bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrolysis of various types of ester substrates with linear, cyclic and polymeric peptides containing His, Ser and Asp residues
Authors: NISHI NORIO , NAKAJIMA BUN‐ICHIRO , MORISHIGE MASAYA , TOKURA SEIICHI
Published: August 2010

Catalytic activities of linear, cyclic and polymeric peptides having the sequences of ‐Asp‐ßAla‐Gly‐His‐ßAla‐Gly‐(nonapeptide series) and ‐Asp‐eAhx‐Ser‐eAhx‐His‐eAhx‐ (hexapeptide series) in the hydrolysis of various types of ester substrates were compared with one another and with that of poly (‐His‐ßAla‐Gly) (Poly‐3) which has no Ser or Asp residues. Hydrolytic activity of the hexapeptide series, the cyclic form in particular, was larger than that of the nonapeptide series in many cases such as in the hydrolysis of N‐protected amino acid p‐nitrophenyl esters (Z‐Gly‐ONp, Boc‐Ala‐ONp, Z‐ (l and d) ‐Leu‐ONp, Boc‐ (l and) ‐Phe‐ONp) and anionic 3‐nitro‐4‐acetoxybenzoic acid (NABA). The activities of the polymeric peptides were generally smaller than those of the linear or cyclic peptides. None of the peptides showed the remarkable activity to the hydrophobic substrate with long chain, p‐nitrophenyl laurate (PNPL), and they were almost inactive to bulky p‐nitrophenyl trimethylacetate (PNPTMA) and cationic 3‐acetoxy‐N‐trimethylanilinium iodide (ANTI). Enantiomer‐selectivity in the hydrolysis of N‐protected amino acid p‐nitrophenyl esters and solvent isotope effect in the hydrolysis of p‐nitrophenyl acetate (PNPA) are also reported.
Use of carboethoxysulfenyl chloride for disulfide bond formation
Authors: LE‐NGUYEN DUNG , RIVIER JEAN
Published: August 2010

The use of carboethoxysulfenyl chloride for disulfide bond formation and concomitant cyclization of five peptides was investigated. Even though cyclic peptides were obtained very rapidly and in good yields when cyclization was performed in aqueous media at different pHs (4 to 7), the final crude peptides were found to contain closely related impurities which, in the case of somatostatin and pressinoic acid, were not generated by air oxidation. This observation may limit the use of carboethoxysulfenyl chloride to those cases where other methods of disulfide bond formation prove inadequate.
Synthesis of pseudo‐peptide analogues of the C‐terminal tetra‐peptide of gastrin and evaluation of their biological activity on acid secretion
Authors: RODRIGUEZ MARC , BALI JEAN‐PIERRE , MAGOUS RICHARD , CASTRO B. , MARTINEZ J.
Published: August 2010

The syntheses of pseudo‐tetrapeptides Boc‐Trp‐ψ(CH2‐NH)‐Met‐Asp‐Phe‐NH2 21 and Boc‐Trp‐Met‐ψ(CH2‐NH)‐Asp‐Phe‐NH2 20, representing the C‐terminal tetrapeptide sequence of gastrin, in which amide bonds were replaced by CH2‐NH bond, are described, as well as the syntheses of pseudo‐peptide analogues Boc‐Trp‐ψ(CH2 ‐NH)‐Nle‐Asp‐Phe‐NH2 16, Boc‐Trp‐Nle‐ψ(CH2‐NH)‐Asp‐Phe‐NH2 11, and Boc‐Trp‐Nle‐Asp‐ψ(CH2‐NH)‐Phe‐NH2 5, in which the methionyl residue was replaced by a norleucyl residue. Pseudo‐peptides 16 and 21, in which the amide bond between Trp and Met (or Nle) was substituted by a CH2‐NH) bond, stimulated gastric acid secretion in the rat in vivo. Pseudo‐peptides 11,16,20 and 21, where the amide bond between Met (or Nle) and Asp was replaced by a CH2‐NH bond, did not exhibit any activity on acid secretion in the rat in vivo but were potent inhibitors of pentagastrin‐incluced acid secretion. Peptides 11, 16, 20 and 21 all recognize the gastrin receptor on a mucosal cell preparation. Pseudo‐peptide 5, in which the amide bond between Asp and Phe was replaced by a CH2‐NH bond, was a less potent inhibitor of pentagastin‐induced acid secretion and had a weaker affinity than the other pseudo‐peptides.
Reinvestigation of the disulfide bridge arrangement in human pro‐opiomelanocortin N‐terminal segment (hNT 1–76)
Authors: BENNETT H.P.J. , SEIDAH N.G. , BENJANNET S. , SOLOMON S. , CHRETIEN M.
Published: August 2010

The cystine bridge structure of the amino‐terminal fragment of human proopiomelanocortin has been reinvestigated. Highly purified amino‐terminal fragment 1–76 was rapidly isolated from human pituitaries using only reverse‐phase liquid chromatography (RP‐HPLC). This peptide was then subjected to trypsin and V8‐protease digestion and the products separated by RP‐HPLC> and subjected to amino acid and microsequence analysis. The results show that disulfide bridges link Cys‐2 to Cys‐24 and Cys‐8 to Cys‐20. Amino acid analysis and amino sugar determination confirm (i) the previously proposed sequence and (ii) the suggestion of the presence of two glycosylation sites in this molecule. These are most probably located at Thr‐45 (O‐glycosylation) and at Asn‐65 (N‐glycosylation).
Sequence‐dependence of secondary structure formation
Authors: ALTMANN K.‐H. , FLÖORSHEIMER A. , MUTTER M.
Published: August 2010

The conformational behaviour of the monodisperse amphiphilic oligopeptides (L‐Thr‐L‐Val)n (I and II) and (L‐Ser‐L‐Leu)n (III) for n = 1–4 was investigated by CD spectroscopy in TFE, MeOH and water. A conformational transition random‐coil ‐> ß‐structure was observed for both series: the critical chain length for ß‐structure formation turned out to be dependent on solvent and spatial similarity of the amino acid side‐chains. The very short critical chain‐length for the onset of ß‐structure formation for peptides I and II (n = 3) is explained by the formation of bilayer sheets, in which the minimization of hydrophobic contacts between the amphipilic peptide and the hydrophilic solvent represents an important driving force for ß‐structure formation. The use of amphiphilic peptides for the construction of artificial proteins is briefly discussed.
Purification of three isolectins from root tubers of Trichosanthes kirilowii (Tianhuafen)
Authors: YEUNG H.W. , WONG D.M. , NG T.B. , LI W.W.
Published: August 2010

Proteins precipitated by acetone from an aqueous extract of Trichosanthes kirilowii root tubers contained abortifacient and erythroagglutinating activities. The abortifacient protein was unadsorbed while the erythroagglutinins were adsorbed on DEAE‐Sepharose equilibrated nd eluted with 0.02 M NH4HCO3 containing 0.1 M NaCl. The erythroagglutinins eluted from the ion exchanger were further fractionated on Lacto‐gel and subsequently on Concanavalin A‐Sepharose to yield three lectins.
Influence of Ca2+ binding on the structure and stability of bovine α‐lactalbumin studied by circular dichroism and nuclear magnetic resonance spectra
Authors: Kuwajima Kunihiro , Harushima Yoshiaki , Sugai Shintaro
Published: August 2010

Both the Ca2+‐bound and Ca2+‐free forms of α‐lactalbumin can assume essentially the same folded conformation as evidenced by similarity in their CD and proton n.m.r. spectra. Thermal unfolding followed by the aromatic CD has shown that the stability of the folded state is markedly enhanced by Ca2+ and that the stabilization is almost entirely entropic; addition of 0.1 mM Ca2+ shifts the transition temperature from 40° to 62° in 0.1 M Na+ at pH 7.0. The enthalpy change of the unfolding, coincident between the two forms, is, however, significantly smaller than that known for lysozyme. The n.m.r. spectrum under the condition that both the forms of the protein are in the folded state reflects minor environmental changes of certain protons upon Ca2+ binding, and these changes are shown to afford useful probes for assessment of the location of the binding site. From the pH dependence and temperature dependence of the spectrum and also by using spin decoupling in the aromatic region (6.4–8.7 p.p.m.), it is shown that none of histidyl residues are affected and that at least two tryptophanyl ring protons experience environmental changes upon Ca2+ binding to the folded apo‐protein. Effect of free excess Ca2+ on the spectrum has also shown that in native α‐lactalbumin there is only one Ca2+‐binding site that is detectable by the present method.
Synthesis of plasmin substrates and relationship between their structure and plasmin activity
Authors: Okada Yoshio , Tsuda Yuko , Teno Naoki , Wanaka Keiko , Sasaki Kuniko , Hijikata Akiko , Naito Taketoshi , Okamoto Shosuke
Published: August 2010

The plasmin substrates, D‐Ile‐Phe‐Lys‐pNA (I), 3‐MV‐Phe‐Lys‐pNA (II), Ile‐Phe‐Lys‐pNA (III), D‐Pro‐Phe‐Lys‐pNA (IV), CP‐Phe‐Lys‐pNA (V) and Pro‐Phe‐Lys‐pNA (VI), were synthesized by the conventional solution method and the kinetic parameters of their amidolysis by plasmin were determined. It was found that the free amino group of the D‐amino acid in substrates (I) and (IV) made a contribution to an increment in affinity between the substrate and plasmin.
Purification and characterization of rabbit muscle acylphosphatase in the thiol (‐SH) form
Authors: BERTI A. , STEFANI M. , CAMICI G. , MANAO G. , CAPPUGI G. , DEGL'INNOCENTI D. , RAMPONI G.
Published: August 2010

Modifications in the muscle acylphosphatase purification procedure enabled us to isolate the enzyme with its sole cysteine in the ‐SH form; this enzyme form is the most abundant in vivo. Our data demonstrate that the enzyme forms purified by previously reported procedures can be easily derived from a reaction of the SH‐enzyme with oxidized glutathione. Probably most, or even all, of these enzyme forms are artifacts due to the purification. The SH‐acylphosphatase shows kinetic parameters similar to those reported for the mixed disulfide with glutathione and S‐S dimer, except for the specific activity value, which is about twice as much, and the Km, which is reduced.
Polydepsipeptides. 13
Authors: MAMMI STEFANO , GOODMAN MURRAY
Published: August 2010

The synthesis of three collagen model analogs is described: Ac‐Ala‐Gly‐Pro‐Ala‐Gly‐Pro‐NHMe, Ac‐Ala‐Gly‐Pro‐Ala‐Glc‐Pro‐NHMe, and Ac‐Ala‐Glc‐Pro‐Ala‐Gly‐Pro‐NHMe, where Glc stands for glycolic acid. The 1H‐n.m.r. properties of these compounds in dimethylsulfoxide‐d6 and trifluoroethanol are described. While in DMSO‐d6 the compounds are random, in TFE the glycine amide protons seem to be less solvent exposed than the other amide protons. Little difference was found in the behavior of the three compounds.
Deamidation of the asparaginyl‐glycyl sequence
Authors: MEINWALD YVONNE C. , STIMSON EVELYN R. , SCHERAGA HAROLD A.
Published: August 2010

The deamidation of Ac‐Asn‐Gly‐NHMe and Ac‐Isn‐Gly‐NHMe has been studied as a model for the facile deamidation of the Asn‐Gly sequence in proteins. At alkaline pH, the product in each case is an identical mixture of Ac‐α‐Asp‐Gly‐NHMe (˜ 22%) and Ac‐β‐Asp‐Gly‐NHMe (˜ 78%) as determined by n.m.r. spectroscopy. Because this same ratio is obtained from both Ac‐Asn‐Gly‐NHMe and Ac‐Isn‐Gly‐NHMe, the postulated mechanism, that deamidation proceeds through a cyclic imide intermediate, is confirmed. Unlike peptides of aspartyl esters, cyclization does not occur under nonaqueous conditions or at low pH in aqueous solution.
Functional Kunitz inhibitor binding domain in plasmin‐derived light chain as shown by affinity chromatography
Authors: CHAUVET JACQUELINE , CHABBAT JACQUES , ACHER ROGER
Published: August 2010

The light chain of plasmin, prepared by selective reduction of the interchain disulfide bridges, can be separated from the heavy chain by affinity adsorption onto Kunitz inhibitor/Sepharose. This adsorption involves the active center of plasmin because it does not occur if the light chain is derived from a plasmin previously blocked by the active site titrant p‐nitrophenyl‐p'‐guanidinobenzoate. It can be deduced that the conformation of the inhibitor binding domain of plasmin is preserved in the free light chain.
Dehydro‐dermorphins
Authors: PIERONI OSVALDO , FISSI ADRIANO , SALVADORI SEVERO , BALBONI GIANFRANCO , TOMATIS ROBERTO
Published: August 2010

Dehydropeptide analogs of dermorphin (H‐Tyr‐D‐Ala‐Phe‐Gly‐Tyr‐Pro‐Ser‐NH2) and N‐terminal fragments containing one or two dehydrophenylalanine residues in the 3rd and/or 5th position, have been investigated by means of CD spectroscopy. The results indicate that the above dehydropeptides can adopt different conformations in alcohol and water solutions. In methanol and trifluoroethanol, the CD spectra are mainly consistent with the presence of folded structures, probably stabilized by intramolecular hydrogen bonds. In water, conversely, CD data indicate disruption of ordered structures and formation of preferentially extended flexible conformations. Models of the involved folded structures are tentatively proposed, taking into account the geometric features of dehydro residues and their tendency to favor hydrogen‐bonded 10‐membered rings.
1H n.m.r. studies of insulin
Authors: RAMESH V. , BRADBURY J.H.
Published: August 2010

1H n.m.r. studies at 270 MHz were made of the transformation of 2 Zn insulin hexamer to 4 Zn hexamer produced by the addition of anions (thiocyanate ion). Four separate H2 histidine resonances were observed for the B5 and B10 histidines in 2 Zn hexamer at pH 7 and 9 and four separate resonances also occurred in the 4 Zn hexamer. The observation of these resonances and others from phenylalanine, tyrosine and leucine residues showed that the 2 Zn to 4 Zn transformation probably occurred in solution in a similar manner to that observed in the crystal. Furthermore as occurred in the crystal, it was found that in solution the transformation was reversible (on removal of thiocyanate) and that 2 Cd insulin was unable to undergo the transformation. Des‐Phe‐B1‐insulin did not undergo the transformation. Addition of SCN˜ to Zn‐free insulin (mainly dimer) produced only a small transformation, consistent with the idea that Zn2 + promotes formation of hexamer from dimer but probably does not otherwise affect the transformation.
In vitro interaction of opioid peptides with phospholipids
Authors: VITA FABRIZIO , VENTURELLI FRANCESCA , ROSCETTI GIANNA , RODA L. GIORGIO
Published: August 2010

The binding of tritiated Leu‐enkephalin to phosphatidylserine and phosphatidylcholine vesicles, both unmodified and modified by the incorporation of free fatty acid, has been studied by steric exclusion chromatography, ultraviolet difference spectroscopy and fluorescence anisotropy. The results obtained tend to confirm that both ionic and hydrophobic interactions are important in the binding phenomena. On the other hand, it seems likely that steric factors play a very limited role in the recognition of the phospholipid by the opioid peptide. Finally, these results confirm the existence of three complexes of different size, as already demonstrated. But, unlike the previously presented results, they stress the importance of the larger of the three complexes formed through binding.
Peptides related to the calcium binding domains II and III of calmodulin
Authors: BUCHTA RICHARD , BONDI ELCHANAN , FRIDKIN MATI
Published: August 2010

Three hexadecapeptides which correspond to the putative Ca2+ binding domains II and III of calmodulin were synthesized employing solid phase methodology. One of the peptides contained an internal cystine bridge which was formed while the corresponding linear peptide was still attached to the polymeric carrier. The interaction of the synthetic peptides with calcium ions was investigated using Tb3+mediated fluorescence. Binding was of the order Cal2 > Cal3 > Cal3C (Fig. 1) with binding constants KTb= 0.68 times 10‐5, 0.54 times 10‐5, and 0.21 times 10‐5 M‐1 respectively. Biological activity of the compounds was assessed by measuring their stimulatory effect on erythrocyte membrane (Ca2++ Mg2+)‐ATPase activity For 50% activity as compared with CaM, the concentration of peptides required was for Cal2, Cal3 and Cal3C, 50, 100 and 167 times higher than CaM, respectively. The results suggest that the three synthetic peptides possess certain calmodulin‐like features.
Detection of desamido forms of purified bovine growth hormone
Authors: SECCHI C. , BIONDI P.A. , NEGRI A. , BORRONI R. , RONCHI S.
Published: August 2010

Tryptic peptide mapping and amino acid sequencing were used for the identification of desamido forms of bovine growth hormone. The major desamido forms of bovine growth hormone resulted from deamidation of asparagine in position 13, 148 and glutamine 140. These forms did not seem to be produced by prolonged treatment of bovine growth hormone in tryptic hydrolysis.
Protein structural homology: a metric approach
Authors: USHA R. , MURTHY M.R.N.
Published: August 2010

The flexibility of the polypeptide fold of proteins is essentially due to the rotational freedom about the main chain bonds involving Cα atoms. The polypeptide fold can therefore be represented by virtual bonds joining consecutive Cα atoms. The ordered sequence of virtual torsion and bond angles involving these bonds can be used to specify the fold. Such representations can then be compared to reveal structural similarities using the Needleman & Wünsch algorithm, which has been developed for comparison of amino acid sequences. Such an approach is presented and illustrated with examples. The method is suitable for detecting structural similarities that extend over 7 or more residues.
Conformation of the glycotripeptide repeating unit of antifreeze glycoprotein of polar fish as determined from the fully assigned proton n.m.r. spectrum
Authors: BUSH C. ALLEN , FEENEY ROBERT E.
Published: August 2010

With its simple glycotripeptide repeating structure the antifreeze glycoprotein of polar fish may be an especially simple conformational mode for mucin glycoproteins with similar but more complex structures. The fully assigned proton n.m.r. spectrum confirms the anomeric configurations of the hexapyranosidic sugars of the side chains and the coupling constants of the α GalNAc and the β Gal residues show both to be in the expected 4C1 chair conformation. The assignment of a single resonance for each proton of the (Ala‐Thr‐Ala)n repeat unit coupled with the observation of long range nuclear Overhauser effects (n.O.e.) implies a three‐fold repeating conformation. The resonances of the two alanines are distinct and can be assigned to their correct positions in the peptide sequence by n.O.e. observed at the amide proton resonances on saturation of the α proton signals. The amide proton coupling constants of all three peptide residues are similar and imply a limited range of peptide backbone torsion angles, CN. The large n.O.e. which has been observed between the amide proton and the α proton of the residue preceding it in the sequence implies large positive values for the peptide dihedral angle, CC. Limits are placed on possible values of side chain dihedral angles by the observation of the coupling constant between the α and β protons of the threonyl residue. The observation of n.O.e. between the anomeric proton of GalNAc and the threonyl side chain protons gives information on the conformation of the α glycosidic linkage between the disaccharide and the peptide. n.O.e. observed between the protons of the β glycosidic linkage indicates the conformation of the disaccharide and the large amide proton coupling constant of the GalNAc residue shows a trans proton relationship. The spectroscopically derived data have been combined with conformational energy calculations to give a conformational model for antifreeze glycoprotein in which the hydrophobic surfaces of the disaccharide side chains are wrapped closely against a three‐fold left handed helical peptide backbone. The hydrophilic sides of the disaccharides are aligned so that they may bind to the ice crystal face, which is perpendicular to the fast growth axis inhibiting normal crystal growth.
A spectroscopic study of the interaction of allylisothiocyanate with mustard 12S protein
Authors: MURTHY N.V. KISHORE KUMAR , RAO A.G. APPU , RAO M.S. NARASINGA
Published: August 2010

The intraction of allylisothiocyanate (AIT) with mustard 12S protein resulted in a change in the absorption spectrum of the protein below 280nm without any shift in the γmax. The spectrophotometric titration of mustard 12S protein after interaction with AIT suggested the involvement of phenolic groups. Upon interaction with AIT, a new band at 250nm appeared in the near ultraviolet circular dichroism spectrum of the protein. However, no change occurred in the far ultraviolet circular dichroism spectrum. Circular dichroism measurements with amino acids suggest the possible involvement of tyrosine residues in the interaction of AIT with mustard 12S protein.
Improved deprotection of cysteine‐containing peptides in HF
Authors: HEATH WILLIAM F. , TAM JAMES P. , MERRIFIELD R.B.
Published: August 2010

The deprotection of S‐4‐methylbenzyl‐cysteine in HF was studied as a function of acidity and scavengers employed and a highly effective procedure was developed. Under conditions of low acidity which promote SN2 deprotection of benzyl alcohol‐derived protecting groups of amino acid side‐chain functionalities, i.e. low HF (HF:DMS, 1:3, v/v), little or no deprotection of S‐4‐methylbenzyl cysteine was observed. Under conditions of high acidity (90% HF), recovery of cysteine was only 79% using the conventional scavenger, anisole. However a combination of the scavengers p‐cresol and p‐thiocresol provided nearly quantitative recovery of the cysteine thiol, with the preferred deprotection conditions being HF:p‐cresol:p‐thiocresol (90:5:5, v/v), 0°C, 1 h. The possibility that the sulfoxide of the protected cysteine thioether was involved in cysteine side reactions was investigated. The formation of the sulfoxide was found to be low (0.15% per residue added) under standard solid‐phase peptide synthesis conditions. Since the sulfoxide derivative was resistant to deprotection in high HF, two methods for the reduction of the molecule to the thioether were developed. One method involved the reduction of the sulfoxide in HF at intermediate acidity levels (HF:DMS, 40:60, v/v), 0°, 4h. The other method involved a mixture of TFA, DMS and CH2Cl2 (45:10:45, v/v) containing (Et)4 NCl ˜ H2O (50 equiv. per cysteine residue) which efficiently reduced both free and resin‐bound S‐4‐methylbenzyl cysteine sulfoxide (t1/2= 35 min). Both methods also reduced methionine sulfoxide to methionine.
Reinvestigation of the crystal structure of β‐alanine
Authors: PAPAVINASAM E. , NATARAJAN S. , SHIVAPRAKASH N.C.
Published: August 2010

A reinvestigation of the crystal structure of β‐alanine was carried out. The structure is orthorhombic, space group Pbca, with eight molecules per unit cell. Cell parameters were a = 9.882 (2), b = 13.807 (2), and c = 6.086 (2) Å. Three‐dimensional intensity data collected in a CAD‐4 diffractometer using Cu K α radiation was used in the least‐squares refinement leading to a final R value of 0.038. The average standard deviations in bond lengths and angles were 0.002 Å and 0.2°, respectively. The corresponding values in the earlier work of José & Pant (1965) were 0.01 Å and 0.6°, respectively. The positions of all the hydrogen atoms were located in the present study. The amino nitrogen forms three hydrogen bonds of nearly equal bond lengths and angles, with the oxygen atoms. The β‐alanine molecules exist in the crystal as zwitterions.
Oxygen‐18 isotope labeling and its effect on carbon‐13 chemical shifts of the peptide bond
Authors: PONNUSAMY E. , FIAT D. , JONES C.R.
Published: August 2010

The effects of 18O isotopes on 13C NMR chemical shifts of peptide carbonyl carbons were found to be 0.028 ppm for glycylglycine and 0.029 ppm for glycylproline at 50.31 MHz.
Synthesis of a γ‐carboxyglutamic acid containing heptapeptide corresponding to bovine prothrombin residues 17–23
Authors: HOKE RANDAL A. , DEERFIELD DAVID W. , PEDERSEN LEE G. , KOEHLER KARL A. , HISKEY RICHARD G.
Published: August 2010

The vitamin K‐dependent proteins involved in blood coagulation processes each contain a small cystine loop with the sequence ‐Gla‐Cys‐X‐Gla‐Gla‐X‐Cys‐. A method for the synthesis of the heptapeptide derivative representing the 17–23 sequence of bovine prothrombin, Z‐Gla‐Cys‐Leu‐Gla‐Gla‐Pro‐Cys‐OBzl, has been developed. The 25 Mg2+ n.m.r. spectrum of the heptapeptide derivative has been obtained and is compared to the n.m.r. spectra obtained from the interaction of 25 Mg2+ with Z‐Gla‐OMe and Z‐Gla‐Gla‐OMe.
Enantioselective synthesis of (R)‐ and (S)‐2‐methyl‐[3,3,2‐2H3] alanines
Authors: SUBRAMANIAN PULLACHIPATTI K. , WOODARD RONALD W.
Published: August 2010

The synthesis of optically pure (R)‐ and (S)‐2‐methyl‐[3,3,3‐2H3] alanines of biological interest is described. The stereochemistry of the reaction of the lithio derivative of (R)‐(©)‐2,5‐dimethoxy‐3‐benzyl‐3‐methyl‐3, 6‐dihydropyrazine with alkyl and deuterated alkyl iodides is discussed. The configuration of the newly formed center of chirality in (R)‐ and (S)‐2‐methyl‐[3,3,3‐2H3] alanines is derived from 1 H NMR.
Aromatic side chain rotational preference
Authors: ZHANG WEIGUO , ANTEUNIS MARC J.O. , BORREMANS FRANS A.M.
Published: August 2010

The 1H NMR spectra of the L, L and D, L diastereomers of the protected linear dipeptides Boc‐ (and Tfa)‐Ala‐N(Me)Ala‐OMe, Boc‐ (and Tfa)‐Phe‐N(Me)Ala‐OMe, Z‐Ala‐(Λ‐thia)Pec‐OMe and Z‐Phe‐(Λ‐thia)Pec‐OMe (Pec = pipecolic acid) have been recorded in chloroform, dimethylsulfoxide and benzene at room temperature. The observed side chain vicinal coupling constants and ring current effects indicated a conformational preference of the Phe side chain for the “extended‐to‐oxygen” rotamer (X1 torsion angle of 180°) in the cis isomer (ω= 0°) of the L, L‐ and in the trans isomer (ω= 180°) of the D, L‐dipeptides. Concomitantly, these L, L‐cis and D, L‐trans isomers were more populated in the Phe‐Xxx as compared to the Ala‐Xxx sequences (Xxx = the imino acid). The results are explained in terms of an attractive interaction between the aromatic ring and the succeeding amide bond.
New synthesis and biological activity of the cyclic tetrapeptides tentoxin and [Pro 1] tentoxin
Authors: EDWARDS JUDSON V. , LAX ALAN R. , LILLEHOJ EIVIND B. , BOUDREAUX GORDON J.
Published: August 2010

The cyclic tetrapeptide tentoxin and the conformationally related analog [Pro1] tentoxin have been synthesized by a new solution methodology. D, L‐3‐phenyl‐serine was employed as a synthetic precursor to the Z‐dehydrophenylalanine substituent. Increased yields of both compounds were obtained when a modified cyclization procedure was employed through ring closure from the N‐terminal substituents of N‐methylalanine and proline to a C‐terminal glycine. Biological activities were determined in a seedling assay used to measure chlorosis induction. Both tentoxin and [Pro1] tentoxin exhibited similar chlorosis inducing activity. Whole leaf extracts of chlorotic, [Pro1] tentoxin‐treated seedling leaves lacked active polyphenoloxidase when subjected to electrophoretic analysis. Coupling factor1 (CF1) ATPase isozymes were assayed for ATPase activity in 10μuM‐100 μuM solutions of tentoxin and [Pro1] tentoxin. CF1 ATPase inhibition was observed for both tentoxin and [Pro1] tentoxin. Inhibition of a single ATPase isozyme by tentoxin was alleviated at or above 50μuM while [Pro1] tentoxin inhibited two CF1 ATPases at concentrations up to 110μuM. No alleviation of ATPase inhibition was noted for higher concentrations of [Pro1] tentoxin.
Polytetrapeptide of elastin
Authors: URRY DAN W. , HARRIS R. DEAN , LONG MARIANNA M. , PRASAD KARI U.
Published: August 2010

High molecular weight polytetrapeptide of elastin, (L‐Val1‐L‐Pro2‐Gly3‐Gly4)n, was synthesized using activation of the (GGVP) permutation for polymerization. The temperature‐dependence of aggregation was characterized as a function of concentration and the circular dichroism spectra were obtained in the 20° to 70°C temperature range. The latter showed an inverse temperature transition centered near 50°C in which polypeptide order increased on raising the temperature. A concentration of 0.6 g of polytetrapeptide in 1 g of water was Λ irradiation cross‐linked (20 Mrad) to form an elastomeric matrix. A study of the temperature‐dependence of elastomeric force demonstrated a transition toward increased force on raising the temperature with a midpoint of the transition near 50°C. Thus, there is a correlation between increase in intramolecular order and elastomeric force development. These results are compared to previous results on the polypentapeptide of elastin, (VPGVG)n and on an analog, (IPGVG)n, to demonstrate that the temperature of the transition is proportional to the hydrophobicity of the repeating unit. The point is noted that the elastomeric force development correlates better with intramolecular ordering than with intermolecular processes.
Empirical rules predicting conformation of cyclic tetrapeptides from primary structure
Authors: KATO TETSUO , LEE SANNAMU , SHIMOHIGASHI YASUYUKI , TONE AKIRA , KODERA YASUSHI , IZUMIYA NOBUO
Published: August 2010

A useful set of empirical rules is put forward to predict the conformations of cyclic tetrapeptides and cyclic tetradepsipeptides on the basis of primary structure, briefly presented as follows: 1. A conformation allowing an intramolecular hydrogen bond (IMHB) of γ‐turn is preferred, and an ester bond always adopts a trans form. 2. On a right‐handed peptide ring, the carbonyl group acylating a D residue is oriented to the upper side of the main ring. 3. The carbonyl group acylating a d proline or an N‐methyl‐d‐amino acid residue is oriented to the lower side of the ring, forming a cis bond. 4. The lddl configurational sequence adopts a cis‐trans‐cis‐trans backbone with Ci symmetry. 5. A glycine residue behaves as a d residue in an l‐peptide. Conformations of cyclotetrapeptides containing two glycine residues at diametric positions or containing an N‐methyl‐dehydroamino acid residue are predicted by use of appendices of rule 5. Almost all conformations of cyclic tetrapeptides are predicted by these rules. Energetical rationalization of the rules and prediction of possible new conformations are described. Conformations of cyclo (‐l‐Pro‐l‐Leu‐d‐Tyr(Me)‐l‐Ile‐)(1) and cyclo (‐l‐Pro‐d‐Leu‐d‐Tyr(Me)‐l‐Ile)(2) are compared. Results of n.m.r. experiments showed that compound 1 adopts a unique cis‐trans‐trans‐trans backbone with a γ‐turn IMHB, and 2 has a cis‐trans‐cis‐trans backbone with Ci symmetry. These observations confirmed the rules described above. Peptides 1 and 2 are the first diastereomeric peptides with trans (ld) and cis (dd) secondary amide bonds.
Synthesis of new head‐activator analogues and their application for improved radioimmunoassays
Authors: BODENMÜLLER H. , ESCHER E. , ZACHMANN B. , SCHILLING E.
Published: August 2010

New analogues of head activator were produced for receptor and radioimmunoassay studies. The precursor molecules [(4′‐I)Phe11] head activator and [Tyr11] head activator were synthesised for catalytic tritiation and iodination, respectively. With the tracer [(3,5‐125 I2)Tyr11] head activator the sensitivity range of the radioimmunoassay was 5–100 fmol.
1H‐n.m.r. study of the folding of ribonuclease 12‐(β‐(3‐pyridyl)‐l‐Ala) S‐peptide (1–14)
Authors: RICO M. , BERMEJO F.J. , SANTORO J. , NIETO J.L. , GALLEGO E. , HERRANZ J. , VOSKUYL‐HOLTKAMP I. , SCHATTENKERK C.
Published: August 2010

The 1H‐n.m.r. spectra (360 MHz) of 12‐(β‐(3‐pyridyl)‐l‐Ala) ribonuclease S‐peptide (1–14), a tetradecapeptide incorporating (β‐3‐pyridyl‐l‐Ala) instead of His at position 12, have been assigned. The shift vs. temperature dependence has been analyzed at three different pD's in terms of a two‐state helix (3–13) ± coil equilibrium, and the corresponding values for the thermodynamic quantities ΔH° and ΔS° determined. Helix populations at 0°C have been measured as a function of pD, showing their dependence on two apparent pKa's at ˜ 3.3 and 5.5, with a maximum at pD ˜ 4.2. All the obtained results show that the new peptide has very similar folding properties to those shown by S‐peptide and particularly to those of C‐peptide. The 3–13 helix formed is stabilized by two interactions: a salt‐bridge Glu 2‐. Arg 10+ and a partial stacking between the aromatic rings of residues Phe 8 and His 12. Calculations involving ring current shifts and potential energies validate the possible existence of this latter interaction, which must present a local geometry defined by χ1X8 180°, χ2X8 100°, χ112 – 60 and χ212 80.
Conformational studies on polypeptide models of collagen. Poly(Gly‐Pro‐Val), poly(Gly‐Pro‐Met), poly(Gly‐Val‐Pro) and poly(Gly‐Met‐Pro)
Authors: GUANTIERI V. , TAMBURRO A.M. , CABROL D. , BROCH H. , VASILESCU D.
Published: August 2010

The title polytripeptides were synthesized and studied experimentally, by circular dichroism, and theoretically, by quantum mechanical methods. With the exception of poly(Gly‐Pro‐Val), which was found to be essentially structureless in solution, the other polymers adopt folded conformations, most probably of type II β‐bends. Conclusions from theoretical studies were generally in agreement with the experimental results. In particular, it is noteworthy that the optimized (φ, ø) maps for poly(Gly‐Pro‐Met) showed the absolute minimum (φ = 60°, ø = 0°) located inside the βII bend space.
Amino acid sequence of toxin XI of the scorpion Buthus occitanus tunetanus. Evidence of a mutation having an important effect upon neurotoxic activity
Authors: SAMPIERI F. , HABERSETZER‐ROCHAT C. , MARTIN M.‐F. , KOPEYAN C. , ROCHAT H.
Published: August 2010

The complete amino acid sequence of toxin XI of the North African scorpion Buthus occitanus tunetanus has been elucidated by automatic sequencing of the reduced and alkylated toxin and of the peptides obtained after tryptic cleavage restricted to arginyl bonds. This toxin is structurally homologous to toxin II of Androctonus australis Hector, the most active among the α‐toxins, but is far less potent, both in vivo and in vitro. This work points out 12 mutations, many of which are conservative. Nevertheless, the most striking difference is the replacement of the lysine residue at position 58, known to be important in the activity of AaH toxin II, by a valine residue. Thus, it seems that the presence of a positive charge at this location facilitates the interactions between the receptor on the sodium channel and the α‐type toxins.
Synthesis and biological activity of tuftsin and rigin derivatives containing monosaccharides or monosaccharide derivatives
Authors: ROCCHI R. , BIONDI L. , CAVAGGION F. , FILIRA F. , GOBBO M. , DAGAN S. , FRIDKIN M.
Published: August 2010

Synthesis of some modified rigins is described in which either D‐gluconic acid or 2‐amino‐2‐deoxy‐β‐D‐glucopyranose have been linked to the parent molecule through amide bonds involving the α‐amino function, α‐carboxyl function or the γ‐amide function of glutamine in position 2. Glu2‐rigin and D‐gluconyl‐Glu2‐rigin have also been synthesized. Binding and phagocytosis assays have been carried out on the rigin derivatives and on some glycosylated tuftsin derivatives as well. Of all the tested peptides only rigin enhanced the phagocytic capacity of mouse peritoneal macrophages to the same extent as tuftsin. The peptides H‐Thr‐Lys‐Pro‐Arg‐NH‐Glc and Nα‐gluconyl‐Gly‐Glu‐Pro‐Arg‐OH slightly enhanced phagocytosis. H‐Thr[(α + β)‐O‐glucosyl]‐Lys‐Pro‐Arg‐OH was found to displace 3H‐tuftsin even better than tuftsin but lacked the ability to stimulate phagocytosis.
Reactivity of consecutive basic amino acid residues in peptides
Authors: BAYLE‐LACOSTE M. , DE TINGUY‐MOREAUD E. , GEOFFRE S. , NEUZIL E.
Published: August 2010

Different tetrapeptides of general formula L‐Ala‐X‐X‐Gly, possessing a basic doublet in the second and third position (X = Arg or Lys), have been synthesized as free or N‐acetylated molecules. The chemical reactivity of the arginine guanidino group and of the lysine e‐amino group were studied using respectively the Sakaguchi and the orthodiacetylbenzene reactions, in the tetrapeptides as well as in related molecules. In both cases, the colour yield is markedly influenced by the length of the polypeptide chain and by the relative positions of the arginine and lysine residues, suggesting the occurrence of intramolecular bonds within the tetrapeptide molecule. Tryptic hydrolysis of the tetrapeptides was followed by evaluating the amino acids or peptides which appear to be specific for the different possible cleavages at the arginyl or at the lysyl bonds. The susceptibility to trypsin of the carboxylic group of the second basic amino acid decreases progressively in the order Lys‐Arg > Arg–Arg ± Lys–Lys > Arg–Lys, which shows a fair correlation with the intra‐cellular cleavage of the bonds observed during the processing of preproteins or of the precursors of several physiologically active peptides.
Synthesis and assay of tyrosinated analogs of a crustacean pigment‐dispersing neuropeptide hormone
Authors: RIEHM JOHN P. , RAO K. RANGA
Published: August 2010

In an effort to obtain biologically active tyrosine analogs of the octadecapeptide pigment‐dispersing hormone (β‐PDH) of the fiddler crab Uca pugilator, we have synthesized [Tyr15]‐ and [Nle18]‐β‐PDH, as well as eight tyrosine analogs of [Nle15]‐β‐PDH by the solid‐phase method. Each analog was purified to homogeneity by gel filtration, ion‐exchange chromatography, and partition chromatography. When tested for melanophore pigment‐dispersing activity in destalked Uca, [Nle15, Tyr16]‐β‐PDH and [Nle15]‐β‐PDH were found to be 31‐fold and 16‐fold more potent, respectively, than β‐PDH. Somewhat reduced potency was displayed by [N‐Tyr,Nle15]‐β‐PDH (81%) and [Nle15, Tyr17]‐β‐PDH (26%). All other analogs, including [Nle15, Tyr19]‐β‐PDH and the four derivatives of [Nle15]‐β‐PDH obtained through substitution for nonpolar amino acid residues at positions 4, 5, 8, and 11 in the primary structure, showed marked decrease in biological activity (0.01 to 2% potency).
CD‐n.m.r. study of the solution conformation of bradykinin analogs containing α‐aminoisobutyric acid
Authors: CANN JOHN R. , LONDON ROBERT E. , UNKEFER CLIFFORD J. , VAVREK RAYMOND J. , STEWART JOHN M.
Published: August 2010

The conformation in aqueous solution of several α‐aminoisobutyric acid (AIB)‐containing analogs of bradykinin (BK) has been probed by complementary CD and 1H n.m.r. measurements. The conclusion reached is that substitution of AIB for Pro2 and/or Pro3 in BK stabilizes a degree of β‐turn conformation in the N‐terminal tetrapeptide moiety of the resulting analogs. Changing the solvent from water to DMSO or TFE further enhances the contribution of particular hydrogen bonded structures to the time‐averaged conformation of these peptides. Bradykinin and [AIB7]‐BK adopt similar hydrogen bonded conformations in TFE, apparently with a contribution from a β‐turn involving their common Arg1‐Pro2‐Pro3‐Gly4 moiety. The contrasting biological activities of BK and its AIB‐analogs are considered in terms of the conformational analogy between the AIB‐residue and cis1 Pro and the propensity for a β‐turn at the N‐terminus of the peptide.
β‐Endorphin: peripheral opioid activity of homologues from six species
Authors: HO CHEWN LANG , KO JANE LING , LI CHOH HAO
Published: August 2010

The peripheral opioid activity of six homologous β‐endorphins (β‐EPs) were assayed on the guinea pig ileum and the vas deferens of the mouse, the rat and the rabbit. In the guinea pig ileum assay, human β‐EP (βh‐EP) was less potent than camel, turkey, and ostrich β‐EPs, of the same potency as equine β‐EP and more active than des‐acetyl salmon β‐EP. In the rat vas deferens, mammalian β‐EPs showed higher activity than those from the bird and the fish, whereas in the mouse vas deferens assay, βh‐EP is more active than those from other species. In the rabbit vas deferens, however, all homologous β‐EPs show very weak activity. The relative potency of β‐EP homologues obtained from rat vas deferens assay is in good correlation with the analgesic potency, while the receptor binding activity does not correlate with any of the four bioassays, but appears to be related to the charge properties of the peptides.
Effects of carbamoylation with alkyl isocyanates on the assay of proteins by dye binding
Authors: LEA MICHAEL A. , LUKE ALEYKUTTY
Published: August 2010

The effect of carbamoylation with alkyl isocyanate was used both to monitor the stability of the isocyanates and to study the influence of charge modification on protein assay. Carbamoylation of poly (L‐lysine) with methyl isocyanate, ethyl isocyanate and 2‐chloroethyl isocyanate was observed to decrease binding of methyl orange. The data emphasized the lability of alkyl isocyanates and indicated the importance of preparing aqueous solutions at low temperatures for studies on protein carbamoylation. After carbamoylation of several proteins, there was decreased metachromasia on binding to Coomassie Blue G. Poly (L‐lysine) and H1 histone showed anomalous behavior in that with low concentrations of Coomassie Blue G the metachromasia was increased by carbamoylation, but at high concentrations of the dye the metachromasia was decreased by carbamoylation. In contrast to some reports in the literature, the data indicated that there is not always a simple relationship between the positive charge on a protein and the interaction with anionic dyes.
Conformation of glycyl residues in globular proteins
Authors: RAMAKRISHNAN C. , SRINIVASAN N. , PRASHANTH D.
Published: August 2010

Glycine is unique among the amino acids in view of its symmetric nature. While the overall distribution of glycyl residues in the (φ, ø) plane is near‐symmetric, there can be certain preferences for the individual conformations. An analysis of the observed glycyl conformations in 70 proteins has been carried out to find the influence of residues adjoining the glycyl residues. For this purpose, the (φ, ø) plane has been divided into two regions: (a) the region in which φ is negative and (b) the region in which φ is positive. The analysis is done in terms of the number of conformations occurring in these regions. It has been found that while the overall percentage distribution of glycyl residues between the positive and the negative φ regions is 54:46, the distribution shows asymmetry when the examples are sorted out in terms of X‐Gly and Gly‐Y doublets. The asymmetry becomes more prominent when the data are sorted out into triplets X‐Gly‐Y. Using the available information, it has been possible to designate 25 triplets as P‐predominant and 19 as N‐predominant. An examination of P‐predominant triplets for possible occurrence in β‐bends having one of the conformations in the positive φ region shows that only 25% are of this nature. Thus, the P‐preference of P‐predominant triplets is not an outcome of the bend formation alone and must be an inherent property of these triplets.
Hybridization and partial cDNA sequence analyses of bovine lung angiotensin I‐converting enzyme*
Authors: DELUCA–FLAHERTY CAMILLE , SCHULLEK JOHN R. , WILSON IRWIN B. , HARRIS ROBERT B.
Published: August 2010

The mRNA encoding angiotensin I‐converting enzyme, a zinc‐metallo dipeptidyl carboxyhydrolase, has been identified in extracts prepared from bovine lung tissue. Bovine lung poly(A) + mRNAs were subjected to electrophoresis and northern blot hybridization analysis using a radiolabeled synthetic 24‐deoxy‐oligonucleotide probe complementary to eight codons for amino acids at the active‐site of the enzyme (Harris, R.B. & Wilson, I.B., J. Biol. Chem. 260, 2208–2211, 1985). This amino acid sequence contains the catalytic glutamic acid residue. A single RNA species (4 kb) was detected which is 1 kb larger than predicted from the molecular weight of the enzyme. The excess nucleic acid composition may be due to leader and/or trailer sequences or the RNA may encode a high molecular weight precursor form of the enzyme. We have cloned an Eco R1‐HindIII digest fragment (1400 bp) of the duplex cDNA derived from the bovine lung converting enzyme poly(A) + mRNA and also Bal31 deletion fragments generated from the 1400 bp clone. Several of the Bal31 clones contain the active‐site sequence codons of the enzyme and the complete cDNA sequence of one of these (72 bp) has been determined. We found the amino acid sequence at the active site to be ‐Phe‐Thr‐Glu‐Leu‐Ala‐Asn‐Ser‐, containing the catalytic Glu residue. This sequence is identical with the sequence that we previously determined by manual Edman degradation analysis of the appropriate active‐site peptide except that we now find Asn instead of Asp. We have sequenced 670 bp of the 1400 bp clone but have not yet overlapped the active‐site sequence. The deoxyoligonucleotide probe directed against the active‐site of lung converting enzyme also hybridizes with a poly(A) + mRNA from bovine atrial tissue, a tissue that does not contain converting enzyme. The atrial mRNA we have detected very probably is the mRNA that encodes atrial peptide convertase, a metallo dipeptidyl carboxyhydrolase that is involved in processing the atrial natriuretic peptides (Harris, R.B. & Wilson, I.B., Peptides 6, 393–396, 1985). The atrial enzyme appears to share active‐site homology with the converting enzyme.
Human growth hormone. Immunochemical characterization of polypeptide fragments purified by reversed phase‐high performance liquid chromatography
Authors: MOLLERACH‐GOBBI BEATRIZ , VITA NATALIO , POSKUS EDGARDO , PENA CLARA
Published: August 2010

Using HPLC it was possible to obtain fragments of human growth hormone, enzymatically or chemically cleaved, with a purity not previously attained. The immuno‐reactivity of these fragments was assayed with polyclonal or mouse monoclonal antibodies to the native hormone. Antigenicity was found in the peptide sequences derived from the two thirds of the molecule from the amino terminal end. No immunoreactivity was found in the sequence 135–191.
Preparation and properties of some crystalline symmetrical anhydrides of Nα‐tert.‐butyloxycarbonyl‐amino acids
Authors: YAMASHIRO DONALD
Published: August 2010

The preparation and properties of 16 crystalline symmetrical anhydrides of Nα‐tert.‐butyloxycarbonyl‐amino acids is described.
Synthesis, resolution and characterization of ring substituted phenylalanines and tryptophans
Authors: PORTER JOHN , DYKERT JOHN , RIVIER JEAN
Published: August 2010

Experimental protocols have been developed for the synthesis and resolution of numerous ring substituted phenylalanines and tryptophans in half mole quantities. Physical constants on these amino acids are given and their behavior on ion exchange supports (amino acid analyzer and post column ortho‐phthalaldehyde derivatization) as well as that of some selected N‐methylated amino acids is described. Those amino acids were then derivatized (Nα‐protection with the t‐butyloxycarbonyl group) for solid phase peptide synthesis.
Amino acids and peptides
Authors: TENO NAOKI , TSUBOI SATOSHI , OKADA YOSHIO , ITOH NORIO , OKAMOTO HIROSHI
Published: August 2010

The Gln‐Val‐Val‐Ala‐Gly sequence, which occurs frequently in several natural thiol proteinase inhibitors, and derivatives were synthesized by conventional solution methods and their effect on thiol proteinases were examined. The studies led us to the conclusion that certain of these peptides exhibited a weak inhibitory effect on the thiol proteinase, papain. One of them, Z‐Gln‐Val‐Val‐Ala‐Gly‐OMe, showed a protective effect on papain from natural thiol proteinase inhibitor‐induced inactivation. The relationship between structure and activity of these derivatives was studied and certain conclusions were derived on possible mode of action of these inhibitors. From these studies, it was concluded that Z‐Gln‐Val‐Val‐OMe was the smallest peptide to exhibit some effect on papain.