bluuebunny/crossref_metadata_2025 huggingface dataset:
Isolation, characterization and primary structure of two γ‐ variants from ostrich pituitary glands
Authors: LITTHAUER DEREK , NAUDÉ RYNO J. , OELOESEN WILLEM
Published: August 2010

Two γ‐LPH variants have been isolated from ostrich pituitary glands using acid acetone extraction, salt fractionation, ion exchange and gel permeation chromatography and HPLC. The two fractions appeared homogeneous on PAG‐IEF (pI = 4.7) and both displayed an alanine N‐terminal residue. Amino acid composition and fragmentation data for these two peptides are in agreement with that expected for the N‐terminal 44 and 46 amino acid residues in ostrich β‐LPH, with corresponding molecular masses of 4911 and 5154 respectively. The molecular mass of the smaller variant was confirmed by means of sedimentation equilibrium centrifugation to be 4717. The two variants displayed lower lipolytic potencies than the corresponding peptides from other species.
Synthesis and biological activity of monothionated analogs of leucine‐enkephalin
Authors: LAJOIE GILLES , LÉPINE FRANÇOIS , LEMAIRE SIMON , JOLICOEUR FRANÇOIS , AUBÉ CARL , TURCOTTE ANDRÉE , BELLEAU BERNARD
Published: August 2010

The synthesis of the four regioisomers of monothionated Leu‐enkephalins (Leu‐Enk) from previously reported protected precursors is described. The Tyr1‐thio analog was obtained as a 1:1 mixture of the L‐ and D‐Tyr diastereomers. The pure compounds were tested for opiate‐like activity by using the guinea‐pig ileum (GPI) and mouse vas deferens (MVD) preparations, by assessing analgesic effects following intra‐cerebroventricular administration and by examining their ability to displace [3H]‐D‐Ala2, D‐Leu5‐enkephalin (DADLE) and [3H]‐dihydromorphine from rat brain homogenates. The results demonstrate that depending on the backbone position of the thioamide function, activity can be decreased or increased. In the smooth muscle preparations as well as in the opiate binding tests, the activity of D, L‐Tyr1‐thio‐Leu‐Enk and Gly3‐thio‐Leu‐Enk was reduced. The activity of the latter analog was also diminished in the analgesia test. In all biological assays, Phe4‐thio‐Leu‐Enk was either equally or slightly less potent than the parent compound. However, introduction of the sulfur atom in position 2 of Leu‐Enk increased the potency of the compound in all assays, the MVD assay being the most sensitive. The results are interpreted in terms of the thioamide (amide) function in receptor recognition processes, the probable behavior of thiopeptides toward physiologically relevant peptidases and the structural divergences between tissue‐specific receptors.
Synthesis of peptide inhibitors of human spleen fibrinolytic proteinase (SFP) and human leukocyte elastase‐like proteinase (ELP)
Authors: OKADA YOSHIO , TSUDA YUKO , NAGAMATSU YOKO , OKAMOTO UTAKO
Published: August 2010

Stereoisomers of specific substrates for SFP and ELP, Suc‐L‐Tyr‐L‐Leu‐L‐Val‐pNA and Suc‐L‐Ala‐L‐Tyr‐L‐Leu‐L‐Val‐pNA, were synthesized by the conventional solution method. Suc‐L‐Tyr‐D‐Leu‐D‐Val‐pNA was found to be an effective and specific inhibitor of SFP and ELP. Suc‐L‐Tyr‐L‐Leu‐L‐Val‐Pipe and Suc‐L‐Tyr‐D‐Leu‐D‐Val‐Pipe inhibited only SFP very slightly and showed no inhibitory effect on ELP. Both Dan‐L‐Tyr‐L‐Leu‐L‐Val‐pNA and Dan‐L‐Tyr‐D‐Leu‐D‐Val‐pNA exhibited an inhibitory effect on both SFP and ELP.
Synthetic derivatives and analogues of γ‐L‐glutamyl‐taurine, a bioactive compound from bovine parathyroids
Authors: GULYÁS J. , HORVÁTH A. , FURKA Á. , SEBESTYÉN F. , FEUER L.
Published: August 2010

γ‐L‐Glutamyl derivatives and a β‐L‐aspartyl derivative of different amines (taurine, nortaurine, N‐methyltaurine, taurine amide, tauryl‐methylamine, tauryl‐piperidine, β‐alanine amide, orthanilic acid, 2‐aminoethanephosphonic acid, ethanolamine‐O‐sulfate and ethanolamine‐O‐phosphate) have been synthesized by mixed anhydride or active ester coupling method. One of the dipeptide analogues, γ‐L‐glutamyl‐(ethanolamine‐O‐sulfate) was prepared by esterification, too. Syntheses of α,γ‐L‐glutamyl‐bis‐taurine and of DL‐2‐amino‐8‐sulfo‐octanoic acid are also described.
Conformational study of neurotensin
Authors: FINN P.W. , ROBSON B. , GRIFFITHS E.C.
Published: August 2010

The conformation of the biologically‐active tridecapeptide, neurotensin, has been predicted by a procedure including a continuum method for solvent effects on conformation. The neurotensin conformation is described as a β‐type chain with breaks or “corners” most obvious at Tyr3, Asn5, Lys6, Arg8 and Tyr11. The general problem of predicting conformation of larger peptides is emphasized by comparison of the structures of neurotensin and its fragments obtained by other workers with the calculation carried out here on the entire molecule including the effects of the solvent‐dependent reaction field. This inclusion of the reaction field leads to a further, equally‐plausible conformation, which is more justifiable physically as well as in terms of the pharmacological data available on neurotensin. Factors leading to different residue conformations and the relative merits of the different results obtained are analyzed in some detail to cast further light on the aspects that must be considered in the analysis and design of biologically‐active analogues of neurotensin.
Synthesis of shrimp red pigment‐concentrating hormone analogs and their biological activity in locusts
Authors: Yamashiro Donald , Applebaum Shalom W. , Li Choh Hao
Published: August 2010

Two analogs of the red pigment‐concentrating hormone (RPCH) have been synthesized by the solid‐phase method: [Thr6]‐RPCH (I) and [Tyr4, Thr6]‐RCPH (II). Analog I has the same amino acid composition as the second adipokinetic hormone (AKH‐II) isolated from locust corpora cardiaca. Bioassay for lipid‐mobilizing activity in adult male locusts gave the following increases in hemolymph lipid content: AKH‐I, 3.5; I, 2.4; II, 2.9. The biological response shown by I lends support to the conclusion that its sequence is that of the presumptive AKH‐II. Replacement of Phe in position 4 by Tyr does not reduce the adipokinetic response.
Conformational properties of the pentapeptide fragment [32–36] of the thymic hormone thymopoietin
Authors: Tourwe D. , De Coen J.L. , Hallenga K. , Van Binst G.
Published: August 2010

The conformational energy for the pentapeptide Arg‐Lys‐Asp‐Val‐Tyr (TP5) is calculated using empirical potential functions. Calculation of the local interactions for each independent residue gives a local energy term for which the probabilities as a function of ø, ø are plotted on Ramachandran‐type maps. The interaction energy between residues is calculated only for these points in the maps with maximum probability. The most probable conformation for TP5 is found to have an extended backbone arrangement having the Arg and Tyr side‐chains folded over the backbone. 13C n.m.r. spin lattice relaxation time measurements show no increase in T1 of the α‐carbons at the first and terminal amino acids. The increase in T1 along the sidechain as found for Lys does not occur for Arg and Tyr. These signs of reduced mobility are consistent with a set of folded conformations in which the Arg and Tyr sidechains have hindered internal rotations. The vicinal NH‐CαH couplings agree well with those calculated for the most probable conformer. This is not so for the CαH‐CβH couplings. These data are consistent with previous n.m.r. and structure activity studies.
Crystal and molecular structure of N‐α‐acetyl‐L‐arginine‐methyl ester hydrochloride
Authors: Coll M. , Solans X. , Font‐Altaba M. , Subirana J.A.
Published: August 2010

The crystal structure of N‐α‐acetyl‐L‐arginine‐methyl ester hydrochloride has been determined from X‐ray diffraction data. The crystals are orthorhombic, space group P212121, a = 15.746 (4), b = 11.569 (4), c = 7.158 (3) Å, Z = 4. The structure was solved by direct methods (MULTAN) and refined by fullmatrix least‐squares to an R = 0.070 for all observed reflections. The molecule shows a planar peptidic unit, with a distortion of H(N1) due to hydrogen bond interaction. The side chain is in the low energy all‐trans conformation. The guanidinium group forms three hydrogen bonds with the carbonyl oxygens of two neighbouring molecules. A direct interaction of the peptidic NH with the chloride ions is observed. The latter ions also interact with the guanidinium groups, neutralizing their charges.
Biologically active conformation of tuftsin
Authors: Nikiforovich G.V. , Liepina I.T. , Sekacis I.P. , Liepins E.E. , Katayev B.S. , Veretennikova N.I. , Chipens G.I.
Published: August 2010

The main features of the assumed biologically active conformation of the tuftsin molecule have been described using the energy calculations as well as the n.m.r. and CD‐spectroscopy measurements performed for the conformationally rigid active cycloanalogue, Thr‐L‐ys‐Pro‐Arg. The biologically active conformation has been shown to be of BBRB or BLRB backbone type with the trans‐conformation of proline residue.
Primary structure of tryptophan‐containing peptides from skin extracts of Phyllomedusa rhodei (tryptophyllins)
Authors: Montecucchi Pier Carlo , Gozzini Luigia , Erspamer Vittorio , Melchiorri Pietro
Published: August 2010

A new conspicuous set of peptides has been isolated from the skin of Phyllomedusa rhodei, a South American frog. All these peptides contain a tryptophyl residue, which justifies the suggested denomination of tryptophyllins (TPH). On the basis of their chain length, they were classified as TPH‐4, TPH‐5, etc. The peptides, described in this paper, have been isolated from the 95% ethanol eluate from an alumina column. They are tetra‐ and pentapeptide amides showing the characteristic sequences <Glu‐Pro‐Trp‐Xxx (Xxx = Val, Met) and Phe‐Pro‐Pro‐Trp‐Xxx (Xxx = Val, Leu, Met), respectively.
Comparison of Cyssor analogues in the cysteine‐specific chemical cleavage of ovalbumin
Authors: Holmes Thomas J. , Lawton Richard G.
Published: August 2010

A comparison of analogous benzoquinonediimide protein cleavage reagents is presented. While the 2‐methoxy derivative reveals no apparent advantage over the previously reported 2‐methyl‐N1‐benzenesulfonyl‐N4‐bromoacetyl‐benzoquinonediimide (Cyssor I; Sigma Chemical Company), the 2‐chloro analogue reveals significant cleavage of ovalbumin under identical solvent conditions, but without the application of heat. This improvement might allow application of this chemical cleavage technique to particularly temperature‐sensitive proteins.
Conformation of valinomycin in its barium perchlorate complex from X‐ray crystallography and n.m.r.
Authors: Devarajan S. , Vijayan M. , Easwaran K.R.K.
Published: August 2010

The conformation of the ionophore antibiotic valinomycin in its barium perchlorate complex has been determined in the solid state by X‐ray crystallography and in solution using proton (1H) and carbon‐13 (13C) nuclear magnetic resonance spectroscopy. All our results indicate that both in solution and in the solid state, the valinomycin molecule in the complex stabilizes in a flat open structure, without internal hydrogen bonds, with two bariums per molecule. In the crystals each barium is liganded with three consecutive amide carbonyls and is separated from the other by 4.57 Å. The other atoms coordinating to barium ions belong to perchlorate groups and solvent molecules. The crystal structure contains infinite layers of valinomycin molecules interconnected by perchlorate groups. The solvent molecules in the structure are sandwiched between successive layers. In solution the valinomycin molecules exhibit three‐fold symmetry in the n.m.r. time scale. This observation, along with a careful consideration of steric factors as well as the conformational differences between chemically equivalent residues in the solid state, suggests the presence of many conformers in solution, all clearly related to the one observed in the crystals, interconverting rapidly in the n.m.r. time scale.
Conformation study of neurotensinC‐terminal heptapeptide Pro‐Arg‐Arg‐Pro‐Tyr‐Ile‐LeuOH
Authors: Cotrait Michel
Published: August 2010

The conformational behavior of the activeC‐terminal heptapeptide of neurotensin (NT), Pro‐Arg‐Arg‐Pro‐Tyr‐Ile‐LeuOH, or NT{7–13}, was investigated using empirical energy calculations. A sequential approach was used to display the specific contribution of each residue to induce stable conformations of the whole heptapeptide. The most stable conformations include numerous conformations of various types in a rather limited energy range. There is no preferential conformation contrary to the activeC‐terminal pentapeptide. These structures may coexist in the biological environment.
Dynorphin‐(1–13).
Authors: Turcotte Andree , Lalonde Jean‐Marc , St‐Pierre Serge , Lemaire Simon
Published: August 2010

Dynorphin‐(1–13) (Dyn‐(1–13)) and its analogs substituted by single introduction of Ala in positions 1–11 were synthesized by the solid‐phase method and purified by high pressure liquid chromatography. Relative potencies of the synthetic compounds were determined by their ability to inhibit electrically‐evoked contractions of the guinea pig ileum (GPI) and of the mouse vas deferens (MVD) and to compete with [3H]‐etorphine for opiate receptors in rat brain homogenates. Introduction of Ala in positions 1 and 4 of Dyn‐(1–13) provoked most important decreases in the activity of the molecule in the three assays (relative potency of 0.2% or less). Substitution of Ala in positions 2 or 5, but not 3, also severely decreased the potency of the peptide in the smooth muscle preparations (0.6–5.0% activity). However, the opiate receptor binding assay was less sensitive to the replacement of residue in position 2 (20% activity) than that in positions 3 or 5 (12% and 6% relative potencies, respectively). In the GPI assay and the opiate binding test, the other substitutions which greatly lowered the potency of the molecule were seen in positions 6, 7, 9 and 11, four basic residues. Among these, Arg6and Arg7were demonstrated to be the most important in the three biological tests. Finally, the replacement of Ile8by Ala increased the relative potency of Dyn‐(1–13) up to 191% and 900% in the MVD and the opiate binding tests, respectively.
Denaturation studies on lysozyme by n.m.r. measurements of its inhibitors
Authors: Sheinblatt Mati
Published: August 2010

A method for studying denaturation of an enzyme by n.m.r. measurements of its specific inhibitor is reported and discussed for the case of lysozyme and N‐acetyl glucose amine. It was shown that in the presence of bound inhibitor molecules, the enzyme is more resistant to the denaturant agent as compared to the free enzyme.
Self‐association and solubility of peptides.
Authors: Toniolo C. , Bonora G.M. , Schaaper W.M.M.
Published: August 2010

Self‐associated species of the protected C‐terminal tetrapeptide segment of porcine vasoactive intestinal peptide and related short sequences in methylene chloride have been disrupted by adding increasing amounts of dimethylsulphoxide. This structural transition has been monitored following the disappearance of the amide I carbonyl stretching band assigned to strongly intermolecularly hydrogen‐bonded molecules (1655–1633 cm‐1) in the infrared absorption spectra. A scale for the propensity of the various peptides to aggregate has been established. Substitution of the asparagine residue by a β‐tert.‐butylaspartic acid residue in the tripeptide drastically reduces the extent of self‐association. The increasing tendency to aggregate shown by these peptides is paralleled by a decrease in their solubility. The impact of these results on the strategy of synthesis of porcine vasoactive intestinal peptide is briefly outlined.
Separation of the cellulolytic system of Trichoderma viride‐reesei mutant using medium pressure liquid chromatography and characterization of a new exo‐cellobiohydrolase*
Authors: Hostomské Z. , MikeŠ O.
Published: August 2010

Using a combination of rapid medium pressure ion exchange chromatography on the cation exchanger Spheron Phosphate‐1000 and the anion exchanger Spheron DEAE‐1000 a number of enzyme fractions of the cellulolytic system of a mutant of the imperfect fungus Trichoderma viride‐reesei were isolated from the cultivation medium. One of the fractions, which appeared homogeneous on poly‐acrylamide gel electrophoresis and sedimentation analysis, was prepared on a larger scale. It was a glycoprotein with 7% of neutral sugars, having a molecular weight 66 600 ± 3% and a sedimentation coefficient 4.2 S. Its amino acid composition was determined as well as the N‐terminal amino acid sequence: Glyαa˙Val˙Pro. Since the isolated enzyme hydrolyzed Avicel, filter paper and – to a small extent – carboxymethylcellulose with the main product cellobiose, it was identified as exo‐cellobiohydrolase.
Peptide models for β‐turns.
Authors: Crisma M. , Fasman G.D. , Balaram H. , Balaram P.
Published: August 2010

The circular dichroism spectra of four β‐turn model peptides, Z‐Aib‐Pro‐Aib‐Pro‐OMe (1), Piv‐Pro‐Aib‐NHMe (2), Piv‐Pro‐D‐Ala‐NHMe (3) and Piv‐Pro‐Val‐NHMe (4) have been examined under a wide range of solvent conditions, using methanol, hexafluoroisopropanol and cyclohexane. Type I and Type II β‐turns have been observed for peptides 1 and 2 respectively, in the solid state, while the Pro‐D‐Ala sequence adopts a Type II β‐turn in a related peptide crystal structure. A class C spectrum is observed for 1 in various solvents, suggesting a variant of a Type I (III) structure. The Type II β‐turn is characterized by a CD spectrum having two positive CD bands at ˜ 230 nm and ˜ 202 nm, a feature observed in Piv‐Pro‐D‐Ala‐NHMe in cyclohexane and methanol and for Piv‐Pro‐Aib‐NHMe in methanol. Peptide 2 exhibits solvent dependent CD spectra, which may be rationalized by considering Type II, III and V reverse turn structures. Piv‐Pro‐Val‐NHMe adopts non‐β‐turn structures in polar solvents, but exhibits a class B spectrum in cyclohexane suggesting a population of Type I β‐turns.
A three‐step synthesis of (±)‐β‐methyleneaspartic acid
Authors: Hand Elli Smakula , Baker David C.
Published: August 2010

A simplified, three‐step synthesis for (±)‐β‐methyleneaspartic acid is described. Condensation of diethyl malonate with ethyl pyruvate gives 1,1,2–tricarbethoxyprop‐1‐ene, which is α‐aminated with chloramine to give 1‐amino‐1,1,2‐tricarbethoxyprop‐2‐ene. The latter is hydrolyzed in acid to give the title compound.
D ˙ Ala3 analog of elastin polypentapeptide.
Authors: Urry D.W. , Trapane T.L. , Wood S.A. , Harris R.D. , Walker J.T. , Prasad K.U.
Published: August 2010

The polypentapeptide, H(L˙Val1‐L˙Pro2‐D·Ala3‐L˙Val4‐Gly5)n Val‐OMe which is the D·Ala3 analog of the elastomeric polypentapeptide (PPP) of elastin, (L˙Val1‐L˙Pro2‐Gly3‐L˙Val4‐Gly5)n, has been synthesized. Its conformation is compared to that of the PPP and found to be similar with a somewhat stabilized β‐turn. The D·Ala3 analog coacervates to form a more cohesive viscoelastic material and the coacervate when cross‐linked by γ‐irradiation exhibits an approximate doubling of the Young's modulus of elasticity. These results are discussed in connection with other related analogs of the polypentapeptide of elastin, which are non‐elastomeric, and found to be consistent with a proposed conformationally based librational entropy mechanism of elasticity.
Putative high mobility group (HMG) non‐histone chromosomal proteins from wheat germ
Authors: Mayes E.L.V. , Walker J.M.
Published: August 2010

Four proteins have been isolated from wheat germ by methods analogous to those used to isolate HMG proteins from animal tissue. All four proteins have been shown to be chromosomal in origin. Although amino acid analyses show that three of these proteins have compositions similar to those of the mammalian HMG proteins, N‐terminal sequence analyses of these proteins show an absence of sequence homology with any of the mammalian HMG proteins.
Use of triphenylmethyl (trityl) amino protecting group in the synthesis of ketomethylene analogues of peptides
Authors: JOHNSON RODNEY L. , MILLER ROBERT B.
Published: August 2010

The Grignard reagents of 2‐(2‐bromoethyl)‐1,3‐dioxane and 2‐(2‐bromoethyl)‐1,3‐dioxolane readily reacted with the 2‐thiopyridyl ester of N‐triphenylmethyl‐l‐leucine to give the ketone adducts 2‐[3‐oxo‐4(S)‐(triphenylmethyl) amino‐6‐methylheptyl]‐1,3‐dioxane (8a) and 2‐[3‐oxo‐4(S)‐(triphenylmethyl) amino‐6‐methylheptyl]‐1,3‐dioxolane (8b) in near quantitative yield. When 1 equiv. of the Grignard reagent of 2‐(2‐bromoethyl)‐1,3 dioxane was used, the desired ketone adduct 8a was formed slowly but quantitatively. In contrast, when 2 equiv. of the Grignard reagent were used, the formation of ketone 8a was instantaneous. The triphenylmethyl protecting group was easily removed from 8a using dilute acid to give the amino ketone 2‐[3‐oxo‐4(S)‐amino‐6‐methylheptyl]‐1,3‐dioxane oxalate salt (9). This material served as a useful intermediate in the synthesis of the ketomethylene analogues of the peptides, Z‐Pro‐Leu‐Gly‐OH and Leu‐Gly‐Val‐Phe‐OCH3.
Carbonyl‐17O n.m.r. of amino acid and peptide carboxamide and methyl ester derivatives§
Authors: STEINSCHNEIDER A. , FIAT D.
Published: August 2010

Specific carbonyl enrichment with 17O of amino acid OMe esters by up to 103 times over natural abundance was affected by treating [17O]‐α‐COOH amino acids with SOCl2 in MeOH. Carbonyl‐[17O]‐Gly‐NH2, Gly‐NHCH3 and Gly‐N(CH3)2 were obtained from [17O]‐Gly‐OMe by (methyl)aminolysis with NH3, CH3NH2 and (CH3)2NH gases respectively. Peptide [17O]‐carboxamides were prepared by (methyl)aminolysis of Z‐Pro‐Leu‐[17O]‐Gly‐OMe followed by catalytic hydrogenation to remove the Z group. 17O chemical shifts of amino acid and peptide carboxamides in H2O, MeOH, CH3CN and DMSO were 260–324 p.p.m. downfield relative to H2O, depending on α‐NH2 ionization, substitution on both amino groups and solvent H bonding, primarily to amide oxygen. Introduction of an amide‐N methyl group usually caused upfield shifts (approx. – 10 p.p.m.), attributed to elimination of one NH bond, while a second N methylation had the opposite effect. Amino acid and peptide OMe ester carbonyl‐[17O] resonances appeared 326–359 p.p.m. downfield relative to H2O reflecting on side chain interactions, state of α‐NH2 ionization and H‐bonding with the solvent. Effective rotational correlation times for glycine and peptide carboxamide‐[17O], calculated from T2 relaxation data, were of similar magnitude to values derived from solution properties and depended on the molecular weight and solvent viscosity.
Molecular mechanics study of ion binding by a cyclic pentapeptide
Authors: LYNN THOMAS E. , KUSHICK JOSEPH N.
Published: August 2010

We have used energy minimization and harmonic analysis to study the structural and thermodynamic changes which occur upon the binding of lithium ions to the cyclic pentapeptide, cyclo‐(Gly‐L‐Pro‐Gly‐D‐Ala‐L‐Pro) (GPGAP). A number of theoretically stable vacuum configurations of uncomplexed GPGAP were found, one of which is very close to the crystal conformation determined by X‐ray diffraction. Stable complexes with lithium were found where the ion binds to the carbonyl oxygen atoms of three residues. Detailed conformational information is presented for both the uncomplexed and the complexed peptide, along with an analysis of the atomic interactions which stabilize the various peptide conformations.
Comparative biological activities of potent active‐site analogues of α‐melanotropin. Effect of tyrosine substitution at position‐4
Authors: WILKES BRIAN C. , SAWYER TOMI K. , HRUBY VICTOR J. , HADLEY MAC E.
Published: August 2010

We have prepared several α‐melanotropin (α‐MSH) analogues with tyrosine substituted for methionine at the 4‐position and determined their melanotropic activities on the frog (Rana pipiens), lizard (Anolis carolinensis) and S‐91 (Cloudman) mouse melanoma adenylate cyclase bioassays. The potencies of Ac‐[Tyr4]‐α‐MSH4–10‐NH2 and Ac‐[Tyr4]‐α‐MSH4–11‐NH2 were compared with α‐MSH and with their corresponding methionine and norleucine substituted analogues. The Tyr‐4 analogues were found to be less active than the Nle‐4 analogues on both the frog and lizard assays. Ac‐[Tyr4]‐α‐MSH4–10‐NH2 was found to be less active than Ac‐[Tyr4]‐α‐MSH4–11‐NH2 on the lizard bioassay, but more active than the longer fragment on the frog skin assay. Ac‐[Tyr4]‐α‐MSH4–10‐NH2 exhibited extremely prolonged biological activity on frog skin, but not on lizard skin, while the melanotropic activity of Ac‐[Tyr4]‐α‐MSH4–11‐NH2 was rapidly reversed on both assay systems. The increased potency of Ac‐[Tyr4]‐α‐MSH4–10‐NH2 over Ac‐[Tyr4]‐α‐MSH4–11‐NH2 on frog melanocytes may be related to the fact that the shorter 4–10 analogue exhibits prolonged biological activity. Interestingly, it was found that both Tyr‐4 analogues were partial agonists on the mouse melanoma adenylate cyclase bioassay, and stimulated the enzyme to only about 50% of the maximal activity of α‐MSH. We reported previously that replacement of L‐Phe‐7 by its D‐enantiomer in [Nle4]‐α‐MSH and its Nle‐4 containing analogues resulted in peptides with increased potency and in some instances prolonged activity. Similarly, incorporation of D‐Phe‐7 into Tyr‐4 containing melanotropin fragments produced analogues Ac‐[Tyr4, D‐Phe7]‐αMSH4–10‐NH2 and Ac‐[Tyr4, D‐Phe7]‐α‐MSH4–11‐NH2, which also exhibited greatly increased biological activity in all three assay systems. Both of these analogues were also found to have prolonged activity in the frog skin bioassay but little or no prolonged activity in the lizard skin bioassay. These two analogues turned out to be full agonists in the mouse melanoma adenylate cyclase bioassay and were equipotent to α‐MSH. These results demonstrate that substitution of tyrosine for methionine at position‐4 dramatically affects the potency and prolonged activity of these melanotropin analogues and the melanotropic activities observed as a result of such substitutions are themselves affected by concomitant substitutions at the 7(Phe) and 11 (Lys) positions of the analogues.
Synthesis of N‐(2‐chloroethyl)‐N‐nitrosocarbamoyl derivatives of biologically active polypeptide hormone fragments
Authors: SÜLI‐VARGHA HELGA , MEDZIHRADSZKY KÁLMÁN
Published: August 2010

N‐(2‐chloroethyl)‐N‐nitrosocarbamoyl derivatives of α‐melanotropin and gastrin fragments were synthesized by the acylation of the peptides with active esters of N‐(2‐chloroethyl)‐N‐nitrosocarbamic acid. These compounds are supposed to be antitumor agents of low toxicity and increased selectivity.
Cyclic melanotropins
Authors: LEBL M. , CODY W.L. , WILKES B.C. , HRUBY V.J. , CASTRUCCI A.M. DE L. , HADLEY M.E.
Published: August 2010

The highly potent cyclic analogue of α‐MSH, Ac‐[Cys4, Cys10]‐α‐MSH4–13‐NH2, was structurally modified in position 4. Four analogues were prepared and their biological activities in the in vitro frog and lizard skin bioassays were determined. It was shown that removing the terminal acetylamino group to give [Mpa4, Cys10]‐α‐MSH4–13‐NH2 resulted in little change in the biological activity, but a change in the stereochemistry of cysteine in position 4 to give Ac‐[D‐Cys4, Cys10]‐α‐MSH4–13‐NH2 led to a small decrease of activity in both bioassays. Decreasing the size of the intramolecular ring by removing one methylene group to give [Maa4, Cys10]‐α‐MSH4–13‐NH2, resulted in an analogue with lower activities in both assays (about 3 times in the lizard and 500 times in the frog), and increasing the size of the ring by one methylene group to give Ac‐[Hcy4, Cys10]‐α‐MSH4–13‐NH2 led to much lower activities in the lizard system and similar effects were seen upon decreasing the ring size in the frog skin assay.
Human β‐endorphin
Authors: YAMASHIRO DONALD , WESTPHAL MANFRED , LI CHOH HAO
Published: August 2010

Three analogs of human β‐endorphin (βh‐EP) have been synthesized by the solid‐phase method: [Phe3, Gly4]‐βh‐EP (I), [Tyr5]‐βh‐EP (II), and [Trp5]‐βh‐EP (III). Analogs I and II are related to the highly potent hybrid analog [dermorphin1–7]‐βc‐EP (βc‐EP is camel β‐EP). Radio‐receptor‐binding and analgesic assays gave relative potencies as follows, respectively: βhEP, 100, 100; I, 51, 43; II, 64, 30; III, 15, 4. The high potency of [dermorphin1–7]‐βc‐EP is not due to any one of the following structural elements: D‐Ala2, Phe3‐Gly4, Tyr5, and Pro6. Increasing hydrophobicity in position 5 (Met in β‐EP) leads to decreasing biological activity.
Normal modes of vibration of a model peptide adopting the C7 C5 structure
Authors: LAGANT P. , VERGOTEN G. , FLEURY G. , LOUCHEUX‐LEFEBVRE M.H.
Published: August 2010

A normal coordinate treatment was performed on the C7C5 conformation using a modified Urey‐Bradley force field refined from previous studies on β‐turns. The predicted frequencies were compared with the experimental ones obtained on the peptide hormone human angiotensin II. The existence of both a β‐turn and a C7C5 conformation in solid and in aqueous solution is discussed.
Studies on β‐turn of peptides
Authors: KAWAI MASAO , SATO KAZUKI , NAGAI UKON
Published: August 2010

A conformational energy study was performed upon the effect of replacement of the Gly of Ac‐Gly‐AA2‐AA3‐Gly‐NHCH3 by L‐ or D‐Ala when AA2‐AA3 part forms a turn conformation. When D‐Ala‐L‐Pro constitutes the AA2‐AA3 moiety, L‐Ala at the 1st and 4th positions favor a β‐turn conformation of the tetra‐peptide, while D‐Ala residues at these positions do not. In the case of L‐Pro‐L‐Ala at the AA2‐AA3 position, the effect of replacing the two Gly residues by L‐or D‐Ala was shown to be just the opposite to that calculated for the D‐Ala‐L‐Pro sequence. Terminal Gly residues are always allowable for β‐turn conformation.
Time‐dependent ultraviolet absorption changes in proteins at high pH
Authors: GRUEN L.C. , TAO Z.‐J.
Published: August 2010

The effect of alkali on the ultraviolet absorption of several proteins was examined by difference spectrophotometry. In addition to the well known generation of phenolate ions from tyrosine, time‐dependent changes occurred. These were relatively slow in water, but arose more quickly and to a greater degree in 6 M guanidine hydrochloride. These time‐dependent changes were attributed to modification of the sulfur‐containing amino acids, cystine and cysteine. The magnitude of the changes depended on the number and accessibility to solvent of the cystine, cysteine or derivatized species present. The increase in absorption at 295 nm typically reached a maximum value for disulfide containing proteins after ca. 1 h exposure to pH > 12 in 6 M guanidine hydrochloride; thereafter the changes were at least partially reversible. Taken in conjunction with amino acid analysis data, the results lend support to the β‐elimination mode of action of alkali on proteins. However the reaction mechanism appears to be complex and more than one chromophore, arising from more than one reaction pathway, seems to be involved in the alkaline degradation of the sulfur‐containing amino acids. Particularly for proteins containing large amounts of cystine or cysteine, caution must be exercised when performing tyrosine titration experiments in order to recognize and minimize potential interference from other non‐tyrosine related chromophores.
DNA‐binding compounds – synthesis and intercalating properties of a peptide‐diamino diacridine
Authors: KELLY DAVID P. , MACK PHILIP O‐L. , MARTIN ROGER F. , WAKELIN LAURENCE P.G.
Published: August 2010

A novel diacridine has been prepared in which two acridines are linked by a flexible peptide chain composed of γ‐aminobutyric acid, tyrosine, lysine and glycine. Synthesis of N‐(9‐acridinyl)‐4‐aminobutanoyl‐tyrosyl‐lysyl‐lysyl‐glycyl)‐N′‐(9‐acridinyl)‐1,3‐diaminopropane (VII) was achieved in 8% overall yield by a solution phase stepwise procedure. This compound binds to DNA by intercalation of both chromophores with at least a 140‐fold enhancement of affinity compared to 9‐aminoacridine.
Isolation and characterization of a neurophysin from ostrich neurohypophyses
Authors: SAAYMAN HESTA S. , NAUDE RYNO J. , OELOFSEN WILLEM
Published: August 2010

A neurophysin has been isolated from ostrich neurohypophyses using acid acetone extraction, salt fractionation and Sephadex G‐75 chromatography. The crude neurophysin eluting from the Sephadex G‐75 column was subjected to a) reverse‐phase HPLC followed by Sephadex G‐75 chromatography, b) DEAE‐Sephadex A‐50 chromatography or c) isoelectric focusing. The different homogeneous ostrich neurophysin fractions so obtained were compared i.t.o. amino acid composition, spectral properties,N‐terminal amino acid residues and PAGE. They all revealed a singleN‐terminal Ala residue and displayed spectral properties (A280/A260< 1) which are typical of mammalian neurophysin‐like polypeptides. Ultracentrifugation studies on purified ostrich neurophysin over a range of concentrations revealed a reversible concentration dependent association behaviour characterized by the presence of dimeric complexes at higher concentrations. Partial sequencing from theN‐terminus revealed the molecule to be VLDV‐like. The purified molecule was also submitted to CNBr fragmentation.
Use of high‐performance size‐exclusion chromatography to measure protein molecular weight and hydrodynamic radius
Authors: TARVERS RICHARD C. , CHURCH FRANK C.
Published: August 2010

We have conducted a study of the TSK 3000 SW high‐performance size‐exclusion column to define under what conditions proteins would migrate most consistently with their known hydrodynamic properties. Our findings include the following: 1) the residual negative charge of the column does cause charge‐exclusion or charge‐retention effects at low ionic strengths; with elution in deionized water several anionic proteins elute approximately in the void volume; 2) at μ > 0.5, protein migration is not only independent of ionic strength, but consistent with protein molecular weight and hydrodynamic volume; 3) small hydrophobic peptides are retarded by the column; and 4) very asymmetric proteins and other hydrodynamic particles are likely to be retarded by an “end‐on insertion” mechanism.
Studies of peptide antibiotics. XLVI. Syntheses of gramicidin S analogs containing D‐α, β‐diaminopropionic acid or α,β‐dehydroalanine*
Authors: ANDO SHOJI , KATO TETSUO , IZUMIYA NOBUO
Published: August 2010

A gramicidin S (GS) analog ([d‐Dpr4,4] GS) containing d‐α,β‐diaminopropionic acid (D‐Dpr) in place of D‐Phe at 4,4′ positions was derived from [l‐Orn(δ‐formyl)2,2, d‐Dpr(β‐Z)4,4′]GS, which was synthesized by conventional method in solution. An analog [ΔAla4,4′]GS was synthesized from [l‐Orn(δ‐Boc)2,2′, d‐Dpr4,4′]GS through Hofmann degradation of the d‐Dpr residues. Antimicrobial activities of these analogs were tested; [d‐Dpr(β‐Z)4,4′]GS and [ΔAla4,4′]GS showed high antimicrobial activities against Gram‐positive bacteria. [d‐Dpr4,4′]‐GS showed an appreciable activity against Gram‐negative bacteria such as Escherichia coli. Four semigramicidin S (semiGS) analogs such as [ΔAla4]semiGS were synthesized; these had no antimicrobial activity. Analogs containing ΔAla residues were hydrogenated, and the formation of l‐Ala or d‐Ala residues was determined. The ΔAla residues in [ΔAla4,4′] GS were reduced to dl‐Ala, and ΔAla in [ΔAla4]semiGS mostly to l‐Ala. The relationships of the antimicrobial activity, CD curves and asymmetric hydrogenation to the structure were discussed.
NH resonances of Ribonuclease S‐peptide in aqueous solution. Low temperature n.m.r. study
Authors: NIETO J.L. , RICO M. , SANTORO J. , BERMEJO J.
Published: August 2010

A detailed study of the NH resonances of Ribonuclease‐S‐peptide (1–19 N‐terminal fragment of Ribonuclease A) has been carried out in H2O, pH 3.0, in the temperature range 1–31, and ionic strength 0–1 M. Individual assignments of all NH amide signals have been achieved by means of extensive double resonance experiments. The folding of S‐peptide at low temperature has been monitored by examination of the several NH resonance parameters: first, the non‐linearity of chemical shift vs. temperature plots; second, the selective broadening observed for signals assigned to residues 3–13; and third, the decrease of 3JHNCH coupling constants belonging to this region of the polypeptide chain. All these results are in agreement with the formation of a folded structure at low temperature, which is similar to the one found for the S‐peptide in the RNase S crystal.
New bovine adrenal medullary peptide and its precursor
Authors: BRANDAU DUANE T. , RAY PURNIMA , STERN ALVIN S. , LEWIS RANDOLPH V.
Published: August 2010

We have isolated a previously unknown peptide and its precursor from bovine adrenal medullary chromaffin granules. The peptide sequence is Leu‐Pro‐Val‐Asn‐Ser‐Pro‐Met‐Asn‐Lys‐Gly‐Asn‐Glu‐Val‐Met‐Lys. The peptide is cleaved from the precursor at a Lys site. The sequence shows no homology to any known protein in the largest sequence data bank available.
Peptide binding by a micellar polymer of 10‐undecenoate
Authors: HOLLADAY LESLIE A. , TEMPLE LOUISE M.
Published: August 2010

A micelle‐like polymer of 10‐undecenoate was prepared by γ‐irradiating micellar solutions in 1 M NH4HCO3. The polymer was characterized with respect to its Stoke's radius, molecular weight, and intrinsic viscosity. The hydrodynamic data are consistent with a fairly compact molecule of molecular weight 6000. The binding of several tryptophanyl‐containing peptides to the polymer was examined using difference spectroscopy.
Bilirubin binding to polypeptides and chiral amines. Induced circular dichroism and fluorescence studies
Authors: MARR‐LEISY DEBRA , LAHIRI KASTURI , BALARAM P.
Published: August 2010

Induced Cotton effects have been observed in the visible region on interaction of bilirubin with chiral mono‐ and diamines and poly‐l‐lysine. At alkaline pH distinct CD spectra are observed for bilirubin bound to the α‐helical and β‐sheet conformation of poly‐l‐lysine, which differ from that observed for the pigment bound to human serum albumin. The CD pattern observed on binding toN‐acetyl‐Lys‐N1‐methylamide in CH2Cl2and dioxane is different from that observed in the presence ofl‐Ala‐NH‐(CH2)6‐NH‐l‐Ala in dioxane. The latter case resembles the spectrum observed in the presence of human serum albumin. Binding to the helical polypeptide melittin and the antiparallel β‐sheet peptide, gramicidin S, in aqueous solutions results in opposite signs of the bilirubin CD bands. The quenching of tryptophan fluorescence in melittin, in aqueous solution and enhancement of bilirubin fluorescence in dioxane on binding to gramicidin S have been used to monitor pigment‐peptide interactions. The results suggest the utility of bilirubin as a conformational probe.
Synthesis of tryptophyllin‐7 and analogues
Authors: PERSEO GIUSEPPE , GIGIL MAURO , DE CASTIGLIONE ROBERTO
Published: August 2010

Syntheses by solution methods of tryptophyllin‐7 (H‐Val‐Pro‐Pro‐Leu‐Gly‐Trp‐Met‐OH), a heptapeptide isolated from skin extracts of Phyllomedusa rhodei, and its methyl ester and amide are reported. Preliminary biological results in rats seem to indicate a growth promoting activity for both the acid and the ester derivative.
Conformational preferences and binding to neurophysins of oxytocin analogs with sarcosine or N‐methylalanine in position 7
Authors: GRZONKA ZBIGNIEW , MISHRA P.K. , BOTHNER‐BY A.A.
Published: August 2010

The 600 MHz proton n.m.r. spectra of (sarcosyl7)‐oxytocin and (N‐methylalanyl7) oxytocin in 2H2O solution have been recorded and completely assigned. In each case the spectrum indicates the presence of two slowly interconverting conformers, which are the cis‐trans isomers about the peptide bond between residues six and seven. The trans isomer is energetically favored in both cases. When neurophysin is added to a solution of (N‐methylalanyl7) oxytocin or (sacrosyl7)‐oxytocin at pH 3.0, the proportion of minor conformer remains constant, indicating that the cis and trans conformers are equally tightly bound to the protein.
HPLC‐studies on nonmercapt‐mercapt conversion of human serum albumin
Authors: SOGAMI MASARU , ERA SEIICHI , NAGAOKA SHUNJI , KUWATA KAZUO , KIDA KIMIHIRO , MIURA KIYOSHI , INOUYE HIROSHI , SUZUKI EIJI , HAYANO SHIGEO , SAWADA SHIGEKI
Published: August 2010

Human mercaptalbumin (HMA) and nonmercaptalbumin (HNA) could be separated by high‐performance liquid chromatography (HPLC) at neutral pH. Using HPLC, the present authors found the nonmercapt‐mercapt conversion (HNA ← HMA) during hemodialysis and the mercapt‐nonmercapt conversion (HMA ← HNA) after hemodialysis in chronic renal failure, indicating HMA as the covalent carrier protein for sulfur‐containing amino acids.
Solid phase synthesis of two cholera toxin B subunit antigens
Authors: DELMAS A. , GUYON‐GRUAZ A. , HALIMI H. , RAULAIS D. , RIVAILLE P.
Published: August 2010

The 30–50 and 50–75 sequences of the cholera toxin β chain including the amino‐acids that are thought to be involved in toxin‐receptor binding have been synthesized using the solid phase method. They were then purified by gel permeation and ion exchange chromatography. Both these free peptides induced serum antibodies recognising the native toxin after oral or intraperitoneal administration. Only the antibodies raised against the 50–75 peptide, however, were able to neutralize toxin activity.
Self‐association and solubility of peptides. Solvent‐titration study of protected C‐terminal segments of porcine secretin*
Authors: TONIOLO C. , BONORA G.M. , MORETTO V. , BODANSZKY M.
Published: August 2010

Self‐association of peptides (related to the C‐terminal sequence of porcine secretin) in methylene chloride was disrupted by adding dimethylsulfoxide in increasing amounts. This structural transition was monitored by the disappearance of the amide‐I C = O stretching band of strongly intermolecularly hydrogen‐bonded molecules (1625–1630 cm‐1) in the infrared absorption spectra. The effects induced by main‐chain length and sequence, type of Nα‐protection, and concentration were assessed. Hexamethylphosphortriamide was compared for its structure‐disrupting properties to dimethylsulfoxide. The increasing propensity to aggregate displayed by these peptides is paralleled by a decrease in their solubility. The impact of these results on the planning of peptide syntheses is briefly discussed.
Anti‐writhing activity of some peptides related to neurotensin and tuftsin
Authors: NICOLAIDES E.D. , LUNNEY E.A. , KALTENBRONN J.S. , WILEY J.N. , DOWNS D.A.
Published: August 2010

Several small peptides related to neurotensin (NT) and tuftsin were synthesized and tested for analgesic activity against acetic acid induced writhing in mice. None of the peptides approached the activity shown by NT or NT hexapeptide. Tuftsin itself was found to be weakly active. An isosteric dipeptide related to a cobra venom peptide was found to have considerable anti‐writhing activity at a high intracerebroventricular dose.
β‐endorphin. Synthesis and biological activity of analogs with disulfide bridges
Authors: BLAKE JAMES , HELMESTE DAIGA M. , LI CHOH HAO
Published: August 2010

Two analogs of human β‐endorphin (β‐EP) which contain cystine bridges, [Cys15‐Cys26,Phe27,Gly31]‐β‐EP (I) and [Cys16‐Cys26,Phe27,Gly31]‐β‐EP (II), were synthesized by the solid‐phase method. Peptides I and II were shown to contain 2–2.5 times the opiate receptor binding activity of β‐endorphin. We also synthesized two analogs with reduced alkylated cysteine residues and these peptides, [Arg9,19,24,28,29Cys(Cam)11,26, Phe27,Gly31] and [Arg9,19,24,28,29,Cys‐(Cam)12,26, Phe27, Gly31], were shown to have approximately the same opiate receptor activity as β‐endorphin.
Preparation and analytical data of some unusual amino acid derivatives used in peptide syntheses (I)
Authors: BALÁSPIRI LAJOS , TÓTH MIHÁLY V. , SOMLAI CSABA , KOVÁCS KÁLMÁN
Published: August 2010

The preparation methods, yields and some analytical data of benzyloxycarbonyl‐, t‐butyloxycarbonyl‐ and 9‐fluorenylmethyloxycarbonyl‐amino acid derivatives of several unusual amino acids are given and tabulated.
Synthesis of thymosin α1by fragment condensation usingtert.‐butyl side chain protection
Authors: FELIX ARTHUR M. , HEIMER EDGAR P. , WANG CHING‐TSO , LAMBROS THEODORE J. , SWISTOK JOSEPH , ROSZKOWSKI MARTIN , AHMAD MUSTAQ , CONFALONE DIANNE , SCOTT JOHN W. , PARKER DAVID , MEIENHOFER JOHANNES , TRZECIAK ARNOLD , GILLESSEN DIETER
Published: August 2010

A novel synthesis of thymosin α1by classical methods using seventert.‐butyl side chain protected fragments is described. Optimum conditions were found for the final DCC/HOBt coupling of the two key intermediates; decapeptide and octadecapeptide. Thymosin α1was purified by two stages of preparative HPLC (partial purification with C8and final purification with C18reverse phase silica gel) to give a 30% overall yield for the final four stages of synthesis (including catalytic hydrogenation of octadecapeptide, coupling, deprotection and purification). The product was shown to be homogeneous by thin‐layer and paper high voltage electrophoresis, isoelectric focusing analysis, thin‐layer chromatography and high performance liquid chromatography. Amino acid analysis, optical rotation,1H‐n.m.r. spectroscopy, FAB mass spectroscopy and peptide mapping after tryptic digestion confirmed the structure of thymosin α1. Three minor stereoisomer contaminants were isolated by HPLC and characterized as [D‐Lys14]‐thymosin α1, [D‐Lys17]‐thymosin α1and [D‐Ala3]‐thymosin α1resulting from racemization at Lys14, Lys17and Ala3during the coupling of the fragments. A final contaminant, isolated by HPLC, was characterized asNα‐isobutyloxycarbonyl‐thymosin α1(15–28), which results from “wrong way opening” of an activated mixed anhydride.
Effect of cetyl trimethyl ammonium bromide on the heat‐induced denaturation and protein‐protein interactions of arachin at pH 3.6
Authors: KELLA NAVIN KUMAR D. , RAO M.S. NARASINGA
Published: August 2010

The effect of a cationic detergent, cetyl trimethyl ammonium bromide, on the heat‐induced denaturation and protein‐protein interactions of arachin at pH 3.6 was studied by gel melting temperature, turbidity, electrophoresis, u.v. difference and fluorescence spectral measurements. Cetyl trimethyl ammonium bromide decreased the heat‐induced protein‐protein interactions as shown by the melting temperature, turbidity and electrophoretic measurements. Turbidity and electrophoretic measurements also showed that the detergent induces dissociation of the protein before and after heating it at higher detergent concentration (above 1 times 10‐3 M). U.v. difference and fluorescence spectral measurements suggested that the detergent induces unfolding of arachin at room temperature and this increases markedly after heating the protein in the detergent. The promotive effect of cetyl trimethyl ammonium bromide on the heat‐induced denaturation and its preventive effect on the protein‐protein interactions of arachin under the experimental conditions may arise out of the binding of the detergent to protein by primarily hydrophobic interactions.
Myoglobin structure and regulation of solvent accessibility of heme pocket
Authors: BISMUTO ETTORE , COLONNA GIOVANNI , SAVY FRANCESCA , IRACE GAETANO
Published: August 2010

The effects of heme removal on the molecular structure of tuna and sperm whale myoglobin have been investigated by comparing the solvent accessibility to the heme pocket of the two proteins with that of the corresponding apoproteins. Although the heme microenvironment of tuna myoglobin is more polar than that of sperm whale myoglobin, the accessibility of solvent to heme is identical in the two proteins as revealed by thermal perturbation of Soret absorption. The removal of heme produces loss of helical folding and increase of solvent accessibility but the effects are rather different for the two proteins. More precisely, the loss of helical structure upon heme removal is 50% for tuna myoglobin and 15% for sperm whale myoglobin; moreover, the solvent accessibility of the heme pocket of tuna apomyoglobin is 2–3‐fold greater than that of sperm whale apomyoglobin. These results have been explained in terms of the lack of helical folding in segment D, the structural organization of which may have a relevant effect in regulating the accessibility of ligands to the heme. The effects produced by charged quenchers reveal that the ligand path from the surface of the molecule to the ion atom of the heme involves a positively charged residue which may reasonably be identified as Arg‐45 (sperm whale myoglobin) or Lys‐41 (tuna myoglobin) on the basis of recent X‐ray crystallographic information.