摘要:

AbstractWhen using proteases in direct reversal of their normal hydrolytic function, the equilibrium position is very important in limiting the attainable yield in equilibrium‐controlled enzymic peptide synthesis. Analysis of the equilibrium position reveals a favourable shift towards the peptide product if starting materials are largely undissolved in the reaction medium and the product precipitates. This approach enabled us to obtain high peptide yields in thermolysin‐catalysed reactions in high‐density aqueous media with an equimolar supply of substrates. The easy scale‐up (up to mol‐scale) of this approach is demonstrated by two examples. Z‐His‐Phe‐ NH2and Z‐Asp‐Phe‐OMe, precursors for cyclo‐[‐His‐Phe‐] and the low‐calorie sweetener Aspartame, respectively, were synthesized in preparative yields of 84–88%. © 1997 European Peptid

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199707)3:4<245::AID-PSC98>3.0.CO;2-L

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractChaperonin 10 protein fromRattus norvegicus(Rat cpn10) has been reported to bind chaperonin 60 fromEscherichia coli(GroEL) in an ATP‐dependent manner. Chemically synthesized Rat cpn10 was immobilized in a defined orientation to agarose‐bound monomeric avidin using a reversible biotinylated affinity label (1), attached to the Nα‐terminal residue. The resulting affinity chromatographic matrix was then used to isolate binding proteins from a crude cell lysate. Following affinity separation the bound ligand and ligate was released by treatment with organic base. Rat cpn10 was prepared using a highly effective synthetic protocol involving HBTU/HOBt activation and capping withN‐(2‐chlorobenzyloxycarbonyloxy) succinimide to terminate unreacted amino groups. The biotinylated Fmoc‐based molecule (1) was introduced specifically onto the Nα‐terminal amino acid as the succinimidyl carbonate, before final cleavage and deprotection of side‐chain protecting groups using a low‐TFMSA/high‐HF procedure. Crude biotinylated Rat cpn10 (Rat cpn10+1) was immobilized on monomeric avidin with a binding efficiency of approximately 75% and unlabelled truncated/capped impurities eluted off the column with buffer. The biotinylated Rat cpn10–avidin affinity matrix was then used to isolate GroEL from a crude cell lysate. The identity of the purified protein was confirmed by SDS–PAGE and binding to a specific anti‐GroEL monoclonal antibody (MoAb). These results extend the applicability of the biotinylated label (1), providing a reversible non‐covalent anchor for immobilization of peptide and protein ligands, thus simplifying isolation of ligates and enabling recovery of synthetic material under mild conditions. © 1997 European Peptide So

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199707)3:4<252::AID-PSC100>3.0.CO;2-4

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractRecently we have demonstrated the advantage of solid‐ phase substrate pools mainly in equilibrium controlled protease‐catalysed peptide syntheses. The extension of this approach to protease‐catalysed acyl transfer reactions will be presented. The model reaction was systematically investigated according to both the influence of solid phases present in the system on enzyme activity as well as nucleophile concentration on peptide yield. The key parameter for obtaining high peptide yield via acyl transfer is the ratio between aminolysis and hydrolysis. We combined high nucleophile concentrations with solid‐phase acyl donor pools. This approach enabled us to supply ester substrate and nucleophile in equimolar amounts in a high‐density media without the addition of any organic solvent. Several multi‐functional di‐ to tetrapeptides were obtained in moderate to high yields. ©1997 European Peptide Society and John W

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199707)3:4<261::AID-PSC103>3.0.CO;2-Y

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractBased on immunogenicity studies, two T‐cell epitopes in melittin were found to be functional in guinea pigs, one being centrally located, the other one residing in the C‐terminal chain. In Balb/c mice only the central epitope was found to be active. A human T‐cell clone was found by T‐cell proliferation studies to employ strictly the C‐terminal chain. Truncation of melittin peptides at the N‐terminus did not markedly affect the capacity of guinea pigs to develop anti‐IgG responses towards peptidic epitopes and towards a C‐terminally attached haptenic group. Attachment of various substituents inside and outside the T‐cell epitopic areas had no marked effect on antibody responses. In contrast, the substituents positioned within a T‐cell epitope abolished T‐cell proliferation. This difference between whole animal data and cellularin vitroresponses is presently not understood. © 1997 European Peptide Society an

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199707)3:4<267::AID-PSC106>3.0.CO;2-7

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractA novel type of cyclic opiod peptide analogue, cyclo(Nϵ,Nϵ′‐carbonyl‐D‐Lys2,Lys5)enkephalinamide, was prepared from a linear precursor peptide. The peptide was synthesized on the Merrifield resin and also by a combination of the solid‐phase technique and the classical method in solution. In both cases the cyclization was performed by reaction of bis(4‐nitrophenyl)carbonate with the free side‐chain amino groups of the two lysine residues. The described method permits the convenient preparation of novel peptide analogues cyclized via a ureido group incorporating the side‐chain amino groups of two α,ω‐diamino acid residues. The cyclic enkephalin analogue containing a 21‐membered ring structure showed preference for μ over δ opioid receptors in opioid bioassaysin vitro. © 1997 European Peptide Societ

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199707)3:4<277::AID-PSC107>3.0.CO;2-3

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractThe study of the phylogenetic distribution of the β‐thymosin family is important to elucidate its biological function further. A new thymosin, designated as thymosin β14, consisting of 40 amino acid residues and with a molecular weight of 4537 Da as determined by ion spray mass spectrometry, was isolated from the sea urchin. The N‐terminus of this polypeptide is blocked by an acetyl group as found by matrix‐assisted laser desorption mass spectrometric and amino acid analysis. The primary structure was elucidatd by Edman degradation of the HPLC‐purified thymosin β14fragments produced by digestion with endoproteinase Asp‐N and trypsin. Sequence comparison reveals that thymosin β14is 73% homologous to thymosin β4, obtained from calf thymus. By isolating and characterising the structure of thymosin β14from the sea urchin, an invertebrate, substantial knowledge about the phylogenetic distribution and evolution of β‐thymosins is gained. © 1997 European Peptide Society and

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199707)3:4<282::AID-PSC119>3.0.CO;2-A

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractLipid mimetics, synthetic molecules that resemble natural lipids either structurally or functionally, have been developed as potential medicinal substances. They have been successfully applied in the development of drug and peptide delivery systems and for the development of inhibitors or lipid metabolizing enzymes. Phospholipase A2 is considered to be involved as the rate‒limiting step in the production of lipid mediators of inflammatory responses and, as such, it has been a target for drug design. A series of lipid mimetics including lipopeptides, amides and alcohols of lipidic α‒amino acids, have been tested by bulk and monolayer assay techniques. The findings suggested the direct interaction of the tested compounds with porcine pancreatic phospholipase A2. The inactivation of the enzyme occurred in a competitive manner. The most active compound 1 (2‐amino‐N‐hexadecyl‐L‐hexanamide) showed an apparent IC50of 12 μMand inhibitory powerZ=13 in the monolayer assay. © 1997 European Peptide Society and John

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199707)3:4<291::AID-PSC120>3.0.CO;2-1

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractA peptide fragment corresponding to the third helix ofStaphylococcus Aureusprotein A, domain B, was chosen to study the effect of the main‒chain direction upon secondary structure formation and stability, applying the retro‒enantio concept. For this purpose, two peptides consisting of the native (Ln) and reversed (Lr) sequences were synthesized and their conformational preferences analysed by CD and NMR spectroscopy. A combination of CD and NMR data, such as molar ellipcitity, NOE connectivities, Hα and NH chemical shifts,3JαNcoupling constants and amide temperature coefficients indicated the presence of nascent helices for both Ln and Lr in water, stabilized upon addition of the fluorinated solvents TFE and HFIP. Helix formation and stabilization appeared to be very similar in both normal and retro peptides, despite the unfavourable charge–macrodipole interactions and bad N‐capping in the retro peptide. Thus, these helix stabilization factors are not a secondary structure as determined for this specific peptide. In general, the synthesis and confirmational analysis of peptide pairs with opposite main‒chain directions, normal and retro peptides, could be useful in the determination of secondary structure stabilization factors dependent on the direction. © 1997 European Peptide Society and John Wil

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199707)3:4<299::AID-PSC121>3.0.CO;2-B

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractKaliotoxin (KTX) is a natural peptide blocker of voltage‐dependent K+channels. The 3D structure of a truncated analogue of KTX (Fernándezet al.(1994)Biochemistry 33, 14256–14263) was determined by NMR spectroscopy and showed significant differences from structures established for other related scorpion toxins. A recent publication with the structure of the complete toxin (Aiyaret al.(1995)Neuron 15, 1169–1181) did not confirm these differences. In this communication we report NMR data for KTX at pH 3.0, 5.5 and 7.2 and the 3D structure obtained from data at pH=5.5. Complete KTX displays a folding similar to that of other toxins with an α‐helix and a β‐sheet linked by two disulphide bonds. The pKaof His 34 is anomalously low (4.7–5.2 depending on the buffer) owing to its interaction with two Lys residues (including the essential Lys 27), the charged N‐terminus and the side chain of Met 29. Charged residues are placed symmetrically with respect to an axis that approximately coincides with one of the principal components of the moment of inertia of the toxin. His 34, which occupies a well‐defined position between two conserved Cys, is located on the centre of a layer of charged groups. Positively and negatively charged residues are found at the same position in related toxins. It is suggested that electrostatic effects modulate the distances between positive charges in flexible side chains, contributing to the fine tuning of the selectivity toward different channel subclasses and that the approximate coincidence between the moment of inertia and the charge axis facilitate the approach of the toxin to the channel. The very low pKaof His 34 implies that it will be completely unprotonated at physiological pH. © 1997 European Peptide Society and J

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199707)3:4<314::AID-PSC117>3.0.CO;2-E

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY