bluuebunny/crossref_metadata_2025 huggingface dataset:
SYNTHESIS OF PROTECTED SECRETIN16–27 ON A MERRIFIELD RESIN
Authors: WRIGH DAVID E. , AGARWAL NIRANKAR S. , HRUBY VICTOR J.
Published: August 2010

The partially protected dodecapeptide to secretin, H ‐ Ser(Bzl) ‐ Ala ‐ Arg(Tos) ‐ Leu ‐ Gln ‐ Arg(Tos) ‐ Leu ‐ Leu ‐ Gln ‐ Gly ‐ Leu ‐ Val ‐ NH2 (protected secretin16–27) was prepared using a standard Merrifield resin and solid phase synthesis methods. For comparative purposes the unprotected peptide also was prepared on a benzhydrylamine resin. Contrary to previous reports, the valine C‐terminal peptide can be cleaved from the resin and the amide obtained in high yield. A variety of conditions were examined to accomplish the cleavage of the peptide from the resin in its carboxamide terminal form. The best conditions found were transesterification followed by ammonolysis in a mixed solvent system. A thin‐layer chromatography system which clearly separates the methyl ester and carboxamide terminal secretin16–27 was developed.
NONFUNCTIONAL NATURE OF SULFHYDRYL GROUPS FOR PIGEON LIVER MALIC ENZYME
Authors: CHANG GU‐GANG , CHUEH SHEAU‐HUEI
Published: August 2010

The cyanylated derivative of pigeon liver malic enzyme (EC 1.1.1.40) may be prepared by reacting the sulfhydryl groups of the enzyme with 2‐nitro‐5‐thiocyanobenzoic acid in the presence of excess KCN or by replacing the thionitrobenzoate moiety of the thionitrobenzoated enzyme with CN group. The ‐SCN derivative thus prepared is enzymatically active and is resistant to react with the affinity label bromopyruvate. In the generation of ‐SCN enzyme from the thionitrobenzoated enzyme, there is a correlation between the [14C] CN incorporation and the activity recovered. The sulfhydryl groups are thus not directly involved in the catalytic mechanism of the malic enzyme. Evidence is also provided to show that the SH groups were not involved in the binding of nucleotide coenzyme.
STRUCTURAL STUDIES ON STEM BROMELAIN
Authors: GOTO KASHIKO , TAKAHASHI NORIKO , MURACHI TAKASHI
Published: August 2010

Stem bromelain was cleaved with cyanogen bromide, and the products were fractionated with and without prior maleylation and sulfitolysis. The fragments that corresponded to the carboxyl‐terminal half of the molecule were isolated and nearly completely sequenced. This portion of the enzyme molecule contained one disulfide linkage. A specific cleavage at the amino peptide bonds of that cystine residue by reduction, modification into S‐cyano derivatives and exposure to alkali gave important information of the amino terminal sequence. By combining the present data with the previously known partial sequence of the parent molecule, 101 amino acid residues were aligned down to the carboxyl terminus and compared with those of papain. The sequence homology between carboxyl‐terminal halves of these two thiol proteases of plant origin was found to be 34.7%.
SYNTHESIS OF SOMATOSTATIN AND [D‐TRP8]‐ SOMATOSTATIN
Authors: FELIX ARTHUR M. , JIMENEZ MANUEL H. , WANG CHING‐TSO , MEIENHOFER JOHANNES
Published: August 2010

Experimental details for practical syntheses of somatostatin and D‐Trp8‐somatostatin are described. The peptides were assembled from three fragments which permit further syntheses of analogs with modifications at positions 1, 2 or 8. Nα‐Bpoc protecting groups were used for the two major fragments and these were selectively removed in the presence of the tert‐butyl derived amino acid side chain functionalities. The two cysteine residues were protected by acetamidomethyl groups. All the peptide intermediates were fully characterized and a 10‐g synthesis of the protected tetradecapeptide is reported. Major fragments were coupled by the azide method in good yield. Dihydrosomatostatin and D‐Trp8‐dihydrosomatostatin were isolated, purified, characterized and cyclized. Polymeric side‐product was successfully recycled (by reduction with dithiothreitol and reoxidation) to give an overall yield for the oxidation of 52%. Somatostatin and D‐Trp8‐somatostatin were purified by gel filtration or countercurrent distribution and the final products were fully characterized and determined to be>97% pure by reversed phase high performance liquid chromatography.
CARBON‐13 N.M.R. STUDY OF BLEOMYCIN‐A2 PROTONATION
Authors: MOOBERRY ED. S. , DALLAS JERRY L. , SAKAI TED T. , GLICKSON JERRY D.
Published: August 2010

The acid‐base titration of bleomycin‐A2 in D2O solution at 35 ± 5° has been monitored by 13C n.m.r. spectroscopy at 67.89 MHz. The following pKDa values were obtained: 3.68 ± 0.05 (secondary amine), 5.29 ± 0.03 (imidazole), and 8.23 ± 0.19 (primary amine), where KDa is the dissociation constant in D2O solution. The equilibrium isotope effects (pKDa ‐pKa in H2O) are: 0.70 ± 0.06 (secondary amine), 0.28 ± 0.04 (imidazole), and 0.85 ± 0.19 (primary amine). Titration of the imidazole group of Bleo‐A2 occurs at Nπ, i.e. only Nπ is protonated in basic solution. Significant protonation shifts are almost completely limited to carbons of the N‐terminal tetrapeptide, suggesting that the C‐terminal tripeptide extends into the solvent and interacts to a minimal extent with the rest of the molecule. Long range protonation shifts associated with titration of the imidazole and secondary amine groups indicate that protonation of one or both of these sites is probably accompanied by significant conformational changes. The observed protonation shifts generally fail to correlate with Zn(II) complexation shifts reported by Dabrowiak et al. (1973, Biochemistry 17, 4090) indicating that ligation sites cannot unambiguously be determined from these complexation shifts. The complexation shifts previously attributed to coordination of the imidazole and carbamoyl groups probably result from conformational changes.
THERMITASE, A THERMOSTABLE SERINE PROTEASE FROM THERMOACTINOMYCES VULGARIS
Authors: HAUSDORF G. , KRÜGER K. , HÖHNE W.E.
Published: August 2010

Studies on the amino acid composition, chemical modifications, and characterization of the cyanogen bromide cleavage peptides of a thermostable serine protase (thermitase) from Thermoactinomyces vulgaris were performed. The amino acid analysis shows that the enzyme contains a single cysteine and methionine residue. From the amino acid composition as well as a partial sequence determination around the single methionine residue it is concluded that thermitase belongs to the subtilisin‐type proteases. The two peptides obtained by cyanogen bromide cleavage were further characterized by amino acid analysis and molecular weight determination yielding 25 000 and 6 000 daltons, respectively. Chemical modification experiments show that in addition to the active site serine and histidine residue the cysteine as well as the methionine residue are essential for activity of the enzyme. The alignment of these amino acids in the polypeptide chain of the thermitase is supposed.
FLUORESCENCE PROPERTIES OF NEUTRAL PROTEASE FROM BACILLUS SUBTILIS
Authors: GRANDI CLAUDIO , DALZOPPO DANIELE , VITA CLAUDIO , FONTANA ANGELO
Published: August 2010

The fluorescence properties of neutral protease from B. subtilis have been investigated under a variety of conditions and the results compared with those previously reported for the homologous metalloendopeptidase thermolysin (Fontana et al., 1977). In the pH range 5–9 neutral protease displayed a quite unusual fluorescence emission spectrum with a maximum near 320 nm, when excitation was at 295 nm. At this wavelength the protein fluorescence is due to tryptophan residues only, which, considering their blue‐shifted emission, appear rather buried in the hydrophobic protein interior. Specific removal of the functional zinc ion from the enzyme with tetraethylenepentamine does not lead to alteration of the microenvironment around tryptophan residues. On the other hand, removal of both zinc and calcium with ethylenediaminetetraacetic acid brings these residues in full contact with the aqueous solvent medium. Fluorescence quenching measurements were also used to determine the exposure of tryptophan residues in the native enzyme as well as in the presence of chelating agents and protein denaturants. Melting profile experiments carried out by monitoring the fluorescence intensity at 320 nm indicated a cooperative transition at 60–70°. Temperature effects were also determined under conditions perturbed with respect to pH, guanidine hydrochloride and chelating agents. The results reveal differences in the fluorescence properties of the tryptophanyl residues of B. subtilis neutral protease relative to those of thermolysin, which are interpretable considering the location of these residues in the sequences of the two homologous proteins.
REVERSALS OF POLYPEPTIDE CHAIN IN GLOBULAR PROTEINS
Authors: KOLASKAR A.S. , RAMABRAHMAM V. , SOMAN K.V.
Published: August 2010

A simple algorithm has been developed to detect β‐bends and ‘loops’‐chain reversals containing five amino acid residues, using only coordinates of Cα‐atoms from crystal structure data of globular proteins using the above algorithm. Analysis of bends have showed that the total number of bends in each protein (TB) is linearly related to total number of non‐hydrophobic residues in that protein which in turn is related linearly to total number of amino acid residues. Secondly, we found that a large number of consecutive bends occur in each protein which give rise to on an average only three independent residues per turn. Positional preference of amino acid residues in chain reversals is stressed. Consideration of pairs of amino acid residues in positions (i + 1) and (i + 2) of bends seems to provide a more reliable basis for predicting chain reversals in proteins.
ISOLATION AND PROPERTIES OF A TRYPTOPHAN‐CONTAINING PEPTIDE FROM BOVINE AND TURKEY BRAINS
Authors: SWANN RAYMOND W. , SHINE NANCY , LI CHOH HAO
Published: August 2010

A tryptophan‐containing peptide has been isolated from bovine cerebral hemispheres. A similar peptide has also been isolated from the turkey brain. Isoelectric focusing on polyacrylamide gels shows the peptides to be essentially homogeneous. Both peptides consist of 67 amino acids with isoleucine at the COOH‐terminus. The NH2‐terminal residues cannot be detected by end‐group analysis. Both peptides exhibit 45–50%α‐helix as revealed by circular dichroism spectra.
STABILIZATION OF WHOLE MOLECULES OF GASTROPODAN HAEMOCYANINS BY CHLORHEXIDINE
Authors: VERSCHUEREN LAURENT J. , GIELENS CONSTANT , LONTIE RENÉ
Published: August 2010

Chlorhexidine aiacetate 0.01% stabilized the whole molecules of Helix pomatia α‐haemocyanin under dissociating conditions; in 1 M NaCl and in 1.42 M sucrose. Dissociation at low ionic strength (10 mM) of the haemocyanin of Pila leopoldvillensis was likewise prevented by chlorhexidine. After dissociation into half molecules of H. pomatia α‐haemocyanin in 1.42 M sucrose and of P. leopoldvillensis haemocyanin by lowering the ionic strength, whole molecules were formed on introduction by dialysis of chlorhexidine diacetate to a concentration of 0.01%. This stabilization points to the binding of the two chlorophenyl groups in hydrophobic regions of the protein and an ensuing cross‐linking of the half molecules of gastropodan haemocyanins. Chlorguanide, which almost corresponds to one half chlorhexidine, even at a concentration of 0.1%, only slightly stabilized the whole molecules.
PREFERRED CONFORMATION OF THE tert‐BUTOXYCARBONYLAMINO GROUP IN PEPTIDES
Authors: BENEDETTI ETTORE , PEDONE CARLO , TONIOLO CLAUDIO , NÉMETHY GEORGE , POTTLE MARCIA S. , SCHERAGA HAROLD A.
Published: August 2010

Structural parameters, derived from X‐ray crystallographic data, have been compiled for amino acid and linear peptide derivatives which contain the N‐terminal tert‐butoxycarbonyl (Boc) group or its next higher homolog, the tert‐amyloxycarbonyl group. The comparison of the geometry of the urethane group in Boc‐derivatives with that of the peptide group shows small differences in bond angles about the trigonal carbon, because of altered interactions when a CαH group of a peptide unit is replaced by an ester oxygen. In contrast to the strong preference of the peptide bond for the trans form (except when it precedes proline), the urethane amide bond adopts both the cis and trans conformations in crystals. The cis urethane conformation is preferred in crystals of compounds with a tertiary nitrogen (such as Boc‐Pro) or in structures stabilized by strong intermolecular interactions. Conformational energy computations on Boc‐amino acid N'‐methylamides indicate that the trans and cis conformations of the urethane amide bond have nearly equal energies (even for amino acids other than proline), in contrast to the peptide bond, for which the trans conformation has a much lower energy. The computed increase of the cis content in Boc‐amino acid derivatives (as compared with the corresponding N‐acetyl derivatives) is consistent with the observed distributions of conformations in crystal structures and with n.m.r. studies in solution. Usually, the substitution of a Boc for an N‐acetyl end group does not alter the conformational preferences (as indicated by φ, Ψ values and relative energies) of the amino acid residue which follows the end group when the amide bond is trans. Particular conformations, however, can be stabilized by strong attractive interactions between some side chains (e.g. that of phenylalanine) and the bulky Boc end group.
CONFORMATIONALSTUDY OF [LEU5]‐ENKEPHALIN BY LASER RAMAN SPECTROSCOPY
Authors: HAN SHAW‐LIN , STIMSON EVELYN R. , MAXFIELD FREDERICK R. , SCHERAGA HAROLD A.
Published: August 2010

The Raman spectrum of [Leu5]‐enkephalin in the solid state indicates the presence of a type I' ß bend, in agreement with X‐ray data of Smith & Griffin (1978). In solution, this molecule takes on different conformations in different solvents. In DMSO‐d6, it forms a ß‐bend structure whereas in water it exists as an ensemble of conformations.
CHROMATOGRAPHIC CHANGE IN HISTONE H3‐H4 PREPARATIONS DURING SHORT TERM STORAGE AND ITS REVERSAL BY BISULFITE
Authors: LEWIS RAMILLA O. , COX DAVID J. , REECK GERALD R.
Published: August 2010

Chicken erythrocyte histone H3‐H4 preparations stored at 4° in 50 mM sodium acetate (pH 5.0) exhibit altered gel chromatographic properties that are detectable within 2 days. After 5–7 days, material with chromatographic properties of the H3‐H4 tetramer is absent, but the H3 and H4 polypeptides are intact, as judged by gel electrophoresis. The change in chromatographic properties results from an oxidation reaction: The change is accelerated by bubbling oxygen through H3‐H4 preparations, and it is reversed by exposure to dithiothreitol. Because chicken erythrocyte H3 contains a single cysteine residue the oxidation reaction is intermolecular disulfide bond formation between H3 molecules. High molecular weight aggregates formed by the H3 dimers and some histone H4 probably are the same aggregates observed but unexplained by other workers. The H3‐H4 tetramer can be regenerated by exposure of aged preparations to bisulfite, presumably as a result of cleavage of disulfide bonds and formation of S‐sulfonated H3.
ORDERED CONFORMATIONS OF CATIONIC POLYPEPTIDES IN ANIONIC SURFACTANT SOLUTIONS*
Authors: IKEDA KIYOSHI , YANG JEN TSI
Published: August 2010

Ionic poly(L‐ornithine) at 45° adopts a helical conformation in the presence of sodium dodecyl sulfonate or phosphate just as it is in sodium dodecyl sulfate solution as evidenced from circular dichroic spectra. But the polypeptide remains unordered in sodium tridecanate. Under similar conditions ionic poly‐(L‐lysine) assumes the ß‐form in all four anionic surfactant solutions. In sodium dodecyl phosphata solution at 45° (Lys)n also undergoes a ß‐to‐helix transition in alkaline solution with a midpoint at pH 9.2, noting that dodecyl phosphoric acid has two dissociation constants with pKa of about 3 and 8. Raising the pH of the solution above 11 at 45° converts the helical conformation back to the ß‐form. This contrasts with a single ß‐to‐helix transition at pH 10.9 at 45° for (Lys)n in sodium dodecyl sulfate solution.
CHOLECYSTOKININ (PANCREOZYMIN)
Authors: BODANSZKY MIKLOS , TOLLE JOHN C. , GARDNER JERRY D. , WALKER MICHAEL D. , MUTT VIKTOR
Published: August 2010

The acetyl‐derivative of the biologically active C‐terminal 7‐peptide portion of cholecystokinin (CCK), N‐acetyl‐O‐sulfate‐L‐tyrosyl‐L‐methionyl‐glycyl‐L‐tryptophyl‐L‐methionyl‐L‐aspanyl‐L‐phenylalanine amide was prepared by the condensation of 2‐peptide segments with 1‐isobutyloxycarbonyl‐2‐isobutyloxy‐1,2‐dihydroquinoline as coupling reagent. The N‐terminal residue, tyrosine, was incorporated by the active ester method. The same 7‐peptide was prepared also by stepwise chain‐lengthening, starting with the C‐terminal residue. The 9‐fluorenylmethyloxycarbonyl group was applied for the protection of α‐amino functions.

In the release of amylase from acinar cells of the pancreas of guinea pigs, the acetyl‐7‐peptide amide was about 3 times more potent than CCK 27–33 and equal in potency to CCK 26–33. The new derivative strongly stimulated the contraction of the in situ guinea pig gall bladder.
TIME‐DEPENDENCY OF NEUROHYPOPHYSEAL PEPTIDE ATTENUATION OF PUROMYCIN AMNESIA IN MICE
Authors: WALTER RODERICH , HOFFMAN PAULA L. , FLEXNER JOSEFA B. , FLEXNER LOUIS B.
Published: August 2010

[Ile3, Arg8]. vasopressin (arginine‐vasotocin), as well as the C‐terminal tripeptides of the neurohypophyseal hormones arginine and lysine vasopressin, Pro‐Arg‐Gly‐NH2 and Pro‐Lys‐Gly‐NH2, were protective against puromycin‐induced amnesia in mice when administered 24h before training. The N‐protected tripeptide derivative, Z‐Pro‐Lys‐Gly‐NH2, was effective when given 5 days before training. The effectiveness of all peptides to attenuate puromycin‐induced amnesia decreased as the interval between training and peptide treatment increased, indicating that the peptides influence memory processes, rather than general arousal. Z‐Pro‐Lys‐Gly‐NH2 was active at 24h after training, when the other peptides were no longer effective. Although it seems clear that neurohypophyseal hormones per se can attenuate puromycin‐induced amnesia, these results are in line with the possibility that some portion of hormone action may be mediated via formation of longer‐lived hormone fragments in the CNS.
ANTIFREEZE GLYCOPROTEIN. Conformational Model Based on Vacuum Ultraviolet Circular Dichroism Data
Authors: BUSH C. ALLEN , FEENEY ROBERT E. , OSUGA DAVID T. , RALAPATI SURESH , YEH YIN
Published: August 2010

Circular dichroism spectra (CD) of an active fraction of antifreeze glycoprotein (AFGP) and of a lower molecular weight fraction which is less active are found to be similar in the wavelength range 170–230 nm. The contribution of the disaccharide side chain chromophores to the CD spectra of the glycoprotein is estimated from spectra of model oligosaccharides having similar structures. Comparison of the CD spectra of the peptide portion of AFGP to those of established model polypeptides suggests a 3‐fold left‐handed helix of the collagen type as the most likely conformation of the peptide. In the proposed model, the disaccharide moieties attached to every third residue are in identical environments. Furthermore, proline residues which are found in the less active fraction can be accommodated in this helical structure, consistent with the observed similarity of the spectra of the two fractions.
SECONDARY STRUCTURE RELATIONS BETWEEN BETA‐LACTAMASES AND PENICILLIN‐SENSITIVE D—ALANINE—CARBOXYPEPTIDASES
Authors: MOEWS PAUL C. , KNOX JAMES R. , WAXMAN DAVID J. , STROMINGER JACK L.
Published: August 2010

The sequence homology found by Waxman & Strominger between penicillin‐sensitive d‐alanine‐carboxypeptidases and penicillin‐inactivating beta‐lactamases is shown to extend to the level of secondary structure as predicted by the method of Chou & Fasman or by the informational method of Garnier et al. Thermodynamic similarity of homologous segments of these proteins is demonstrated by means of a sequence‐independent parameter, the hydration potential of Wolfenden et al. Although the 40‐ to 70‐ residue amino‐terminal sequences examined contain a common serine reactive with pencillins and (in the case of the carboxypeptidases) an R‐D‐alanyl‐D‐alanine substrate analog, no homology in secondary structure or hydration potential could be found with a serine protease such as α‐chymotrypsin.
HUMAN β‐ENDORPHIN: SYNTHESIS AND BIOLOGICAL ACTIVITY OF ANALOGS WITH SUBSTITUTIONS IN POSITIONS 2, 9, 18, 27 AND 31
Authors: YEUNG HIN‐WING , YAMASHIRO DONALD , TSENG LIANG‐FU , CHANG WEN‐CHANG , LI CHOH HAO
Published: August 2010

Four analogs of the opioid peptide human β‐endorphin (βh‐EP) have been synthesized: [d‐Lys9,Phe27,Gly31]‐βh‐EP, [d‐Phe18,Phe27,Gly31)‐βh‐EP, [d‐Thr2,d‐Lys9,Phe27,Gly31]‐βh‐EP, and [d‐Thr2,d‐Phe18,Phe27,Gly31]‐βh‐EP. All are practically indistinguishable from βh‐EP in the guinea pig ileum assay. All show diminished analgesic potency in the mouse tail‐flick assay.
ANALYTICAL ISOTACHOPHORESIS IN PEPTIDE CHEMISTRY: I. Analysis of Anions in Peptides*
Authors: van NISPEN J.W. , JANSSEN P.S.L. , GOVERDE B.C. , SCHERDERS J.C.M. , van DINTHER F. , HANNINK J.A.J.
Published: August 2010

The application of analytical capillary, carrier‐free isotachophoresis as a rapid method (approx. 10–15 min per run) for the simultaneous determination of anions present in peptides (as counterion, contaminating ion or peptide anion) is described. Only small amounts of material, approx. 0.1–1.0 mg, are necessary to obtain information on the nature of the anion (qualitative) and of the amount of anion present (quantitative aspect).
ACCELERATED METHOD FOR COMPARING AMINO ACID SEQUENCES WITH ALLOWANCE FOR POSSIBLE GAPS: Plotting Optimum Correspondence Paths
Authors: POZDNYAKOV V.I. , PANKOV YU.A.
Published: August 2010

An accelerated method is suggested which enables an effective comparison to be made of amino acid (nucleotide) sequences of great length with due regard to a large number of possible gaps. The method consists in limiting the area of com plete similarity charts, calculated in accordance with the algorithm suggested by Sankoff (1972), by a certain specially selected diagonal band. The application of the Monte‐Carlo method permits a statistical evaluation to be made of the certainty of the similarity of the compared sequences and to choose on such a “comparison band”, an optimum “correspondence path” which can readily be transformed into sequence alignment. Using this approach, prolactin and somato tropin families of sequences were found to be homologous at a high level of significance and their optimum alignment with two gaps has been suggested. In contrast, two regions of assumed partial gene duplication in β‐galactosidase sequence, suggested by Hood et al. (1978), were found not to be statistically significantly similar.
SPECTROSCOPIC STUDY OF THE CONFORMATIONS OF PROLINE‐CONTAINING OLIGOPEPTIDES IN THE CRYSTALLINE STATE AND IN SOLUTION
Authors: HAN SHAW‐LIN , STIMSON EVELYN R. , MAXFIELD FREDERICK R. , SCHERAGA HAROLD A.
Published: August 2010

A conformational study has been carried out on a series of linear proline‐containing oligopeptides (ZGP, ZGPL, ZGPLG and ZGPLGP) in both the crystalline state and in DMSO‐d6, solution, using Raman and n.m.r. spectroscopy. The amide I and HI bands in the Raman spectra of the crystalline forms indicate the presence of a type I β‐bend conformation in ZGPLG and ZGPLGP, but not in ZGP and ZGPL. This result is in agreement with X‐ray data on these mole cules. The Raman spectra of these peptides in solution indicate that more than one conformation is present, i.e. that the β‐bend structure of the solid form of ZGPLG and ZGPLGP is destabilized by DMSO‐d6. 13C and 1H n.m.r. data also demonstrate the presence of more than one conformation in ZGP, ZGPL, ZGPLG and ZGPLGP in DMSO‐d6 solution. These isomers differ in their con formation (cis and trans) about their Gly‐Pro peptide bonds and possibly about the Cα‐C' bond of the C‐terminal proline in ZGPLGP. For ZGP, ZGPL, ZGPLG and ZGPLGP, the ensemble of conformations in DMSO‐d6 includes C5 and C7 hydrogen‐bonded rings; in addition, ZGPLGP may contain a small percentage of a β‐bend conformation (at Pro2‐Leuj3) with trans peptides in both Gly‐Pro moieties.
RIGIN, ANOTHER PHAGOCYTOSIS‐STIMULATING TETRAPEPTIDE ISOLATED FROM HUMAN IgG: Confirmations of a Hypothesis
Authors: VERETENNIKOVA N.I. , CHIPENS G.I. , NIKIFOROVICH G.V. , BETINSH YA. R.
Published: August 2010

Structure‐function and conformational studies of the molecule of phagocytosis‐stimulating tetrapeptide tuftsin permitted the conclusion that among products resulting from splitting of H‐chain of IgG Human EU by trypsin, besides tuftsin (sequence 289–292), tuftsin‐like tetrapeptide Gly‐Gln‐Pro‐Arg may be also present; theoretical conformational analysis shows a considerable similarity of spatial arrangement of this tetrapeptide and tuftsin which testifies in favour of potential tuftsin‐like activity of the tetrapeptide. Gly‐Gln‐Pro‐Arg was synthesized and its phagocytosis stimulating activity was found equal to that of tuftsin.
REACTION OF OSMIUM REAGENTS WITH AMINO ACIDS AND PROTEINS: Reactivity of Amino Acid Residues and Peptide Bond Cleavage
Authors: DEETZ J.S. , BEHRMAN E.J.
Published: August 2010

We report a study of the relative reactivity of the common amino acids and of their residues in lysozyme with osmium tetroxide, the osmium tetroxide‐pyridine reagent, and with the oxo‐osmium(VI)‐pyridine reagent. With free amino acids, the osmium(VIII) reagents are most reactive with Met, Cys, His, Thr, Ser, Trp, Lys, and Pro; the osmium(VI) reagent only reacts significantly with His, Met, Cys, Thr, and Ser. In lysozyme, only Cys, Met, and Trp react extensively with the osmium(VIII) reagents; with the osmium (VI) reagent, Cys and Met are most reactive. We also note evidence both for cross‐linking of proteins and for peptide bond cleavage, which appears to have considerable specificity for tryptophanyl residues.
TRIPLE HELIX COIL TRANSITION OF A BLOCKPOLYMER WITH THE SEQUENCE BOC‐(GLY‐PRO‐PRO)5‐(GLY‐PRO‐LEU)5‐(GLY‐PRO‐PRO)5‐NH2
Authors: ROTH W. , HEIDEMANN E.
Published: August 2010

The thermal triple helix coil transition of a blockpolymer with the sequence Boc‐(Gly‐Pro‐Pro)5‐(Gly‐Pro‐Leu)5‐(Gly‐Pro‐Pro)5‐NH2 was studied optically. The collagen model peptide was soluble in methanol/water (9:1, 3:1) and was found to form triple helical structures in this solvent system. The thermodynamic analysis of the transition curves showed that the sequence (Gly‐Pro‐Leu)5 is part of the triple helix after renaturation of the blockpolymer.
CONFORMATIONAL STABILITY OF FRUCTOSE‐1,6‐BIPHOSPHATE ALDOLASE FROM CERATITIS CAPITATA
Authors: GAVILANES F.G. , GAVILANES J.G. , MUNICIO A.M.
Published: August 2010

Fructose 1,6‐biphosphate aldolase from Ceratitis capitata is a tetramer of identical subunits with 34% α‐helix, 22% β structure and 44% of aperiodic order. Increase of urea concentration up to 4.0 M results in non‐cooperative reversible dissociation of the enzyme. Sodium dodecylsulphate 0.06% (w/v) dissociates the tetramer cooperatively with retention of the helical content. Thermal denaturation was a non‐reversible cooperative process with a midpoint for the transition at 55°. Cysteine residues are involved in this process and 2‐mercapto‐ethanol preserves partially the enzyme activity. The acidic dissociation of the enzyme is a non‐reversible process in contrast to the reversible basic dissociation. Increase of ionic strength results in a more ordered secondary structure for the monomer after acidic dissociation.
CONFORMATIONAL CHARACTERISTICS OF THE N‐ACETYL‐N‘‐METHYLAMIDES OF THE FOUR (LYS, TYR) DIPEPTIDES
Authors: RAE I.D. , LEACH S.J. , MINASIAN E. , SMITH J.A. , ZIMMERMAN S.S. , WEIGOLD J.A. , HODES Z.I. , NÉMETHY G. , WOODY R.W. , SCHERAGA H.A.
Published: August 2010

The conformational properties of the N‐acetyl‐N'‐methylamides of the dipeptides lysyl‐lysine, lysyl‐tyrosine, tyrosyl‐lysine, and tyrosyl‐tyrosine were studied by means of conformational energy calculations, by n.m.r. measurements in deuterated dimethylsulfoxide, and by circular dichroism in water, methanol, dioxane‐water, and trifluoroethanol. Since these four dipeptides occur occasionally as bends in proteins, it was of interest to see whether short‐range interactions, acting within the terminally blocked dipeptides, are sufficient to stabilize bend conformations significantly over other conformations. It was found that the four dipeptides exist as ensembles of conformations in solution. Therefore, it appears that longer‐range interactions, such as those present in proteins, are required if bend conformations of these dipeptide sequences are to exist as stable conformations. Three of the dipeptides behave rather similarly. Both the CD and the n.m.r. experiments and computations indicate that the fourth (Lys‐Tyr) differs from the others. It has a preference for compact conformations that appear to be stabilized by strong favorable interactions, primarily hydrogen bonds, between the tyrosyl and the lysyl side chains. The computations suggest that the presence of these interactions, and hence the existence of preferred conformations, is strongly solvent‐dependent, and that these interactions are weakened in aqueous solution.
CLEAVAGE OF DEHYDROALANINE‐CONTAINING PEPTIDES WITH MERCURIC ACETATE
Authors: EDGE ALBERT S.B. , WEBER PETER
Published: August 2010

The dehydroalanine containing peptides glycyldehydroalanine and t‐butyloxycarbonyl‐L‐alanyldehydroalanyl‐β‐methyl‐D,L‐aspartic acid methyl ester were synthesized, respectively, from chloroacetamide and pyruvate and from t‐butyloxycarbonyl‐L‐alanyl‐S‐methyl‐L‐cysteinyl‐β‐methyl‐D,L ‐aspartic acid methyl ester. They were reacted with mercuric acetate in water, 50% methanol and dimethylformamide at 25° and at 80° for various time periods. Reaction proceeded to yield an amino acid amide from the N‐terminal side of the unsaturated residue and pyruvate from the C‐terminal side. Yields of amino acid amides were 76% for the dipeptide and 40% for the tripeptide. The applicability of the neutral reaction conditions employed to the cleavage of glycoproteins containing both O‐ and N‐glycosidically‐linked carbohydrate chains following β‐ elimination of the serine and threonine linked oligosaccharides is pointed out.
CIRCULAR DICHROISM SPECTRA OF TRYPSIN AND CHYMOTRYPSIN COMPLEXES WITH BOWMAN‐BIRK OR CHICKPEA TRYPSIN INHIBITOR
Authors: JIBSON MICHAEL D. , BIRK YEHUDITH , BEWLEY THOMAS A.
Published: August 2010

Circular dichroism spectra of trypsin and chymotrypsin complexes with Bowman‐Birk soybean inhibitor or chickpea inhibitor have been determined at neutral and acid pH. Trypsin spectra show no evidence of conformational change accompanying the binding of either inhibitor to the enzyme. The formation of chymotrypsin‐inhibitor complexes may involve a minor change in tertiary structure, as shown by a CD shift between 250 and 320 nm.
CONFORMATION OF CYCLO‐(l‐THREONINE)2 AND CYCLO‐(l‐ALLO THREONINE)2
Authors: KOPPLE KENNETH D. , NARUTIS VYTAUTAS
Published: August 2010

The diketopiperazines cyclo‐(l‐Thr)2 and cyclo‐(l‐allo Thr)2 in water and in dimethyl sulfoxide were studied by proton and carbon‐13 nuclear magnetic resonance, and the dominant conformations were deduced from proton‐proton and proton‐carbon coupling constants. In cyclo‐(l‐Thr)2 the χ1 = 60°, hydroxyl over the ring, side chain conformation is favored; this conformation is also favored for cyclo‐(l‐Ser)2 and cyclo‐(l‐Ser‐d‐Ser). However, the important side chain conformation for cyclo‐(l‐allo Thr)2 is χ1 = ‐60°, methyl group over the diketopiperazine ring. The determining factors are apparently steric. The diketopiperazine ring of cyclo‐(l‐Thr)2 is puckered to hold the side chains more nearly axial than is that of cyclo‐(l‐allo Thr)2, although the degree of ring folding is probably not large.
MODIFICATION OF LYSINE 69 REACTIVITY IN BOVINE GROWTH HORMONE BY CARBAMYLATION OF ITSN‐TERMINAL GROUP
Authors: NOWICKI C. , SANTOMÉ J.A.
Published: August 2010

Bovine growth hormone was carbamylated under conditions that assure full reaction of theN‐terminal residue. Approximately 28% of lysine 179 and 7% of lysine 143 were also carbamylated. The modified hormone retained an important growth promoting activity and was as effective as the native hormone in competition assaysin vivofor the receptors in rat liver. However, a change in its conformation must occur since lysine 69, which is resistant to trinitropheny‐ lation in the native hormone, reacted easily and under mild conditions, in the carbamylated protein. The growth promoting activity and binding properties of the carbamylated and trinitrophenylated hormone were practically nil.
POTENTIATION OF BRADYKININ WITH SYNTHETIC PEPTIDES ON GUINEA PIG ILEUM
Authors: RAGNARSSON ULF , SYVÄNEN ANN‐CHRISTINE , HAMBERG ULLA
Published: August 2010

Potentiation of the activity of bradykinin on the isolated guinea pig ileum was studied using a designed test system with the synthetic peptides Leu‐Val‐Glu‐Ser‐Ser‐Lys, Thr‐Pro‐Val‐Ser‐Glu‐Lys, derivatives of the former coupled to theN‐ andC‐terminals of bradykinin and two peptides with phenylalanine substituted with its isomerl‐3‐amino‐3‐phenylpropanoic acid in the 5‐ and 5,8‐positions in bradykinin respectively. On average, two times potentiation effects were obtained at 10‐6to 10‐8M concentrations of the peptides. After elimination of the basic lysine no potentiation occurred with synthetic Leu‐Val‐Glu‐Ser‐Ser. With the [βPhe5,8]‐bradykinin a mixed sensitizing/potentiating effect was observed, suggesting that a separation of the two effects may be difficult with an intact receptor structure of this kind. This peptide was not hydrolyzed by carboxypeptidase B or chymotrypsin.
DEMONSTRATION OF AN ENDOGENOUS, HIGHLY POTENT, NONCOMPETITIVE PROTEIN INHIBITOR(S) OF 3H‐DIAZEPAM BINDING IN BOVINE BRAIN
Authors: KENESSEY ÁGNES , LÁNG TIBOR , GRÁF LÁSZLÓ
Published: August 2010

Extracts from bovine brain show significant diazepam displacing activity in receptor binding assay. The proteinase sensitive component of this benzo‐diazepine‐like activity has been resolved into three main fractions by chromatography on a Sephadex G‐75 column. The most active fraction that contains the largest proteins has been further characterized and shown to be a noncompetitive inhibitor of the diazepam binding to synaptic brain membranes.
ISOLATION AND CHARACTERIZATION OF β‐LIPOTROPIN FROM THE PITUITARY GLAND OF THE OSTRICH, STRUTHIO CAMELUS
Authors: NAUDÉ RYNO J. , OELOFSEN WILLEM
Published: August 2010

Avian β‐lipotropin (β‐LPH) was purified from adenohypophyseal glands of the ostrich Struthio camelus by a procedure involving acid/acetone extraction, NaCl fractionation, CM‐cellulose chromatography, Sephadex G‐75 chromatography and paper electrophoresis (pH 6.7). The 90‐amino acid peptide behaved as a single substance during polyacrylamide‐gel electrophoresis, isoelectric focusing (pI of 6.0) and N‐terminal analysis, the N‐terminal amino acid being alanine. Ostrich β‐LPH exhibited lipolytic activity corresponding to an average minimal effective dose of 0.088 μg in rabbit adipose tissue.
STUDIES ON PEPTIDES
Authors: AKAJI KENICHI , FUJII NOBUTAKA , YAJIMA HARUAKI , MORIGA MOTOYUKI , AONO MITSURU , TAKAGI ATSUSHI
Published: August 2010

The heptacosapeptide amide corresponding to the entire amino acid sequence of gastrin‐releasing peptide (GRP) was synthesized by assembling seven peptide fragments followed by deprotection with a new reagent system, IM trifluoro‐methanesulfonic acid‐thioanisole in TFA. The deprotected peptide was purified by ion‐exchange chromatography on CM‐cellulose followed by partition chromatography on Sephadex G‐25. The latter was found to remove effectively the Met (O) derivative of GRP. The highly purified synthetic GRP was active as synthetic bombesin on the molar basis. A new carboxyl‐activating reagent, thiazoline‐2‐thione, was employed for preparation of the necessary fragments.
CONFORMATIONAL ENERGY CALCULATIONS ON ENKEPHALINS AND ENKEPHALIN ANALOGS:
Authors: Manavalan Parthasarathy , Momany Frank A.
Published: August 2010

Conformational energy calculations were carried out on the peptide enkephalins (ENK) and selected analogs to find those conformers of low energy. The analogs studied include [D‐Ala2]Enk‐NH2, [D‐Ala2]Enk, [D‐Met2, Pro5]Enk‐NH2, [D‐Ala2, D‐Phe5]Enk, [D‐Ala2, D‐Leu5]Enk, [D‐Ala2, (N‐Me)Phe4, Met5] Enk‐NH2 and [D‐Ala2, (N‐Me)Met5]Enk‐NH2. When the low‐energy conformers for all the analogs are compared, different allowed backbone conformations are found which orient the functional side‐chains such that three classifications of structures appear. Each classification shows a unique configuration of side‐ chain positions in space even though different backbone conformations are found within each classification.
β‐ENDORPHIN:
Authors: Jibson Michael D. , Li Choh Hao
Published: August 2010

The a‐helix content of human β‐endorphin (βh‐EP) has been determined by circular dichroism (CD) in solutions ranging from 0 to 95% methanol in water. In addition, the CD spectra of βh‐EP‐(1–30),‐(1–29),‐(1–28),‐(1–27),‐(1–26), ‐(1–21) and ‐(1–15) have been examined in 90% methanol, and their a‐helix contents estimated using parameters determined for this solvent. Addition of methanol to βh‐EP solutions brings about a noncooperative formation of a‐helix. An attempt to correlate secondary structure in methanol with biological and immunological activities showedlimited direct correspondence, but may indicate the involvement of tertiary interactions.
INTERACTION OF THE THREE MAIN COMPONENTS OF CLUPEINE WITH GLYCOSAMINOGLYCANS
Authors: Bertanzon F. , Stevens E.S. , Toniolo C. , Bonora G.M.
Published: August 2010

The interactions between each of the three main components of clupeine (YI, YII and Z) and the glycosaminoglycans chondroitin sulfate, heparin and hyaluronic acid were studied with circular dichroism spectroscopy. The induced dichroism is a measure of relative complex stability, which increases with the number of sulfate groups on the glycosaminoglycan. Measuring the induced dichroism as a function of mole ratio of disaccharide to arginine establishes the stoichiometry of the complexes. For a given glycosaminoglycan, the induced dichroism depends on the clupeine, increasing in the order YI < YII < Z.
LABELING OF AMINO ACIDS AND PEPTIDES WITH ISOTOPIC OXYGEN AS FOLLOWED BY 17O‐N.M.R.*
Authors: Steinschneider A. , Burgar M.I. , Buku A. , Fiat D.
Published: August 2010

17O was introduced into the respective α‐ and γ‐COOH groups of Boc‐Gly and Boc‐Glu by saponification of the corresponding O‐methyl esters with 1 N NaOH in H217O. Other 17O enriched Boc‐amino acids were prepared by acid catalyzed exchange into the amino acid α‐COOH group followed by t‐butyloxycarbonylation with t‐butyl S‐4, 6‐dimethylpyrimidin‐2‐ylthio carbonate. Final enrichment, by approximately three orders of magnitude over natural abundance, was 60–100% of the possible maximum. The synthesis of [17O]‐Gly‐Ala, [17O]‐Gly‐Leu and [17O]‐Gly‐Glu by DCC/HBT mediated coupling of Boc‐Gly‐[17'O]‐α‐COOH with amino acid‐O‐t‐butyl esters followed by deprotection with HCl/EtOAc proceeded without undue loss of the isotope. Boc‐[17O]‐Pro‐Leu‐Gly‐NH2 was prepared by a similar procedure. [Tyr2–17O]‐, [Pro7–17O]‐ and [Gly4–17O]‐oxytocin were synthesized using solid phase support. 17O‐chemical shifts of synthetic intermediates and of the final products were as expected for each functional group. Linewidth data correlate with the molecular weights of the compounds prepared.
CLOSTRIPAIN‐CATALYZED RE‐FORMATION OF A PEPTIDE BOND IN A CYTOCHROME C FRAGMENT COMPLEX*
Authors: Juillerat Marcel , Homandberg Gene A.
Published: August 2010

Enzymatically‐catalyzed condensation of cytochrome c fragments, ferrous heme fragment (1–38) and apofragment (39–104), has allowed the back‐conversion of cytochrome c complex to native cytochrome c. The conversion was accomplished in 90% (v/v) glycerol, a solvent which has been shown to decrease the ionization of the terminal α‐carboxyl group liberated during hydrolysis of a peptide bond. The effect on the pK is probably the main reason the thermodynamic obstacle to re‐synthesis is minimized. A 30% conversion to cytochrome c was obtained. The cytochrome c product was distinguished from the non‐covalent complex and separated fragments by molecular weight analysis with sodium dodecyl sulfate polyacrylamide gel electrophoresis, by elution from Sephadex G‐50 and sulfopropyl‐Sephadex in the presence of denaturant, by amino acid analysis of the product purified under complex‐dissociation conditions, and by spectral analysis of the absorption bands of the heme. This method provides an opportunity to study the covalent rather than the complex form of cytochrome c analogs.
HUMAN SOMATOTROPIN: Noncovalent Interaction of Two Thrombin Fragments Restores Receptor‐Binding Activity*
Authors: Graf Laszloa , Cheng Christoper H.K. , Li Choh Hao
Published: August 2010

Two thrombin fragments of reduced carbamidomethylated human somatotropin containing the full primary structure of the native hormone (residues 1–134 and 135–191) were shown to give a recombinant with the same receptor‐binding activity as reduced‐carbamidomethylated somatotropin as tested on rabbit liver and mammary gland membranes.
POLARIZATION FLUORESCENCE STUDIES ON PROTEOLYTIC ACTIVITY OF α2‐MACROGLOBULIN‐TRYPSIN COMPLEXES
Authors: Karic Lucija , Glaser Charles B.
Published: August 2010

When digestive enzymes are released into the blood, they may be completely inactivated by a variety of inhibitors present (alpha‐1‐protease inhibitor, antithrombin III, α2‐plasmin inhibitor, etc.) or only partially neutralized by α2‐macroglobulin. In this study, polarization fluorescence is used to demonstrate that complexes of α2‐macroglobulin with trypsin can digest β‐endorphin, adrenocorticotropin, and β‐lipotropin. Furthermore, it has been shown that a small trypsin inhibitor (trasylol, mol. wt. 6500) can prevent this digestion, but that larger inhibitory proteins (i.e. soybean trypsin inhibitor, mol. wt. 21 500; α1‐protease inhibitor, mol. wt. 50000) cannot.
β‐ENDORPHIN:
Authors: Wong T.M. , Koo A. , Li Choh Hao
Published: August 2010

β‐Endorphin, enkephalins and morphine dilated in vivo the arteriole of the microcirculatory system in hamster cheek pouch. β‐Endorphin had the highest potency and morphine the lowest. The effect was dose dependent and blocked competitively by the opiate antagonist, naloxone. The result demonstrated an effect of the opiates on the arteriole of the cutaneous circulation. This effect probably plays an important role in thermoregulation.
COMPLETE SEQUENCE OF THE GLYCOSYLATED AMINO TERMINAL SEGMENT OF PORCINE PRO‐OPIOMELANOCORTIN
Authors: Lariviere N. , Seidah N.G. , Chretien M.
Published: August 2010

The complete sequence of an anterior pituitary glycopeptide corresponding to the first 80 amino acid residues of the amino terminal of pro‐opiomelanocortin (POMC) after excision of the signal peptide is reported. This peptide isolated from pig pituitaries shows considerable sequence conservation with its predicted homologues from bovine, murine and human species.
Partial molal heat capacity of the peptide group in aqueous solutions
Authors: Mishra A.K. , Ahluwalia J.C
Published: August 2010

Integral enthalpies of solution at very high dilution of sodium salts of N‐acetyl amino acids, N‐acetyl peptides, and N‐benzoyl glycine have been measured in water at 298.15 and 308.15 K. Standard heat capacities of solution at 303.15 K have been derived from the enthalpy of solution data. The peptide backbone‐unit (CH2CONH) contribution toward the limiting partial molal heat capacities derived from these experimental results is compared with those obtained from Cp2 of other model compounds, viz. oligopeptides, pyrrolidones, piperidones, diketopiperazine, and amides. Cp2 of the peptide backbone unit observed in the sodium salts of the N‐substituted amino acids and peptides is also correlated with the structural details of the compounds and it is concluded that Cp2 contribution of the whole CH2CONH group, rather than that of CONH group, should be used for predicting the heat capacities of polypeptides and proteins in aqueous solution.
Synthesis of an analogue of α‐MSH‐(1–10)‐decapeptide as a substrate for enzymatic Nα‐acetylation
Authors: DRIESSEN H.P.C. , BLOEMENDAL H. , DE JONG W.W. , TESSER G.I.
Published: August 2010

The synthesis of a stable substrate for enzymatic Nα‐acetylation is described. To this end an analogue of α‐MSH‐(1–10)‐decapeptide with norleucine instead of methionine at position 4 is prepared. t‐Butylation of an intermediate Z‐Tyr‐OMe leads only to about 75% conversion in a few hours' reaction time, and cannot be carried to completion. The [Nle4]‐decapeptide is as good a substrate for enzymatic Nα‐acetylation as the original decapeptide containing methionine.
Caiman crocodylus hemoglobin
Authors: LECLERCQ F. , STANGL A. , SCHRANK B. , VANDECASSERIE C. , PAUL C. , SCHNEK A.G. , LEONIS J. , BRAUNITZER G.
Published: August 2010

In some reptiles, the hemoglobin oxygen affinity is lowered only by CO2 and not by the usual phosphate cofactors. To understand the molecular mechanism of this regulation, Caiman crocodylus hemoglobin's primary structure has been determined. The alignment of the 141 residues of the α chain as well as the 146 of the β chain were obtained by classical method of sequence analysis and are compared with some mammalian, avian, amphibian, and fish hemoglobin chains. Furthermore, from these sequences, it is possible to explain the non‐interaction of phosphorylated cofactors with the caiman deoxyhemoglobin on the basis of mutations of the amino acids responsible for their fixation on the β chain. Among these residues only lysine β82 is unchanged. In addition a site has been proposed for the fixation of HCO3‐ which involves ionic bonds with serine β1 and glutamic acid β144 (Perutz et al. (1981) Nature 291, 682–684) (1).
Metal‐peptide interactions: enkephalin rigidifications
Authors: HARAN RAYMOND , SHARROCK PATRICK , GAIRIN JEAN , MAZARGUIL HONORÉ
Published: August 2010

Two enkephalin analogues, Tyr‐d‐Ala‐Gly‐Phe‐NVal‐NH2 and Tyr‐d‐Ala‐Gly‐Phe‐NVal‐OH were studied by n.m.r. spectroscopy. 13C chemical shifts were determined as a function of pH and in water‐dimethyl sulfoxide solvent mixtures. The acid and amide forms of the analogues show a marked difference in their n.m.r. features. Complexation with metal ions causes changes in the n.m.r. spectra of the acid form. The temperature dependence of the NH proton resonances of the zinc complex shows striking similarity with that of the amide analogue. The results are discussed in terms of the potential modification of biological activities which may occur following metal ion induced conformation changes.
Primary structure of seiwhale pituitary somatotropin
Authors: PANKOV Yu. A. , BULATOV A.A. , OSIPOVA T.A.
Published: August 2010

Seiwhale somatotropin has been isolated from seiwhale pituitaries. It was cleaved by cyanogen bromide, trypsin and chymotrypsin. The peptide fragments were separated and purified by gel filtration on Sephadexes, ion exchange chromatography, high voltage electrophoresis and paper chromatography. Amino acid sequences of the isolated peptides were studied by the dansyl‐Edman procedure. The data obtained suggested a primary structure of seiwhale somatotropin consisting of 190 amino acid residues and showed a high degree of homology with somatotropins of many other species.