@article {292,
	title = {Why is THz Sensitive to Protein Functional States? Oxidation State of Cytochrome C},
	journal = {Terahertz Science and Technology},
	volume = {3},
	year = {2010},
	chapter = {149-162},
	abstract = {<p>We investigate the presence of structural collective motions on a picosecond time scale for the heme protein, cytochrome c, as a function of oxidation and hydration, using terahertz (THz) time-domain spectroscopy and molecular dynamics simulations. Structural collective mode frequencies have been calculated to lie in this frequency range, and the density of states can be considered a measure of flexibility. A dramatic increase in the THz response occurs with oxidation, with the largest increase for lowest hydrations and highest frequencies. For both oxidation states the measured THz response rapidly increases with hydration saturating above ~25\% (g H<sub>2</sub>O/g protein), in contrast to the rapid turn-on in dynamics observed at this hydration level for other proteins. Quasi-harmonic collective vibrational modes and dipole-dipole correlation functions are calculated from the molecular dynamics trajectories. The collective mode density of states alone reproduces the measured hydration dependence providing strong evidence of the existence of these collective motions. The large oxidation dependence is reproduced only by the dipole-dipole correlation function, indicating the contrast arises from diffusive motions consistent with structural changes occurring in the vicinity of a buried internal water molecule.</p>},
	doi = {10.11906/TST.149-162.2010.12.15},
	url = {http://www.tstnetwork.org/10.11906/TST.149-162.2010.12.15/},
	author = {He,Y. and Chen, J.-Y. and Knab, J. R. and Zheng, W. and Markelz, A.G.}
}
