Saturday, October 06, 2007

Hiyam's Journal Update

J. Am. Chem. Soc., ASAP Article 10.1021/ja073234s S0002-7863(07)03234-9
Combined Analysis of 15N Relaxation Data from Solid- and Solution-State NMR Spectroscopy
Veniamin Chevelkov, Anastasia V. Zhuravleva, Yi Xue, Bernd Reif, and Nikolai R. Skrynnikov

It is well-known that structures of globular proteins in liquid and in crystalline solid are essentially identical. Many lines of evidence suggest that internal dynamics are also similar (assuming that the solid sample is well-hydrated and the measurements are conducted at the same temperature). On the basis of this premise, we undertake a combined analysis of solid- and liquid-state 15N relaxation data from a small globular protein, -spectrin SH3 domain. The interpretation using the extended Lipari-Szabo model demonstrates that liquid R1, R2, NOE, and solid R1 data measured at multiple fields are mutually consistent. To validate these results, we prepared a series of samples where the protein is dissolved in a water-glycerol solvent. The presence of glycerol ensures that the overall protein tumbling is slowed, thus increasing the visibility of nanosecond time-scale internal motions. When additional data are included in the fitting procedure, a credible picture of protein dynamics is obtained. In particular, the analysis suggests that ns time-scale motions with very low amplitude, S2 0.95, are present throughout the protein. It is envisaged that combined analyses of liquid- and solid-state data can provide an efficient method for detailed characterization of internal dynamics in proteins at multiple time scales.

J. Am. Chem. Soc., ASAP Article 10.1021/ja075846i S0002-7863(07)05846-5
Probing Supramolecular Structure from Measurement of Methyl 1H-13C Residual Dipolar Couplings
Remco Sprangers and Lewis E. Kay

A simple NMR experiment is presented for the measurement of methyl 1H-13C residual dipolar couplings in fractionally aligned supramolecular protein complexes. The approach makes use of methyl-TROSY spectroscopy that significantly increases the lifetime of the NMR signal, along with highly deuterated, methyl-protonated samples that minimize relaxation contributions from protons external to the methyl group probes. An application to a 360 kDa half-proteasome complex is presented, establishing the methodology.

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