Electronic energy transfer in biomacromolecules

Abstract

Electronic energy transfer is widely used as a molecular ruler to interrogate the structure of biomacromolecules, and performs a key task in photosynthesis by transferring collected energy through specialized pigment–protein complexes. Förster theory, introduced over 70 years ago, allows linking transfer rates to simple structural and spectroscopic properties of the energy‐transferring molecules. In biosystems, however, significant deviations from Förster behavior often arise due to breakdown of the ideal dipole approximation, dielectric screening effects due to the biological environment, or departure from the weak‐coupling regime. In this review, we provide a concise overview of advances in simulations of energy transfer in biomacromolecules that allow overcoming the main limitations of Förster theory. We first discuss advances in quantum chemical methods to compute electronic couplings, their extension to multiscale formulations to include screening effects, and strategies to treat the interplay between coupling fluctuations and energy transfer dynamics. We then examine the spectral overlap term, and how this quantity can be estimated from simulations of the spectral density of exciton–phonon coupling. Finally, we discuss rate theories that can describe energy transfers in situations where strong coupling leads to delocalized excitions, a common situation found in closely packed multichromophoric systems such as photosynthetic complexes and nucleic acids. This article is categorized under: Structure and Mechanism > Computational Biochemistry and Biophysics Theoretical and Physical Chemistry > Spectroscopy

Spectral Variability in Phycocyanin Cryptophyte Antenna Complexes is Controlled by Changes in the α‐Polypeptide Chains

“…Here, instead, we include this effect based on the MD‐QM/MMPol and QM/MMPol/ddCOSMO methods, thus explicitly taking into account the heterogeneous nature of the protein environment. The latter can significantly modulate screening effects compared to Förster homogeneous assumption . Moreover, in some situations the term can even lead to an enhancement of the coupling depending on the relative arrangement between chromophores .…”

“…The , which in the present formulation includes contributions mediated by both the MMPol and the ddCOSMO environment, typically leads to an overall attenuation of the coupling, and an effective screening factor can be defined as [Eq. ]: …”

Quantum Chemical Modeling of the Photoinduced Activity of Multichromophoric Biosystems

“…50,51 Approximated forms of this interaction, including the point-dipole approximation (PDA) and a point-charge expansion, have found widespread use. 52 The PDA coupling is the first nonzero multipole order of the interaction (eq 8), and can be expressed aswhere μ i / j is the transition dipole for transition i or j , R ij is the vector distance between the centers of transitions i and j , with magnitude R ij . It is well-known that the point-dipole approximation breaks down at close interchromophoric separation, namely, when R ij is smaller than the dimensions of the chromophores.…”

“…Nonetheless, because of the simplicity of its implementation, the PDA has been widely employed to compute Coulomb couplings, even outside of its range of applicability. 52…”

Linear and Kinked Oligo(phenyleneethynylene)s as Ideal Molecular Calibrants for Förster Resonance Energy Transfer

“…Thus, systematic studies with conformationally unambiguous molecules would bring significant value, not only from a fundamental perspective, but also for comparing structural information obtained from FRET with other experiments, [39][40][41] and for the validation of modern computational methods. [42][43][44][45] Table S1, and fit residuals are shown in Figure S5.…”