A 31P-NMR study on multilamellar liposomes formed from the lipids of a thermophilic bacterium.

The membrane lipids of a thermophilic bacterium, Thermus SPS11, isolated from thermal springs in São Pedro do Sul, Portugal, were fractionated by chromatography on silica gel. The total lipid extract was found to contain one major phospholipid (PL), which accounts for about 90% of the total lipid phosphorous, and one major glycolipid (GL), which accounts for about 95% of the total carbohydrate in the non-phospholipid fraction. The membranes also contain about 11% by weight of a complex mixture of carotenoids (CA).

1H and 31P NMR study of the interaction of molybdate with the nucleotides adenosine 5'-diphosphate and adenosine 5'-triphosphate.

ADP and ATP form in acidic aqueous solutions strong complexes with Mo(VI) oxocations in different stoichiometries. Complexation occurs predominantly, if not exclusively, through the phosphate groups of the nucleotides.

Magnetic field dependence of solvent proton relaxation rates induced by Gd3+ and Mn2+ complexes of various polyaza macrocyclic ligands: implications for NMR imaging.

The magnetic field dependence of the solvent water proton longitudinal relaxation rate 1/T1 (the NMRD profile) has been measured for solutions of chelates of Gd3+ and Mn2+ ions with two different polyaza macrocyclic ligands: 1,4,7-triazacyclononane-N,N',N",-triacetic acid (NOTA) and 1,4,7,10-tetraazacyclododecane-N,N',N",N'"-tetraacetic acid (DOTA). Studies were carried out mainly near physiological pH, but the pH dependence was also examined in some cases. The results are compared with published data for complexes of Gd3+ and Mn2+ ions with ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA).

Nuclear-magnetic-resonance study of the conformation of a dinucleotide in solution using the lanthanide probe method.

The conformation of the dinucleotide adenylyl(3'-5')adenosine 2'-phosphate (ApA2'p) in aqueous solution at different pH values and temperatures has been studied using the lanthanide(III) ethylenodiaminetetraacetate(EDTA) 1:1 complexes as shift and relaxation probes. The conformational analysis, based on mixing different conformations in fast exchange within the nuclear magnetic resonance time scale, agrees well with the results from vicinal coupling constants and dimerization shifts obtained for the metal-free system. The dinucleotide exists in a temperature-dependent and pH-dependent conformational equilibrium between unstacked and base-stacked forms.

Nuclear-magnetic-resonance studies of 5'-ribonucleotide and 5'-deoxyribonucleotide conformations in solution using the lanthanide probe method.

The conformations of the metal-bound 5'-ribonucleotides and 5'-deoxyribonucleotides in aqueous solution at different pH values have been studied using the lanthanide probe method. The conformational analysis, based on mixing different conformations in fast exchange within the nuclear magnetic resonance time scale, agrees well with the results from coupling constants, nuclear Over-hauser effects and spin-lattice relaxation times, obtained for the metal-fixed systems. The equilibrium between the two basic conformational combinations for the 5'-nucleotides, anti-(N in equalibrium S)-gg-g'g' and syn-(N in equalibrium S)-gt-g'g' depends on the nature of the furanose ring, the base and also on the state of base protonation and phosphate ionization.

Conformational studies of some 2':3'-cyclic mononucleotides in solution by different nuclear-magnetic-resonance methods.

The conformations of the 2':3'-cyclic mononucleotides of adenosine and cytidine in deuterium oxide has been studied at pH 2.3, using lanthanide ions as paramagnetic nuclear magnetic resonance (NMR) probes. It was not possible to find any single conformation for these molecules which accounts for the observed shift and relaxation data.

Nucleotide torsional flexibility in solution and the use of the lanthanides as nuclear-magnetic-resonance conformation probes. The case of adenosine 5'-monophosphate.

In this article the single family of conformations of adenosine 5'-monophosphate (5'AMP) in aqueous solution previously obtained using the lanthanide ions as nuclear magnetic resonance (NMR) probes is shown to disagree with the conformational data available from independent NMR methods, such as coupling constant and nuclear Overhauser enhancement analysis. The original lanthanide experimental data is reinterpreted assuming the contribution of different conformers to the observed magnetic perturbations. The average conformation obtained for 5'AMP agrees quite satisfactorily with the other independent conformational information.