摘要:

9‐Fluorenylmethoxycarbonyl (Fmoc) amino acids were first used for solid phase peptide synthesis a little more than a decade ago. Since that time, Fmoc solid phase peptide synthesis methodology has been greatly enhanced by the introduction of a variety of solid supports, linkages, and side chain protecting groups, as well as by increased understanding of solvation conditions. These advances have led to many impressive syntheses, such as those of biologically active and isotopically labeled peptides and small proteins. The great variety of conditions under which Fmoc solid phase peptide synthesis may be carried out represents a truly “orthogonal” scheme, and thus offers many unique opportunities for bioorganic chem

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00939.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The orthogonal synthesis ofNx‐Boc‐L‐aspartic acid‐γ‐fluorenylmethyl ester andNα‐Boc‐L‐glutamic acid‐δ‐fluorenylmethyl ester is reported. This is a four‐step synthesis that relies on the selective esterification of the side‐chain carboxyl groups onNx‐CBZ‐l‐aspartic acid andNα‐CBZ‐l‐glutamic acid. Such selectivity is accomplished by initially protecting the a‐carboxyl group through the formation of the corresponding 5‐oxo‐4‐oxazolidinone ring. Following side‐chain esterification, the α‐carboxyl and α‐amino groups are deprotected with acidolysis. Finally, the α‐amino group is reprotected with the t‐butyl‐oxycarbonyl (Boc) group. Thus aspartic acid and glutamic acid have their side‐chain carboxyl groups protected with the base‐labile fluorenylmethyl ester (OFm) and their α‐amino groups protected with the acid‐labile Boc group. These residues, when used in conjunction withNx‐Boc‐Nε‐Fmoc‐l‐lysine, are important in the formation of side‐chain t

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00940.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Enzyme‐catalyzed synthesis of two polypeptide fragments, one of which is obtained by chemical synthesis, in the presence of proteolytic enzymes and in aqueous organic solvents constitutes a convenient procedure for the synthesis of proteins and their analogs. This novel semisynthetic procedure was investigated for preparingCOOH‐terminal fragments of the metallo‐protease thermolysin. Fragment 205–316, obtained by autolysis of the protein in the presence of EDTA, was first cleaved selectively withStaphylococcus aureusV8 protease at the level of the single Glu302residue into fragments 205–302 and 303–316. Upon incubation for 2–5 days of fragment 205–302 with a 5–fold excess of peptide 303–316, prepared by solid phase synthesis, with V8‐protease in 0.1M ammonium acetate, pH6.0, containing 50% glycerol as organic cosolvent, enzyme‐catalyzed reformation of the peptide bond was achieved in yields up to ñ90% (based on fragment 205–302). The same procedure was used to prepare also the thermolysin fragments 205–315 and 205–311 by enzymatic coupling of fragment 205–302 to peptide 303–315 or 303–311, these last prepared by proteolytic digestion of the synthetic peptide 303–316. This procedure of semisynthesis opens up an approach for the site‐directed modification of the tetrahelicalCOOH‐terminal fragment 205–316 of thermolysin at the level of its helical segment encompassing residues 301–312 in the native, intact protein. Such analogs will be useful for examining structure‐folding‐stability relationships in this fold

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00941.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Based on structure‐activity relationships of the potent α‐MSH agonist, Ac‐Nle4‐Asp5‐His6‐d‐Phe7‐Arg8‐Trp9‐Lys10‐NH2, several analogs of the general formula Ac‐Nle4‐Asp5‐Waa6‐Xaa7‐Yaa8‐Zaa9‐Lys10‐NH2were synthesized and tested on frog and lizard skin bioassays for their possible inhibitory actions against α‐MSH on melanocyte stimulation. When Waa6= Trp, Xaa7= D‐Phe, Yaa8= Nle and Zaa = Trp, a highly potent α‐MSH antagonist, Ac‐Nle‐Asp‐Trp‐d‐Phe‐Nle‐Trp‐Lys‐NH., with selectivity on the frog skin α‐MSH receptor system (PA2= 8.4) was obtained. However, several modifications in the amino acid sequence of the peptide resulted in a complete loss of antagonistic activity and a recovery of very weak agonistic action. The following changes in the amino acid sequence of the peptide were examined; His ord‐Trp for Waa,l‐Phe for Xaa, Arg, Ala or Pro for Yaa, andd‐TV for Zaa. All resulted in full agonists with no antagonistic activity. In addition, lactam cyclization between the Asp5and Lys10side chains in the antagonist gave a full agonist and a complete loss of antagonistic activity. Efforts to develop a rational approach for the design of selec

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00942.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The conformational free energy of armadillo metmyoglobin was examined over a pH range of 4.4–8.0 and a guanidinium chloride concentration of 0–2.3 M. For isothermal unfolding at 25′ essentially the same value was obtained for the conformational free energy from all the data: 27 ± 2 kJ/mol. These data suggest that the armadillo has the least stable metmyoglobin of any mammal thus far examined. The cooperativity of the unfolding with respect to denaturant is considerably less than for other mammalian myoglobins. On unfolding only three to four side chains with a pKAof 6 in the unfolded protein are protonated instead of the six found for horse and sperm whale myog

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00943.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A number of dodecapeptides with the sequence YIIKGVFWDPAC were synthesized using solid phase peptide synthesis. The purity of the crude cleavage product was found to be directly related to the cysteine protecting group and the conditions employed for cleavage of the peptide from the resin. When 4‐methyl‐benzyl cysteine was used, complete deprotection was only achieved with low‐high HF conditions at temperatures of 10°‐25°, whereas milder conditions could be used for dodecapeptides containing ethyl cysteine or acetamidomethyl cysteine. In several syntheses the biological activity of the crude cleavage product greatly exceeded the biological activity of a purified major peptide component. The high activity found in the crude cleavage peptide was probably due to minor peptide side products in which the cysteine sulfur was alkylated by hydrophobic species during HF treatment. Two dodecapeptides, YIIKGV‐FWDPAC and YIIKGFWDPAC(Ethyl), had significant α‐factor activity againstMATα strains ofSaccharomyces cerevisiae.These peptides represent the first synthetic analogs with α

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00944.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A convergent synthesis of the peptide [1‐(β‐mercapto‐β,β‐cyclopentamethylenepropionic acid)‐2‐(O‐ethyl‐d‐tyrosine)‐4‐valine‐9‐desglycine]arginine vasopressin (1), based on the classical solution phase method, was developed. The molecule is assembled by a 3 + 4 coupling via the amide method; then the disulfide bridge is installed by iodine treatment of the bis‐acetamidomethyl protected thiols, and the terminal arginine amide added by a 7 + 1 coupling. The method (see Scheme 1) has been used to prepare gram quantities of 1 in more than 98% purity and in 13% yield (based on tetrapeptide intermediate 13) after a single stage purification. The method appears to be particularly suitable for the large scale preparation of 1 and other vasopressin congeners. A novel, albeit low level, transfer of acetamidomethyl group from the sulfur of cysteine to the asparagine amide side‐chain was detected following hydrogen chloride treatment

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00945.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

A precipitin effect has been observed with mixtures of cerebroside sulfate and the neuropeptide substance P. This phenomenon is attributed to multivalency of the lipid due to its existence in micellar form, and to bivalency of substance P. One of those neuropeptide sites is almost certainly the basic residue(s) located at theN‐terminal of substance P, whereas the hydrophobic residues at theC‐terminus are suggested as candidates for the other site on the basis of turbidimetric, circular dichroic, and fluorometric studies. An intrinsic asSociation constant of 3.6 × 104M‐1has been obtained from the cerebroside sulfate concentration asSociated with maximal turbidity of mixtures containing a fixed concentration of the neurop

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00946.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The title compound 3, an amatoxin analogue containingl‐α‐aminobutyric acid instead ofl‐asparagine in position 1, as in natural toad stool peptides, has been synthesized. It does not inhibit the eukaryotic DNA‐dependent RNA polymerase form II (or B) in concentrations up to 10‐4M, whereas 50% inhibition is exerted in M solution by the corresponding Asn‐analogue S‐deoxo‐Ile3‐amaninamide 2. The striking difference seems to be due to a relatively small variation of the conformation recognized by sensitive NMR spe

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00947.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Six peptides with amino acid sequences of human histocompatibility Class II membrane glycoproteins were synthesized by conventional solution methods. Five peptides were prepared by stepwise procedures from the carboxyterminus. The sixth was synthesized by fragment condensation (5 + 10 coupling). Antibodies to synthetic peptides were then used to locate exposed and buried regions in the membrane glycoproteins.

ISSN:0367-8377    

DOI:10.1111/j.1399-3011.1990.tb00948.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY