Time-resolved X-ray absorption determination of structural changes following photoinduced electron transfer within bis-porphyrin heme protein models

被引:26
作者
Chen, LX
Lee, PL
Gosztola, D
Svec, WA
Montano, PA
Wasielewski, MR
机构
[1] Argonne Natl Lab, Div Chem, Argonne, IL 60439 USA
[2] Argonne Natl Lab, Expt Facil Div, Argonne, IL 60439 USA
[3] Argonne Natl Lab, Div Sci Mat, Argonne, IL 60439 USA
[4] Northwestern Univ, Dept Chem, Evanston, IL 60208 USA
来源
JOURNAL OF PHYSICAL CHEMISTRY B | 1999年 / 103卷 / 16期
关键词
D O I
10.1021/jp990056j
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Time domain energy dispersive X-ray absorption spectroscopy provides a powerful probe of changes in molecular structure that occur during photoinduced electron transfer reactions. In this study a diporphyrin model for electron transfer within modified heme proteins is examined using this technique. Transient optical absorption experiments show that photoinduced electron transfer from the lowest excited triplet state of a Zn, porphyrin attached at a fixed 25 Angstrom distance by means of a long spacer molecule to an Fe(III) porphyrin occurs with a 6 ms time constant at 77 K. Time domain X-ray absorption measurements are consistent with transient reduction of Fe(III) to Fe(II) that is accompanied by substantial weakening of the bond between the Fe atom and a pyridine molecule ligated to it. Coupling of ligand loss to reduction of Fe(III) to Fe(II) provides a means of stabilizing the reduced intermediate.
引用
收藏
页码:3270 / 3274
页数:5
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