bluuebunny/crossref_metadata_2025_split huggingface dataset:
STUDIES ON TRYPSIN INHIBITORS:
Authors: Tomatis Roberto , Guggi Augusto , Salvadori Severo , Rocchi Raniero 
Published: August 2010

The synthesis, by fragment condensation, of protected peptides related to the N‐terminal (positions 1–14) and C‐terminal (positions 36–52) portions of the amino acid sequence of porcine pancreatic secretory trypsin inhibitor II (Kazal type) is described.The α‐carboxyl function of the lysyl residue in position 14 was used as the free acid, or protected by the tert‐butyloxycarbonylhydrazide.Two different synthetic pathways were used in the preparation of the 36–52 sequence of the inhibitor. The identity and purity of the synthesized peptide derivatives were established by amino acid analysis of acid hydrolysates, optical rotation and thin layer chromatography in two solvent systems. The final products were also evaluated, after partial deprotection with anhydrous hydrogen fluoride or aqueous 90% trifluoroacetic acid, by paper electrophoresis at different pH values and enzymic digestion with papain and aminopeptidase M followed by quantitative amino acid analysis.
SYNTHESIS AND BIOLOGICAL ACTIVITIES OF TWO ACTH‐ANALOGUES CONTAINING L‐NORARGININE IN POSITION 8
Authors: VAN Nispen J.W. , Tesser G.I. , Nivard R.J.F. 
Published: August 2010

Two new ACTH‐analogues, an octadecapeptide amide and a tetracosapeptide containing the lower homologue of arginine (norarginine) in position 8, have been synthesized by the generally accepted method. Special attention was paid to the synthesis of the required tetrapeptide representing the 7–10 sequence, which was obtained either by direct introduction of L‐nitronorarginine or by amidination of the γ‐amino function in a protected peptide containing α, γ‐diaminobutyric acid.Biological activity determination showed that the shortening of the arginine side chain in position 8 results in the formation of active ACTH‐analogues.
INVESTIGATION OF THE ROLE OF TRYPTOPHAN IN α‐MSH*:
Authors: VAN Nispen J. W. , Smeets P. J. H. , Poll E. H. A. , Tesser G. I. 
Published: August 2010

Two analogues of α‐MSH are described, in which the tryptophan residue occuring in position 9 of the natural hormone has been replaced by pentamethyl‐phenylalanine and phenylalanine, respectively. The analogues were synthesized via a conventional procedure and the [Phe9]‐analogue also by a semi‐synthetic approach, which demonstrated thefavourable properties of the applied, new amino‐protecting Msc function for this purpose.The widely different electron donor properties of the substituted residues were accompanied by a large difference in melanocyte stimulating activity of the analogues. The [Pmp9]‐analogue, having donor properties comparable to those of the natural compound, was four to five times more active than the analogue containing the poorly donating Phe residue. The opposite effect was noted in in vivo lipolysis in rabbits.
NON‐ELASTOMERIC POLYPEPTIDE MODELS OF ELASTIN
Authors: Rapaka Rao S. , Okamoto Kouji , Urry D. W. 
Published: August 2010

The synthesis of two polyhexapeptides is reported. The polyhexapeptides are H‐(Val6‐Ala1‐Pro2‐Gly3‐θ4‐Gly5)n ‐Val‐OMe where θ= Vol or Lys with a mole ratio of 3.5:1 and H‐(Val6‐Ala1‐Pro2‐Gly3‐Lys4‐Gly5)n‐Val‐OMe. The first polymer was utilized with a previously synthesized polyhexapeptide, H‐(Val6‐Ala1 ‐Pro2‐Gly3‐θ‐Gly5)n‐Val‐OMe where θ was either Val4 or Glu4 at a mole ratio of 3.5:1, to obtain an intermolecular cross‐linked matrix by means of primary amide bond formation between the γ‐carboxyls of the Glu residues of one copolymer and the α‐amino groups of the Lys residues of the other copolymer. The cross‐linking reaction was run during a temperature‐elicited phase separation with flow orientation of the polymers. An insoluble, non‐elastomeric, cross‐linked, polyhexapeptide matrix was obtained. The nature of the insoluble polyhexapeptide matrix was well‐demonstrated by the polymer, H‐(Val6‐Ala1‐Pro2‐Gly3‐θ4‐Gly5)n‐Val‐OMe where θ4 is Vol or Lys, which could be formed into cellophane‐like, non‐elastomeric sheets which would tear and which could be shown by microscopy to have sharp edges. This very different property of the polyhexapeptide of tropoelastin as compared to the elastomeric polypentapeptide of tropoelastin is discussed in terms of a different structural role.The purity of key intermediate hexamers and of the polyhexapeptides is demonstrated by carbon‐13 magnetic resonance in addition to the usual analytical methods.
BACKBONE TORSIONAL POTENTIAL FUNCTIONS FOR ROTATIONS ABOUT N‐Cα AND Cα‐C BONDS IN DIPEPTIDE MODEL SYSTEMS IN RELATION TO NUCLEAR MAGNETIC RESONANCE AND INFRA RED SPECTRAL DATA*
Authors: Mitra Alok K. 
Published: August 2010

A comparative study of the conventional three‐fold torsional potential functions (referred to as “Old V”), the potential function having zero φ barrier and a twofold ψ‐barrier, proposed from this laboratory (“Int V”), and those developed recently in this laboratory from the study of dipeptide conformations in protein crystal structures (“New V”) has been carried out by comparing theoretically calculated and experimentally observed NH‐CαH coupling constants from n.m.r. studies and the relative occupancy of hydrogen‐bonded conformations from i.r. studies of dipeptide model systems. It is observed that no fully satisfactory agreement with both n.m.r. and i.r. data is possible in any one of the three functions. For the hydrogen bond‐disrupting solvent DMSO, (NH‐CαH) coupling constant values were predicted equally well in all three. However, only for New V are values of the constants A (= 8.62), B (= ‐2.33), C (= 1.51) as obtained by the least‐squares method in the expression J(θ) = A cos2θ+ B cos θ+ C sin2θ such that J‐values in excess of 10Hz, observed experimentally in some cases, are permissible. However, the same potential function yields unsatisfactory agreement in the case of hydrogen bond‐promoting solvent CCl4. This was interpreted to be because the potential function concerned was obtained from data in solid state where solvent interaction is absent.In view of the lack of satisfactory agreement with the solution data for all three potential functions, it was concluded that solvent effects other than the promotion of intramolecular hydrogen bonding, which were ignored in the present study, must be taken into account for better prediction of experimental data from theoretical potential functions.
HALOACETYL GROUPS AS REVERSIBLE PROTECTION OF THE AMINO FUNCTION: CLEAVAGE WITH 2‐AMINOTHIOPHENOL
Authors: GLASS JOHN D. , PELZIG MICHAL , PANDE CHANDRA S. 
Published: August 2010

Haloacetylamino acids and haloacetyl peptides react rapidly with 2‐aminothiophenol in weakly alkaline media to yield 2‐aminothiophenoxyacetyl derivatives. These intermediates are subject to acidolysis under mild conditions with release of free amino acids or peptides. With this mild method for removal of the haloacetyl group N‐haloacetoxysuccinimide derivatives, which rapidly and specifically acylate amino groups of polypeptides in aqueous solutions, become promising reagents for the reversible protection of amino groups. The chloro‐acetylation of amino groups in lima bean trypsin inhibitor and the quantitative removal of the chloroacetyl groups demonstrate the applicability of the method for polypeptides. The haloacetyl group also serves an analytical function in that treatment of a completely or partially haloacetylated polypeptide with cysteine forms one carboxymethylcysteine residue per haloacetyl group in the polypeptide derivative. Carboxymethylcysteine is readily measured by amino acid analysis of acid hydrolysates.Approaches to further improvement of conditions for removal of haloacetyl groups are discussed and potential applications of the general chemistry of 2‐haloacids to modern polypeptide chemistry are outlined.
MALEYLATION AND PH‐DEPENDENCE OF STREPTOMYCES GRISEUS PROTEASE B
Authors: SHINAR SHULAMIT , GERTLER ARIEH 
Published: August 2010

The enzymatic activity of Streptomyces griseus protease B (SGPB) was measured over pH range 8.4–11.5 using a specific new, chromophoric substrate N‐succinyl‐glycyl‐glycyl‐l‐phenylalanine p‐nitroanilide. It was found that the activity is dependent on ionization of a single group with apparent pK = 10.84, possibly lysine‐125. Maleylation of the ∍‐amino group of this lysine was linearily associated with the loss of enzymatic activity.It is therefore suggested that the electrostatic interaction between the side chain of lysine‐125 and the α‐carboxyl group of the the C‐terminal tyrosine is crucial to the active conformation of the enzyme. In contrast the maleylation of the α‐amino group of the N‐terminal isoleucine was rapid but could not be correlated to the loss of activity.
EFFECTS OF d AND l AMINO ACID RESIDUES IN LINEAR PEPTIDES ON CARBON‐13 NUCLEAR MAGNETIC RESONANCE PARAMETERS
Authors: DESLAURIERS ROXANNE , SMITH IAN C.P. , SOMORJAI R.L. , RALSTON E. , ORLOWSKI R.C. , WALTER RODERICH 
Published: August 2010

The 13C spectra of the linear tripeptidyl diastereoisomers, Gly‐Gly‐Leu, Gly‐Gly‐d‐Leu, Leu‐Gly‐Gly, d‐Leu‐Gly‐Gly, Ala3, Ala‐Ala‐d‐Ala, Ala‐d‐Ala‐Ala, Val3, and Val‐Val‐d‐Val are very similar or even identical at pH meter readings of 1.0, 7.0 and 12.0 in D2O. The spectra of Pro‐Leu‐Gly‐NH2 and Pro‐d‐Leu‐Gly‐NH2 likewise show only minor differences in 13C chemical shifts (less than 0.4 p.p.m.) under similar conditions. This contrasts significantly with previous findings comparing 13C chemical shifts of cyclo (Pro‐Leu) and cyclo (Pro‐d‐Leu) where major differences in chemical shifts were observed for both residues due to differences in conformational constraints present in these cyclic prolinecontaining peptides.The least‐squares fit of spin‐lattice relaxation times (T1) for Pro‐Leu‐Gly‐NH2 and Pro‐d‐Leu‐Gly‐NH2 show that it is not possible to fit all the T1 values to a unique and rigid structure whether folded or extended. The glycyl residue undergoes enhanced motion when compared with the prolyl and leucyl residues. Internal motion must be postulated within the proline ring and for the CH3 groups of leucine.
FORMATION OF AMINOSUCCINYL PEPTIDES DURING ACIDOLYTIC DEPROTECTION FOLLOWED BY THEIR TRANSFORMATION TO PIPERAZINE‐2, 5‐DIONE DERIVATIVES IN NEUTRAL MEDIA
Authors: SCHÖN ISTVÄN , KISFALUDY LAJOS 
Published: August 2010

Prolonged acidic treatment of Boc‐Leu‐Asp(OBut)‐Phe‐NH2 with 4N HCl in acetic acid resulted in H‐[Leu‐Asc‐Phe‐NH2] HCl(Asc, aminosuccinyl), which transformed partially to cyclo[Leu‐Asp(Phe‐NH2)] during its purification by column chromatography on silica gel with a mixture of ethyl acetate/pyridine/acetic acid/water = 60:20:6:11, i.e. in neutral medium. Examination of the imide formation was extended to different reaction conditions (no imide derivative was detected in trifluoroacetic acid), to several protected derivatives of L‐aspartyl‐L‐phenylalaninamide and to tripeptides containing an aspartyl residue in the middle position. It was clearly demonstrated that in strongly acidic media the imide derivatives are directly formed from the aspartyl peptides containing a free β‐carboxyl group.The influence of the C‐terminal residue was greater than the N‐terminal on both the rate of formation of the imide and its further transformation to piperazine‐2,5‐dione derivative. In aqueous ethanol the X‐Asc‐Y‐NH2 (X, Pro, Leu; Y, Gly, Ala, Val, Phg, Phe) containing N‐terminal proline are more readily transformed to piperazine‐2,5‐dione derivatives, but compared to simple proline dipeptides the rate of this transformation is relatively slow because of the crowdedness of the tricyclic transitional state.
N‐TERMINAL AMINO ACID SEQUENCE OF PROALBUMIN FROM INBRED BUFFALO RATS
Authors: MILLERSHIP ANNE , EDWARDS KAYLENE , CHELLADURA MOHANATHASAN , DRYBURGH HEIDE , INGLIS ADAM S. , URBAN JÖRG , SCHREIBER GERHARD 
Published: August 2010

The sequence of radioactively labelled amino acids at the N‐terminus of proalbumin was determined by automated Edman‐degradation. [3H] Valine, [3H] phenylalanine or [14Carginine was incorporated into protein in vivo for a time period of 10 min after injection. Since albumin remains unlabelled during this time period (Urban et al., 1976), separation of proalbumin and albumin was not required for this work. Hence, compared to previous methods, a shorter purification procedure could be used which increased the yield of anti‐albumin‐precipitable protein and reduced the risk of proteolysis.Microsomes were prepared from livers removed 10 min after injection of the radioactively labelled amino acids. A buffer extract of the acetone‐dried powder from these microsomes was chromatographed on DEAE‐cellulose. All protein obtained after chromatography which could be precipitated with antiserum to serum albumin was isolated by immunoprecipitation and subsequent separation of the antigen‐antibody complex. The sequence of radioactive amino acids in this antigen preparation suggests that about 20–25% of proalbumin possessed at the N‐terminus the pentapeptide sequence X‐Val‐Phe‐Arg‐Arg‐ whereas 75–80% contained the hexapeptide sequence Arg‐X‐Val‐Phe‐Arg‐Arg‐.
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.
Circular dichroism studies on conformational transitions of phytohemagglutinins effected by some alcohols
Authors: JIRGENSONS BRUNO , ROSS DORIS L. 
Published: August 2010

The effects of methanol, ethanol, 1‐propanol and 2,2,2,‐trifluoroethanol (TFE) on conformation of 10 phytohemagglutinins (lectins) were examined by applying the circular dichroism (CD) method. Concanavalin A and the lectins isolated from pea (Pisum sativum), lentil (Lens culinaris), soybean (Glycine max), peanut (Arachis hypogaea), Dolichos biflorus, Sophora japonica, Lotus tetragonolobus, Ulex europaeus I, and Phaseolus vulgaris (leucoagglutinin) were used.Slight changes in the structure of these proteins were observed at relatively low concentrations (5–20 vol. %, pH 7.2–8.2, at 22–25°) of the perturbants, and the effectiveness of the alcohols increased with their concentration and molecular weight. The circular dichroism bands related to the aromatic side chain chromophores decreased in the presence of the alcohols. The secondary structure was reorganized by high concentrations (30–80 vol. %) of the alcohols, as indicated by CD at 187–250 nm. Curves typical for proteins of relatively high α‐helix content (strong positive CD bands at 191 nm and negative bands at 206–208 and 222 nm) were recorded in the presence of high concentrations of trifluoroethanol.
Side chain characteristic main chain conformations of amino acid residues
Authors: KOLASKAR A.S. , RAMABRAHMAM V. 
Published: August 2010

Main chain conformation characteristics of the respective side chains of the 20 naturally occurring amino acid residues were obtained by the analysis of (φ, ε)‐data from the crystal structures of 38 different globular proteins. The following observations are of interest: (i) For amino acids other than Glu, Thr and aliphatic amino acids, at least one main chain conformation is stabilised solely by side chain atoms. Such conformations are listed. (ii) In globular proteins, the main chain conformations which are significantly destabilised by side chain atom interactions are observed. The stabilising force for those conformations seems to come from main chain atom interactions. (iii) A set of conformations for which the main chain and side chain interactions are almost equal but in opposite directions, is listed and these conformations will be taken by residues mainly due to the effect of surroundings.The results can be used to study the folding of polypeptide chains and they also provide an insight into the role of the respective side chains on main chain conformations of amino acid residues.
Identification of secondary structures in globular proteins ‐ a new algorithm*
Authors: Ramakrishna C. , Soman K.V. 
Published: August 2010

A new algorithm has been developed for identifying helices, extended structures, and bends from the positions of the α‐carbon atoms using the virtual bond approach. The parameters used are two virtual bond angles (Δ1 and Δ2), the virtual dihedral angle (θ), and the distance (D) between the terminal α‐carbon atoms of the tripeptide.The criteria for classification have been worked out by model building as well as from proteins whose complete secondary structures are known. These criteria are as follows: (i) |θ| ≤ 60° and (Δ1+Δ2) ≤ 230° for a bend, (ii) for a helix, successive θ's should not differ by more than 30°, and (iii) for an extended structure, the cumulative deviation of the above parameters should not vary by more than 20% from the ideal extended chain. The method developed has been applied successfully to three proteins wherein the coordinates of α‐carbon atoms alone are known and a complete mapping of the secondary structures has now been obtained. One interesting observation is that the percentage of residues not taking part in helices, extended structures, and bends is very small ‐ of the order of 4%.
Refinement of conformational preferences of Leu enkephalin and Tyr‐Gly‐Gly‐Phe by 15 N n.m.r.
Authors: GARBAY‐JAUREGUIBERRY C. , MARION D. , FELLION E. , ROQUES B.P. 
Published: August 2010

15N labeled Tyr‐*Gly‐*Gly‐*Phe (I) and Tyr‐*Gly‐*Gly‐*Phe‐*Leu or Leuenkephalin (II) are taken as models to test the ability of 15N n.m.r. as conformational probe for peptide analysis. Analysis of the 3J 15 N‐1Hα constants using a Karplus relationship permits the proposal of a 2–5 βII type turn for Leuenkephalin, instead of the previously proposed 2–5 βI bend. In the two peptides, side‐chain populations for Phe and Leu residues are computed, without any assignment assumption, by an optimization procedure taking into account all the available vicinal coupling constants (3JHαHβ, 3J 13CO‐Hβ, 3J 15N‐Hβ). Our results confirm the upfield shift of the β ProR proton relatively to the β ProS for the β CH2 group of Phe residue in Me2SO solution.In both peptides (I) and (II), the tg° rotamer is the most populated for residue Phe4, whereas in (II) only this rotamer is present for the Leu5 sidechain. This feature indicates that the hydrophobic group lies opposite to the N‐terminal Tyr residue, a feature not found for the methionine side‐chain in Met‐enkephalin.
Regeneration of native structure and biological activity by air oxidation of the reduced bovine trypsin inhibitor (Kunitz)*
Authors: BIONDI LAURA , FILIPPI BRUNO , FILIRA FERNANDO , TOLAZZI MARILENA , ROCCHI RANIERO 
Published: August 2010

Derivatives of the tetraguanidinated bovine trypsin‐kallikrein inhibitor lacking up to four amino‐acid residues have been prepared by Edman degradation of the amino‐terminal Arg‐Pro‐Asp‐Phe sequence. Comparative studies on the native inhibitor, tetraguanidinated inhibitor, and truncated sequences demonstrated that none of the four N‐terminal amino‐acid residues are essential for the regeneration of native structure and biological activity by air oxidation of the reduced molecule.However residues 2, 3, and 4, although to a different extent, are important for the protein stability and significantly affect the conformation of the tetraguanidinated inhibitor and the rate of the reactivation process.Removal of the terminal positive charge from Arg 1 by diazotization gave a fully active deaminated, tetraguanidinated inhibitor but the lack of the salt bridge interaction between the amino and the carboxyl terminus of the protein prevented the correct folding of the reduced molecule by air oxidation as shown by activity measurements and conformational studies.The stability constants and the standard free energies of binding of the complexes between trypsin and the different inhibitor derivatives have been determined.
Denaturation of concanavalin A by urea at acid pH
Authors: AUER HENRY E. , SCHILZ TIMOTHY 
Published: August 2010

The denaturation of dimeric concanavalin A induced by urea at pH 3 has been studied using optical activity and sedimentation velocity. Under the conditions employed Mn+2 and Ca+2 are dissociated from the protein, but the basic structural elements are little changed from those prevailing in the functional lectin at pH 5.5 [H.E. Auer and T. Schilz, preceding paper in this issue]. The protein passes through three stages as the urea concentration is varied from 0 to 10 M. Below 4M urea the only effect observed is the loss of optical activity of the aromatic amino acid residues. At 4 M, a conformational change occurs producing extensive aggregation, which persists to 7 M. At 8–10 M urea a disordered monomeric protein molecule prevails. The protein could be reactivated provided that dilution to native conditions was very rapid and the protein concentration remained very low.Kinetics of denaturation were monitored by optical activity at 218, 225 and 283 nm, Transients with one, two or three components were observed, which were resolved by nonlinear regression according to sequential first‐order decay laws. First order character was confirmed by independence of the kinetic parameters from protein concentration over a two‐ to four‐fold range. Enthalpies and entropies of activation for the various steps were also determined. The transients at the three wavelengths monitor changes in β structure, β turns and aromatic groups, respectively. The urea dependence of the rate constants is unique in most cases. It is concluded that different structural elements of the concanavalin A molecule unfold independently from one another.