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S Andini

Publications and source records attributed to S Andini.

10 recordsLinked to original sources
PubMed1986

Nuclear magnetic resonance of protamines. A 1H-NMR study of the interaction of clupeine fractions with mononucleotides.

The interaction of the three clupeine fractions, YI, YII, Z, and salmine fraction AI with mononucleotides has been examined by means of 1H nuclear magnetic resonance. The results obtained are interpreted in terms of electrostatic interactions between positive arginine guanidinyl groups and negative nucleotide phosphates. In addition, clupeine fraction YI and salmine fraction AI exhibit with guanine and adenine nucleotides a more specific interaction that leads to the formation of large aggregates in solution. The experimental data presented in this work demonstrate that the strength of interaction between clupeine YI and salmine AI with mononucleotides follows the order: 5'-dTMP approximately equal to 5'-dCMP much less than 5'-dAMP less than 5'-dGMP approximately equal to 5'-GMP.

Adamantane↗
PubMed1984

Modified calmodulin calcium binding domain III. Solid phase synthesis, purification and 1H n.m.r. characterization.

The dodecapeptide Ac-Asp-Lys-Asp-Gly-Asn-Gly-Tyr-Ile-Ser-Ala-Ala-Gaba-OH is a modified calmodulin calcium binding domain III. The synthesis of the peptide by the solid phase method with a total protection scheme using PAM-resin is reported. The purified compound has been characterized by 1H n.m.r. spectroscopy, both in the presence and in the absence of calcium ions, at various pHs. No strong specific interaction seems to occur between the peptide and Ca++ ions in water solutions.

Binding Sites↗
PubMed1983

Comparative proton NMR studies of bovine semen and pancreas ribonucleases.

The fine structure of bovine semen RNAase was studied with proton NMR spectroscopy making use of the four-protein system constituted by dimeric bovine semen RNAase, its catalytically active monomeric bis-(S-carboxymethyl-31,32) derivative, the naturally monomeric RNAase A from the pancrease of the same species, and dimerized RNAase A. Only four histidine C-2 H resonances were observed in the aromatic spectrum of bovine semen RNAase, which belong to the four histidine residues present in the sequence of bovine semen RNAase subunits at positions identical with those of the histidines of RNAase A. This is indicative of identical environments for the individual histidine residues in both subunits. These resonances were assigned (i) by comparing their titration curves with the corresponding curves obtained with RNAase A and with monomeric bovine semen RNAase and (ii) by evaluating the effects on their titration curves of nucleotide binding. Very similar NMR parameters were measured for His-105 and also for His-119 of seminal and pancreatic RNAase, while His-12 was found to have different environments in the two proteins. The distinctive NMR features of His-48 in bovine semen RNAase confirmed the role of the hinge regions of the subunits in maintaining the dimeric structure of the protein. While monomerization of the seminal enzyme reduced the differences between the histidine C-2 H resonances of RNAase A and bovine semen RNAase, dimerization of RNAase A did not affect the NMR spectrum of this protein, thus indicating as unlikely the possibility that the quaternary structure of bovine semen RNAase resembles that of dimerized RNAase A.

Animals↗
PubMed1983

Studies on gliadin related peptides. I. Synthesis, purification and 1H n.m.r. characterization of the pentapeptide H-Tyr-(Gln)3-Pro-OH.

The pentapeptide H-Tyr-(Gln)3-Pro-OH has been recently postulated to be the basic repetitive unit of a sequential polypeptide contained in wheat bread alpha-gliadins, which are believed to be toxic factors in coeliac disease, gluten-dependent enteropathy. Solid-phase synthesis, purification and 1H n.m.r. characterization in water solution of this peptide are described.

Chromatography, High Pressure Liquid↗
PubMed1982

Nuclear magnetic resonance of protamines. A 13C relaxation study of the three main fractions of clupeine.

The three main fractions of clupeine, the protamine extracted from herring sperm, have been investigated by 13C nuclear magnetic resonance techniques. The dynamic behaviour, examined through the evaluation of the spin lattice relaxation times (T1) of individual carbon resonances assigned to both backbone and side chains, reveals interesting features. The relaxation times of backbone alpha-carbons, interpreted on the basis of an axially symmetric ellipsoid, point to the clupeine fractions as being essentially extended in aqueous solution. These times remain constant along the polypeptide chain and are of the order of 0.16 +/- 0.02 s. Conversely, the side chains show different flexibilities in the presence of monophosphate counterions, thus demonstrating a diverging behaviour which may be biologically relevant. In particular, the side-chain flexibilities of fraction YI decrease, while those of fractions Z and YII are either constant or increase. Comparison of these data with the viscosity measurements helps in explaining the viscosity changes observed in the presence of phosphate.

Amino Acid Sequence↗
PubMed1976

Structural characterization of thermal prebiotic polypeptides.

Thermal polycondensation of amino-acids as a possible prebiotic path of chemical evolution of life has been critically examined. The polymeric materials studied by nmr methods have scarce resemblance to natural peptidic material because beta, gamma and eplision peptide bonds largely predominate over a-peptide bonds.

Aspartic Acid↗
PubMedDate not supplied

NMR studies of prebiotic polypertides.

Several polypeptides prepared by means of pyrocondensation have been the subject of structural investigations. Attention has been focused on the constitutional characterization of homo-and co-polymers containing Asp and Glu residues, whose role is essential for the formation of the so-called proteinoids. Contrary to the literature data based on chemical degradation, nmr studies show conclusively that in thermal poly-aspartic acid only beta-peptide linkages are present. This result casts serious doubt on the role thermal condensation might have played in prebiotic polypeptide syntheses.

Aspartic Acid↗