RT Journal Article
SR Electronic
T1 Bistablity in Fluorescence from a purple non-sulfur bacteria
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 132225
DO 10.1101/132225
A1 Anirban Bose
A1 Sufi O Raja
A1 Sanhita Ray
A1 Anjan Kr Dasgupta
YR 2017
UL http://biorxiv.org/content/early/2017/05/03/132225.abstract
AB Bistability has been observed for photosynthetic purple non-sulfur bacteria Rhodobacter capsulatus SB1003. The microbes respond to UV excitation (at 365nm) in a switchable manner. A time dependent increase in fluorescence (590-685nm) following roughly a first order kinetics is observed at normal temperature (298K). When either concentration or temperature is lowered the state switches to a steady state first order bleaching. Similar bistability is also observed with respect to temperature variations, as amplification occurring at say 298K disappears below 280K. One can synthetically control bistability and force a re-emergence of fluorescence amplification by exposing the system to a static magnetic field (0.25T). Differential excitability of singlet and triplet states and selective sensitivity of triplets to static magnetic field may explain this result. The triplets dominate at low temperature preventing amplification of emission, and the reversal may be caused by the Zeeman splitting of the triplets, wherein the excitable singlets re-emerge. Evolutionary and ecological implication of bistable photosynthetic system is discussed in the text.PACS numbers: 87.18.Fx, 31.50.Df, 33.50.-j,87.50.C-