In biological photoreceptors, the energy stored in early transient species is a key feature to drive the photocycle or a chain of reactions. Time-resolved photoacoustics (PA) can explore the energy landscape of transient species formed within few ns after photoexcitation, as well as volumetric changes (Delta V) of these intermediates with respect to the parental state. In this work, PA identified these important parameters for several channelrhodopsins, namely CaChR1 from Chlamydomonas augustae and CrChR2 from Chlamydomonas reinhardtii and various variants. PA has access to the sub-ns formation of the early photoproduct P1 and to its relaxation, provided that this latter process occurs within a few mu s. We found that Delta V-P1 for CaChR1 is ca. 12 mL/mol, while it is much smaller for CrChR2 (4.7 mL/mol) and for H. salinarum bacteriorhodopsin (HsBR, Delta V-K = 2.8 mL/mol). PA experiments on variants strongly indicate that part of this large Delta V-P1 value for CaChR1 is caused by the protonation dynamics of the Schiff base counterion complex involving E169 and D299. PA data further show that the energy level of P1 is higher in CrChR2 (ca. 96 kJ/mol) than in CaChr1 (ca. 46 kJ/mol), comparable to the energy level of the K state of HsBR (60 kJ/mol). Instrumental to gain these molecular values from the raw PA data was the estimation of the quantum yield (Phi) for P1 formation via transient spectroscopy; for both channelrhodopsins, Phi(P2) was evaluated as ca. 0.4.

Time-resolved photoacoustics of channelrhodopsins: early energetics and light-driven volume changes / Walter, Maria; Schubert, Luiz; Heberle, Joachim; Schlesinger, Ramona; Losi, Aba. - In: PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES. - ISSN 1474-905X. - 22:(2023), pp. 477-486. [10.1007/s43630-022-00327-8]

Time-resolved photoacoustics of channelrhodopsins: early energetics and light-driven volume changes

Heberle, Joachim
Resources
;
Losi, Aba
Investigation
2023-01-01

Abstract

In biological photoreceptors, the energy stored in early transient species is a key feature to drive the photocycle or a chain of reactions. Time-resolved photoacoustics (PA) can explore the energy landscape of transient species formed within few ns after photoexcitation, as well as volumetric changes (Delta V) of these intermediates with respect to the parental state. In this work, PA identified these important parameters for several channelrhodopsins, namely CaChR1 from Chlamydomonas augustae and CrChR2 from Chlamydomonas reinhardtii and various variants. PA has access to the sub-ns formation of the early photoproduct P1 and to its relaxation, provided that this latter process occurs within a few mu s. We found that Delta V-P1 for CaChR1 is ca. 12 mL/mol, while it is much smaller for CrChR2 (4.7 mL/mol) and for H. salinarum bacteriorhodopsin (HsBR, Delta V-K = 2.8 mL/mol). PA experiments on variants strongly indicate that part of this large Delta V-P1 value for CaChR1 is caused by the protonation dynamics of the Schiff base counterion complex involving E169 and D299. PA data further show that the energy level of P1 is higher in CrChR2 (ca. 96 kJ/mol) than in CaChr1 (ca. 46 kJ/mol), comparable to the energy level of the K state of HsBR (60 kJ/mol). Instrumental to gain these molecular values from the raw PA data was the estimation of the quantum yield (Phi) for P1 formation via transient spectroscopy; for both channelrhodopsins, Phi(P2) was evaluated as ca. 0.4.
2023
Time-resolved photoacoustics of channelrhodopsins: early energetics and light-driven volume changes / Walter, Maria; Schubert, Luiz; Heberle, Joachim; Schlesinger, Ramona; Losi, Aba. - In: PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES. - ISSN 1474-905X. - 22:(2023), pp. 477-486. [10.1007/s43630-022-00327-8]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11381/2931777
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