Untitled

Abstract

Relaxation measurements of side-chain 13CH2-groups of uniformly 13C labeled human ubiquitin were performed at 600 MHz and 800 MHz magnetic field strength at 30 degrees C. Dipole-dipole cross-correlated relaxation effects in T1 experiments were suppressed by the combination of radio-frequency pulses and pulsed field gradients during the relaxation delay leading to monoexponential relaxation decays that allow a more accurate extraction of the 13C T1 relaxation times. Heteronuclear [1H]-13C NOEs obtained by using different proton saturation schemes indicate that the influence of cross-correlation is small. The experimental T1 and NOE data were interpreted in a model-free way in terms of a generalized order parameter and an internal correlation time.

Protein Side-Chain Dynamics and Residual Conformational Entropy

“…55 Resolution of these difficulties requires further development of methods for direct detection of methylene conformational dynamics, which hitherto have been limited to relatively small proteins (<15 kDa). [56][57][58][59][60]…”

Relaxation Rates of Degenerate 1H Transitions in Methyl Groups of Proteins as Reporters of Side-Chain Dynamics

“…[7][8][9][10] One of the most interesting and important areas of study as related to proteins involves side-chain dynamics that play an important role in stability, molecular recognition, catalysis, and ligand binding. [11][12][13][14][15] Over the past decade, NMR experiments for the study of such motional processes have emerged, 12,[16][17][18][19][20][21][22] in addition to new computational approaches that incorporate "dynamic" information into the calculation of protein structures. 23 NMR studies of side-chain dynamics frequently make use of the deuteron as a spin-spy probe of motion since 2 H spin relaxation is dominated by the well-understood quadrupolar interaction.…”

“…A complete description of molecular structure is based not only on static molecular images obtained by X-ray diffraction, NMR spectroscopy, and now cryo-EM techniques − but must also include information that relates to how conformations change in time due to molecular dynamics. − In this regard, NMR spectroscopy has emerged as a valuable probe since experiments have been developed that can be used to study motion over a very broad range of time scales. − One of the most interesting and important areas of study as related to proteins involves side-chain dynamics that play an important role in stability, molecular recognition, catalysis, and ligand binding. − Over the past decade, NMR experiments for the study of such motional processes have emerged, ,− in addition to new computational approaches that incorporate “dynamic” information into the calculation of protein structures …”

Rapid1H{13C}-Resolved Diffusion and Spin-Relaxation Measurements by NMR Spectroscopy

“…In this way, Hadamard-encoding can be used to measure 13 C T 2 relaxation by adapting a CPMG-based pulse sequence using 1 H π pulses to suppress cross-correlation effects, , as shown in Figure b. As a second example, a recently published pulse sequence, optimized for the measurement of T 1 relaxation times in AX 2 systems (such as − C H 2 − groups), was modified to include Hadamard encoding, as shown in Figure b. In this pulse sequence, a refocused INEPT sequence followed by a 13 C π/2 pulse is used to generate S z magnetization, which then relaxes during the following delay period τ.…”

“…Heteronuclear-resolved 13 C T 1 relaxation times were measured by using a pulse sequence proposed by Jin et al . In this pulse sequence, a sandwich of four π/2 pulses and four gradient pulses is repeated during the relaxation time to remove the effects of cross-correlations. For these 13 C T 1 measurements, the relaxation times were varied between 200 ms and 10 s with 1 H π pulses applied every 10 ms.…”