How the Protein Environment Can Tune the Energy, the Coupling, and the Ultrafast Dynamics of Interacting Chlorophylls: The Example of the Water-Soluble Chlorophyll Protein

Abstract

The interplay between active molecules and the protein environment in light-harvesting complexes tunes the photophysics and the dynamical properties of pigment–protein complexes in a subtle way, which is not fully understood. Here we characterized the photophysics and the ultrafast dynamics of four variants of the water-soluble chlorophyll protein (WSCP) as an ideal model system to study the behavior of strongly interacting chlorophylls. We found that when coordinated by the WSCP protein, the presence of the formyl group in chlorophyll b replacing the methyl group in chlorophyll a strongly affects the exciton energy and the dynamics of the system, opening up the possibility of tuning the photophysics and the transport properties of multichromophores by engineering specific interactions with the surroundings.

Engineering couplings for exciton transport using synthetic DNA scaffolds

“…Nanoscale control over chromophore position is challenging in proteins due to their structural complexity and limitations in mutagenesis. [20][21][22] Instead, synthetic model systems that position chromophores have been developed, including metal-organic frameworks, 8,23 viral proteins, [24][25][26] self-assembled molecular aggregates, [27][28][29][30] and conjugated polymers. 31 However, these systems lack a synthetic handle for electronic coupling.…”

Electron Nuclear Double Resonance of the Chlorophyll Triplet State in the Water-Soluble Chlorophyll Protein from Brassica oleracea: Investigation of the Effect of the Binding Site on the Hyperfine Couplings

“…The four symmetry-related chlorophyll (Chl) binding sites are identical, and therefore, the four bound chromophores experience identical protein surroundings and are spectroscopically equivalent, contrarily to chlorophyll (Chl)-binding complexes involved in photosynthesis, in which tens to hundreds of chromophores are bound in finely tuned individual binding sites [12], resulting in highly complex spectra. It follows that WSCP is an ideal model system for detailed spectroscopic investigation focused on understanding Chl-protein and Chl-Chl interactions [5,[13][14][15][16][17][18][19][20].…”

“…(E) Plot of the displacement of each tetrapyrrole atom from the plane defined averaging the position of the 24 atoms composing the tetrapyrrolic system for the Chls a in Bo WSCP [4] and Lv WSCP [3] (in black and gray, respectively). The x-axis is not in scale 1 3 Electron Nuclear Double Resonance of the Chlorophyll Triplet… selectivity [10,19] and to the observed differences in the optical properties of the bound Chls [4,18,19,23]. In particular, the absorption of the Q y (S 0 → S 1 ) band of Chl a in class IIa WSCP from Brassica oleracea var.…”

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

“…It is now ascertained that chlb expands the spectral range of chla for capturing sunlight and tunnelling it to the reaction centres [11][12][13] and that it also plays an essential role in the turnover of light-harvesting complexes [14]. More recently, it has been discovered that the electronic properties of chlb are tuned by specific interactions between the protein backbone and the formyl group in the C7 position, whose presence distinguishes the molecular structure of chlb from chla [15]. the redistribution of energy to specific vibrational modes.…”