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G Valensin

Publications and source records attributed to G Valensin.

At least 37 records · Page 2Linked to original sources
PubMed1990

1H-NMR studies of postmortem biochemical changes in rat skeletal muscle.

1H-nuclear magnetic resonance (NMR) has been applied to the study of postmortem biochemical changes in perchloric acid extracts of rat skeletal muscle. Several metabolites have been detected and the dependence upon the postmortem time has been considered. The simultaneous quantitative determination of metabolites showing up at very low and very high fields has been suggested to yield a satisfactory delineation of the thanatochronology.

Animals↗
PubMed1990

Adenosine blocks calcium entry in activated neutrophils and binds to flunarizine-sensitive calcium channels.

Adenosine is able to prevent Ca+(+) influx into activated neutrophils as detected by the specific fluorescent indicator Quin 2. Such an effect is shown in a similar fashion by the calcium entry blocker flunarizine. The binding interaction between flunarizine and the neutrophil membrane as well as the flunarizine-adenosine antagonism are shown by the 1H-NMR technique, thus supporting evidence of a competition between the agents at the same or a nearby site on the cell membrane.

Adenosine↗
PubMed1990

NMR investigation of cell cultures: early detection of infection by Herpes simplex virus type 2 and transformation.

The water proton Nuclear Magnetic Resonance (NMR) spin-lattice relaxation rates were measured in suspension of uninfected and Herpes simplex virus type 2-infected WI-38 diploid cells and shown to allow reliable detection of (i) the early signs of productive infection, and (ii) the tendency to undergo either spontaneous or virus-induced transformation. In addition, NMR investigation of several transformed cell lines currently and previously established from WI-38 cells clearly indicated that the NMR relaxation parameter is a suitable tool for assessment of the level of malignancy, as revealed by in vivo oncogenicity tests in immunosuppressed mice.

Animals↗
PubMed1988

NMR investigation of the copper(II)-carnosine complex in water solution.

The predominant species in water solution of excess carnosine and Cu2+ ions was characterized by measuring 13C and 1H spin-lattice and spin-spin relaxation rates. Four peptide molecules were calculated to be coordinated to the metal through the imidazole nitrogen. Evaluation of ion-proton distances demonstrated that metal complexation does not involve severe changes in conformation of the peptide.

Carnosine↗
PubMed1988

Conformational dynamics of cytochalasin B in solution as detected by 13C and 1H NMR relaxation rates.

13C and 1H NMR spin-lattice relaxation rates have been measured for cytochalasin B in [2H]6DMSO. Motional features have been interpreted in terms of nearly isotropic reorientation of the whole molecule with few additional internal motions. The 'isotropic' reorientational correlation time was evaluated at 0.21 ns at room temperature. By using selective and double-selective excitation techniques, relevant cross-relaxation terms have been obtained wherefrom proton-proton distances have been calculated. A Dreiding model of the 'preferred' conformation in solution has been built, yielding evidence of a strong similarity between solution and solid state structures of cytochalasin B.

Carbon Isotopes↗
PubMed1987

Receptors on the neutrophil membrane. I. Flunarizine-adenosine antagonism as detected by 1H-nuclear magnetic resonance relaxation investigations.

Selective proton relaxation rates were measured for selected protons of flunarizine in the presence of neutrophils, yielding evidence of a binding interaction that involves different moieties of the drug. Fast exchange between bound and free environments was demonstrated as the main factor determining the selective relaxation rate enhancement, whereas viscosity effects were shown to be negligible. The relaxation effect was cancelled out by the presence of adenosine as a cosolute in a dose-dependent fashion, leading to the suggestion that the endogenous mediator adenosine affects binding of flunarizine to the neutrophil surface.

Adenosine↗
PubMed1986

Liposomes containing paramagnetic macromolecules as MRI contrast agents.

The use of paramagnetic ions, bound to macromolecules and trapped in liposomes, as MRI contrast agents is suggested. As an example, the system of Mn2+ bound to serum proteins was tested. The binding of the metal ions to the macromolecules enhances their relaxation and at the same time decreases their rate of diffusion out of the liposomes. The use of liposomes is expected to reduce the potential toxicity of the paramagnetic ions and allows their targeting toward specific tissues.

Beta-Globulins↗
PubMed1986

Selective 1H-NMR relaxation investigations of membrane-bound drugs in vitro. 2. Angiotensin II.

Binding interactions between human angiotensin II and dipalmitoylphosphatidylcholine bilayer vesicles have been detected by measuring the selective proton spin-lattice relaxation rates of aromatic protons within the peptide. Involvement of the imidazole moiety of the His-6 residue has been demonstrated by the pH dependence of the NMR observables. A lower limit of the binding constant has been evaluated at 78.12 mol-1 dm3 for the interaction involving nonionic intermolecular forces between aromatic residues and the lipid matrix.

Angiotensin II↗
PubMed1986

Conformation and dynamics of the chemotactic peptide formyl-L-methionyl-L-leucyl-L-phenylalanine in solution.

Several conformational and dynamic features of the chemotactic peptide formyl-L-methionyl-L-leucyl-L-phenylalanine in solution have been delineated by investigations of NMR and IR spectroscopic parameters. Both 1D and 2D NMR experiments have been performed for detection of scalar and dipolar proton-proton connectivities, whereas 13C and 1H relaxation parameters have been interpreted in terms of molecular dynamics. The main conformation appeared to be unfolded with the three hydrophobic side chains extending in divergent directions with respect to the backbone. The existence of relatively weak intermolecular hydrogen bonds was demonstrated, involving the formamide end group, with increase in the hydrophobicity of the external surface.

Magnetic Resonance Spectroscopy↗
PubMed1985

Nuclear magnetic resonance probes for investigations of the virus-cell interactions.

Measuring the NMR relaxation parameters of selectively excited protons within molecules bound to the cell membrane was shown to provide a profitable way of looking at the virus-cell interaction. Such approach made it possible to delineate the virus adsorption to human red blood cells by using the NMR features of the cytoskeleton inhibitor colchicine.

Adsorption↗
PubMed1985

Structural, motional, and kinetic features of the Cu(II)-(L-His)2 complex in aqueous solution.

A careful analysis by 1H and 13C FT-NMR on the Cu(II) (L-histidine)2 complex was carried out which allows delineation of structure and dynamics in solution. A mixture of complexes was shown such that 24% of the Cu(II) (L-histidine)2 complex contains both histidines bound in the histaminelike way, while the remaining 76% contains one L-His molecule bound in the histaminelike way and the other L-His molecule bound in the glycinelike way. The motional correlation time and relevant features of the exchange process were also delineated.

Chemical Phenomena↗
PubMed1985

Conformational and dynamic features of cocaine in DMSO-d6 solution.

13C spin-lattice relaxation rates, 13C {1H} NOESs, 1H spin-spin relaxation rates and 1H two-dimensional magnetization transfer spectroscopy were used for delineating conformational features of cocaine in DMSO-d6 solution. Two main conformations differing in the orientation of the plane made by the benzoxy substituent with respect to the piperidine ring principal axis were observed. Relatively slow interconversions of the piperidine ring were delineated together with the main motional features of the whole molecule.

Journal Article↗
PubMed1985

Selective 1H-NMR relaxation investigations of membrane-bound drugs in vitro. 1. Colchicine.

Binding of colchicine to dipalmitoylphosphatidylcholine bilayer vesicles was detected by measuring the 1H-NMR selective spin-lattice relaxation rates of the low-field protons of colchicine. From the temperature dependence of the selective rates, preferential binding was observed above the temperature of transition. In the same way, binding of colchicine to red blood cells was detected and the equilibrium constant determined. Binding to the lipid matrix of red blood cells accounted only partially for the binding of colchicine to whole cells.

Journal Article↗
PubMed1985

Binding features of diacetylmorphine (heroin) in whole blood and in blood fractions.

Binding features of heroin in whole blood and in blood fractions were delineated by measuring the selective spin-lattice relaxation rates of heroin protons in physiologic conditions. Interaction with some receptor located in the whole human blood or in the human plasma was detected and the apparent binding constant calculated (K = 39 mol-1 dm3). Inferences about molecular dynamics of the bound heroin could be also gained.

Erythrocytes↗
PubMed1984

The effect of binding divalent metal ions on the conformation of human angiotensin-II in solution as probed by nuclear and electron paramagnetic resonance investigations.

The interaction between human angiotensin-II and Mn(II) ions in water solution has been delineated by nmr and esr experiments. A pH-dependent binding interaction with the imidazole moiety of His 6 has been shown, ratifying the suggestion that His 6 is involved in intramolecular structuring within the peptide molecule.

Angiotensin II↗
PubMed1983

Conformational features of cell-bound drugs as detected by selective proton relaxation rate investigations.

The nonselective and selective longitudinal relaxation rates were measured for procaine protons in the presence of model lipid membranes, biological membranes and whole cells. Unlike the nonselective relaxation rates, the selective rate was shown to be particularly sensitive in detecting binding interactions with macromolecular cell constituents. It was shown that the aromatic moiety of procaine is involved in binding the cell plasma membrane.

Carcinoma, Squamous Cell↗