Nuclear vibrational spectroscopy of iron sulfur enzymes and nitrogenase

ANYL 262

Hongxin Wang, hongxin@popper.lbl.gov1, Yuming Xiao, yxiao@ucdavis.edu1, Yisong Guo1, Simon J. George2, Matt Smith1, and Stephen P. Cramer, spjcramer@mac.com1. (1) Department of Applied Sciences, UC Davis, MS 6-2100, 1 Cyclotron Rd., Berkeley, CA 94720, (2) Lawrence Berkeley National Laboratory, Berkeley, CA 94720
Nuclear resonance vibrational spectroscopy (NRVS) is a modern synchrotron radiation based technique. Similar to laser induced fluorescence spectroscopy (LIFS), it involves pumping a sample with 1 meV resolution X-ray beam near a Mossbauer resonance, and probing the delayed fluorescence as a function of excited energy.

When apply to iron samples, it is sensitive and only sensitive to all the vibrational modes involving a 57Fe site motion. In this study, we used 57Fe NRVS to study the vibrational modes inside various fe-S enzymes, such as rubredoxin, ferredoxin, FeMo-cofactor and nitrogenase, which catalyzes the nitrogen fixation.

The catalytic site FeMo-cofactor exhibits a strong signal near 190 cm-1, where conventional Fe-S clusters have weak NRVS. This intensity is ascribed to cluster breathing modes whose frequency is raised by an interstitial atom. Our work is the first spectroscopic information on this issue.

FTIR and resonance Raman spectroscopy were also used to assist the analysis of the Fe-S vibrational modes.

 

Analytical Approaches, Spectroscopy
8:30 AM-12:00 PM, Wednesday, 13 September 2006 Moscone Center -- Room 124, Oral

Division of Analytical Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006