Matthew Ranaghan - Photochemical and thermal stability of green and blue proteorhodopsins: implications for protein-based bioelectronic devices.

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      Publication Details (including relevant citation   information):

      Ranaghan, M.   J., Shima, S., Ramos, L., Poulin, D. S., Whited, G.,   Rajasekaran, S., Stuart, J. A., Albert, A. D., Birge, R. R.   (2010) J. Phys. Chem.   B 144 (44): 14064-70. (DOI: 10.1021/jp106633w)


      The photochemical and thermal stability of the   detergent-solubilized blue- and green-absorbing proteorhodpsins,   BPR and GPR, respectively, are investigated to determine the   viability of these proteins for photonic device applications.   Photochemical stability is studied by using pulsed laser   excitation and differential UV-vis spectroscopy to assign the   photocyclicity. GPR, with a cyclicity of 7 × 10(4) photocycles   protein(-1), is 4-5 times more stable than BPR (9 × 10(3)   photocycles protein(-1)), but is less stable than native   bacteriorhodopsin (9 × 10(5) photocycles protein(-1)) or the   4-keto-bacteriorhodopsin analogue (1 × 10(5) photocycles   protein(-1)). The thermal stabilities are assigned by using   differential scanning calorimetry and thermal bleaching   experiments. Both proteorhodopsins display excellent thermal   stability, with melting temperatures above 85 °C, and remain   photochemically stable up to 75 °C. The biological relevance of   our results is also discussed. The lower cyclicity of BPR is   found to be adequate for the long-term biological function of the   host organism at ocean depths of 50 m or more.

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