ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1979.tb01842.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

A study of the efficiency of partition chromatography for the purification of peptides as a function of structure has been undertaken. A series of 19 omission analogs of camel β‐endorphin and of some of its partial sequences have been synthesized with each analog missing only a single amino acid. Their chromatographic properties have been examined with use of the Martin hypothesis and the RMconcept, and a hydrophobicity scale for the amino acid side chains was obtained. To a first approximation a correlation with the Tanford hydrophobicity scale for amino acids was found. A decrease in hydrophobicity has been observed with increasing chain length and is discussed in terms of column efficiencies required for the purification of synthetic peptid

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1979.tb01843.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Experimental conditions and parameters involved in high performance liquid chromatography (HPLC) separations of the peptide hormone oxytocin and seven of its diastereoisomers, namely [1‐hemi‐d‐cystine]‐, [2‐d‐tyrosine]‐, [4‐d‐glutamine]‐, [5‐d‐asparagine]‐, [6‐hemi‐d‐cystine‐], [7‐d‐proline]‐, and [8‐d‐leucine]‐oxytocin, on reverse phase columns were investigated. The effects of solvent, pH, and salt concentration were studied. Using the solvent systems 10% tetrahydrofuran‐ammonium acetate buffer or 18% acetonitrile‐ammonium acetate buffer and the üBondapak C18support, oxytocin was separated from each of its diastereoisomers under all conditions studied, but the order of elution of diastereoisomers was highly dependent on solvent and to a lesser extent on pH. Separations of the hormone and its diastereoisomers on reverse phase HPLC and on classical partition chromatography on Sephadex G‐25 were compared. The results are discussed in terms of the interactions of the solute with the reverse phase column and the solvent system. Implications of these findings in terms of the different

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1979.tb01844.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Acylation of the hydroxyl groups in the side chains of serine, threonine or tyrosine occurs in coupling with active esters. This side reaction, which is quite pronounced in histidine‐containing peptides, can be prevented with additives. From a series of compounds tested, 2,4‐dinitrophenol and pentachlorophenol were the most effect

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1979.tb01845.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Haloacetylamino acids and haloacetyl peptides react rapidly with 2‐aminothiophenol in weakly alkaline media to yield 2‐aminothiophenoxyacetyl derivatives. These intermediates are subject to acidolysis under mild conditions with release of free amino acids or peptides. With this mild method for removal of the haloacetyl group N‐haloacetoxysuccinimide derivatives, which rapidly and specifically acylate amino groups of polypeptides in aqueous solutions, become promising reagents for the reversible protection of amino groups. The chloro‐acetylation of amino groups in lima bean trypsin inhibitor and the quantitative removal of the chloroacetyl groups demonstrate the applicability of the method for polypeptides. The haloacetyl group also serves an analytical function in that treatment of a completely or partially haloacetylated polypeptide with cysteine forms one carboxymethylcysteine residue per haloacetyl group in the polypeptide derivative. Carboxymethylcysteine is readily measured by amino acid analysis of acid hydrolysates.Approaches to further improvement of conditions for removal of haloacetyl groups are discussed and potential applications of the general chemistry of 2‐haloacids to modern polypeptide chemistry are

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1979.tb01846.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The utility of repetitive nonhydrolytic base cleavage of α‐amino protective groups in solid phase peptide synthesis is shown by a preparation of the model tetrapeptide leucyl‐alanyl‐glycyl‐valine on a p‐benzyloxybenzyl ester polystyrene–1% divinylbenzene resin support.Nα‐9‐Fluorenylmethyloxycarbonyl (Fmoc: Carpino&Han, 1970, 1972) amino acids were coupled by the symmetrical anhydride procedure, followed by Fmoc group cleavage using 50% piperidine in methylene chloride. Quantitative removal of the Fmoc‐tetrapeptide from the solid support was effected by treatment with 55% trifluoroacetic acid in methylene chloride. Homogeneous free tetrapeptide was obtained in 87% overall yield. The procedure is proposed to offer advantages over present solid phase methods which use acidolysis for repetitive α‐

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1979.tb01847.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

An analog of sheep insulin which differs from the parent molecule in that the C‐terminal amino acid residue of the A chain, asparagine, is replaced by arginine, has been synthesized and isolated in highly purified form. The [Arg21] A chain of sheep insulin was synthesized by the fragment condensation approach and isolated as the S‐sulfonated derivative. Conversion of the latter into the sulfhydryl form and interaction with the S‐sulfonated B chain of bovine (sheep) insulin yielded [Arg21‐A] sheep insulin, which was purified by chromatography on a carboxymethylcellulose column with an exponential sodium chloride gradient. The [Arg21‐A] sheep insulin shows potencies of 10.5–12.5 IU/mg when assayed by the mouse convulsion method and 8.6 IU/mg by the radioimmunoassay method (cf. 23–25 IU/mg for the natural hormone). It has been suggested that in the insulin molecule the A21asparagine participates in salt bridge‐ and hydrogen bond‐forming interactions which are critical in the biological activity of the hormone. Although the [Arg21‐A] analog still retains these interactions, it is only ca. 50% as active as the natural hormone. It is speculated that other factors than the abovementioned interactions come into play, which involve the side chain of the A21amino acid residue and affect the biological acti

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1979.tb01848.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

A complex between bovine lutropin (LH) and monovalent antibodies (Fab fragments) directed against its α subunit, which is common to the glycoprotein hormones, has been purified by gel filtration and chromatography on concanavalin A‐Sepharose. The complex is heterogeneous with respect to molecular size; 70–80% of the hormone is complexed with either two or three Fab fragments. The LH‐Fab α complexes retain only about 13% receptor binding activity as compared to LH when measured in a radioligand receptor assay in which the radiolabeled ligand is human choriogonadotropin. (Use of the human hormone as labeled ligand permits direct measurement of competition between receptor and the bovine complex because the α portion of the human hormone does not cross react significantly with antibodies directed against bovine α subunits.) Complex formation does not lead to dissociation of the lutropin into its subunits, as shown with a homologous LH‐β immunoassay which distinguishes free β subunit from intact LH. Complexing of LH with Fab‐α fragments also causes little or no change in the affinity of the hormone's β subunit for anti‐LH‐β antibodies indicating that significant changes in β subunit conformation did not occur. The data show that at least two well‐separated antigenic regions on the α subunit are exposed to the surface in the intact hormone. They are also in agreement with the proposal that the loss of binding activity to receptor is due to steric effects rather than to changes in conformation or dissociation, and that there may be sites on the α subunit which interact

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1979.tb01849.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

The purification of rabbit lutropin is described. A product with a potency of 1.53 × NIH‐LH‐Sl was obtained as assayed by the ovarian ascorbic acid depletion assay. In a homologous radioimmunoassay, which is described, rabbit lutropin has a potency 4.83 × NIH‐LH‐Sl. In a radioligand assay, utilizing labeled ovine lutropin as the trace, the relative potency was 0.47 × NIH‐LH‐Sl measured by 50% inhibition comparison since rabbit lutropin response in this system did not parallel ovine lutropin.A counter‐current distribution procedure for separation of rabbit lutropin subunits is described. Amino acid composition of the isolated subunits and intact rabbit lutropin was determined. The carbohydrate composition of the latter is presented; only amino sugar determinations are available for the subunits. The NH2‐terminal amino acids are phenylalanine (alpha subunit) and alanine (beta subunit). Preliminary data on COOH‐terminal amin

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1979.tb01850.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Analysis of the 220 MHz proton magnetic resonance spectra of bovine neurophysins‐I and ‐II and of the effects of pH and succinylation on these spectra has allowed identification of the ‐CH3proton resonances of the amino‐terminal alanine of both proteins and of the ‐CH3resonance of methionine‐2 of neurophysin‐II. The alanine ‐CH3resonance of neurophysin‐I is a sharp doublet at all pH values between 1 and 10.5 indicating relatively few restrictions on its mobility. By contrast, the ‐CH3resonances of the amino‐terminal alanine and methionine‐2 of neurophysin‐II undergo pH‐dependent changes in broadening compatible with the formation of an intramolecular salt‐bridge at neutral pH between the protonated α‐amino and an unprotonated side chain carboxyl. The results suggest that differences in the properties of the two proteins are partially mediated by conformational differences involving their amino‐terminal sequences. The potential usefulness of the amino‐terminal resonances as n.m.r. ‘reporter’ signals is additionally demonstrated by studies of the effects of spin labels on the neurophysin‐I amino‐terminal alanine resonance; these studies place the amino‐terminus of neurophysin‐I approximately 14 Å from residue 3 of peptides bou

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1979.tb01851.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY