摘要:

Reduced and carbamidomethylated alpaca growth hormone was submitted to tryptic digestion. Peptides in the mixture were purified by reverse phase HPLC andN‐terminal determination and an amino acid analysis of each was performed. Data obtained and the already known primary structure of the equine growth hormone allowed the assembly‐by homology‐of a definite sequence of amino acids for the polypeptide chain of the protein. Present data provide further information about the relationship between growth fa

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1991.tb01428.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Vibrational Circular Dichroism (VCD) spectra of unblockedl‐proline oligopeptides, (Pro)nn = 3 to 7, dissolved in D2O are reported. For these oligomers, the VCD spectra can be attributed to a conformational dominance of thetransamide conformation with subunits interrelated by a left‐handed twist, particularly for the longer oligomers. As a function of oligomer length, formation of this conformation starts at n = 3; and by n = 5 a spectrum closely resembling that of the poly‐l‐proline II helix in shape and magnitude is seen. The VCD data are compared with previous (Pro)nresults using IR, CD, Raman and NMR spectroscopies, and reasons for the variations in interpretation are di

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1991.tb01429.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The receptor‐recognition site human transforming growth factor‐α (TGFα), a 50‐residue tricyclic peptide with three disulfide bonds, was mapped by a set of 46 peptide analogs consisting of linear, monocyclic, bicyclic, and tricyclic structures representing individual and overlapping subdomains of human TGFα. Linear overlapping fragments ranging from 7 to 18 residues and spanning the entire length of TGFα as well as monocyclic analogs with one disulfide linkage were found to be inactive in both receptor‐binding and mitogenic assays. Bicyclic analogs with two disulfide linkage and representing either the amino or carboxyl two‐thirds of TGFα showed low activity at 0.1–0.9 mmconcentrations. Tricyclic analogs containing all three disulfide linkages but lacking either the amino or carboxyl terminal heptapeptide was, respectively, 3% and 0.1 % as active as TGFα. These results show that determinants for the receptor binding cannot be represented by a short continuous fragment or a single subdomain, but are located on a discontinuous surface on a folded structure with disulfide restraints. Furthermore, these results when combined with our previous results which shows that the middle subdomain (second disulfide loop) is not involved in the receptor binding suggest that the receptor‐binding residues are constituted of three fragments located at the first and third subdomains as well as the extern

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1991.tb01430.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

We examined the binding capacity of anti‐metastatic polypeptide containing repetitive Arg‐Gly‐Asp(RGD) sequence derived from cell binding site of fibronectin, poly(RGD), to the surface of tumor cells. Poly(RGD) competitively inhibited the binding of radiolabeled fibronectin to the cell surface more potently than oligo(RGD) or RGD tripeptide on a molar basis. Compared on a weight basis to oligo(RGD) or RGD peptide, poly(RGD) was more active than the oligo‐ and monomeric peptide at inhibiting tumor cell adhesion to immobilized fibronectin. The secondary structure of poly(RGD) was predicted to be a β‐turn from the data of CD spectra and its amino acid sequence. These findings suggest that poly(RGD)‐mediated inhibition of cell adhesion is due to its potent binding capacity to fibronectin receptors on cell surface probably through its conformationa

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1991.tb01431.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

In order to elucidate the role of the aromatic side‐chains in the mechanism of transduction of monovalent cations through the channel of linear gramicidin, two series of analogues containing non‐coded aromatic amino acids were synthesized. In the first series, the four tryptophans were replaced by either fourl‐3‐(8‐quinolyl)alanyl or fourl‐3‐(4‐quinolyl)alanyl residues and single channel conductance measurements showed that these substitutions led to a strong lowering of the channel conductance, which is attributed to a modification of the orientation of the aromatic side‐chains due to an increase of their hydrophobicity. In the second series, the analogues contained both tryptophyl and naphthylalanyl residues in various amounts and positions. The single channel conductance data indicated that the conductance was mainly governed by the number of polar residues (Trp) and not by their positions. The conformational consequences of these results are discussed together with their influence on the energy profile of the g

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1991.tb01432.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The leucine zipper motif is a characteristic amino acid sequence found in dimeric DNA‐binding proteins. Computer‐generated models for leucine zippers were constructed as α‐helical coiled dimers with leucine repeated every seventh residue. An empirical Gibbs free energy, ΔG, function which incorporates hydrophobic force, electrostatic interactions, and conformational entropy loss as the major intermolecular interactions was used to estimate the ΔG of dimer formation infos, jun, and GCN4 zipper sequences. The calculations showed that complexes known to form stable homo‐ or heterodimers have favorable (negative) ΔG, while other less stable complexes have unfavorable (positive) ΔG. Leucines in positiondof the coiled coil contribute large hydrophobic stabilization energies while residues in theaposition contribute less to dimer stability. Hydrophobic contributions show little sequence specificity, however, and do not contribute significantly to homo/heterodimer preference. Charged residues in theeandgpositions, on the other hand, determine homo/heterodimer specificity. In GCN4 homodimers, residues GLUe1, Glub2, Lysg2, and Lyse4greatly contribute to dimer stability. The preferential stability offos‐junheterodimer over thejun‐junandfos‐foshomodimers is primarily due to the side chains Aspb1, Glug1, Aspb2, Glue2, Glug2, Glug3, and Lysa5of the fos helix, and Argc1, Lysg1, Lysb2, Lyse2, Arge4, and G

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1991.tb01433.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

A new Stereocontrolled synthesis of the Ψ[CH=CH] dipeptide isostere is described. They key step of the sequence relies on the stereospecific α‐alkylation of δ‐amino‐γ‐mesyloxy‐α,β‐unsaturated esters. The broad availability of nucleophilic α‐side chains by this method allows the preparation of a wide variety of Ψ[CH=CH]isosteres with predic

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1991.tb01434.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Conformational energy computations on Ac‐l‐(αMe)Val‐NHMe indicate that turns and right‐handed helical structures are particularly stable conformations for this chiral Cα‐methyl, Cα‐alkylglycyl residue. We have synthesized and characterized a variety ofl‐(αMe)Val derivatives and peptides (to the pentamer level). The results of the solution conformational analysis, performed using infrared absorption,1H nuclear magnetic resonance, and circular dichroism, are in general agreement with those obtained from the theoretical investigation, in the sense that thel‐(αMe)Val residue turns out to be a strong β‐turn and right‐handed helix former. A comparison is also made with the conclusions extracted from published work on peptides rich in other Cα‐met

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1991.tb01435.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Immobilized metal ion affinity chromatography (IMAC) is a useful method for purification of synthetic peptides with anN‐terminal metal‐binding amino acid such as His, Trp, or Cys, especially when such residues are not present in other parts of the molecule. In solid phase peptide synthesis (SPPS), capping with acetic anhydride will, in principle, produce truncated peptides as the only side‐products due to incomplete couplings. Consequently, only the desired product will carry the affinity label. Most of the impurities, therefore, can be removed by a single passage through an IMAC column. Some representative examples are presented, where fairly large peptides (30–40 amino acid residues) were efficiently purified by this a

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1991.tb01436.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Bovine plasma albumin (BPA) has 17 disulfide bonds and approximately one SH group at Cys‐34 which catalyzes the intramolecular SH, S‐S exchange reaction in the alkaline region at low ionic strength, resulting in the formation of the aged form (A‐form). 1) Fractions of α‐helix (fα) and β‐form (fβ) of iodoacetamide‐blocked non‐aged BPA (IA‐BPA) at pH 6.5 (the N‐form) and 9.0 (the B‐form) in the absence of added salt were 0.70, 0.12 and 0.62, 0.18, respectively (Eraet al.(1990)). However, there were no changes in fαand fβof the iodoacetamide‐blockedA‐form (IA‐A‐form) over the pH range from 5.5 to 9.1 in the absence of added salt or in 0.10mKCl(fα∼ 0.60, fβ∼ 0.20), indicating that the secondary structure of the IA‐A‐form might be similar to that of non‐aged IA‐BPA at pH 9.0 (B‐form) in the absence of added salt, that is, the frozen B‐form, stabilized covalently by the repairing of disulfide bonds. 2) The rigidity of theA‐ and IA‐A‐forms, as monitored by cross‐relaxation times between irradiated and observed protein protons, was similar to or slightly higher than that of non‐aged IA‐BPA or BMA. However, spin‐echo1H‐NMR spectra indicated that side chains of the IA‐A‐form, such as ɛ‐CH2of Lys, ‐CH3, in the absence of added salt are more mobile than those of non‐aged IA‐BPA. 3) The ratio of the hydrody

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1991.tb01437.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY