Time-resolved photoacoustics (PA) is uniquely able to explore the energy landscape of photoactive proteins and concomitantly detects light-induced volumetric changes (ΔV) accompanying the formation and decay of transient species in a time window between ca. 20 ns and 5 μs. Here, we report PA measurements on diverse photochromic bilin-binding photoreceptors of prokaryotic origin: (1) the chromophore-binding GAF3 domain of the red (R)/green (G) switching cyanobacteriochrome 1393 (Slr1393g3) from Synechocystis; (2) the red/far red (R/FR) Synechocystis Cph1 phytochrome; (3) full-length and truncated constructs of Xanthomonas campestris bacteriophytochrome (XccBphP), absorbing up to the NIR spectral region. In almost all cases, photoisomerization results in a large fraction of energy dissipated as heat (up to 90%) on the sub-ns scale, reflecting the low photoisomerization quantum yield (<0.2). This "prompt" step is accompanied by a positive ΔV1  = 5-12.5 mL mol(-1) . Formation of the first intermediate is the sole process accessible to PA, with the notable exception of Slr1393g3-G for which ΔV1  = +4.5 mL mol(-1) is followed by a time-resolved, energy-conserving contraction ΔV2  = -11.4 mL mol(-1) , τ2  = 180 ns at 2.4°C. This peculiarity is possibly due to a larger solvent occupancy of the chromophore cavity for Slr1393g3-G.

Time-Resolved Energetics of Photoprocesses in Prokaryotic Phytochrome-Related Photoreceptors / Losi, Aba; Bonomi, Hernán R; Michael, Norbert; Tang, Kun; Zhao, Kai-Hong. - In: PHOTOCHEMISTRY AND PHOTOBIOLOGY. - ISSN 0031-8655. - 93:3(2017), pp. 733-740. [10.1111/php.12728]

Time-Resolved Energetics of Photoprocesses in Prokaryotic Phytochrome-Related Photoreceptors

LOSI, Aba;
2017

Abstract

Time-resolved photoacoustics (PA) is uniquely able to explore the energy landscape of photoactive proteins and concomitantly detects light-induced volumetric changes (ΔV) accompanying the formation and decay of transient species in a time window between ca. 20 ns and 5 μs. Here, we report PA measurements on diverse photochromic bilin-binding photoreceptors of prokaryotic origin: (1) the chromophore-binding GAF3 domain of the red (R)/green (G) switching cyanobacteriochrome 1393 (Slr1393g3) from Synechocystis; (2) the red/far red (R/FR) Synechocystis Cph1 phytochrome; (3) full-length and truncated constructs of Xanthomonas campestris bacteriophytochrome (XccBphP), absorbing up to the NIR spectral region. In almost all cases, photoisomerization results in a large fraction of energy dissipated as heat (up to 90%) on the sub-ns scale, reflecting the low photoisomerization quantum yield (<0.2). This "prompt" step is accompanied by a positive ΔV1  = 5-12.5 mL mol(-1) . Formation of the first intermediate is the sole process accessible to PA, with the notable exception of Slr1393g3-G for which ΔV1  = +4.5 mL mol(-1) is followed by a time-resolved, energy-conserving contraction ΔV2  = -11.4 mL mol(-1) , τ2  = 180 ns at 2.4°C. This peculiarity is possibly due to a larger solvent occupancy of the chromophore cavity for Slr1393g3-G.
Time-Resolved Energetics of Photoprocesses in Prokaryotic Phytochrome-Related Photoreceptors / Losi, Aba; Bonomi, Hernán R; Michael, Norbert; Tang, Kun; Zhao, Kai-Hong. - In: PHOTOCHEMISTRY AND PHOTOBIOLOGY. - ISSN 0031-8655. - 93:3(2017), pp. 733-740. [10.1111/php.12728]
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11381/2824416
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