ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1974.tb02396.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1974.tb02397.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The conformations in solution of a series of monodisperse L‐valine oligomers having the general formula BOC(L‐Val)nOMe* (n = 2–7) were investigated using polarimetry, UV absorption, and CD. We examined these oligopeptides in TFE, HFIP, HFA, and mixed fluoroalcoholic‐water media, and compared the results with those obtained in the analogous L‐isoleucine series, which in part have been previously reported. The β‐associated structure stands out clearly at the heptamer in the two β‐branched linear homo‐oligopeptide series in TFE. In HFIP and HFA, however, the oligomers exist essentially in an unordered conformation. Also, we demonstrated that addition of water to solutions of these oligopeptides in the fluoroalcohols forces the higher oligomers to assume β‐type associated structures. The aggregates could be disrupted by dilution or in

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1974.tb02398.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The norphalloin analogues with glycine and L‐valine instead of L‐alanine in position 1, (II and III), with D‐α‐aminobutyric acid instead of D‐threonine in position 2 (IV), and with β‐trideutero‐L‐alanine instead of L‐alanine in position 5 (β‐D3‐I), have been synthesized according to Chart I, mainly using the mixed anhydride method. For the final cyclization step to III the p‐nitrophenylester method was employed. Analogue IV showed toxicity in the white mouse with doses<5 mg per kg body weight, whereas II and III were nontoxic. The deuterated norphalloin analogue proved by p.m.r. measurement that in fact the methyl group of alanyl residue no.5 is located above the indole nucleus, as suggested i

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1974.tb02399.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The general strategy for the synthesis, by conventional procedure, of the entire sequence of porcine pancreatic secretory trypsin inhibitor II (Kazal) is discussed. Six suitably protected subunits, spanning the entire amino acid sequence of the inhibitor, have been synthetized and fully characterized.

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1974.tb02400.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

[Tyr120]‐RNase 111–124 and [Ala120]‐RNase 111–124 were synthesized and purified to chromatographic and electrophoretic homogeneity. The peptides were mixed noncovalently with RNase 1–118 that had been prepared by enzymatic degradation of native bovine pancreatic ribonuclease A. The activities of the resulting complexes were compared with that of the corresponding complex containing the natural peptide sequence, [Phe120]‐RNase 111–124, and with native RNase, using yeast RNA, C>p and U>p as substrates. The Tyr120and Phe120complexes were equally active against RNA and C>p, but the Tyr120complex was twice as active as the Phe120complex against U>p. The complex with alanine at position 120 was only 1% as active toward C>p as the complex containing phenylalanine. The prediction that giraffe RNase, which contains tyrosine at position 120, would be relatively more active toward U>p than C>p compared with bovine RNase

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1974.tb02401.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

When a homogenate of beef pancreas prepared at neutral pH is assayed for RNase activities at pH 4.5 and at pH 7.5, the specific activity at the acid pH is more than half that at neutral pH. Yet the procedures normally employed for the isolation of the well‐characterized RNase A from the pancreas yield an enzyme that is almost devoid of activity at pH 4.5. Experiments designed to isolate from the pancreas the protein responsible for the RNase activity at acid pH have utilized chromatography and gel filtration under conditions that avoid both the strong acidification and the heat which are common features of the methods for the preparation of RNase A. The purified protein active at pH 4.5 (yield, 10 mg per 100 g of tissue) is also active at pH 7.5. The protein is labile to both strong acid and high temperature and it is this sensitivity that has contributed to its being overlooked during the decades when RNase A has been so thoroughly studied.Acid or heat treatment converts the enzyme active at pH 4.5 to a protein which is currently indistinguishable from RNase A, with as yet no detectable change in amino acid composition. Further research is required to define the small but significant chemical or physical changes which accompany this transformatio

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1974.tb02402.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

In order to describe further the role of the invariant amino acid residue lysine‐7 in the RNase S' system, potential catalytic activities of des‐Lys7‐[Orn10]‐, [Ala7, Orn10]‐, [Lys4, Ala7, Orn1.0]‐S‐peptide and corresponding guanidinated derivatives were studied. New information was obtained about S‐protein binding capacities of the analogs relative to that of unmodified S‐peptide, and about conformation of the corresponding RNase S' analogs by studies on competitive inhibition, difference spectroscopy, difference circular dichroism and thermal transition. Peptides modified in position 7 were no weaker in strength in peptide‐protein noncovalent interaction in the presence of substrate. In the absence of substrate the variously modified S‐peptide analogs were differentiated in their S‐protein affinity. Conformational changes in the geometry of the active site of the reconstituted enzymes, if present, must be smaller than the detection limits of the techniques used. There is strong implication that the change in catalytic efficiency has to be attributed to an alteration or to the position of the charge and that lysine‐7 in the natural enzyme is involved in stabilizing the transition state intermediates during decomposition of the substrate. Further substantiation was provided by substrate inhibition studies as well as 3‐CMP binding measurements, since 3‐CMP binding affinity of RNase S' modified in position 7 was found to be significantly lower

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1974.tb02403.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

The synthesis by fragment condensation of a nonatricontapeptide corresponding to positions 66–104 of the proposed amino acid sequence of the enzyme ribonuclease T1is described. It is shown that complex peptides corresponding to the C‐terminal region of the T1enzyme are soluble in 8 M pH 10.7 urea and that purification can be achieved by gel filtration in this sol

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1974.tb02404.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Cysteine is smoothly converted to S‐3‐sulphopropylcysteine by 3‐hydroxypropane‐sulphonic acid γ‐sultone (1,3‐propane sultone) in aqueous propanol at pH 8.3. The reaction is about 12 times slower than with iodoacetate but the selectivity for thiol groups is similar, as judged from model experiments and reactions with proteins. S‐3‐Sulphopropylcysteine is stable to the conditions to total acid hydrolysis and behaves distinctively in electrophoresis and ion‐exchange chromatography. Reduction and alkylation of bovine insulin and human serum albumin (pH 8.3, 50% aqueous propanol) on a preparative or analytical scale gives fully S‐substituted derivatives. The S‐sulphopropylated A and B chains of insulin have been separated by precipitation or ion‐exchange chromatography. The sulphopropyl derivatives have good handling properties and the reaction with propane sultone is suggested as a useful addition to the meth

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1974.tb02405.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY