Research    

The subject of my research is heme proteins and heme compounds, namely the connection between their structure, dynamics and functions. The experiments are performed at Argonne National Laboratory using relatively new x-ray synchrotron technique - Nuclear Resonance Vibrational Spectroscopy (NRVS), which was designed for Mossbauer nuclei, in our case - ⁵⁷Fe. If a vibrational mode has energy equal to the difference between the x-ray beam and the ⁵⁷Fe nuclear resonance (14.4 keV), the resonance can be excited, and subsequent deexcitation can be detected as Fe fluorescence. By monitoring this fluorescence as the x-ray energy is scanned through the resonance, Fe vibrational density of states can be obtained.

To characterize vibrational density of states spectrum Normal Mode Analysis (NMA) calculations are performed for heme compounds. We treat a compound as a set of balls and springs, introduce a force field and vary force constants until there is a good fit between experimental NRVS data and NMA calculations. Although the problem is extremely underdetermined, there is a number of constraints such as typical force constant value or symmetry considerations which have to be taken into account during the refinement process. 

Due to computer limitations, NMA can not be performed on the whole protein molecule, instead we do it for heme site only; however, heme site dynamics is highly correlated with the whole protein molecule motion. Thus, we can, at least partially, try to answer the question about the correlation between structure, dynamics and functions of heme proteins.

Selected Abstracts

Valeria Starovoitova et al, Vibrational Spectroscopy and Normal Mode Analysis of Fe(II)octaethylporphyrin [PDF]

Valeria Starovoitova et al, Nuclear Resonance Vibrational Spectroscopy as a probe of iron dynamics in heme proteins and heme compounds  [PDF]

Valeria Starovoitova, Intermolecular dynamics in crystalline iron octaethylporphyrin (FeOEP) [PDF]