Hasnain S S, Evans R W, Garratt R C, Lindley P F
S.E.R.C. Daresbury Laboratory, Warrington, U.K.
Biochem J. 1987 Oct 15;247(2):369-75. doi: 10.1042/bj2470369.
Our previous extended-X-ray-absorption-fine-structure (e.x.a.f.s.) study has shown that the probable iron environment in chicken ovotransferrin involves two low-Z ligands (consistent with phenolate linkages) at 0.185(1) nm and four low-Z ligands at 0.204(1) nm [Garratt, Evans, Hasnain & Lindley (1986) Biochem. J. 233, 479-484]. Herein we provide additional information from the e.x.a.f.s. and near-edge structure suggestive of a decrease in the co-ordination number of ovotransferrin-bound iron upon freeze-drying. These effects are reversible, and exposure of the freeze-dried material to a humid atmosphere results in reversion to the solution spectra. Progressive rehydration was monitored by using e.p.r. spectroscopy and was confirmed by recording the high-resolution X-ray-absorption near-edge structure (x.a.n.e.s.). The results suggest the presence of a labile water molecule at the iron-binding sites of ovotransferrin in solution.
我们之前的扩展X射线吸收精细结构（EXAFS）研究表明，鸡卵转铁蛋白中可能的铁环境涉及两个距离为0.185(1) nm的低Z配体（与酚盐键一致）和四个距离为0.204(1) nm的低Z配体[加勒特、埃文斯、哈斯奈因和林德利（1986年）《生物化学杂志》233卷，479 - 484页]。在此，我们提供来自EXAFS和近边结构的更多信息，表明冻干后卵转铁蛋白结合铁的配位数减少。这些效应是可逆的，将冻干材料暴露于潮湿气氛中会使其恢复为溶液光谱。通过电子顺磁共振光谱监测逐步复水过程，并通过记录高分辨率X射线吸收近边结构（XANES）加以证实。结果表明，溶液中的卵转铁蛋白铁结合位点存在一个不稳定的水分子。
