Carotenoid-induced non-photochemical quenching in the cyanobacterial chlorophyll synthase-HliC/D complex.

Chl synthase (ChlG) is an important enzyme of the Chl biosynthetic pathway catalyzing attachment of phytol/geranylgeraniol tail to the chlorophyllide molecule. Here we have investigated the Flag-tagged ChlG (f.ChlG) in a complex with two different high-light inducible proteins (Hlips) HliD and HliC.

Ultrafast Dynamics of Long Homologues of Carotenoid Zeaxanthin.

Three zeaxanthin homologues with conjugation lengths N of 15, 19, and 23 denoted as Z15, Z19, and Z23 were studied by femtosecond transient absorption spectroscopy, and the results were compared to those obtained for zeaxanthin (Z11). The energies of S2 decrease from 20 450 cm(-1) (Z11) to 18 280 cm(-1) (Z15), 17 095 cm(-1) (Z19), and 16 560 cm(-1) (Z23). Fitting the N dependence of the S2 energies allowed the estimation of [Formula: see text], the S2 energy of a hypothetical infinite zeaxanthin, to be ∼14 000 cm(-1).

Mechanism of photoprotection in the cyanobacterial ancestor of plant antenna proteins.

Plants collect light for photosynthesis using light-harvesting complexes (LHCs)-an array of chlorophyll proteins that are able to reversibly switch from harvesting to energy-dissipation mode to prevent damage of the photosynthetic apparatus. LHC antennae as well as other members of the LHC superfamily evolved from cyanobacterial ancestors called high light-inducible proteins (Hlips). Here, we characterized a purified Hlip family member HliD isolated from the cyanobacterium Synechocystis sp.

Highly efficient energy transfer from a carbonyl carotenoid to chlorophyll a in the main light harvesting complex of Chromera velia.

We report on energy transfer pathways in the main light-harvesting complex of photosynthetic relative of apicomplexan parasites, Chromera velia. This complex, denoted CLH, belongs to the family of FCP proteins and contains chlorophyll (Chl) a, violaxanthin, and the so far unidentified carbonyl carotenoid related to isofucoxanthin. The overall carotenoid-to-Chl-a energy transfer exhibits efficiency over 90% which is the largest among the FCP-like proteins studied so far.

Coupling to light, and transport and dissipation of energy in silver nanowires.

Transient absorption experiments with diffraction-limited spatial resolution have been used to study the optical absorption properties and dynamics of isolated, single silver nanowires. The images and polarization analysis show that the near-IR pump and near-UV probe beams couple to fundamentally different electron motions. The near-IR pump laser excites the propagating surface plasmon polariton (SPP) modes of the wires when focused at the ends, and multipolar plasmon modes (antenna modes) for medial excitation.

Dark-field microscopy studies of single metal nanoparticles: understanding the factors that influence the linewidth of the localized surface plasmon resonance.

This article provides a review of our recent Rayleigh scattering measurements on single metal nanoparticles. Two different systems will be discussed in detail: gold nanorods with lengths between 30 and 80 nm, and widths between 8 and 30 nm; and hollow gold-silver nanocubes (termed nanoboxes or nanocages depending on their exact morphology) with edge lengths between 100 and 160 nm, and wall thicknesses of the order of 10 nm. The goal of this work is to understand how the linewidth of the localized surface plasmon resonance depends on the size, shape, and environment of the nanoparticles.