摘要:

Five subfractions were isolated on DEAE‐cellulose from samples of a commercially available human transferrin preparation and their carbohydrate composition was analysed. Hexosamine, galactose and total hexose were determined in four subfractions and sialic acid in all five.The data obtained indicate that the excess number of electrophoretic bands observed in transferrin from this source is due to the loss of carbohydrates which only affects sialic acid and none of the other sugar types. The availability of the penultimate galactose residues as the terminal residues in the subfractions deficient in sialic acid was also confirmed by a biological test utilizing the rat liver.The reason for the gradual loss of sialic acid from transferrin is unknown. Freezing‐thawing and lyophilization did not detectably affect the sialic acid content of purified transferrin. However, free sialic acid did appear in some preparations on storage.It is concluded that similar changes in the carbohydrate composition of other plasma glycoproteins before, during, or after purification can be expected to exert an adverse effect on their usefulness as metabolic trac

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03487.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

A relatively easy synthetic method is reported for the production of the immunoadjuvant glycopeptide, N‐acetyl‐muramyl‐L‐alanyl‐D‐isoglutamine (MDP). Most of the details in this method were also applied to the preparation of some analogs, that were synthesized in order to study structure‐activity

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03488.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Aminopeptidase I is a membrane‐bound metalloenzyme isolated fromB.stearothermophilus which is thermostable and requires Co2+for activity. The Co, Zn, and metal‐free enzyme were titrated with ANS,* and cooperative binding was noted with the active Co enzyme but not with the Zn (5% active) or apo (inactive) enzymes. There are a number of sites for ANS on each of the three enzyme forms and the agreement between the association constants of the Zn enzyme (identical and independent sites) and the non‐cooperative sites of the Co enzyme suggest that these sites are intrinsically similar. However, binding to the first of these sites in the Co enzyme triggers a cooperative binding of a second molecule of ANS, and this cooperative binding is related to a concomitant decrease in enzymatic activity. The correspondence can be shown by comparison of the inhibition constant for the hydrolysis of Gly‐Leu‐Tyr (Ki‐1= 13,300 cm3/mmol) and the association constant for the cooperating site (12, 500 cm3/mmol). The significance of these observations is discussed in terms of the nature of the binding sites and the possible consequences of the interactions on the regulation of aminopeptidase

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03489.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

An alternative synthesis of [7‐(thiazolidine‐4‐carboxylic acid)]‐oxytocin by a 6 + 3 route using a hexapeptide with a preformed disulphide bridge is o

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03490.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

The C‐terminal undecapeptide of ovine prolactin, H‐Leu‐Asn‐Cys‐Arg‐Ile‐Ile‐Try‐Asn‐Asn‐Asn‐Cys‐OH possesses several structural features common to protein proteinase inhibitors, yet has no inhibitor properties. The undecapeptide is completely hydrolysed by trypsin (Arg‐Ile bond) and by chymotrypsin (Tyr‐Asn bond), with a proteolytic coefficient of approximately 3,000 M‐1sec‐1and 240 M‐1sec‐1respectively. On the basis of these results, a consideration of entropy, and studies by other workers, we agree with the view of Nishinoet al.that the best models for small synthetic peptides with inhibitor properties would be those naturally‐occurring inhibitors whose reactive site is

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03491.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

An analysis of 11 crystal structures of cyclic dipeptides so far reported in the literature is made, with main reference to the internal parameters of these molecules. Preferred conformations of the side chains of cyclic dipeptides with different α‐amino acid residues have been studied by classical energy calculations. The possible conformations of the DKP ring are also studied. The significance of the non‐bonded interaction in deciding the pathway for conformational change has also been investigated. The agreement between theoretical results and experimental observations is quite good, both with respect to the conformation of these molecules as well as the enthalpy difference as estimated from n.m.r. studies between different confor

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1977.tb03492.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY