bluuebunny/crossref_metadata_2025 huggingface dataset:
SEQUENCE DEPENDENT DEAMIDATION RATES FOR MODEL PEPTIDES OF CYTOCHROME C
Authors: Robinson Arthur B. , McKerrow James H. , Legaz Mark
Published: August 2010

The rates of deamidation in pH 7.5, 0.15 M, 37.0°C phosphate buffer of pentapeptide models of the sequences found near asparaginyl and glutaminyl residues in cytochrome c were measured. These rates were used to calculate a sequence‐determined half‐life for non‐deamidated cytochrome c. The sequence‐determined deamidation rates of the pentapeptide models were compared with the in vivo and in vitro deamidation rates of cytochrome c and the in vivo turnover rate of cytochrome c. Deamidation of the peptides during synthesis and purification was also measured. The implications of these measurements for deamidation as a biological molecular timer and deamidation during peptide synthesis are discussed.
CONFORMATIONAL STUDIES ON LARGE FRAGMENTS OF BOVINE SERUM ALBUMIN IN RELATION TO THE STRUCTURE OF THE MOLECULE
Authors: Hilak M. C. , Harmsen B. J. M. , Braam W. G. M. , Joordens J. J. M. , van Os G. A. J.
Published: August 2010

A model of albumin is proposed which accounts for the behaviour of bovine serum albumin during proteolytic hydrolysis by several enzymes. This model is tested and confirmed by conformational studies on large fragments of albumin at acid and neutral pH by means of optical rotation and hydrogen ion titration. The isolation of some fragments is described. It is suggested that BSA is a compact molecule at neutral pH, while in the F‐configuration it is composed of a compact NH2‐terminal moiety, and a COOH‐terminal part with a loose structure, which is very susceptible to proteolytic cleavage. The N‐F transition can be interpreted as an isomerization of the NH2‐terminal moiety, without loss of helix content, and an unfolding of the COOH‐terminal part in a cooperative process. Some parallelism between acid and neutral transition is demonstrated.
PRESENCE OF REPEATING SUB‐SEQUENCES AND SYMMETRY PATTERNS IN PROTEINS
Authors: Erhan Semih , Greller Larry D.
Published: August 2010

Comparison of amino acid sequences of ancestrally unrelated proteins as well as a particular protein with itself, using a sliding match performed by a computer (Greller & Erhan, previous paper), reveals the presence of certain repeating sequences. Furthermore, a symmetry pattern is observed if either the target or the key sequence is reversed, written from the carboxyl to amino terminus when a protein is matched against itself. The significance of these findings is discussed, particularly in reference to the possibility of these repeating sequences to represent primordial sub‐sequences from which proteins might have been formed.
THE MAJOR LETHAL NEUROTOXIN OF THE VENOM OF NAJA NAJA PHILIPPINENSIS:
Authors: Hauert Jacques , Maire Michel , Sussmann Alexandre , Bargetzi J. Pierre
Published: August 2010

The major lethal component of the venom of Naja naja philippinensis has been extracted and extensively purified, up to complete homogeneity, by physical and chemical standards and by exacting immunological tests. The method of preparation, aimed at preserving the native conformation, avoids the polystyrene resins commonly used for such toxins, but relies exclusively on hydrophilic supporting media and takes advantage of the extreme affinity of salt‐free neurotoxin for wetted poly‐dextran gels in order to increase the efficiency considerably. The pure toxin has an LD50 of 0.05 μg/g, is a single chain polypeptide of 61 residues, has a mol. wt. of 6867, a pI of 10.8, and an unusually high absorptivity, 14,300 at 280 nm, when compared to all known parent toxins. At 10‐4 to 10‐5 M and slightly acidic pH, equilibrium sedimentation failed to provide evidence for dimerization or conformational heterogeneity. This minute and tightly assembled protein molecule belongs to type I neurotoxins of snake venoms, acting selectively by inhibiting myofibrillar membrane depolarization in excitatory synapses and blocking myoneural transmission to striated muscles, particularly those involved in pulmonary ventilation. This neurotoxin brings about two new and unexpected features: 1) It differs from all known isotoxins of type 1 by having Ala in its composition, located at position 11 in the sequence, an amino acid so far considered as typical of type II neurotoxins of more recent origin, and of all other isotoxins of higher mol. wt. 2) Strikingly, it contains two Trp instead of the unique Trp characteristic of all neurotoxins described so far. Though the unique ancestral Trp has been claimed repeatedly to play a critical role in lethality of all neurotoxins, the present sidewise duplication shows no influence on the LD50. ORD‐CD profiles display β sheet structure predominantly, an observation consistent with the occurrence of a majority of non helix‐formers in the two largest stretches. A third large loop, where hydrophobic and all the aromatic side chains are packed, may have helical conformation. Though denaturation in 6 M guanidine‐HCl releases completely randomized structures, as apparent by ORD‐CD, the unfolding in 10 M urea is far from complete and remains fully reversible. Fluorescence investigations by reversible solvent perturbation using methanol or urea confirm localized unfolding accompanied by the translation of the unique Tyr chromophore from the interior out to the surface of the molecule, whereas both Trp chromophores appear unaffected except for minor hyperchromatism. These residues may not necessarily be directly involved in the receptor‐complex formation, but may be essential for conformational stabilization. Whether neurotoxin engages in this binding process as a rigid ligand or by some kind of “induced‐fit” is a matter for further investigations.
FACILE ASSIGNMENT OF DISULFIDE BONDS IN OVINE LACTOGENIC HORMONE AND HUMAN GROWTH HORMONE
Authors: Glaser Charles B. , Maeda Hiroshi , Meienhofer Johannes
Published: August 2010

A procedure, recently developed in this laboratory, for the rapid determination of the positions of disulfide bonds in proteins of known amino acid sequence was applied to the assignment of the disulfide bonds of ovine lactogenic hormone and human growth hormone. Each protein was hydrolysed by pepsin under conditions where disulfide interchange does not occur. Peptide maps of the resulting hydrolysates were prepared. Sodium borohydride reduction and subsequent treatment with S,S'‐dithiobis (2‐nitrobenzoic acid) (DNTB) revealed the locations of cystine‐containing peptides: four for ovine lactogenic hormone and three for human growth hormone. These cystine‐containing peptides were eluted, hydrolysed, and their amino acid compositions determined. By comparison of the analytical data with the known amino acid sequences around each half‐cystine residue and the known substrate specificity of pepsin, the positions of the disulfide bridges were unequivocally determined. The results confirm the disulfide linkages previously established by other methods. The scope and limitations of this procedure are discussed.
PREPARATION AND PROPERTIES OF HORSERADISH PEROXIDASE CROSS‐LINKED IN NONAQUEOUS MEDIA
Authors: Bartling Greg J. , Chattopadhyay Swaraj K. , Barker Charles W. , Forrester Lawrence J. , Brown Harry D.
Published: August 2010

Horseradish peroxidase (hydrogen peroxide oxidoreductase [1.11.1.7]) has been cross‐linked in methylene chloride using N,N'‐carbonyldiimidazole to produce a water insoluble preparation which retains enzymatic activity. Relative to native enzyme, which was treated with methylene chloride but not N,N'‐carbonyldiimidazole, the cross‐linked product displayed significant stability toward denaturation in aqueous mixtures of ethanol, methanol, and 1,4‐dioxane. The cross‐linked product showed a a marked stability toward thermal denaturation relative to the native protein. Applications of the catalyst in chemical reactors for the preparation of synthetic quinones are discussed.
DENATURATION OF PROTEINS. V.* N.M.R. STUDY OF THE ARGININE RESIDUES OF LYSOZYME
Authors: Bradbury J. H. , Norton Raymond S.
Published: August 2010

The heat denaturation of lysozyme has been studied by proton magnetic resonance spectroscopy at 220 MHz in water at pH 2.8. At 20°C a broad resonance is observed at 6.8δ due to the arginine NH2 resonances, which becomes a well defined triple resonance at 40°C, without any change in the rest of the spectrum. This sharpening of the arginine NH2 resonances is due to their increased mobilities and/or some normalisation of their chemical shifts. It is proposed that the surface structure of lysozyme is loosened at 40°C, without any change in the hydrophobic core and this is considered to be an intermediate phase in its heat denaturation. The heat denatured product at 80°C in D2O retains some noncovalent interactions, since further treatment with guanidine deuterochloride or mercaptoethanol causes sharpening of the aromatic region of the spectrum.
THE SOLID‐PHASE SYNTHESIS OF α‐MELANOTROPIN HYDRAZIDE
Authors: Hemmasi Bahram , Li Choh Hao
Published: August 2010

The solid‐phase synthesis of α‐melanotropin hydrazide, a new analog of α‐MSH, is described. Cleavage of the partially protected peptide from the solid support was accomplished with hydrazine in dimethylformamide. The protecting groups were removed with sodium in liquid ammonia and the product was purified by chromatography on carboxymethylcellulose to give a highly purified and melanotropically active tridecapeptide.
SYNTHESIS OF ANALOGS OF THE N‐TERMINAL EICOSAPEPTIDE SEQUENCE OF RIBONUCLEASE A
Authors: Borin G. , Marchiori F. , Moroder L. , Rocchi R. , Scoffone E.
Published: August 2010

For a better understanding of the role played by glut amine 11 either in the catalytic function of ribonuclease A or in the S‐peptide/S‐protein association process the following S‐peptide analogs have been synthesized: [Orn10,Leu11]‐ and [Orn10, Lys11]‐ S peptide.

The S‐protein activating ability of the two synthetic S‐peptide analogs was tested, before and after guanidination, by exploring their capacity to generate ribonuclease activity, against RNA as substrate, when recombined with S‐protein.
SEPARATION OF AMINO ACID MIXTURES ENRICHED IN STABLE ISOTOPES
Authors: Sogn John A. , Craig .Lyman C. , Gibbons William A.
Published: August 2010

A scheme is presented for the separation of protein acid hydrolyzates into the constituent amino acids on a scale up to approximately 10 g. The scheme was devised specifically for the purpose of separating relatively expensive, commercially available amino acid mixtures enriched in stable isotopes, so special attention is directed toward assuring quantitative recovery. The separation involves a countercurrent distribution and three ion‐exchange columns
THREE‐DIMENSIONAL ARCHITECTURE OF MONODISPERSE β‐BRANCHED LINEAR HOMO‐OLIGOPEPTIDES
Authors: Toniolo C. , Bonora G. M. , Fontana A.
Published: August 2010

The conformations in solution of a series of monodisperse L‐valine oligomers having the general formula BOC(L‐Val)nOMe* (n = 2–7) were investigated using polarimetry, UV absorption, and CD. We examined these oligopeptides in TFE, HFIP, HFA, and mixed fluoroalcoholic‐water media, and compared the results with those obtained in the analogous L‐isoleucine series, which in part have been previously reported. The β‐associated structure stands out clearly at the heptamer in the two β‐branched linear homo‐oligopeptide series in TFE. In HFIP and HFA, however, the oligomers exist essentially in an unordered conformation. Also, we demonstrated that addition of water to solutions of these oligopeptides in the fluoroalcohols forces the higher oligomers to assume β‐type associated structures. The aggregates could be disrupted by dilution or increasing temperature.
SYNTHESIS AND CHARGE‐TRANSFER PROPERTIES OF TWO ACTH ANALOGUES CONTAINING PENTAMETHYLPHENYLALANINE IN POSITION 9
Authors: van Nispen J. W. , Tesser G. I.
Published: August 2010

In order to investigate the possible role of the Trp residue in ACTH as a charge‐transfer donor in the activation of ACTH receptors, two ACTH analogues (β‐corticotrophins (1–24) with L‐Ser1 and D‐Ser1, respectively) containing pentamethylphenylalanine instead of Trp have been synthesized. In these syntheses a new, alkaline‐labile, aminoprotecting group, the methylsulphonylethyloxycarbonyl group, was employed. The association constants of ACTH (1–24) and [Pmp9]‐ACTH (1–24)* with the watersoluble acceptor paraquat, were nearly equal.
ISOLATION AND CHARACTERIZATION OF THE CYANOGEN BROMIDE FRAGMENTS OF LOBSTER ARGININE KINASE (HOMARUS VULGARIS)
Authors: Debuire Brigitte , Han Kia‐Ki , Dautrevaux Michel , Biserte Gerard
Published: August 2010

Arginine kinase was aminoethylated in order to block the five free thiol groups on the native enzyme, and then submitted to BrCN cleavage. The BrCN resulting peptides were soluble in propionic acid (10%) and subsequently submitted to gel‐filtration. The large polypeptide subfractions were citraconylated and resubmitted to different gelchromatographies, whereas the short peptide subfractions were submitted to preparative paper electrochromatographies. Eight peptides of 2, 11, 17, 25, 61, 82, 86 and 132 amino acid residues were isolated, one of which is the overlapping of two peptides. The amino acid composition and the end group of all the isolated peptides were established. The short peptides (2, 11 and 17 residues) were sequenced. All peptides possess homoserine at C‐terminal position because one methionyl residue is situated at the C‐terminal position in the native protein. The polypeptide with 132 residues possessed N‐acetylated residue at N‐terminal position; therefore this polypeptide is located at the N‐terminal position in the protein. The sum and account of each amino acid of the seven isolated peptides were compared to those of the intact protein: the sum of the seven peptides is 331 amino acid residues, whereas the whole protein contains 342 residues. The molecular weight of arginine kinase is revised and calculated on the basis of the present results (37, 687).
DIGESTION OF INSULIN DERIVATIVES WITH SUBTILISIN: A KINETIC STUDY
Authors: Ronca G. , Montali U. , Lucacchini A. , Ronca‐Testoni S. , Rossi C. A.
Published: August 2010

Native, denatured, performic acid‐oxidized or S‐sulfo insulin and S‐sulfo or performic acid‐oxidized A‐ and B‐chains were digested with subtilisin type Carlsberg. The proteolysis was followed by measuring the uptake of alkali through autotitration. The kinetic study shows the existence of 2 first‐order reaction classes which differ markedly in rate constant. The number of bonds split with fast and with slow reactions has been calculated. Only one of a total of 12 cleavable bonds in native insulin is opened by fast reaction. In the denatured protein the number of bonds split by the fast reaction increases to 4 and in the oxidized and S‐sulfo protein 3 bonds are cleaved, while the slow cleavable bonds number 8 and 7, respectively. The kinetic study of the proteolysis of S‐sulfo A‐chain and of oxidized or S‐sulfo B‐chain shows that two bonds are split in A‐chain with the fast and slow reactions, while in B‐chain only one of the six cleavable bonds is susceptible to fast attack.
CARBAMYLATION OF ALKALINE MESENTERICOPEPTIDASE
Authors: Genov Nicolay , Vorotyntseva Tatiana , Antonov Vladimir
Published: August 2010

The effects of carbamylation with potassium cyanate, and methylation with methyl p‐nitrobenzene sulphonate on the mesentericopeptidase activity are studied. The treatment with potassium cyanate causes the enzyme to lose its activity towards ester substrates and casein. The specific reagent N‐trans‐cinnamoylimidazole does not acylate the active site in the carbamylated enzyme. The pH dependence of the rate of inactivation indicates that an ionizing group of pK = 7.3, probably the protonated imidazole group of the active site histidine, is involved in the reaction. The competitive inhibitor boric acid protects mesentericopeptidase against inactivation with potassium cyanate. These results suggest that the active site residues are modified in the unprotected enzyme. Sixty per cent of the enzyme activity toward N‐acetyl‐L‐tyrosine ethyl ester was restored after treatment of the carbamylated mesentericopeptidase with 1 M hydroxylamine hydrochloride. Circular dichroism spectra show that the carbamylation does not change markedly the native protein conformation.

Methyl p‐nitrobenzene sulphonate does not methylate the active site histidine.
CRYSTAL AND MOLECULAR STRUCTURE OF A 4‐OXIMINO‐5‐IMINO‐PYRAZOLINE ACTIVE ESTER
Authors: Guarneri M. , Menegatti E. , Benassi C. A. , Sacerdoti M. , Gilli G.
Published: August 2010

The crystal structure of an active 4‐oximino‐5‐imino‐pyrazoline ester has been determined by single‐crystal X‐ray diffraction methods. The possible reasons for its high reactivity towards nucleophilic reagents are briefly discussed.
MECHANISM OF GLUTATHIONE REGENERATION OF REDUCED PANCREATIC RIBONUCLEASE A
Authors: Schaffer Stephen W.
Published: August 2010

A comparative study was made of the kinetics of glutathione regeneration of reduced pancreatic ribonuclease A, as determined by circular dichroism, sulfhydryl oxidation and the kinetics of reactivation. Four sulfhydryls were reoxidized prior to any large circular dichroic changes or recovery of enzymatic activity. The helical and β segments in ribonuclease were shown to reform at approximately the same rate. The results are discussed in terms of a regeneration mechanism for ribonuclease involving (1) nucleation, (2) polypeptide backbone refolding, and (3) reshuffling of incorrectly paired disulfide bonds.
SEQUENTIAL POLYPEPTIDES.
Authors: Bell John R. , Jones John H. , Webb Terence C.
Published: August 2010

A general route has been devised for the synthesis of sequential polypeptide collagen models of formula H‐(X‐Gly‐Pro)n‐OH where X is a trifunctional amino acid residue. Application of this route to the cases X = Tyr, Orn, Lys, Glu and Ser is described.
THE METHYLSULFONYLETHYLOXYCARBONYL GROUP, A NEW AND VERSATILE AMINO PROTECTIVE FUNCTION
Authors: Tesser G. I. , Balvert‐Geers I. C.
Published: August 2010

A new amino protecting group, the methylsulfonylethyloxycarbonyl (Msc) group, is described which combines well with other familiar groups (benzyloxycarbonyl, t‐butyloxycarbonyl) in peptide syntheses. Its main characteristics are an extreme acid stability, a high base lability and a high polarity which enhances solubility in polar solvents including water. The group resists catalytic hydrogenolysis but does not poison the catalyst. It has good crystallizing properties. Application in peptide synthesis is exemplified in the synthesis of Msc‐Phe‐Arg‐Trp‐Gly‐OMe.HCl. Deprotection of the masked tetrapeptide was accomplished within 5 sec with a 1.0 N solution of base (OH‐and OCH3‐). A reaction scheme for the cleavage of the group is suggested.
THEORY OF REVERSIBLE DENATURATION OF GLOBULAR PROTEINS
Authors: Gö Nobuhiro
Published: August 2010

A theoretical method is developed by which the character of the process of protein denaturation (e.g., whether or not it is of the all‐or‐none type) can be discussed in terms of conformation of native proteins and the forces stabilizing it. An important role is played by a quantity S(H): entropy of a protein molecule in solution in the conformational states with a given value of enthalpy H. It is demonstrated that the all‐or‐none type denaturation of proteins is a rather direct consequence of the globularity and specificity of the native conformations. Denaturations with significant intermediate states are discussed. Denaturations induced by added denaturants are also discussed.
SYNTHESIS OF THE SEQUENTIAL POLYPEPTIDE POLY[CYS(ACM)‐SER‐PHE‐GLU‐GLU] AS A MODEL FOR HYDROLYTIC ENZYMES
Authors: Trudelle Y. , Birr Christian
Published: August 2010

To construct a possible model of hydrolytic enzymes, the sequential polypeptide H[Cys(Acm)‐Ser‐Phe‐Glu‐Glu]nOH, n = 3–110, was prepared by polycondensation of H‐Cys(Acm)‐Ser(But)‐Phe‐Glu(OBut)‐Glu(OBut)‐O Su/1‐hydroxybenzotriazole. In a solid state the polypeptide material showed β‐conformation both before and after cleavage of t‐butyl protecting groups.

The pentapeptide unit was synthetized by the Merrifield method utilizing modifications as follows: Gel phase synthesis on < 0.5% cross‐linked copolystyrene (quasi dissolved state). Centrifugal reactor. Ddz‐amino acids, deprotected by 5% trifluoroacetic acid/dichloromethane/ 15 min. 3‐Nitrophthalic anhydride to suppress formation of false sequences. Continuous photometric control of the completion of all operations during synthesis and transesterification, yielding Ddz‐Cys(Acm)‐Ser(But)‐Phe‐Glu‐(OBut)‐Glu(OBut)‐OMe (0.827 g; 53%, m.p. 180–182°).
A KINETIC STUDY OF THE HYDROLYSIS OF N‐ACETYL DEHYDROALANINE METHYL ESTER
Authors: Snow John T. , Finley John W. , Friedman Mendel
Published: August 2010

Hydrolysis rates of N‐acetyl dehydroalanine methyl ester (methyl 2‐acetamidoacrylate) and related model compounds were measured in aqueous, organic and mixed aqueous media. Adding dimethyl sulfoxide (DMSO) to water, retarded hydrolysis of the ester by a factor of 2 to 500, depending on the pH of the medium and concentration of DMSO. Ethanol also slowed hydrolysis, but the effect was not so pronounced. Related studies show that the acetamido group C‐N bond of sodium 2‐acetamido‐acrylate is hydrolyzed only about 1/130 as fast as the ester group C‐O bond. Aqueous dimethyl sulfoxide should be a useful medium for synthesis of peptide, amino acid and protein derivatives of N‐acetyl dehydroalanine methyl ester.
THE PRIMARY STRUCTURE OF OVINE INTERSTITIAL CELL STIMULATING HORMONE IV: DISULFIDE BRIDGES OF THE β SUBUNIT
Authors: Chung David , Sairam M. R. , Li Choh Hao
Published: August 2010

The disulfide linkage of the 12 half‐cystine residues in the β subunit of ovine interstitial cell stimulating hormone has been investigated by enzymic and partial acid hydrolysis of the intact molecule. Results indicate that the disulfide bridges are formed by residues 9–38, 23–72, 26–110, 34–90, 57–88, and 93–100.
AN IMPROVED SYNTHESIS OF tert‐ BUTYLOXYCARBONYL‐L‐HISTIDINE
Authors: van Batenburg O. D. , Kerling K. E. T.
Published: August 2010

In our investigations on the effect of replacement of histidine by homohistidine (I) on the biological activity of some peptide‐hormones, relatively large quantities of Boc‐ homohistidine were required. Homohistidine being difficult to synthesize, it was essential to find an effective way of introducing the Boc‐group. In the past, many syntheses of Boc‐histidine were reported (2–6), none of which proved to be quite satisfactory. However, by modifying the procedure of Flouret et al. (6) a convenient method resulting in a high yield of Boc‐histidine and Boc‐homohistidine was found.
AMINO ACIDS AND PEPTIDES. XLII. SYNTHESIS OF AN OCTAPEPTIDE SEQUENCE (A20‐A27) OF RUBREDOXIN
Authors: Weinstein Boris , Cook Ronald M. , Heffernan John T.
Published: August 2010

A protected octapeptide corresponding to a section found in the first half of the protein chain of rubredoxin has been prepared by standard peptide methods. Alternative approaches to this fragment are discussed in some detail. This work completes the series of subunits necessary to synthesize the molecule.
ISOLATION OF A TRYPSIN‐LIKE ENZYME FROM. STREPTOMYCES PAROMOMYCINUS (PAROMOTRYPSIN) BY AFFINITY ADSORPTION THROUGH KUNITZ INHIBITOR‐SEPHAROSE
Authors: Chauvet Jacqueline , Dostal Jean‐Pierre , Acher Roger
Published: August 2010

A trypsin‐like enzyme has been isolated from the filtrate of a Streptomyces rimosus forma paromomycinus culture. Purification involves acetone fractionated precipitation, ultrafiltration on a Diaflo UM 10 membrane and affinity adsorption on to Kunitz pancreatic trypsin inhibitor linked to Sepharose. The trypsin‐like enzyme (paromotrypsin) appears homogeneous by zone electrophoresis on gelatinized cellulose acetate. Specific activity toward Tos‐Arg‐OMe, calculated from amino acid analysis, is about 220 u mg‐1. The overall yield in activity is about 30%.

The molecular weight of the trypsin‐like enzyme, determined by gel filtration, is around 22,000–25,000 daltons. Electrophoretic migration on cellulose acetate strips indicates an isoelectric point around 8. Amino acid composition has been determined; the protein comprises about 210 residues on the basis of a single histidine residue per molecule.

Paromotrypsin is unstable in acidic medium and is not stabilized by calcium ions. Enzymic activity towards Bz‐Arg‐OEt is not increased by the addition of calcium ion in contrast to the activating effect observed on bovine trypsin.

Paromotrypsin is inhibited by TLCK and NPGB; it interacts with naturally occurring bovine trypsin inhibitors such as soya bean and Kunitz pancreatic inhibitors, but not with chicken ovomucoid. Proteolytic specificity, examined by hydrolysis of oxidized Kunitz pancreatic inhibitor and characterization of resulting peptides, seems similar to that of bovine trypsin.
RELATIVE REACTIVITIES OF SULFHYDRYL GROUPS WITH N‐ACETYL DEHYDROALANINE AND N‐ACETYL DEHYDROALANINE METHYL ESTER
Authors: Snow John T. , Finley John W. , Friedman Mendel
Published: August 2010

The reaction rates in aqueous solutions of aminothiols, thiols, and other compounds with N‐acetyl dehydroalanine and its methyl ester (2‐acetamidoacrylic acid and methyl 2‐acetamidoacrylate) were studied as a function of the structure of the thiol compound in aqueous solutions. Correction of the observed second‐order rate constants to identical thiol anion concentration gave a series of computed rate constants whose logarithms showed a linear dependence on the pK's of the thiol group in similar steric environments.

Comparison of the addition rates of penicillamine to N‐acetyl dehydroalanine and its methyl ester showed the methyl ester to react approximately 11,400 times faster than the acid. Addition rates for thiol acids and aromatic and heterocyclic thiols were also compared; each showed sluggish reactivity with dehydroalanine, but each reacted readily with methyl dehydroalanine. The kinetic data were applied in developing a method for preparing lanthionine in high yield.
STUDIES ON TRYPSIN INHIBITORS
Authors: Guggi Augusto , Tomatis Roberto , Salvadori Severo , Rocchi Raniero
Published: August 2010

Synthesis is described of the partially protected nonapeptide tert‐butyloxycarbonyl‐valylleucylisoleucylglutaminyl ‐ Nε ‐ trifluoroacetyllsylserylglycylprolyl‐ S‐acetamido ‐ methylcysteine corresponding to positions 44–52 of the amino acid sequence of porcine pancreatic secretory trypsin inhibitor II. The hexapeptide free base glutaminyl‐Nε ‐ trifluoroacetyllysylserylglycylprolyl‐S‐acetamidomethylcysteine, prepared by two alternative routes, was acylated by the azide procedure, with the tripeptide tert‐butyloxycarbonylvalylleucylisoleucine hydrazide. The stereochemical homogeneity of the resulting nonapeptide was assessed, after partial deprotection by treatment with aqueous 90% trifluoroacetic acid, by digestion with papain and aminopeptidase M followed by quantitative amino acid analysis.
THE EFFECT OF CALCIUM CHLORIDE ON THE ACTIVITY AND INHIBITION OF BACTERIAL COLLAGENASE
Authors: Head David L. , Yankeelov John A.
Published: August 2010

The enzymatic behavior and inhibition patterns of collagenase of Clostridium histolyticum in the presence of 0.5 M and 3.4 mM CaCl2 have been examined viscosimetrically. The more concentrated salt was found to enhance the rate of digestion of calfskin collagen when either measured viscosimetrically or colorimetrically by trinitrobenzenesulfonate. However, the rate of digestion of calfskin gelatin is unaffected by 0.5 M CaCl2 as determined colorimetrically.

Calcium chloride also proved to have a marked effect on the inhibitory behavior of a series of imidazole compounds. Histidine (10 mM) is about three‐fold more effective as an inhibitor in 0.5 M CaCl2 than in 3.4 mM CaCl2, whereas a reverse effect is true for histamine. Imidazolylpropionate (10 mM) was only weakly inhibitory (16%) in 0.5 M CaCl2 and not at all in 3.4 mM CaCl2. Inhibition by 10 mM imidazole was not detectable. These observations may be useful in the design of inhibitors for tissue collagenases which share a number of common characteristics with the bacterial enzyme.
PURIFICATION OF A LYSINONORLEUCINE CROSS‐LINKED PEPTIDE FRACTION FROM PORCINE AORTA ELASTIN
Authors: Davril Monique , Han Kia‐Ki
Published: August 2010

Highly purified elastin from porcine aorta was submitted to elastase digestion. The enzymic products were subjected to gel filtration on Sephadex G 25. The excluded fraction was then submitted to thermolysin digestion and gel filtration. The excluded fraction was submitted to partial acid hydrolysis and gel filtration. Several sub‐fractions were obtained. The F3 subfraction containing cross‐linking agents (desmosines and lysinonorleucine) was finally subjected to ion exchange chromatography. A highly enriched peptide fraction containing lysinonorleucine was obtained and then purified by preparative electrophoresis. The ratio of enrichment passed from 2 residues of lysinonorleucine (expressed as lysine) from starting material (elastin) to 178 out of 1,000 residues in the final step. In this peptide fraction, if we express in molar ratio and consider the amount of lysinonorleucine is one residue, the following amino‐acid composition is Pro:3, Gly:1, Ala:2, LNL:1, Lys:2. No traces of desmosines are detected. The role of lysinonorleucine in bridging functions in elastin is discussed.
UNUSUAL BEHAVIOUR OF A PROTEIN: REVERSIBLE QUANTITATIVE PRECIPITATION OF STAPHYLOCOCCAL DELTA‐HAEMOLYSIN BY LOW CONCENTRATIONS OF SOME ORGANIC SOLVENTS
Authors: Heatley N. G.
Published: August 2010

Staphylococcal delta‐haemolysin is precipitated from watery solutions by low concentrations of chloroform. The effect on this precipitation of pH, kind and concentration of salts, and concentration of, and time of exposure to, chloroform have been investigated. Some but not all of the other solvents tested cause a similar precipitation. The haemolytic activity is not destroyed and under appropriate conditions precipitation is quantitative.

The dry lysin will take up nearly double its weight of chloroform when exposed to the vapour. Some is bound strongly.
SEARCH FOR LOW‐ENERGY CONFORMATIONS OF A NEUROTOXIC PROTEIN BY MEANS OF PREDICTIVE RULES, TESTS FOR HARD‐SPHERE OVERLAPS, AND ENERGY MINIMIZATION*
Authors: Gabel Detlef , Rasse Daniel , Scheraga Harold A.
Published: August 2010

A method to obtain models for the three‐dimensional structure of the neurotoxin α from Naja nigricollis from its amino acid sequence is explored here. Empirical predictive rules were used to estimate the positions of helices, extended structures and bends; advantage was taken of the availability of 14 homologous sequences for the neurotoxins in an attempt to increase the reliability of these predictions. Unassigned residues were allowed to take up several possible conformations determined from the frequencies of occurrence of each type of conformation of that residue in x‐ray structures of many proteins. The conformational space of the molecule was explored initially by testing for hard‐sphere overlaps and approximate closure of disulfide loops with the aid of a computer; this procedure yielded a limited number of conformations, whose conformational energies were then determined and minimized by optimizing the backbone and side‐chain dihedral angles of each residue. Five compact conformations with low energy were found for this neurotoxin. The procedure used here provides an illustration as to how empirical protein algorithms may be used to limit the conformational space, in which energy minimization has to be carried out.
THE PRIMARY STRUCTURE OF MUSKRAT PANCREATIC RIBONUCLEASE
Authors: van Dijk Henk , Sloots Boele , van den Berg Annelies , Gaastra Wim , Beintema Jaap J.
Published: August 2010

Pancreatic ribonuclease from muskrat (Ondatra zibethica) was isolated and its amino acid sequence was determined from tryptic digests of the performic acid‐oxidized and the reduced and aminoethylated enzyme. The peptides have been positioned in the sequence by homology with other ribonucleases. This could be done unambiguously for all peptides except Arg‐Arg (tentative position 32–33) and Ser‐Arg (tentative position 75–76). The amino acid sequences of the peptides were determined by the dansyl‐Edman method, with the exception of residues 23–25 and 99–102, which were positioned by homology.

The enzyme differs in 38 positions from the enzyme from rat and in 31–42 positions from other mammalian pancreatic ribonucleases, while rat ribonuclease differs at 44–52 positions from the other enzymes. These data point to a common ancestry of the enzymes from muskrat and rat and an increased evolution rate of rat ribonuclease after divergence of the ancestors of both species.

Muskrat ribonuclease contains no carbohydrate, although the enzyme possesses a recognition site for carbohydrate attachment in the sequence Asn‐ Val‐Thr (62–64).
PROTON MAGNETIC RELAXATION DISPERSION IN HUMAN FLUOROMETHAEMOGLOBIN SOLUTIONS
Authors: Lahajnar G. , Benko B. , Rutar V. , Zupančič I.
Published: August 2010

The solvent proton spin‐lattice relaxation time of high spin Fe3+(S=5/2) human A fluoromethaemoglobin aqueous solutions was measured at 14 Larmor frequencies in the range from 2.2 to 96 MHz. The observed paramagnetic relaxation rates are analysed in terms of the Solomon‐Bloembergen theory, with the g‐tensor value of 2 based on the consideration of the protein tertiary structure. From the H2O (pH 6) haemoprotein solution relaxation data,τ c = (9.3±0.3) × 10‐10sec. If the total relaxation rates are corrected for the “outer‐sphere” paramagnetic contribution, τc = (6.5±0.4) × 10‐10sec. The latter correction is obtained from the p.m.r. of the non‐exchangeable aliphatic protons of C2H4(OD)2 added to the D2O‐solution of fluoromethaemoglobin. Assuming that single proton transfer is taking place through the protein channel along the axis normal to the haem (g = 2), the proton “binding” site is at a distance of 3.93 to 3.98 Å from the haem Fe3+ion.
STRUCTURE‐ACTIVITY STUDIES ON MAMMALIAN TISSUE LYTIC ENZYMES: CHEMICAL CHARACTERIZATION AND SUBSTRATE SPECIFICITY OF RAT KIDNEY NUCLEAR LYSOZYME*
Authors: Raghunathan R. , Shantoo Gurnani
Published: August 2010

Studies on the structure and substrate specificity of purified rat kidney nuclear (RKN) lysozyme are reported.

The carboxyl and amino terminal residues of RKN‐lysozyme were found to be leucine and alanine respectively. The amino acid composition indicated similarities and differences as compared with that of hen egg white (HEW) lysozyme. There were alterations in the nine amino acid residues, Lys, His, Arg, Asp, Glu, Pro, 1/2 Cys, Tyr and Trp. The other nine residues were present in identical proportions to those of HEW‐lysozyme. The decrease in the arginine and aspartic acid residues was found to be compensated by the increase in the number of lysine, histidine and glutamic acid residues. The overall ratio of the acidic to basic amino acids has thus been conserved in the mammalian enzyme. In addition, RKN‐lysozyme contained decreased numbers of Trp, Tyr and 1/2 Cys, and increased numbers of proline residues as found in HEW‐lysozyme. RKN‐lysozyme did not cross react with heterologous antibodies produced against HEW‐lysozyme, and vice versa.

RKN‐lysozyme showed distinct specificity towards the lysis of M. luteus. Against this substrate, it was three times more efficient than HEW‐lysozyme. It also cleaved E. coli B, but its efficiency was half as much as with M. luteus. However, it cleaved P. septica and B. subtilis at a rate similar to HEW‐lysozyme under identical conditions.
THE PH DEPENDENCE OF BINDING OF α, α‘‐DIBROMO‐P‐XYLENESULFONIC ACID TO LYSOZYME
Authors: Chung Ane C. , Day Richard A.
Published: August 2010

The chemical modification of lysozyme (I) has been accomplished with α,α'‐dibromo‐p‐xylenesulfonic acid (DBX) at five different pH values. I was alkylated by DBX at room temperature (28°C) with decrease in enzyme activity. The rate of inactivation depended upon the pH at which alkylation was carried out. The highest rate was seen at alkaline pH values; the lowest at more acidic pH values. Amino acid analyses showed that two lysines and two tryptophan residues had been modified at pH 9; two lysines, one tryptophan and one methionine had reacted at pH 8. A histidine residue was bound at pH 6.5 together with a tryptophan residue. At the lower pH values (2.7, 4.5, 6.5), alkylation occurred with a single tryptophan residue each. Fluorescence and CD data both ruled out the participation of tryptophans 62 or 108. Labeling experiments showed that two residues of DBX‐35S were bound per molecule of I at both pH 9 and pH 8; one residue of DBX was bound per molecule of I at the other pH values. Sedimentation coefficients were characteristic of native lysozyme. The stoichiometry of binding and residue modification indicated that intra‐molecular cross links were established. The pH dependence of the cross‐linking provides means to measure several allowed intramolecular distances. The results presented here are consistent with the existence of side chain motion in lysozyme.
POLYPEPTIDE MODELS OF COLLAGEN: SYNTHESIS OF (PRO‐PRO‐ALA)n AND (PRO‐PRO‐VAL)n
Authors: Rapaka Rao S. , Bhatnagar Rajendra S.
Published: August 2010

The synthesis of two collagen models (Pro‐Pro‐Ala)n and (Pro‐Pro‐Val)n is reported. Preliminary examination suggests that (Pro‐Pro‐Ala)n may exhibit some properties of collagen‐like polypeptides whereas (Pro‐Pro‐Val)n does not have a collagen‐like character.
DISSOCIATION AND DENATURATION BEHAVIOUR OF SESAME α‐GLOBULIN IN SODIUM DODECYL SULPHATE SOLUTION*
Authors: Prakash V. , Nandi P. K.
Published: August 2010

The effect of anionic detergent, sodium dodecyl sulphate, on the major protein, α‐globulin of sesame seed (Sesamum indicum L.) has been investigated by gel filtration, sedimentation velocity, viscosity, optical rotation, difference spectra and fluorescence measurements. The detergent causes dissociation of the protein first and then denaturation. In the detergent concentration range of 1.75–4.0 times 10‐3M four components are observed in the ultracentrifuge. The specific rotation of the protein increases with the detergent concentration above 2.5 times 10‐3M and shows a cooperative transition between 3–8 times 10‐3M detergent suggesting conformational change; above 8 times 10‐3M detergent the value of –[α] does not change. The reduced viscosity ηred however, increases above 2.5 times 10‐3M detergent and does not attain a plateau value. The difference spectrum of the protein indicates that both tryptophan and tyrosine groups have been affected by the detergent. The fluorescence intensity decreases and the maxima shifts towards red in the detergent solution resulting in an ‘isoemissive point’ at 355 nm. The double difference spectra in sucrose‐detergent protein system show that below 5.0 times 10‐3M detergent, the difference absorption and fluorescence spectrum result from the binding of the detergent near the chromophoric groups and are not due to conformational change. Binding studies by equilibrium dialysis indicate the presence of 50 binding sites in the protein and a binding constant of 3.0 times 103.
THE RECONSTRUCTION OF A FRAGMENT OF PRIMORDIAL GENETIC INFORMATION FROM MODERN PROTEINS: PGI‐F1 (AHAP)
Authors: Bauer Klausdieter
Published: August 2010

In a continuation of earlier studies the connection between a reconstructed ancestral histone IV peptide and various sequences from non‐histone proteins was investigated. This peptide, AHAP, was found to be related to partial peptides from the human encephalitogenic protein, immunoglobulin L‐chains, fibrinopeptide A, glyceraldehyde‐3‐phosphate‐dehydrogenase, TMV coat protein and several other proteins and protein families; for comparison, nodal sequences were employed wherever possible.

The widespread occurrence of genetic information expressed in AHAP caused us to rename the peptide PGI‐F1 (primordial genetic information‐fragment 1) since this peptide is apparently part of a very primitive and ancient genetic information, and may be called “protogene”.
STUDIES ON POLYPEPTIDES. XVII.
Authors: Voskuyl‐Holtkamp Ingrid , Schattenkerk Cecile , Havinga E.
Published: August 2010

Sequences [5–17] and [1–17] of rat pancreatic ribonuclease have been synthesized via convergent fragment coupling. The rat peptides combine with bovine S‐protein and yield fully active ribonuclease S' analogues.
SYNTHESIS AND N.M.R. SPECTRAL ANALYSIS OF LEUCINE ‐dγ
Authors: Sogn J. A. , Gibbons W. A. , Wolff S.
Published: August 2010

A simple reaction scheme for the synthesis of leucine totally deuterated in the γ position is described. The n.m.r. spectral properties of this derivative are analyzed and its potential usefulness as a probe of leucine sidechain stereochemistry in peptides is discussed.
STUDIES ON A PROTAMINE (GALLINE) FROM FOWL SPERM.
Authors: Nakano Minoru , Tobita Tohru , Ando Toshio
Published: August 2010

Galline, a protamine of domestic fowl, was obtained by two preparation procedures from the semen of a strain of White Plymouth Rock and submitted to fractionation by column chromatography on Bio‐Gel CM‐30. In the first procedure the specimen prepared from sperm heads was purified by the use of distilled water and dilute acetic acid and fractionated into almost eight fractions (G‐I‐G‐VIII) in the same way as the specimen from a strain of New Hampshire (1,2). No difference could be found between galline specimens from the two different strains based on the amino acid and terminal analyses of each fraction. The specimen of galline from sperm heads purified with 1% citric acid (the second procedure) was composed of only one component, which was isolated as a single peak. The smaller fractions, G‐I‐G‐VII, were found to be derived from G‐VIII by the action of trypsin‐like protease contained in the extract of sperm heads with 1% citric acid. This enzyme seems to originate in the acrosome of fowl spermatozoa. Consequently, it is concluded that intact galline is composed of only one molecular species and its total amino acid sequence is represented by the completed formula of G‐VIII as shown in the preceding paper (4).
APPLICATION OF THE ONE‐DIMENSIONAL ISING MODEL TO THE SECONDARY STRUCTURES IN GLOBULAR PROTEINS.
Authors: Ananthanarayanan V. S. , Bandekar Jagdeesh
Published: August 2010

An attempt has been made to predict the β‐regions in 16 globular proteins by applying the one‐dimensional Ising model theory of Lifson & Roig (8). The parameters for the theory have been derived from the statistical data on globular proteins given by Chou & Fasman (5). Comparison of our results with the data available from the X‐ray crystallographic studies indicates a prediction accuracy which is comparable to those of several other methods, especially in view of the limitations in our method for considering the other secondary structures. It is pointed out that not considering the long‐range interactions in our and other methods based on short‐range interactions would make these methods incomplete and incapable of being uniformly applicable to all proteins.
CYCLIC PEPTIDES
Authors: Lee Sannamu , Izumiya Nobuo
Published: August 2010

Synthesis of a cyclohexadepsipeptide corresponding to the sequence of protodestruxin from linear hexapeptides was attempted through five different routes in a conventional method, and three routes afforded the same cyclopeptide. Biological and physicochemical properties of the synthetic peptide were identical to those of natural protodestruxin. Differences in the yields of the cyclization were explained through the assumed conformations of the linear hexapeptides.
CHEMICAL STUDIES ON A HAMSTER SUBLINGUAL GLYCOPROTEIN
Authors: Downs Fred , Herp Anthony
Published: August 2010

A secretory glycoprotein was isolated from the hamster sublingual gland. It contains 65% carbohydrates, the remainder being protein. The principal type of sialic acid was identified as N‐acetylneuraminic acid with about 1/4 of the molecules O‐acetylated. The hexosamine occurs mainly as N‐acetylgalactosamine; other sugars present are galactose and fucose. The carbohydrate side chains are linked to the protein core by an O‐glycosyl linkage between seryl and threonyl residues and N‐acetylgalactosamine. The glycoprotein has an apparent molecular weight of 330,000. The sialoglycoprotein may act as a biological antifreeze. Relevant differences in the chemical composition of the secretory glycoproteins of the sublingual and submaxillary salivary glands of this species are briefly discussed.
CONFORMATIONAL ANALYSIS OF CYCLO (L‐CYSTINE
Authors: Mitra Alok K. , Chandrasekaran R.
Published: August 2010

Conformational analysis of cyclo(L‐cystine) shows that the diketopiperazine ring has to exist only in the boat form. With this geometry, the molecule can adopt two distinct forms differing mainly in the chirality of the disulphide bridge. In both the P‐ and M‐models, corresponding to dihedral angles of nearly + 90° and —90° respectively about the S‐S bond, the molecule displays an approximate two‐fold symmetry. According to our semi‐empirical energy calculations, the minimum energy of the M‐model is —9.2 kcal/mol, only 0.3 kcal/mol lower than that of the P‐model. Because the difference between the two minima is so small, neither form is clearly superior to the other. However, the number of low energy conformations of the M‐model in the allowed conformational space is significantly larger than that of the P‐model by a ratio of 3 to 1, and therefore the former is likely to be thermodynamically favoured.
SOLID PHASE SYNTHESIS AND SOME HORMONAL ACTIVITIES OF 1‐DEAMINO‐4‐L‐VALINE‐8‐D‐HOMOLYSINE‐AND 1‐DEAMINO‐4‐L‐VALINE‐8‐D‐HOMOARGININE‐VASOPRESSIN
Authors: Lindeberg Gunnar , Karlsson Sune M. , Melin Per
Published: August 2010

1‐Deamino‐4‐L‐valine‐8‐DL‐homolysine‐vasopressin and protected 1‐deamino‐4‐L‐valine‐8‐D‐lysine‐vasopressin were synthesized by the solid phase method and were then converted into the title compounds (dVDHLVP and dVDHAVP) by tryptic digestion and e‐guanidination, respectively. The new hormone analogues exhibit only moderate antidiuretic potency, dVDHLVP 21 units/mg and dVDHA VP 31 units/mg, but since they are essentially devoid of pressor activity (0.01 units/mg) the A/P ratios are very high. In fact, dVDHLVP is the most specific antidiuretic agent in the lysine series known so far.
PREDICTED SECONDARY STRUCTURE OF SNAKE VENOM TOXINS FROM THEIR PRIMARY STRUCTURES
Authors: Eterovic Vesna A. , Ferchmin P.A.
Published: August 2010

We have predicted the secondary structure of 38 snake venom toxins using the method of Chou and Fasman. Our predictions indicate that β‐chain and random coil structures predominate in these proteins. The conformations of long neurotoxins, short neurotoxins and cytotoxins are less similar than previously believed Cytotoxins contain 40–50% of β‐structure and they form a notably homogeneous group. Short neurotoxins contain less β‐structure (13–30%) and more random coil than cytotoxins, and they also form a more heterogeneous group in terms of secondary structure. The characteristics of long neurotoxins are intermediate to the above mentioned groups. Experimental evidence supporting these propositions is discussed.
SYMMETRY PATTERNS IN TRYPSINOGEN
Authors: Erhan Semih , Greller Larry D. , Rasco Barbara
Published: August 2010

When the primary structure of bovine trypsinogen is searched for the existence of regularities, according to Greller & Erhan (1974), one finds eight pairs of peptides, arranged in a symmetrical pattern along the molecule. These peptides cover 49% of the length of the molecule–112 of the 227 amino acids – and each pair folds in a similar way. This observation is in agreement with the observation that “Trypsin folds into two halves, each of which contains a pseudo‐cylindrical arrangement of hydrogen bonds…”, Stroud et al. (1971). Thus the above mentioned method is capable not only of detecting regularities along the primary structure but also of predicting the folding of a protein.