bluuebunny/crossref_metadata_2025 huggingface dataset:
Sulfur protection with the 3‐nitro‐2‐pyridinesulfenyl group in solid‐phase peptide synthesis
Authors: RIDGE RICHARD J. , MATSUEDA GARY R. , HABER EDGAR , MATSUEDA REI
Published: August 2010

The 3‐nitro‐2‐pyridinesulfenyl(Npys) group has been used successfully for side chain protection of cysteine during the stepwise solid‐phase synthesis of Lys8‐vasopressin(LVP) on benzhydrylamine resin. The versatility and limitations of this group have been evaluated by comparison of this synthesis with a parallel control synthesis using the 3,4‐dimethylbenzyl(DMB) group and with a synthesis utilizing a combination of both groups. The Npys group was found to be stable to TFA as reported and, in addition, was found to be stable to HF:anisole(9:1) for 45 min at 0°, but not when thiol was present in either reagent. Furthermore, compatibility of the Npys group with the Boc‐benzyl synthetic tactic in solid‐phase peptide synthesis was demonstrated. LVP with full biological activity was obtained after purification by gel filtration and reverse‐phase HPLC.
Internal fluctuations in globular proteins
Authors: PONNUSWAMY P.K. , BHASKARAN R.
Published: August 2010

An attempt was made to study the dynamics and hence the fluctuations in globular proteins treating them as prolate and oblate spheroidal bodies. The fluctuations were obtained by solving the dynamical differential equation of motion derived from the elastic stress‐strain relations. The results provide information on the nature of variation of the displacement of the atoms due to fluctuations in the distance from the centroid of the protein.
β‐Endorphin: analgesic and receptor binding activity of non‐mammalian homologs
Authors: HAMMONDS R. GLENN , NICOLAS PIERRE , LI CHOH HAO
Published: August 2010

Analgesic potencies of turkey, ostrich and des‐acetyl salmon β‐endorphins have been measured in the tail‐flick test and binding affinities determined by radioreceptor assay. The duration of analgesia and the slope of the dose‐response curves generated by these peptides are similar to those elicited by mammalian β‐endorphins. This suggests that they actin vivoandin vitroon the same population of opiate receptors. The ratio of binding to analgesic potencies observed for these peptides varies nearly sixfold. Structure‐activity analysis suggests that a basic side‐chain at position 9 is required in order to produce a high opiate activity bothin vivoandin vitro.A reexamination of the biological activities of camel β‐endorphin shows that the analgesic potency and binding affinity of this peptide are respectively 1.7 and 2.7 times higher than human β‐endorphin. His‐27 and/or Gln‐31 may contribute to this increased potency. The dissociation of radioreceptor binding affinity from analgesic potency in these naturally occurring β‐endorphin homologs suggests that either the conditions under which the binding assay is performed mask the true binding potency in the brain or that, once bound to the appropriate receptor, these homologs do not possess equal ability to produce biological effects.
Synthesis and biological activity of some new 3,6‐dinitro‐1:8‐naphthaloyl‐and 3,6‐diamino‐1:8‐naphthaloylamino acids and dipeptide derivatives
Authors: EL‐NAGGAR A.M. , ZAHER M.R. , SALEM A.A.
Published: August 2010

Synthesis of a series of 3,6‐dinitro‐1:8‐naphthaloylamino acids (II‐IX) and some of their corresponding methyl esters (X‐XVI) and 3,6‐diamino‐1:8‐naphthaloylamino acid derivatives (XXIX‐XXXVI) is described. Coupling of 3,6‐dinitro‐1:8‐naphthaloylamino acids with amino acid methyl ester hydrochlorides in dioxane‐DMF‐Et3N medium using DCC method furnishes the desired 3,6‐dinitro‐1:8‐naphthaloyldipeptide methyl esters (XVII‐XXVIII). Most of the synthesized 3,6‐dinitro‐1:8‐naphthaloylamino acids, esters and dipeptide derivatives (compounds III‐VI, XI‐XV, XVII, XIX‐XXI, XXIII and XXV) and 3,6‐diamino‐1:8‐naphthaloylamino acid derivatives (XXIX‐XXXV) were found to be active against a number of microorganisms.
Peptide‐urea interaction
Authors: CESÀRO ATTILIO , RUSSO ELIO , BARONE GUIDO
Published: August 2010

The excess enthalpies of the ternary aqueous solutions containing urea and the glycyl‐glycine, glycyl‐L‐alanine, L‐alanyl‐L‐alanine and sarcosyl‐sarcosine diketopiperazines respectively have been determined. A weak but favourable enthalpic contribution to the interaction between these solutes is found. The difference between “strong” and “weak” interactions in aqueous solutions of non‐electrolytes is stressed and the role of water in the weak, non‐specific interactions, is discussed. The consequence of the weakness of the urea‐peptide interactions on the binding of urea to the proteins is also briefly discussed.
β‐Endorphin: synthesis and properties of analogs modified in positions 8 and 31
Authors: YAMASHIRO DONALD , NICOLAS PIERRE , LI CHOH HAO
Published: August 2010

Four analogs of human β‐endorphin (βh‐EP) were synthesized by the solid‐phase method: [Gln8.31]‐βh‐EP(I), [Arg8, Gln31] ‐βh‐EP(II), [Ala8, Gln31] ‐βh‐EP (III), and [Val8, Gln31]‐βh‐EP(IV). Radioreceptor binding assay with use of tritiated βh‐EP as primary ligand gave relative potencies as follows: βh‐EP, 100; I, 200; II, 150; III, 150; IV, 120. Relative potencies in an analgesic assay were: βh‐EP, 100; 1,236; II, 254;III, 116; IV, 121. The side‐chain of Glu‐8 in βh‐EP can be replaced by a variety of structures without diminishing biological activity.
Physicochemical studies of dinitrophenylated bovine serum albumin
Authors: KESSLER KURT F. , BARTH ROLF F. , WONG KIN‐PING
Published: August 2010

The structural changes of bovine serum albumin (BSA) as a function of dini‐trophenylation have been studied by disc gel electrophoresis, sedimentation velocity analyses, and circular dichroism. These experiments were designed to understand the molecular bases for the change in immunogenicity and antigenicity of BSA upon dinitrophenylation. Dinitrophenylated BSA tends to aggregate to dimers and higher aggregates. A concomitant large change in electrophoretic mobility was also observed. Circular dichroism studies reveal a large decrease in the α‐helical structure of the BSA molecule.
Synthesis of human corticotropinyl‐thiolglycine and its specific conjugation to bovine serum albumin
Authors: BLAKE JAMES , HAGMAN JAMES , RAMACHANDRAN J.
Published: August 2010

Human corticotropin containing a thiolglycine residue at the carboxyl terminal (I) was synthesized by the solid‐phase method. The citraconyl derivative of peptide I was coupled to either a model tetrapeptide or bovine serum albumin by reaction with silver nitrate/N‐hydroxysuccinimide in water. The extent of reaction with bovine serum albumin was determined by radioimmunoassay, and the peptide‐protein conjugate was shown to possess 12% of the steroidogenic activity of porcine adrenocorticotropin in isolated rat adrenal cells. Peptide I and its conjugate with the model tetrapeptide were fully active in the same system.
Kinetic mechanism of threonyl‐tRNA synthetase from human placenta
Authors: PAN F. , LO K.Y. , PAI S.H. , LEE H.H.
Published: August 2010

Using purified enzyme and homologous tRNA, we have investigated the order of substrate binding and product release for the human placental threonyl‐tRNA synthetase by isotope exchange, initial velocity, dead‐end inhibition and product inhibition studies. The kinetic patterns obtained from these studies are consistent with a unique Bi Uni Uni Bi ping‐pong mechanism. The order of addition of the first two substrates ATP and threonine is random, while the release of products follows an obligatory sequence, with AMP as the last product to dissociate from the enzyme.
Dynorphin in bovine adrenal medulla
Authors: DAY ROBERT , DENIS DANIELLE , BARABE JEAN , ST‐PIERRE SERGE , LEMAIRE SIMON
Published: August 2010

The presence and secretion of immunoreactive dynorphin in bovine adrenal medulla and isolated adrenal chromaffin cells were examined and compared with those of immunoreactive leucine‐enkephalin. Using an antiserum raised against dynorphin‐(1–13), a sensitive and highly specific radioimmunoassay was developed. A nearly intact antigen was required for recognition by the antiserum since it did not react with leucine‐enkephalin and reacted poorly with dynorphin‐(1–12) (cross‐reactivity 0.5%) and other fragments of dynorphin‐(1–13). On the other hand, the antibody used for detection of leucine‐enkephalin did not cross‐react with dynorphin‐(1–13). Adrenal medulla acid extracts contained 195 times more immunoreactive leucine‐enkephalin than dynorphin. However, the concentration of immunoreactive dynorphin in acid extracts of freshly isolated adrenal chromaffin cells was only 1.4 times smaller than that of leucine‐enkephalin. Incubation of the isolated chromaffin cells in the presence of acetylcholine, nicotine, high potassium, but not muscarine, induced a concomitant release of immunoreactive dynorphin (3.5–9% of total cell content) and leucine‐enkephalin (6.5–11.4% of total cell content).
Dehydro‐enkephalins. III. Synthesis and biological activity of [ΔAla2, Leu5]‐enkephalin
Authors: SHIMOHIGASHI YASUYUKI , STAMMER CHARLES H.
Published: August 2010

[ΔAla2, Leu5]‐enkephalin has been prepared and shown to be more active than the parent saturated enkephalin in a binding assay using rat brain membranes and [3H] dihydromorphine as a tracer. In a comparison of potencies against [3H] dihydromorphine and [3H]‐[d‐Ala2,d‐Leu5]‐enkephalin as tracers, [ΔAla2, Leu5]‐enkephalin showed preference for μ opiate receptors, possibly due to the hydrophobicity of the ΔAla2residue. A synthetic tetrapeptide enkephalin [ΔAla2]‐desLeu5‐enkephalin had weak activity and high selectivity for the μ receptors.O‐Acylation of a serine residue in the peptide was achieved by coupling between the peptide and a carboxylic acid using DCC and a catalytic amount of 4‐dimethylaminopyridine.
Weak acid‐catalyzed pyrrolidone carboxylic acid formation from glutamine during solid phase peptide synthesis
Authors: DIMARCHI RICHARD D. , TAM JAMES P. , KENT STEPHEN B.H. , MERRIFIELD R.B.
Published: August 2010

Formation of pyrrolidone carboxylic acid (pyroglutamic acid) residues from amino‐terminal glutaminyl residues in peptides was shown to be catalyzed by weak acids, but not by strong acids. During dicyclohexylcarbodiimide‐mediated coupling reactions the Nα‐protected amino acid reagent accelerated this cyclization and resulted in a significant amount of chain termination. The side reaction could be minimized by accelerating the coupling reaction and simultaneously reducing the time of exposure to weak acids. The most effective procedure was to couple in dimethylformamide with the preformed symmetric anhydride of the amino acid.
Interaction of lead ions with bovine carbonic anhydrase
Authors: MAILER KATHLEEN , CALHOUN LARRY A. , LIVESEY DEREK L.
Published: August 2010

The interaction of lead (Pb2+) ions with apocarbonic anhydrase is studied by u.v. difference spectroscopy. The Pb2+results are compared with those of Zn2+interacting with apocarbonic anhydrase. The results of both metals interacting with apoenzyme are related to the difference spectra of Pb2+and Zn2+with Trp and Tyr model compounds. The interaction of Pb2+with apocarbonic anhydrase containing an acetylated tyrosine residue is examined. Evidence is presented that Pb2+is located in the active site cavity of apocarbonic anhydrase, but displaced from the zinc His ligands, interacting with Tyr 7. An attempt is made to rationalize the metal‐chromophore micro‐environment based on analysis of the 270–295 nm u.v. region of the difference spectra.
Solid phase synthesis of the protected 43–55 tridecapeptide of the heavy chain of myeloma immunoglobin M603, employing cyclohexyl ester protection for glutamic acid
Authors: DIMARCHI RICHARD D. , TAM JAMES P. , MERRIFIELD R.B.
Published: August 2010

A protected tridecapeptide of the sequence Boc‐Lys(2ClZ)‐Arg(Tos)‐Leu‐Glu(OcHex)‐Trp(For)‐Ile‐Ala‐Ala‐Ser(Bzl)‐Arg(Tos)‐Asn‐Lys(2ClZ)‐Gly‐OH, representing residues 43–55 of the variable region of the heavy chain of mouse myeloma protein M603, was synthesized. It was assembled by a stepwise solid phase method designed to give a fully protected peptide in high yield and purity with minimal side reactions. Thus, the peptide chain was attached as an α‐methyl phenacyl ester to a 2‐bromopropionyl‐resin. After the synthesis the protected peptide fragment was obtained in 89% yield by photolytic cleavage from the resin. The peptide was purified by multiple precipitation and column chromatography. It was shown to be homogeneous by reverse phase high pressure liquid chromatography, and it had the correct amino acid composition and sequence. In the course of this work it was shown that tert.‐butyloxycarbonyl‐amino acids caused the formation of significant amounts of pyrrolidone carboxylic acid residues during the coupling reaction when a γ‐benzyl glutamyl residue was NH2‐terminal. Other weak‐acid additives also caused this chain terminating side reaction. The cyclization was markedly suppressed by protection of the glutamyl side chain as a cyclohexyl ester. With this protecting group, no evidence of pyrrolidone carboxylic acid formation could be detected in the tridecapeptide 43–55.
Purification and subunit structure studies of human placental threonyl‐tRNA synthetase
Authors: PAN F. , LEE H.H. , PAI S.H. , LO K.Y.
Published: August 2010

Human threonyl‐tRNA synthetase has been purified from full‐term placenta over 5000‐fold with a 13% overall yield by a combination of affinity chromatographic methods and conventional procedures. The product was apparently homogeneous by the criterion of sodium dodecyl sulfate‐polyacrylamide gel electrophoresis. The purified enzyme catalyzed the esterification of ˜ 3500 nmol L‐threonine to tRNA per min per mg of protein at 37°, corresponding to a molecular activity of ˜ 700/min. The apparent molecular weight of the native enzyme ranged from 210 000 to 220 000 by gel‐filtration on Sephadex G‐200, and was either ˜ 110 000 or 228 000 by sucrose gradient centrifugation for different preparations. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis demonstrated a single band of molecular weight 85 000 or 115 000 for different preparations. These results suggest that human placental threonyl‐tRNA synthetase has a subunit structure of the type α2 with a subunit molecular weight of about 100 000. However, some other molecular forms with lower specific activity were also found to exist under certain conditions.
Conformational changes of bovine plasma albumin prior to the salting‐out of the protein in concentrated salt solution
Authors: Sogami Masaru , Inouye Hiroshi , Nagaoka Shunji , Era SEiichi
Published: August 2010

By working at very low protein concentration (ca. 0.003%), it is possible to measure tryptophyl fluorescence intensity at 350nm (F350) of bovine plasma albumin (BPA) as a function of pH under precipitating conditions (acidic concentrated salt solutions). Under such conditions, distinct changes in F350 were seen before the starting of precipitation of BPA and no further changes in F350 over the precipitating pH range. Comparison of pH‐profiles monitored by F350 with those by solubility in the presence of various salts at various concentrations indicated that the change of solubility is observed after definite changes in conformation of the protein.
Dehydroaspartic acid derivatives*
Authors: Kolasa Teodozyj , Gross Erhard
Published: August 2010

Dipeptides of threo‐ and erythro‐β‐hydroxyaspartic acid were transformed into O‐tosyl derivatives, which on base‐catalyzed elimination gave aminofumaric acid derivatives. The possible mechanism of this process and the spectroscopic properties of the elimination products are discussed.
Studies on the structure of connectin in muscle
Authors: GRUEN L.C. , KING N.L. , KURTH L. , McKENZIE I.J.
Published: August 2010

Enzymic hydrolysis, followed by amino acid analysis, provided no evidence for the presence of e‐(y‐glutamyl) lysine or other isopeptide crosslinks in connectin. Gel electrophoresis in the presence of sodium dodecyl sulphate did not reveal any difference in connectin between normal and lathyritic muscle, indicating that lysyl oxidase does not initiate cross‐link formation in connectin. Although connectin may be covalently crosslinked by some unknown mechanism, the available evidence suggests that the subunit of MW ˜ 900 000 is synthesised as a single polypeptide chain. In developing fetal muscle, myosin heavy chains are apparent some weeks earlier than connectin. This, together with the known susceptibility of connectin to hydrolysis, suggests that connectin exists in an exposed environment rather than as a core to the thick filament.
Experiments on the protection of the thioether in methionine
Authors: BODANSZKY MIKLOS , BEDNAREK MARIA A.
Published: August 2010

The decrease in the solubility of peptides when their methionine residues are replaced by methionine sulfoxides prompted the exploration of an alternative approach to the protection of the thioether in methionine side chains. Alkylation of tert.‐butyloxycarbonyl methionine p‐nitrophenyl ester with methyl p‐toluenesulfonate yielded the crystalline derivative of methionine S‐methyl p‐toluenesulfonate which could be incorporated into peptide chains. Alternatively, methionine S‐methyl p‐toluenesulfonate (Mmt) residues could be generated by the action of methyl p‐toluenesulfonate on methionine containing peptides. The protecting group remained intact under the conditions of aminolysis and ammonolysis commonly used in peptide synthesis, and it was unchanged after the removal of other blocking groups with trifluoroacetic acid or diethylamine. On treatment with hydrobromic acid in acetic acid the toluenesulfonate anion was replaced by bromide ion, while hydrogenation resulted in the decomposition of the modified methionine side chain. In the process of deprotection Mmt residues could be smoothly converted to methionine residues by thiolysis. Thus, the protecting group functioned well in several respects but an increase in solubility (in dimethylformamide) on alkylation was observed only in a part of the peptide derivatives tested. Therefore, the value of the new approach for the protection of the methionine side chain in peptide synthesis remains to be established.
Synthesis of human β‐endorphinyl‐thiolglycine and its use for the preparation of affinity columns of β‐endorphin
Authors: BLAKE JAMES , HINES KATHERINE K. , LI CHOH HAO
Published: August 2010

The peptide human β‐endorphinyl‐thiolglycine (I) has been synthesized by the solid‐phase method. The citraconyl derivative of peptide I was coupled to aminohexyl‐Sepharose by reaction with silver nitrate/N‐hydroxysuccinimide in water. The citraconyl groups were removed in aqueous acetic acid and the resulting resin was used in affinity chromatography for the purification of antisera to β‐lipotropin and β‐endorphin.
Derivatives of S‐9‐fluorenylmethyl‐L‐cysteine
Authors: BODANSZKY MIKLOS , BEDNAREK MARIA A.
Published: August 2010

The 9‐fluorenylmethyl (Fm) group was examined with respect to its potential for blocking the sulfhydryl function. The S‐Fm group is resistant to acids and to catalytic hydrogenation but is cleaved by ammonia in methanol or by organic bases, such as a 20% solution of piperidine in dimethylformamide. Synthesis of N‐tert.‐butyloxycarbonyl‐S‐9‐fluorenylmethyl‐L‐cysteine p‐nitrophenyl ester and of cysteinyl peptides protected with the S‐Fm group are described.
Acid‐labile resin linkage agents for use in solid phase peptide synthesis
Authors: SHEPPARD ROBERT C. , WILLIAMS BRIAN J.
Published: August 2010

Details are given of the preparation of two acid‐labile peptide‐resin linkage agents for use in solid phase peptide synthesis, viz. 4‐hydroxymethylphenoxy‐acetic acid and 3‐methoxy‐4‐hydroxymethylphenoxyacetic acid. The latter is suitable for the preparation of peptide fragments bearing t‐butyl‐based side chain protecting groups.
Statistical and energetic analysis of side‐chain conformations in oligopeptides
Authors: BENEDETTI ETTORE , MORELLI GIANCARLO , NÉMETHY GEORGE , SCHERAGA HAROLD A.
Published: August 2010

The distributions of side‐chain conformations in 258 crystal structures of oligopeptides have been analyzed. The sample contains 321 residues having side chains that extend beyond the Cβ atom. Statistically observed preferences of side‐chain dihedral angles are summarized and correlated with stereochemical and energetic constraints. The distributions are compared with observed distributions in proteins of known X‐ray structures and with computed minimum‐energy conformations of amino acid derivatives. The distributions are similar in all three sets of data, and they appear to be governed primarily by intraresidue interactions. In side chains with no β‐branching, the most important interactions that determine χ1 are those between the CγH2 group and atoms of the neighboring peptide groups. As a result, the g‐ conformation (χ1 ⋍ ‐60°) occurs most frequently for rotation around the Cα‐Cβ bond in oligopeptides, followed by the t conformation (χ1 ⋍ 180°), while the g + conformation (χ1 ⋍ 60°) is least favored. In residues with β‐branching, steric repulsions between the CγH2 or CγH3 groups and backbone atoms govern the distribution of χ1. The extended (t) conformation is highly favored for rotation around the Cβ‐Cγ Cγ‐Cδ bonds in unbranched side chains, because the t conformer has a lower energy than the g + g ‐ conformers in hydrocarbon chains. This study of the observed side‐chain conformations has led to a refinement of one of the energy parameters used in empirical conformational energy computations.
Influence of trifluoroacetic acid on retention times of histidine‐containing tryptic peptides in reverse phase HPLC
Authors: ACHARYA A. SEETHARAMA , DI DONATO ALBERTO , MANJULA BELUR N. , FISCHETTI VINCENT A. , MANNING JAMES M.
Published: August 2010

The tryptic peptides of the aminoethylated α‐and β‐chain of hemoglobin have been separated on a Partisil‐10 ODS‐2 column with a linear gradient of acetonitrile containing 0.1% trifluoroacetic acid. The elution profile of the tryptic peptides of the chains obtained with this acetonitrile trifluoroacetate system has been compared with that obtained using phosphoric acid as the ion‐pairing reagent. This comparison demonstrated that trifluoroacetate influences the retention times of the histidine‐containing tryptic peptides much more than it affects those peptides that do not contain histidine residues. This behavior has been rationalized on the basis of ion‐pairing of trifluoroacetate with the histidine residues of the tryptic peptides.
Reexamination of sodium‐liquid ammonia reduction in the peptide chemistry†
Authors: SCHON ISTVÁN , SZIRTES TAMÁS , ÜBERHARDT TAMÁS , RILL ATTILA , CSEHI ATTILA , HEGEDUS BÉLA
Published: August 2010

Sodium‐liquid ammonia reduction has been used for over 50 years for removal of benzyl‐type protecting groups in peptide chemistry. Up until now a definitely blue end‐point has generally been accepted for detection of the completion of reaction. Systematic investigation with model compounds has revealed that this is not only unnecessary for the complete removal of the protecting groups but also that the application of sodium in excess results in many undesired transformations which can simply be suppressed or even eliminated by optimizing the sodium consumption.

Cleavage of tert. ‐butyloxycarbonyl group and N‐Cα bond, reduction of carboxamide groups to carbinol derivatives, transpeptidation and formation of a hydantoin derivative have been observed in model experiments by using sodium in excess.
Synthesis of an IgG fragment decapeptide exhibiting phagocytosis stimulating activity of polymorphonuclear leucocytes
Authors: MARTINEZ JEAN , LAUR JEANINE , WINTERNITZ FRANCOIS
Published: August 2010

Fragment 335–344 of human IgG was synthesized stepwise, using active esters of N ‐protected amino acids and benzotriazolyloxytris(dimethylamino)phosphonium hexafluorophosphate for coupling. This fragment could be liberated from the carrier molecule by the two specific enzymes responsible for the release of tuftsin from the same carrier molecule: tuftsin endocarboxy‐peptidase cleaves at the Arg‐Glu bond and leukokininase at the Lys‐Thr bond. This decapeptide fragment, Thr‐Ile‐Ser‐Lys‐Ala‐Lys‐Gly‐Gln‐Pro‐Arg showed significant activity in stimulating phagocytosis of human polymorphonuclear leucocytes.
L‐Serine tripeptides: Ac‐Ser‐Gly, Ala‐Ser‐Gly and Gly‐Ser‐Phe. An n.m.r. study
Authors: POGLIANI L. , ZIESSOW D.
Published: August 2010

The 1H and 13C n.m.r. spectra of Ac‐Ser‐Gly, Ala‐Ser‐Gly and Gly‐Ser‐Phe tripeptides have been measured and analysed at three different pD values. The n.m.r. parameters of Ser side‐chain are nearly pD independent. CαH group (13C/1H) of Ser residue of Gly‐Ser‐Phe shows a consistent pD dependence in acid solutions. Conformational calculations on Ser side‐chain show the growing importance of the gauche conformers on the overall conformation of the side‐chain all along the three tripeptides.
Multiple conformational equilibria of cyclic octapeptide, cyclo (L‐Pro‐Sar)4 in solution
Authors: SHIMIZU TOSHIMI , TANAKA YOSHIO , TSUDA KEISHIRO
Published: August 2010

Cyclo (l‐Pro‐Sar)4 is asynthetic cyclic octapeptide composed of only N ‐substituted amino acids. The conformation of this peptide in different solvents was examined by 1H‐and 13C‐n.m.r. spectroscopy, 1H‐n.m.r. data of this cyclic peptide demonstrated that multiple conformational equilibria take place in solution and they vary with solvent polarity. Three conformers are interconverting with each other in the nonpolar chloroform (CDCl3); one C4‐symmetric conformer (49%) and two C2‐symmetric conformers (37% and 14%). While three C2‐symmetric (59%, 19%, and 18%) and one asymmetric conformer (4%) are detected to coexist in acetonitrile (CD3CN), one largely populated C2‐symmetric one (97%) is favored in the polar dimethyl sulfoxide (Me2SO‐d 6). N.m.r. measurement employing various strategy predicted the occurrence of trans‐cis‐cis‐cis‐trans‐cis‐cis‐cis (two Sar‐Pro bonds: trans) (tccctccc) peptide bond sequence in a predominant C2‐symmetric conformer of Me2SO‐d 6 solution. In the same way, tccctccc and ctttcttt (two Sar‐Pro bonds: cis) peptide unit arrangement was proposed for the first and the secondly populated conformer in CD3CN, respectively. In CDCl3 a conformer having tctctctc (four Sar‐Pro bonds: trans) C4‐symmetric peptide bond sequence was deduced.
Ring conformation of cyclic octapeptide cyclo (L ‐Pro‐Sar)4 in the crystalline state
Authors: SHIMIZU TOSHIMI , UENO KATSUHIKO , TANAKA YOSHIO , TSUDA KEISHIRO
Published: August 2010

A single‐crystal X‐ray diffraction analysis has been made of the structure of the cyclic octapeptide cyclo(l‐Pro‐Sar)4. The material [C32H48O8N8 · (21/4) H2O° (1/2) CH3OH, Mr = 799.43] crystallizes in the monoclinic space group C2 with cell dimensions a = 14.544 (3), b = 11.902 (2), c = 14.064 (3), and β = 122.26 (2)° (Λ = 1.54178 Å, T = 293 K). The final R value for the 1980 observed reflections is 0.079. The ring conformation has the peptide bond sequences of cis‐cis‐trans‐trans‐cis‐cis‐trans‐trans (Pro‐Sar‐Pro peptide bond linkages are cis‐cis ‐or trans‐trans). The pyrrolidine rings in the four proline residues take an envelope form in which the γ‐carbon atom deviates from the plane of the remaining four atoms in the ring.
Statine and its derivatives. Conformational studies using nuclear magnetic resonance spectrometry and energy calculations
Authors: RICH DANIEL H. , TERADA YUKIMASA , KAWAI MEGUMI
Published: August 2010

The conformations of derivatives of 3(S)‐hydroxy‐4(S)‐amino‐6‐methylheptanoic acid (statine) and its analogs have been studied by n.m.r. in chloroform and in dimethyl sulfoxide, and by molecular mechanics calculations. The data obtained from these studies indicate that: 1) the coupling constant between NH and C4H is large, suggesting that the dihedral angle (θ) is near 165° or 0°; 2) the coupling constant between C4H‐C3H is small, indicating a vicinal bond angle of approximately 90°; 3) the hydrogen deuterium exchange rate of statine amide protons is slow; however, the rate is dependent upon the electron withdrawing substituents adjacent to the amide NH's; 4) intramolecular hydrogen bonds involving the NH of the statine amide group do not stabilize conformations of single amino acid derivatives. Based on the n.m.r. results, four possible conformations of Boc‐statine‐OMe in solution are possible. MM1 calculations indicate one conformation is especially likely.
CD‐resolved secondary structure of bovine plasma albumin in acid‐induced isomerization*
Authors: ERA SEIICHI , ASHIDA HIROSHI , NAGAOKA SHUNJI , INOUYE HIROSHI , SOGAMI MASARU
Published: August 2010

Bovine plasma albumin (BPA) showed the acid‐induced two‐step transition, the N‐F transition and acid‐expansion. Changes in fractions of α‐helix (fα), β‐form (fβ) and unordered form (fR) in the acid‐induced isomerization of BPA were studied using the method of Chen et al. (1972) with two constraints: fi = 1, 0 ± fi ± 1. pH‐profiles of fα and fR showed the two‐step change, one corresponding to the N‐F transition and the other to the acid‐expansion in 0.10 m KCl and in 0.02 m NaClO4. pH‐profile of fβ showed one‐step change, correlating to the later part (lower pH side) of the N‐F transition. The N‐F transition might thus involve the helix ± β and helix ± coil transitions.
Cyclols, cyclodepsipeptides, and N‐acyl‐diketopiperazines from linear precursors: Synthesis and crystal structure of 10‐membered cyclodepsipeptides
Authors: ZANOTTI GIANCARLO , PINNEN FRANCESCO , LUCENTE GINO , CERRINI SILVIO , GAVUZZO ENRICO , MAZZA FERNANDO
Published: August 2010

In order to investigate the relative formation tendency of different tautomeric ring systems (cyclols, cyclodepsipeptides and corresponding N ‐acyl‐diketopiperazines), two linear peptide precursors containing proline as C ‐terminal residue, have been synthesized and subjected to cyclizing conditions. Boc‐Ser‐Phe‐Pro‐ONp (I) gave three isomeric cyclic compounds: Boc‐Ser‐Phe‐Pro‐(IV), N ‐(Boc‐Ser)‐cyclo ‐(Phe‐d‐Pro) (III) and the corresponding aza‐cyclol (II). Starting from Hyb‐Phe‐Pro‐ONp (V) two epimeric N (3‐hydroxybutyryl)diketopiperazines (VI) and (VII) and the corresponding 10‐membered cyclodepsipeptide (VIII) could be isolated. Crystal and molecular structure of VIII is reported. Crystals of VIII are orthorhombic, P212121 with a = 9.684, b = 22.985, c = 7.841, z = 4. The two peptidic bonds are cis with ω values of 6.6° and — 18.1°, whereas the lactonic bond is of transoid type. The pyrrolidine ring has C2—Cγ‐exo conformation.
Conformation and mobility of tyrosine side chain in tetrapeptides: Specific effects of cis‐ and trans ‐proline in Tyr‐Pro‐ and Pro‐Tyr‐segments
Authors: JUY MICHEL , LAM‐THANH HUNG , LINTNER KARL , FERMANDJIAN SERGE
Published: August 2010

We examined the properties of tyrosine in four free tetrapeptides: Ala‐Ala‐Tyr‐Ala (AATA), Ala‐Pro‐Tyr‐Ala (APTA), Ala‐Tyr‐Ala‐Ala (ATAA) and Ala‐Tyr‐Pro‐Ala (ATPA) by CD, n.m.r. and energy calculations. Experimental data (the aromatic 1Lb signal, rotamer populations around the Cα‐Cβ bond (x1), rotations around Cβ‐ Cγ(χ2), chemical shifts of ortho‐ and meta‐protons in the phenolic ring (in aqueous and Me2SO solutions), NH proton temperature coefficients and vicinal coupling constants 3JNH‐CαH in the backbone (Me2SO solution) were compared with calculated minimum energy conformations. We find qualitative agreement between the results of the different techniques with respect to global tendencies of conformational behaviour: we present experimental evidence showing that the presence of proline in the sequence has a more pronounced effect on the side chain organization of the residues preceding it than on one succeeding it. This steric influence of proline on its immediate neighbor is even stronger in the cis isomer than in the more common trans isomer. The strong preference for Rotamer II (χ1 = 180°) over Rotamer I (χ1 = ‐ 60°) in ATPA (cis ‐form) concomitant with a noticeable deviation of χ2 is a striking example.
Studies on gliadin related peptides. I. Synthesis, purification and 1H n.m.r. characterization of the pentapeptide H‐Tyr‐(Gln)3‐Pro‐OH
Authors: PAVONE V. , ROSSI F. , PUCCI P. , ANDINI S. , FERRARA L. , DI BLASIO B. , PEDONE C.
Published: August 2010

The pentapeptide H‐Tyr‐(Gln)3‐Pro‐OH has been recently postulated to be the basic repetitive unit of a sequential polypeptide contained in wheat bread α‐gliadins, which are believed to be toxic factors in coeliac disease, gluten‐dependent enteropathy. Solid‐phase synthesis, purification and1H n.m.r. characterization in water solution of this peptide are described.
Synthesis and preliminary biological investigations of O‐sulphated dermorphin
Authors: De Castiglione Roberto , Perseo Giuseppe
Published: August 2010

Synthesis by a classical solution method of a sulphated analogue of dermorphin is reported. The product has proved to be devoid of any peripheral and central opiate‐ or CCK‐like activity in the tests assayed.
Protonated form of histidine 238 quenches the fluorescence of tryptophan 241 in subtilisin Novo
Authors: Shopova Maria , Genov Nicolay
Published: August 2010

The pH dependence of the fluorescence of phenylmethanesulfonyl‐subtilisin Novo after excitation at 300nm is studied. pK values of 5.9 and 10.3 were determined from the titration curve. The major source of indole fluorescence is tryptophan 106. Evidence is presented that the protonated form of histidine 238 quenches the fluorescence of tryptophan 241 in this enzyme. The quenching is explained by a charge‐transfer complex formation between the excited indole and imidazole rings which are parallel and quite close to each other in the X‐ray model.
Pharmacological, conformational and dynamic properties of cycloleucine‐2 analogues of oxytocin and [1‐penicillamine]oxytocin
Authors: HRUBY VICTOR J. , ROCKWAY TODD W. , VISWANATHA V. , CHAN W.Y.
Published: August 2010

The solid phase syntheses of [2‐cycloleucine]oxytocin and [1‐penicillamine, 2‐cycloleucine]oxytocin are reported. [1‐Penicillamine, 2‐cycloleucine]oxytocin is an oxytocin antagonist exhibiting noin vitrooxytocic activity. In thein vitrooxytocic assay, [1‐penicillamine, 2‐cycloleucine]oxytocin has a pA2value of 6.70 ± 0.08. [2‐Cycloleucine]‐oxytocin is afulloxytocin agonist exhibiting 4.9 ± 0.5 U/mg of oxytocic activity. Neither compound possesses any measurable agonist or antagonist activity in the rat pressor assay. Carbon‐13 nuclear magnetic resonance chemical shift parameters and spin‐lattice relaxation times (T1) of the antagonist, [1‐penicillamine, 2‐cycloleucine]oxytocin, indicate that the antagonist exhibits similar conformational and dynamic properties as other oxytocin inhibitors previously studied. The carbon‐13 nuclear magnetic resonance shift parameters and spin‐lattice relaxation times (T1) of the oxytocin agonist, [2‐cycloleucine] oxytocin, indicate that the agonist exhibits similar conformational and dynamic properties as oxytocin. These results are discussed in terms of the different receptor requirements for agonist and antagonist activities. It appears that there are different structural and conformational requirements at the 2‐position for oxytocic agonist and antagonist activities.
Electrophoretic and immunoelectrophoretic study of the enzymatic degradation of human orosomucoid (α1 ‐acid glycoprotein)
Authors: KROTOSKI W.A. , WEIMER H.E.
Published: August 2010

Purified, intact orosomucoid (α1‐acid glycoprotein) derived from whole human plasma was incubated with a number of proteolytic and saccharolytic enzymes under a variety of conditions. The unfractionated digests were immediately examined by both agar gel‐ and immunoelectrophoresis for the presence of antigenically active (precipitating) and/or inactive macrofragments. Despite otherwise clear evidence of rapid degradation by several proteases, no antigenic subunits were detected. Among the glycosidases, almond emulsin produced a suggestion of modification of the carbohydrate moiety of a sialic acid‐poor orosomucoid preparation obtained from Cohn Fr. VI, but had no effect on antigenic properties. These results are presented as further evidence for a lack of involvement of the extensive carbohydrate component of orosomucoid in its antigenic reactions, and support previous data implicating the polypeptide chain as solely responsible for its antigenicity.
9‐Fluorenylmethyl esters
Authors: BEDNAREK MARIA A. , BODANSZKY MIKLOS
Published: August 2010

N
α‐Protected amino acid 9‐fluorenylmethyl esters (Fm esters) were prepared by imidazole‐catalyzed transesterification of active esters with 9‐fluorenylmethanol (9‐hydroxymethylfluorene). The new carboxyl protection is unaffected by acids, but is efficiently removed by β‐elimination under the influence of secondary and tertiary amines. Primary amines and ammonia can cause slight amide formation. Deblocking was achieved also by catalytic hydrogenation.
Complete amino acid sequences of two protease inhibitors in the venom of Bungarus fasciatus
Authors: LIU CHEN‐SHENG , WU TSE‐CHONG , LO TUNG‐BIN
Published: August 2010

Two analogous protease inhibitors, VIIIb and IX in the venom of Bungarus fasciatus were reduced and carboxymethylated. Tryptic peptides were separated by cellulose thin‐layer peptide mapping technique, and amino acid sequences were analyzed by DABITC/PITC double coupling method. Alignment of all tryptic peptides was established by analyses of chymotryptic peptides and further confirmed by Staphylococcus aureus V8 protease digestion. IX consisted of 65 amino acid residues. VIIIb consisted of 62 residues, identical to the N‐terminal 62‐amino acid sequence of IX.
Self association of secretin in aqueous solution
Authors: BODANSZK MIKLOS , HANZMANN EDITH
Published: August 2010

Viscosity measurements of aqueous solutions of porcine secretin indicate self association of molecules of the hormone.
Synthesis and properties of dermorphin and an analog of β‐endorphin containing the dermorphin sequence
Authors: YAMASHIRO DONALD , NICOLAS PIERRE , LI CHOH HAO
Published: August 2010

Dermorphin (I) and [D‐Ala2, Phe3, Gly4, Tyr5, Pro6]‐βc‐EP (II) have been synthesized by the solid‐phase method (β‐EP, camel β‐endorphin). Positions I through 7 of II correspond to the sequence of I. Relative potencies of synthetic peptides in the mouse tail‐flick test for analgesia by the intracerebroventricular route were: human β‐endorphin, 100; camel β‐endorphin, 164; I, 450; II, 440. The dermorphin was about 670 times more potent than morphine in the assay. Peptide II represents a rare instance where the enkephalin moiety of β‐endorphin has been altered to produce a more potent analgesic.
1H n.m.r. parameters of the N‐terminal 19‐residue S‐peptide of ribonuclease in aqueous solution
Authors: GALLEGO E. , HERRANZ J. , NIETO J.L. , RICO M. , SANTORO J.
Published: August 2010

The 1H n.m.r. chemical shifts and the spin‐spin coupling constants of the N‐terminal 19‐residue S‐peptide of ribonuclease A have been measured in a 10mM solution in D2O, pD 3.0, 27d̀, at 300 MHz. The titration parameters for end groups Lys‐1 and Ala‐19 and side chains Lys‐1, Glu‐2, Lys‐7, Glu‐9, Arg‐10, His‐12 and Asp‐14 have been determined at 90 MHz. An assignment of observed signals to individual residue protons based upon characteristic shifts, spectral analysis, double resonance, titration shifts and comparison with the spectrum of C peptide (N‐terminal 13 residue) is proposed. Differences in the observed chemical shifts, pKa‘s and titration shifts with reference to those proposed as “random coil” parameters are not large enough to assume the existence of a significant population of secondary structure in the conditions studied. The Hα chemical shifts differences can be accounted for by the Phe‐8 phenyl ring current for an extended peptide backbone conformation and appropriate values for the torsion angles X1 Phe‐8 and X2 Phe‐8.
Alcohol induced conformational transitions of proteins and polypeptides
Authors: MISHRA A.K. , AHLUWALIA J.C.
Published: August 2010

Integral enthalpies of solution of diglycine in tert.‐butyl alcohol + water and of diglycine and β‐alanine in ethanol + water mixtures were measured at 298.15 K as a function of alcohol concentration. Enthalpies of transfer of the solutes from water to aqueous alcohol mixtures were evaluated from these data. Entropies of transfer of a peptide backbone unit (CH2CONH) and peptide group (CONH) from water to aqueous ethanol solutions were derived from the enthalpy of transfer data and the free energies of transfer of glycine, α‐alanine, β‐alanine and diglycine. The thermodynamic transfer functions are discussed in terms of “water structure” mediated solute‐solute interactions. The observed trends in the thermodynamic transfer functions have also been utilized to rationalize the effect of alcohols on the conformational stability of proteins and polypeptides in aqueous solutions
Circular dichroism of gonadotropin recombinants
Authors: STRICKLAND THOMAS W. , PUETT DAVID
Published: August 2010

Circular dichroic spectra have been determined for ovine and porcine lutropin, human choriogonadotropin, and their subunits (α and β). All nine homologous and heterologous αβ recombinants were prepared from the purified subunits and characterized by circular dichroic spectroscopy over the wavelength interval of 200–320 nm. Above 250 nm, the spectra of all recombinants were similar and more closely resembled the spectra of the β subunits than of the α subunits. Circular dichroic difference spectra above 250 nm, derived by subtracting the sum of the subunit spectra from the appropriate recombinant spectrum, were characterized by a negative extremum near 280 nm. For a common α subunit, the magnitude of this difference extremum was in the order choriogonadotropin β > ovine lutropin β > porcine lutropin β. Interestingly, this was the same order that we found for biological activity based upon an in vitro assay [Strickland, T.W. & Puett, D. (1981) Endocrinology109, 1933–1942]. The lutropin α‐containing recombinants exhibit a positive band at 235 nm which arises from the 233 nm band characteristic of the lutropin α subunit. Between 210–230 nm, the circular dichroic spectra of the recombinants are quite similar. Even at lower wavelengths only the human choriogonadotropin α subunit‐containing recombinants exhibit differences. Aside from the overall general similarity in the circular dichroic spectra of these recombinants, the most striking observation is that the spectrum of a given recombinant is quite distinct from the additive spectra of the constituent α and β subunits. This finding, in conjunction with spectral data and chemical evidence from other laboratories, supports the concept that the subunit conformations in an αβ complex differ from those of the free subunits.
Preferred conformations of tert.‐butyloxycarbonyl‐L‐aminosuccinyl‐glycyl‐glycine methyl ester in the solid and solution state
Authors: CAPASSO S. , MATTIA C.A. , MAZZARELLA L. , ZAGARI A.
Published: August 2010

Detailed conformational studies in the solid and solution state have been carried out on the blocked peptide tert.‐butyloxycarbonyl‐L‐aminosuccinyl‐glycyl‐glycine methyl ester, a model compound to study the conformational restrictions imposed by the presence of an aminosuccinyl residue in a polypeptide chain.

The crystals belong to the monoclinic space group P21 with a = 5.022(1), b = 15.193(3), c = 11.173(2) Å, β = 95.09(1)± and V = 849.0(5) Å3. The structure was solved by direct methods and least‐squares refinement, which included the coordinates of hydrogen atoms, converged at R = 0.030 for 1648 *** reflections. Although in the solid state the molecule prefers an ***extended ***mation, the i.r. and 1H n.m.r. spectra in chloroform solution *** that a folded conformation of the type II′ β turn, also predicted by the potential energy calculations, is stable.
Resolution of human mercapt‐ and nonmercaptalbumin by high‐performance liquid chromatography
Authors: SOGAMI MASARU , NAGOKA SHUNJI , ERA SEIICHI , HONDA MAKOTO , NOGUCHI KOHJI
Published: August 2010

Gel‐exclusion high‐performance liquid chromatographic (HPLC) analysis of human serum albumin (HSA) on PGP 2000 column (0.10 M sodium phosphate buffer, 0.30 M NaCl, pH 6.86) showed at least two peaks, the principal component corresponding to human mercaptalbumin (HMA) and the second one to human nonmercaptalbumin (HNA). Mechanism for the separation of HMA and HNA might be due to weak resin‐HSA interaction. HPLC analysis of bovine plasma albumin (BPA) showed a single peak on PGP 2000 column. The elution volume of HSA was larger than that of BPA, resulting in a clear resolution of HSA and BPA.
Side‐chain torsional energies, conformer populations, and other tests of an improved conformational energy program for peptides: ECEPP83
Authors: CHUMAN H. , MOMANY F.A.
Published: August 2010

Modifications made to potentials and partial atomic charges in the program ECEPP83 are shown to improve agreement between theoretical and experimental side‐chain rotamer populations. The bond torsional model is used to examine the subtle combination of forces acting on amino‐acid side‐chains and new torsional potentials are obtained using protein data and statistical methods of analysis. A new conformational distribution function is defined and the effects of conformational entropy upon conformational preference is discussed. Comparison of computed side‐chain populations to experimental data is made and selected results compared to n.m.r. 3JHNCαH coupling constants. New side‐chain geometry for Phe and Tyr is given in Appendix I.
Influence of the peptide chain length of new elongated tuftsin analogs on phagocytosis process
Authors: KONOPIŃSKA DANUTA , KAZANOWSKA BERNADA , BOGUS?WSKA‐JAWORSKA JANINA
Published: August 2010

In this paper the synthesis of the following elongated tuftsin analogs: Arg‐Thr‐Lys‐Pro‐Arg (1), Pro‐Arg‐Thr‐Lys‐Pro‐Arg(II), Lys‐Pro‐Arg‐Thr‐Lys‐Pro‐Arg(III) and Thr‐Lys‐Pro‐Arg‐Thr‐Lys‐Pro‐Arg(IV) by classical and solid‐phase methods are described. The obtained peptides were tested for their biological activity: restoration of the phagocytosis of defected granulocytes from blood of children with acute lymphoblastic leukemia (ALL).
Synthesis of polypeptide models of collagen
Authors: GUANTIERI V. , TAMBURRO A.M.
Published: August 2010

It is well known that the amino acid sequence of collagen contains a large number of tripeptide units such as Y‐X‐Gly, where Y and X can be any amino acid residue but most frequently are proline or hydroxyproline. Accordingly, several sequential polytripeptides, including repeating sequences of that type containing one or two imino acid residues, have been synthesized and studied in solution and/or in the solid state (1–14).

In this paper we describe in detail the syntheses via active esters of four polytripeptides of the type poly(Pro‐X‐Gly) and poly(X‐Pro‐Gly), where X is isoleucine or norleucine. The general objective was to study the influence of hydrophobic residues on the stability of collagen three‐dimensional structure; in particular we were interested in the introduction of branching at Cβ in view of the recent calculations of Némethy & Scheraga (15). The Nle residue was introduced in order to obtain reference polymers without any branching in the side chain. By way of comparison, we have shown earlier that polymeric sequences where X is leucine (branching at the Cγ) possess collagen‐like structures in an appropriate milieu (10, 11). The results of both theoretical and experimental conformational studies on the polymers will be published in a forthcoming paper.

Syntheses via p‐nitrophenyl esters are described for poly(Pro‐Ile‐Gly), poly(Ile‐Pro‐Gly), poly(Pro‐Nle‐Gly) and poly(Nle‐Pro‐Gly), four synthetic polytripeptide analogues of the non‐polar regions of collagens. The obtained polymers exhibit molecular weights in the range 5000–10000 as judged from viscosity measurements.