Investigations of the Energy Transfer in the Phycobilisome Antenna of Arthrospira platensis Using Femtosecond Spectroscopy

Alexandra Fălămaș,Sebastian A Porav,Valer Tosa

doi:10.3390/app10114045

Abstract

Understanding the energy transfer in phycobilisomes extracted from cyanobacteria can be used for building biomimetic hybrid systems for optimized solar energy collection and photocurrent amplification. In this paper, we applied time-resolved absorption and fluorescence spectroscopy to investigate the ultrafast dynamics in a hemidiscoidal phycobilisome obtained from Arthrospira platensis. We obtained the steady-state and time-resolved optical properties and identified the possible pathways of the excitation energy transfer in the phycobilisome and its components, phycocyanin and allophycocyanin. The transient absorption data were studied using global analysis and revealed the existence of ultrafast kinetics down to 850 fs in the phycobilisome. The fluorescence lifetimes in the nanosecond time-scale assigned to the final emitters in each sample were obtained from the time-correlated single photon counting fluorescence experiments.

Highlights

Arthrospira (Spirulina) platensis is planktonic, photoautotrophic, filamentous cyanobacteria, which is morphologically characterized by multicellular spiral trichomes [1]
Cyanobacterial phycobiliproteins are found in vivo assembled in huge macromolecular complexes, which are known as phycobilisomes (PBSs)
We found that the A. platensis PBS

Summary

Introduction

Arthrospira (Spirulina) platensis is planktonic, photoautotrophic, filamentous cyanobacteria, which is morphologically characterized by multicellular spiral trichomes [1]. The PBSs are the main light harvesting antenna systems found in cyanobacteria and red algae, which are unique complexes among all photosynthetic organisms that are located on the stromal face of the thylakoid membrane [2]. The PBS is a macromolecular complex formed by soluble, colored proteins, known as phycobiliproteins (PBPs) and linker polypeptides [3,4]. The PBS can be found in several shapes, from hemidiscoidal and hemielipsoidal to bundle shape. Regardless of their shape, the basic structure of the PBS can be divided into two structural different compartments, consisting of a cylindrical core from which several rods of stacked disks radiate out [7].

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