Concentration Effect on Quenching of Chlorophyll a Fluorescence by All-Trans-β-Carotene in Photosynthesis

Energy Transfer and Radical-Pair Dynamics in Photosystem I with Different Red Chlorophyll a Pigments

We establish a general kinetic scheme for the energy transfer and radical-pair dynamics in photosystem I (PSI) of Chlamydomonas reinhardtii, Synechocystis PCC6803, Thermosynechococcus elongatus and Spirulina platensis grown under white-light conditions. With the help of simultaneous target analysis of transient-absorption data sets measured with two selective excitations, we resolved the spectral and kinetic properties of the different species present in PSI. WL-PSI can be described as a Bulk Chl a in equilibrium with a higher-energy Chl a, one or two Red Chl a and a reaction-center compartment (WL-RC). Three radical pairs (RPs) have been resolved with very similar properties in the four model organisms. The charge separation is virtually irreversible with a rate of ≈900 ns-1. The second rate, of RP1 → RP2, ranges from 70-90 ns-1 and the third rate, of RP2 → RP3, is ≈30 ns-1. Since RP1 and the Red Chl a are simultaneously present, resolving the RP1 properties is challenging. In Chlamydomonas reinhardtii, the excited WL-RC and Bulk Chl a compartments equilibrate with a lifetime of ≈0.28 ps, whereas the Red and the Bulk Chl a compartments equilibrate with a lifetime of ≈2.65 ps. We present a description of the thermodynamic properties of the model organisms at room temperature.

Energy transfer and trapping in photosystem I with and without chlorophyll-f

We establish a general kinetic scheme for energy transfer and trapping in the photosystem I (PSI) of cyanobacteria grown under white light (WL) or far-red light (FRL) conditions. With the help of simultaneous target analysis of all emission and transient absorption datasets measured in five cyanobacterial strains, we resolved the spectral and kinetic properties of the different species present in PSI. WL-PSI can be described by Bulk Chl a, two Red Chl a, and a reaction center compartment (WL-RC). The FRL-PSI contains two additional Chl f compartments. The lowest excited state of the FRL-RC is downshifted by ≈ 29 nm. The rate of charge separation drops from ≈900 ns-1 in WL-RC to ≈300 ns-1 in FRL-RC. The delayed trapping in the FRL-PSI (≈130 ps) is explained by uphill energy transfer from the Chl f compartments with Gibbs free energies of ≈kBT below that of the FRL-RC.

Spectral detection technology of vegetable oil: Spectral analysis of porphyrins and terpenoids

In this paper, the existence of porphyrins and terpenoids in different vegetable oils and their spectral characterization techniques are reported. The classification of pure vegetable oils was realised by principal component analysis - support vector machine (PCA-SVM) model. The absorption spectra, Raman spectra, fluorescence spectra and supercontinuum spectra of 8 kinds of pure vegetable oils were studied, and the effects of oil types and processing technology on spectral differences were analysed. The results showed that the fingerprint information of 4 kinds of spectral techniques mainly came from chlorophyll and β-carotene in vegetable oil. The extra virgin olive oil (EVOO) got by physical cold pressing technology had the most porphyrins and terpenoids content and the strongest activity. Therefore, the spectral characterization of porphyrins and terpenoids in vegetable oil can guide the regulation of the processing technology of vegetable oil and realise the qualitative and quantitative analysis of vegetable oil.

Photobiology and Endogenous Fluorophore Based Applications, from Natural Environment to Biomedicine to Improve Human Life

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Effects of carotenoids on the absorption and fluorescence spectral properties and fluorescence quenching of Chlorophyll a

Fluorescence and absorption characteristics of Chlorophyll a (Chl-a) were modulated by the carotenoids (Cars) with different numbers of conjugated carbon‑carbon double bonds in solutions. The Chl-a absorption appears the redshift phenomenon with the effective conjugated of Cars increasing. The absorption of Chl-a and Cars are linearly dependent on intrinsic factors, namely effective conjugate length and functional groups, and on environmental factors, such as the polarizability of the solvent. Cars can be able to quench the Chl-a fluorescence by producing the non-emitting exciplex intermediate. The effective conjugated length of Cars is one of the reasons that effect the fluorescence quenching of Chl-a. According to the Stern-Volmer plots, the Chl-a fluorescence quenching should be predominantly dynamic rather than static.