摘要:

The effects of Li+ and H3O+ on the conformation of bovine serum albumin in aqueous solutions at room temperature are compared. At low pH (high concentration of H3O+) the change in conformation of the protein is demonstrated by an increase in effective volume, a decrease in helical content and a blue shift of tyrosyl residue. A similar change is observed for the protein in highly concentrated LiCl solution (6.0–7.0 M) at neutral pH. However, the H3O+ is 12,000 times more powerful than the Li+ in destabilizing the protein molecule. This is consistent with their thermodynamic and kinetic properties, since the H3O+ is often different from the Li+ in several orders of magnitude. While the changes in structural properties of the protein are almost identical in both the acidic solution and the highly concentrated LiCl solution, further study using dioxane as a probe suggests different mechanisms under which the changes occur. The effect of H3O+ is related to electrostatic force, whereas the effect of Li+ is related to both the electrostatic and hydrophobic forces. These two major forces are believed to be responsible for the conformation of protein molecule

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1975.tb02419.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Native, denatured, performic acid‐oxidized or S‐sulfo insulin and S‐sulfo or performic acid‐oxidized A‐ and B‐chains were digested with subtilisin type Carlsberg. The proteolysis was followed by measuring the uptake of alkali through autotitration. The kinetic study shows the existence of 2 first‐order reaction classes which differ markedly in rate constant. The number of bonds split with fast and with slow reactions has been calculated. Only one of a total of 12 cleavable bonds in native insulin is opened by fast reaction. In the denatured protein the number of bonds split by the fast reaction increases to 4 and in the oxidized and S‐sulfo protein 3 bonds are cleaved, while the slow cleavable bonds number 8 and 7, respectively. The kinetic study of the proteolysis of S‐sulfo A‐chain and of oxidized or S‐sulfo B‐chain shows that two bonds are split in A‐chain with the fast and slow reactions, while in B‐chain only one of the six cleavable bonds is

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1975.tb02420.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The synthesis of several sequential oligomer models of collagen is reported. Polytripeptides H(‐Pro‐Gly‐Leu‐)nOH, H(‐Pro‐Gly‐Phe‐)nOH, H(‐Pro‐Sar‐Gly‐)nOH, H‐(‐Sar‐Pro‐Gly‐)n‐OH, H(‐Pro‐Gly‐Val‐)nOH and H(‐Gly‐Val‐Pro‐)nOH were synthesized by the active ester method. Preliminary fractionation and mol.wt. determination showed typical gaussian distributions. Good yields were obtained in the mol.wt. range of 4,000–6,000, except in the case of H(‐Pro

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1975.tb02421.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The effects of carbamylation with potassium cyanate, and methylation with methyl p‐nitrobenzene sulphonate on the mesentericopeptidase activity are studied. The treatment with potassium cyanate causes the enzyme to lose its activity towards ester substrates and casein. The specific reagent N‐trans‐cinnamoylimidazole does not acylate the active site in the carbamylated enzyme. The pH dependence of the rate of inactivation indicates that an ionizing group of pK = 7.3, probably the protonated imidazole group of the active site histidine, is involved in the reaction. The competitive inhibitor boric acid protectsmesentericopeptidaseagainst inactivation with potassium cyanate. These results suggest that the active site residues are modified in the unprotected enzyme. Sixty per cent of the enzyme activity toward N‐acetyl‐L‐tyrosine ethyl ester was restored after treatment of the carbamylatedmesentericopeptidasewith 1 M hydroxylamine hydrochloride. Circular dichroism spectra show that the carbamylation does not change markedly the native protein conformation.Methyl p‐nitrobenzene sulphonate does not methylate the active s

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1975.tb02422.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Inhibited subtilisin (Subtilisin Carlsberg; Subtilopeptidase A) is unfolded in the presence of 7 M guanidine hydrochloride. The unfolding reaches a maximum in approximately 6 min at 20°C at pH 8.0. This is demonstrated by an increase of the mean residue ellipticity at 222 nm from ‐8.02 times 103to ‐1.72 times 103deg. cm2/decimole. The unfolding is partially reversible and this reversibility is favoured by lower concentrations of enzyme. The fact that the refolding process is not complete may be attributed to either the demonstrated self association of the denatured enzyme or to interference of non‐covalently bound autolysis pe

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1975.tb02423.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The synthesis of two protected peptides which correspond to positions 139–146 and 147–156 of the HGH primary structure is described. These peptides prepared by the stepwise procedure, are: Boc‐Phe‐Lys(Z)‐Gln‐Thr(Bzl)‐Tyr(Bzl)‐Ser(Bzl)‐Lys(Z)‐Phe‐OMe and Boc‐Asp(OBzl)‐Thr(Bzl)‐Asn‐Ser(Bzl)‐His(Dnp)‐Asn‐Asp(OBzl)‐Asp(OBzl)‐Ala‐Leu‐OBzl. All protected intermediates were

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1975.tb02424.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The crystal structure of an active 4‐oximino‐5‐imino‐pyrazoline ester has been determined by single‐crystal X‐ray diffraction methods. The possible reasons for its high reactivity towards nucleophilic reagents are briefl

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1975.tb02425.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The reactivity of arachin (principal storage protein of the peanut) with anti‐arachin decreased after arachin was heated at certain temperatures. Infrared and circular dichroic spectra of heated and unheated samples of arachin were examined to determine whether conformational modes changed concomitantly with decreased antigenicity. Infrared absorbances of each sample at amide I, II and V bands were essentially identical; however, absorbances at amide IV and VI bands were altered in relative intensities proportionally to the temperatures of treatment. Conformational modes, determined by circular dichroism, gradually increased in content of unordered structure from α‐helical and pleated sheet modes relative to the temperature of treatment. These observations are discussed in regard to relationships of the loss of antigenicity to conformational changes in heated ara

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1975.tb02426.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Human serum albumin has been modified with 2,4,6‐trinitrobenzenesulphonic acid and picryl chloride in low ratios of reagent/albumin. The derivatives have been investigated by spectrophotometry and by thin layer chromatography of the hydrolysates in order to assess the specificity of the reagents. The same reaction conditions were used to modify albumin previously complexed with bilirubin in the ratio of 1:1. The affinity of bilirubin to the modified albumins was estimated by an improved peroxidase method. It is concluded that TNBS and picryl chloride react almost quantity for quantity with ‐amino groups of lysine on the albumin molecule. The results also suggest that at least one TNBS reactive amino group and at least one picryl chloride reactive amino group are located in or near the high‐affinity bilirubin binding

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1975.tb02427.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

An isotope dilution assay for racemization during acid couplings is described and applied to carbodiimide‐mediated synthesis. Using the coupling of t‐BOC‐L‐phenylalanine with glycine derivatives as a model, racemization in solution falls in the 0.01 to 0.1% range and is a function of reagent concentrations. A typical coupling using the solid phase method shows 0.03% r

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1975.tb02428.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY