摘要:

AbstractThe conformational preferences of peptide T (ASTTTNYT) were analysed by means of computational methods. A thorough exploration of the conformational space was carried out within the framework of the molecular mechanics approach, using simulated annealing as a searching strategy. Specifically, in order to obtain a subset of low‐energy conformations with energies close to the global minimum as complete as possible, a simulated annealing protocol was repeated several times in a recursive fashion. The results of the search indicate that the peptide exhibits a α‐helical character although most of the conformations characterized, including the global minimum, can be described as bent conformations. Conformations exhibiting β‐turn motives previously proposed from NMR studies were also characterized, although they are not very predominant in the set of low‐energy conformations. © 1997 European Peptide Society and John Wiley

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199703)3:2<85::AID-PSC84>3.0.CO;2-0

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractThe ability of the endopeptidase α‐chymotrypsin (EC 3.4.21.1) to catalyse the reaction of various Nα‐ unprotected di‐ and tripeptide ester derivatives with H‐Leu‐NH2, and with a series of C‐terminal free di‐ and tripeptides at −15° C in frozen aqueous solution was investigated. The enzyme is able to synthesize N‐ and C‐terminal unprotected penta‐ and hexapeptides in up to 92% yield, depending on the amino component used, in a single‐step segment‐condensation reaction. Freezing the reaction mixture resulted in significantly increased peptide yields compared with the reaction at room temperature. The enzyme shows a modified nucleophilic specificity in frozen solution compared with room temperature. Nucleophilic amino components with positively charged amino acids in P2′‐position are accepted. © 1997 European Peptide

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199703)3:2<93::AID-PSC87>3.0.CO;2-R

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractThe preparation of a β‐galactosylated hydroxyproline derivative and its use in the multi‐gram solid‐phase synthesis of the potent analgesic neoglycopeptideO1.5‐β‐D‐galactopyranosyl[D‐Met2, Hyp5]enkephalinamide is described in this paper. The most closely related impurities have been identified, isolated and characterized. Significant aspects of the synthesis and purification affecting yields and purity of both the building block and the target neoglycopeptide are discussed. © 1997 European Peptide Society and John

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199703)3:2<99::AID-PSC89>3.0.CO;2-F

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractA series of N‐ and C‐protected, monodispersed homo‐oligopeptides (to the dodecamer level) from the small‐ring alicyclic Cα,α‐dialkylated glycine 1‐aminocyclobutane‐1‐carboxylic acid (Ac4c) and two Ala/Ac4c tripeptides were synthesized by solution methods and fully characterized. The conformational preferences of all the model peptides were determined in deuterochloroform solution by FT‐IR absorption and1H‐NMR. The molecular structures of the amino acid derivatives Z‐Ac4c‐OH and Z2‐Ac4c‐OH, the tripeptides Z‐(Ac4c)3‐OtBu, Z‐Ac4c‐(L‐Ala)2‐OMe and Z‐L‐Ala‐Ac4c‐L‐Ala‐OMe, and the tetrapeptide Z‐(Ac4c)4‐OtBu were determined in the crystal state by X‐ray diffraction. The average geometry of the cyclobutyl moiety of the Ac4c residue was assessed and the τ(N–Cα–C′) bond angle was found to be significantly expanded from the regular tetrahedral value. The conformational data are strongly in favour of the conclusion that the Ac4c residue is an effective β‐turn and helix former. A comparison with the structural propensities of α‐aminoisobutyric acid, the prototype of Cα,α‐dialkylated glycines, and the other extensively investigated members of the family of 1‐aminocycloalkane‐1‐carboxylic acids (Acnc, withn=3, 5–8) is made and the implications for the use of the Ac4c residue in conformationally constrained peptide an

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199703)3:2<110::AID-PSC88>3.0.CO;2-6

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractIn an effort to increase the probability of finding novel peptides in resin‐bound combinatorial libraries displaying affinity to various macromolecular targets, we increased the diversity of a solid‐phase library considerably by synthesizing multiple structures on each bead – a motif‐library – including 45 building blocks. The building blocks consist ofL‐aa,D‐aa and eight hydrophobic non‐proteinogenic α‐amino acids. A library with the format O‐Z0–1‐O‐Z0–1‐O‐XX‐resin was synthesized giving the four motifs OOOXX, OZOOXX, OOZOXX, OZOZOXX corresponding to 364.500 different motifs (453×4 theoretical combinations). The positions O are defined amino acids while Z represents three mixtures Π, Ω, ϖ, where Π is a mixture of polar and charged residues, Ω is a mixture of aliphatic residues and ϖ is a mixture of aromatic residues. X represents a mixture of all 45 residues. The library was screened with the macromolecular target streptavidin which served as a model receptor. Binding peptides were sequenced by microsequencing. We included small amounts of norvaline and norleucine in the library, which served as index residues to be able to distinguish betweenLD‐amino acids and other residues with the same retention time in the HPLC system. Beads that interact with the receptor were found, and the binding motifs that appeared had no homology to known binding motifs found in eitherL‐aa orD‐aa libraries, instead motifs with the non‐proteinogenic residuesL‐phenylglycine,O‐benzyl‐L‐hydroxyproline andO‐benzyl‐L‐tyrosine dominated. The novel peptides inhibit binding of biotin to streptavidin but do not bind to avidin, and the affinity is higher than the peptides found in linear allL‐aa peptide l

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199703)3:2<123::AID-PSC92>3.0.CO;2-H

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractVia the refinement process of the monomer form of an arginine–vasopressin‐like insect factor, the paper analyses the most relevant NMR information to define the solution structure of a flexible peptide. The relative importance of the different NOE constraints is discussed. © 1997 European Peptide Society and John Wiley&Sons,

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199703)3:2<133::AID-PSC91>3.0.CO;2-H

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractA competitive reaction of activated Boc‐Ala‐OH and Boc‐Phe‐OH with H‐Leu‐resin has been developed for assessing the relative efficiencies of different carbodiimides. This allowed a comparison of the efficiency of the carbodiimidesN,N;′‐dicyclohexylcarbodiimide,N,N′‐diisopropylcarbodiimide,N‐tert‐butyl‐N′‐methylcarbodiimide andN‐tert‐butyl‐N′‐ethylcarbodiimide. Comparable results were obtained when these reagents were used for the preformation of symmetrical anhydrides or of 1‐hydroxybenzotriazole estersin situ. Differential incorporation was observed when asymmetrical carbodiimides were used for peptide bond formation by the direct carbodiimide procedure. © 1997 Europea

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199703)3:2<141::AID-PSC93>3.0.CO;2-A

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractThe biosynthesis of bacterial isoleucyl‐rich surfactins was controlled by supplementation ofL‐isoleucine to the culture medium. Two new variants, the [Ile4,7]‐ and [Ile2,4,7]surfactins, were thus produced byBacillus subtilisand their separation was achieved by reverse‐phase HPLC. Amino acids of the heptapeptide moiety were analysed by chemical methods, and the lipid moiety was identified to β‐hydroxyanteisopentadecanoic acid by combined GC/MS. Sequences were established on the basis of two‐dimensional NMR data. Because conformational parameters issuing from NMR spectra suggested that the cyclic backbone fold was globally conserved in the new variants, structure–activity relationships were discussed in details on the basis of the three‐dimensional model of surfactin in solution. Indeed, both variants have increased surface properties compared with that of surfactin, and this improvement is assigned to an increase of the hydrophobicity of the apolar domain favouring micellization. Furthermore, the additional Leu‐to‐Ile substitution at position 2 in the [Ile2,4,7]surfactin leads to a substantial increase of its affinity for calcium, when compared with that of [Ile4,7]surfactin or surfactin. This effect is assigned, from the model, to an increase in the accessibility of the acidic side chains constituting the calcium binding site. Thus, the propensities of such active lipopeptides for both hydrophobic and electrostatic interactions were improved, further substantiating that they can be rationally designed. © 1997 European Peptide Society an

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199703)3:2<145::AID-PSC96>3.0.CO;2-Y

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY