25-30 August 2019
Henry Ford Building
Europe/Berlin timezone

Broad timescale conformational dynamics: Application of geometric approximation and adiabatic relaxation dispersion

Not scheduled
Harnack House and Henry Ford Building

Harnack House and Henry Ford Building

Board: 58
Poster Posters


Dr R. Andrew Byrd (National Cancer Institute, USA)


Relaxation dispersion techniques are powerful tools to quantitatively characterize the chemical (or conformational) exchange across biologically relevant timescales [Palmer et al, Meth. Enzymol. 2001 & 2019]. Recently, a new type of data analysis, geometric approximation methodology [Chao & Byrd, JACS 2016], has been developed to decipher the complex experimental data associated with the adiabatic relaxation dispersion experiment [Mangia et al. JACS 2010], thus providing the assessment of a very broad range of timescales. The advantages of geometric approximation can also be applied to conventional CPMG experiments, including the use of different exchange models and related problems [Chao & Byrd, JMR 2017, Emerg. Topics Life Sci., 2018].
The original adiabatic relaxation dispersion experiment focused on protein backbone (15NH) dynamics. We have recently extended these methods to methyl groups in the new methyl-geoHARD experiment, combining geometric approximation, adiabatic relaxation dispersion techniques, and methyl TROSY effects [Tugarinov et al. JACS 2003]. Methyl-geoHARD can explore broad timescale conformational dynamics (ranging from 150 sec-1 to 100,000 sec-1) in the hydrophobic cores of large protein complexes.
We illustrate the detection and quantification of a broad distribution of collective motions and local motions of methyl groups within a moderately large enzyme (tauc = 24 ns). The method is quantitatively validated by comparison with the conventional SQ-CPMG [Lundstrom et al., JBNMR 2007] and other experimental data, for sites where the dynamics are within the timescale of both experiments. The technique is developed and optimized to address the large off-resonance effects at ultra-high magnetic fields (> 1GHz) and for large and complex biological systems (up to tauc = 50 ns). Overall, the potentials of geometric approximation methodology enable the analysis of complex relaxation phenomena and simplify the experiments to gain or retain sensitivity in challenging, large molecular weight proteins.

Primary authors

Dr R. Andrew Byrd (National Cancer Institute, USA) Dr Fa-an Chao (National Cancer Institute) Dr Yifei Li (Fosun Pharmaceuticals) Dr Yue Zhang (National Cancer Institute)

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