成人正常血红蛋白中组氨酸残基的质子纵向弛豫研究
Proton longitudinal relaxation investigation of histidyl residues in human normal adult hemoglobin.
作者信息
Russu I M, Ho C
出版信息
Biophys J. 1982 Aug;39(2):203-10. doi: 10.1016/S0006-3495(82)84509-8.
The longitudinal relaxation of the C2 protons of surface histidyl residues as well as other aromatic protons of human normal adult deoxyhemoglobin investigated at 360 MHz is discussed in terms of the theory proposed by Kalk and Berendsen for the proton longitudinal relaxation in proteins (Kalk, A., and H.J.C. Berendsen. 1976. J. Magn. Reson. 24:343-366). The role of the four paramagnetic iron atoms of deoxyhemoglobin as fast-relaxing sinks for the overall proton longitudinal relaxation is evaluated according to the model proposed by Bloembergen for the relaxation of nuclei in crystals containing paramagnetic centers (Bloembergen, N. 1949. Physica. 15:386-426). The results suggest that the effectiveness of the paramagnetic iron atoms of deoxyhemoglobin for the overall proton longitudinal relaxation is reduced as a result of slower spin diffusion and wide distribution of methyl groups within the hemoglobin molecule. Thus, deoxyhemoglobin provides a good model for investigating the influence of cross relaxation on proton longitudinal relaxation in proteins at the slow motion limit and in the presence of paramagnetic centers. For the C2 protons of surface histidyl residues, we show that the cross relaxation resulting from the interresidue dipolar interaction makes an important contribution to their longitudinal relaxation.
依据卡尔克（Kalk）和贝伦森（Berendsen）提出的蛋白质中质子纵向弛豫理论（卡尔克，A.，以及H.J.C. 贝伦森。1976年。《磁共振杂志》24卷：343 - 366页），探讨了在360兆赫下对人类正常成人脱氧血红蛋白表面组氨酸残基的C2质子以及其他芳香族质子的纵向弛豫情况。根据布洛姆伯根（Bloembergen）提出的含有顺磁中心晶体中原子核弛豫模型（布洛姆伯根，N. 1949年。《物理学》15卷：386 - 426页），评估了脱氧血红蛋白的四个顺磁铁原子作为质子整体纵向弛豫的快速弛豫汇的作用。结果表明，由于自旋扩散较慢以及血红蛋白分子内甲基分布广泛，脱氧血红蛋白的顺磁铁原子对质子整体纵向弛豫的有效性降低。因此，脱氧血红蛋白为研究在慢运动极限且存在顺磁中心时交叉弛豫对蛋白质中质子纵向弛豫的影响提供了一个良好的模型。对于表面组氨酸残基的C2质子，我们表明，由残基间偶极相互作用导致的交叉弛豫对其纵向弛豫有重要贡献。
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