bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyclic peptides.
Authors: Mihara Hisakazu , Aoyagi Haruhiko , Lee Sannamu , Waki Michinori , Kato Tetsuo , Izumiya Nobuo
Published: August 2010

In order to investigate the influence of the side‐chain length at position 3 of AM‐toxin I (cyclic tetradepsipeptide) on necrotic activity for apple leaf, two analogs of AM‐toxin I, [L‐2‐amino‐4‐(p‐methoxyphenyl)butanoic acid3]‐AM‐toxin I and [L‐2‐amino‐6‐(p‐methoxyphenyl)hexanoic acid3]‐AM‐toxin I, were synthesized by the conventional method. Spectra of 1H‐n.m.r., u.v. and CD of the analogs were similar to those of natural or synthetic AM‐toxin I. The toxic activities of the analogs for apple leaf, however, were weak, indicating that the exact side‐chain length at position 3 must be one of the important factors for the induction of the activity. The interaction between AM‐toxin I and a possible receptor on apple leaf is discussed.
Isolation and identification of thymosin α‐1 from calf spleen using high performance liquid chromatography
Authors: DANHO WALEED , GABRIEL THOMAS F. , MAKOFSKE RAYMOND C.
Published: August 2010

A peptide isolated from calf spleen has been identified as thymosin α1. The isolation involved defatting of the desiccated glands with acetone, extraction of the acetone power with pyridine acetate pH 5.5, heat denaturation, reverse phase chromatography on an RP‐8 column, anion exchange chromatography on a Partisil SAX column and, finally, reverse phase purification on a μBondapak C18 column. The identification was based on: 1) amino acid analysis; 2) thermolysin digest; and 3) retention time in two different HPLC systems. The amount isolated from the spleen was 10–20% of that isolated from calf thymus glands.
Synthesis of Ac‐Asp‐Gly‐Ser and Ac‐Asp‐Pro‐Leu‐Gly‐NH2
Authors: HAGEN ERIK A. , LOENNECHEN THRINA , SYDNES LEIV K. , AASEN ARNE J.
Published: August 2010

The syntheses of Ac‐Asp‐Gly‐Ser and Ac‐Asp‐Pro‐Leu‐Gly‐NH2 are described. The two peptides were prepared in solution by stepwise elongation using the DCC method with additives (HOSu or HOBt). The push‐pull method was also used in the synthesis of Ac‐Asp‐Gly‐Ser. A racemization test of the amino acids in this peptide has been performed.
Unfolding of tertiary structures of proteins
Authors: WAKANA HIROMITSU , YOKOMIZO HIDEO , WAKO HIROSHI , ISOGAI YOSHINORI , KOSUGE KAZUHIKO , SAITÔ NOBUHIKO
Published: August 2010

The unfolding pathway of lysozyme was investigated by carrying out the computer simulation. Taking into account the simultaneous change of both the dihedral angles ø and of a residue, we explore the detailed features of the conformational energy profiles. The triangle distance map shows that the lysozyme molecule is divided into three domains, 1–40, 41–101 and 102–129 in amino acid residue numbers (referred to as the domains I, II and III, respectively). The calculated unfolding process indicates that in the early stage of unfolding domain III located at the C‐terminal begins to be detached from the other two, and then domain I can be unfolded. The long‐range interactions between domains I and III stabilize the whole molecule and give the cooperative nature of the folding. The calculated unfolding pathway of lysozyme is consistent with the folding pathway proposed by Anderson & Wetlaufer [J. Biol. Chem. (1976). 251, 3147–3153] who identified the disulfide bondings in the early stage of the glutathione regeneration. A simplified treatment of unfolding for myoglobin is also discussed in the Appendix.
Preparation and characterization of photoreactive derivatives of GnRH
Authors: NIKOLICS KAROLY , TEPLAN ISTVAN , RAMACHANDRAN J.
Published: August 2010

A photoreactive derivative of the highly potent gonadotropin releasing hormone (GnRH) agonist, D‐Lys6‐GnRH(1–9)‐ethylamide, was prepared by selective modification of the e‐amino group with 2‐nitro‐4‐azidophenyl sulfenyl chloride (2,4‐NAPS C1). The modified peptide [D‐Lys(NAPS)]6‐GnRH‐(1–9)‐ethylamide was found to be a full agonist of LH release from rat pituitary cells with a relative potency 23 compared to GnRH. Covalent attachment of the photoreactive analog to rat pituitary cells resulted in prolonged activation of LH secretion whch could not be inhibited by a potent GnRH antagonist. Persistent stimulation of pituitary gonadotrophs caused by covalently bound hormone led to desensitization of the LH releasing mechanism.
Conformational influences of N2‐methylation in chemotactic peptides
Authors: JEFFS PETER W. , HEADL SARAH L. , CHODOSH DANIEL F. , EGGLESTON DRAKE S.
Published: August 2010

Physical and structural data on two of a series of related N‐formyl methionine peptides are reported. The effects of peptide bond N‐methylation on chemotactic response and on conformational properties observed in solution, in the solid state and by conformational energy calculations are described.
Vibrational analysis of peptides, polypeptides and proteins
Authors: NAIK V.M. , KRIMM S. , DENTON J.B. , NÉMETHY G. , SCHERAGA H.A.
Published: August 2010

Normal mode calculations have been carried out on three low‐energy structures of gramicidin S obtained from conformational energy calculations. When the results on the amide modes are compared with observed bands in the infrared and Raman spectra of crystalline gramicidin S and its N‐deuterated derivative, one of the structures is clearly disfavored. Of the other two, one is slightly favored, and it corresponds to the lowest‐energy structure obtained from the energy calculations. Spectra from solutions in DMSO and CH3 OH suggest that the molecular conformation is essentially retained in these solvents.
Experimental and theoretical conformational studies on polypeptide models of collagen
Authors: TAMBURRO A.M. , GUANTIERI V. , CABROL D. , BROCH H. , VASILESCU D.
Published: August 2010

The synthetic polytripeptides poly(Gly‐Pro‐Ile) and poly(Gly‐Ile‐Pro) were studied both experimentally (mainly by circular dichroism spectroscopy) and theoretically by quantum mechanical methods. Poly(Gly‐Ile‐Pro) adopts a collagen‐like structure under favourable conditions while the isomeric poly(Gly‐Pro‐Ile) does not. Theoretical studies emphasize severe intrastrand interactions which limit the main chain conformations in the case of poly(Gly‐Ile‐Pro). On the other hand, both the side cahin and the backbone in poly(Gly‐Pro‐Ile) can take up many different local conformations. Therefore, it seems that the conformational behaviour of synthetic polytripeptides can be at least partially explained in terms of local interactions.
Purification of mammalian arylsulfatase A enzymes by subunit affinity chromatography
Authors: WAHEED ABDUL , VAN ETTEN ROBERT L.
Published: August 2010

Rabbit liver arylsulfatase A (arylsulfatase sulfohydrolase, EC 3.1.6.1) monomer was immobilized on cyanogen bromide‐activated Sepharose‐6MB and on Affi‐Gel‐10 under various experimental conditions in order to study the effects of variables in sulfatase monomer/oligomer subunit affinity chromatography. First, the number of reactive groups on activated Sepharose‐6MB and Affi‐Gel‐10 was determined by a procedure involving spectrophotometric titration with L‐tyrosine. After covalent coupling of sulfatase monomers to the gels, the enzyme binding capacities of the sulfatase subunit affinity gel matrixes were determined at pH 4.5. The maximum binding of free monomers from solution could be achieved when the Affi‐Gel‐10 protein monomer matrix was prepared at low degrees of covalent loading. The introduction of a batch technique for equilibration of the protein sample with the monomer affinity matrix also increased the efficiency of the subunit affinity gel in purification procedures. The effect of pH on the stability of the heterodimers formed between monomers of rabbit liver arylsulfatase A immobilized on Affi‐Gel‐10 and free monomers of arylsulfatase A enzymes from different tissues and organisms was studied using the batch technique. For all sulfatase A enzymes tested, the midpoint of the pH transition for subunit association was pH 6.2, suggesting that the amino acid residues involved in the dimerization are similar. The versatility of the Affi‐Gel‐10 monomer affinity matrix was further demonstrated by purifying 13 mammalian arylsulfatase A enzymes to homogeneity, as assessed by Sephacryl chromatography, native and SDS gel electrophoresis. The molecular weights of the homogeneous monomers and their peptide subunits were in the range of 110–180 KDa and 50–64 KDa, respectively. The amino acid compositions of these enzymes were also determined.
Kinetics of acetylation‐deacetylation of angiotensin II
Authors: MOORE GRAHAM J.
Published: August 2010

The possible existence of intramolecular interactions involving the tyrosine and histidine residues in angiotensin II has been investigated by measuring the reactivities of the functional groups in the molecule. Angiotensin II catalyzed the hydrolysis of p‐nitrophenylacetate in the pH range 6.6–8.2 at higher rates than were consistent with the reactivities of the free constituent functional groups, and had 2–4% of the activity of chymotrypsin between pH 6.6 and 7.5. Treatment of angiotensin II with acetic anhydride demonstrated that the tyrosine hydroxyl and the imidazole side‐chain in angiotensin II acetylated and deacetylated at markedly higher rates than for the free amino acids, indicating increased nucleophilicities and the presence of intrinsic deacetylation mechanisms for these residues in angiotensin II. These findings are consistent with the presence of tyrosine hydroxyl‐histidine‐carboxylate charge relay system in ANG II in aqueous environments, and suggest that ANG II may act at membrane receptors by a mechanism which is analogous to that operating in serine proteases.
Specificity of antisera obtained to Substance P and its C‐terminal hexapeptide
Authors: BABINSKA A. , CIERNIEWSKI C.S. , KOZIOLKIEWICZ W. , JANECKA A.
Published: August 2010

Synthetic fragments and analogs were used to characterize specificity of antisera toSP and SP6–11. [Tyr8]SP and [Lys6]SP6–11 were both used as radioiodinated ligands. The latter was conjugated with Bolton‐Hunter reagents before labelling. In both systems, the C‐terminal pentapeptide SP7–11 was the shortest fragment showing antigenic identity with Substance P molecule. Substitution of different amino acid residues in SP6–11 by His or Gly showed that all but Glu6 take part in the structure of the antigenic determinant.
Conformational analysis of cyclized dipeptide models for specific types of β‐bends by two‐dimensional nuclear Overhauser spectroscopy*
Authors: STIMSON E.R. , HUANG S.G. , NÉMETHY G. , LEACH S.J. , SCHERAGA H.A.
Published: August 2010

The solution conformations in DMSO‐d6 of the two cyclized dipeptides, cyclo(l‐alanyl‐l‐alanyl‐e‐aminocaproyl) and cyclo(l‐alanyl‐d‐alanyl‐e‐amino‐caproyl), have been analyzed by means of the two‐dimensional nuclear Overhauser effect (2D‐NOE). The preferred conformations for the two compounds have been deduced by comparing proton‐proton distances, derived from the 2D‐NOE data and relaxation‐time measurements, with the corresponding distances in several possible computed low‐energy conformations. The predominant conformations are a type III bend and a type II bend, respectively, for the two compounds. These conclusions agree with those deduced earlier on the basis of infrared and Raman spectra and circular dichroism measurements.
Cyclic peptides. XVIII. Syntheses of AM‐toxin I analogs containing bulky L‐amino acid residues instead of an L‐alanine*
Authors: AOYAGI HARUHIKO , MIHARA HISAKAZU , LEE SANNAMU , KATO TETSUO , UENO TAMIO , IZUMIYA NOBUO
Published: August 2010

In order to investigate the influence of the alanine residue at position 1 of AM‐toxin I (cyclic tetradepsipeptide) on necrotic activity for apple leaves, three analogs, [l‐2‐aminobutanoic acid1] AM‐toxin I, [l‐leucine1] AM‐toxin I and [l‐phenylalanine1] AM‐toxin I, were synthesized by the conventional method for peptide synthesis. Spectra of 1H‐n.m.r., u.v. and CD of the analogs were similar to those of natural AM‐toxin I. The analogs showed appreciable biological activity including host‐specificity, indicating that considerable variation in the size of side chain at position 1 is allowed for the induction of necrotic activity.
Preparation and properties of tritiated human [Tyr 18, Trp 27]‐β ‐endorphin
Authors: HAMMONDS R. GLENN , LI CHOH HAO
Published: August 2010

Tritiated [Tyr 18, Trp 27]‐βh‐EP was prepared from the corresponding diiodotyrosine derivative by catalytic reduction in the presence of carrier free tritium gas. A photoaffinity probe for β‐endorphin (β‐EP) receptors was prepared by selective modification of [Tyr18, Trp27]‐βh‐endorphin with 2‐nitro‐4‐azidophenylsulfenyl chloride (2,4‐NAPS‐Cl) under acidic conditions to yield [Trp18‐2,4‐NAPS‐Trp27]‐βh‐endorphin (NAPS‐β‐EP). NAPS‐β‐EP was purified by high performance liquid chromatography and characterized by ultraviolet absorption spectroscopy and peptide mapping. Tritiated NAPS‐β‐EP was prepared from tritiated [Tyr18, Trp27]‐βh‐endorphin with 2,4‐NAPS‐Cl. The ability of NAPS‐β‐EP to form covalent bonds to macromolecules due to photolysis was established using bovine serum albumin. The efficiency of photolytic cross‐linking was 15% and the equilibrium dissociation constant was 1.3 times 10‐5 M.
Complete amino acid sequence of fin whale growth hormone
Authors: TSUBOKAWA MAKOTO , KAWAUCHI HIROSHI
Published: August 2010

The complete amino acid sequence of growth hormone from fin whale pituitary has been determined. It consists of 190 amino acid residues with two disulfide bridges formed by residues 52–163 and 180–188. The sequence identity with sei whale, bovine, ovine and human growth hormone is 90%, 91%, 90% and 68%, respectively.
β‐Endorphin. Biological activity of synthetic analogs with analgesia inhibiting property in rat vas deferens and guinea pig ileum assays
Authors: HO CHEWN LANG , LI CHOH HAO
Published: August 2010

Three synthetic analogs of human β‐endorphin (βh‐EP) (I, [Gln8, Gly31]‐βh‐EP‐Gly‐Gly‐NH2; II, [Arg9,12,24,28,29]‐βh‐EP and III, [Cys11,26, Phe27, Gly31]‐βh‐EP), which have been shown to possess potent inhibiting activity to βh‐EP‐induced analgesia, were assayed in rat vas deferens and guinea pig ileum bioassay systems. In the rat vas deferens assay, relative potencies of these analogs were βh‐EP, 100; I, 30; II, 40; III, 1, whereas in the guinea pig ileum assay: βh‐EP, 100; I, 184; II, 81; III, 163. From previous studies on their analgesia potency in mice and opiate receptor‐binding activity in rat brain membranes, their activity in rat vas deferens correlates well with the analgesic potency and the activity from guinea pig ileum assay shows good correlations with that from the opiate receptor‐binding assay.
Spectroscopic study of the interaction of gossypol with bovine serum albumin
Authors: MALIWAL B.P. , RAO A.G. APPU , RAO M.S. NARASINGA
Published: August 2010

The interaction of gossypol with bovine serum albumin (BSA) at pH 7.6 in 0.02 M borax‐borate buffer has been followed by circular dichroism (CD) and difference spectroscopy. From the extrinsic CD band at 390 nm, a binding constant of 2.7 times 103M‐1was calculated. At 54° the induced CD spectrum was abolished, suggesting that the interaction is not favoured at that temperature. The effect of various solvents and salts on the interaction has been followed by difference spectroscopy. The modification of ∍‐amino groups of lysine did not affect the interaction. Binding of gossypol to BSA does not cause a change in its secondary structure or sedimentation coefficient.
Conformation and stability of the chymotrypsin inhibitor from winged bean seed (Psophocarpus tetragonolobus (L.) DC)
Authors: GRUEN L.C. , KORTT A.A.
Published: August 2010

Spectrophotometric measurement was found to be a sensitive method for evaluating the stability of the chymotrypsin inhibitor from the winged bean. The thermal stability of this protein in aqueous solution was much greater at pH 3 than at pH 8 or pH 11. Evidence from u.v. absorption and from circular dichroism indicated that irreversible conformation changes occurred at higher temperature (> 70°). Circular dichroism and optical rotatory dispersion studies at pH 8 show that the inhibitor is rich in β‐structure and virtually devoid of α‐helix in aqueous solution. We conclude from experiments with denaturing solvents that the inhibitor is very stable and that high concentrations of denaturant are required before unfolding occurs. Chemical modification experiments with tetranitromethane were consistent with a tight stable structure; even in 6 M guanidine hydrochloride only three of the five tyrosine residues in the inhibitor molecule were nitrated. However, tyrosine does not seem to be implicated at the reactive site of the inhibitor. Interaction of the inhibitor with α‐chymotrypsin and chymotrypsin B was also followed by difference spectroscopy in the ultraviolet region. Difference spectra were detected that were characteristic of changes in the environment of both tyrosine and tryptophan chromophores. Comparison of the spectral data obtained for the interaction of the inhibitor with bovine α‐chymotrypsin and with chymotrypsin B indicated that a tryptophan residue may be involved at the reactive site of the inhibitor. Spectral changes were also detected for the interaction between the chymotrypsin inhibitor and trypsin, although it is well established that the specificity of this inhibitor is restricted to the chymotrypsins. However the complex formed between the inhibitor and the chymotrypsins (verified to have a 1:2 inhibitor: enzyme stoichiometry) was found to be stable to at least 50°, whereas the weaker “non‐specific” interaction observed between the inhibitor and trypsin was largely destroyed on heating to 40°.
β‐Endorphin does not protect alkylation of opiate receptor byN‐ethylmaleimide
Authors: WESTPHAL MANFRED , HAMMONDS R. GLENN , FERRARA PASCUAL , LI CHOH HAO
Published: August 2010

Rat brain membranes were incubated inN‐ethylmaleimide (NEM, 0.5–1.0 mM) in the presence and absence of various concentrations of morphine, Leuenkephalin and human β‐endorphin (β‐EP). After sufficient washing, the binding of dihydromorphine (DHM), [d‐Ala‐d‐Leu]‐enkephalin (DADLE) and tritiated βh‐EP was 10–40% above that of membranes treated with NEM alone. There was no additive effect of morphine and Leu‐enkephalin with respect to their effect on recovery of βh‐EP binding. Evaluation of βh‐EP as protecting ligand proved to be difficult since preincubation completely inhibits subsequent DHM and DADLE binding unless a more extensive washing protocol is employed. A protocol for washing βh‐EP preincubated membranes using a Tris‐phosphate buffer of pH 6 containing 150 mM NaCl, 20 mM MgCl2and 10% glycerol was used to recover enough binding potential to evaluate the effects of βh‐EP preincubation towards NEM treatment. Preincubation with βh‐EP itself at 0.1–1.0μM did not result in any increased recovery of opiate binding, in contrast to the findings with the other two ligands.
Utilization of 1‐hydroxybenzotriazole in mixed anhydride coupling reactions
Authors: PRASAD KARI U. , IQBAL MOHAMMED A. , URRY DAN W.
Published: August 2010

The coupling of Boc‐Val‐OH to either H‐Pro‐OBzl or H‐Pro‐Gly‐Val‐Gly‐OBzl by the mixed anhydride method leads to the formation of a urethane by‐product in yields of 40–60%. This side reaction can be suppressed by the addition of HOBt to the reaction mixture before the amino component is added. This results in a substantially increased yield of the desired peptide.
Peptide N‐alkylamides by solid phase synthesis*
Authors: KORNREICH WAYNE , ANDERSON HARRY , PORTER JOHN , VALE WYLIE , RIVIER JEAN
Published: August 2010

Three new resins have been developed that allow for the solid phase synthesis of C‐terminal peptide N‐alkylamides using Boc amino acids, usual side chain protecting groups and hydrogen fluoride cleavage and deprotection. These resins were prepared by reacting the appropriate alkylamine (NH2 CH3, NH2 CH2 CH3, NH2 CH2 CF3) to Merrifield's 1% divinylbenzene cross‐linked chloromethylated polystyrene resin. The application of these resins to the synthesis of C‐terminal GnRH N‐alkylamides illustrates the versatility of this approach. GnRH analogs were tested for their ability to release LH from cultured rat anterior pituitary cells. [D Glu6, Pro9‐NHCH2 CH3]‐GnRH was synthesized for the first time using the solid phase approach and found to be three times more potent than [D Glu6]‐GnRH. Other analogs including [D Trp6, Pro9‐NHCH2 CH3]‐GnRH, [D Ala6, Pro9‐NHCH2 CF3]‐GnRH and related peptides were found to be equipotent and to have the same properties (HPLC retention times, amino acid analysis and specific rotation) as the corresponding peptides synthesized using less amenable strategies; yields were equivalent or better than those reported earlier.
Cyclic peptides.
Authors: UEDA TOSHIHISA , SADA ISAO , KATO TETSUO , IZUMIYA NOBUO
Published: August 2010

cyclo(‐l‐Pro‐l‐Val‐l‐Pro‐l‐Val‐) (1L) and cyclo(‐l‐Pro‐d‐Val‐l‐Pro‐d‐Val‐) (1D) were synthesized by the conventional method for peptide synthesis. Conformations of 1L and 1D in solution were studied. Compound 1L has a cis‐trans‐cis‐trans backbone conformation with C2 symmetry in CDCl3. This conformation is slightly different from that in crystalline state and in DMSO‐d6 solution. Compound ID has a cis‐trans‐cis‐trans conformation in DMSO‐d6 and an all‐trans conformation in trifluoroethanol‐d3. Compound 1L retarded stem‐growth of rice seedlings and, in contrast, compound 1D promoted root‐growth of rice seedlings.
Preferential cleavage at aspartyl‐prolyl peptide bonds in dilute acid*
Authors: MARCUS FRANK
Published: August 2010

A simple, rapid technique is presented for preferential cleavage at aspartyl‐prolyl peptide bonds. The method is based upon the fact that these peptide bonds are 8–20‐fold more labile in 0.015 n HCl at 100–110° than other aspartyl‐X or X‐aspartyl peptide bonds. The method has proven effective in the cleavage of several peptides from pig kidney fructose‐1,6‐bisphosphatase and should facilitate sequence analysis of proteins that contain aspartyl‐prolyl linkages.
Vasopressin analogs with high and specific antidiuretic activity
Authors: ZAORAL MILAN
Published: August 2010

A systematic approach to structure‐activity studies is described. Its application to the vasopressin field made possible the preparation of vasopressin analogs with very high and very specific antidiuretic activity, analogs with increased pressor specificity, and analogs with high agonistic‐antagonistic properties.
Hexapeptide analogue of somatostatin, Sandoz 201–456.
Authors: WYNANTS C. , van BINST G. , LOOSLI H.R.
Published: August 2010

The conformational properties of the somatostatin analogue 201–456 (1) have been studied by high field n.m.r. in DMSO. This analogue is the base structure of nine derivates synthesized by Bauer et al. and shows a very low biological activity, although derived structures such as SMS 201–995 (2) are very potent. Our study has shown an important difference between the most stable conformation of the two compounds: although the β turn type II' structure at the Phe3‐Trp4‐Lys5level is present in both analogues, an important conformational change appears at the cystine bridge. In SMS 201–995 the β turn/β sheet conformation is stabilized by the additional amino‐acids d‐Phe1and Thr8(ol) through intramolecular H‐bonds.
Synthesis of analogs of K‐582A, an antibiotic heptapeptide
Authors: MIHARA HISAKAZU , AOYAGI HARUHIKO , YONEZAWA HIROO , KUROMIZU KENJI , IZUMIYA NOBUO
Published: August 2010

K‐582 A, an antibiotic heptapeptide, has a sequence of H‐l‐Arg‐l‐Arg(OH)‐d‐Orn‐l‐Thr‐d‐Orn‐l‐Lys‐d‐Tyr‐OH (Arg(OH), threo‐γ‐hydroxyarginine). In order to investigate the relationship between structure and antimicrobial activity, four shortened analogs, des‐l‐Arg1,l‐Arg(OH)2‐K582 A (pentapeptide), des‐l‐Arg(OH)2‐K‐582 A (hexapeptide) and their N‐acetyl derivatives, were synthesized by the conventional method. None of them, however, showed any antimicrobial activity. Three more analogs, [l‐Lys2]K‐582 A, [l‐Orn2]K‐582 A and [l‐Arg2]K‐582 A, were synthesized. Among them, only [l‐Arg2]K‐582 A showed substantial activity against Candida krusei and Saccharomyces rouxii, indicating that the presence of a guanidyl side chain at position 2 is an essential factor for the induction of activity.
Stability of 11S globulin from Vicia faba seeds
Authors: DANILENKO ANATOLI N. , ROGOVA ELENA I. , BIKBOV TAKHIR M. , GRINBERG VALERI YA. , TOLSTOGUZOV VLADIMIR B.
Published: August 2010

Heat denaturation of 11S globulin, a dodecameric globular protein isolated from Vicia faba seeds was studied using scanning microcalorimetry at pH 7.6 and NaCl concentrations from 0 to 1 M. The specific enthalpy of denaturation was shown to be a linear function of temperature. The ratio of the calorimetric enthalpy to the effective one (Van't‐Hoff's) per protomer of 11 S globulin was 0.9 ± 0.06. It is concluded that at first approximation 11 S globulin protomers denaturated independently in conformity with the two‐state model. The plotted temperature‐dependent specific free energy of 11 S globulin denaturation at different NaCl concentrations demonstrated that an increase in the salt content brought about the rise in protein stability. The maximum 11 S globulin stability is reached at about 300°K. The molar free energy of denaturation at 300°K in 1 M NaCl is 918 kJ/mol.
Calcium and praseodymium complexes in solution
Authors: ASSO MARCEL , GRANIER CLAUDE , VAN RIETSCHOTEN JURPHAAS , BENLIAN DAVID
Published: August 2010

The synthetic tetrapeptide acetyl‐aspartyl‐valyl‐aspartyl‐alanine (Ac‐DVDA) is a model of the calcium binding site of proteins such as carp parvalbumin, thermolysin and calmodulin. 1H n.m.r. spectra of the tetrapeptide are presented and assigned for D2O and DMSO solutions to determine the conformational mobility. The resonance of the two aspartyl side chains could be completely analysed and the vicinal coupling (CαH‐CβH and NH‐CαH) indicated that the free peptide has considerable conformational mobility. The Ca(II) complex generates a different 1H n.m.r. spectrum for the aspartyl resonances at neutral pH. The solution conformation of Pr(III) complex of Ac‐DVDA has been investigated using induced chemical shifts. The observed trends in the magnitude of the shift ratios and the rotamer population suggest that the metal ion binds predominantly to both carboxylates of two aspartyl residues in a bidentate fashion. We discuss the consistency of the differentiated spectra for aspartyl residues in the complex with the stepwise binding of Ca2+ to the carrier.
Sodium dodecyl sulfate‐bovine plasma albumin complex
Authors: ERA SEIICHI , NAGAOKA SHUNJI , SOGAMI MASARU , WATARI HIROSHI , AKASAKA KAZUYUKI
Published: August 2010

The acid‐induced isomerization (the N‐F transition) and expansion of sodium dodecyl sulfate‐bovine plasma albumin complex (ADm;m, molar ratio of added sodium dodecyl sulfate to bovine plasma albumin; 0 ± m ± 12) were studied by measuring CD‐resolved secondary structure, fluorescence polarization and lifetime of tryptophyl fluorophors, acid‐titration with the electrostatic correction for the surface potential, 1H‐n.m.r. spectra and cross relaxation time between irradiated and observed protons. The immobilization of tryptophyl fluorophors observed in the F‐form of AD0 was suppressed in the F‐form of AD10. The acid‐titration analysis of AD12 showed non salt‐bonding between carboxylate groups and cationic side chains in the F‐form, as in the case of AD0, indicating charged side chains being presumably mobile. 1H‐n.m.r. spectra and cross relaxation times between irradiated and observed protons in the F‐form of AD10 indicated the increase in the local motion. On the other hand, AD10 and AD12 did not show any significant change in the CD‐resolved secondary structure in the N‐F transition region. The F‐form of AD10 or AD12 may therefore be the molten‐globule state which has secondary structure similar to the N‐form of the complexes with fluctuating tertiary structure (side chains).
Improved approach for anchoring Nα‐9‐fluorenylmethyloxycarbonylamino acids as p‐alkoxybenzyl esters in solid‐phase peptide synthesis
Authors: ALBERICIO FERNANDO , BARANY GEORGE
Published: August 2010

Several Fmoc‐amino acids have been esterified by use of N,N‐dimethylformamide dineopentyl acetal (2) to 2,4,5‐trichlorophenyl 3‘‐(4“‐hydroxymethyl‐phenoxy)propionate (7), and the resultant handle derivatives (5) were purified and then quantitatively coupled onto aminomethyl supports. Compared to literature methodology, the present procedure is preferred because: (i) extra steps to selectively protect and liberate the carboxyl of the handle are circumvented; and (ii) the additional methylene group spacer reflecting substitution of a propionyl group for an acetyl group in the handle changes the electronic parameters of the resultant p‐alkoxybenzyl ester sufficiently so that the rates of acidolytic cleavage of the anchoring linkage are 2‐ to 3‐fold increased and useful improvements in yields can be achieved.
Selective labelling of apolipoproteins A–I and C–I at methionine residues by (3H) methyl exchange
Authors: HANCOCK W.S. , HARDING D.R.K. , BARLING P.M. , SPARROW J.T.
Published: August 2010

Apolipoproteins C–I and A–I were radioactively labelled with tritium by (3H)‐methyl exchange. The methionine residues were first methylated with (3H)‐methyl iodide at pH4 and the reaction products were purified by gel filtration and cation exchange chromatography. The products were then demethylated with 2‐mercaptoethanol (6M) at pH 8.6 to regenerate the apolipoproteins in an unmodified but tritiated form. The specific radioactivity for apolipoprotein C–I and A–I was 3.5 times 106 and 1.5 times 107 dpm/pmol respectively. The properties of (3H)‐apolipoprotein C–I were examined by reversed phase HPLC and by incorporation into very low density lipoproteins (VLDL).
Distinct behavior of β‐endorphin and corticotropin toward leucine aminopeptidase action
Authors: LI CHOH HAO , CHUNG DAVID
Published: August 2010

Reactions of human β‐endorphin, corticotropin and their synthetic analogs with leucine aminopeptidase have been investigated. The results confirmed previous findings that β‐endorphin is resistant to the aminopeptidase action whereas corticotropin is not. β‐endorphin‐(1–5) is completely digested by the enzyme while β‐endorphin‐(1–17) is resistant. In contrast, the NH2‐terminal 7 residues in corticotropin are removed readily by leucine aminopeptidase. This is confirmed by the observation that human corticotropin‐(7–38) is not hydrolyzed by the enzyme. This contrasting behavior of the two hormones toward leucine aminopeptidase may be related to differences in their conformational structures.
Studies on peptides
Authors: FUJII NOBUTAKA , HAYASHI YOSHIO , KATAKURA SHINICHI , AKAJI KENICHI , YAJIMA HARUAKI , INOUYE ATSUKO , SEGAWA TOMIRO
Published: August 2010

A decapeptide corresponding to the entire amino acid sequence of neurokinin A, a porcine spinal cord peptide, was synthesized in a conventional manner using protecting groups removable by 1 M TFMSA‐thioanisole in TFA. The HS‐CH2CH2CO group was introduced onto the synthetic neurokinin A by reaction of 3‐(S‐acetyl‐thiopropionyl)‐thiazolidine‐2‐thione, followed by deacetylation with hydroxylamine. 2,4‐Dinitrophenyl‐p‐(β‐nitrovinyl)‐benzoate trapped the above HS‐CH2CH2CO‐neurokinin A derivative in acidic media, then BSA in basic media in nearly quantitative yield. A similar decapeptide, neurokinin B, was also synthesized and conjugated onto BSA using an alternative SH‐introducing reagent, 3‐(S‐p‐methoxybenzyl‐thiopropionyl)‐thiazolidine‐2‐thione, and the above heterobifunctional conjugating reagent.
Vibrational analysis of peptides, polypeptides, and proteins
Authors: BANDEKAR JAGDEESH , KRIMM S.
Published: August 2010

The normal modes of cyclo(D‐Phe‐L‐Pro‐Gly‐D‐Ala‐L‐Pro), a cyclic pentapeptide known to contain a Λ‐turn, have been calculated, and the amide I, II, III, and V modes have been compared with observed Raman and infrared bands. The observed bands are well predicted by the calculation. This gives confidence in the reliability of the calculations of the normal modes of standard Λ‐turn structures.
A helical peptide containing a majority of valyl residues
Authors: FRANCIS A.K. , VIJAYAKUMAR E.K.S. , BALARAM P. , VIJAYAN M.
Published: August 2010

The monohydrate of the heptapeptide t‐butyloxycarbonyl‐(L‐valyl‐α‐aminoiso‐butyryl)3‐L‐valyl methyl ester crystallizes in the orthorhombic space group P212121 with four molecules in a unit cell with the dimensions α= 9.375, b = 19.413 and c = 25.878 ÅA. The structure has been solved by direct methods and refined to an R value of 0.059 for 3633 observed reflections. The molecule in the structure exists as a slightly distorted 310‐helix stabilized by five 4 ‐> 1 intramolecular hydrogen bonds, indicating the overwhelming influence of α‐aminoisobutyryl (Aib) residues in dictating helical fold even when a majority of residues in the peptide have a low intrinsic propensity to be in helices. Contrary to what is expected in helical structures, the valyl side chains, two of which are disordered, exhibit all three possible conformations. The molecules arrange themselves in a head‐to‐tail fashion along the c‐axis. The columns thus generated pack nearly hexagonally in the crystal.
Studies of repeating synthetic peptides designed to adopt a cross‐β conformation
Authors: CARBONE F.R. , LEACH S.J.
Published: August 2010

Three polypeptides with the sequence poly(Gly‐Gln‐[Val‐Val]n‐Asn‐Pro) have been synthesised with n = 0, 1 or 2. The polyoctapeptide sequence is designed as a model for cross‐β structures, in particular those described for the microcrystalline parts of certain feather keratins (Fraser & MacRae (1976) Proc. 16th Int. Ornithol. Congress, Canberra, 1974). The circular dichroism (CD) spectra of all three polypeptides in trifluoroethanol are similar to those of the corresponding monomeric tetra‐, hexa‐ and octapeptides, with double minima near 205 and 220 nm and maxima near 193 nm. Accordingly, these polypeptides are believed to adopt repeating type I(III) β‐bends stabilised by H‐bonds involving Asn side chains. The difference CD spectrum produced by subtracting the spectrum for poly(GlyGlnAsnPro) from that of poly(GlyGlnVal4AsnPro) is typical of that for a β‐sheet, suggesting that the Val residues adopt a β‐strand conformation. Aqueous solutions of the polyhexapeptide can be induced to take up similar CD spectra on heating, presumably due to induced hydrophobic interactions between the Val β‐strands. X‐ray diffraction patterns on unoriented films of the polypeptides add weight to the conclusion that the polyoctapeptide folds up into a cross‐β structure with an inter‐strand spacing of 4.6 Å, a strand length of 23 Å and an inter‐sheet distance of 9.4 Å.
Solid phase synthesis of gastrin I
Authors: TAM JAMES P. , MERRIFIELD R.B.
Published: August 2010

A successful synthesis of human gastrin I in 60% overall yield based on the first residue attached to a benzhydrylamine‐resin was achieved by the stepwise solid‐phase method. The synthesis was carried out on a 1% crosslinked polystyrene support, using conventional benzyl‐based side chain protecting groups and final deprotection with different acidic protocols. Several improvements in this general approach were applied, including new scavengers, new resin attachment and especially a new technique that allows the strong acid reactions to occur by an SN2 mechanism.
Head‐to‐tail sequences and other patterns of peptide aggregation in the solid state
Authors: SURESH C.G. , VIJAYAN M.
Published: August 2010

Encouraged by the results of our earlier study on the occurrence and the geometrical features of head‐to‐tail sequences involving amino acids, which have been suggested to be of probable relevance to prebiotic polymerisation, the available crystal structures of unprotected peptides have been analysed with a view to investigating head‐to‐tail sequences and other patterns of peptide aggregation in the solid state. The number of available dipeptide structures is large enough to permit meaningful conclusions. The dipeptide molecules in the crystal structures can be broadly classified as extended or folded depending upon their conformations. The basic elements of dipeptide aggregation are different types of head‐to‐tail sequences and sequences involving hydrogen bonds with the peptide nitrogen atom as the donor, generated by periodic translations and 21screw axes. Using these basic elements and the known geometrical preferences of hydrogen bonds, it is possible to construct several plausible idealized patterns, mostly two‐dimensional, of dipeptide aggregation for extended as well as folded molecules. The patterns observed in crystal structures are in substantial agreement with these idealized patterns. Infinite hydrogen‐bonded sequences of the type observed in dipeptide structures remain the basic elements of aggregation in the structures of higher peptides also. The present analysis shows that peptide aggregation in the solid state is controlled primarily by interactions involving main chain atoms. Also, despite the increased molecular flexibility of peptides in comparison with amino acids and the presence of additional hydrogen bonding groups in them, head‐to‐tail sequences remain the most important intrinsic feature not only of amino acid aggregation but of peptide aggregation as well.
Possible role of water on the structural stability of ribosomes
Authors: DAMODARAN SRINIVASAN
Published: August 2010

Exposure of yeast 80 S ribosomes to low concentrations of NaClO4 caused complete dissociation of the ribosome. At higher ribosome concentrations the dissociated ribosomal proteins aggregated via hydrophobic interactions. Temperature exhibited very little effect on the NaClO4 induced dissociation of the ribosome, suggesting that the enthalpy change is nearly zero and the dissociation process is predominantly entropy driven. The origin of this entropy and the mechanism of dissociation of the ribosome by NaClO4 is discussed. Based on the observations it is proposed that the structural stability of the ribosome is probably maintained by the structure of the liquid water surrounding the ribosome.
Homo‐oligohistidines
Authors: RAJASEKHARAN K.N. , JONES J.H. , BONORA G.M. , TONIOLO C.
Published: August 2010

A series ofN(α)‐t‐butoxycarbonyl,N(®)‐benzyloxymethyl‐homo‐oligo‐L‐histidine methyl esters, ranging from the dipeptide to the heptapeptide, has been prepared, using the standard operations of conventional peptide synthesis starting from the corresponding monomer. The monodisperse homo‐oligopeptides were obtained in a pure state and fully characterised. Polarimetric measurements in a structure‐disrupting solvent confirmed that all the synthetic stages had proceeded with the preservation of chiral integrity, as expected from the methodology employed. Conformational investigations carried out by infrared absorption indicated that the highest oligomers adopt an intermolecularly hydrogen‐bonded β‐structure in the solid state.
Comparison and optimization of synthetic methods for preparing cholecystokinin peptides
Authors: TÓTH GÁBOR K. , PENKE BOTOND , ZARÁNDI MÁRTA , KOVÁCS KÁLMÁN
Published: August 2010

Cholecystokinin‐octapeptide sulphate ester was synthesized by four different strategies in the liquid phase. Both sulphation of the non‐sulphated octapeptide and the introduction of tyrosine‐O‐sulphate into the peptide molecule were attempted. For sulphation, three different reagents were applied: the classical pyridine‐SO3H complex, DCC‐H2SO4 and a new sulphating agent, pyridinium‐acetylsulphate. Although all these methods proved suitable for preparing cholecystokinin‐octapeptide of full biological activity, the mixed anhydride of sulphuric acid‐acetic acid seemed to be the best reagent for sulphation, causing minimal side‐reactions. The sensitive amino acids (methionine, tryptophan) could be protected from oxidation and tert.‐butylation during the deprotection step by using a new scavenger mixture containing water, thioglycolic acid and dithiothreitol. Both classical liquid chromatography on silica gel and reverse‐phase high‐performance liquid chromatography were suitable for isolation of pure cholecystokinin‐octapeptide.
Isolation of the C‐terminal fragment of proteins after re‐digestion of their esterified tryptic hydrolysates
Authors: DIBÓ GÁBOR , FURKA ÁRPÁD , SEBESTYÉN FERENC , FEHÉRVÁRI ÁGOTA
Published: August 2010

The key steps of the method proposed for isolating the C‐terminal fragment of proteins from their tryptic hydrolysates are the esterification of the digest with methanolic HC1 and redigestion with trypsin. The C‐‐terminal peptide is identified by preparing a peptide map using pH 2.1 buffer in the first, and pH 5.5 buffer in the second dimension. The C‐terminal fragment appears as an on‐diagonal spot. It can be isolated by a pH 5.5 run of the corresponding zone from the first (pH 2.1) electrophoretogram. Yields are up to 45% from different test proteins of known sequences.
Synthesis of L‐2‐amino‐4‐hexynoic acid and derivatives
Authors: SASAKI N. ANDRÉ , MORGAT JEAN‐LOUIS , POTIER PIERRE
Published: August 2010

A synthesis is described of optically pure L‐2‐amino‐4‐hexynoic acid and its derivatives, which can serve as potentially useful precursors for the preparation of highly tritium labeled norleucine‐containing peptides, as well as other side‐chain modified peptides. Catalytic tritiation of one derivative of this acetylenic amino acid afforded the (3H)‐L‐norleucine derivative with a specific activity of 115 ± 5 Ci/mmol.
β‐Endorphin‐(1–27) inhibits the spinal beta‐endorphin‐induced release of Met‐enkephalin
Authors: TSENG LIANG‐FU , LI CHOH‐HAO
Published: August 2010

The effect of intraventricular β‐endorphin‐(1–27) on the spinal release of Met‐enkephalin induced by intraventricular β‐endorphin was studied using the intrathecal superfusion technique in urethane anesthetized rats. Intraventricular injection of β‐endorphin at a dose of 15 μg released Met‐enkephalin from the spinal cord. This release of Met‐enkephalin induced by β‐endorphin was significantly reduced by β‐endorphin‐(1–27), 60 μg, injected intraventricularly. Injection of β‐endorphin (1–27) itself did not cause any release of Met‐enkephalin. The finding is in line with the previous report that β‐endorphin (1–27) inhibited the analgesia induced by β‐endorphin.
Membrane‐associated proteins of adriamycin sensitive and resistant murine leukemic P388 cells
Authors: SHANBAKY NABILA M. , SAMY T.S. ANANTHA , RUBIN ROBERT , KRISHAN AWTAR
Published: August 2010

We have isolated an 84‐fold adriamycin resistant subline, P388/R84, from mouse leukemia P388 cells by serial cultivation in methylcellulose in the presence of increasing drug concentrations. Electrophoresis of detergent soluble fractions of radiolabeled sensitive and resistant cells suggested marked alterations in the protein fractions of 160, 100, 60, 45, and 30 kd. In resistant clones labeled with 1251 an increase in 160 and 100 kd proteins was accompanied by concomitant reduction in the 60, 45, and 30 kd proteins. In 35S methionine‐labeled resistant cells, similar increases in the 160 and 100 kd components were observed but in contrast to 125I‐labeled cells the 30 kd component was also higher. Alterations in surface proteins were confirmed in experiments where the cell extracts were adsorbed to concanavalin A polymers and extracted with 0.26 M methyl‐α‐D‐mannopyranoside. Our data confirm earlier reported observations on cell‐surface protein changes in cells resistant to anthracyclines and alkaloids.
Conformational study of thyrotrophin‐releasing hormone
Authors: WARD D.J. , GRIFFITHS E.C. , ROBSON B.
Published: August 2010

The solution conformations of thyrotrophin‐releasing hormone (TRH), a biologically‐active tripeptide, have been predicted computationally using a method which represents solution effects as a dielectric continuum surrounding the molecule throughout energy minimisation; this is described as the reaction field contribution. The predicted conformations have been compared with previous experimental and theoretical studies. Favoured conformations of TRH under other simulated conditions have also been examined, including the behaviour of thecisisomer, and have been related to possible interactions with intermediates and with specific receptors. The relevance of these predictions to the design of biologically‐active analogues of TRH has been analysed.
Denaturation of glycinin by urea and guanidine hydrochloride
Authors: SURESHCHANDRA B.R. , RAO A.G. APPU , RAO M.S. NARASINGA
Published: August 2010

Denaturation of glycinin by urea and guanidine hydrochloride (GdnHC1) has been studied at 30° by viscosity and circular dichroism (CD) measurements. The kinetics of denaturation by 8M urea at 20, 30, 40 and 50°, and by 6M GdnHC1 at 20° have been measured by monitoring the increase in absorbance at 287 nm as a function of time. Viscosity increased with denaturant concentration and reached maximum value of 28 mL/g at 6M GdnHC1 and 7M urea. The (negative) molar ellipticity values in the region 250–200 nm decreased with increase in denaturant concentration. Analysis of viscosity and CD data indicated that both sets of data fitted the same curve of fd (fraction of protein denatured) versus denaturant concentration. The kinetic data followed first order reaction kinetics, These suggest that denaturation of glycinin by urea/GdnHC1 is a two‐state process and follows the same pattern as that of globular proteins.
Conformational studies on gastrin related peptides by high resolution 1H‐n.m.r.
Authors: MAMMI S. , GOODMAN M. , PEGGION E. , FOFFANI M.T. , MORODER L. , WUENSCH E.
Published: August 2010

The secondary structures of three gastrin analogs, HCl · H‐Trp‐Nle‐Asp(O‐tBu)‐Phe‐NH2 (tetragastrin), pGlu‐Ala‐Tyr‐Gly‐Trp‐Nle‐Asp‐Phe‐NH2 (octagastrin), and H‐Leu‐(Glu)5‐Ala‐Tyr‐Gly‐Trp‐Nle‐Asp‐Phe‐NH2 (minigastrin) were studied by 1H‐n.m.r. in dimethylsulfoxide and in trifluoroethanol. All three compounds were found to assume a random conformation in the former solvent, while some ordered secondary structure is present in trifluoroethanol even at the tetra‐peptide level. This was shown by temperature studies and solvent titrations. At least four amide protons were found to be solvent shielded in the longer hormone.
Nuclear magnetic resonance studies of linear, cyclic and polymeric peptides containing His, Ser and Asp residues spaced by ß alanylglycine
Authors: TSUTSUMI AKIHIRO , NAKAJIMA BUN‐ICHIRO , NISHI NORIO
Published: August 2010

1H and 13C nuclear magnetic resonance studies have been carried out on the linear, cyclic and polymeric peptides having a sequence of ‐Asp‐ßAla‐Gly‐Ser‐ßAla‐Gly‐His‐ßAla‐Gly‐. From the 1 H spectra measured at 400 MHz, the rotamer populations about side chain Cα‐Cß bond for Asp, Ser and His residues were estimated at pD 5 and 8. For Asp and Ser residues, the rotamers T (trans), G and G' (gauche) had an equivalent population at both pDs, while for His residue the rotamer G' had a higher probability than the others. 13C chemical shift of His and Asp residues measured at a frequency 15 MHz showed a considerable change in the pD ranges 3 ˜ 5 and 5 ˜ 8, respectively, owing to the ionizable side chains. The pK value for His residue, i.e. the midpoint of the chemical shift change, corresponded fairly well to that obtained from ester hydrolytic activity measurements, supporting the previous suggestion that the ester hydrolytic reaction is mainly controlled with the imidazole group of His residue. 13C spin‐lattice relaxation time T1 was measured in order to investigate the molecular motion. It was found that the backbone was composed of relatively movable parts, ‐ßAla‐Gly‐, and less movable parts, Asp‐ Ser and His. Thisphenomenon was especially remarkable at the higher pD. The internal motion in the side chain was also investigated using the relaxation theory for the molecules undergoing the internal rotation. These results of relaxation measurements were compared with the results of conformational studies by circular dichroism measurements. The polymeric peptide composed only of ‐His‐ßAla‐Gly‐ sequence was also measured as a related peptide.