Biomedical subjects

Maggy Hologne

Publications and source records attributed to Maggy Hologne.

6 recordsLinked to original sources

PubMed2006

Protein side-chain dynamics observed by solution- and solid-state NMR: comparative analysis of methyl 2H relaxation data.

Rapid advances in solid-state MAS NMR made it possible to probe protein dynamics on a per-residue basis, similar to solution experiments. In this work we compare methyl 2H relaxation rates measured in the solid and liquid samples of alpha-spectrin SH3 domain. The solution data are treated using a model-free approach to separate the contributions from the overall molecular tumbling and fast internal motion. The latter part forms the basis for comparison with the solid-state data. Although the accuracy of solid-state measurements is limited by deuterium spin diffusion, the results suggest a significant similarity between methyl dynamics in the two samples. This is a potentially important observation, preparing the ground for combined analysis of the dynamics data by solid- and solution-state NMR.

Animals↗

PubMed2006

13C/15N distance determination by CPMAS NMR in uniformly 13C labeled molecules.

The REDOR and CPMAS techniques are applied for measuring 13C-15N dipolar coupling constants in glycine. It is shown that the selective CP or SPECIFIC CP technique removes the coherent evolution of the spin system under homonuclear 13C-13C J couplings. While the large coupling constant (approximately 900 Hz) is readily determined because of the presence of large oscillations in the CPMAS dynamics, their absence precludes the measurement of the small coupling constant (approximately 200 Hz). The experimental results and numerical simulations demonstrate that the determination of 13C-15N coupling constants of medium size (<1 kHz) by the CPMAS technique is mainly limited by the strength of the 1H decoupling field and the size of the 13C and 15N chemical shift anisotropies.

Journal Article↗

PubMed2005

Characterization of dynamic processes using deuterium in uniformly 2H,13C,15N enriched peptides by MAS solid-state NMR.

We present in this paper 2H,13C MAS correlation experiments that are performed on a uniformly 2H,13C,15N labeled sample of Nac-Val, and on the uniformly 2H,15N labeled dipeptide Nac-Val-Leu-OH. The experiments involve the measurement of 2H T1 relaxation times at two different magnetic fields, as well as the measurement of the 2H tensor parameters by evolution of the 2H chemical shift. The data are interpreted quantitatively to differentiate between different side chain motional models.

Acetylcysteine↗

PubMed2005

Characterization of dynamics of perdeuterated proteins by MAS solid-state NMR.

We show in this communication that dynamic information for uniformly 2H,13C,15N isotopically enriched, crystalline proteins can be obtained by MAS solid-state NMR spectroscopy. The experiments make use of the deuterium quadrupolar tensor, which is the dominant interaction mechanism. Dynamic properties are accessed by measurement of the size of the quadrupolar coupling constant, Cq, and the value of the asymmetry parameter, eta, via evolution of the deuterium chemical shift, as well as by measurement of deuterium T1 relaxation times. Three-dimensional experiments are performed in order to obtain site-specific resolution. Due to proton dilution, no proton decoupling is required in the carbon evolution periods at MAS rotation frequencies of 10 kHz.

Animals↗

PubMed2005

1H/31P distance determination by solid state NMR in multiple-spin systems.

The results of two techniques of dipolar recoupling, REDOR and CPMAS, are compared in the case of a coupled multiple-spin system. A fundamentally different behavior is observed for these two techniques. In REDOR, the terms associated with each interaction S-I(k) commute with each other and no truncation takes place so that each addition of spin I(k) causes a splitting with its dipolar frequency. In CPMAS, the flip-flop terms of the dipolar Hamiltonian do not commute with the dominant term from the strongly coupled spin pair so that the weak coupling terms from the neighboring spin I(k) are effectively truncated by the dominant pair interaction. Spin dynamics calculations are in agreement with the experimental data in a cubane shaped cluster.

Journal Article↗

PubMed2004

Molecular dynamics as studied by static-powder and magic-angle spinning 2H NMR.

The 2H NMR magic-angle spinning (MAS) technique is compared to the static-powder quadrupole echo (QE) and Jeener-Brockaert (JB) pulse sequences for a quantitative investigation of molecular dynamics in solids. The linewidth of individual spinning sidebands of the one-dimensional MAS spectra are observed to be characteristic of the correlation time from approximately 10(-2) to approximately 10(-8) s so that the dynamic range is increased by approximately three orders of magnitude when compared to the QE experiment. As a consequence, MAS 2H NMR is found to be more sensitive to the presence of an inhomogeneous distribution of correlation times than the QE and JB experiments which rely upon lineshape distortions due to anisotropic T2 and T1Q relaxation, respectively. All these results are demonstrated experimentally and numerically using the two-site flip motion of dimethyl sulfone and of the nitrobenzene guest in the alpha-p-tert-butylcalix[4]arene-nitrobenzene inclusion compound.

Computer Simulation↗