Molecular basis of water proton relaxation in gels and tissue
Molecular basis of water proton relaxation in gels and tissue
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DOI：
10.1002/mrm.20912
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发表时间：
2006-07-01
影响因子：
3.3
通讯作者：
Halle, Bertil
中科院分区：
文献类型：
--
作者：
Chavez, Fabian Vaca;Halle, Bertil
一组广泛的水-H磁弛豫分散（MRD）的数据，提出了水琼脂糖和明胶凝胶。结果表明，EMOR模型，这是在一个配套文件，这项研究的发展（见Halle，本期），解释了水-H自旋-晶格弛豫速率对四十多年来共振频率和pH值的依赖性。从H-1 MRD数据分析中推导出的参数值与从相同凝胶的H-2 MRD曲线中推导出的值一致，分子参考数据。该协议表明，水-H-1弛豫分散在水性生物聚合物凝胶中直接产生的内部水分子或不稳定的生物聚合物质子的交换介导的取向随机化，很少或没有集体生物聚合物振动或相干自旋扩散所发挥的作用。这种普遍存在的机制被认为是水-H-1自旋晶格弛豫的主要来源，在低磁场下，在所有的水溶液系统与旋转固定的生物聚合物，包括生物组织。相同的机制也有助于横向和双帧弛豫和磁化转移在高场。
An extensive set of water-H magnetic relaxation dispersion (MRD) data are presented for aqueous agarose and gelatin gels. It is demonstrated that the EMOR model, which was developed in a companion paper to this study (see Halle, this issue), accounts for the dependence of the water-H spin-lattice relaxation rate on resonance frequency over more than four decades and on pH. The parameter values deduced from analysis of the H-1 MRD data are consistent with values derived from H-2 MRD profiles from the same gels and with small-molecule reference data. This agreement indicates that the water-H-1 relaxation dispersion in aqueous biopolymer gels is produced directly by exchange-mediated orientational randomization of internal water molecules or labile biopolymer protons, with little or no role played by collective biopolymer vibrations or coherent spin diffusion. This ubiquitous mechanism is proposed to be the principal source of water-H-1 spin-lattice relaxation at low magnetic fields in all aqueous systems with rotationally immobile biopolymers, including biological tissue. The same mechanism also contributes to transverse and rotating-frame relaxation and magnetization transfer at high fields.