bluuebunny/crossref_metadata_2025 huggingface dataset:
Testing for cis‘ proline with α‐aminoisobutyric acid substitution
Authors: LONDON ROBERT E. , SCHMIDT PAUL G. , VAVREK RAYMOND J. , STEWART JOHN M.
Published: August 2010

Substitution of Pro residues with AIB (α‐aminoisobutyric acid) residues in peptides provides a means of evaluating the presence of cis' proline conformations both in solution and, using bioassay data, in a receptor complex. 1 H n.m.r. has been used to probe the DMSO solution conformation of all seven of the possible AIB/Pro isomers of bradykinin. AIB substitution for Pro2 and/or Pro3 appears to stabilize a type III β‐turn involving the N‐terminal residues, but not an incipient 310 helix suggested by model peptides. These substitutions are correlated with low biological potencies, suggesting that such conformational features may be incompatible with receptor complexation. Alternatively, AIB7 ‐bradykinin analogs exhibit a variety of long range shift perturbations relative to bradykinin. The data suggests that bradykinin can adopt several folded conformations, including β‐turns involving both Ser6‐Pro7‐Phe8‐Arg9 and Phe5‐Ser6‐Pro7‐Phe8. The relatively high biological activities of the AIB7‐BK suggest that the complexed form of the peptide is characterized by a cis' Pro7 conformation.
Solid‐phase synthesis of peptides via α, β‐unsaturated amino acids: Oxytocin, simultaneous incorporation of amide functions in COOH‐terminal and endo‐positions
Authors: NODA KOSAKU , GAZIS DIANA , GROSS ERHARD
Published: August 2010

Oxytocin was synthesized via the solid‐phase method using dehydroalanine as pseudo‐protecting group of the carboxyl‐terminal as well as the ω‐amide functions of asparagine and glutamine in endo‐position. Starting with Boc‐Gly‐Dha‐resin and using Boc‐L‐Asp(Dha‐NHEt)‐OH and Boc‐L‐Glu(Dha‐NHEt)‐OH as precursors of asparagine and glutamine, respectively, oxytocin was assembled in stepwise manner under solid phase synthesis conditions. Treatment of the protected [Glu(Dha‐NHEt)4, Asp(Dha‐NHEt)5]‐oxytocin‐Dha‐resin with 1 N HCl in glacial acetic acid in the presence of 3 equiv. water removed the peptide from the support with the simultaneous formation of the asparagine and glutamine residues to give the protected nonapeptide amide: Cbz‐Cys(Bzl)‐Tyr(Bzl)‐He‐Gln‐Asn‐Cys(Bzl)‐Pro‐Leu‐Gly‐NH2, which was deprotected with sodium in liquid ammonia and then oxidized with diiodoethane to give oxytocin. After purification by gel chromatography and countercurrent distribution, the product displayed the chemical and physical properties and oxytocic activity (533 ± 30 IU/mg) of a standard oxytocin preparation.
Circular dichroic and immunological properties of human choriogonadotropin‐β carboxyl terminal peptides
Authors: PUETT DAVID , RYAN ROBERT J. , STEVENS VERNON C.
Published: August 2010

Circular dichroic spectra have been obtained in aqueous solution and in trifluoroethanol for several synthetic (non‐glycosylated) human choriogonadotropin carboxyl terminal peptides of the β‐subunit ranging in size from 10 residues to 40 residues. There was no evidence for formation of α‐helicity or β‐structure, but the spectra in 90% (v/v) trifluoroethanol were consistent with the occurrence of β‐turns. The Chou‐Fasman predictive rules also suggest a high probability of β‐turns in these peptides which could result in the occurrence of repeating kinks. Disulfide‐linked dimers were also investigated by circular dichroism, and there was evidence of stabilization of particular skewness of the disulfide dihedral angle depending upon the location of the disulfide bond. The single phenylalanyl residue at position 115 in the β‐subunit also contributed to the circular dichroic spectra above 250 nm. Antibodies raised to a peptide consisting of residues 111–145 have been shown to contain two immunological determinants, but the sum of antibodies raised to separate determinant sequences do not equal those raised to the full length peptide. These data could reflect the existence of a conformation‐related determinant on the 111–145 peptide or stearic hindrance of immunoglobulin binding of two antibodies to the same peptide.
Synthesis, conformation and reactivity towards p‐nitrophenyl acetate of polypeptides incorporating aspartic acid, serine and histidine
Authors: TRUDELLE YVES
Published: August 2010

Examination of β‐carbons coordinates of seryl, aspartyl and histidyl residues in active sites of α‐chymotrypsin and subtilisin BPN' shows that a close geometrical arrangement can be obtained in an antiparallel β‐structure. Therefore some polypeptides incorporating serine, aspartic acid and histidine, poly (Gly‐Ser‐Asp‐His‐Ala‐Pro) and poly [(Asp‐Leu‐Asp‐Leu)10, (His‐Leu‐Ser‐Leu)1], and expected to have some tendency to give rise to an antiparallel β‐conformation, have been prepared and studied. The second polymer only adopts a fairly well‐defined β‐structure in aqueous solution. Catalytic activities of these products towards p‐nitrophenyl acetate are not improved as compared to histidine. However kinetic pK of histidine side‐chain depends markedly upon the nature of the product, owing probably to a hydrophobic environment effect.
Deprotectum of Nin‐formyl tryptophan using 1,2‐ethanedithiol in liquid hydrogen fluoride
Authors: MATSUEDA GARY R.
Published: August 2010

Deprotection of Nin‐formyl tryptophan (Trp) occurs during liquid hydrogen fluoride treatment at 0° when 1,2‐ethanedithiol (EDT), or 1,4‐butanedithiol, is present. Deformylation, as evidenced by amino acid analysis and ultraviolet spectral analysis, is complete after 10 min at 0° when Trp(CHO) is treated with HF: anisole: EDT(85:10:5) or HF: EDT(95:5). HF treatment of a peptidyl‐resin containing Trp(CHO) yielded a peptide whose ultraviolet spectrum was typical of Trp (maximum at 280 nm) rather than Trp(CHO) (maximum at 300 nm). However, in the absence of dithiol during HF treatment, the expected spectrum for Trp(CHO) was obtained. The efficiency of HF cleavage of a 49‐pe?tidyl‐resin was unaffected by EDT; 77% was cleaved in the presence of EDT, and 76% in the absence of EDT. In a model study, dithiol deformylation as a synthetic tactic was used for the solid‐phase synthesis of Trp‐Met‐Asp‐Phe amide. When the Trp(CHO)‐Met‐Asp(Bzl)‐Phe‐NH‐methylbenzhydrylamine resin was treated with HF:anisole: EDT(85:10:5) for 30 min at 0°, the major peptide component observed by high pressure liquid chromatography (HPLC) was identical to the control tetrapeptide amide made without CHO‐group protection of Trp.
Biofunctional evaluation of a hydrogen bond stabilizing the conformation in the cyclic part of oxytocin
Authors: ROY J. , GAZIS D. , SHAKMAN R. , SCHWARTZ I.L.
Published: August 2010

[5‐β‐Malamidic acid] oxytocin was synthesized to study the importance of the hydrogen bond between the C=O of Tyr2and the peptide N‐H of Asn5for the stabilization of a biologically functional conformation of oxytocin. This analog lacks the peptide N‐H at residue 5 required for the formation of a hydrogen bond with the C=O of Tyr2. [5‐β‐Malamidic acid] oxytocin exhibited 45.1 ± 2.5 U/mg and 65.6 ± 5.9 U/mg of uterotonic activity,in vitro, in the absence and in the presence, respectively, of Mg2+, 147 ± 14 U/mg of uterotonic activityin vivo, 203 ± 13 U/mg of milk‐ejecting activity, 0.37 ± 0.03 U/mg of pressor activity and 0.32 ± 0.29 U/mg of antidiuretic activity. It is concluded that devoid of the hydrogen bond under question, an oxytocin‐like peptide can still assume the conformation needed to interact with the oxytocin receptors.
Conformation and crystal structure of L‐prolyl‐L‐glutamic acid dihydrate
Authors: EGGLESTON DRAKE S. , HODGSON DEREK J.
Published: August 2010

The crystal structure of the dipeptide L‐prolyl‐L‐glutamic acid dihydrate, L‐Pro‐L‐Glu · 2H2O, C10H20O7N2, has been determined from three‐dimensional X‐ray diffractometer data. The dipeptide crystallizes in the space group P21 of the monoclinic system with two formula units in a cell of dimensions a= 5.629(2), b= 11.832(5), c= 10.485(4)Å, and β= 103.06(3)°. The structure was solved by direct methods and refined by least squares techniques to a final value of the conventional R‐factor (on F) of 0.039 based on 1798 independent intensities with I ≥ 3s̀(I). The dipeptide occurs as a zwitterion in the crystal with the pyrrolidine nitrogen atom protonated and the main chain carboxyl group deprotonated. The conformation of the peptide linkage is trans, the ω torsional angle being 173.7°. The pyrrolidine ring adopts the Cs‐Cβ endo conformation and the conformation of the glutamyl side chain is fully extended. There is considerable intermolecular hydrogen bonding in the crystals.
Examination of chiral stability during the preparation of hydrazides and coupling by the azide procedure using a series of model peptides
Authors: BENOITON N. LEO , KURODA KEIJI , CHEN FRANCIS M.F.
Published: August 2010

The peptide hydrazides of N‐benzyloxycarbonylglycyl‐X where X = alanine, leucine, phenylalanine, valine and isoleucine have been prepared by hydrazinolysis of the corresponding methyl esters and 2,4‐distributed‐5(4H)‐oxazolones, and by the carbodiimide‐mediated reactions of the peptide acids with hydrazine in the presence of 1‐hydroxybenzotriazole. The stereochemical purity of the products was examined by coupling them by the azide method with an ester of lysine followed by analysis for the diastereomeric tripeptides by an established procedure. The results concur with and substantiate the generally held notions on the chiral stability associated with hydrazinolysis and the azide procedure, except that an optically pure hydrazide could not be obtained from the oxazolone of the alanyl peptide.
Structural features of human leukocyte interferon A as determined by circular dichroism spectroscopy*
Authors: BEWLEY THOMAS A. , LEVINE HOWARD L. , WETZEL RONALD
Published: August 2010

The solution structure of human leukocyte (alpha) interferon‐A (LeIF‐A) purified from E. coli extracts was investigated by circular dichroism spectroscopy. At pH 8.2, the native molecule exhibits 40–70%α‐helix and no clearly detectable β‐structure. The tertiary structure includes a closely‐packed interior containing at least one tryptophan side‐chain. Titration to pH 1.5 produces a partial loss of structural features which are rapidly regained on return to neutral pH.
Circular dichroism studies on conformational transitions of phytohemagglutinins effected by some alcohols
Authors: JIRGENSONS BRUNO , ROSS DORIS L.
Published: August 2010

The effects of methanol, ethanol, 1‐propanol and 2,2,2,‐trifluoroethanol (TFE) on conformation of 10 phytohemagglutinins (lectins) were examined by applying the circular dichroism (CD) method. Concanavalin A and the lectins isolated from pea (Pisum sativum), lentil (Lens culinaris), soybean (Glycine max), peanut (Arachis hypogaea), Dolichos biflorus, Sophora japonica, Lotus tetragonolobus, Ulex europaeus I, and Phaseolus vulgaris (leucoagglutinin) were used.

Slight changes in the structure of these proteins were observed at relatively low concentrations (5–20 vol. %, pH 7.2–8.2, at 22–25°) of the perturbants, and the effectiveness of the alcohols increased with their concentration and molecular weight. The circular dichroism bands related to the aromatic side chain chromophores decreased in the presence of the alcohols. The secondary structure was reorganized by high concentrations (30–80 vol. %) of the alcohols, as indicated by CD at 187–250 nm. Curves typical for proteins of relatively high α‐helix content (strong positive CD bands at 191 nm and negative bands at 206–208 and 222 nm) were recorded in the presence of high concentrations of trifluoroethanol.
Side chain characteristic main chain conformations of amino acid residues
Authors: KOLASKAR A.S. , RAMABRAHMAM V.
Published: August 2010

Main chain conformation characteristics of the respective side chains of the 20 naturally occurring amino acid residues were obtained by the analysis of (φ, ε)‐data from the crystal structures of 38 different globular proteins. The following observations are of interest: (i) For amino acids other than Glu, Thr and aliphatic amino acids, at least one main chain conformation is stabilised solely by side chain atoms. Such conformations are listed. (ii) In globular proteins, the main chain conformations which are significantly destabilised by side chain atom interactions are observed. The stabilising force for those conformations seems to come from main chain atom interactions. (iii) A set of conformations for which the main chain and side chain interactions are almost equal but in opposite directions, is listed and these conformations will be taken by residues mainly due to the effect of surroundings.

The results can be used to study the folding of polypeptide chains and they also provide an insight into the role of the respective side chains on main chain conformations of amino acid residues.
Dynorphin in bovine adrenal medulla
Authors: DENIS DANIELLE , DAY ROBERT , LEMAIRE SIMON
Published: August 2010

Two highly potent dynorphin‐like peptides were isolated from bovine adrenal medulla by successive chromatography of an acid (HCl) extract on Sephadex G‐10, carboxymethylcellulose, Sephadex G‐50 and partition chromatography on Sephadex G‐50. Amino acid analysis of both peptides revealed the presence of 24 amino acids including the composition of dynorphin‐(1–13) and differing from each other only by a few residues. Both peptides were shown to have the same activity as dynorphin‐(1–13) in the guinea pig ileum assay and reacted as well as dynorphin‐(1–13) with a specific antibody (R‐31) directed against the synthetic material.
Effect of dimethylsulfoxide and its homologues on the thermal denaturation of lysozyme as measured by differential scanning calorimetry
Authors: FUJITA YUKIHISA , IZUMIGUCHI SHOZO , NODA YUKINAO
Published: August 2010

The thermal denaturation of lysozyme in aqueous sulfoxide solutions (pH 3) was investigated by differential scanning calorimetry (DSC). The sulfoxides employed were dimethylsulfoxide (DMSO), ethylmethylsulfoxide (EMSO), diethylsulfoxide (DESO), and butylmethylsulfoxide (BMSO). The temperature of denaturation, Td, decreased with an increase in the concentration of sulfoxide, the decrease becoming much more pronounced at higher sulfoxide concentrations. The lowering of Td was enhanced by an increase in the hydrocarbon content of the sulfoxide molecule. The enthalpy of denaturation, ΔHd, showed a complex dependence on the solvent composition; the ΔHd first increased with increasing sulfoxide concentration and then started decreasing at different concentrations for each sulfoxide. This behavior is analogous to that with monohydric alcohols, but is different from that with guanidine hydrochloride. These results may be interpreted in terms of the interactions of the sulfoxide added with the protein and with water.
Critical chain length for polyproline‐II structure formation in H‐Gly‐(Pro)n‐OH
Authors: HELBECQUE N. , LOUCHEUX‐LEFEBVRE M.H.
Published: August 2010

Linear proline‐containing peptides H‐Gly‐(Pro)n‐OH with n = 2–5 have been investigated by measuring the circular dichroism in water as a function of pH, temperature and salt added. By comparison with similar studies conducted by others on oligoprolines it has been possible to demonstrate the formation of a helical (polyproline II‐like) structure at the stage n = 3.
Penguin egg‐white and polar fish blood‐serum proteins
Authors: FEENEY ROBERT E.
Published: August 2010

The development of, and findings in, a long‐term research program on penguin proteins and polar fish blood proteins are described. Two of the egg‐white proteins from the Adelie penguin (Pygoscelis adeliae) have unique properties: a glycoprotein named penalbumin that is a major constituent with some characteristics similar to ovalbumin, and an ovomucoid with strong inhibitory capacity for subtilisin as well as for bovine trypsin and α‐chymotrypsin. The antifreeze glycoproteins from Antarctic fish (Trematomus borchgrevinki and Dissostichus mawsoni) and an Arctic fish (Boreogadus saida) appear to function noncolligatively by lowering the freezing temperature without affecting the melting point. Current evidence indicates that the antifreeze glycoprotein functions at the ice‐solution interface, either on the ice surface or in a transition layer between the solution and the ice.
Circular dichroic and fluoropolarimetric studies on tryptophyl residues in acid‐induced isomerization of bovine plasma albumin*
Authors: SOGAMI MASARU , ERA SEIICHI , NAGAOKA SHUNJI , INOUYE HIROSHI
Published: August 2010

The acid‐induced isomerization (the N‐F transition) and expansion of bovine plasma albumin were studied by measuring circular dichroic spectra and fluorescence polarization of tryptophyl residues. Decreases in the magnitude of ellipticities at 208, 222, 262 and 268nm were observed in the N‐F transition and acid‐expansion. However, increases in the magnitude of ellipticities at 295–300nm observed in the initial part of the N‐F transition exactly correlated with the increase of rotational relaxation time of tryptophyl side chains obtained by fluorescence polarization measurement.
Formation of aminosuccinyl derivative from β‐phenacyl aspartyl peptides catalyzed by sodium thiophenoxide
Authors: GAUDREAU PIERRETTE , MORELL JOHN L. , GROSS ERHARD
Published: August 2010

In the solid‐phase synthesis of cholecystokinin 30–33, Trp‐Met‐Asp‐Phe‐ amide, the β‐phenacyl ester was used to protect the β‐carboxyl of aspartyl residue. The ester was cleaved, on the solid support, with a 1 M solution of sodium thiophenoxide in DMF, prior to ammonolysis. The product, after purification by countercurrent distribution, was identified as a mixture of isoasparaginyl and aspartyl peptides. A study of the deprotection step, with sodium thiophenoxide, on a model peptide (t‐butyloxycarbonyl‐β‐phenacyl‐aspartyl‐phenylalanineamide) showed the rapid formation of the aminosuccinyl derivative, catalyzed by this reagent.
Comparison of the thermal stability characteristics of native and deglycosylated ovine pituitary lutropin
Authors: SAIRAM M.R. , MANJUNATH P.
Published: August 2010

The receptor binding, immunological and biological activities of native ovine lutropin were almost completely eliminated when aqueous solutions of the hormone were kept in a boiling water bath for 30 or 60 min. Similar exposure of chemically deglycosylated lutropin revealed that this preparation was relatively more stable to heat treatment. The conformational features of deglycosylated lutropin required for receptor binding and immunological activity were significantly retained after thermal treatment. The heated deglycosylated lutropin solution still retained its ability to antagonize cyclic AMP accumulation stimulated by the native hormone in rat testicular interstitial cells. Specificity of receptor (lutropin) binding or inhibitory activity was not lost by heating of deglycosylated lutropin as revealed by lack of an effect in follitropin radioreceptor assays.
Chemistry of carbamoyl disulfide protected derivatives of proline*
Authors: BARANY GEORGE
Published: August 2010

High‐yield methods have been devised for the synthesis of a series of alkyl and aryldithiocarbonyl derivatives of the α‐imino acid proline. The carbamoyl disulfide protecting groups were rapidly and quantitatively removed under a variety of reductive conditions, suggesting their potential value for orthogonal schemes of peptide synthesis.
Identification of secondary structures in globular proteins ‐ a new algorithm*
Authors: Ramakrishna C. , Soman K.V.
Published: August 2010

A new algorithm has been developed for identifying helices, extended structures, and bends from the positions of the α‐carbon atoms using the virtual bond approach. The parameters used are two virtual bond angles (Δ1 and Δ2), the virtual dihedral angle (θ), and the distance (D) between the terminal α‐carbon atoms of the tripeptide.

The criteria for classification have been worked out by model building as well as from proteins whose complete secondary structures are known. These criteria are as follows: (i) |θ| ≤ 60° and (Δ1+Δ2) ≤ 230° for a bend, (ii) for a helix, successive θ's should not differ by more than 30°, and (iii) for an extended structure, the cumulative deviation of the above parameters should not vary by more than 20% from the ideal extended chain. The method developed has been applied successfully to three proteins wherein the coordinates of α‐carbon atoms alone are known and a complete mapping of the secondary structures has now been obtained. One interesting observation is that the percentage of residues not taking part in helices, extended structures, and bends is very small ‐ of the order of 4%.
Pigeon egg white lysozyme
Authors: Gavilanes J. G. , De Buitrago G. Gonzalez , Del Pozo A. Martinez , Perez‐CasTells R. , Rodríguez R.
Published: August 2010

Lysozyme from pigeon egg white has been purified by ion exchange chromatography and gel filtration. The overall yield of the purification procedure is 65%. The specific activity of the enzyme is 15 000 units/mg. The influence of pH and ionic strength on the lytic activity of the protein, as well as its thermal stability, have been studied. The molecular weight, secondary structure estimation, amino acid composition, NH2‐ and COOH‐terminal sequence of the protein are also reported. The pigeon enzyme has been classified as a chicken type lysozyme (lysozyme c) according to the obtained results.
Refinement of conformational preferences of Leu enkephalin and Tyr‐Gly‐Gly‐Phe by 15 N n.m.r.
Authors: GARBAY‐JAUREGUIBERRY C. , MARION D. , FELLION E. , ROQUES B.P.
Published: August 2010

15N labeled Tyr‐*Gly‐*Gly‐*Phe (I) and Tyr‐*Gly‐*Gly‐*Phe‐*Leu or Leuenkephalin (II) are taken as models to test the ability of 15N n.m.r. as conformational probe for peptide analysis. Analysis of the 3J 15 N‐1Hα constants using a Karplus relationship permits the proposal of a 2–5 βII type turn for Leuenkephalin, instead of the previously proposed 2–5 βI bend. In the two peptides, side‐chain populations for Phe and Leu residues are computed, without any assignment assumption, by an optimization procedure taking into account all the available vicinal coupling constants (3JHαHβ, 3J 13CO‐Hβ, 3J 15N‐Hβ). Our results confirm the upfield shift of the β ProR proton relatively to the β ProS for the β CH2 group of Phe residue in Me2SO solution.

In both peptides (I) and (II), the tg° rotamer is the most populated for residue Phe4, whereas in (II) only this rotamer is present for the Leu5 sidechain. This feature indicates that the hydrophobic group lies opposite to the N‐terminal Tyr residue, a feature not found for the methionine side‐chain in Met‐enkephalin.
Reductive methylation of insulin: Production of a biologically active tritiated insulin
Authors: MARSH JON W. , NAHUM AVI , STEINER DONALD F.
Published: August 2010

Reductive methylation of the three amino groups of porcine insulin was accomplished by incubation with formaldehyde and sodium cyanoborohydride. The two amino termini and the epsilon amino group of B29 lysine were each dimethylated within 1 h of incubation. The fully methylated insulin bound more tightly to a reverse phase column than did native insulin, had a slightly more acid isoelectric point, and maintained approximately 50% biological activity when examined with an insulin sensitive cultured cell line. Reductive methylation with sodium cyanoboro [3H] hydride resulted in a [3H] methylated insulin with a specific activity of 6 Ci/mmol.
Isolation of melanotropins and vasopressin from neuro‐intermediate lobes of bovine pituitary glands. A simplified procedure
Authors: HAMMOND GRAEME L. , CHUNG DAVID , LI CHOH HAO
Published: August 2010

A simplified procedure for the isolation of α‐melanotropin, β‐melanotropin and arginine vasopressin from the acid acetone extract of posterior‐intermediate lobes of bovine pituitaries has been described. It involves essentially two steps: gel filtration on Sephadex G‐10 and high performance liquid chromatography.
Synthesis of the protected tridecapeptide (56–68) of the VH domain of mouse myeloma immunoglobulin M603 and its reattachment to resin supports
Authors: VOSS CHRISTOPH , DIMARCHI RICHARD , WHITNEY DONALD B. , TJOENG FOE SIONG , MERRIFIELD R.B. , TAM JAMES P.
Published: August 2010

A protected tridecapeptide, representing a new peptide corresponding to residues 56–68 of the VH domain in the mouse M603 myeloma protein, has been prepared by solid phase peptide synthesis. The protected tridecapeptide was prepared using the photolabile 4‐bromomethyl‐(3‐nitro)‐benzamidomethyl‐resin and the multidetachable 2‐[4‐bromomethyl)phenylacetoxy] propionyl‐resin as solid supports. The synthetic protocol and protecting groups were the same for both syntheses. The protected tridecapeptide was removed photolytically from both supports and the sequence integrity was determined by preview analysis using the solid phase Edman degradation procedure. The protected tridecapeptide‐OMPA was purified to homogeneity by DMF/H2O precipitation and LH‐60 chromatography. The purity of the protected peptide was further demonstrated by high pressure liquid chromatography on the free peptide after HF deprotection. The protected tridecapeptide was reattached to 4‐bromomethyl‐(3‐nitro)‐benzamidomethyl‐resin to give the photolabile Boc‐(protected) peptidyl‐4 ‐ oxymethyl ‐ (3 ‐ nitro) benzamidomethyl ‐ resin in 25% yield. The protected tridecapeptide‐oxymethylphenylacetic acid derivative was reattached to aminomethyl‐resin to give Boc ‐(protected)peptidyl‐2‐[(4‐oxymethyl)phenyl]acet‐amidomethyl‐resin in 45% yield and to 2‐bromopropionyl‐resin generating the multidetachable Boc ‐ (protected)peptidyl ‐ 2 ‐ [(4 ‐ oxymethyl) phenylacetoxy] propionyl‐resin in 80% yield. The reactivity of these reattached peptides was demonstrated by the quantitative coupling of Boc‐leucine to the protected peptide‐resin. The advantages and disadvantages of the different resins with respect to solid phase fragment synthesis are discussed.
The toxic peptides from Amanita mushrooms
Authors: WIELAND THEODOR
Published: August 2010

The results of 50 years of effort in the chemistry of Amanita toxins are reviewed. The phallotoxins, fast acting components, but not responsible for fatal intoxications after ingestion, are bicyclic heptapeptides. They combine with F‐actin, stabilizing this protein against several destabilizing influences. The virotoxins likewise fast acting are monocyclic heptapeptides. The amatoxins which are the real toxins lead to death within several days by inhibiting the enzymatic synthesis of m‐RNA. They are bicyclic octapeptides. The structures of all of these compounds are described, as well as conformations, chemical reactions and modifications, syntheses and correlations between structures and biological activities.
Effect of amino acids, peptides and related compounds on the autooxidation of ascorbic acid
Authors: FLEMING J.E. , BENSCH K.G.
Published: August 2010

The autooxidation rate of ascorbic acid (AA) at 10‐5 m under aerobic conditions at pH 7.4 was found to be 1.16 μmol/min/1. A number of compounds at low concentrations were found to inhibit this oxidation rate. These were in order of effectiveness: EDTA (10‐6 m) > Mercaptoethanol > aminoethyl cysteine, oxidized glutathione > glycylglycylhistidine > glycylhistidyllysine > 3‐methyl histidine ˜ histidine > histamine > hypertensin > cysteic acid > imidazole > glutamine > hydroxyproline, and lysine. All other amino acids and peptides examined had little or no effect on the autooxidation rate of ascorbic acid. Ascorbate solutions, treated with Chelex‐100 (divalent chelating resin) or containing low concentrations of EDTA (10‐7 m) did not show a significant reduction of the rate of autooxidation. Of particular interest was the finding that 3‐methyl histidine had a significant inhibitory effect on ascorbic acid oxidation whereas 1‐methyl histidine had no effect. These data suggest that ascorbic acid forms complexes with certain compounds and that this interaction stabilizes ascorbic acid against auto‐oxidation.
Conformational and biological properties of glucagon fragments containing residues 1–17 and 19–29
Authors: CARREY ELIZABETH A. , EPAND RICHARD M.
Published: August 2010

The 29 amino acid polypeptide hormone glucagon was cleaved into two large fragments by the enzyme clostripain. The conformational properties of these two fragments were monitored by circular dichroism at pH 2 and 12 in both the presence and absence of sodium dodecyl sulfate. Both glucagon (1–17) and glucagon (19–29) have reduced abilities to fold in aqueous solution. However, both fragments can take on structure of higher apparent helical content in acidic solution in the presence of sodium dodecyl sulfate but only the glucagon (19–29) retains this conformation at high pH. Neither of the two fragments react with dimyristoylphosphatidylcholine as the intact peptide does. Only the carboxyl terminal fragment was capable of reacting with an antibody specific for glucagon. The glucagon (1–17) has markedly reduced affinity for binding to the glucagon receptor as well as markedly reduced ability to stimulate adenylate cyclase activity which is not affected by the presence of glucagon (19–29). It is proposed that the intact sequence provides specific groups required for activity as well as the potential for forming a stable amphipathic helix, both of which are necessary for full biological activity at low peptide concentrations.
High‐performance partition chromatography of peptides on a new cross‐linked agarose
Authors: YAMASHIRO DONALD
Published: August 2010

A new cross‐linked agarose in bead form (20–40 microns in diameter) has been used for partition chromatography in two‐phase solvent systems to give columns exhibiting efficiencies of several thousand theoretical plates. The efficiency of this high‐performance partition column (70–80 plates per cm) far exceeds that of the most commonly used soft gel Sephadex G‐50 (10 plates per cm). The column is operated under moderate pressure (5 p.s.i.) and can be regenerated. The new procedure appears capable of separating a peptide of moderate size, such as β‐endorphin (31 residues), from the majority of possible single‐deletion sequences.
[1‐Desaminopenicillamine, 8‐α‐hydroxyisocaproic acid] oxytocin. A selective inhibitor in rats of the uterine response to oxytocin
Authors: GAZIS DIANA , ROY UMA , SCHWARTZ I.L. , ROY J.
Published: August 2010

[1‐Desaminopenicillamine, 8‐α‐hydroxyisocaproic acid] oxytocin was synthesized by a 6 + 3 fragment condensation from precursors which had been formed by solution methods. This analog inhibited uterine responses to oxytocin (pA2 7.37, 7.9, 6.17; uterus in vitro without Mg++, in vitro with Mg++, and in vivo, respectively) and showed little or no activity in other bioassays.
Estimation of peptide hormone noncovalent binding site functionality from frequencies of interaction of amino acid side chains in proteins
Authors: Roberts David C. , Bohacek Regine S.
Published: August 2010

A method is described for estimating the amino acid side chain functional groups most likely to occur at a receptor site (or other protein‐type binding site) given a particular peptide hormone sequence. The predictions are based on mutual affinities of amino acid side chains, as manifested in the frequencies of side chain contacts occurring in proteins. The relative merits of various measures of these affinities are discussed, and a new set of contact frequency data based on 36 proteins (coordinate data taken from the Brookhaven Protein Data Bank) is presented. Evaluation of predictions was carried out using subunit‐subunit interfaces as models for peptide‐receptor association; accuracy of guesses was found to be 3–4 times better than random, according to this measure. Computer programs for carrying out all requisite data manipulations are described.
Cyclic peptides
Authors: HASHIMOTO YOSHIHIDE , AOYAGI HARUHIKO , WAKI MICHINORI , KATO TETSUO , IZUMIYA NOBUO
Published: August 2010

Four cyclic dehydrodipeptides, cyclo (‐Δaminoacyl‐L‐Ala‐), in which aminoacyl is Phe, Apb (2‐amino‐4‐phenylbutanoic acid), App (2‐amino‐5‐phenylpentanoic acid) and Aph (2‐amino‐6‐phenylhexanoic acid), were prepared by condensation of cyclo (‐N‐Ac‐Gly‐N‐Ac‐L‐Ala‐) with the corresponding aldehydes. Among them, the yield of cyclo (‐ΔApb‐L‐Ala‐) was exceptionally low. Each compound was hydrogenated in the presence of Pd black at various temperatures and chiral induction in hydrogenation was evaluated. Low chiral induction at high temperature (50d̀) was observed in the case of cyclo (‐ΔPhe‐L‐Ala‐). Optically pure L‐Apb, L‐App and L‐Aph were obtained from the corresponding cyclic dehydrodipeptides, respectively, by hydrogenation and subsequent acid hydrolysis.
Nitroxyl‐induced T1 relaxation rates as a probe of conformation in peptide hormones
Authors: KOPPLE KENNETH D.
Published: August 2010

Proton spin‐lattice relaxation rates in the N‐H region of the n.m.r. spectra of aqueous LHRH and angiotensin II were measured in the presence of varying concentrations of 2,2,6,6‐tetramethylpiperidinoxyl. At peptide concentrations of 3–7 mM and nitroxyl concentrations up to three times the peptide concentration, the relaxation rate is linearly dependent on nitroxyl concentration. Second order rate constants for nitroxyl induced relaxation in water are in the 200–1000s‐1 M‐1 range, and are dependent more on conformational factors than on side chain bulk. Exclusion of the radical from the hydration sphere of imidazolium ion appears to occur. The measurements for LHRH agree with earlier observations of the effect of the nitroxyl on linewidths. A two‐ to threefold decrease in sensitivity of the amide protons of at least three of the residues in angiotensin II when the His6 imidazole is protonated indicates a conformational transition related to this ionization.
Confirmation of the primary structure of thymosin α1 by microsequence analysis of limited acid and enzymatic hydrolysis fragments
Authors: MICHALEWSKY JOSEPH , GABRIEL THOMAS F. , WINTER DONALD P. , MAKOFSKE RAYMOND , DANHO WALEED , SHIVELY JOHN , BIEMANN KLAUS , MEIENHOFER JOHANNES
Published: August 2010

The primary structure of the 28‐peptide thymosin α1 as determined by Goldstein et al. (1) has been confirmed by independent procedures. Limited dilute acid digestion generated a 26‐peptide and a 22‐peptide both extending to the C‐terminal and lacking the N‐terminal blocking group. A combination of Edman microsequencing, carboxypeptidase Y and thermolysin digestion, and fast atom bombardment mass spectrometry was used.
Carbonyldiimidazole/1‐hydroxybenzotriazole activation in polymer phase synthesis of the arginine rich proalbumin hexapeptide extension
Authors: PIPKORN R. , SCHMID M. , WEIGAND K. , BIRR CHR.
Published: August 2010

The synthesis on different polymer phases of Arg‐Gly‐Val‐Phe‐Arg‐Arg, the proalbumin extension, is reported. The peptide was prepared both on a 0.5% cross‐linked polystyrene gel containing 2‐oxoethyl bromide anchor functions and on a 1% cross‐linked chloromethyl polystyrene. For temporary blocking of the amino groups we utilized the 2‐(3, 5‐dimethoxyphenyl)propyl‐(2)‐oxycarbonyl (Ddz). The guanidino groups of the three arginine moieties were protected by the 4‐toluenesulfonyl (Tos) group. As coupling procedure we used 1 equiv. carbonyldiimidazole (CDI)/2 equiv. 1‐hydroxybenzotriazole (HOBt). The C‐terminal activation of the Ddz‐amino acids with CDI/HOBt made it possible to recover the excess Ddz‐amino acids in 60–80% yield. We also investigated different procedures to cleave the 2‐oxoethyl ester bond between the peptide and the polymer. This bond was completely stable against trifluoro‐methanesulfonic acid and was split by 1 N triethylamine in methanol/dioxane 1:1 (v/v) + 1 vol% 1 N NaOH. The optical rotation and HPLC properties of Arg‐Gly‐Val‐Phe‐Arg‐Arg from this synthesis are identical to the product from a different synthesis published earlier.
Information contained in protein shapes
Authors: SUNDARAM K. , VISWANADHAN V.N. , MacELROY R.D.
Published: August 2010

The sequence of local conformations at Cαatoms of a protein has been considered as an informational message string. The total self information contents and self information per letter have been evaluated for 83 globular proteins whose structures are known from X‐ray crystallography. The derived information contents provide a method of quantitating structural specificity of proteins. This method of analysis enables repeating, intricate structural features to be recognized. Among the globular proteins whose structures have been solved, high potential iron protein stands out with the largest three‐letter dependence.
Biological activity of synthetic analogs of serum thymic factor*
Authors: GYOTOKU JUNICHIRO , IMAIZUMI AKIRA , TERADA SHIGEYUKI , KIMOTO EIJI
Published: August 2010

A series of analogs of serum thymic factor (Facteur Thymique Sérique; FTS) devoid of C‐ and N‐terminal few residues were synthesized and their ability to induce Thy‐1 (θ) antigen in vitro on mouse T lymphocyte precursors was examined. The pentapeptide moiety (Lys‐Ser‐Gln‐Gly‐Gly) seems to be important for the expression of agonistic activity. Some of the short chain peptides showed antagonistic properties. Synergistic activation by two inactive analogs was observed.
Preferred conformation of the benzyloxycarbonyl‐amino group in peptides*
Authors: BENEDETTI ETTORE , PEDONE CARLO , TONIOLO CLAUDIO , DUDEK MICHAEL , NÉMETHY GEORGE , SCHERAGA HAROLD A.
Published: August 2010

Structural parameters, derived from X‐ray crystallographic data, have been compiled for 35 derivatives of amino acids, peptides, and related compounds, which contain the N‐terminal benzyloxycarbonyl (Z) group. The geometry of the urethane moiety of this end group is closely similar to that of the tert‐butoxycarbonyl (Boc) group, except for a relaxation of some bond angles because the Z group is sterically less crowded than the Boc group. For the same reason, the Z group has greater conformational flexibility. As a result, packing forces in the crystal may cause greater deformations of bond angles, resulting in larger variations of observed bond lengths and bond angles than in Boc‐peptide crystals. The aromatic rings of the Z end groups tend to stack in crystals. Conformational energy calculations indicate that most conformations of Z‐amino acid‐N' ‐methylamides and of corresponding Boc derivatives have similar dihedral angles and relative energies, i.e. the nature of the N‐terminal end group has little effect on the conformational preferences of the residue next to it. In particular, the computed fraction of molecules with a cisurethane (C‐N) bond is similar for the two derivatives: 0.51 and 0.42 in Boc‐Pro‐NHCH3 and Z‐Pro‐NHCH3, respectively, and 0.02 in the two Ala derivatives. There exist several computed conformations of Z‐Ala‐NHCH3 and Z‐Pro‐NHCH3 in which the phenyl ring and the C‐terminal methylamide group are close to each other. Because of favorable nonbonded interactions, such conformations are of low energy.
Effects of peptide‐binding on the proton n.m.r. spectrum of bovine neurophysin‐I
Authors: VIRMANI‐SARDANA VINOD , BRESLOW ESTHER
Published: August 2010

The effects of binding L‐phenylalanyl‐L‐phenylalanine amide and related peptides on the 220 MHz and 300 MHz proton n.m.r. spectra of bovine neurophysin‐I were studied. Throughout both the aliphatic and aromatic proton regions, marked binding‐induced changes in the protein spectrum occur which are best explained by invoking conformational change within the neurophysin dimer, in addition to direct perturbation of individual protein protons by bound peptide. In the region downfield from 6 p.p.m., a new resonance, centered at 6.45 p.p.m. was resolved in 300 MHz spectra. This resonance is tentatively assigned to a non‐exchangeable ‐NH and undergoes a reversible binding‐induced broadening. Also in this region, the binding‐induced chemical shift change in the ortho ring protons of Tyr‐49 was used to explore additional aspects of the kinetics of peptide‐binding. The results indicate that peptides with affinities ≥ 104M‐1 exhibit slow to intermediate exchange rates on the time scale of the Tyr‐49 chemical shift change, but that fast exchange can be achieved with peptides having affinities ≅ 102M‐1.
Dehydro‐enkephalins
Authors: SHIMOHIGASHI YASUYUKI , DUNNING JAMES W. , KOLAR ALDEAN J. , STAMMER CHARLES H.
Published: August 2010

Two kinds of dehydropeptide analogs of enkephalin containing a ΔTyr unit at the N‐terminus have been synthesized by coupling Boc‐ΔTyr‐(Cl2Bzl)‐OH with amino acid amides and tetrapeptide esters using the water soluble carbodiimide‐HOBt method. Pentapeptides consisting of ΔTyr1, and ΔPhe4 or ΔLeu5 were also prepared. Ultraviolet difference spectroscopy was important in the characterization of the dehydro moieties, ΔTyr, ΔPhe and ΔLeu. Attempts to liberate ΔTyr1‐enkephalins have been unsuccessful because of the instability of an N‐terminal ΔTyr residue having p‐phenolic group in the side chain.
Preparation and analytical data of some unusual t‐butyloxycarbonyl‐amino acids
Authors: PERSEO GIUSEPPE , PIANI SILVANO , De CASTIGLIONE ROBERTO
Published: August 2010

A modified method for the preparation of t‐butyloxycarbonyl‐amino acids is reported. The procedure is easily reproducible and permits the scale‐up with high yields. Analytical data of several unusual amino acids are tabulated.
Conformational study of the salivary proline‐rich polypeptides
Authors: ISEMURA T. , ASAKURA J. , SHIBATA S. , ISEMURA S. , SAITOH E. , SANADA K.
Published: August 2010

The conformational study of three proline‐rich polypeptides of human whole saliva, with known primary structures, was performed by CD and 1H‐n.m.r. spectra measurements. All these polypeptides contained more than four consecutive prolyl residues in their amino acid sequences. The occurrence of the poly‐L‐proline form II conformation in their structures was demonstrated with two of these polypeptides. The continuous prolyl residues in the third was suggested to take the same structure as the others.
Fluorescence study on the solution conformation of dynorphin in comparison to enkephalin
Authors: SCHILLER PETER W.
Published: August 2010

Conformational parameters of the opioid peptides dynorphin and [Leu5] enkephalin in dilute aqueous solution (3 times 10‐5M) were investigated by performing singlet‐singlet energy transfer experiments with dynorphin and with the biologically active 4‐tryptophan analogs of dynorphin‐(1–13) and [Leu5] enkephalin at pH 5.5 and 8.0. Efficiencies of transfer of excitation energy from the phenol ring of tyrosine (donor) to the indole moiety of tryptophan (acceptor) were determined and average intramolecular Tyr‐Trp distances were calculated on the basis of the Förster equation. The observed absence of energy transfer between Tyr1and Trp14of dynorphin indicates that the two fluorophores are at least 20 Å apart and rules out a close proximity between theN‐ andC‐terminal segments of the peptide. Evaluation of energy transfer in [Trp4] dynorphin‐(1–13) resulted in an average intramolecular Tyr1‐Trp4distance of at least 15 Å whereas the corresponding average distance in [Trp4, Leu5] enkephalin was found to be much shorter (10 Å). It thus appears that in [Trp4] dynorphin‐(1–13) the predominant conformation of theN‐terminal tetrapeptide segment is almost completely extended, whereas in [Trp4, Leu5] enkephalin folded conformations of that same segment occur in a major proportion. This drastic conformational difference is of interest with regard to the different preferences of dynorphin and [Leu5] enkephalin for the various opiate receptor subclasses.
Studies of peptide antibiotics
Authors: ANDO SHOJI , AOYAGI HARUHIKO , WAKI MICHINORI , KATO TETSUO , IZUMIYA NOBUO
Published: August 2010

Gramicidin S (GS) analogs, [D‐Ser4,4′]‐GS and its precursor [O‐benzyl‐D‐Ser4,4′]‐GS, were synthesized by the conventional method in order to evaluate the role of the hydroxymethyl side chains in D‐Ser at 4,4′ positions on the biological activity. Another analog [L‐Orn(δ‐Boc)2,2′, ΔAla4,D‐Ser4′]‐GS was prepared from [D‐Ser4,4′]‐GS by t‐butyloxycarbonylation and successive dehydration using dicyclohexylcarbodiimide‐CuCl as dehydrating reagent. The ΔAla residue was asymmetrically hydrogenated to D‐Ala in the presence of Pd‐black. On the microbial assays, [O‐benzyl‐D‐Ser4,4′]‐GS showed high antimicrobial activity as natural GS, but [D‐Ser4,4′]‐GS showed low activity; the structure‐activity relationships of the analogs were discussed.
Synthesis of polypeptide models of elastin
Authors: RAPAKA RAO S. , OKAMOTO KOUJI , LONG MARIANNA M. , URRY DAN W.
Published: August 2010

Synthesis of two copolymers, H‐(φO‐Pro‐Gly‐Gly)n‐Val‐OMe and H‐(φO‐Pro‐Gly‐Gly)n‐Val‐OMe, where φO is Val or Lys and φO is Val or Glu is described. Cross‐linking between the two copolymers is achieved by a coupling reaction between the εe‐amino groups of the lysine containing copolymer and δ‐carboxyls of the glutamic acid of the other copolymer. The cross‐linking reaction was performed during a temperature elicited phase separation with flow orientation of the copolymers. Coacervation of the intermediate polymers is presented, as is the scanning electron micrograph of the insoluble cross‐linked product and its calcifiability as determined with electron probe microanalysis. The purity of the key intermediates and polymers is demonstrated by the usual analytical methods. Carbon‐13 magnetic resonance spectra of the intermediate monomer units are included to validate the purity of their synthesis.
Synthesis and properties of equine β‐melanotropin analogs with substitution in residue position 1
Authors: NÁDASDI LÁSZLÓ , YAMASHIRO DONALD , LI CHOH HAO , IZDEBSKI JAN
Published: August 2010

Five analogs of equine β‐melanotropin have been synthesized by the solid phase method. The NH2‐terminal aspartic acid was substituted with amino acids (Gly, Trp, Ile, Lys and Nα‐acetyl‐Asp) differing widely in physicochemical properties. On the basis of their lipolytic potencies it was concluded that this position plays a negligible role in this activity.
Amino acid composition and zinc content of milk‐clotting protease from Bacillus mesentericus strain 76
Authors: MESROB B.K. , STOEVA P.
Published: August 2010

The milk‐clotting protease from Bacillus mesentericus strain 76 is free of carbohydrate and lacks cysteine and cystine. The amino acid composition indicates a single peptide chain with 304 residues. Five amino acids ‐ aspartic acid, threonine, serine, glycine and alanine ‐ represent one‐half of the total residues. The enzyme contains 35 aromatic amino acids and 103 ionic amino acids. The observed constant value of the ratio Menzyme:AZinc is 1:1 for active and acid denatured enzyme preparations, indicating that 0.1 M acetic acid causes denaturation of the enzyme but it can not eliminate the zinc ions.
Peptides containing dipropylglycine
Authors: HARDY PAUL M. , LINGHAM IAN N.
Published: August 2010

Methods for the incorporation of the hindered amino acid 2‐amino‐2‐propyl‐pentanoic acid (dipropylglycine, Dpg) into peptides have been investigated. Limitations on the preparation of protected derivatives of Dpg are discussed, and common methods of coupling examined. These methods are not subject to problems when used to link protein amino acids to the amino group of Dpg, but steric hindrance severely limits efficient peptide bond formation by the carboxyl group of Dpg. Only two reagents proved useful in this respect. N‐Benzyloxycar‐bonyl (Z) Dpg can be coupled through its derivative with 3‐hydroxy‐4‐oxo‐3,4‐dihydrobenzotriazine; other methods of activation of Z‐Dpg tend to lead to formation of 2‐benzyloxy‐4,4‐dipropyloxazolin‐5(4H)‐one, which resists attack by nucleophiles. 2‐Trifluoromethyl‐4,4‐dipropyloxazolin‐5(4H)‐one, however, which is readily prepared from N‐trifluoroacetyl‐Dpg and thionyl chloride, couples cleanly with other amino acids, making it the reagent of choice for introduction of a Dpg residue.