摘要:

In the present study SDS polyacrylamide gel electrophoresis was used to reinvestigate the conditions under which b‐TSH dissociates into its constituent subunits. The effects of SDS itself, urea, acid pH and temperature were assessed by the decrease in the amount of undissociated TSH and the increase in the dissociated components as revealed by SDS gel electrophoresis. In SDS alone 25–30% dissociation occurred. Pre‐treatment with increasing concentrations of urea up to 7.1 M increased the degree of dissociation to 70% after 4 h at room temperature. Maximum dissociation was achieved by treatment at pH 2.5 and 37°C for 1 h. In 1 M propionic acid approximately 10% of the TSH was still undissociated after 18 hat

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02861.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

A cyclic tetradepsipeptide with a sequence corresponding to AM‐toxin II (a phytotoxic peptide) was synthesized in order to confirm the proposed structure by a conventional method. This was mediated through a dehydration reaction of cyclodepsipeptide containing a D‐Ser residue, by methanesulfonyl chloride containing sulfur dioxide. The synthetic peptide and natural AM‐toxin II were identical as regards t.l.c, crystal form, several kinds of spectra measurements and biological activity in causing necrosis on apple leaves. An analog, [L‐Phe1]‐AM‐toxin, containing the lower homolog (L‐phenylalanine) instead of L‐2‐amino‐5‐phenylpentanoic acid in position 1 of natural toxin II, was synthesized simultaneously. [L‐Phe1] ‐AM‐toxin showed extremely weak activity; the relationship between the bulkiness of an aromatic side chain and the biological activity

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02862.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

An insulin fragment containing residues A18–21and B19–26linked by the disulfide bond between residues A20and B19was synthesized. The sequence B21–26was assembled on a solid support by the Merrifield technique. The protected fragments A18–21and B19–20were prepared by conventional methods. After forming the disulfide bridge through cleavage of the S‐thiocarbonate derivative of A18–21by the thiol peptide B19–20, the resulting asymmetrical cystine peptide A18–21—B19–20was coupled via the carboxyl group of residue B20to the free NH2‐terminal amino group of the protected B21–26resin. The product was deprotected, cleaved from the resin, and purified to give the homogeneous do

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02863.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

Six protein fractions were isolated from mixtures of neuraminidase‐treated and untreated samples of human transferrin type C (TfC) in the 2Fe‐form by chromatography on DEAE‐cellulose. The first 2Fe‐TfC peak (designated TfC‐1–6) to desorb from the column did not contain sialic acid; The second (TfC‐2–6) and third (TfC‐3–6) peaks were intermediates between asialotransferrin and the least acidic component of native 2Fe‐TfC; The fourth, fifth and sixth (TfC‐4–6, ‐5–6 and ‐6‐6) peaks were identical with the three components described earlier for native 2Fe‐TfC. Ratios of N‐acetylneuraminic acid/galactose contents in all peaks were determined by gas‐liquid chromatography of the glycopeptides.Further heterogeneity in the carbohydrate composition of TfC‐1–6 was demonstrated with the aid of an affinity medium which was obtained by immobilising the asialoglycoprotein‐binding lectin from rabbit liver on Sepharose. This medium separated TfC‐1–6 into a retarded (‘low affinity’) and a retained (‘high affinity’) component, the ratios of which in TfC‐1–6 samples prepared from three individual donors were similar (83–84% and 16–17% respectively). Column chromatography on Sepharose‐concanavalin A (S‐con A) was used to identify the position in the normal DEAE‐chromatogram of those 2Fe‐TfC molecules which, in the desialylated state, give rise to the high‐affinity component in TfC‐1–6. S‐con A divided native 2Fe‐TfC into two components: one that passed through the column with 0.1M NaCl and another which could only be eluted by α‐methyl‐D‐glucoside. After mixing the former component with unfractionated TfC, the electrophoretic band corresponding to TfC‐6‐6 was markedly enriched, and when partially purified TfC‐6‐6 was chromatographed on S‐con A, a large portion of the load failed to specifically bind to the lectin. In contrast, TfC‐5–6 was nearly quantitatively retained by S‐con A. Resolution of TfC‐1–6 on S‐con A was similar to that of native 2Fe‐TfC. From animal studies the protein not retained by S‐con A was identified as high‐affinity TfC‐1–6, whereas the retained portion was of the low‐affinity type. These observations suggest that those 2Fe‐TfC molecules which, after desialylation, show high affinity for the hepatic lectin probably correspond to TfC‐6‐6 in the native state.Complete desialylation of TfC in a single incubation with neuraminidase appears virtual

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02864.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

The tightly packed protein interiors and interfaces are taken to be essentially solids. The tight packing, and the r‐6dependence of the energy of van der Waals' interactions may account for the highly conservative core regions of homologous proteins. The hydrophobic free energies used to calculate conformational stability and the association constants for protein‐protein interactions are not adequate, since the free energies are obtained from liquid‐liquid transfer of model compounds. An additional term is required, the enthalpy of fusion. This provides an additional 7 kcal mol‐1for the stabilization of the trypsin‐trypsin inhibito

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02865.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

The synthesis of βh‐endorphin* ‐(1–15), ‐(1–21), ‐(1–26), ‐(1–28) and ‐(1–29) have been accomplished by the solid‐phase method. The opiate activities of the peptides were measured in the guinea pig ileum assay. Their relative potencies were βh‐endorphin (βh‐EP), 1.00; Met‐enkephalin, 0.25; βh‐EP‐(1–15), 0.17; βh‐EP‐(1–21), 0.46; βh‐EP‐(

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02866.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY

摘要:

This survey of the atom packing in the high resolution X‐ray crystal structures of 21 proteins indicates that the atom density around a given central atom is determined primarily by its covalently bonded neighbors and proximity to the surface of the protein. Long‐range hydrophobic, hydrogen bonding, and electrostatic interactions are strictly of secondary importance. Both radial and angular atom densities were calculated about various central atoms of several residue types, averaged over all occurrences of the chosen residue type in all 21 proteins. Polar interactions, such as hydrogen bonding, involve on the average shorter distances than hydrophobic interactions do, and are more directional. Spatial segregation of polar and non‐polar atoms is never complete in long‐range interactions since the types of atoms are linked together cov

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1978.tb02867.x

出版商:Blackwell Publishing Ltd    

年代:1978

数据来源: WILEY