bluuebunny/crossref_metadata_2025 huggingface dataset:
Homo‐oligohistidines
Authors: Bonora G.M. , Toniolo C. , Jones J.H. , Rajasekharan K.N.
Published: August 2010

Conformational studies (CD, i.r., 1H n.m.r.) are reported for a series of N(α)‐t‐butoxycarbonyl, N(π)‐benzyloxymethyl‐homo‐oligo‐L‐histidine methyl esters ranging from the dipeptide to the heptapeptide. In chloroform at high dilution the extent and stability of intramolecularly hydrogen‐bonded folded forms were assessed as a function of chain length. In this low‐polarity solvent at high concentration the heptapeptide adopts a well developed intermolecularly hydrogen‐bonded β‐structure. In polar solvents such as 1,1,1,3,3,3,‐hexafluoro‐propan‐2‐ol and dimethylsulphoxide, unordered solvated forms were found to predominate.
Synthesis and binding properties of specific photoaffinity ligands for μ and δ opioid receptor subtypes
Authors: Garbay‐Jaureguiberry C. , Robichon A. , Roques Dr.B.P.
Published: August 2010

We report the synthesis and binding properties of specific photoaffinity ligands for μ and δ opioid receptor subtypes. These ligands are derived from DAGO: Tyr‐D‐Ala‐Gly‐NMePhe‐Gly‐ol, a μ selective probe and DTLET: Tyr‐D‐Thr‐Gly‐Phe‐Leu‐Thr, a δ selective probe by modifying the Phe 4 residue. These modifications are: i) a nitro group on the para position of Phe ring as Phe(4 NO2) or Nip, ii) an azido group as Phe(4 N3) or AZ. Pharmacological responses on mouse vas deferens (δ sites) and guinea pig ileum (μ sites), as well as competition experiments with [3H] DAGO and [3H] DTLET on crude rat brain membranes have been performed. The nitro group on the phenyl ring of the Phe residue preserves the affinity and selectivity of each probe: NipDAGO for the μ sites, NipDTLET for the δ ones. However the nitro probes do not appear to be photo‐activable by u.v. irradiation. Likewise, azidation of the phenyl ring of the Phe residue does not change the receptor selectivity of each probe, but AZDAGO has less affinity than its parent molecule DAGO, while AZDTLET has more affinity than DTLET. These compounds are photoactivable and provide an efficient tool to characterize and isolate the different receptor subtypes, especially the δ site.
Chymotrypsin catalysed synthesis of fluorescent amino acid amide and peptide derivatives
Authors: SKALLI A. , PUGNIÈRE M. , COLETTI‐PREVIERO M. A. , TORREILLES J. , PREVIERO A.
Published: August 2010

Chymotrypsin catalyses a condensation reaction between l‐methyl‐3,4‐dihydro‐ß‐carboline‐3‐methyl carboxylate and amino acid amides or peptides, yielding fluorescent derivatives. During the peptide bond formation, the enzyme ensures the reaction's steric control of both carboxyl and amino components.
Water structure in [Phe4 Val6] antamanide • 12H2O crystallized from dioxane
Authors: KARLE ISABELLA L.
Published: August 2010

Crystals of [Phe4 Val6] antamanide (cyclic[ValProProPhePhe]2) grown from dioxane/H2O, with space group P21212 and cell parameters a= 15.099(4), b = 22.008(5) and c = 11.024(3) Å, are almost identical to crystals grown from H2O/acetone, the structure of which was determined a number of years ago. Perpeptide molecule there are the equivalent of 12 water molecules occupying 16 sites in both crystals; however, in the new investigation a number of water molecules present at one‐half occupancy have been found in different positions than in the earlier analysis. The interpretation of the hydrogen bonding between peptide/water and between water/water is much more satisfactory. Pentagonal water assemblies are present in the solvent channel. There is a distinct indication of the occurrence of a bifurcated bond between two water molecules, as well as the presence of three‐center hydrogen bonds joining three water molecules. This may be the first experimental example of a bifurcated bond between two water molecules.
Desaminopenicillamine tocinoic acid derivatives ‐ inhibitors of oxytocin
Authors: ROY UMA , GAZIS DIANA , GLASS JOHN D. , SCHWARTZ IRVING L.
Published: August 2010

Tocinoic acid analogs with penicillamine in place of one or both of the cysteine residues have been studied and [1‐β‐mercaptopropionic acid, 6‐penicillamine] tocinoic acid (dPen6TA) and [1‐β,β‐dimethyl‐β‐mercaptopropionic acid, 6‐penicillamine] tocinoic acid (dPen1Pen6TA) have been synthesized in solution. Biological activities of these 2 compounds and those of the previously synthesized [1‐β,β‐dimethyl‐β‐mercaptopropionic acid] tocinoic acid (dPen1TA) have been assayed. It was found that dPen1TA and dPen1Pen6TA, both of which have a β,β‐dimethyl‐β‐mercaptopropionic acid in position 1, are strong inhibitors of the uterine activity of oxytocinin vitro(without Mg2+) with pA2values of 7.1 and 7.8, respectively, whereas dPen6TA with penicillamine in position 6 is a mild agonist.
Peptides containing dialkylglycines
Authors: COTTON RON , HARDY PAUL M. , LANGRAN‐GOLDSMITH ANDREW E.
Published: August 2010

A short route for the preparation of 2‐trifluoromethyl‐4,4‐dialkyloxazolin‐5‐ones (Tdo's), useful reagents for the addition of dialkylglycine residues to theN‐terminus of peptides, was examined. 2‐Trifluoromethyl‐oxazolin‐5(4H)‐one proved too unstable for a general substrate for alkylation, but 2‐trifluoromethyl‐4‐alkyl‐oxazolin‐5(2H)‐ones, readily available from protein amino acids, could be alkylated to Tdo's in the presence of mild base using active alkyl halides. 2‐Trifluoromethyl‐4,4‐dibenzyl‐oxazolin‐5‐one, prepared in this way as a stable crystalline solid, coupled well with protein amino acid esters or amides, confirming the utility of reagents of this type. Of a number of alkylations examined, only in the case of 2‐trifluoromethyl‐4‐isobutyl‐oxazolin‐5(2H)‐one using isobutenyl iodide was the isomeric 2‐trifluoromethyl‐2‐isobutenyl‐4‐isobutyl‐oxazolin‐5‐one observed at all; in this case, it predominated. Ammonolysis of Tdo's gave Tfa‐dialkylglycine amides,N‐deprotection of which using NaBH4unexpectedly gave 2‐trifluoromethyl‐4,4‐dialkylimidazol‐5‐ones. The partition coefficients (P) of a series ofN‐acetyldialkylglycinamides were measured. Comparison with the values obtained for similar derivatives of the corresponding protein amino acids showed a close correlation between the increasing hydrophobicity of the second side chain of the dialkylglycine derivative and the log P values obtained.
Complex of subtilisin BPN‘ with Streptomyces subtilisin inhibitor
Authors: KOMIYAMA TOMOKO , OOMORI AKIRA , FUKUYO KAZUNOBU , KANNO HIDEKI , MIWA MAKOTO
Published: August 2010

Structure of the complex of Streptomyces subtilisin inhibitor (SSI) with subtilisin BPN' was studied by examining the thermal denaturation and reducibility of disulfide bonds. The denaturation temperature of the complex was significantly higher than that of the enzyme. Two disulfide bonds localized in the inhibitor side were completely reduced in the complex, whereas only one of them was reduced in the free SSI. Gel filtration of the reduced complex solution showed clearly that the main products of reduction of the complex were two peptide fragments of SSI divided at the active site. The resistive disulfide bond in the complexed inhibitor became accessible as a result of a large conformational change due to splitting of the half‐reduced inhibitor.
Synthesis of a potent enkephalin analog, Tyr‐D‐Thr‐Gly‐Phe‐Δ3Pro‐NH2, and some of its biological activities
Authors: TZOUGRAKI CHRYSA , DAIRMAN WALLACE M. , MAKOFSKE RAYMOND C. , AEPPLI LISLOT , MEIENHOFER JOHANNES
Published: August 2010

The enkephalin analog, H‐Tyr‐D‐Thr‐Gly‐Phe‐Δ3Pro‐NH2 x HCl (VI)([D‐Thr2, Δ3Pro5]‐enkephalinamide), has been synthesized by conventional methods in solution and purified to homogeneity by reversed phase HPLC. The analog is a potent analgesic agent. For evaluation of some of its biological activity a related compound [D‐Thr2, Thz5]‐enkephalinamide (XI) was also synthesized in solution. Anti‐diarrhea activity was evaluated in mice by the intravenous route for anti‐DL‐5‐hydroxytryptophan (5‐HTP) induced diarrhea activity. Analgesic activity was assayed by the method of Nilsen in mice using the intravenous route, and by a modified tail flick test in rats and the acetic acid writhing test in mice following subcutaneous administration. Within the constraints of the assays the two analogs are approximately equipotent. Both are less active than [D‐Ala2, MePhe4, Met(0)ol]‐enkephalinol (XII). Earlier receptor binding studies of compound XI indicated enhanced affinity for the μ receptor and little for the δ receptor. By comparison this may also be the case for compound VI.
Conformations of cyclic octapeptides
Authors: VISHWANATH C.K. , GO ANITA , PARAMESWARAN K.N. , WANG Y.‐S. , KOPPLE K.D.
Published: August 2010

Stereoisomers of cyclo(Gly‐Pro‐Phe‐Ala‐Asn‐Ala‐Val‐Ser) were synthesized. NMR studies of their solution conformations, focusing on peptide N‐H solvent exposure, were made. These indicated that a single proline residue in the cyclic octapeptide ring is insufficient constraint to stabilize the backbone conformations that were previously established for cyclo(Gly‐Pro‐Phe‐Ala)2.
Effect of tertiary amines and amine salts on racemization in peptide synthesis
Authors: KOŁODZIEJCZYK ALEKSANDER M. , ŚLEBIODA MAREK
Published: August 2010

An effect of different tertiary amines, anions and cations on yield, product purity and reaction rate in DCC‐mediated Ac‐Phe‐Leu‐OMe synthesis was studied. Degree of racemization and side‐product yields down to 0.05% were readily determined by HPLC. The increasing effect of tertiary amino salts on degree of racemization was determined more precisely than previously and, more interestingly, their suppression of N‐acylurea formation was discovered. Unexpectedly, we found that the suppressing effect of the racemization of l‐hydroxybenztriazole was completely blocked by tribenzylamine. Furthermore, kinetic investigation showed that degree of racemization was not directly linked with 5(4H)‐oxazolone formation and aminolysis. The much greater racemization observed than calculated from the rate of formation and aminolysis of 5(4H)‐oxazolone led us to the conclusion that an activated form of Ac‐Phe other than 5(4H)‐oxazolone could be co‐responsible for racemization in the investigated reaction. An efficient method for preparation of N‐(acetyl‐DL‐phenylalanyl)‐dicyclohexylurea is described.
Conformational behaviour of some tachykinin C‐terminal heptapeptides
Authors: COTRAIT MICHEL , HOSPITAL MICHEL
Published: August 2010

The conformational behaviour of substance P, physalaemin and eledoisin C‐terminal heptapeptides was investigated using empirical energy calculations. Although the conformational distributions of the three heptapeptides are some‐what different, they have a few common low energy conformations. Some of them, which satisfy the structure‐activity relationships, may fit the well known SP‐P receptors.
Blood group antigens: synthesis of Ss antigenic peptides related to human glycophorinB
Authors: FERRARI B. , PAVIA A.A.
Published: August 2010

The human Ss blood group antigens are located on glycophorin B, a minor human erythrocyte membrane glycoprotein. The structural difference in Ss antigens is determined by a Met/Thr polymorphism at position 29. This report describes the first synthesis of the two peptides carrying the Ss specificities, SS: Asn‐Gly‐Glu‐Met‐Gly‐Gln‐Leu‐Val and ss: Asn‐Gly‐Glu‐Thr‐Gly‐Gln‐Leu‐Val.
Backbone‐side chain interactions in peptides
Authors: BOUSSARD G. , MARRAUD M. , AUBRY A.
Published: August 2010

Experimental investigations by infrared spectroscopy and proton nuclear magnetic resonance have been carried out on the dipeptides tBuCO‐Pro‐His‐Z (Z = NHMe: 1, OMe: 2) and on their Nπ and Nπ methylated analogues in various organic solvents. Both the neutral and protonated states of the His residue have been studied and they have revealed the different interaction modes of the His imidazole and His+ imidazolium rings with the peptide backbone. The dipeptide 2 assumes an extended conformation for both states, in which the imidazole or imidazolium‐NπH bond acts as a proton‐donor to the CO(tBu) carbonyl. The dipeptide 1 in the neutral state exhibits a high β1 folding ratio due to the existence of the His‐NH to imidazole‐Nπ hydrogen bond. This interaction is obviously absent from the protonated state and the βI folding ratio considerably decreases to the advantage of an open conformation similar to that assumed by 2. The His‐NH to imidazole‐Nπ hydrogen bond found in the βI folded conformer of 1 in the neutral state is the only His side chain to peptide backbone interaction retained in a strong aprotic medium.
Solution synthesis of antigenic and inhibiting peptides of the human renin prosegment‐1
Authors: FEHRENTZ JEAN‐ALAIN , SEYER1 RENÉE , HEITZ ANNIE , FULCRAND PIERRE , CASTRO BERTRAND , CORVOL PIERRE
Published: August 2010

The [Tyr47, Nle53] preprorenin (47–60) peptide methyl ester, a tetradecapeptide related to the human renin prosegment, has been synthesized using a three‐segment coupling strategy. Selective deprotection of the segments before coupling allowed an easy removal of the final tetradecapeptide side chain‐protecting groups by acidolysis and an easy purification. Antibodies raised against this peptide bound the plasmatic inactive renin.
Solvent dependent conformational statistics of enkephalin and angiotensin II
Authors: OLATUNJI O.L. , PREMILAT S.
Published: August 2010

A screened electrostatic potential model of hydration, recently proposed, is used to simulate the statistical behaviour of enkephalin and angiotensin II in solution. Curves of the end‐to‐end distances as well as calculated values of n.m.r. coupling constants are given and compared with experiments and results obtained from other theoretical studies. The satisfactory agreement between calculated values and the corresponding experimental data indicates that the present theoretical approach is a simple and efficient way to take into account solvent effects on the conformation of biological molecules.
Correctly folded proteins make twice as many hydrophobic contacts
Authors: BRYANT STEPHEN H. , AMZEL L. MARIO
Published: August 2010

A novel statistical analysis of non‐bonded contacts in a set of known protein structures shows that the natural residue types fall into five or six groups distinguishable by nearest neighbor preference. The observed pattern of contact specificities clearly reflects residue hydrophobicity and charge. Its most striking feature is that residues in the hydrophobic group make about twice as many contacts with one another as would be expected on a random basis. A similar increase in hydrophobic contact frequency can be observed at the level of individual proteins. Native proteins make, on average, about twice as many hydrophobic contacts as corresponding misfolded proteins (1), generated by computer. On the basis of these observations increased hydrophobic contact frequency is proposed as a simple model of the hydrophobic effect.
Synthesis of 3‐(3‐pyridyl)‐ and 3‐(3‐benzo[b]thienyl)‐D‐alanine
Authors: RAO PEMMARAJU NARASIMHA , BURDETT JAMES E. , CESSAC JAMES W. , DiNUNNO CECIL M. , PETERSON DOROTHY M. , KIM HYUN K.
Published: August 2010

The DL‐arylamino acid ethyl ester derivatives of β‐(3‐pyridyl)‐DL‐alanine, and β‐(3‐benzo[b]thienyl)‐DL‐alanine were synthesized by diethyl acetamidomalonate condensation with the respective arylmethyl halides followed by partial hydrolysis to the monoethyl ester and decarboxylation. Each derivative was enzymatically resolved to a separable mixture of the corresponding N‐acetyl‐L‐amino acid and the unchanged D amino acid derivative. Acidic hydrolysis of the latter gave the corresponding D‐amino acid, the optical purity of which was established by HPLC analysis of the 2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranosyl isothiocyanate (GITC) derivative. The free D amino acids were converted to D‐BOC derivatives by reaction with di‐tert‐butyldicarbonate in tert‐butyl alcohol, water and sodium hydroxide.
Cyclization of peptides on a solid support. Application to cyclic analogs of Substance P
Authors: PLOUX OLIVIER , CHASSAING GÉRARD , MARQUET ANDRÉE
Published: August 2010

The general conditions for cyclization of peptides on polymer matrix by disulfide bridge formation are reported. This procedure is based on attack of 3‐nitro‐2‐pyridinesulfenyl group (Npys) by a thiol function. It has been used for synthesis of five cyclic analogs of Substance P.
Structure and conformation of linear peptides. IX. Structure of l‐tyrosyl‐l‐phenylalanine
Authors: MURALI R. , SUBRAMANIAN E.
Published: August 2010

The dipeptide, l‐tyrosyl‐l‐phenylalanine (C18H20N2O4, molecular weight = 346) crystallizes as a monohydrate in the orthorhombic system, space group P212121 with a = 5.744(2), b = 8.284(2), c = 35.518(6)Å, Z = 4. The structure was solved by direct methods and refined to a final R‐index of 0.060. The peptide unit is trans and planar, and makes a dihedral angle of 93° with the plane of the carboxyl group. The backbone torsion angles are given by: ø1 = 164.7°, ω1 = 177.0°, φ2 = – 70.1°, ø2 = 146.6°. The values of the side‐chain torsion angles (χ1, χ2) are (47.3°, 79.9°) for tyrosine and (– 75.1°, 75.9°) for phenylalanine. The planes of the two (side‐chain) aromatic rings make a dihedral angle of 142.6° and their centres are separated by 9.3 Å.
Glucagon releasing activity of a cyclic peptide related to somatostatin
Authors: LYLE TERRY A. , FREIDINGER ROGER M. , NUTT RUTH F. , HOMNICK CARL F. , SAPERSTEIN RICHARD , VEBER DANIEL F.
Published: August 2010

A possible benefit of creating smaller and more rigid active analogs of somatostatin is the discovery of compounds which selectively inhibit the secretion of insulin, glucagon or growth hormone. A series of cyclic tetrapeptide analogs related to somatostatin was synthesized, and one member of this series was found to cause an unexpected stimulation of glucagon secretion while having little if any effect on either insulin or growth hormone secretion. A sustained increase in plasma glucose levels was also observed. Two possible modes of action are proposed.
Isosteric conversion of protein carboxyl groups into carboxamide groups. I. Examination of alkyl and aryl esters as model compounds
Authors: KOOISTRA C. , SLUYTERMAN L.A.æ.
Published: August 2010

With a view to substituting protein carboxyl groups by carboxamide groups the properties of a number of model compounds have been examined. The methyl ester of acetylglycine can be 97% converted into amide in 7 M ammonium acetate/ 7 M ammonia in 10 min. Amidation of the N‐ethylsalicylamide ester of benzoyl‐glycine, prepared by reaction with N‐ethylbenzisoxazolium fluoroborate (EBI), is 100% complete in 2 M ammonium acetate/ammonia, pH 9.2, within 1 min; no rearrangement into imide occurred at all. Under the conditions of protein modification (0.1 M EBI, pH 4.2, 0°) acetyltyrosinamide is 13% converted into a compound, presumably containing the N‐ethylsalicylimidate group, exhibiting an absorption maximum at 309 nm (e = 3300). This compound decomposes in ammonium acetate/ammonia, pH 9.1, within 1 min. Nα‐acetylhistidinamide is not converted at all. Reaction with aminogroups can either be avoided by protection of these groups or be analyzed by spectroscopy of the amidine produced. Spectral data required for analysis have been measured for N‐ethylsalicylamide (Λmax295 nm, e = 3200 at pH 6, Λmax324 nm, e = 5100 at pH 10, pK 8.15), for O‐acetyl‐N‐ethylsalicylamide (e = 1200 at 250 nm, e = 180 at 280 nm) and for O‐diethylsalicylamidine (Δmax277nm, e = 2330 at pH 6, Λmax302 nm, e = 3230 at pH 10, pK 7.90).
Circular dichroism studies on synthetic peptides corresponding to the cleavage site region of precursor proteins
Authors: REDDY G. LAXMA , NAGARAJ R.
Published: August 2010

The conformations of synthetic peptides which span the region in which the precursor part of proteins (signal sequences) destined for export are cleaved by signal peptidases, were investigated by circular dichroism spectroscopy. Pentapeptides comprising amino acids only from the carboxy‐terminus of signal sequences or the amino terminus of the mature protein do not have any preferred conformation in a variety of solvents. Octa‐ and nonapeptides containing amino acids from the carboxy‐terminal protion of signal sequences and the amino‐terminus of the mature portions of precursor proteins tend to adopt β‐turn conformations in trifluoroethanol and micelles of sodium dodecylsulphate. Hence, in addition to the distribution of amino acids with small side chains at the carboxy terminus of signal sequences, it is conceivable that signal peptidases also recognize a β‐turn conformation in the cleavage site region of precursor proteins.
Design, synthesis, and testing of potential antisickling agents. 9. Cyclic tetrapeptide homologs as mimics of the mutation site of hemoglobin S
Authors: SHEH LEUNG , MOKOTOFF MICHAEL , ABRAHAM DONALD J.
Published: August 2010

As part of our continuing search for new agents which might be useful for the treatment of sickle‐cell anemia, we have synthesized two cyclic tetrapeptide homologs, cyclo(‐Val‐Glu[‐Thr‐Pro‐]‐OH) (1a) and cyclo(‐Phe‐Glu[‐Thr‐Pro‐]‐OH (1b), and a tetrapeptide lactone homolog cyclo(H‐T‐hr‐Pro‐Val‐Glu‐OH) (2). The intent was that these peptides would mimic a tetrapeptide region around the mutation site of HbS and thus be able to bind at the acceptor site of HbS and thereby inhibit polymerization. The synthesis of the linear peptides was accomplished in solution using both the polymeric reagent (PHBT) and DCC/HOBT methods; cyclization was accomplished by an improved method. 13C‐n.m.r. studies were performed which allowed us to assign the conformation about the Thr‐Pro bond in 1a and 2 as trans. The cyclic peptides were tested for their ability to increase the solubility of HbS under deoxygenating conditions, but only 1a had any antigelling activity, albeit low.
Synthesis of the protected repeat sequence of glutelin‐2 of maize, Boc‐Val‐His‐Leu‐Pro‐Pro‐Pro‐OH, via nucleophilic cleavage from an Nbb‐resin
Authors: GIRALT E. , CELMA C. , LUDEVID M.D. , PEDROSO E.
Published: August 2010

The protected hexapeptide Boc‐Val‐His‐Leu‐Pro‐Pro‐Pro‐OH, the N‐terminal protected repeat sequence of glutelin‐2 of maize, has been synthesized on a bromomethyl‐Nbb‐resin. After cleavage of the peptide‐resin bond by two 3‐min treatments with dioxane/methanol/4n NaOH (30:9:1), gel filtration followed by anion‐exchange chromatography allowed the isolation of the target peptide (37% yield) and its methyl ester derivative (52% yield). Cleavage with dioxane/2‐dimethylaminoethanol/4n NaOH (30:9:1) has been found to be a simple and effective alternative to the photolysis of the peptide‐Nbb‐resin bond. After two 15‐min treatments with this reagent the protected hexapeptide was isolated by chromatography without apparent epimerization.
Conformation and stability of two recombinant human interferon‐α analogs
Authors: DAVIS JANICE M. , NARACHI MICHAEL A. , LEVINE HOWARD L. , ALTON N. KIRBY , ARAKAWA TSUTOMU
Published: August 2010

Structural features of a recombinantE. coliderived interferon‐α analog, interferon consensus1, was studied by circular dichroism and fluorescence spectroscopy. Circular dichroic spectra of the purified protein showed that it has about 70% α‐helix and a distinct tertiary structure. These structural features are similar to those for a natural interferon‐α subtype, interferon‐α2, indicating that the amino acid substitutions in interferon consensus1apparently did not alter the protein structure. Another analog, interferon consensus5, which has Ser instead of Cys at residues 1 and 99 but is otherwise identical to interferon consensus1, was prepared to study the role of the disulfide bond between Cys 1 and 99. Circular dichroic and fluorescence spectra indicated similarity in the structure of these two analogs. However, interferon consensus1was significantly more stable than interferon consensus5against denaturation. pH unfolding experiments indicated that the former protein is more stable in the transition region by about 1.6 kcal/mol, which was interpreted in terms of the increased free energy of the denatured state due to an extra disulfide bond in interferon consensus1.
Conformation of arginine side chain in a mini peptide. Molecular structure of acetyl‐l‐arginine‐ethylamide
Authors: COLL M. , SUBIRANA J.A. , SOLANS X. , FONT‐ALTABA M. , MAYER R.
Published: August 2010

The crystal structure of N‐α‐acetyl‐l‐arginine ethylamide perchlorate (molecular formula: C10H21N5O2 ± HClO4) has been determined from X‐ray diffraction data. This arginine derivative has the two charged ends substituted by peptide units and thus becomes representative of an arginyl residue in a protein. The crystals are orthorhombic, space group P21,21,21, a = 7.485 (2), b = 28.623 (5), c = 7.261 (3) Å, Z = 4. The structure was solved by direct methods and refined by full matrix least‐squares using 559 reflections to an R = 0.052. The molecule shows two planar peptide units with φ and ø values in the β pleated sheet region. The side chain torsion angles are in trans conformation, except the χ1, angle which is in the gauche(‐) region. This observation further illustrates that this is one of the favoured side chain conformations of arginine, together with the all‐trans conformation. Symmetric double hydrogen bonds are observed between the guanidinium group and perchlorate anions. The H(N) and oxygen atoms of the amide groups also form hydrogen bonds.
Thermodynamic studies of the interactions of alkylureas with glycine, diglycine, and triglycine
Authors: ẐZEROVNIK EVA , LAPANJE SAVO
Published: August 2010

The solubilities of glycine, diglycine, and triglycine have been measured in methyl‐, N,N '‐dimethyl‐, and ethylurea solutions. Gibbs free energies of transfer of glycine, the two oligoglycines, and the peptide group from water to alkylurea solutions have been calculated. Enthalpies of transfer for the same compounds and the peptide group have been determined from calorimetric measurements. The additivity principle is roughly obeyed for the contribution of the peptide group to the enthalpy of transfer. Comparison of the thermodynamic quantities of transfer to urea and alkylurea solutions reveals significant differences, those of the alkylureas clearly reflecting the hydrophobic interaction. Furthermore, Gibbs free energy of transfer of the peptide group to urea solutions is positive at lower urea concentrations but above 4 M it becomes negative and increases (i.e. becomes more negative) with increasing concentration. The interaction with the peptide group is thus an important factor in the denaturing activity of urea. For the alkylureas, on the other hand, the interaction with the peptide group is generally less favorable for unfolding.
Cyclic peptides
Authors: UEDA KAZUO , WAKI MICHINORI , IZUMIYA NOBUO
Published: August 2010

In order to explore the route for the preparation of cyclodepsipeptide by cyclization through an ester bond formation, two analogs of AM‐toxin II, cyclotetradepsipeptide, were synthesized. As a preliminary experiment, synthesis of [L‐Phe3, L‐Ser(Bzl)4]‐AM‐toxin II, containing L‐Phe and L‐Ser(Bzl) in place of L‐App (2‐amino‐5‐phenyl‐pentanoic acid) and ΔAla (α,β‐dehydroalanine), respectively, was attempted. Cyclization of H‐L‐Hmb‐L‐Phe‐L‐Ser(Bzl)‐L‐Ala‐OH in CH2CI2 at 10mM concentration using water‐soluble carbodiimide (EDC) and 4‐dimethylaminopyridine (DMAP) successfully gave a cyclic monomer in 16% yield. Cyclization of H‐L‐Hmb‐L‐App‐L‐Ser(Bzl)‐L‐Ala‐OH under the same conditions also afforded a cyclic monomer, [L‐Ser(Bzl)4]AM‐toxin II, in 19% yield. Analytical parameters of these cyclic monomers obtained were identical to those of the authentic samples obtained by cyclization through a peptide bond formation.
Simple, rapid method for converting a peptide from one salt form to another
Authors: GABRIEL THOMAS F.
Published: August 2010

A method for converting peptide trifluoroacetate salts to the corresponding acetate salts has been developed. The procedure involves reversed phase HPLC with a volatile buffer system. The method is exemplified by the conversion of Growth Hormone‐Release Factor, GRF(1–44)‐NH2 trifluoroacetate to the acetate which was achieved in > 95% recovery. Extensive analytical studies of the product confirmed the absence of trifluoroacetate and that the acetate salt was obtained without degradation. This procedure is expected to be generally applicable to other peptides and to other salt form conversions.
Effects of CuCl2 on the dimer‐tetramer equilibrium of concanavalin A
Authors: KANOH HIROFUMI , MAEDA HIROSHI
Published: August 2010

Tetrameric concanavalin A at neutral pH dissociated into the dimer when CuCl2 was added in a concentration range comparable to protomer concentration. This effect of CuCl2 was largely suppressed when NaCl concentration was increased. Neither the conformation of the protein nor its binding activity to 4‐methylumbelliferyl α‐D‐man‐nopyranoside was affected on addition of CuCl2.
Mild, orthogonal solid‐phase peptide synthesis: use of Nα‐dithiasuccinoyl (Dts) amino acids and N‐(iso‐propyldithio)carbonylproline, together with p‐alkoxybenzyl ester anchoring linkages*
Authors: ALBERICIO FERNANDO , BARANY GEORGE
Published: August 2010

Several Nα‐dithiasuccinoyl (Dts) amino acids (1) have been esterified without race‐mization by use of either N,N'‐dicyclohexylcarbodiimide or 1‐(3‐dimethylamino‐propyl)‐3‐ethylcarbodiimide hydrochloride, each in the presence of 4‐dimethylaminopyridine (0.1 equiv.), to 2, 4, 5‐trichlorophenyl 4′‐hydroxymethylphenoxyacetate (10) or the corresponding propionate (11). The resultant handle derivatives (8,9) were purified and then quantitatively attached onto aminomethyl supports by couplings using as solvent N,N‐dimethylformamide containing 1‐hydroxybenzotriazole (0.1 M). This methodology facilitates anchoring of Dts‐amino acids as p‐alkoxybenzyl esters, which can be cleaved in good yields by trifluoroacetic acid‐dichloromethane (1:1) at 25°. Model experiments established that quantitative thiolytic removal (>99.8%) of the Dts group occurs with (i) β‐mercaptoethanol (0.5M)‐N,N‐diisopropylethylamine (0.5M) in dichloromethane, 2 times 2min; (ii) N‐methylmercaptoacetamide (0.5M)‐N‐methylmorpholine (0.5M) in dichloromethane, 2 times 2min; and (iii) N‐methylmercaptoacetamide (0.5M)‐1‐hydroxybenzotriazole (0.1M) in N,N‐dimethylformamide, 2 times 2 min. The susceptibility of the Dts functionality to nucleophiles was also defined, including demonstration of tertiary amine‐catalyzed hydantoin formation from Dts‐dipeptidyl units, but side reactions from these processes are entirely avoided under appropriate conditions relevant to peptide synthesis. These observations were exploited to devise efficient, racemization‐free solid‐phase syntheses of a number of model peptides in high yields and purities, including L‐leucyl‐L‐alanylglycyl‐L‐valine, H‐Gly6‐Val‐OH, H‐Met‐Ala‐Gly‐OH, methionine‐enkephalin, and bradykinin.
Oligomerization of trypsin and chymotrypsin inhibitor from chick pea. A kinetic study
Authors: JACOBI D.
Published: August 2010

A mathematical method for determining oligomerization of a reversible enzymatic inhibitor has been developed. The method was applied to chick pea trypsin and chymotrypsin inhibitor (CI) and to Bowman‐Birk inhibitor (BBI) using trypsin and chymotrypsin with ester, amide and protein substrates. It has been shown that CI undergoes oligomerization whereas CNBr modified CI does not oligomerize. These results were substantiated by gel filtration on Sephadex G‐75. Oligomerization of BBI has been shown earlier by different methods. This oligomerization is shown here by the mathematical method. The kinetic data can be useful in determining oligomerization when the available amounts of an inhibitor are too small for gel filtration or when the oligomers are present in very small, and thus hard to detect, amounts.
Changes of dipole moments in the series of Boc‐(ProLeuGly)n‐OBzl oligopeptides and their possible explanation. A preliminary survey
Authors: SIEMION I.Z. , PEDYCZAK A. , ROSPENK M.
Published: August 2010

It was found that the dipole moments in the series of Boc‐(ProLeuGly)n‐OBzl oligopeptides (n = 1–5) measured in dioxane solution demonstrate a distinct concentration dependence beginning from dodecapeptide. This effect may be connected with the appearance of aggregated (triple‐helical?) structure in conformation equilibrium. The tendency to minimize the dipole moment of the system may be of some importance in the creation of supercoiled structures of polypeptides.
Structure analysis of trypsin inhibitors isolated from Cucurbitacae seeds. Circular dichroism studies
Authors: HIDER R.C. , DRAKE A.F. , MORRISON I.E.G. , KUPRYSZEWSKI G. , WILUSZ T.
Published: August 2010

Structure analysis jointly based on circular dichroism and Chou and Fasman analysis has been performed on a homologous group of 12 squash proteinase inhibitors. The analysis favours a structure incorporating 40–45% helix which is tightly crosslinked by three disulphide bonds. The proposed structure is consistent with the previously published CD and 1H n.m.r. spectra. The amino acid which forms the centre of the interaction between trypsin and the inhibitor, arginine5 or lysine5, is located on the N‐terminus of one of the helical segments. The basic residue is orientated away from the rest of the structure and thus is ideally situated for interaction with the confined space of the trypsin active site.
Identification of intramolecular crosslinks in bovine growth hormone after two‐step modification with 1,5‐difluoro‐2,4‐dinitrobenzene
Authors: ERMÁCORA M.R. , NOWICKI C. , WOLFENSTEIN‐TODEL C. , SANTOMÉ J.A.
Published: August 2010

Derivatives of bovine growth hormone, containing monoaminotyrosyl residues in positions 35, 42 and 174, were treated at pH 3.6 with a bifunctional reagent, 1,5‐difluoro‐2,4‐dinitrobenzene. Under these conditions aminotyrosyl groups reacted. On changing the pH to 9.3, the second fluorine atom of the reagent was substituted with the sterically adjacent side groups of lysine, since the excess of reagent had been previously removed. The modified protein underwent cyanogen bromide treatment. Peptides containing the crosslinks were purified from tryptic digests of the cyanogen bromide fragments by HPLC. Results show that aminoTyr 174 was able to form dinitrophenylene bridges with Lys 111, Lys 29 and Lys 170. AminoTyr 35 was found crosslinked to Lys 29. Taking into account the size of the reagent, it may be inferred that Lys 29, 111 and 170 are located at approximately 5 Å from Tyr 174 in the bovine growth hormone molecule.
Oxidation products of L‐lysine derivatives as starting materials for peptide synthesis and for the preparation of homoglutamic acid, homoglutamine and homoisoglutamine.
Authors: LIBEREK BOGDAN , KASPRZYKOWSKA REGINA
Published: August 2010

(2 S) 5‐Benzyloxycarbonylcarbamoyl‐2‐aminopentanoic acid, H‐L‐Aad(NHZ)‐OH 1 and (2 S) 5‐benzyloxycarbonylcarbamoyl‐2‐benzyloxycarbonylaminopentanoic acid Z‐L‐Aad(NHZ)‐OH 2 — oxidation products of L‐lysine derivatives H‐L‐Lys(Z)‐OH and Z‐L‐Lys(Z)‐OH — are convenient starting materials for peptide synthesis as well as for the preparation of L‐homoglutamic acid, L‐homoglutamine and L‐homoisoglutamine.
Some problems in direct Edman degradation of peptidyl‐resins
Authors: GOZZINI LUIGIA , De CASTIGLIONE ROBERTO , BALLABIO MARZIA , DI BELLO CARLO
Published: August 2010

Peptides covalently attached to an insoluble matrix through acid‐resistant linkages, as in the case of PAM and benzhydrylamine resins, have been submitted to Edman degradation directly on the same support used for the synthesis. Under Edman degradation conditions, Trp and His behaved as expected, giving deformylation and detosylation respectively, whereas protected Thr and Ser gave racemization products which have been identified by n.m.r. The rate constants of the racemization reactions have also been determined.
4‐Methoxybenzyloxycarbonyl amino acids in solid phase peptide synthesis
Authors: WANG S.S. , CHEN S.T. , WANG K.T. , MERRIFIELD R.B.
Published: August 2010

Moz‐amino acids were used in solid‐phase synthesis of Leu‐Ala‐Gly‐Val and thymosin α1. It was found that the Moz‐group can be removed rapidly and completely with 5–10% TFA in CH2Cl2. Some advantages of utilizing Moz‐amino acids over Boc‐amino acids in solid phase peptide synthesis are demonstrated.
β‐Subunit of baboon chorionic gonadotropinContinuous flow Fmoc‐polyamide synthesis of theC‐terminal 37‐peptide
Authors: WU CUI‐RONG , WADE JOHN D. , TREGEAR GEOFFREY W.
Published: August 2010

The synthesis of a 37‐peptide fragment derived from the carboxyl terminal of the β‐subunit of baboon chorionic gonadotropin has been accomplished by the continuous flow Fmoc‐polyamide solid phase method. The use ofN′‐fluorenylmethoxy‐carbonyl‐glutamine with its sidechain protected by the 4.4′‐dimethoxybenzhydryl group enabled successful incorporation of this residue onto a hydroxymethyl linkage agent without apparent side reaction.
Isolation and properties of the pituitary gonadotropin from silver carp (Hypophthalmichthys molitrix)
Authors: CHANG YEA‐SHA , HUANG FORE‐LIEN , CHEN CHIEN‐TSU , LO TUNG‐BIN
Published: August 2010

The gonadotropin of silver carp (scGTH) was purified from the pituitary glands in a yield of 8.4 mg g through extraction with 6% ammonium acetate (pH 5.1)–40% ethanol followed by 80% ethanol precipitation. DEAE‐cellulose chromatography and gel filtration. The molecular weight of scGTH is about 32 000 as estimated by gel filtration. Leucine and serine were the two N‐termini of scGTH. The amino acid composition of scGTH is rich in aspartic acid asparagine, glutamic acid/glutamine, valine, proline and half cystine. Its carbohydrate content is 22.2%. Biologically, scGTH significantly stimulated the steroidogenesis in carp testis and ovary in vitro and induced the ovulation in loaches. It also stimulated the 32P‐phosphate uptake into 1‐day‐old chicken testis. Immunologically. scGTH could cross‐react with the anti‐serum against cGTH and vice versa. In both cases parallel displacement curves were displayed.
New segment synthesis of α‐inhibin‐92 by the acyl disulfide method
Authors: YAMASHIRO DONALD , LI CHOH HAO
Published: August 2010

The thiocarboxyl group reacts with diaryl disulfides to give an unsymmetrical acyl disulfide in dimethylformamide (DMF) and a symmetrical diacyl disulfide in aqueous DMF. Both acyl disulfides react with the α‐amino group to form the peptide bond. The method was used in a new segment synthesis of α‐inhibin‐92 (α‐IB‐92) with use of 2,2′‐dipyridyl disulfide as activator. Thiocarboxyl peptides were synthesized by the solid‐phase method on 4‐[α‐(Boc‐Gly‐S)benzyl]phenoxyacetamidomethyl‐resin. The segments α‐IB‐92‐(1–34)SH (I), Msc‐α‐IB‐92‐(35–65)SH (II), Msc‐α‐IB‐92(66–92)OH (III), and Msc‐α‐IB‐92‐(35–92)OH (VI) were prepared in yields of 33, 36, 41, and 25%, respectively, with use of crystalline symmetrical anhydrides in double and triple coupling protocols. Segments I, II, and III were used in a 3‐segment synthesis of α‐IB‐92 with an overall yield based on starting resin of about 8% while a 2‐segment synthesis using I and IV gave 11%. An all stepwise synthesis of α‐IB‐92 gave 4.5%.
Solid phase synthesis and characterization of two canine gut gastrin‐releasing peptides
Authors: MILTON R. C. DE L. , MAYER E. , WALSH J.H. , RIVIER J.E. , DYKERT J. , LEE T.D. , SHIVELY J.E. , REEVE J. R.
Published: August 2010

Two canine gastrin‐releasing peptides originally isolated from gut tissue extracts have been synthesized by solid phase methodology and purified by preparative reverse phase high performance liquid chromatography (RP‐HPLC). The synthetic gastrin‐releasing peptides GRP1‐27 and GRP 5‐27 were characterized with regard to homogeneity and composition using nine different RP‐HPLC systems, mass spectroscopy, amino acid analysis, Edman degradation, methionine oxidation, and peptide mapping with tryptic, Staph. aureus V8 protease and cyanogen bromide cleavage (the latter two systems performed only with GRP 1‐27). Although a scarcity of the natural products prevented quantitative biological comparison of the synthetic and natural peptides, they were found to elute identically on RP‐HPLC co‐chromatography and similar dose dependent biological potencies were observed in canine antral muscle tissue contraction experiments. Indeed, all the peptides containing the bombesin‐like car‐boxyl terminal decapeptide sequence studied to date have similar biological activities.
Chemical modification of superoxide dismutase Extension of plasma half life of the enzyme through its reversible binding to the circulating albumin
Authors: OGINO TETSUYA , INOUE MASAYASU , ANDO YUKIO , AWAI MICHIYASU , MAEDA HIROSHI , MORINO YOSHIMASA
Published: August 2010

Protection of organisms from oxidative stress is one of the major prerequisites for aerobic life. Since intravenously injected Cu++/Zn++ ‐type superoxide dismutase (SOD) rapidly undergoes renal glomerular filtration and appears in urine in its intact form, its clinical use as a scavenger for superoxide radicals has been highly limited. To test whether reversible interaction of SOD with plasma albumin might decrease the rate of disappearance of the enzyme from the circulation, the lysyl residues of the human erythrocyte‐type enzyme were covalently linked with poly‐(styrene‐co‐maleic acid) butyl ester (SMA) via amide linkage. Affinity chromatographic analysis by an albumin‐Sepharose column revealed that the enzyme samples labeled with SMA (SMA‐SOD) tightly bound to the column, while unmodified SOD was eluted in the unbound fractions. SMA‐SOD bound to the column could be eluted by the buffer solution containing 0.1% sodium dodecylsulfate. In vivo analysis revealed that intravenously administered SMA‐SOD circulated bound to albumin with an extremely long half‐life (6 h), while unmodified SOD rapidly underwent renal glomerular filtration with a plasma half‐life of 4min. Thus, SMA‐SOD may effectively dismutate superoxide radicals in the circulation.
Further studies on the resolution of human mercapt‐ and nonmercaptalbumin and on human serum albumin in the elderly by high‐performance liquid chromatography
Authors: ERA SEIICHI , HAMAGUCHI TAKASHI , SOGAMI MASARU , KUWATA KAZUO , SUZUKI EIJI , MIURA KIYOSHI , KAWAI KENJI , KITAZAWA YOSHIAKI , OKABE HIROAKI , NOMA AKIO , MIYATA SEIJI
Published: August 2010

High‐performance liquid chromatographic (HPLC) analysis of human serum albumin (HSA) on Asahipak GS‐520 showed at least two peaks, the principal component corresponding to human mercaptalbumin (HMA) and the secondary one to nonmercaptalbumin (HNA). HPLC analysis of HSA on Asahipak ES‐520 N showed three peaks, the principal component corresponding to HMA, the secondary one to HNA having mixed disulfide with cysteine or glutathione and the tertiary one to HNA oxidized higher than mixed disulfide. Two kinds of rapid HPLC for the resolution of HSA into HMA and HNA were developed by the present authors. Using these HPLC, the present authors found a significant decrease in the fraction of HMA in the elderly.
Purification and primary structure of ostrich insulin
Authors: EVANS TRACEY K. , LITTHAUER DEREK , OELOFSEN WILLEM
Published: August 2010

Insulin has been isolated from ostrich pancreas by a procedure of acid ethanol extraction, adsorption onto SP‐Sephadex, gel permeation chromatography and HPLC. The primary structure of the ostrich insulin is identical to that reported for the chicken hormone. The isoelectric point as determined by polyacrylamide gel isoelectric focusing was significantly higher than that of the bovine hormone.
Peptide conformations — 49(1): Synthesis and structure‐activity relationships of side chain modified peptides of cyclo(‐d‐Pro‐Phe‐Thr‐Lys‐Trp‐Phe‐)
Authors: KESSLER H. , HAUPT A. , SCHUDOK M. , ZIEGLER K. , FRIMMER M.
Published: August 2010

Cyclic hexapeptide analogues representing the modified retro sequence of the amino acid residues 7‐11 of natural somatostatin are known to protect liver cells from phalloidin poisoning. To determine the influence of steric, lipophilic, and charge effects on (a) the conformation of the backbone and the aromatic side chains and (b) the biological response, the side chains of Phe2, Lys4, and Phe6 of cyclo(‐d‐Pro1‐Phe2‐Thr3‐Lys(Z)4‐Trp5‐Phe6‐), 1a, one of the most active peptides found so far, were modified by various residues. The discussion of conformationally relevant parameters proves that neither backbone conformations nor populations of aromatic side chain rotamers were altered by these substitutions. The potency of these derivatives in a cytoprotection assay varies by at most one order of magnitude (more or less active than the parent peptide 1a). A qualitative evaluation of lipophilic, steric, and charge effects reveals the dominance of lipophilic effects of aromatic residues; the most potent compounds contain aromatic substructures in the side chain of Lys4.
Rigid conformation in tert.‐butyloxycarbonyl‐l‐alanine ortho‐nitrophenyl ester
Authors: KARLE ISABELLA L. , BODANSZKY MIKLOS
Published: August 2010

Ortho‐nitrophenyl esters of blocked amino acids have significantly higher aminolysis rates than the corresponding para‐nitrophenyl esters. This difference prompted a series of investigations that led to the present study. Single crystal X‐ray diffraction analysis of tert.‐butyloxycarbonyl‐l‐alanine o‐nitrophenyl ester has shown a rather rigid molecular conformation with very restricted rotation about the ester bond owing to the wedging of one of the nitro oxygen atoms between the two oxygens of the ester group. A para nitro group can not interact in a similar fashion and consequently can have many more rotamers. The C14H18N2O6 ester crystallizes in space group P21, with a = 5.180 Å, b = 9.726 Å, c = 15.616 Å and β= 92.36 Å. There is only one intermolecular hydrogen bond, N(1)H…O(0) at 3.125 Å, that links neighboring molecules into infinite chains. There are no intramolecular hydrogen bonds.
9‐Acridinylpeptides and 9‐acridinyl‐4‐nitrophenylsulfonylpeptides
Authors: KARUP GUNNAR , MELDAL MORTEN , NIELSEN PETER E. , BUCHARDT OLE
Published: August 2010

The preparation of 6‐(9‐acridinylamino)hexanoic acid DHBT ester and Nα‐Fmoc‐N3 ‐ (4‐nitrophenylsulfonyl)‐l‐lysine DHBT ester and their application in solid phase peptide synthesis are described. The 9‐acridinylamino ligand was shown to confer high DNA affinity, probably by intercalation, to the resulting peptides. The 4‐nitrophenylsulfamido ligand furthermore resulted in “photonuclease” activity of some of the modified peptides.
Conformational studies on host‐guest peptides containing chiral α‐methyl‐α‐amino acids
Authors: ALTMANN EVA , ALTMANN KARL‐HEINZ , NEBEL KURT , MUTTER MANFRED
Published: August 2010

The conformational behaviour of host‐guest peptides of the type Ac‐Ala‐Xxx‐Ala‐Ala‐Xxx‐Ala‐Ala‐Xxx‐Ala‐Ala‐NH‐PEGM (Xxx =α‐aminoisobutyric acid (Aib), (S)‐2‐ethylalanine ((S)‐Iva). (S)‐2‐methyiserine ((S)‐α‐MeSer)) has been studied by CD spectroscopy in CF3CH2OH. CH3OH. and water and by i.r. spectroscopy in CHCl3 and in the solid state. In this way the relative helix‐inducing potential of the two chiral α‐methyl‐α‐amino acids (S)‐Iva and (S)‐α‐MeSer could be established in comparison to the strong helix‐former Aib. The results show that (S)‐Iva exerts a comparable helix‐inducing effect as Aib, making this amino acid a valuable complementary tool for the stabilization or induction of helices. No significant helix‐promoting effect was observed for (S)‐α‐MeSer in polar solvents; however, the i.r.‐spectroscopic data in CHCl3 and in the solid state point to a helical conformation under these conditions. Possible reasons for the different behaviour of (S)‐Iva and (S)‐α‐MeSer are briefly discussed.