Photosynthetic Pigment-protein Research Articles

A comprehensive assessment of photosynthetic acclimation to shade in C4 grass (Cynodon dactylon (L.) Pers.)

BackgroundLight deficit in shaded environment critically impacts the growth and development of turf plants. Despite this fact, past research has predominantly concentrated on shade avoidance rather than shade tolerance. To address this, our study examined the photosynthetic adjustments of Bermudagrass when exposed to varying intensities of shade to gain an integrative understanding of the shade response of C4 turfgrass.ResultsWe observed alterations in photosynthetic pigment-proteins, electron transport and its associated carbon and nitrogen assimilation, along with ROS-scavenging enzyme activity in shaded conditions. Mild shade enriched Chl b and LHC transcripts, while severe shade promoted Chl a, carotenoids and photosynthetic electron transfer beyond QA− (ET0/RC, φE0, Ψ0). The study also highlighted differential effects of shade on leaf and root components. For example, Soluble sugar content varied between leaves and roots as shade diminished SPS, SUT1 but upregulated BAM. Furthermore, we observed that shading decreased the transcriptional level of genes involving in nitrogen assimilation (e.g. NR) and SOD, POD, CAT enzyme activities in leaves, even though it increased in roots.ConclusionsAs shade intensity increased, considerable changes were noted in light energy conversion and photosynthetic metabolism processes along the electron transport chain axis. Our study thus provides valuable theoretical groundwork for understanding how C4 grass acclimates to shade tolerance.

Identification and functional analysis of phycocyanin-derived bioactive peptides with non-small cell lung cancer cell inhibition

Non-small cell lung cancer (NSCLC) is one of the most lethal types of malignancies around the world. Phycocyanin, a type of functional food additive derived from photosynthetic pigment protein in Spirulina cells, has been verified to exhibit antineoplastic effect on NSCLC. However, the investigation on bioactive peptides of phycocyanin, especially in NSCLC, remains poorly documented. The goal of this work is to identify novel phycocyanin-derived bioactive peptides with NSCLC cell inhibition function. Phycocyanin was hydrolysed by trypsin, followed by peptides isolation, purification and identification through ultrafiltration, high performance liquid chromatography (HPLC) and mass spectrometry (MS), respectively. Three phycocyanin peptides (PCP1: AGDASVLEDR, PCP2: ADSLLSGLR and PCP3: MFDAFTK) predicted to exhibiting anticancer ability were identified. Molecular docking analysis indicated the peptides had strong interaction with epidermal growth factor receptor (EGFR), a proto-oncogene in cells. Phenotype experiments showed that peptides significantly inhibited growth and migration of A549, H1299 and LTEP-a2 cells. Moreover, they also suppressed the activity of Akt pathway of NSCLC cells. Three phycocyanin-derived peptides might be suitable for development as new anti-lung cancer agents, owing to their antineoplastic activities. The current work also provides a vital basis for further utilization of marine algae nutrient components.

Effects of intramolecular vibrations on excitation energy transfer dynamics of the Fenna-Matthews-Olson complex

The role of vibrational coherence in photosynthetic pigment-proteins has been controversial. The present article investigates theoretically how the intramolecular vibrations of bacteriochlorophyll (BChl) influence the excitation energy transfer (EET) dynamics in the Fenna-Matthews-Olson complex (FMO). To this end, we use an exciton model incorporating recent experimental data and treat the vibrations as both coherent and incoherent. We simulate the transfer phenomena numerically with non-Markovian quantum dynamics. Our results at 300 K indicate that incoherent vibrations can moderately improve the efficiency of EET between FMO and a reaction center. With a vibronic model, we show that the coherent vibrations in either strongly or resonantly coupled BChl pairs can generate characteristic oscillations in their electronic populations which persist for several picoseconds even at 300 K. Despite such robust coherences, no significant improvement in the efficiency of EET is observed.

Enhancement of Photocurrent by Integration of an Artificial Light-Harvesting Antenna with a Photosystem I Photovoltaic Device

Photosynthetic pigment–protein-based biophotovoltaic devices are attracting interest as environmentally friendly energy sources. Photosystem I (PSI), a photosynthetic pigment–protein, is a proven biophotovoltaic material because of its abundance and high charge separation quantum efficiency. However, the photocurrent of these biophotovoltaic devices is not high because of their low spectral response. We have integrated an artificial light-harvesting antenna into a PSI-based biophotovoltaic device to expand the spectral response. To fabricate the device, a perylene di-imide derivative (PTCDI) was introduced onto a TiO2 surface as an artificial antenna. In the photovoltaic cells formed by the PTCDI/PSI-assembled TiO2 electrode, the magnitude of the incident photon-to-current conversion efficiency spectrum was significantly enhanced in the range 450–750 nm, and the photocurrent increased to 0.47 mA/cm2. The result indicates that the photons absorbed by PTCDI transfer to PSI via Forster resonance energy transfer.

Excitation transfer pathways in excitonic aggregates revealed by the stochastic Schrödinger equation

We derive the stochastic Schrödinger equation for the system wave vector and use it to describe the excitation energy transfer dynamics in molecular aggregates. We suggest a quantum-measurement based method of estimating the excitation transfer time. Adequacy of the proposed approach is demonstrated by performing calculations on a model system. The theory is then applied to study the excitation transfer dynamics in a photosynthetic pigment-protein Fenna-Matthews-Olson (FMO) aggregate using both the Debye spectral density and the spectral density obtained from earlier molecular dynamics simulations containing strong vibrational high-frequency modes. The obtained results show that the excitation transfer times in the FMO system are affected by the presence of the vibrational modes; however, the transfer pathways remain the same.

Conformational changes in photosynthetic pigment proteins on thylakoid membranes can lead to fast non-photochemical quenching in cyanobacteria

A high non-photochemical quenching (NPQ) appeared below the phase transition temperature when Microcystis aeruginosa PCC7806 cells were exposed to saturated light for a short time. This suggested that a component of NPQ, independent from state transition or photo-inhibition, had been generated in the PSII complex; this was a fast component responding to high intensity light. Glutaraldehyde (GA), commonly used to stabilize membrane protein conformations, resulted in more energy transfer to PSII reaction centers, affecting the energy absorption and dissipation process rather than the transfer process of phycobilisome (PBS). In comparison experiments with and without GA, the rapid light curves (RLCs) and fluorescence induction dynamics of the fast phase showed that excess excitation energy was dissipated by conformational change in the photosynthetic pigment proteins on the thylakoid membrane (PPPTM). Based on deconvolution of NPQ relaxation kinetics, we concluded that the fast quenching component (NPQf) was closely related to PPPTM conformational change, as it accounted for as much as 39.42% of the total NPQ. We hypothesize therefore, that NPQf induced by PPPTM conformation is an important adaptation mechanism for Microcystis blooms under high-intensity light during summer and autumn.

Photosynthetic pigments and pigment-proteins in natural populations of Antarctic sea-ice diatoms

Abstract Pigment analyses of natural populations of sea-ice diatoms in Antarctica showed a range of chlorophyll a : c molar ratios of 1.85–3.83 and carotenoid (fucoxanthin): chlorophyll a molar ratios of 1.52–2.57. To understand the structural organization of pigments in these low light-adapted populations, the photosynthetic apparatus of a monospecific natural population of the Antarctic sea ice diatom, Nitzschia stellata Manguin (Bacillariophyta), was investigated. Three chlorophyll-protein complexes were isolated from the thylakoid membranes of this diatom. Spectral and pigment analyses revealed that, while all three complexes possessed chlorophyll a and fucoxanthin, chlorophyll c was found only in Complexes I and II. Fifty-nine per cent of the chlorophyll c was found in Complex I, which possessed a chlorophyll a: chlorophyll c: fucoxanthin ratio of 1 : 2: 1, a ratio enriched in accessory pigments compared to whole cell ratios. Complex III contained fucoxanthin and 53% of the total chlorophyll a; this ...