Acceleration of the excitation decay in Photosystem I immobilized on glass surface

Abstract

Femtosecond transient absorption was used to study excitation decay in monomeric and trimeric cyanobacterial Photosystem I (PSI) being prepared in three states: (1) in aqueous solution, (2) deposited and dried on glass surface (either conducting or non-conducting), and (3) deposited on glass (conducting) surface but being in contact with aqueous solvent. The main goal of this contribution was to determine the reason of the acceleration of the excitation decay in dried PSI deposited on the conducting surface relative to PSI in solution observed previously using time-resolved fluorescence (Szewczyk et al., Photysnth Res 132(2):111–126, 2017). We formulated two alternative working hypotheses: (1) the acceleration results from electron injection from PSI to the conducting surface; (2) the acceleration is caused by dehydration and/or crowding of PSI proteins deposited on the glass substrate. Excitation dynamics of PSI in all three types of samples can be described by three main components of subpicosecond, 3–5, and 20–26 ps lifetimes of different relative contributions in solution than in PSI-substrate systems. The presence of similar kinetic components for all the samples indicates intactness of PSI proteins after their deposition onto the substrates. The kinetic traces for all systems with PSI deposited on substrates are almost identical and they decay significantly faster than the kinetic traces of PSI in solution. We conclude that the accelerated excitation decay in PSI-substrate systems is caused mostly by dense packing of proteins.Electronic supplementary materialThe online version of this article (doi:10.1007/s11120-017-0454-z) contains supplementary material, which is available to authorized users.

Photovoltaic activity of electrodes based on intact photosystem I electrodeposited on bare conducting glass

“…Cyanobacterial PSI immobilized directly on FTO conducting glass has recently been shown by ultrafast optical spectroscopy to preserve excitation quenching properties very similar to those of the native PSI in solution (Szewczyk et al 2017(Szewczyk et al , 2018. The detailed analysis has shown that the observed modest acceleration of the excitation decay in immobilized PSI (by a few ps) may be assigned to the crowding effect similar to that reported for aggregated LHCII (Ruban et al 2007).…”

“…In the following, we present photovoltaic data obtained from the system containing simple PSI-FTO photoelectrode identical to that one described in Szewczyk et al (2017Szewczyk et al ( , 2018 and propose a mechanism of the anodic and cathodic photocurrent generation in this system. The advantage of this system is the functionality of immobilized PSI proven to be highly intact at the level of excitation decay and charge separation.…”

“…Time-resolved absorption data were collected using 1 kHz pump-probe Helios system (Ultrafast Systems), described in detail previously (Szewczyk et al 2018). Shortly, the excitation pulses (800 nm, ~ 200 fs wide, FWHM) were generated in the Ti:Sapphire oscillator (Mai-Tai, Spectra Physics), then amplified in the regenerative amplifier (Spitfire Ace, Spectra Physics), and tuned in the optical parametric amplifier to 650 nm (Topas Prime, Spectra Physics).…”

“…What differs various PSI-containing photoelectrodes described in the literature is: (1) the substrate on which PSI is deposited, (2) the method of PSI immobilization on the substrate, (3) the way by which the electric contact between PSI and the substrate as well as between PSI and the counter electrode is achieved, (4) the species from which the PSI is extracted and the type of the PSI preparation. The electrode substrates used for PSI immobilization are gold (Ciesielski et al 2008(Ciesielski et al , 2010aMukherjee et al 2010;Stieger et al 2016a), graphene (Gunther et al 2013;Feifel et al 2015), titanium dioxide (Mershin et al 2012;Gordiichuk et al 2014;Shah et al 2015;Yu et al 2015;Gizzie et al 2015), or a conducting glass, FTO or ITO (Indium-doped Tin Oxide) (Ocakoglu et al 2014;Stieger et al 2016b;Szewczyk et al 2017Szewczyk et al , 2018. The substrate may have a flat surface or a porous structure to increase the number of attached proteins and thus to maximize the photocurrent.…”

Uphill energy transfer in photosystem I from Chlamydomonas reinhardtii. Time-resolved fluorescence measurements at 77 K

“…It is worth noting that the acceleration of the primary electron transfer reactions as the temperature is decreased was previously observed in bacterial reaction centers (Fleming et al 1988;Kirmaier and Holten 1990;Jia et al 1993). Interestingly, significant acceleration of excitation trapping by RCs was also observed after immobilization of cyanobacterial PSI on conducting glass at RT (Szewczyk et al 2017a, b) and this effect was explained by the dense packing of proteins in the solid-state phase (Szewczyk et al 2017a).…”