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The T1 (the lowest triplet)-state of the RC (reaction center)-bound 15-cis-spheroidene is examined using time-resolved EPR spectroscopy at low temperatures to identify its conformational changes. The results support the mechanism of triplet-energy dissipation, which shows that the rotational motions around the central double bonds cause a change in the orbital angular momentum and through the spin-orbit coupling, a change in the spin angular momentum, which enhances T1--> S0 intersystem crossing dissipating the triplet energy.

Sub-mu-second time-resolved difference absorption spectra of a polar carotenoid analogue, 2-(all-trans-retinylidene)indan-1,3-dione (RetInd), were recorded in tetrahydrofuran at room temperature upon anthracene-sensitized triplet excitation. The 'cation' of RetInd showed vibrational structure in its absorption spectrum, and its lifetime was determined to be 15(mu)s.

Development of efficient photocatalysts with a wide spectral range for the photocatalytic hydrogen evolution reaction (HER) is a promising way to address the current energy and environmental crises. In particular, utilization of natural photosynthetic pigments in the artificial HER is a rational approach to explore better photocatalysts toward practical applications. In this work, bacteriochlorophyll-a (BChl-a) derivatives combined with a series of carotenoids were synthesized and deposited on the surface of Ti3C2Tx MXenes to prepare organic–inorganic composites as noble metal-free photocatalysts for the HER. The optical properties of six kinds of dye-sensitizers, namely, methyl bacteriopyropheophorbide-a (Dye-1), four bacteriochlorin–carotenoid dyads (Dyes-2–5), and a triad (Dye-6) were investigated both in solutions and in solid thin films, and the composites (Dye@Ti3C2Tx) were used as photocatalysts for the HER under white light irradiation (λ > 420 nm) in an aqueous suspension system in the presence of ascorbic acid at pH = 2.8. Among the Dyes-1–6 possessing different side chains at the C17-propionate terminal of bacteriochlorin chromophores, the Ti3C2Tx hybrid photocatalyst composed of Dye-4 with a siphonaxanthin analog unit showed the highest hydrogen evolution efficiency, and its best value was 5 times larger compared to that of Dye-1@MXene without a conjugated carotenoid chromophore. Other Dye@Ti3C2Tx composites showed enhanced H2 evolution abilities over Dye-1@MXene, depending on the structural characteristics of dye-sensitizers composed of bacteriochlorin and different kinds of carotenoids. The observed high activity of Dye-4@MXene for the HER is attributed to the panchromatic light absorption ability of Dye-4 through the visible to near-infrared range as well as the desirable charge separation at the Dye-4@Ti3C2Tx interface. This study provides new insights into utilizing photosynthetic dyes to construct MXene hybrid structures suitable for photocatalytic water-splitting H2 production. [ABSTRACT FROM AUTHOR]

The relation between volume and enthalpy changes in the melting regime of lipid membranes is studied by employing differential scanning calorimetry, pressure calorimetry, and densitometry. The study concluded that pressure calorimetry could serve as a valuable tool to measure the proportional relation between volume and enthalpy changes accurately.

Experiments on chaotically oscillating arrays of nickel electrodes in sulfuric acids are conducted. It concluded that the application of periodic forcing affects the dynamics of the individual oscillators and thus changes the collective dynamics, making condensation possible.

The chemical shifts of various compounds including cyclic and acyclic saccharides, oligoglycines, and sodium chloride using an external reference in terms of volume magnetic susceptibilities and molar volumes of these compounds is investigated. The equilibrium formation constant and structure of ion-pair of tetrathylammonium (TMA) and benzenesulfonate ion (BS) are estimated from chemical shifts referred to an internal standard.

The synthesis and characterization of a model for the active site of thiamin-dependent enzymes in solution is reported. The data showed that, in the ternary Cu(super 2+)-[pentapeptide]-[HETPP] system at physiological pH, the peptide backbone offers three coordination sites to the metal ion and the coordination sphere is completed by two additional phosphate oxygen and the nitrogen N(1') of the thiamine coenzymes.