摘要:

Isoleucine occurs in different conformations in the crystalline state and the various conformational aspects are analysed in the light of the energy calculations done earlier in this laboratory.

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03466.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Antithrombin III (AT‐III), being an α2‐globulin, will have an electrophoretic mobility in the presence of heparin like prealbumin in agarose gels. This phenomenon was utilized to quantitate AT‐III from serum and plasma by electroimmunodiffusion (EID) for 90 min in agarose gels containing 75 USP units of heparin/ml gel. The method permits a rapid quantitation of AT‐III from serum, citrated plasma and EDTA plasma, and a positive correlation was observed between these values and those obtained by single radial immunodiffusion (SRI). This is in contrast to quantitation of AT‐III by EID in gels containing no heparin where the values for plasma showed poor correlation with those obtai

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03467.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The ortho‐nitrobenzyl group (ONBzl) was utilized to protect the phenolic function of the side chain of tyrosine. Optimal conditions for its mild photolytic removal were established. This paper describes the preparation and properties of some (O‐ONBzl)‐tyrosine derivatives of potential value in the synthesis of tyrosine‐containing peptides. Their use in the synthesis of the dipeptide, N‐benzyloxycarbonyl‐L‐tyrosyl‐glycine ethyl ester is presente

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03468.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The effect of urea and GuHCl on the major protein of sesame seed (Sesamum indicumL.), α‐globulin, has been investigated by turbidity, sedimentation velocity, viscosity, difference spectra and fluorescence spectral measurements. The protein undergoes dissociation, aggregation and denaturation in the presence of the above denaturants. There is a critical concentration of the denaturant where aggregation is maximum. Both denaturation and aggregation are lower in buffers of high ionic strength. Dissociation and aggregation have been explained by considering two types of subunits present in the protein molecule, one leading to smaller sedimenting component and the other producing the aggregate. The amino acid analysis shows that the aggregated fraction is rich in aliphatic amino acid residues. The endothermic nature of the aggregation process has been considered to arise from hydrophobic interaction of aliphatic side chains of the relevant subunits. The protein exists in a more denatured state in GuHCl than in urea soluti

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03469.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Urogastrone is a potent inhibitor of gastric acid secretion which is present in human urine. Its existence has been known for over 30 years but it has only recently been isolated in a sufficiently pure form for detailed structural studies to be undertaken. Two separate polypeptides β‐ and γ‐urogastrone were isolated. The structures were established by carrying out enzymic degradations of S‐carboxymethyl and S‐carboxamidomethyl derivatives with trypsin, chymotrypsin, thermolysin and a protease derived from the fungusArmillaria mellea. Sequences of the smaller peptides thus obtained were determined by the dansyl Edman method. Partial acid hydrolysis of urogastrone itself gave fragments containing single intact disulphide bonds, and oxidation then allowed the direction of individual bonds to be established. β‐Urogastrone was shown to be a 53‐amino acid residue polypeptide containing three disulphide bonds, and γ‐urogastrone had an identical sequence but lacked the C‐terminal arginine residue.Urogastrone was subsequently found to be structurally related to mouse epidermal growth factor in that 37 of the 53 residues were commonly located in each polypeptide. Furthermore, as both peptides had similar effects upon gastric acid secretion and upon epidermal growth, urogastrone was also a human epidermal growth factor. The 16 variable residues were spread across the molecule, all apart from two were compatible with single base changes in the triplet codons, and the overall effect was to make urogastrone more acidic than EGF. The smallest biologically active unit has not been defined but at least six residues can be removed from the C‐terminus without causing a

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03470.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Bovine and equine growth hormones were chemically modified with tetranitromethane, at pH 7.4 during 5 h and at pH 8.0 in the presence of 8 M urea during 1 h.a) Both hormones have very similar but not identical reactivities.b) The nitration of the reactive tyrosines and tryptophan residues at pH 7.4 produces no detectable changes in their immunological or somatotrophic activities.c) The nitration of all tyrosine residues in both hormones gives rise to a complete loss of somatographic activity with no alteration of the immunological activity.

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03471.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

A simple preparative system is described for rapid and efficient purification of protected synthetic peptides on a gram scale by high performance liquid chromatography on prepacked silica gel 60 columns. A variety of protected peptides up to tetradecapeptides have been chromatographed at pressures of 50 to 150 psi and obtained in analytically pure form within 2 to 4h. With such commonly used protecting groups asN‐benzyloxycarbonyl (Z),N‐2‐(p‐biphenylyl)‐2‐propyloxycarbonyl (Bpoc),N‐t‐butyloxycarbonyl (Boc),O‐ andS‐t‐butyl (But), andS‐acetamidomethyl (Acm), compounds were sufficiently soluble in chloroform, alcohols, acetic acid, or mixtures of these solvents for column loading. Dimethylformamide was also used as a solvent for loading. Solvent systems for column elution in isocratic, stepwise, or gradient modes were composed of chloroform, isopropanol, ethanol or methanol and acetic acid in ratios that differed for each protected peptide depending on Rfvalues on t.l.c. plates. A simple chromatograph is described which was self‐assembled using standard instruments commonly in use in most laboratories. A shut‐off valve was designed to prevent loss of

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03472.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The synthesis, by fragment condensation, of protected peptides related to the N‐terminal (positions 1–14) and C‐terminal (positions 36–52) portions of the amino acid sequence of porcine pancreatic secretory trypsin inhibitor II (Kazal type) is described.The α‐carboxyl function of the lysyl residue in position 14 was used as the free acid, or protected by thetert‐butyloxycarbonylhydrazide.Two different synthetic pathways were used in the preparation of the 36–52 sequence of the inhibitor. The identity and purity of the synthesized peptide derivatives were established by amino acid analysis of acid hydrolysates, optical rotation and thin layer chromatography in two solvent systems. The final products were also evaluated, after partial deprotection with anhydrous hydrogen fluoride or aqueous 90% trifluoroacetic acid, by paper electrophoresis at different pH values and enzymic digestion with papain and aminopeptidase M followed by quantitative amino

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03473.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The secondary structure within histone IV and its fragments obtained by cyanogen bromide (CNBr) cleavage at Met 84 has been examined by circular dichroism and spectrophotometric pH titration measurements. These studies have confirmed the existence of stable secondary structure within the C‐terminal fragment of histone IV (C‐peptide) which can be perturbed only by 6 M urea at pH>8 or 8M guanidine ˙ HCl. In contrast, the N‐terminal fragment (N‐peptide) appears to lack significant secondary structure at low ionic strengths but acquires approximately 15%β‐sheet conformation and 5%α‐helix upon aggregation at ionic strengths ≥ 0.4.The rates of nitration of the N‐ and C‐peptides by tetranitromethane (TNM) have also been measured as a function of ionic strengths. Under comparable conditions, the rate constant for nitration of the N‐peptide was found to be about six times greater than that for the C‐peptide, further evidence in support of the presence of stable secondary structure within the C‐terminal region of histone IV. After binding these histone IV fragments to DNA, however, the nitration reaction rate constants for the N‐ and C‐peptide in the bound form are found to be 2% and 27% of the corresponding free peptides. Reconstituted nucleohistone IV is about 10% as reactive to TNM as histone I

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03474.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

When the backbone hydrogen bonding scheme of the protein triose phosphate isomerase is represented in the two‐dimensional map where the donor residue number (i) is taken along the x‐axis and the acceptor residue number (j) is taken along the y‐axis, the (i, j)‐map shows a characteristic pattern of (βα)8‐supersecondar

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03475.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY