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Biomedical subjects

N Niccolai

Publications and source records attributed to N Niccolai.

9 recordsLinked to original sources
PubMed1992

Probing protein structure by solvent perturbation of nuclear magnetic resonance spectra. Nuclear magnetic resonance spectral editing and topological mapping in proteins by paramagnetic relaxation filtering.

Soluble spin labels, which "bleach" the surface proton resonances of a protein to n.m.r. measurements, can provide useful information about protein conformation and dynamics. The use of the soluble nitroxide, TEMPOL, has been explored to show the correlation of the paramagnetic perturbations of protein two-dimensional n.m.r. data with proton exposure to the free radical in hen egg-white lysozyme. The results demonstrate that the nitroxide approaches the protein randomly, and that the extent of the observed paramagnetic effects reflects the native folding pattern of the protein. A correlation of spectral simplification with the known tertiary structure establishes the feasibility of new strategies for topological mapping of surface and buried protons of the protein. Application to the elucidation of protein structure and to the study of dynamical processes is discussed.

Amino Acid Sequence↗
PubMed1991

1H- and natural abundance 15N-NMR studies of a derivative of a rabies glycoprotein fragment.

Using a combination of one- and two-dimensional methods, 1H- and 15N-nmr spectroscopy has been employed to perform the complete assignment and the structural determination of the immunogenic undecapeptide CTTTNSRGTTT in DMSO solution. Nuclear Overhauser enhancement spectroscopy experiments indicated the presence of secondary structures, mainly turn-like structures, which only represent a family, albeit a dominant one, of an ensemble of conformations available to the peptide. Since reverse turns may play an important role as intermediates in protein folding, the experimental observations described here may link the immunological and theoretical approaches to protein folding.

Amino Acid Sequence↗
PubMed1990

Solvent spin-labelling for investigating the interaction of biological ligands with macromolecules. A 1H paramagnetic relaxation study.

The paramagnetic contributions to the spin-lattice relaxation rates of khellin protons, induced by the presence in an aqueous solution of TEMPO nitroxide, have been analyzed in the interaction of the furochromone with DNA. The relaxation data obtained at different temperatures, nitroxide and DNA concentrations indicate that the average solvent exposure of the furanic moiety of khellin is lower than that of the pyranic group. This feature suggests that the former is the main site of approach of khellin to DNA.

DNA↗
PubMed1988

Antipeptide monoclonal antibodies inhibit the binding of rabies virus glycoprotein and alpha-bungarotoxin to the nicotinic acetylcholine receptor.

It has been reported that binding to muscle nicotinic acetylcholine receptor at the post-synaptic membrane is an important event of the rabies virus neurotropism. The binding site can be located within the 190-203 region of the virus glycoprotein sharing a high degree of homology with the "toxic loop" of the curare-mimetic snake neurotoxins. We have synthesized a tetradecapeptide corresponding to this glycoprotein region and used it, following conjugation with an immunogenic carrier to raise MAbs. We found that some MAbs raised against the peptide were able to recognize both the virus glycoprotein and the snake neurotoxin alpha-bungarotoxin; moreover, they can inhibit the binding of rabies virus glycoprotein and alpha-bungarotoxin to the nicotinic acetylcholine receptor extracted from the electric organs of Torpedo marmorata. On the basis of this cross-reactivity, we suggest that rabies virus glycoprotein and curare-mimetic snake neurotoxins share three-dimensionally similar structures in order to bind to the nicotinic cholinergic receptor. The potential use of the immunogenic properties of the peptide for the rational design of a synthetic vaccine against rabies is proposed.

Antibodies, Monoclonal↗
PubMed1987

Resolution of conformation equilibria in linear peptides by circular dichroism in cryogenic solvents.

The circular dichroism spectra of the synthetic peptide antigen, 209-222 of the surface glycoprotein of the rabies virus were recorded as a function of solvent composition and over the temperature range of +60 degrees C to -135 degrees C; beta-III and beta-II reverse turn conformations were found to exist in TFE/H2O (3:1) at room temperature and in ethanediol/H2O (2:1) below -110 degrees C respectively. Evidence, from comparison of observed and calculated spectra, is given to support the existence of a conformational equilibrium between a beta-II and a beta-III reverse turn. These data can serve as a basis for synthetic vaccine development and understanding the nature of polypeptide chain folding.

Circular Dichroism↗
PubMed1986

The mechanisms of interaction between furanochromones and DNA. A heteronuclear Overhauser effect study on the khellin-thymidine model system.

The furanochromones khellin and visnagin have been characterised by 1H and 13C mono- and bidimensional NMR spectroscopies. Their strong affinity with DNA was experimentally confirmed by the complete disappearance of the furano-chromones' NMR signals upon additions of DNA. An intermolecular interaction between furanochromones and the thymidyl moieties of DNA, stabilized by the formation of a hydrogen bond between the thymidyl NH hydrogen and the C = O group of khellin or visnagin, is here proposed. This is suggested by the strong donor-acceptor behavior of these two molecular moieties, as pointed out by a selective 1H-13C Overhauser effect study of the khellin-thymidine model system.

Carbon Isotopes↗
PubMed1978

Coordination behaviour of antithyroid drugs against the Fe(I)(NO)2 group in solution: ESR and FT-NMR study.

The binding sites of some types of antithyroid drugs in the presence of the Fe(I)(NO)2 paramagnetic probe were investigated. Coordination behaviour in solution of different structured ligands was determined by means of ESR parameters and 13C FT-NMR spectra. Selective isotopic substitution with 15NO combined with computer simultation was used to elucidate overlapping ESR patterns. A correlation between chemical structure and antithyroid activity of the pharmacological bases is suggested.

Aniline Compounds↗