摘要:

The thermal triple helix coil transition of a blockpolymer with the sequence Boc‐(Gly‐Pro‐Pro)5‐(Gly‐Pro‐Leu)5‐(Gly‐Pro‐Pro)5‐NH2was studied optically. The collagen model peptide was soluble in methanol/water (9:1, 3:1) and was found to form triple helical structures in this solvent system. The thermodynamic analysis of the transition curves showed that the sequence (Gly‐Pro‐Leu)5is part of the triple helix after renaturat

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1981.tb02024.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Insoluble 2‐mercaptopyridine and 2‐mercapto‐nitrobenzene derivatives were prepared by modification of commercially available polystyrene. Applicability of these polymers as reagents for the thiolytic removal of the 2‐nitrophenyl‐sulphenyl amino‐protecting group and as supports for preparation of polymeric active esters was evaluated. Polymeric 2‐mercaptopyridine (PMP) was found efficient for both purposes. It was used in the stepwise synthesis of Leu‐enkephalin via the polymeric reagent approach, serving as an Nps‐cleaver. Polymeric esters derived from PMP and Boc‐amino acids proved to be excellent acylators. Their usefulness is exemplified in the preparation of two dipeptides, which were produced rapidly and in hig

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1981.tb02025.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Fructose 1,6‐biphosphate aldolase from Ceratitis capitata is a tetramer of identical subunits with 34% α‐helix, 22% β structure and 44% of aperiodic order. Increase of urea concentration up to 4.0 M results in non‐cooperative reversible dissociation of the enzyme. Sodium dodecylsulphate 0.06% (w/v) dissociates the tetramer cooperatively with retention of the helical content. Thermal denaturation was a non‐reversible cooperative process with a midpoint for the transition at 55°. Cysteine residues are involved in this process and 2‐mercapto‐ethanol preserves partially the enzyme activity. The acidic dissociation of the enzyme is a non‐reversible process in contrast to the reversible basic dissociation. Increase of ionic strength results in a more ordered secondary structure for the monomer after aci

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1981.tb02026.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The synthesis of locust adipokinetic hormone by the solid‐phase method is described. The synthetic product has been shown by bioassay to possess lipid‐mobilizing activity identical to that of the natural horm

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1981.tb02027.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Considering the three‐dimensional structure and the native Zn(II)‐binding ligands of carboxypeptidase A followed by extensive model building, a cyclic octapeptide, cyclo‐(Gly‐L‐Glu‐Gly‐Gly‐L‐His‐Gly‐L‐His‐Gly) was designed to mimic the Zn(II)‐binding site of carboxypeptidase A. The cyclic octapeptide was prepared by high dilution technique from the corresponding linear octapeptide, N‐Boc‐Gly‐γ‐OBut‐L‐Glu‐Gly‐Gly‐L‐His‐Gly‐L‐His‐Gly‐OBzlNO2via the azide method. The linear octapeptide was obtained by coupling of the two tetrapeptide fragments: N‐Boc‐Gly‐γ‐OBut‐L‐Glu‐Gly‐Gly‐ONp and L‐His‐Gly‐L‐His‐Gly‐OBzlNO2. The cyclic peptide was purified to homogeneity by the method of countercurrent distribution. The product obtained was both ninhydrin negative and Pauli's reagent positive. Further confirmation of this material was obtained by the proper amino acid ratio of its acid hydrolysate and by the proton magnetic resonance spectrum in which the various kinds of protons of this peptide were accounted for. A detailed13C‐ and1H‐n.m.r. investigation was undertaken to determine the Zn(II)‐binding ligands of the cyclo‐octapeptide. The assignments for all the resonances were attempted by pH titration, by employing homonuclear decoupling experiments and by synthesis of cyclo‐octapeptide containing specifically deuterated amino acids cyclo‐(Gly‐L‐Glu‐Gly‐d2‐Gly‐d2‐L‐His‐Gly‐L‐His‐Gly). Titration results of Zn(II) bound form of the cyclic peptide showed the presence of a 1:1 complex. Upon Zn(II)‐binding, the proton resonances were shifted downfield, the largest change being that of the histidine residues and more particularly C(2)‐H protons. The chemical shifts induced on glutamic acid residue were also observed for Glu CH2γ. In the case of13C resonances, the maximum change in chemical shift was observed in the histidine residues and especially in the imidazole ring upon complexation. Two methylenes of the glutamic acid residue showed a large change in chemical shift upon ligating to the metal ion. The most significant observation was the deshielding effect of the Glu COO‐group. The results demonstrate that Zn(II) binds both the

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1981.tb02028.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Two peptide anilides, Suc‐Tyr‐Leu‐Val‐pNA (III) and Ac‐Ser‐His‐I.eu‐Val‐pNA (V) were synthesized by the conventional method with the object of obtaining specific substrates for human spleen fibrinolytic proteinase (SFP). The Kcat/Kmvalues for hydrolysis of HI and V by SFP were 22 64 7 and 2 700, respectively. On the contrary, the Kcat/Kmvalues for hydrolysis of III and V by porcine pancreatic elastase were 21 an

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1981.tb02029.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The synthesis of three peptide sequences which are useful as histone models, [Lys]5,† [Lys]5‐Pro and the sequence 17–27 of the lysine‐rich histone from rabbit thymus Pro‐Ala‐Lys‐Lys‐Lys‐Lys‐Ala‐Ala‐Lys‐Lys‐Pro is described. Three different methods for the synthesis are applied. [Lys]5is synthesized from the amino end beginning with Nα‐acryloyl‐Ne‐Cbo‐lysine by successive coupling of Cbo‐lysine to yield the pentalysine monomer CH2=CH—CO—[Lys(Cbo)]5which can be used directly for radical copolymerization. [Lys]5‐Pro is synthesized according to the conventional peptide synthesis using the carbobenzoxy group for Nα‐protection and the tert.‐butyl group for side chain protection. The carboxyl function is protected as tert.‐butyl ester. The undecapeptide is synthesized in a similar manner. Instead of purifying the intermediate peptides by extraction, chromatography is used exclusively. The isolation of the unprotected peptides Lys‐Pro, [Lys]3‐Pro, [Lys]4‐Pro, [Lys]5‐Pro and Pro‐Ala‐[Lys]4‐[Ala]2‐[Lys]2‐Pro and their characterization using amino acid analysis, el

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1981.tb02030.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The conformational properties of theN‐acetyl‐N'‐methylamides of the dipeptides lysyl‐lysine, lysyl‐tyrosine, tyrosyl‐lysine, and tyrosyl‐tyrosine were studied by means of conformational energy calculations, by n.m.r. measurements in deuterated dimethylsulfoxide, and by circular dichroism in water, methanol, dioxane‐water, and trifluoroethanol. Since these four dipeptides occur occasionally as bends in proteins, it was of interest to see whether short‐range interactions, acting within the terminally blocked dipeptides, are sufficient to stabilize bend conformations significantly over other conformations. It was found that the four dipeptides exist as ensembles of conformations in solution. Therefore, it appears that longer‐range interactions, such as those present in proteins, are required if bend conformations of these dipeptide sequences are to exist as stable conformations. Three of the dipeptides behave rather similarly. Both the CD and the n.m.r. experiments and computations indicate that the fourth (Lys‐Tyr) differs from the others. It has a preference for compact conformations that appear to be stabilized by strong favorable interactions, primarily hydrogen bonds, between the tyrosyl and the lysyl side chains. The computations suggest that the presence of these interactions, and hence the existence of preferred conformations, is strongly solvent‐dependent, and that these interactions are weake

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1981.tb02031.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY