摘要:

The cleavage of oxidized glutathione by alkali has been studied as representative of the cleavage of protein disulfides. This process is quite different when studied in 10‐4N or 2 ˙ 10‐1N NaOH. At low alkali concentration no spectral changes are noted; at higher hydroxyl concentration the appearance of persulfide groups (followed at 335 nm), the formation of thiocyanate (arising from cold cyanolysis of persulfide groups) and the absorbance at 240 nm follow the same kinetics. The amount of half‐cystine, recovered as cysteic acid after a 3‐h reaction, is significantly lower than calculated.These results confirm that oxidized glutathione undergoes β‐elimination at high pH values, and that persulfide groups absorb not only at 335 nm (as already known) but also at 240 nm where, under our conditions, the contribution of other absorbing species is no

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb01732.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Male Wistar rats were treated with Mo in a single dose or over a period of 84 days. The course of molybdenum excretion after a single dose was expressed mathematically. It was shown that various tissues produced different excretion curves and a high retention was observed only in skin. In long‐term treatment it was possible to ascribe this retention to direct binding of molybdenum to collagen. In contrast to some other heavy metals molybdenum causes a decrease of collagen stability. The mechanism of this effect is discusse

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb01733.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

An AM‐toxin analog, cyclotetradepsipeptide, containing anO‐methyl‐l‐tyrosine residue in place of anl‐2‐amino‐5‐arylpentanoic acid residue in AM‐toxins has been prepared by a conventional method. The synthesis was attempted through six different routes and the desired analog was obtained by one such procedure. This compound showed extremely weak activity in causing necrosi

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb01734.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Synthesis of a cyclohexadepsipeptide corresponding to the sequence of protodestruxin from linear hexapeptides was attempted through five different routes in a conventional method, and three routes afforded the same cyclopeptide. Biological and physicochemical properties of the synthetic peptide were identical to those of natural protodestruxin. Differences in the yields of the cyclization were explained through the assumed conformations of the linear hexapeptides.

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb01735.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The kinetic study of fluorescence stopped‐flow method suggested that the interaction between lipoxygenase and H2O2is consistent with a simple irreversible one‐step mechanism. The activation energy of the reaction was 7.2 kcal/mol. Participation of an ionizable group with pK about 8.8, possibly a histidine residue, was suggested from the pH‐dependence of the rate constant. No further fluorescence quenching of lipoxygenase was observed when the product was added to the lipoxygenase solution before mixing the lipoxygenase and H2O2solutions. The fluorescence quenching of lipoxygenase by H2O2was in parallel with the inactivation of the enzyme. Hydroperoxylinoleic acid strongly protects the inactivation of lipoxygenase caused by H2O2. These results are consistent with an interpretation that OH and/or O‐are produced when the iron of the enzyme is oxidized by H2O2, which in turn will attack some amino acid essential for the enzyme activity. The pH‐dependence of the inactivation rate constant of photooxidation of lipoxygenase sensitized by methylene blue indicated that an ionizable group with pK about 8.8 is concerned with the enzymatic activity. In contrast to the inactivation of lipoxygenase by H2O2, the product protected the inactivation of the enzyme by photooxidation only at high conc

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb01736.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Some perturbing solvents appear to be short‐range perturbants at 20% concentration, but long‐range at 40%, based on Δε/ε for phenols and their ethers. The apparent long‐ or short‐range character of a solvent also depends on the chromophore. It is possible that perturbants, which are apparently of long‐range character at 20% concentration, are really of short‐range character because they interact rather similarly with phenols and their ethers. For ethers Δε/ε increases faster than for phenols with increasing concentrations of

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb01737.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

A secretory glycoprotein was isolated from the hamster sublingual gland. It contains 65% carbohydrates, the remainder being protein. The principal type of sialic acid was identified asN‐acetylneuraminic acid with about 1/4 of the moleculesO‐acetylated. The hexosamine occurs mainly asN‐acetylgalactosamine; other sugars present are galactose and fucose. The carbohydrate side chains are linked to the protein core by anO‐glycosyl linkage between seryl and threonyl residues andN‐acetylgalactosamine. The glycoprotein has an apparent molecular weight of 330,000. The sialoglycoprotein may act as a biological antifreeze. Relevant differences in the chemical composition of the secretory glycoproteins of the sublingual and submaxillary salivary glands of this species are briefly

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb01738.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Conformational analysis of cyclo(L‐cystine) shows that the diketopiperazine ring has to exist only in the boat form. With this geometry, the molecule can adopt two distinct forms differing mainly in the chirality of the disulphide bridge. In both the P‐ and M‐models, corresponding to dihedral angles of nearly + 90° and —90° respectively about the S‐S bond, the molecule displays an approximate two‐fold symmetry. According to our semi‐empirical energy calculations, the minimum energy of the M‐model is —9.2 kcal/mol, only 0.3 kcal/mol lower than that of the P‐model. Because the difference between the two minima is so small, neither form is clearly superior to the other. However, the number of low energy conformations of the M‐model in the allowed conformational space is significantly larger than that of the P‐model by a ratio of 3 to 1, and therefore the former is likely to be t

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb01739.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

1‐Deamino‐4‐L‐valine‐8‐DL‐homolysine‐vasopressin and protected 1‐deamino‐4‐L‐valine‐8‐D‐lysine‐vasopressin were synthesized by the solid phase method and were then converted into the title compounds (dVDHLVP and dVDHAVP) by tryptic digestion and e‐guanidination, respectively. The new hormone analogues exhibit only moderate antidiuretic potency, dVDHLVP 21 units/mg and dVDHA VP 31 units/mg, but since they are essentially devoid of pressor activity (0.01 units/mg) the A/P ratios are very high. In fact, dVDHLVP is the most specific antidiuretic agent

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb01740.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

We have predicted the secondary structure of 38 snake venom toxins using the method of Chou and Fasman. Our predictions indicate that β‐chain and random coil structures predominate in these proteins. The conformations of long neurotoxins, short neurotoxins and cytotoxins are less similar than previously believed Cytotoxins contain 40–50% of β‐structure and they form a notably homogeneous group. Short neurotoxins contain less β‐structure (13–30%) and more random coil than cytotoxins, and they also form a more heterogeneous group in terms of secondary structure. The characteristics of long neurotoxins are intermediate to the above mentioned groups. Experimental evidence supporting these propositions

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb01741.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY