摘要:

This review article, based on a lecture delivered in Madras in 1985, is an account of the author's experience in the working out of the molecular structure and conformation of the collagen triple‐helix over the years 1952–78. It starts with the first proposal of the correct triple‐helix in 1954, but with three residues per turn, which was later refined in 1955 into a coiled‐coil structure with approximately 3.3 residues per turn. The structure readily fitted proline and hydroxyproline residues and required glycine as every third residue in each of the three chains. The controversy regarding the number of hydrogen bonds per tripeptide could not be resolved by X‐ray diffraction or energy minimization, but physicochemical data, obtained in other laboratories during 1961–65, strongly pointed to two hydrogen bonds, as suggested by the author. However, it was felt that the structure with one straight NH … O bond was better. A reconciliation of the two was obtained in Chicago in 1968, by showing that the second hydrogen bond isviaa water molecule, which makes it weaker, as found in the physicochemical studies mentioned above. This water molecule was also shown, in 1973, to take part in further cross‐linking hydrogen bonds with the OH group of hydroxyproline, which occurred always in the location previous to glycine, and is at the right distance from the water. Thus, almost all features of the primary structure, X‐ray pattern, optical and hydrodynamic data, and the role of hydroxyproline in stabilising the triple helical structure, have been satisfactorily accounted for. These also lead to a confirmation of Pauling's theory that vitamin C improves immunity to diseases, as explained in

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00001.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The binding of bilirubin with adult or fetal human serum albumin has been studied by steady‐state fluorescence emission spectroscopy. The 1:1 complex between bilirubin and the two albumin samples shows very similar fluorescence properties, as well as essentially identical accessibility of the protein‐bound bilirubin to fluorescence quenchers added to the aqueous medium. The intramolecular distance between bilirubin and the single tryptophyl residue can be estimated to be 2.4 ± 0.2 nm for both proteins by singlet‐singlet energy transfer. These findings suggest that fetal and adult human serum albumin have a very similar three‐dimensional structure; the different binding capacity for bilirubin displayed by the two proteins is likely to be the consequence of small differences in the physico‐chemical properties of some amino acid residues close to the bilirubin binding site, as indicated by pH‐titration experiments of the intrinsic albumin

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00002.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The structure‐conformation relationships of a series of angiotensinogen6–13(ANG6–13, His‐Pro‐Phe‐His‐Leu‐Val‐Ile‐His) congeners substituted byNin‐For‐Trp (Ftr),d‐Ftr or Trp at theN‐terminus, Tyr at theC‐terminus and PheΨ[CH2NH]Phe at the P1‐P′1cleavage site (i.e. Leu10‐Val11) were studied using resonance energy transfer coupled with molecular modeling of the peptide conformation using macromolecular energy refinement and dynamics simulation. Average end‐to‐end intramolecular distances (r) of the peptides in solution were determined by fluorescence spectroscopy. For example, Ac‐Ftr‐Pro‐Phe‐His‐PheΨ[CH2NH]Phe‐Val‐Tyr‐NH2(U‐70714E) gave an average intramolecular donor (Tyr)‐acceptor (Ftr) distance of 16.3 Å in aqueous solution. This experimental value was consistent with a distance of 17.9 Å determined by molecular modeling of U‐70714E to a human renin 3‐D structure (developed from known homologous aspartyl protease inhibitor X‐ray crystallographic data) followed by simulation of the solution phase conformation of the peptide. An extended backbone secondary structure of U‐70714E is suggested from these studies and the relationship(s) of structure‐conformation to structure‐activity was explored by analysis of several congeners

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00003.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

A lectin fromEuphorbia nivuliaBuch. Ham. latex was purified by affinity chromatography on galactose‐Sepharose‐6B.Euphorbia nivulialatex (ENL‐L) was resolved into four lectin fractions on CM‐Sephadex C‐50 column. All the four fractionated lectins were found to be homogeneous. One of the major fractionated lectins (ENL‐L‐IV) was further characterised. ENL‐L‐IV shows a single band on PAGE at pH 4.5 and SDS‐PAGE. Both ENL‐L and ENL‐L‐IV are glycoproleins containing 13.6% and 9% of carbohydrates respectively. ENL‐L has a molecular weight of 45 700 and has two subunits with Mrof 19 000 and 22 800 and a sedimentation coefficient of 4S. ENL‐L‐IV has a molecular weight of 44 000 and appears to be a dimer with subunits of Mrof 22 000. Ultracentrifugation studies showed that it has a Mrof 29 000 and a sedimentation coefficient of 4.8S. Both ENL‐L and ENL‐L‐IV are galactose specific and are also inhibited by galactose derivatives and its oligosaccharides. with increased β‐anomeric specificity. They are found to be mitogenic against human lymphocytes and blood group non‐specific. ENL‐L‐IV was found to be immunologically identical

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00004.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The synthesis of a 37‐peptide fragment derived from the carboxyl terminal of the β‐subunit of baboon chorionic gonadotropin has been accomplished by the continuous flow Fmoc‐polyamide solid phase method. The use ofN′‐fluorenylmethoxy‐carbonyl‐glutamine with its sidechain protected by the 4.4′‐dimethoxybenzhydryl group enabled successful incorporation of this residue onto a hydroxymethyl linkage agent without appa

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00005.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

N‐benzyloxycarbonyl‐l‐homoglutamine was studied to answer the question whether or not there is any tendency for the dehydration of the δ‐carboxamide group during activation and coupling. Only a minor conversion to nitrile by‐products was found in the activation of the α‐carboxyl group and formation of peptide bond with the help of dicyclohexylcarbodiimide. Addition ofN‐hydroxybenzotriazole to the reacting mixture eliminates the side chain dehydration reaction. The dehydration reaction is also overcome by protection of the side chain carboxamide with the benzyloxycarbonylcarbam

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00006.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The synthesis of the tripeptided‐Phe‐Pro‐Arg with the nitrite group instead of the carboxylgroup is described. Initially, the corresponding peptide amide was synthesized by conventional methods in solution using Boc and Fmoc as the protecting group ford‐Phe. The dehydration in order to create the nitrite moiety was achieved by treating the peptide amide with phosphorus oxichloride or trifluoroacetic anhydride. Best results were obtained by the use of phosphorus oxichloride in pyridine as the solvent in the presence of imidazole. After deprotection of theN‐terminal amino acid the crude product was purified by chromatography on Butyl‐Fractogel® HW‐40 (S). The purity of the final product was checked on a RP18 phase by hplc. The existence of the nitrite group was demonstrated by i.r. and13C‐n.m.r. spectra. The peptide nitrite exhibited a strong inhibition of thrombin compared to the

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00007.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Reduction and carbamidomethylation of two of the three disulfide bridges of ovine placental lactogen was accomplished by the use of 20‐fold molar excess of dithiothreitol over protein disulfide content. The derivative retained its binding capacity to somatogenic as well as lactogenic rat liver receptors, although the latter was somewhat diminished. The two disulfide bonds exposed to the reducing agent are those located near the carboxy‐ and amino‐terminus. while the larger loop remained intact after reduction. This behaviour is similar to that of bovine growth hormone, where the larger loop was also more resistant to redu

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00008.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

An X‐ray diffraction study has been carried out on single crystals of two symmetrical ureines (N,N′‐diiopropylurea and the familiarN,N′‐dicyclohexylurea) and one unsymmetrical ureine (N‐tert.‐butyl.N′‐methylurea). The presence/absence of intermolecular H‐bonds in the crystal state has been compared to the situation assessed in solution by1H n.m.r. It was shown by i.r. absorption that soluble ureines may disrupt intermolecular (peptide)N—H‐ O=C(peptide) H‐bonds in methylene chloride, a point of practical interest, particularly in soli

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00009.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The BOP reagent [benzotriazol‐l‐yl‐oxy‐tris‐(dimethylamino)phosphonium hexafluorophosphate] introduced by Castroet al. [Tetrahedron Lett.(1975) 14, 1219–1222] is ideally suited for solid phase peptide synthesis. The rate of coupling using BOP compared favorably to DCC and other methods of activation including the symmetrical anhydride and DCC/HOBt procedures. BOP couplings using the solid phase procedure proceeded more rapidly and to a greater degree of completion for peptide bond formations that were previously determined to be very slow using the conventional DCC method. Stepwise solid phase peptide synthesis using BOP was successfully utilized for the preparation of the (22–29) and (13–29) fragments of [Ala15]‐GRF(1–29)‐NH2. Single couplings with 3 equiv. BOP and Boc‐amino acids and 5.3 equiv. of diisopropylethylamine in DMF were used for each cycle. The yields of the fragments were superior and the purities comparable using the BOP procedure (single couplings) to those observed using multiple couplingsviathe DCC coupling method. A total synthesis of [Ala15]‐GRF(1–29)‐NH2was also carried out using the BOP procedure (single couplings and 3 equiv. BOP and Boc‐amino acids and 5.3 equiv. diisopropylethylamine in DMF for each cycle). Multiple couplings were only required for Boc‐Asn‐OH due to the proposed formation of Boc‐aminosuccinimide during activation. The resultant GRF(1–29) analog was comparable to a control prepared with multiple DCC couplings under optimized conditions. In a parallel study, unprotected Boc‐(hydroxy)‐amino acids were successfully coupled with the BOP reagent. However, the number of coupling cycles after the introduction of unprotected hydroxy‐amino acid must be minimal (<10). The use of the BOP reagent with unprotected Tyr in solid phase p

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1988.tb00010.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY