RESUMO
Far-red cyanobacteriochromes (CBCRs) are bilin-based photosensory proteins that promise to be novel optical agents in optogenetics and deep tissue imaging. Recent structural studies of a far-red CBCR 2551g3 have revealed a unique all-Z,syn chromophore conformation in the far-red-absorbing Pfr state. Understanding the photoswitching mechanism through bilin photoisomerization is important for developing novel biomedical applications. Here, we employ femtosecond spectroscopy and site-directed mutagenesis to systematically characterize the dynamics of wild-type 2551g3 and four critical mutants in the 15Z Pfr state. We captured local relaxations in several picoseconds and isomerization dynamics in hundreds of picoseconds. Most mutants exhibited faster local relaxation, while their twisting dynamics and photoproducts depend on specific protein-chromophore interactions around the D-ring and C-ring. These results collectively reveal a unique dynamic pattern of excited-state evolution arising from a relatively rigid protein environment, thereby elucidating the molecular mechanism of Pfr-state photoisomerization in far-red CBCRs.
Assuntos
Proteínas de Bactérias , Isomerismo , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Cianobactérias/metabolismo , Cianobactérias/química , Mutagênese Sítio-Dirigida , Fotorreceptores Microbianos/química , Fotorreceptores Microbianos/metabolismo , Pigmentos Biliares/química , Pigmentos Biliares/metabolismoRESUMO
Optical control of dynamic processes has been challenging yet has only been demonstrated in several chemical and biological systems. The control of a reaction passing the widely present conical intersection has not been realized. Here, we modulated the phase of the excitation pulse to control the dynamics of ß-carotene through accessing the conical intersection (CI). We observed different dynamics in 110-220 fs into the CI and the consecutive process in 400-600 fs through another CI by various chirped excitation pulses. We successfully controlled those ultrafast wavepacket dynamics passing the CIs on the femtosecond time scales. The method developed here can be used to control a various of ultrafast chemical and biological reactions through the CI(s).