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Biomedical subjects

O Millet

Publications and source records attributed to O Millet.

5 recordsLinked to original sources
PubMed2001

A graphical method for the analysis of anisotropic rotational diffusion in proteins.

A graphical method for the analysis of relaxation data is presented. It allows a fast estimation of the range of values of the components of the axially symmetric rotational diffusion tensor that are compatible with the experimental relaxation data. The graphical method clearly shows the contribution of different experimental relaxation parameters to the measured anisotropy. In particular, for proteins with moderate anisotropy, data from at least two N-H bonds forming angles close to 0 degrees and 90 degrees with respect to the principal axis of the rotational diffusional tensor are needed. For very anisotropic systems, combination of different relaxation parameters from a single residue is enough to characterize the local anisotropy.

Anisotropy↗
PubMed1999

Measurement of relaxation rates of N(H) and H(alpha) backbone protons in proteins with tailored initial conditions.

Several methods are presented for the selective determination of spin-lattice and spin-spin relaxation rates of backbone protons in labeled proteins. The relaxation rates of amide protons in (15)N labeled proteins can be measured by using two-way selective cross-polarization (SCP). The measurement of H(alpha) relaxation rates can be achieved by combining this method with homonuclear Hartmann-Hahn transfer using doubly selective irradiation. Various schemes for selective or nonselective inversion of the longitudinal proton magnetization lead to different initial recovery rates. The methods have been applied to lysine K6 in (15)N-labeled human ubiquitin and to leucine L5 in (15)N- and (13)C-labeled octapeptide YG*G*F*LRRI (GFL) in which the marked residues are (15)N- and (13)C-labeled.

Carbon Isotopes↗
PubMed1998

A new method for measuring diffusion coefficients by 2D NMR using accordion spectroscopy

Translational diffusion measurements are a useful tool for studying supramolecular complexes and for characterizing the association state of molecules that aggregate at NMR concentrations. Pulsed field gradients can be used to measure diffusion coefficients. Spectral overlap problems in complex mixtures can be alleviated by using 2D spectroscopy but the need to record a complete series of 2D spectra with increasing gradient strength makes these experiments extremely time consuming. Concerted incrementation of the gradient strength and the evolution time provides a new version of accordion spectroscopy that allows the measurement of individual diffusion coefficients in complex mixtures in a single experiment. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Synthesis of aryl 3-O-beta-cellobiosyl-beta-D-glucopyranosides for reactivity studies of 1,3-1,4-beta-glucanases.

A series of substituted aryl beta-glycosides derived from 3-O-beta-cellobiosyl-D-glucopyranose with different phenol-leaving group abilities as measured by the pKa of the free phenol group upon enzymatic hydrolysis has been synthesised. Aryl beta-glycosides with a pKa of the free phenol leaving group > 5 were prepared by phase-transfer glycosidation of the per-O-acetylated alpha-glycosyl bromide with the corresponding phenol, whereas the 2,4-dinitrophenyl beta-glycoside was obtained by condensation of 1-fluoro-2,4-dinitrobenzene with the partially acetylated trisaccharide followed by acid de-O-acetylation. The aryl beta-glycosides have been used for reactivity studies of the wild-type Bacillus licheniformis 1,3-1,4-beta-D-glucan 4-glucanohydrolase. The Hammett plot log kcat versus pKa is biphasic with an upward curvature at low pKa values suggesting a change in transition-state structure depending on the aglycon.

Bacillus↗