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. 2021 Oct 22;12(11):7082-7091.
doi: 10.1364/BOE.441118. eCollection 2021 Nov 1.

Mammalian complex III heme dynamics studied with pump-probe spectroscopy and red light illuminations

Sean P O'Connor  1 , Samantha M Powell  2   3 , John M Rickman  4 , Nathaniel J Pope  4   5 , Gary D Noojin  4 , Marlan O Scully  1   6 , Michael L Denton  7   8 , Vladislav V Yakovlev  1   9   10
Affiliations

Mammalian complex III heme dynamics studied with pump-probe spectroscopy and red light illuminations

Sean P O'Connor et al. Biomed Opt Express. .

Abstract

The electronic or molecular mechanisms that initiate photobiomodulation (PBM) in cells are not yet fully understood. The porcine complex III (C-III) of the electron transport chain was characterized with transient absorption spectroscopy (TAS). We then applied our recently developed continuous wave laser coupled TAS procedure (CW-TAS) to investigate the effect of red light irradiances on the heme dynamics of C-III in its c1 reduced state. The time constants were found to be 3.3 ± 0.3 ps for vibrational cooling of the oxidized state and 4.9 ± 0.4 ps for rebinding of the photodissociated axial ligand of the c1 reduced state. The analysis of the CW-TAS procedure yielded no significant changes in the C-III heme dynamics. We rule out the possibility of 635 nm CW light at 4.7 mW/cm2 inducing a PBM effect on the heme dynamic of C-III, specifically with the photodissociation of its axial ligand.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Fig. 1.
Fig. 1.
Supercontinuum spectra generated from the sapphire window.
Fig. 2.
Fig. 2.
Ground state absorbance spectra for C-III measured in its initial oxidized state (black) and after sodium dithionite-treatment (red). Inset plot displays a magnified view of the Q bands.
Fig. 3.
Fig. 3.
Transient absorption spectra of oxidized C-III with 418 nm excitation at 200 nJ/pulse displayed as (a) a surface and (b) spectral cross sections at the constrained time-delay range used for global analysis. Also provided are the first two (c) spectral components and (d) kinetic components from SVD analysis.
Fig. 4.
Fig. 4.
Transient absorption spectra of SDT-C-III with 418 nm excitation at 200 nJ/pulse displayed as (a) a surface and (b) spectral cross sections at the constrained time-delay range used for global analysis. Also provided are the first two (c) spectral components and (d) kinetic components from SVD analysis.
Fig. 5.
Fig. 5.
First principal spectral components from SVD analysis on each of the nine TAS surfaces for the (a) control and (b) CW irradiance collections on SDT-C-III.
See this image and copyright information in PMC

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