatin, captopril and phosphoramidon, on the hydrolysis of [Met5]-enkephalin-Arg6-Phe7 and other opioid peptides
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The contents of [Met5]-enkephalin-Arg6-Phe7 (met-enk-RF) and its six hydrolysis products: Y, YG, YGG, YGGF, YGGFM, and YGGFMR were estimated after incubating met-enk-RF with either a guinea-pig ileal or striatal membrane fraction for various times at 37°C. After 45 min incubation with either ileal or striatal membranes, met-enk-RF was completely hydrolyzed, yielding Y as the major product. Incubation with either membrane preparation for 60 min in the presence of the aminopeptidase inhibitor amastatin hydrolyzed 90 or 92% of met-enk-RF, respectively, with YGG being the major product. If the dipeptidyl carboxypeptidase I inhibitor captopril is also included in the incubation, met-enk-RF hydrolysis decreases by about half for both membranes, with YGG remaining the major product. Inclusion of three peptidase inhibitors, amastatin, captopril, and phosphoramidon (inhibition of endopeptidase-24.11) further reduced met-enkhydrolysis, with 87% or more remaining intact. This shows that met-enk-RF was mainly hydrolyzed by three enzymes, amastatin-sensitive aminopeptidase, captopril-sensitive dipeptidyl carboxypeptidase I and phosphoramidon-sensitive endopeptidase-24.11, in both ileal and striatal membranes. Additionally, estimations of [Leu5]-enkephalin (leu-enk), α- and β-neoendorphins (α- and β-neoends), and dynorphin B (dyn B) contents after incubating the individual peptides with striatal membrane for 60 min in the presence of the three peptidase inhibitors showed that 98, 32, 5, and 23%, respectively, remained intact. Our previous studies together with the data obtained here show that one group of endogenous opioid peptides: met-enk, leu-enk, met-enk-RF, met-enk-RGL, and dyn A-(1-8) are largely or almost exclusively hydrolyzed by the three enzymes, amastatin-sensitive aminopeptidase, captopril-sensitive dipeptidyl carboxypeptidase I, and phosphoramidon-sensitive endopeptidase-24.11, and indicate that an unidentified fourth enzyme(s) is involved in the hydrolysis of another group of peptides: α-neoend, β-neoend, and dyn B.
- Hiranuma, Toyokazu,Kitamura, Ken,Taniguchi, Takao,Kobayashi, Tomomi,Tamaki, Raita,Kanai, Masayuki,Akahori, Kazuhito,Iwao, Kayoko,Oka, Tetsuo
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p. 276 - 282
(2007/10/03)
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- Transmucosal delivery of methionine enkephalin. I: Solution stability and kinetics of degradation in various rabbit mucosa extracts
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To evaluate the feasibility of transmucosal delivery of methionine enkephalin (Tyr-Gly-Gly-Phe-Met; Met-Enk), it is important to first investigate its physicochemical and enzymatic stability. The kinetics of degradation of Met-Enk in aqueous solution was determined at pH 2.01-9.84 and 37-45 °C by high-performance liquid chromatography. The first-order rate constant (k) was calculated, and the log k-pH profile showed that Met-Enk is most stable at pH ~5.0. Various mucosae excised from rabbit were mounted on Valia-Chien permeation cells and exposed to isotonic phosphate buffer at physiologic pHs. Mucosal and serosal extracts were collected from the donor and receptor solutions, respectively. The degradation of Met-Enk in the extracts followed first-order kinetics, but no significant difference in the degradation rates was observed between mucosal and serosal extracts, regardless of the type of mucosa used. Degradation was most rapid in the extracts of rectal mucosa, followed by vaginal and nasal mucosae. The major metabolites were Des-Tyr-Met-Enk and Tyrosine (Tyr), indicating the enzymatic hydrolysis by aminopeptidases. However, the data also suggested that dipeptidyl peptidase and dipeptidyl carboxypeptidase could play some roles in the degradation of Met-Enk. The degradation pathways of Met-Enk were further explored by concomitantly determining the formation of smaller metabolites of primary hydrolytic fragments of Met-Enk in the mucosal extracts.
- In Koo Chun,Chien
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p. 373 - 378
(2007/10/02)
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- Transmucosal delivery of leucine enkephalin: Stabilization in rabbit enzyme extracts and enhancement of permeation through mucosae
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Leucine enkephalin (Tyr-Gly-Gly-Phe-Leu; Leu-Enk) is a naturally occurring peptide that has been shown to have pain modulating properties. To evaluate the feasibility of using various absorptive mucosae as a route of systemic delivery, the stability of Leu-Enk and the effect of enzyme inhibitors (e.g., amastatin, EDTA, and thimerosal) on stabilization and permeation of Leu-Enk through rabbit mucosae in the presence of dihydrofusidates were investigated. Enzymes in the nasal, rectal, and vaginal mucosae were extracted and Leu-Enk (50 μg/mL) was added to each of the enzyme extracts and incubated to determine the kinetics and mechanism of degradation. The rate of degradation in the extracts in the absence of inhibitors followed the order: rectal > vaginal > nasal. Whereas EDTA had the best stabilizing effect on Leu-Enk, thimerosal was the best stabilizer for the degradation intermediates. A combination of amastatin (50 μM), EDTA (5 mM), and thimerosal (50 μM) had the greatest stabilizing effect on Leu-Enk and its degradation intermediates. For permeation studies, each mucosa was mounted onto a Valia-Chien permeation cell with Leu-Enk (200 μg/mL) in isotonic phosphate buffer (as donor solution). The enhancers used for the study were sodium tauro-dihydrofusidate (STDHF), sodium glycodihydrofusidate (SGDHF), and phosphato-dihydrofusidate (PHDHF). The greatest effect was achieved by PHDHF for all the mucosae. STDHF had a significant effect only on the rectal permeation, whereas SGDHF had significant effects on rectal and vaginal mucosae. Mechanisms by which the dihydrofusidates enhance permeation may involve micelle formation. Thus, the use of enzyme inhibitors and dihydrofusidates in combination has made transmucosal delivery of Leu-Enk a viable option.
- Sayani,Chun,Chien
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p. 1179 - 1185
(2007/10/02)
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- Real-Time Reaction Monitoring by Continuous-Introduction Ion-Spray Tandem Mass Spectrometry
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A temperature-controlled reaction vessel was closely coupled to the ion-spray LC/MS interface on an atmospheric pressure ionization, triple quadrupole mass spectrometer and used to study mechanistic and kinetic aspects of reactions taking place in solution.Free access to the reaction vessel and temperature control as well as minimal sample consumption make continuous-introduction ion-spray mass spectrometry a useful approach for real-time measurement of reactions.The reaction medium, reactants, and products were transferred to the ion source of the mass spectrometer from the reaction vessel in less than 1 s.A variety of model reactions have been investigated to demonstrate the feasibility and potential for continuous-introduction ion-spray mass spectrometry for real-time reaction monitoring.The half-life for the solvolysis of methandrostenolone sulfate in aqueous medium and the Michaelis-Menten constant of the enzymatic hydrolysis of O-nitrophenyl β-D-galactopyranoside by lactase were determined.The enzymatic hydrolysis of dynorphin 1-8 by α-chymotrypsin and leucine aminopeptidase and the reduction of the disulfide bridge in oxytocin with β-mercaptoethanol were obtained on-line to emphasize the technique's capability for peptide sequencing and structural elucidation.
- Lee, Edgar D.,Mueck, Wolfgang,Henion, Jack D.,Covey, Thomas R.
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p. 4600 - 4604
(2007/10/02)
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