Modeling molecular requires validation of any significant conclusions by experimental techniques. In particular, both accurate and precise distance measurements have to be made at the subnanometer scale. For this reason, spectroscopic techniques such as NMR and EPR are necessary auxillaries to molecular modeling and molecular dynamics simulations.

We have utilized these techniques in studies of the rhodopsin/transducin system of signal transduction. Rhodopsin is the prototypical G-protein coupled receptor and transducin is its G-protein partner in vision. The structure of the C-terminal recognition motif of the alpha subunit of transducin was determined by transfer NMR (Kisselev.pdf, O.G., Kao, J., Ponder, J.W., Fann, Y.C., Gautam, N., and Marshall, G.R. 1998. Light-activated rhodopsin induces structural binding motif in G protein alpha subunit. Proc Natl Acad Sci USA 95(8): 4270-4275). More recently, DEER EPR spectroscopy was used to estimate the entropy of peptide binding to photoactivated rhodopsin (Van Eps.pdf, N., Anderson, L.L., Kisselev, O.G., Baranski, T.J., Hubbell, W.L., and Marshall, G.R. 2010. EPR Studies of Functionally Active, Nitroxide Spin-Labeled Analogs of the C-Terminus of a G-Protein Alpha Subunit. Biochemistry in press).

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