Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Rischel, C; Jorgensen, LE; Foldes-Papp, Z.
Microsecond structural fluctuations in denatured cytochrome c and the mechanism of rapid chain contraction
J PHYS-CONDENS MATTER 2003 15: S1725-S1725.
Doi: 10.1088/0953-8984/15/18/306
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- Földes-Papp Zeno
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- Abstract:
- In order to improve the understanding of the diffusive chain movements leading to protein folding, we have studied microsecond conformational fluctuations in denatured yeast cytochrome c by fluorescence correlation spectroscopy (FCS). We show that emitted fluorescence from the dye Alexa-488 chemically attached to the protein depends on the extension of the chain, such that fluctuations in chain length will give fluctuations in fluorescence intensity. Exposure to chemical denaturants leads to an increase in diffusion times, indicating expansion of the molecule. Structural fluctuations of the unfolded protein give rise to fluctuations in the emitted fluorescence. However, FCS measurements fail to show conformational fluctuations of chain segments, establishing an upper bound of 4 mus on the timescale of chain fluctuations in the denatured state. This clearly shows that an early process with a time constant of 50 mus observed in folding experiments must involve passage of a free energy barrier, and cannot be barrierless chain collapse as has been proposed.