bluuebunny/crossref_metadata_2025 huggingface dataset:
MONOIODOINSULIN SPECIFICALLY SUBSTITUTED IN TYR A14 OR TYR A19
Authors: LINDE SUSANNE , HANSEN BRUNO
Published: August 2010

Monoiodoinsulin was prepared using ion exchange chromatography. The isolated monoiodoinsulin showed on polyacrylamide gel electrophoresis two bands with different intensities related to the initial method of iodination. Each of the two bands were isolated from the gel, and determination of the iodine distribution among the tyrosyl groups showed that one band contained monoiodoinsulin substituted in Tyr A19 contaminated with monoiodoinsulin substituted in the B‐chain. The other band contained essentially A14 monoiodoinsulin. Polyacrylamide gel electrophoresis is a convenient method to prepare homogeneous A14 monoiodoinsulin with biological activity indistinguishable from that of native insulin.
CYCLIC PEPTIDES
Authors: YASUTAKE AKIRA , MIYAZAKI KOICHI , AOYAGI HARUHIKO , KATO TETSUO , IZUMIYA NOBUO
Published: August 2010

Four stereoisomers of a cyclic depsidipeptide containing a lysine and a 2‐hydroxy‐3‐phenylpropanoic acid (Hpp) residue have been synthesized and their susceptibility toward trypsin examined. Trypsin hydrolyzed cyclo(‐L‐Lys‐L‐Hpp‐) (I‐LL) and cyclo (‐L‐Lys‐D‐Hpp‐) (I‐LD) rapidly and cyclo(‐D‐Lys‐L‐Hpp‐) (I‐DL) and cyclo(‐D‐Lys‐D‐Hpp‐) (I‐DD) very slowly. Proteolytic coefficients of these substrates and a reference compound are shown as follows: I‐LL, 112; I‐LD, 34; I‐DL, 0.34; I‐DD, 0.11, and Ac‐L‐Lys‐OEt, 44. Possible mode of action of trypsin on these substrates was discussed.
β‐ENDORPHIN: SYNTHESIS OF ANALOGS WITH EXTENSION AT THE CARBOXYL TERMINUS WITH HIGH RADIORECEPTOR BINDING ACTIVITY
Authors: YAMASHIRO DONALD , FERRARA PASCUAL , LI CHOH HAO
Published: August 2010

Four analogs of human β‐endorphin (βh‐EP) have been synthesized: [Gly31]‐βh‐EP‐Gly‐NH2, [CH3(CH2)4NH312]‐βh‐EP, [Gly31]‐βh‐EP‐Gly‐Gly‐NH2, and [Gln8, Gly31]‐βh‐EP‐Gly‐Gly‐NH2. All are more active than βh‐EP in an opiate receptor binding assay. Stepwise extension at the COOH‐terminus shows a progressive increase in binding activity. The last analog, which combines extension at the COOH‐terminus with elimination of the remaining anionic charge in βh‐EP, is nine times more active than the parent molecule.
SYNTHESIS OF [8‐α‐HYDROXYISOCAPROIC ACID] OXYTOCIN
Authors: ROY J. , GAZIS D. , SCHWARTZ I.L.
Published: August 2010

The synthesis and biological activities of [8‐α‐hydroxyisocaproic acid] oxytocin are reported. Thein vivouterine responses to [8‐α‐hydroxyisocaproic acid] oxytocin are prolonged and those to deamino‐[8‐α‐hydroxyisocaproic acid] oxytocin (as well as those we have previously reported for deamino‐oxytocin) are very prolonged as compared with those to oxytocin. Time courses of thein vivouterine responses to deamino‐[8‐α‐hydroxyisocaproic acid] oxytocin and deamino‐oxytocin (as followed by plotting the intervals between the individual contractions of a response vs. time after peptide injection) differ from those to [8‐α‐hydroxyisocaproic acid] oxytocin and oxytocin.
TUFTSIN ANALOGS WITH D‐AMINO ACID RESIDUES*
Authors: NAWROCKA E. , SIEMION I. Z. , ŚLOPEK S. , SZYMANIEC ST.
Published: August 2010

The syntheses of nine tuftsin analogs containing D‐amino acid residues are described. Their biological activity is discussed in terms of possible influence of the configurational change in definite position of the peptide chain on the preservation of ß‐bend conformation of the tetrapeptide.
SEASONAL, CIRCADIAN AND EPISODIC VARIATIONS OF HUMAN IMMUNOREACTIVE β‐MSH, ACTH AND CORTISOL
Authors: CAUTER EVE WALTER‐VAN , VIRASORO EXEQUIEL , LECLERCQ RAOUL , COPINSCHI GEORGES
Published: August 2010

The 24‐hour profile of plasma levels of immunoreactive β‐MSH (IR‐βMSH), ACTH and cortisol was obtained at 15‐min intervals in six normal males in summer and winter. In the radioimmunoassay used, dilution curves of human β‐MSH and human β‐LPH were not parallel. A seasonal variation in basal pituitary‐adrenal secretion, with higher levels in winter than in summer, was demonstrated. A circadian rhythm was found to be significant for ACTH, IR‐βMSH and cortisol in all investigations. Whereas ACTH and cortisol patterns were largely concordant in all studies, there was a significant desynchronization of the circadian rhythm of IR‐βMSH as compared to ACTH in five cases. Eighty‐ three percent of the secretory spikes of cortisol but only 68% of the IR‐βMSH spikes were concomitant with an ACTH spike. Correlations between maximal levels of concomitant spikes were higher during the quiescent period of pituitary‐adrenal secretion (22.00–04.00) for ACTH‐cortisol whereas for ACTH‐ IR‐βMSH, highest correlations were found during the active early morning secretory phase (04.00–10.00). For the three plasma constituents studied, longer apparent half‐lives were found to occur when the basal level before spiking was already elevated, suggesting that ACTH, β‐LPH and cortisol are secreted in bursts superimposed on a continuous basal secretion. Absolute increments of concentration appeared to be relatively independent of the level before spiking. It is suggested that the dissociations between ACTH and IR‐βMSH fluctuations in plasma observed here result from in vitro proteolysis of β‐LPH.
USE OF THE CHROMOGENIC p‐(p‐(DIMETHYLAMINO) PHENYLAZO) BENZYL (AZ) ESTER IN THE SYNTHESIS OF LEU‐ENKEPHALIN
Authors: REYNOLDS GEOIFREY D. , HARDING DAVID R.K. , HANCOCK WILLIAM S.
Published: August 2010

Solution synthesis of Leu‐enkephalin has been achieved using the coloured carboxyl protecting p‐(p‐(dimethylaminojphenylazo)benzyl moiety throughout the synthesis. The intense colour of this protecting group allowed facile purification of protected intermediates on silica gel or ion exchange columns and visualisation on thin‐layer chromatography. The chromogenic p‐(p‐fdimethyl‐amino)phenylazo)benzyl ester group readily withstands successive treatments with 25% trifluoroacetic acid in dichloromethane yet is cleanly removed by catalytic hydrogenation.
[12‐ASPARAGINE‐B] HUMAN INSULIN: An Analogue with Modification in the Hydrophobic Core of Insulin*
Authors: SCHWARTZ GERALD P. , BURKE G. THOMPSON , KATSOYANNIS PANAYOTIS G.
Published: August 2010

The human [12‐Asparagine‐B] insulin ([Asn12‐B] insulin) which differs from the parent molecule in that the valine residue at position B12 is substituted by an asparagine residue, has been synthesized by the procedures developed in this laboratory. In stimulating glucose oxidation and lipogenesis the analogue exhibited potencies of 0.19% and 0.14%, respectively, as compared to insulin. In insulin receptor binding [Asn12‐B] insulin was found to possess a potency of ca. 0.29% compared to the natural hormone. At high concentrations this analogue is shown to have the same maximal activity in the in vitro assays as the natural hormone. This indicates that despite the low affinity of the analogue for the insulin receptor, the analogue‐receptor complex is fully capable of initiating the series of chemical events that leads to the biological response. It is concluded that the B12 valine contributes greatly in the maintenance of a structure possessing the proper receptor‐binding characteristics, but does not have any role in modulating the activity of the hormone‐receptor complex. The potency of this analogue by radioimmunoassay is at least 100‐fold higher than the in vitro biological assays, indicating that the immunological determinants of insulin can be essentially unrelated to the biological activity of the molecule.
ISOLATION OF α‐MELANOTROPIN AND N, O‐DIACETYLSERINE1‐α‐MELANOTROPIN FROM PORCINE PITUITARY EXTRACTS
Authors: BUCKLEY DOUGLAS I. , HOUGHTEN RICHARD A. , RAMACHANDRAN J.
Published: August 2010

In the course of isolation of α‐melanotropin (α‐MSH) from porcine pituitary extracts, a peptide with identical amino acid composition but slightly less polar properties compared to α‐MSH was detected and isolated by partition chromatography. The new peptide was identified as N, O‐diacetyl‐Ser1 ‐α‐MSH by high resolution nuclear magnetic resonance spectroscopy. N, O‐diacetyl‐Ser1 ‐α‐MSH was readily converted to α‐MSH by incubation at pH 9.5. The O‐acetyl analog of α‐MSH was found to be as active as α‐MSH in stimulating lipolysis in isolated rabbit adipocytes.
SYNTHESIS OF γ‐METHYL‐l‐LEUCINE (NEOPENTYLGLYCINE, NEO) AND DERIVATIVES SUITABLE FOR PEPTIDE SYNTHESIS
Authors: Fauchere Jean‐Luc , Petermann Claudia
Published: August 2010

The modified Strecker synthesis of Patel & Worsley was combined with an enzymatic deamidation in the final step, to produce the title compound. The amino acid is a member of the family of the “fat” amino‐acids with high lipophilicity and space‐filling properties, as estimated by its Hansch hydrophobicity constant and its Charton steric parameter v. It can be used for qualitative and quantitative studies of structure‐activity relationships in biologically active peptides. Three of its derivatives suitable for peptide synthesis are also described.
Conformation of linear homo‐oligoprolines
Authors: BENEDETTI ETTORE , BAVOSO ALFONSO , BLASIO BENEDETTO DI , PAVONE VINCENZO , PEDONE CARLO , TONIOLO CLAUDIO , BONORA GIAN MARIA
Published: August 2010

A conformational analysis of Piv‐l‐Pro‐d‐Pro‐OMe was performed in the solid state using i.r. absorption and X‐ray diffraction. The tertiary amide bond is in the trans conformation, whereas the tertiary peptide bond is in the cis conformation. The sequence of the, ø angles is F, F*. The preferred conformations of the pivaloylamino group, the pyrrolidine rings, and the ester moiety are also discussed.
s‐Cisand s‐transisomerism in acylproline analogs
Authors: GALARDY RICHARD E. , ALGER JEFFREY R. , LIAKOPOULOU‐KYRIAKIDES MARIA
Published: August 2010

N‐Acetyl‐2,3‐dehydroproline,N‐acetyl‐5‐oxo‐L‐proline,N‐acrylyl‐L‐proline,N‐acetyl‐L‐azetidine‐2‐carboxylic acid andN‐acetyl‐D,L‐pipecolic acid have been examined in2H2O by1H and13Cn.m.r. for the purpose of finding s‐cisor s‐translocked acylprolines. Conformationally locked acylprolines could be incorporated into proline‐containing peptide hormones such as angiotensin and thyroliberin in order to determine the rotational state of the peptide bond to proline in the hormone receptor complex. The populations oftransandcisrotational isomers were determined as a function of p2H in order to assign thetransandcisisomers and to compare the populations in all the acylprolines at neutral p2H, where thecisisomer is normally present. Proton spectra were also recorded at from 7° to 75° in order to qualitatively determine the exchange rate between the isomers. The majority of these analogs exhibit acis‐transisomerization similar to that ofN‐acetyl‐L‐proline in the ratio oftranstocisrotational isomer found at neutral p2H (about 1:1), the temperature dependence of the population ratio (none), and the coalescence temperature for proton resonances (greater than 75°). However,N‐acetyl‐5‐oxo‐L‐proline was found to be greater than 98% s‐transat neutral pH, compared to 50% s‐transinN‐acetyl‐L proline, and therefore a good candidate for synthesis of an s‐translocked peptide hormone.N‐Acetyl‐2,3‐dehydroproline rapidly exchanges between s‐cisand s‐transin contrast to all other proline analogs examined and exhibits coalescence of the β‐protoncisandtransresonances at 45°. Titration with the shift reagent Pr+++was employed to confirm the assignments of thecisandtransmethyl resonances of all of theN‐acetyl compounds exceptN‐acetyl‐5‐oxo‐L‐proline.
Allomalformin†
Authors: BODANSZKY MIKLOS , BEDNAREK MARIA A. , YIOTAKIS ATHANASIOS E. , CURTIS ROY W.
Published: August 2010

In an attempt to find explanation for the initial erroneous sequence assignment for malformin, a sequence‐isomer of the natural product, 3‐isoleucine‐5‐valine malformin or briefly “allomalformin” that on partial acid hydrolysis could have given rise to misleading fragments, was synthesized and compared with both natural and synthetic preparations of malformin. Allomalformin is identical to the parent microbial peptide (malformin A, or briefly malformin) with respect to biological activity and conformation (ORD and CD spectra) and is indistinguishable from it by high pressure liquid chromatography. Yet, the two isomers have slightly different Rf values on thin‐layer chromatograms and by this method no allomalformin could be detected in samples of the natural product. On the other hand both high pressure liquid chromatography and thin‐layer chromatography demonstrated the presence of the lower homolog, 5‐valine malformin, in the samples examined. On partial acid hydrolysis this natural analog should liberate Val‐Cys, while Cys‐Val forms from malformin itself. Similarly, the corresponding desthio cyclopentapeptides should give rise to Val‐Ala and Ala‐Val respectively; the former being more resistant to further hydrolysis persists in the partial hydrolysates. The presence of Val‐Cys in partial hydrolysates of malformin and of Val‐Ala in the partial hydrolysates of desthiomalformin, both originating from the accompanying lower homolog rather than from malformin itself, is likely to have led to the postulation of the erroneous Cys‐Val‐Cys partial sequence.
Two peptides released in the complex formation of α1 ‐antitrypsin with β‐trypsin; evidence for two structurally identical, inhibitory sites in α1‐antitrypsin
Authors: KLASEN EDUARD C. , VAN DER LINDE PIET C.G.
Published: August 2010

The exact mechanism of action of α1‐antitrypsin, the major protease inhibitor in human serum, is still unknown. Several investigators report the release of a small peptide during complex formation of α1‐antitrypsin with various proteases. In this study the release of two peptides each from the NH2‐and the COOH‐terminal regions of α1 ‐antitrypsin is demonstrated, indicating the presence of two inhibitory sites in α1 ‐antitrypsin. The amino acid sequence near the NH2 ‐terminal inhibitory site is determined to be X‐Ser‐Ile‐Pro‐Pro‐ and near the COOH‐terminal inhibitory site Y‐Ala‐Ile‐Pro‐Met‐Ser‐Ile‐Pro. The combined results of the present report and several other reports indicate the presence of two structurally identical inhibitory sites in α1‐antitrypsin located at both terminal regions in the molecule.
Human somatotropin
Authors: CHENG CHRISTOPHER H.K. , GRÁF LÁSZLÓ , LI CHOH HAO
Published: August 2010

Different mixtures of reduced‐alkylated thrombin fragments of human and sheep somatotropin have been tested for binding affinity to liver membranes. The bioassay data correlated well with the abilities of the fragments to form noncovalent recombinants as shown in separate biochemical studies.
Secondary structural properties of the oligomeric forms of mouse IgA and the unusual effect of guanidine hydrochloride*
Authors: YOUNG N. MARTIN , WILLIAMS ROSS E.
Published: August 2010

The circular dichroism spectra of the monomer, dimer and tetramer forms of MOPC 167 mouse IgA are reported. The spectra were very similar in the aromatic region (250–310nm) but the intensity of the negative band at 217nm, arising from the peptide backbone, was higher in the dimer and tetramer (— 4600 degree cm2 dmol‐1) than in the monomer (— 3400 degree cm2 dmol‐1). When monomer and dimer IgA were exposed to concentrations of guanidine hydrochloride around 1.3 M, the 217 nm band increased in intensity, twofold in the case of the monomer, and solutions of the dimer became turbid, indicating aggregation of the proteins and formation of a cross‐β‐structure. At concentrations of guanidine hydrochloride of above 2.3 M both proteins were similarly denatured, indicating that dimerization through J chain does not alter the stability of IgA. The aggregating effect of guanidine hydrochloride did not occur with samples of human IgA1 and IgA2 and may be related to the unusual CH1 domain of mouse IgA.
Synthesis and properties of human β‐endorphin‐(1–9) and its analogs
Authors: YAMASHIRO DONALD , GARZIA RAFFAELLA , HAMMONDS R. GLENN , LI CHOH HAO
Published: August 2010

Four analogs of human β‐endorphin (βh‐EP) were synthesized by the solid‐phase method: βh‐EP‐(1–9) (I), [D‐Ala2]‐βh‐EP‐(1–9) (II), [Gln8]‐βh‐EP‐(1–9) (III), and [D‐Ala2, Gln8]‐βh‐EP‐(1–9) (IV). Measurement in a radioreceptor binding assay with use of tritiated βh‐EP as primary ligand gave relative potencies as follows: Met‐enkephalin, 100; I, 76; II, 100; III, 200; IV, 200. Two new amino acid derivatives were prepared and used for synthesis of the analogs: Nα‐t‐butyloxycarbonyl‐O‐(cyclopentyl) ‐tyrosine and Nα‐t‐butyloxycarbonyl‐γ‐(cyclopentyl)‐glutamic acid.
Structure of secretory protein IV from rat seminal
Authors: Pan Yu‐Ching E. , Li Steven S.‐L.
Published: August 2010

The complete amino acid sequence of rat SVS‐IV protein, consisting of 90 residues, has been determined. The sequence of rat SVS‐IV protein is the first seminal vesicle secretory protein determined and it does not show any homology with other known protein sequences. The secondary structure of SVS‐IV protein as analyzed by methods of Fasman and Chou indicates that this protein contains 53%α‐helix, 36%ß‐turn and 11% random coil.
Studies on peptides
Authors: Akaji Kenichi , Fujii Nobutaka , Yajim Haruaki , Morig Motoyuki , Takagi Atsushi , Mizuta Kazuhiko , Noguchi Masato , Mcdonald T.J.
Published: August 2010

The heptacosapeptide amide corresponding to the entire amino acid sequence of chicken gastrin‐releasing peptide (cGRP) was synthesized similarly to the synthesis of porcine GRP by assembling six peptide fragments followed by depro‐tection with 1 M trifluoromethanesulfonic acid‐thioanisole in TFA. A new carboxyl‐activating reagent, thiazolidine‐2‐thione, was preferentially adopted for preparation of necessary fragments. The synthetic cGRP, purified by ion‐exchange chromatography, followed by partition chromatography, was active as the synthetic porcine GRP, when plasma immunoreactive gastrin level was examined in rats. No obvious difference was observed when synthetic and natural cGRP preparations were compared by HPLC, immunochemical property and biological activity in dogs.
Synthetic approaches to peptide analogues containing 4, 4‐difluoro‐L‐proline and 4‐keto‐L‐proline
Authors: SUFRIN JANICE R. , BALASUBRAMANIAN TRICHEY M. , VORA CHANDRANAN M. , MARSHALL GARLAND R.
Published: August 2010

An improved synthesis of 4, 4‐difluoro‐L‐proline is described. A key step in this synthesis involves the fluorination of Z‐4‐keto‐L‐proline benzyl ester, using diethylaminosulfur trifluoride (DAST), to give the corresponding Z‐4, 4‐difluoro‐L‐proline benzyl ester. Preparation of dipeptide derivatives containing 4, 4‐difluoro‐L‐proline has been accomplished by initial synthesis of the corresponding 4‐keto‐L‐proline dipeptide derivatives, which were then fluorinated with DAST. A one‐step synthesis of Boc‐4‐keto‐L‐proline from Boc‐4‐hydroxy‐L‐proline by chromium trioxide oxidation is reported. These synthetic procedures should facilitate the preparation of a variety of peptide analogues containing 4, 4‐difluoro‐L‐proline and 4‐keto‐L‐proline.
Synthesis, purification and conformational studies on enkephalin derivatives containing Λ‐amino‐n‐butyric acid
Authors: DI BELLO CARLO , ANDINI S. , FERRARA L. , NAPOLITANO R. , PAOLILLO L.
Published: August 2010

The solid‐phase synthesis of several analogs of enkephalin containing Λ‐amino‐butyric acid is reported. Synthetic strategies, purification methods, chemical and physicochemical characterization are discussed. The n.m.r. data suggest for some of the analogs structural features similar to the opioids.
Chemical mechanism to account for artifactual formation of shortened peptides with free alpha‐amino groups in solid phase peptide synthesis
Authors: KENT STEPHEN B.H. , MERRIFIELD R.B.
Published: August 2010

The formation of terminated peptides with free α‐amino groups has often been observed in stepwise solid phase peptide synthesis. This has been attributed to variable accessibility in regions of the swollen crosslinked resin supports. It is now shown that impurities in the amino acid reagents are responsible for these by‐products. Thus, sec. ‐butyloxycarbonylamino acids were isolated from tert. ‐butyloxycarbonylamino acids after treatment with trifluoroacetic acid under standard deprotection conditions for the removal of the tert. ‐butyloxycarbonyl (Boc) group. Direct reverse phase HPLC analysis of Boc‐amino acids from commercial sources also showed the sec. ‐Boc‐amino acids as impurities present at varying levels. The sec. ‐Boc group was stable to treatment at room temperature with trifluoroacetic acid in dichloromethane (1:1, v/v) (half‐life 7 years), but was removed by HF‐anisole under the standard conditions of cleavage and deprotection of assembled peptides. In model syntheses, the level of terminated free peptides corresponded to the level of preexisting sec. ‐Boc‐amino acid impurities present in the Boc‐amino acid reagents. Use of Boc‐amino acids with no detectable sec. ‐Boc resulted in negligible levels (< 0.05%) of terminated peptides. The problem is thus readily overcome by the use of pure Boc‐amino acid starting materials and is not a reflection of a shortcoming inherent to the polymer supported nature of solid phase syntheses as has been previously suggested.
Intramolecular cross‐linking of insulin. Preparation and properties of oxalyl‐and malonyl‐bis(methionyl) insulin
Authors: SRINIVASA B.R. , CARPENTER FREDERICK H.
Published: August 2010

The bifunctional reagents, oxalyl‐(Met‐ONp)2 and malonyl‐(Met‐ONp)2 have been prepared and investigated as reversible cross‐linking reagents for insulin and model compounds. The removal of the cross‐linking residues was demonstrated by the cyanogen bromide cleavage of oxalyl‐(Met‐Phe‐OMe)2 and malonyl‐(Met‐Phe‐OMe)2. Zinc‐insulin reacted with a molar equivalent of oxalyl‐(Met‐ONp)2 or malonyl‐(Met—ONp)2 in presence of excess triethylamine to yield oxalyl‐(Met)2‐insulin and malonyl‐(Met)2‐insulin, respectively. In these derivatives the N ‐terminal phenylalanine (B1 residue) was free. Thus the cross‐link was between A1 and B29 residues in insulin. All three disulfide bonds of these insulin derivatives undergo reduction with tributylphosphine to give six sulfhydryls. Airoxidation of reduced oxalyl‐(Met)2‐insulin and malonyl‐(Met)2‐insulin in 0.05 m disodium phosphate, pH 9.5, yielded products which were indistinguishable from oxalyl‐(Met)2‐insulin and malonyl‐(Met)2‐insulin respectively, as measured by physicochemical and biological methods. Cyanogen bromide cleavage of reduced and reoxidized malonyl‐(Met)2‐insulin in 70% formic acid regenerated insulin quantitatively, but only 40% of insulin was determined from similar treatment of oxalyl‐(Met)2‐insulin. The regenerated insulins exhibited the biological activity of native insulin. These studies strongly suggest that disulfide bonds formed during oxidation of reduced oxalyl‐(Met)2‐insulin and malonyl‐(Met)2‐insulin are identical to those found in insulin.
Solid‐phase synthesis of sauvagine‐(17–40)
Authors: SANTANGELO FRANCESCO , MONTECUCCHI PIER CARLO , GOZZINI LUIGIA , HENSCHEN AGNES
Published: August 2010

The solid‐phase synthesis of the tetracosapeptide corresponding to the C ‐terminal amino acid sequence of sauvagine is described. After purification by gel filtration, the polypeptide appeared to possess an acceptable degree of homogeneity, as judged by different kinds of electrophoresis and chromatography, and by automated Edman degradation analysis. Preliminary pharmacological results indicate that the fragment‐(17–40) is practically devoid of any sauvagine activity on the circulatory system and endocrine glands; a weak effect on gastric emptying delay has been demonstrated (1% of the natural product).
Invertebrate neuropeptide hormones
Authors: Josefsson Lars
Published: August 2010

The development of a long‐term research program on the neurosecretory hormones of arthropods is described. The purification and full characterization of the first invertebrate neurohormones, the red pigment‐concentrating hormone (RPCH) and the distal retinal pigment hormone (DRPH) demonstrated that they are peptides, an octapeptide and an octadecapeptide, respectively. Physiological function studies with the pure hormones and their synthetic preparations showed that the RPCH acts as a general pigment‐concentrating hormone (PCH), and that the DRPH, in addition to its light‐adaptive function, also constitutes a general pigment‐dispersing hormone (PDH). In the regulation of the color‐adaptation of the animals, the two hormones act as antagonists. The chromatophorotropic activities are widely distributed within the arthropod neuroendocrine systems. Purification of the pigment‐concentrating activities from the locust corpora cardiaca lead to the isolation and characterization of the first insect neurohormones, the adipokinetic hormones (AKH I and AKH II). These two hormones, AKH I being a decapeptide and AKH II being an octapeptide, are close structural analogs to the crustacean PCH, demonstrating a common evolution of arthropod neurohormones. The hormones of this PCH‐family all cross‐react, but structure‐function studies of the hormones show that quite different parts of their structure are involved in their binding to the various receptors.
Fluorescence study of human beta 2 microglobulin
Authors: Chauvet M. , Bourdeaux M. , Briand C. , Dell'Amico M. , Sarrazin M. , Vincent C. , Revillard J.P.
Published: August 2010

A fluorescence study human β2 microglobulin showed the existence of two types of Trp residues, one quite exposed to the solvent, the other buried in a hydrophobic environment. The change in excitation wavelength made obvious the existence of a Tyr to Trp energy transfer mechanism. Treatment by urea or guanidine chlorhydrate brought about quite different results. With the former denaturing agent, some Trp residues remained buried; with the latter, the protein was completely unfolded, as proved by iodide quenching. pH variations could not unfold β2m enough to convert all Trp residues to exposed ones. When heated, β2m supported a transition that began at 50° (melting temperature 63°) and was not reversible. All these results suggest a rather compact conformation as in a globular protein.
Studies on the structure of a novel peptide antibiotic, K‐582
Authors: KAWAUCHI HIROSHI , TOHNO MASAO , TSUCHIYA YOSHINORI , HAYASHIDA MITUO , ADACHI YASUSHI , MUKAI TERUO , HAYASHI ICHIRO , KIMURA SHUICHI , KONDO SHIGEJI
Published: August 2010

A novel peptide antibiotic, K‐582, which exhibited significant growth inhibition of Candida, viruses and ascites tumor in mice, was found in the culture medium of a strain of Metarhizium anisopliae by Kondo et al. (J. Antibiotics33, 535–542 (1980)]. K‐582 consisted of two components, designated K‐582 A and K‐582 B. Threonine, tyrosine, ornithine, and an unusual amino acid were common in both peptides, but lysine was an extra component of K‐582 A. The unusual amino acid was identified to be threo‐γ‐hydroxy‐L‐arginine (OHArg) by means of mass, nuclear magnetic resonance and infrared spectrometries of the derivatives and the related compounds. The threonine and the arginine were assigned to be L‐configuration, and the ornithine and the tyrosine to be D‐configuration in both K‐582 A and K‐582 B, and the lysine to be L‐configuration by comparison of their optical rotatory dispersion spectra with those of standard amino acids. The elucidation of primary structure revealed that they were closely related heptapeptides with the following sequence:

K‐582 A:H‐Arg‐OHArg‐Orn‐Thr‐Orn‐Lys‐Tyr‐OH;

K‐582 B:H‐Arg‐OHArg‐Orn‐Thr‐Orn‐OHArg‐Tyr‐OH,

and had the identical sequence in terms of the configuration of their constituents, namely L‐L‐D‐L‐D‐L‐D.
Amino‐acids and peptides
Authors: APLIN ROBIN T. , CHRISTIANSEN JAN , YOUNG GEOFFREY T.
Published: August 2010

An analogue of the local tissue hormone bradykinin, in which the terminal carboxy group is replaced by a chloromethyl ketone function, has been synthesised. A protected octapeptide, synthesised by the picolyl ester “handle” procedure, was coupled to Nδ, Nω‐dibenzyloxycarbonyl‐L‐arginyl‐choromethane; the product was deprotected by hydrogen fluoride, giving bradykinyl‐chloromethane. The preservation of the reactive chloromethyl ketone group and the entire structure of the product was confirmed by fast atom bombardment mass spectrometry. On the rat uterus and guinea‐pig ileum bradykinyl‐chloromethane was a weak agonist showing no antagonism of responses to bradykinin.
Somatostatin analogs which define the role of the lysine‐9 amino group
Authors: NUTT RUTH F. , VEBER DANIEL F. , CURLEY PAUL E. , SAPERSTEIN RICHARD , HIRSCHMANN RALPH
Published: August 2010

Structure‐activity studies of the lysine residue in the highly active cyclic hexapeptide somatostatin analog cyclo(Pro‐Phe‐D‐Trp‐Lys‐Thr‐Phe) confirm the importance of the lysine amino group for biological activity through the loss of activity seen on replacement of lysine by ornithine, arginine, histidine and p‐amino phenylalanine. Three analogs containing thialysine, γ‐ and δ‐fluorolysine were equipotent to the parent as inhibitors of insulin, glucagon, and growth hormone release. The pKa's of the amino groups in these equiactive peptides ranged from 8.23–9.4. The lack of a correlation between the basicity of the amino groups and the biological activities suggests that deprotonation is not required for biological activity.
tert.‐Butyl aminocarbonate (tert.‐butyloxycarbonyloxyamine) — a new acylating reagent for amines
Authors: Harris Robert B. , Wilson Irwin B.
Published: August 2010

tert.‐Butyl amino carbonate (1, tert.‐butyloxycarbonyloxyamine) was prepared by reaction of hydroxylamine with di‐tert.‐butyl dicarbonate (2). 1 was used to acylate different amino acids or amines in water or in aqueous dioxane. 1 was also prepared in situ and used to acylate amino acids directly. 1 reacted 1.5–2.5 times faster than 2 with all amines studied either in water or 50% (v/v) dioxane. Remarkably, 1 retained its ability to acylate amines even in acid solution; the rate of acylation of L‐Phe at pH 6.5 (15 M‐1˙ min‐1) was about 20% of the rate at pH 10 (72 M‐1˙ min‐1). 2 was not an acylating reagent below pH 7.0 and as expected, the rate at pH 8.3 (4 M‐1˙ min‐1) was about 10% of that at pH 9.3 (39 M ‐1˙ min‐1). Pure BOC‐amino acids were obtained in high yield and could be quantitatively deprotected by standard procedures.
Influence of synthetic peptide inhibitors on the thermal stability of thermitase, a serine proteinase from Thermoactinomyces vulgaris
Authors: Schreier E. , Fittkau S. , Höhne W.E.
Published: August 2010

The influence of chloromethyl ketones and methyl ketones of N‐acylated peptides on the thermal denaturation of thermitase was investigated in the presence and the absence of calcium ions. The chloromethyl ketone derivatives are known to react irreversibly with the enzyme, whereas the corresponding methyl ketones are reversible inhibitors. Both groups of inhibitors offer a broad variety of affinity constants. The irreversible inhibition of thermitase causes a marked stabilization against thermal denaturation. On the other hand, the enzyme stability is not influenced by the binding of reversible inhibitors. The stabilizing effect of calcium ions is not dependent on the inhibitor binding. The importance of bivalent interaction (bridge formation) in the active site region of the enzyme for its thermal stability is discussed.
Evidence for interaction of substrate analogs with chicken eggwhite lysozyme after exhaustive reduction of disulfide bonds
Authors: WHITE FREDERICK H.
Published: August 2010

In a study of factors that influence the remaining secondary structure of reduced chicken eggwhite lysozyme, N‐acetyl‐D‐glucosamine (NAG) and N, N1‐diacetyl‐chitobiose (di‐NAG) were found to alter the circular dichroic (CD) spectrum of the reduced protein and its carboxymethyl derivative (Cml). Thus, negative ellipticities in the far u.v. were greater in the presence of the analogs, with NAG being the more effective. For Cml, curve fitting analysis of the CD data indicated an increased helical content in the presence of NAG by an average of 3% of the chain length, while β‐structure decreased by an equivalent amount. Other compounds structurally related to NAG produced no similar effects on the CD spectrum of Cml, nor were comparable effects of NAG in evidence on the Cm reduced derivatives of ribonuclease, chymotrypsin, wheat germ agglutinin, or α‐lactalbumin. The effect therefore appears specific between NAG and Cml. Conversion of the tryptophan residue at Position 62 of Cml to the oxindole‐alanyl derivative prevented these effects of NAG, and this residue may therefore participate in the interaction. During a 4‐day incubation at room temperature, the analog preserved the CD spectrum of Cml as well as its concentration. This effect was nearly specific when compared with other Cm reduced proteins and with other carbohydrates. Only one, N‐acetyl mannosamine, was effective in preserving the concentration of Cml, but not the CD spectrum. Since D‐glucos‐amine was entirely without effect on either the CD spectrum of Cml or on its change during incubation, the acetyl group appears essential for the NAG‐Cml interaction. The specificity between NAG and Cml is tentatively accounted for in terms of interactions with the primary structure, rather than with the remaining secondary structure. It is suggested that the stabilizing effect noted here could reflect a naturally occurring interaction between a substrate‐related ligand
Radioiodinated [D‐Ala2, Met 5] enkephalin
Authors: YEUNG CLEMENT W. T.
Published: August 2010

125I[D‐Ala2, Met5] enkephalin with high specific activity (122–185 Ci/mmol) was prepared and purified by Sep‐Pak C18reverse phase cartridge followed by high performance liquid chromatography (HPLC). HPLC at pH 3.0 resolved125I[D‐Ala2, Met5] enkephalin into two fractions, which ran as a single spot in thin‐layer chromatography with the same Rfvalues. Alkaline hydrolysates of the HPLC‐purified fractions showed a single spot corresponding to monoiodotyrosine standard when analysed by thin‐layer chromatography. Binding kinetics of the tracer was found to approach equilibrium after 30 min at 24d̀. Scatchard analysis of the saturation equilibrium binding studies gave an equilibrium dissociation constant of 3.58 nM and the number of binding site of 30 fmol/mg protein. Enkephalin analogs were capable of displacing125I[D‐Ala2, Met5] enkephalin binding from the rat brain plasma membrane. The effective concentration of [D‐Ala2, Met5] enkephalin and [D‐Ala2, Leu5] enkephalin for 50% inhibition of125I[D‐Ala2, Met5] enkephalin binding was estimated to be 79 nM and 23 nM, respectively. Both substance P and gastrin tetrapeptide failed to displace the125I[D‐Ala2, Met5] enkephalin binding to any significant extent. The125I[d‐Ala2, Met5] enkephalin prepared by the present procedure is therefore a useful tracer. This method of preparing radioiodinated peptide may be applicable to other enkephalin analogs or neuropeptides in general.
Predictions of the conformation and antigenic determinants of the V‐sis viral oncogene product homologous with human platelet‐derived growth factor
Authors: ROBSON B. , PLATT E. , FINN P.W. , MILLARD P. , GIBRAT J. F. , GARNIER J.
Published: August 2010

In an extensive study involving unification of secondary structure prediction methods to predict peptide backbone angles, folding simulations, and interactive graphics we have calculated conformations for a 160 residue p28sis protein fragment. We demonstrate that the state of the art is sufficient to aid artificial vaccine design.
H n.m.r. spectrum from the flexible N‐terminal segment of Streptomyces subtilisin inhibitor
Authors: AKASAKA KAZUYUKI
Published: August 2010

The 1H n.m.r. spectrum of Streptomyces subtilisin inhibitor shows a limited number of unusually sharp signals at room temperature. Some of these signals are assigned uniquely to protons of the side chains of the N‐terminal segment, Aspl‐Ala2‐Pro3‐Ser4‐Ala5‐Leu6‐Tyr7‐based on experiments of spin decoupling, pH titration, and enzymatic cleavage of the protein. Quantitative examination of these signals indicates that the N‐terminal end of this protein is heterogeneous in that the protein contains a considerable fraction whose sequence starts with Ala2 rather than with Asp1. The pKa values for the amino groups of Asp1 and Ala2 exposed at the N‐terminus are determined to be 8.9 ± 0.4 and 9.0 ± 0.1, respectively. Furthermore, examination of the line‐widths of the methyl proton resonances of Ala2 and Ala5 residues indicates that the N‐terminal peptide segment is free and undergoes rapid segmental motions in the order of 10−9s.
Comparison of hydrolysis of atriopeptin II stand‐in substrate by atrial dipeptidyl carboxyhydrolase and angiotension I‐converting enzyme
Authors: HARRIS ROBERT B. , WILSON IRWIN B.
Published: August 2010

We recently found and partially purified a new membrane‐bound metallo dipeptidyl dipeptidase from bovine atrial tissue homogenates (Harris, R.B. & Wilson, I.B. (1984) Arch. Biochem. Biophys.233, 667–675). We suggested that this enzyme was capable of cleaving the dipeptide, phenylalanyl‐arginine from the C‐terminus of atriopeptin II to give atriopeptin I. The atriopeptins are two atrial natriuretic peptides and the existence of the atrial peptide system has implicated the mammalian heart as an endocrine organ. The tetrapeptide benzoyl‐glycyl‐seryl‐phenylalanyl‐arginine was synthesized because it contains the C‐terminal tripeptide sequence of atriopeptin II and should be useful to test the roles of the atrial enzyme and angiotensin I‐converting enzyme in processing the atrial peptides. We found that for the atrial enzyme, Vmax was 13‐fold higher and Km 7‐fold‐lower for this stand‐in substrate than for benzoyl‐glycyl‐histidyl‐leucine, a standard substrate used to measure converting enzyme activity. The ratio of Vmax/Km as a measure of substrate specificity indicates that the stand‐in substrate is 86‐fold better than benzoyl‐glycyl‐histidyl‐leucine. In contrast, the stand‐in substrate is a 20‐fold poorer substrate for the converting enzyme than benzoyl‐glycyl‐histidyl‐leucine. With the stand‐in substrate, the converting enzyme showed pronounced substrate inhibition. An effective Vmax and Km were calculated using only concentrations of S below the optimum substrate concentration. These results confirm that the atrial enzyme is distinct from the converting enzyme. They also suggest that the conversion of atriopeptin II to atriopeptin I is a physiological process that is mediated by this enzyme.
Circular dichroic and fluorometric studies on the acid‐induced isomerization of bovine plasma albumin – 1‐anilino‐8‐naphthalenesulfonate complex
Authors: ERA SEIICHI , KUWATA KAZUO , KIDA KIMIHIRO , SOGAMI MASARU , YOSHIDA AKIHIKO
Published: August 2010

The acid‐induced isomerization (the N‐F transition) and expansion of bovine plasma albumin – 1‐anilino‐8‐naphthalenesulfonate complex, BPA‐ANS1.0 complex (molar ratio of added ANS to BPA = 1.0) were studied by measuring fluorescence and induced CD spectra of ANS. Decrease in the reciprocal of fluorescence polarization, increase in fluorescence intensity and blue shift of fluorescence of ANS in BPA‐ANS1.0 complex were correlated with the initial part of the N‐F transition and/or the N‐F1 transition. Induced CD spectra of ANS showed positive bands at 250–258 and 320–350 nm and one negative band at 280 nm. Most of changes (decreases) in ‐[θ]280 were also correlated with the initial part of the N‐F transition and/or the N‐F1 transition. Changes in fluorescence parameters and induced CD spectra of ANS (‐[θ]280) might indicate the conformational changes around a strong ANS binding site in the N‐terminal domain (Reed et al. (1975), Jonas & Weber (1970) and Brown & Shockley (1982)).
Kinetics of formation of hydrophobic regions during refolding of bovine serum albumin
Authors: DAMODARAN SRINIVASAN
Published: August 2010

The rate of formation of hydrophobic regions during refolding of bovine serum albumin was studied using 1‐anilinonaphthalene‐8‐sulfonate as the hydrophobic fluorescent probe. The refolding of serum albumin exhibited a sigmoidal behavior. The exhibition of a lag phase followed by a faster kinetic phase suggested that the refolding is a cooperative, sequential process. Refolding under reducing conditions almost completely inhibited the regeneration of hydrophobic binding regions, suggesting that the formation of disulfide bonds plays an important role in the refolding of serum albumin. The rate and the extent of refolding was apparently maximum at about 20° at 37° the extent of refolding was very low compared to that at the other temperatures studied. Based on the results, the mechanism of albumin refolding is interpreted in terms of domain structures and interdomain interactions.
Cyclic peptides
Authors: Lee Sannamu , Noda Kosaku , Aoyagi Haruhiko , Kato Tetsuo , Izumiya Nobuo
Published: August 2010

Cyclochlorotine (CCT) is a toxic metabolite of Penicillium islandicum Sopp, having the structure of cyclo(‐L‐Ser‐L‐β‐Phe‐L‐Ser‐L‐Pro(Cl2)‐L‐Abu‐). An analog of CCT, cyclo(‐L‐Ser‐L‐β‐Phe‐L‐Ser‐L‐Pro(Cl)‐L‐Abu‐) ([L‐Pro(Cl)4]CCT, 1), has been synthesized by the conventional method for peptide synthesis in order to study possible toxic activity of 1. Peptide 1 showed no toxicity toward several microorganisms and mice. 1H‐N.m.r. and CD studies on 1 indicate that the conformation of 1 in solution is similar to that of crystalline CCT. These results suggest that 3‐cis‐chlorine moiety of Pro(Cl2) in CCT plays an essential role in biological activities.
Synthesis and metal‐coordination properties of dimeric cyclo‐L‐hemicystinyl‐glycine
Authors: BRESSAN MARIO , COVIELLO ANTONIO , MARCHIORI FERNANDO
Published: August 2010

The structure of dimeric cyclo‐L‐hemicystinyl‐glycine, investigated by 1H n.m.r. in solution, displays a buckled diketopiperazine ring with a folded side‐chain. A disulfide sulfur atom is the primary coordination site for transition metal ions, such as Rh(III), Pd(II) and Pt(II).
Configuration of thionopeptide bond in solution
Authors: GUTHRIE D.J.S. , WILLIAMS C.H. , ELMORE D.T.
Published: August 2010

A comparison of the Nuclear Overhauser Effect (NOE) between α‐carbon protons and amide protons in a protected dipeptide, the corresponding protected thionodipeptide and the corresponding cyclothionodipeptide shows that the acyclic thionodipeptide has the trans‐configuration.
Carboxylate groups in bovine somatotropin involved in growth promoting activity*
Authors: DELFINO JOSÉ M. , FERNÁNDEZ HORACIO N. , SANTOMÉ JOSÉ A.
Published: August 2010

Modification of approximately one fifth of the carboxylate groups in bovine somatotropin with a water soluble carbodiimide caused loss of growth promoting potency pointing to the existence of residues related to the hormonal activity among those belonging to a fast reacting set. A sigmoidal curve was obtained whether the inactivation process was referred to reaction time or degree of modification. Isoelectrofocusing of derivatives released the native hormone from responsibility for the biological potency exerted by preparations with 1.5–2.6 modified carboxylate groups. Examination of the individual reaction kinetics of the 11 fast reacting residues, in turn, excluded the possibility of the sigmoidal character of the inactivation curve being caused by a nonexponential disappearance of essential residues, as a possible consequence of the chemical modification of others. According to synthetic models, the experimental curve may be the consequence of the effect of cumulative modification of 2 or 3 out of a set of 3 to 8 relevant residues.
Atomic size packing defects in proteins
Authors: CONNOLLY MICHAEL L.
Published: August 2010

The three‐dimensional refined high resolution structures of 20 proteins were examined for the presence of packing defects of atomic size or larger. Of the proteins examined, 12 had no such packing defects, 6 proteins had just 1 packing defect, and 2 proteins had 2 or 3 packing defects. These results confirm earlier studies on smaller samples of proteins which demonstrated that proteins are well packed. The atoms that surround the packing defects are almost always hydrophobic (carbon or sulfur). This study also tabulated the number of internal waters in each protein, which varied from 0 to 28.
Mesotocin and vasotocin, two neurohypophysial hormones in the ostrich, Struthio camelus
Authors: SAAYMAN HESTA S. , NAUDÉ RYNO J. , OELOFSEN WILLEM , ISAACSON LEON C.
Published: August 2010

Two neurohypophysial hormones have been isolated from an avian species, the ostrich, Struthio camelus. Both have been characterized by amino acid analysis and sequence determination. The data obtained suggest that the oxytocin‐like hormone is [Ile8‐oxytocin] (mesotocin) and the vasopressin‐like hormone is [Ile3‐vasopressin] (vasotocin). Bioactivity measurements based on urinary conductivity showed vasotocin to be about five times as active as mesotocin.
Independent folding of autolytic fragments of thermolysin and their domain‐like properties
Authors: CORBETT RONALD J.T. , ROCHE RODNEY S.
Published: August 2010

High molecular weight autolysis products from thermolysin have been isolated and identified. The primary fragments correspond to residues 1 to 187–204 (21kD) and residues 187–204 to 316 (12kD), respectively. The fragments are both capable of independent refolding upon removal of denaturant. On the basis of these results, we suggest that the first step in the unfolding pathway of thermolysin involves unfolding of an interdomain region and domain separation. Bound calcium ions at sites 1, 2 and 4 play a major role in protecting the protein against both autolysis and unfolding, probably by stabilizing the interdomain region and enhancing domain‐domain interactions.
Elephant growth hormone. Isolation and characterization
Authors: LI CHOH HAO , BEWLEY THOMAS A. , CHUNG DAVID , OOSTHUIZEN MATHYS M.J.
Published: August 2010

Growth hormone has been purified to homogeneity from elephant pituitary glands. It has 191 amino acids with two disulfide bridges and a single tryptophan residue. The somatotropin activity is only 15% when compared with the bovine hormone in the radioreceptor binding assay. From circular dichroism spectra α‐helical content of elephant growth hormone is estimated to be 50%. Difference absorption spectra of the hormone suggest the presence of a hydrogen bond between the single Trp and a carboxylate ion.
Structure and conformation of linear peptides. X. Structure of glycyl‐glycyl‐L‐phenylalanine hydrochloride
Authors: MURALI R. , SUBRAMANIAN E.
Published: August 2010

The crystal structure of a tripeptide, glycyl‐glycyl‐L‐phenylalanine HCl (C13H18N3O4 ± HCl, molecular weight = 316.5) has been determined. The crystals are orthorhombic, space group P212121, with a = 4.877 (2) Å, b = 9.956(3), c = 32.690(5) and Z = 4. The final R‐index is 0.043 for 1325 reflections (sinØ/Λ ± 0.55 Å‐1) with I > 2.0 s̀ (I). The N‐terminal of the molecule is protonated and the C‐terminal exists in an un‐ionised state. The peptide units are trans and one of them shows significant deviations from planarity (¶Δω1¶ = 11.3°). The peptide backbone is folded with torsion angles of: ø1 = 165.5°, ω1 = — 168.7°, ø2 = 63.6°, ø2 = — 153.6°, ω2 = 176.5°, ø3 = — 72.2° and Φ3 = 166.5°. For the side chain of phenylalanine, X1 = — 79.5° and X2 = 86.8°. An intramolecular water bridge links the two ends of the molecule.
Cystine peptides. Spectroscopic studies on the conformations of a cyclic pentapeptide disulfide
Authors: KISHORE R. , RAGHOTHAMA S. , BALARAM P.
Published: August 2010

The model cyclic pentapeptide disulfide Boc‐Cys‐Ala‐Aib‐Gly‐Cys‐NHMe 1, has been synthesized. 1H n.m.r. studies in (CD3)2SO and CDCl3‐(CD3)2SO mixtures establish the solvent exposed nature of the Cys(l) and Aib NH groups, while a moderate degree of shielding is observed for the other four NH groups. Nuclear Overhauser effects between Cα1H and Ni+1H protons provide evidence for extended or semi‐extended conformations (ø ± 130° ± 30°) at the Cys(l), Ala(2), Gly(4) and Cys(5) residues. The n.m.r. results are supportive of an intramolecular antiparallel β‐sheet conformation at these residues, nucleated by a γ‐turn centered at Aib(3). This conformation is not stabilized by strong transannular hydrogen bonds. CD studies establish solvent dependent structural changes of the disulfide linkage in methanol‐dioxane mixtures. An unusual CD pattern is observed for the peptide chromophore.