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Paper by Rousso et al., PNAS 1997 Presented by Matt Gethers 11/20/08

Microsecond atomic force sensing of protein conformational dynamics: Implications for the primary light-induced events of bacteriorhodopsin. Paper by Rousso et al., PNAS 1997 Presented by Matt Gethers 11/20/08. Are protein conformational change and charge redistribution related?.

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Paper by Rousso et al., PNAS 1997 Presented by Matt Gethers 11/20/08

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  1. Microsecond atomic force sensing of protein conformational dynamics: Implications for the primary light-induced events of bacteriorhodopsin Paper by Rousso et al., PNAS 1997 Presented by Matt Gethers 11/20/08

  2. Are protein conformational change and charge redistribution related? • The leading hypothesis is that protein conformational change is initiated through isomerization around the C13=C14 bond of the chromophore. • Rousso et al. investigated through AFS the hypothesis that light-induced conformational change is initiated through a polarization of the chromophore.

  3. Atomic Force Sensing

  4. AFS detects conformational change of bR on microsecond scale • After exciting membrane with 532 nm light, AFS data indicates expansion of membrane.

  5. AFS data agrees with known choromophore specificity and photocycle • Exciting membrane with different wavelengths of light shows a peak response ~532 nm. • An initial pulse of 532 nm followed by a secondary pulse shows peak response at ~410 nm, the characteristic absorption of the M intermediate.

  6. AFS data suggests redistribution of charge in chromophore upon excitation

  7. AFS detects changes not observable by absorption spectroscopy • Data from AFS measurements indicate conformational changes even in molecules incapable of undergoing C13=C14 isomerization. • Perhaps the conformational changes detected through AFS become physiologically relevant only if isomerization is possible.

  8. AFS makes possible the ability to sense upstream events • Absorption spectroscopy requires all steps in fluorescence to occur to measure activity. • AFS offers a means of sensing upstream (biomechanical) steps in the fluorescence pathway – allows us to decompose the process with greater resolution.

  9. Questions ?

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