The primary photoisomerization dynamics (< 10 ns), both for 15ZPr ? 15EPg and 15EPg ? 15ZPr reactions, between the native (PCB-incorporated) and the engineered (PFB-incorporated) NpR6012g4 and NpF2164g6 cyanobacteriochromes (CBCRs) from Nostoc punctiforme are compared for the first time by femtosecond time-resolved transient absorption spectroscopy. The broadband time-resolved signals were analyzed within a multi-compartment global analysis formalism that fits the data to a model with multiple interconnected populations. For the 15ZPr ? 15EPg reactions, the PFB-incorporated CBCR samples exhibit markedly faster excited-state decay kinetics than the native PCB-incorporating analogues. The PFB-incorporated CBCRs were found to have Lumi-Rf absorption bands that are ~20-nm red-shifted with respect to that of the PCB-incorporated proteins. For the 15EPg ? 15ZPr reactions, both the native and engineered CBCRs exhibit relatively similar excited-state decay kinetics. Moreover, PCBNpR6012g4 is found to be a �Double-Lumi� CBCR that it generates two primary photoproducts (Lumi-Go1 and Lumi-Go2) within the ultrafast timescale (< 10 ns), while PFBNpR6012g4 and both native and engineered NpF2164g6 generate a single Lumi-photoproduct on the same timescale. These modified CBCRs provide a starting point for engineering tunable biological light sensors. 

Chromophoric engineering of the primary photodynamics of red/green photoswitching cyanobacteriochromes from Nostoc punctiforme

247th National Meeting (2014)

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