Relaxation Dynamics of Chlorophyll b in the Sub-ps Ultrafast Timescale Measured by 2D Electronic Spectroscopy.

Elisa Fresch,Elisabetta Collini

doi:10.3390/ijms21082836

Elisa Fresch, Elisabetta Collini

Open Access

https://doi.org/10.3390/ijms21082836

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Abstract

A thorough characterization of the early time sub-100 fs relaxation dynamics of biologically relevant chromophores is of crucial importance for a complete understanding of the mechanisms regulating the ultrafast dynamics of the relaxation processes in more complex multichromophoric light-harvesting systems. While chlorophyll a has already been the object of several investigations, little has been reported on chlorophyll b, despite its pivotal role in many functionalities of photosynthetic proteins. Here the relaxation dynamics of chlorophyll b in the ultrafast regime have been characterized using 2D electronic spectroscopy. The comparison of experimental measurements performed at room temperature and 77 K allows the mechanisms and the dynamics of the sub-100 fs relaxation dynamics to be characterized, including spectral diffusion and fast internal conversion assisted by a specific set of vibrational modes.

Highlights

Natural light-harvesting systems are comprised of numerous pigment-protein complexes, consisting of different chromophores embedded in a protein matrix [1,2]
In this work we focused the attention on the sub-100 fs relaxation dynamics of chlb within the Q-bands, employing 2D electronic spectroscopy (2DES) with 10 fs time resolution
There has been a previous work focused on the investigation of spectral diffusion chlb, there has ofbeen a experiments previous work focused the investigation of spectral the time resolution those wasspecifically not fast enough to on clearly characterize the sub-100 diffusion in chlb, the time resolution of those experiments was not fast enough to clearly characterize fs dynamics [18]

Summary

Introduction

Natural light-harvesting systems are comprised of numerous pigment-protein complexes, consisting of different chromophores embedded in a protein matrix [1,2] In these complexes, the light energy initially captured by pigments is delivered to the reaction centres through highly optimized energy transfer pathways. The light energy initially captured by pigments is delivered to the reaction centres through highly optimized energy transfer pathways The efficiency of this machinery is heavily related to the organisation of the pigments within the protein matrix and to multiple interactions of the chromophores between each other and with the protein backbone [3,4].

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Discussion

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