摘要:

A biotin‐containing hexapeptide Ac‐Glu‐Ala‐Met‐Bct‐Met‐Met (1) that represents the local biotin‐containing site ofEscherichia coliacetyl‐CoA carboxylase has been prepared by the solid phase method. Peptide1is carboxylated by the biotin carboxylase subunit dimer ofE. coliacetyl‐CoA carboxylase with the following kinetic parameters; Km12 mm, Vmax2.8 μm· min–1. These compare with the parameters for biotin of Km214 mmand Vmax28 μm· min–1. Hence, the overall reactivity (Vmax/Km) of1is 1.8 times greater than that of free biotin. When all methionines in1are replaced by alanine, the resulting peptide (2) retains a similar binding ability but with a much decreased Vmax. It was also found that peptide3, which carries anN‐benzyloxy carbonyllysine in place of biocytin in1, decrea

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03127.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Removal of thetert.‐butyloxycarbonyl group by trifluoroacetic acid in the presence of benzyloxycarbonyl groups, benzyl esters and benzyl ethers is rendered more selective by dilution with acetic acid. Trifluoroacetic acid‐acetic acid mixtures, however, cause acetylation of hydroxyl groups and also some formation oftert.‐butyl esters at free carboxyls. Hence, such mixtures are useful only for the deprotection of intermediates in which the hydroxyl and carboxyl groups are fully blocked. A search for a diluent without such inherent limitation led to the application of a mixture of phenol andp‐cresol. Dilution of trifluoroacetic acid with phenols both improved the selectivity in the removal of thetert.‐butyloxycarbonyl group and suppressed the alkylation of amino acid side chains as well. A 4:3:3 mixture of trifluoroacetic acid, phenol andp‐cresol was found useful in the practical execution of partial d

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03128.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

beta‐Lactoglobulin was modified to various degrees with maltose or beta‐cyclodextrin using the cyclic carbonate method and with glucosamine or glucosamineoctaose using the carbodiimide method. Up to 65% of the amino or the carboxyl groups of b‐LG were glycosylated using the two methods, respectively. Up to 32 maltose residues were coupled to b‐LG using the cyclic carbonate method while up to 16.6 glucosamine residues were coupled to b‐LG using the carbodiimide method. This resulted because more than one disaccharide was attached to each group of b‐LG that was modified. Even so, the coupling efficiency of the active compound was higher for the carbodiimide derivative than for the cyclic carbonate derivative. The electrophoretic analyses of the glycosylated proteins indicated that a heterogeneous population of protein molecules was formed during modification. The electrophoretic mobility of maltosyl‐beta‐lactoglobulin derivatives was essentially unchanged while the mobility of glucosaminyl‐beta‐lactoglobulin derivatives decreased as the extent of modification increased. The glycosylated proteins were suitable for studying their structural and fu

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03129.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The Grignard reagents of 2‐(2‐bromoethyl)‐1,3‐dioxane and 2‐(2‐bromoethyl)‐1,3‐dioxolane readily reacted with the 2‐thiopyridyl ester ofN‐triphenylmethyl‐l‐leucine to give the ketone adducts 2‐[3‐oxo‐4(S)‐(triphenylmethyl) amino‐6‐methylheptyl]‐1,3‐dioxane (8a) and 2‐[3‐oxo‐4(S)‐(triphenylmethyl) amino‐6‐methylheptyl]‐1,3‐dioxolane (8b) in near quantitative yield. When 1 equiv. of the Grignard reagent of 2‐(2‐bromoethyl)‐1,3 dioxane was used, the desired ketone adduct8awas formed slowly but quantitatively. In contrast, when 2 equiv. of the Grignard reagent were used, the formation of ketone8awas instantaneous. The triphenylmethyl protecting group was easily removed from8ausing dilute acid to give the amino ketone 2‐[3‐oxo‐4(S)‐amino‐6‐methylheptyl]‐1,3‐dioxane oxalate salt (9). This material served as a useful intermediate in the synthesis of the ketom

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03130.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Specific carbonyl enrichment with17O of amino acid OMe esters by up to 103times over natural abundance was affected by treating [17O]‐α‐COOH amino acids with SOCl2in MeOH. Carbonyl‐[17O]‐Gly‐NH2, Gly‐NHCH3and Gly‐N(CH3)2were obtained from [17O]‐Gly‐OMe by (methyl)aminolysis with NH3, CH3NH2and (CH3)2NH gases respectively. Peptide [17O]‐carboxamides were prepared by (methyl)aminolysis of Z‐Pro‐Leu‐[17O]‐Gly‐OMe followed by catalytic hydrogenation to remove the Z group.17O chemical shifts of amino acid and peptide carboxamides in H2O, MeOH, CH3CN and DMSO were 260–324 p.p.m. downfield relative to H2O, depending on α‐NH2ionization, substitution on both amino groups and solvent H bonding, primarily to amide oxygen. Introduction of an amide‐N methyl group usually caused upfield shifts (approx. – 10 p.p.m.), attributed to elimination of one NH bond, while a second N methylation had the opposite effect. Amino acid and peptide OMe ester carbonyl‐[17O] resonances appeared 326–359 p.p.m. downfield relative to H2O reflecting on side chain interactions, state of α‐NH2ionization and H‐bonding with the solvent. Effective rotational correlation times for glycine and peptide carboxamide‐[17O], calculated from T2relaxation data, were of similar magnitude to values derived from solution properties and depe

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03131.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

We have used energy minimization and harmonic analysis to study the structural and thermodynamic changes which occur upon the binding of lithium ions to the cyclic pentapeptide,cyclo‐(Gly‐L‐Pro‐Gly‐D‐Ala‐L‐Pro) (GPGAP). A number of theoretically stable vacuum configurations of uncomplexed GPGAP were found, one of which is very close to the crystal conformation determined by X‐ray diffraction. Stable complexes with lithium were found where the ion binds to the carbonyl oxygen atoms of three residues. Detailed conformational information is presented for both the uncomplexed and the complexed peptide, along with an analysis of the atomic interactions which stabilize the various pept

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03132.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The cyclic partial retro‐inverso modified enkephalins, H‐Tyr‐cyclo[‐D‐Glu‐Gly‐gPhe‐D‐Leu‐] (I), H‐Tyr‐cyclo[‐D‐A2bu‐Gly‐gPhe‐R&S‐mLeu‐] (IIf, IIs), and H‐Tyr‐cyclo[‐D‐Glu‐Gly‐Phe‐gLeu‐] (III), have been synthesized by solution methodology. In a like manner, their corresponding acyclic analogsIa‐IIIacontaining D‐Ala2have also been prepared.Gem‐diaminoalkyl residues were generated by conversion of Boc‐dipeptide carboxamide to the correspondinggem‐diaminoalkyl “dipeptide” salt using [bis(trifluoroacetoxy)iodo] benzene. Cyclizations were achieved at high

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03133.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

We have prepared several α‐melanotropin (α‐MSH) analogues with tyrosine substituted for methionine at the 4‐position and determined their melanotropic activities on the frog (Rana pipiens), lizard (Anolis carolinensis) and S‐91 (Cloudman) mouse melanoma adenylate cyclase bioassays. The potencies of Ac‐[Tyr4]‐α‐MSH4–10‐NH2and Ac‐[Tyr4]‐α‐MSH4–11‐NH2were compared with α‐MSH and with their corresponding methionine and norleucine substituted analogues. The Tyr‐4 analogues were found to be less active than the Nle‐4 analogues on both the frog and lizard assays. Ac‐[Tyr4]‐α‐MSH4–10‐NH2was found to be less active than Ac‐[Tyr4]‐α‐MSH4–11‐NH2on the lizard bioassay, but more active than the longer fragment on the frog skin assay. Ac‐[Tyr4]‐α‐MSH4–10‐NH2exhibited extremely prolonged biological activity on frog skin, but not on lizard skin, while the melanotropic activity of Ac‐[Tyr4]‐α‐MSH4–11‐NH2was rapidly reversed on both assay systems. The increased potency of Ac‐[Tyr4]‐α‐MSH4–10‐NH2over Ac‐[Tyr4]‐α‐MSH4–11‐NH2on frog melanocytes may be related to the fact that the shorter 4–10 analogue exhibits prolonged biological activity. Interestingly, it was found that both Tyr‐4 analogues were partial agonists on the mouse melanoma adenylate cyclase bioassay, and stimulated the enzyme to only about 50% of the maximal activity of α‐MSH. We reported previously that replacement of L‐Phe‐7 by its D‐enantiomer in [Nle4]‐α‐MSH and its Nle‐4 containing analogues resulted in peptides with increased potency and in some instances prolonged activity. Similarly, incorporation of D‐Phe‐7 into Tyr‐4 containing melanotropin fragments produced analogues Ac‐[Tyr4, D‐Phe7]‐αMSH4–10‐NH2and Ac‐[Tyr4, D‐Phe7]‐α‐MSH4–11‐NH2, which also exhibited greatly increased biological activity in all three assay systems. Both of these analogues were also found to have prolonged activity in the frog skin bioassay but little or no prolonged activity in the lizard skin bioassay. These two analogues turned out to be full agonists in the mouse melanoma adenylate cyclase bioassay and were equipotent to α‐MSH. These results demonstrate that substitution of tyrosine for methionine at position‐4 dramatically affects the potency and prolonged activity of these melanotropin analogues and the melanotropic a

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03134.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

A peptide isolated from calf spleen has been identified as thymosin α1. The isolation involved defatting of the desiccated glands with acetone, extraction of the acetone power with pyridine acetate pH 5.5, heat denaturation, reverse phase chromatography on an RP‐8 column, anion exchange chromatography on a Partisil SAX column and, finally, reverse phase purification on a μBondapak C18column. The identification was based on: 1) amino acid analysis; 2) thermolysin digest; and 3) retention time in two different HPLC systems. The amount isolated from the spleen was 10–20% of that isolated from calf thymus g

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03135.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Human growth hormone (HGH) was extracted from acromegalic pituitary tumors at pH 10.5 and precipitated with ammonium sulfate at 20–40% saturation. It was purified on a Sephadex G‐100 column to yield monomeric HGH. The tumor‐HGH was indistinguishable from the authentic one in polyacrylamide gel electrophoresis at pH 8.3 or in the presence of sodium dodecyl sulfate, high‐performance liquid chromatography, radioimmunoassay, peptide map, amino acid composition andN‐terminal partial amino acid sequence. The tumor‐HGH is active in the tibia assay and body weight gain test in hypophysectomized rats with comparable potency to that of the authe

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1984.tb03136.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY