摘要:

The disulfide bond in S‐3‐nitro‐2‐pyridinesulfenyl (S‐Npys) compounds is stable towards the acid treatment used in solid‐phase peptide synthesis, yet the lability of S‐Npys‐peptides towards nucleophiles enables the conjugation to proteins to proceed under mild conditions. Thus Boc‐Cys(Npys)‐OH was coupled asN‐terminal residue to a resin‐linked peptide chain. After deprotection and cleavage from the resin the Npys‐cysteinylpeptide was attached to a properly functionalized protein by reaction with a mercapto group. The amount of peptide conjugated to the protein was determined by measuring the amount of 3‐nitro‐2‐thiopyridone liberated. The cysteinylpeptide which was detached from the protein by reduction of the disulfide bond was shown to be identical with the product obtained by reducti

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00930.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The solution conformation of alamethicin, a 20‐residue antibiotic peptide, has been investigated using two‐dimensional n.m.r. spectroscopy. Complete proton resonance assignments of this peptide have been carried out using COSY, SUPERCOSY, RELAY COSY and NOESY two‐dimensional spectroscopies. Observation of a large number of nuclear Overhauser effects between sequential backbone amide protons, between backbone amide protons and CβH protons of preceding residues and extensive intramolecular hydrogen bonding patterns of NH protons has established that this polypeptide is in a largely helical conformation. This result is in conformity with earlier reported solid state X‐ray results and a recent n.m.r. study in methanol solution (Espositoet al.(1987)Biochemistry26, 1043‐1050) but is at variance with an earlier study which favored an extended conformation for theC‐terminal half of alamethicin (Bannerjeeet al.(1983)J. Mol. Biol.1

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00931.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The crystal structures of two tripeptides related to the sequence coding forN‐glycosylation of peptides have been solved: Boc‐Asn(Me)‐Ala‐Ser‐OMe,1, and Boc‐Asn(Me)‐Pro‐Ser‐NHMe,2.Both molecules contain an “Asx‐turn” characterized by a hydrogen bond between the Ser‐NH and Asn‐CγOγ sites. Moreover, the Pro‐Ser sequence is βI‐folded in2.The Ser hydroxyl group is also intramolecularly hydrogen‐bonded in both molecules, but two different hydrogen bondings are observed. In1, the Ser‐Oγ H bond interacts with the Asn‐CγOγ carbonyl, in good agreement with one of the mechanisms which have been proposed for theN‐glycosylation of peptides. In2, the Ser‐OγH bond turns out to be involved in an intra‐residue interaction with Ser‐C'O, and this conformational change is essentially the con

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00932.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Cyclic hexapeptide analogues representing the modified retro sequence of the amino acid residues 7‐11 of natural somatostatin are known to protect liver cells from phalloidin poisoning. To determine the influence of steric, lipophilic, and charge effects on (a) the conformation of the backbone and the aromatic side chains and (b) the biological response, the side chains of Phe2, Lys4, and Phe6of cyclo(‐d‐Pro1‐Phe2‐Thr3‐Lys(Z)4‐Trp5‐Phe6‐), 1a, one of the most active peptides found so far, were modified by various residues. The discussion of conformationally relevant parameters proves that neither backbone conformations nor populations of aromatic side chain rotamers were altered by these substitutions. The potency of these derivatives in a cytoprotection assay varies by at most one order of magnitude (more or less active than the parent peptide 1a). A qualitative evaluation of lipophilic, steric, and charge effects reveals the dominance of lipophilic effects of aromatic residues; the most potent compounds contain aromatic substructures in the s

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00933.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Ortho‐nitrophenyl esters of blocked amino acids have significantly higher aminolysis rates than the correspondingpara‐nitrophenyl esters. This difference prompted a series of investigations that led to the present study. Single crystal X‐ray diffraction analysis oftert.‐butyloxycarbonyl‐l‐alanineo‐nitrophenyl ester has shown a rather rigid molecular conformation with very restricted rotation about the ester bond owing to the wedging of one of the nitro oxygen atoms between the two oxygens of the ester group. Aparanitro group can not interact in a similar fashion and consequently can have many more rotamers. The C14H18N2O6ester crystallizes in space group P21, with a = 5.180 Å, b = 9.726 Å, c = 15.616 Å and β= 92.36 Å. There is only one intermolecular hydrogen bond, N(1)H…O(0) at 3.125 Å, that links neighboring molecules into infinite chains. There are no intramol

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00934.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The solubility prediction method for protected peptides was successfully applied to relatively small peptide fragments of human hemoglobin α‐chain (123‐136) which contained various polar amino acid residues such as Asp(OBzl), Glu(OBzl), Lys(Z), Ser(Bzl), and Thr(Bzl). As reported previously for hydrophobic peptides and human proinsulin C‐peptide fragments, solubility data indicated that the insolubility of protected peptides having avalue below 0.90 appeared to begin at the octa‐ or nonapeptide sequence level and that β‐sheet structure played an important role in the insolubility of peptides. When a peptide has a β‐sheet structure in the solid state, we can clearly determine the critical chain length for peptide insolubility, the solubility dependence on solvent properties, and the solubility independence of amino acid compositio

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00935.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

In order to obtain inhibitors of themeso‐diaminopimelate‐adding enzyme, which participates in the biosynthesis of bacterial peptidoglycan, severalNα‐propionyl‐dipeptides of the general formula Pr‐l‐Ala‐ambo‐Xaa‐OH were synthesized. Xaa represented methionineS,S‐dioxide, methionineS‐oxide, methionine sulfoximine, and 2‐amino‐4‐phosphonobutyric acid, i.e. transition state analogs of glutamine synthetase and γ‐glutamyl‐cysteine synthetase, which catalyze the same type of reaction as our target enzyme. After synthesis, the diastereoisomers were separated by preparative HPLC or t.l.c.; those containing methionine derivatives could be identified thanks to previously synthesized reference compounds. After preincubation with themeso‐diaminopimelate‐adding activity fromEscherichia coli.thelddiastereoisomers displayed moderate inhibitory effects, whereas thellones were inefficient. The best inhibition was obtained with one diastereoisomer of Pr‐l‐Ala‐ζ‐2‐amino‐4‐phosphonobutyrate, presumably theldone. A chloromethylketone derivative Pr‐l‐Ala‐d‐Glu(CH2Cl)‐OH, potential affinity labeler of themeso‐diaminopimelate‐adding enzyme, was also synthesized. In the ass

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00936.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The secondary structure of 11 mammalian growth hormones has been predicted by combining five different methods. Three long helical regions located around residues 20, 120, and 170 constitute the most prominent common feature in the species studied. The strong amphiphilic character of these helices suggests that they can play an important role in protein folding or stability.

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00937.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The synthesis and conformational studies of the oligopeptideN‐tert.‐butyloxycarbonyl‐l‐Leu‐(l‐Leu‐Gly)n‐OBzl (n = 1, 3, 5) andN‐tert.‐butyloxycarbonyl‐(l‐Leu‐Gly)2‐OBzl are described. The peptides were synthesized by stepwise and fragment condensation techniques using dicyclohexylcarbodiimide as the condensing agent in solution. The conformational study of the oligopeptides was carried out using CD, u.v. and i.r. spectra. The conformation in solution was examined in trifluoroethanol, hexafluoroisopropanol. hexafluoroacetone trihydrate, and methanol. CD spectra in trifluoroethanol exhibited a gradual variation with increasing peptide chain length. This can be interpreted as a formation of an ordered structure which is already present in the heptapeptide and, to a greater extent, in the undecapeptide. The results obtained from the CD profiles and i.r. spectra showed the presence of β structure with antiparallel chains in the heptapeptide and undecapeptide. Finally, CD spectra revealed in trifluoroethanol‐water solution the binding of Ca2+to heptapeptide and undecapeptide together with a contemporaneous conformational change. This change is probably due to the formation of β‐turns. No change in the CD profiles was obtained by using Mg2+, K+,

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00938.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY