Ultrafast photoreaction dynamics in protein nanospaces (PNS) as revealed by fs fluorescence dynamics studies on photoactive yellow protein (PYP) and related systems

Ultrafast photoreactions in PNS of PYP have been studied by means of fs fluorescence up conversion method. Conclusions obtained are: (a) Photoreaction in PNS (chromophore twisting) occurs from vibrationally unrelaxed fluorescence state and coherent oscillations in the fluorescence decay curves have been observed for the first time. (b) Comparative studies on fluorescence dynamics of mutants and w.-t. PYP have proved that the w.-t. PYP is best engineered for the ultrafast reaction. (c) The coherent oscillations in the fluorescence decay completely disappeared and the reaction was much slower in the denatured state, demonstrating the supremely important role of PNS for the photoreaction.