Ultrafast Excitation Energy Transfer Dynamics in Chromoproteins: Towards Biosensing
Creators: name: Sanchez-Pedreno Jimenez, Alejandro
Publisher: name: University of Surrey
Year: 2025
Subjects: Quantum biology
Fluorescent proteins
Fluorescence Anisotropy
Biosensors
Fluorescence

description: Förster Resonance Energy Transfer (FRET) is a distance-dependent interaction between the electronic excited states of two light-interacting molecules, a donor and an acceptor, which is widely used as a ”molecular ruler” to measure dynamic changes in proximity within nanoscale distances in biological systems. Understanding how this photophysical phenomenon occurs in chromoproteins would enable the development of novel biosensors. Biological systems were thought to strictly follow the principles of classical physics. This hypothesis was supported by the notion that quantum phenomena are too fragile to withstand the hot and wet environment in biological systems. This study leverages advances in quantum mechanics to enhance biosensing technologies, focusing on the critical role of energy transfer within chromoproteins, including green fluorescent proteins (GFP) and their derivatives. A growing body of literature has reported that quantum effects at room temperature can prevail in Fluorescent Proteins (FP)s specially excitonic coupling when dimerised. Despite their widespread use, the detailed dynamics of energy transfer within these proteins, particularly how dimerisation affects these processes, could elucidate the role of FP dimerisation and provide a new route for novel biosensors. We explore the effects after exciton coupling by employing time-resolved fluorescence spectroscopy and anisotropy to elucidate the energy transfer dynamics in FP tandem dimers (TDs) and in light harvesting complexes which are also believed to exhibit exciton coupling. Experimental measurements were carried out to investigate the transition dipole of FP chromophore, the Homo-FRET depolarisation rates in a variety of FP-TD, as well as the relative dipole orientation between the chromophores, homo-FRET decays ranged from 1 to 3.20 ns and the relative dipole orientation proved to be in a parallel orientation which enables a highly efficient energy transfer. This research employs ultrafast energy transfer dynamics after exciton coupling in dEGFP-TD to develop a novel sensor for hydrophobicity and study the role of dimerisation in protecting energy transfer rates. The ultra-fast signature of dimeric enhanced green fluorescent protein (dEGFP-TD) was modulated by the hydrophobic effect of glycerol and comparison dimerisation dynamics between monomeric and dimeric eGFP showed less degree of depolarization in dimers suggesting a preferential route for energy transfer. Finally, this research presents how anisotropy measurement can be used to study wavelength-dependent energy transfer pathways in the Light Harvesting Complex II and thylakoid of higher organisms, this research shows that due to the lack of symmetry and the rate energy transfer rates between the pigments, lifetime and anisotropy measurements with 80 ps resolution are not sufficient for a comprehensive understanding in higher organisms.