A Moessbauer spectrometer for the study of natural abundance iron proteins.

Abstract

A wide angle Mossbauer spectrometer has been constructed that permits study of natural abundance $\sp{57}$Fe (2.19%) biological samples with a sensitivity of about 10 times better than that of existing spectrometers. This is achieved by using 77 argon gas proportional counters, instead of the single counter conventionally used, to increase the number of detected $\gamma$-rays by roughly a factor of one hundred. By using a type II servo amplifier feedback circuit the $\sp{57}$Fe source velocity drive is able to maintain reproducible velocities with a precision of $\pm$0.001 mm/sec over periods of several weeks. The velocity is measured with a He-Ne laser Michelson-Morley interferometer. The spectrometer is housed in a dewar such that the source and sample temperatures can be operated stably in the range from 4.2 to 300 K. Overall performance of the spectrometer has been evaluated by a study of an iron calibration foil, and has been found to be completely satisfactory for the study of natural abundance proteins.