摘要:

Short range intramolecular interaction energies of a few amino acids with γ‐atoms are reported and their role in determining the molecular conformation has been again stressed. In serine and threonine, it is unlikely that the Oγ atom will occupy position II in which it is trans to the amino nitrogen. In cysteine, all three staggered positions of Sγ about the bond Cα‐Cβ become equally favourable. In valine, there is definite correlation between the orientation of the carboxyl group and that of the two γ‐methyl groups. In general, the backbone conformations of these amino acids are very similar to those of aminobutyric acid. The results indicate that even in amino acids containing hetero‐atoms in the side group where strong inter molecular interactions are possible, the molecular conformation is determined to a great extent by the intramolecular short range inter

ISSN:0020-7551    

DOI:10.1111/j.1399-3011.1971.tb01686.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Preferred conformations of the backbone and side‐chain of the amino acids, norvaline, leucine, phenylalanine, tyrosine, tryptophan, and histidine obtained by calculating the energies of conformations are reported. The conformations of non‐aromatic side groups are restricted to only certain values of χ1and χ2, and the backbone conformation is the same as shown for aminobutyric acid having a single γ ‐methyl group. The aromatic side groups prefer a perpendicular orientation about the bond Cβ‐Cγ and deviations from this orientation are characteristic of the position of the γ ‐atom. The experimentally observed conformations of amino acids with S‐atoms and aromatic groups in the side‐chain are compared with the theoretical predictions and the agreement is fo

ISSN:0020-7551    

DOI:10.1111/j.1399-3011.1971.tb01687.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Carefully performed amino acid analyses of the acidic polypeptides from the bovine eye lens protein α‐crystallin were in agreement with the recently found molecular weight of about 12,000 for these chains. The proposed amino acid composition is: (Asp10, Thr3, Ser15(14),Glu11, Pro7, Gly6, Ala4(3), Val6, Met, Ile5, Leu8, Tyr3, Phe8, Lys4, His4, Arg8, Cys, Try).On tryptic digestion both polypeptide chains yielded a rather small number of nin‐hydrin‐positive spots on peptide maps; 15 strong and 4 very light spots for A‐l and 14 strong and 4 light spots for A‐2.After blocking the ɛ‐amino groups of the lysine residues by trifluoro acetylation, the acidic chains, again, were submitted to tryptic digestion. Both chains, A‐l and A‐2, appeared to contain the same N‐terminus up to the first arginine residue. In connection with recent findings, its amino acid sequence is proposed to be:acetyl‐Met‐Asp‐Ile‐Ala‐Il

ISSN:0020-7551    

DOI:10.1111/j.1399-3011.1971.tb01688.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The paper deals with an analysis of the available crystal structure data related to proline compounds so as to obtain information about bond lengths, bond angles, and the conformation of the pyrrolidine ring. The interesting results are:1. The atoms Cβ, Cα, N, and Cß are nearly coplanar, with the torsion angle 0 about the Cα ‐ N bond varying from about ‐15° to ‐15°. The Cγ atom is displaced from this plane, either up or down, so that the ring exists in one of the two puckered conformations, designated A and B. Conformation A is characterized by negative and may be termed Cγ‐exo when referred to the displacement of the carbonyl carbon C. Conformation B has positive xland is Cγ‐endo; Cγ‐exo is slightly preferred over C‐endo, although both conformations occur simultaneously in some crystal structures with partial probabilities. In the other structures, the non‐occurring position for Cyis found to be disallowed by intermolecular contacts. The proline conformations observed correspond to the‘envelope’type of conformation of the cyclopentane ring. In peptides, the three bonds at N are nearly coplanar, and the torsion about N‐ Cα bond is nearly ‐ 60°.2. The observed ranges of (x1, x2, x3, x4)are (0 to –30°, 15 to 50°, –15 to ‐ ‐30°, 5 to 25°) for conformation A and (20 to 350, ‐30 to ‐ 400, 20 to 35°, 5 to ‐20°) for conformation B; for θ and φ the ranges are ‐15° to ‐15°, ‐45 to ‐75°. The bond lengths and bond angl

ISSN:0020-7551    

DOI:10.1111/j.1399-3011.1971.tb01689.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

An abnormal human hemoglobin was discovered in a woman living at Atago in Nagasaki and was designated Hb Atago.In the thin‐layer starch gel electrophoresis with Tris‐EDTA‐borate buffer, pH 8.6, the main component of this abnormal hemoglobin migrated towards the anode a little behind Hb F, and the minor abnormal component migrated to the same site as non‐hemoglobin protein did. These abnormal components were isolated by CM‐cellulose column chromatography. The hybridization method proved that the α chain of Hb Atago had the abnormality. The abnormal α chain was isolated by CM‐cellulose column chromatography in 8 M urea. The tryptic peptide map of the aminoethylated abnormal α chain showed that the abnormality existed in αT9. The abnormal αT9 was isolated and purified by high voltage paper electrophoresis. The abnormal chymotryptic peptides from αT9 were purified by high voltage paper electrophoresis and paper chromatography. The amino acid compositions of these peptides were analyzed.As a result, it was found that in Hb Atago, a tyrosine residue was substituted for the aspartic acid residue at α85 in the norma

ISSN:0020-7551    

DOI:10.1111/j.1399-3011.1971.tb01690.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Purified rat liver aminopeptidase B preparations were found to contain two molecular forms of the enzyme which can be separated by preparative electrophoresis on poly‐acrylamide columns. The one with higher electrophoretic mobility represents the actual liver enzyme and the one with lower electrophoretic mobility was seen to be derived most likely from hemolyzed red blood cells constantly present in liver homo‐genates. This was proved by purifying aminopeptidase B directly from isolated rat erythrocytes with the same procedure earlier used for the liver enzyme. The enzymic properties of the three enzymes (two derived from livers and one derived from erythrocytes) were seen to be largely the same. The similarity was especially considerable in the kinetics of the enzyme‐catalyzed reactions, where substrate inhibition was seen to be the most characteristic fe

ISSN:0020-7551    

DOI:10.1111/j.1399-3011.1971.tb01691.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

The thermal stability of DNA and of ribonuclease and the pH stability of ordered poly‐L‐lysine conformation in salt (or buffer) aqueous solutions and in 2‐3 M hexa‐methylene tetramine (HMT) aqueous solutions have been found to be nearly identical, respectively. We have also found that HMT induces salting‐out of acetyltetraglycine ethyl ester in water and rises the melting point of aqueous gelatin gels.It is assumed that, despite its pronounced ability in inducing salting‐in in water of apolar molecule (1, 2) (a property shared by all common “denaturants”), HMT leaves the thermal stability of DNA and polypeptides essentially unaltered either because of a lack of direct interactions with the polyelectrolytes considered or because of unfavourable interactions with solvated peptide groups of the denaturat

ISSN:0020-7551    

DOI:10.1111/j.1399-3011.1971.tb01692.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

ISSN:0020-7551    

DOI:10.1111/j.1399-3011.1971.tb01693.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

In prosecution of earlier studies from this laboratory, a detailed investigation on the potentialities of differential enthalpic analysis (DEA) in the evaluation of enthalpies of thermal denaturation as welt as of activation energies for the denaturation processes of three different proteins in concentrated aqueous solutions has been carried out. Our results suggest that DEA may indeed be an useful tool for the evaluation of such thermal and kinetic parameters despite some difficulties encountered in quantitation mainly because of the high biopolymer concentrations necessary with the DEA apparatuses available.

ISSN:0020-7551    

DOI:10.1111/j.1399-3011.1971.tb01694.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Electrometric and spectrophotometric titration curves of glycinin were obtained at 0.4 ionic strength and in the presence of 6M guanidine hydrochloride and 6M urea. The electrometric hydrogen ion titration curves were irreversible in the pH range 6.5 to 12.0 in 0.4M KCl, but exhibited reversibility in the pH 2.0 to pH 6.5 range. The forward and backward electrometric titration curves were entirely reversible in 6M guanidine hydrochloride. The spectrophotometric titration curves of tyrosine groups were also irreversible in 0.4M KCl, but reversible in 6M urea. Alkali‐induced denaturation produced a different spectrophotometric titration curve than the curves obtained with glycinin in 0.4M KCl and 6M urea. The electrostatic factor w was lower in the pH 2.50 to 3.75 range than in the pH 3.75 to 6.50 range. This was interpreted to be due to swelling and dissociation into subunits of the glycinin molecule subjected to acid denaturation. The empirical value of w=0.045 derived from the titration of the carboxyl groups in the pH 3.75 to 6.50 range coincided with the theoretically calculated value of 0.040 for a swollen sphere. Group counting and pK values of carboxyl, imidazole, e‐amino, and phenoxy groups under normal and denaturing conditions are also repor

ISSN:0020-7551    

DOI:10.1111/j.1399-3011.1971.tb01695.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY