摘要:

4‐Arsono‐2‐nitrofluorobenzene reacts selectively at the anion binding site of bovine pancreatic ribonuclease A. The major derivative is the inactive 41‐(4‐arsono‐2‐nitrophenyl) ribonuclease A (45% yield). Additional products are 1‐α‐(4‐arsono‐2‐nitrophenyl) ribonuclease A (11% yield) which is enzymatically active and the disubstituted, inactive 1,41‐bis‐(4‐arsono‐2‐nitrophenyl) ribonuclease A (25% yield). 2′ (3′)‐O‐Bromoacetyluridine reacts with 41‐(4‐arsono‐2‐nitrophenyl) ribonuclease A exclusively at the histidine‐12 residue at a rate which is approximately one‐fourth the rate observed with the unmodified enzyme. Saturation kinetics are observed and the dissociation constant for the protein‐inhibitor complex is 0.096 ± 0.023 M. The first‐order unimolecular decomposition constant for complex breakdown is 8.9 ± 2.9 times 10‐4s‐1. 2′‐Bromoacetamido‐2′‐deoxyuridine reacts with 41‐(4‐arsono‐2‐nitrophenyl) ribonuclease A 25 times more slowly than 2′(3′)‐O‐bromoacetyluridine. Bromo‐acetate reacts with 41‐(4‐arsono‐2‐nitrophenyl) ribonuclease A predominantly at the histidine‐119 residue at a rate 45 times less than that found for the unmodified enzyme. The results of the alkylation studies imply that the dianionic arsonate does not occupy the phosphate binding site in the enzyme but is sufficiently proximate to account for a decrease in bromoacetate binding as well as a reduction in the nucleophilic reactivity of histidine‐12 and ‐119. All these effects may be accounted f

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb00921.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb00922.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

In order to elucidate the role of tertiary peptide bonds in the conformational development and solubility improvement of peptides, the conformational properties of oligo(Leu)s with the Pro residue and the Gly‐(Dmob)Leu sequence were investigated in solution using i.r. absorption, CD, and molar rotation measurements. The i.r. absorption spectroscopy indicated that the peptides soluble in inert solvents such as CCl4and toluene had a predominantly β‐sheet structure in these solvents. The conformations of the peptides in CCl4and toluene were essentially the same as those in a solid state, whereas in THF and in MeOH, the peptides examined were efficiently subjected to solvation, and a randomly coiled structure was predominant. In order to confirm the randomly coiled structure, measurements have been made of the molar rotations of the peptides in a variety of strong proton acceptor and donor solvents. CD measurements are also carried out in MeOH. Through the investigations, it was shown that the protection of peptide bonds and the insertion of the Pro residue had the same effect on conformational and solubilizing behaviors and induced onset of an unordered structure and easy solvation of the peptides in medium and high polarity‐so

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb00923.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The preferential association of amino acid side groups with specific side chain atoms are examined in 44 known protein structures. The resulting association potentials among residue side groups are used to detect structural homology in proteins displaying little or no homology in their primary sequences. Suggestions are also made regarding the nature of the protein folding process. They are based on statistical observations that delineate the extent of short and long range interactions and that display side group bias in association with other side chain atoms on theirN‐terminal sid

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb00924.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Stereoselectively β‐deuterated species were synthesized of Ac‐His‐NHMe, Ac‐His‐OEt, Ac‐His‐OH and H‐His‐NHMe, which are useful as models of histidine residues in peptides. From the spectral comparison of1H n.m.r., the β‐proton resonances of the normal species were unambiguously assigned. In (C2H3)2SO, C22H5O2H, C2H3O2H, and C52H5N solution and in aqueous solution, the lower‐field and higher‐field components of β‐proton resonances of the four histidine derivatives are assigned to the pro‐R and pro‐S protons, respectively. The alternative assignments apply for Ac‐His‐NHMe, Ac‐His‐OEt and Ac‐His‐OH in non‐polar solvents such as C2HCl3. Vicinal coupling constants3JαβSand3JαβRwere obtained for calculating the fractional populations of rotamers about the Cα–Cβbond. The rotamer populations depend little on the ionization states of the α‐amino and carboxyl groups or the imidazole ring. The rotamer populations depend significantly on the solvent polarity, similar to those of Phe, Tyr and Trp derivatives. For the two β‐proton resonances of His, Phe, Tyr, and Trp derivatives in a variety of solvents, linear relationships are found between the differences in chemi

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb00925.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Solution conformation of poly(L‐lysyl‐L‐glutamic acid) (PLGU) and poly(L‐lysyl‐L‐glutamine) (PLGN) was studied in water as a function of pH, added salt, detergents, methanol and trifluoroethanol (TFE). Both the polypeptides exhibit no ordered conformation in the pH range 1.5–12.5; salts and detergents did not have any marked effect. Replacement of side chain carboxyl by an amide group did not help in inducing PLGN to adopt a helical conformation even at pH as high as 12.0, unlike poly(L‐lysine). The helicogenic solvents, methanol and TFE, induce formation of weak helices in PLGU as well as in PLGN. It is not unlikely that H‐bonding between the side chains leads to stabilizing an unorde

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb00926.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

L‐tyrosyl‐L‐tyrosine crystallizes as a dihydrate in the orthorhombic system, space group C2221, with a = 12.105(2), b = 12.789(2), c = 24.492(3) Å, Z = 8. The structure was solved by direct methods and refined to a final R‐value of 0.059 for 1740 observed reflections. The molecule exists as a zwitterion, the peptide unit istransplanar, and the backbone torsion angles correspond to an extended conformation, with e1= 149.4°, e2= ‐ 161.2°, e2= 158.3°. The values of the side‐chain torsion angles (χ1, χ2) are (‐ 58.8°, ‐ 63.1°) for the first tyrosine and (‐ 171.7°, ‐ 116.5°) for the second. The planes of the aromatic rings are nearly parallel (dihedral angle of 6.1°), and their centers are separated by 10.9 Å. The carboxyl plane forms a dihedral angle of 23.8° wi

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb00927.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Acetylenic analogues of tuftsin (Thr‐Dah‐Pro‐Arg) and of a macrophage inhibitory tripeptide (Thr‐Dah‐Pro) have been synthesized by conventional procedures in solution (Dah = 2,6‐diamino‐4‐hexynoic acid). These acetylenic derivatives are intermediates for the preparation of structurally unmodified, tritiated peptides. Catalytic tritiation of Thr‐Dah‐Pro‐Arg and of Thr‐Dah‐Pro has afforded the radioactive tetra‐ and tripeptides with specific activities of 11.4 Ci/mmol a

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb00928.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Neurohypophyseal hormones are fragments of precursor proteins that include specific neurophysins and are processed during axonal transport. Neurohormones and neurophysins purified from 7–9 month old bovine foetuses have been characterized by amino acid analysis and partial amino acid sequences. Oxytocin and arginine vasopressin, on one hand, and VLDV‐neurophysin and MSEL‐neurophysin, on the other, are identical to products previously characterized in the adult. Whereas oxytocin and vasopressin genes seem to be expressed at the same rates in the adult, as judged by the amounts of their peptide products in neurohypophysis, in the late foetus the vasopressin gene appears to be roughly three times more active than the oxytocin

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb00929.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

β‐endorphin administered intraventricularly into pentobarbital anaesthetized rats led to a reduction in rectal temperature and a dose dependent biphasic response in metabolic rate with increase at low doses (7–10 nmol/kg) and decrease at high doses (30–300 nmol/kg) in rats acclimated to 22°. These metabolic responses to β‐endorphin were enhanced both in magnitude and in duration in rats acclimated to 5° for 3 weeks, indicating an increased responsiveness to β‐endorphin. Naloxone antagonized the metabolic effects of β‐endorphin in rats acclimated to both 22° and 5°, indicating the metabolic effects of β‐endorphin were via the naloxone sens

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb00930.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY