摘要:

The thiolysis of Nim‐2, 4‐dinitrophenyl‐histidine peptides with 2‐mercaptoethanol demonstrates an optimal rate between pH 8.5 and 9.0. Base lability of both reactants and product was investigated as a possible cause for the pH optimum. N‐2, 4‐Dinitrophenylimidazole, a model for Nim‐2, 4‐dinitrophenyl‐histidine peptides, 2‐mercaptoethanol and the product of thiolysis, 2, 4‐dinitrophenyl‐S‐mercaptoethan‐2‐ol, were subjected to aqueous basic conditions (pH 8.5 to 12.0). The reactions were followed spectrophotometrically, and products were identified by comparison of their ultra‐violet spectra with commercially available or synthetic compounds. Mechanisms and rate constants for base hydrolysis of 2, 4‐dinitrophenyl‐thio ethers are presented. Although N‐2, 4‐dinitrophenylimidazole and 2, 4‐dinitrophenyl‐S‐mercaptoethan‐2‐ol dohydrolyze, it is the oxidation of 2‐mercaptoethanol to 2‐mercaptoethanol disulfide which res

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02814.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

From a reexamination of the X‐ray studies of the crystal structures of 27 N‐acyl‐amino acids, peptides and their derivatives and 30 linear peptides, it is concluded that specific formation of short intermolecular hydrogen bonds (2.5 to 2.6 å) from the carboxyl OH to the N‐acyl oxygen is an important feature for N‐acyl‐amino acids. For N‐acyl‐N1‐amides, the formation of hydrogen bonds 2.7 to 2.9 å long between N(acyl)‐H … O(amide) is strongly preferred. The dihedral angle δ between the N‐acyl and carboxyl groups or adjacent amide groups shows a preference for values near 20° or 90° for N‐acylamino acid

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02815.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

The decapeptide corresponding to the amino acid sequence of porcine luteinizing hormone‐releasing hormone (LH‐RH) which involves 1 mol of tryptophan was synthesized via solid phase synthesis with two different deblocking procedures which used hydrogen chloride in formic acid and hydrogen chloride in acetic acid containing 1% 2‐mercaptoethanol. After some fundamental studies on the former reagent with respect to deblocking efficiency toward the Boc group, 0.5 M hydrogen chloride (a 10‐fold molar excess with respect to the N‐terminal Boc group) in formic acid was used in the present synthesis. The two synthetic products exhibited the same chemical and biological properties as an authentic LH‐RH. Hydrogen chloride in formic acid has proved effective without a scavenger although loss of peptide from the resin occurred to a somewhat greater extent than that with hydrogen chloride in acetic acid. A derivative of the synthetic LH‐RH formylated at the indole nitrogen had a greatly diminshed biological activity, indicating that the intact indole side chain is essential for

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02816.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

pH Conditions have been found which achieve selective reaction of diazotized p‐amino benzoate with cysteine residues of rabbit muscle aldolase. The difference in reactivity of the two sulphydryl groups involved, (Cys—237 and Cys—287) permits one to form either four or eight diazothioethers on the tetrameric enzyme and obtain a homogeneous protein. In both cases the enzyme became slightly more active in the fructose‐1, 6‐bisphosphate cleavage, the KMvalue being retained. The results have been discussed with regard to chemically modifying an enzyme to change its physical, chemical and immunological properties, whilst leaving the catalytical activity u

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02817.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

The steady‐state kinetics of the alkaline mesentericopeptidase‐catalysed hydrolysis of esters of the general formula Ac‐X‐OMe(OEt) has been studied, “X” being an amino acid residue (Ala, Val, Leu, Ile, Phe, Tyr, Trp, Lys). The values of the specificity ratio kcat/Kmindicate that the bonds involving the carboxyl group of amino acids with aromatic and bulky aliphatic side chain are hydrolysed most effectively. On account of this, alkaline mesentericopeptidase is classified as a chymotrypsin‐like alkaline protease. The primary specificity of mesentericopeptidase reveals the similarity of this enzyme to the group of subtilisins, as well as the distinctive characteristic feature of the enzyme to hydrolyse Ac‐Leu‐OMe with an efficiency practically equal to that of aromatic amino acid derivatives.Suggestions are made about the nature of the substrate‐binding centre, taking into consideration Schechter's and Berger's concepts of the se

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02818.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

The amino acid sequence of human plasma α1‐acid glycoprotein, upon comparison with the sequences of other blood proteins, was shown to possess significant similarity with the immunoglobulins. Employing direct and corrected sequence identity, the average mutation value and two different computer comparisons for the evaluation of sequence similarity, the following two regions of this α‐globulin, which account for approximately half of the total amino acid sequence of the protein, were found to possess sequence similarity with the immunoglobulins. a) The region from residues 77 through 125 proved to be related to the variable region of several human H and L chains, and b) the region from residues 136 through 166 was found to be related not only to the constant region of a human and a mouse L chain but also to the third and fourth constant region of a rabbit and a human H chain, respectively. These results suggest that α1‐acid glycoprotein is probably related to the immunoglobulins and further suggest that it possibly diverged from the immunoglobulin evolutionary tree prior to the formation of the primitive

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02819.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

SELECTIVE CLEAVAGE AT THE SINGLE TRYPTOPHAN RESIDUE IN BOVINE SOMATOTROPIN BY 2‐(2‐NITROPHENYLSULFENYL)‐3‐METHYL‐3′‐BROMOINDOLEMINEThe single tryptophan residue at position 86 in bovine somatotropin has been cleaved by the use of 2‐(2‐nitrophenylsulfenyl)‐3‐methyl‐3′‐bromoindolemine. This reaction was carried out with native bovine growth hormone as well as its reduced and alkylated derivative. When performed on the intact hormone, followed by the reduction and alkylation of the disulfides to liberate the two fragments, the cleavage reaction yielded the fragment containing residues 87–191 in a monomeric state. The other fragment, containing residues 1–86, could only be obtained in a highly aggregated form admixed with other material. When the cleavage reaction was carried out on the reduced and alkylated hormone, both the N‐terminal fragment of reduced‐carbamidomethylated bovine somatotropin as a monomer and the C‐terminal fragment as a dimer were obtained in 35–40% yield. Since the cleavage reaction also oxidized methionine to methionine sulfoxide, the sulfoxides were reduced back to the methionine with N‐methylmercapto acetamide. In this manner the following new derivatives and fragments of bovine somatotropin have been prepared: completely reduced and alkylated hormone, reduced and alkylated hormone with its methionines and tryptophan oxidized, reduced and alkylated hormone with its tryptophan oxidized, the N‐terminal fragment of the hormone containing residues 1–86 with its methionine and tryptophan oxidized, the C‐terminal fragment containing residues 87–191, both with its methionines oxidized and in their native state. The chemical and physical properties of these derivatives and fragments have been determined. Biological activity in the rat tibia was found t

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02820.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Though very effectively ibhibited by both SH‐group directed reagents and inhibitors typical for serine hydrolases, the inducible arylacylamidase from Pseudomonas acidovorans is a serine enzyme rather than a sulfhydryl enzyme. The amino acid sequence around the reactive serine residue is Gly‐Ser‐Ile. The sequence of a larger peptide from the active site is desc

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02821.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

An analysis of succinylated bovine serum albumin showed that all of the 62 α‐amino groups of lysine residues, 13 hydroxyamino acid residues and 12 tyrosin residues were succinylated, but the succinylated tyrosines were later deacylated. Structural properties of the modified protein have been studied with circular dichroism and sedimentation velocity. At neutral pH (pH 7.60) and in a salt‐free aqueous solution the modified protein is in an expanded form and its helical content is only 30% of that of unmodified protein. The increase of ionic strength restores the original conformation of the protein, whereas the increase of pH further disorganizes the structure of the protein. The results suggest that the electrostatic force alone is responsible for the compact structure of the protein molecule. The same mechanism is believed to underlie the effect of H3O+ and the effect of succinylation of side chain groups on the conformation of bovine serum alb

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02822.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Theoretical conformation studies have been carried out for the polytripeptides (Gly‐Pro‐Leu)nand (Gly‐Leu‐Pro)nand the Fourier transforms of the structures have been calculated. X‐ray powder patterns of these polymers had indicated that both these polymers take up coiled‐coil triple‐helical structures, but in the case of (Gly‐Pro‐Leu)nit was not clear whether the triple helix is formed by three parallel polypeptide chains or by a single chain folding back on itself (Scatturin et al 1975). Our studies show that both the polytripeptides can take up stereochemically satisfactory triple‐helical structures with three parallel chains. There is also very good agreement between the calculated intensity distribution and that of the observed X‐ray

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02823.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY