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通过¹H NMR弛豫测量得到的兔晶状体蛋白质上水分子表面扩散的证据。

Evidence of surface diffusion of water molecules on proteins of rabbit lens by 1H NMR relaxation measurements.

作者信息

Bodurka J, Buntkowsky G, Gutsze A, Limbach H H

机构信息

Department of Biophysics, Medical School of Bydgoszcz, Poland.

出版信息

Z Naturforsch C J Biosci. 1996 Jan-Feb;51(1-2):81-90. doi: 10.1515/znc-1996-1-215.

Abstract

In this work, we propose a relaxation model for the interpretation of NMR proton spinlattice and spin-spin relaxation times of mammalian lenses. The framework for this model is based on nuclear magnetic spin-lattice relaxation measurements as a function of temperature at different Larmor frequencies for whole rabbit lenses and fragments of the lens. According to this model, two different dynamic processes of the water molecules determine the relaxation behaviour, namely rotational diffusion and translational surface diffusion. These dynamic processes in conjunction with a two site exchange model give a good explanation of all the measured relaxation data. From the experimental data, we were able to obtain the activation parameters for rotational and translational diffusion of bound lens water. Correlation times of 2.1 x 10(-11) sec and 2.5 x 10(-9) sec and activation energies of 20.5 kJ/mol and 22.5 kJ/mol respectively were found at 308K. At low Larmor frequencies (< or = 100 MHz) the longitudinal relaxation is mainly determined by translational surface diffusion of bound water with a mean square displacement of 1.5 nm, whereas at higher frequencies (> or = 300 MHz), rotational diffusion is the main relaxation mechanism. The spin-spin relaxation is determined by translational diffusion over the whole frequency range and therefore shows only a very small dispersion. By our model it is possible to explain: 1) the strikingly large difference between the T1 value and the T2A and T2B values observed in the lens and 2) the different values of the activation energies measured at different fields for the lens.

摘要

在这项工作中,我们提出了一个弛豫模型,用于解释哺乳动物晶状体的核磁共振质子自旋晶格弛豫时间和自旋 - 自旋弛豫时间。该模型的框架基于对整个兔晶状体及其碎片在不同拉莫尔频率下随温度变化的核磁共振自旋晶格弛豫测量。根据该模型,水分子的两种不同动态过程决定了弛豫行为,即旋转扩散和平动表面扩散。这些动态过程与双位点交换模型相结合,很好地解释了所有测量的弛豫数据。从实验数据中,我们能够获得结合在晶状体中的水的旋转和平动扩散的活化参数。在308K时,分别发现相关时间为2.1×10⁻¹¹秒和2.5×10⁻⁹秒,活化能分别为20.5 kJ/mol和22.5 kJ/mol。在低拉莫尔频率(≤100 MHz)下,纵向弛豫主要由结合水的平动表面扩散决定,其均方位移为1.5 nm,而在较高频率(≥3 MHz)下,旋转扩散是主要的弛豫机制。自旋 - 自旋弛豫在整个频率范围内由平动扩散决定,因此仅显示出非常小的色散。通过我们的模型可以解释:1)在晶状体中观察到的T1值与T2A和T2B值之间显著的巨大差异;2)在不同场强下测量的晶状体活化能的不同值。

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