Strategy of photo-protection in phytoplankton assemblages in the Kongsfjorden, Svalbard, Arctic

Photo-protective functions were investigated in phytoplankton assemblages at Kongsfjorden, Svalbard in spring, using their UV-absorbing compounds （mycosporine-like amino acids （MAAs））, xanthophyllpigments （diadinoxanthin （DD） and diatoxanthin （DT）） and〈beta〉-dimethylsulphoniopropionate （〈beta〉-DMSP）. The dominant phytoplankton species in the inner bay were dominated by Phaeocystis spp. and nanoflagellates, while the offshore waters were dominated by Thalassiosira spp. In the inner bay, UV- absorbing compounds and xanthophyll pigments exhibited higher ratios of MAA to chlorophyll a （MAA：chl a ratio）, and both DD and DT to chlorophyll a （DD：chl a ratio and DT：chl a ratio）, respectively. Thus, the photoprotective-pigrnents such as DD and DT appear to complement MAAs in the natural phytoplankton assemblage. However, the ratio of 〈beta〉-DMSP to chlorophyll a （〈beta〉-DMSP：chl a ratio） did not show a distinct spatial distribution according to environmental factors or interspecies differences. In this study, we found that photoprotective compounds occurred in a manner dependent on the phytoplankton species composition in Kongsfjorden Bay, where Phaeocystis is the dominant species.

Research Progress of Sunscreen Agents and Encapsulate Technology

The harm of ultraviolet radiation to human skin and the mechanism of traditional sunscreen agents and natural sunscreen agents were reviewed.Sunscreen agents were usually encapsulated with delivery systems due to the instability and skin permeability.The research progress of several common sunscreen delivery systems was introduced,the future research direction of sunscreen agents was also prospected.

Effects of pH on the peripheral light-harvesting antenna complex for Rhodopseudomonas palustris

In this work steady-state absorption spectroscopy, circular dichroism spectroscopy and sub-micro-second time-resolved absorption spectroscopy were used to investigate the effect of pH on the struc-tures and functions of LH2 complex for Rhodopseudomonas palustris. The results revealed that: (1) B800 Bchla was gradually transformed to free pigments absorbing around 760 nm on the minutes timescale upon the induction of strong acidic pH, and subsequently there disappeared the CD signal for Qy band of B800 in the absence of B800. In addition, Carotenoids changed with the similar tendency to B850 BChl. (2) The introduction of strong basic pH gave rise to no significant changes for B800 Bchla, while B850 BChla experienced remarkable spectral blue-shift from 852 to 837 nm. Similar phe-nomenon was seen for the CD signal for Qy band of B850. Carotenoids displayed strong and pH-independent CD signals in the visible range. (3) In the case of both physiological and basic pH, broad and asymmetrical positive Tn←T1 transient absorption appeared following the pulsed photo-excitation of Car at 532 nm. By contrast, the featureless and weak positive signal was observed on the sub-microsecond timescale in the acidic pH environment. The aforementioned experimental results indicated that acidic pH-induced removal of B800 Bchla prevented the generation of the caro-tenoid triplet state (3Car*), which is known to be essential for the photo-protection function. Neverthe-less, carotenoids can still perform this important physiological role under the basic pH condition, where the spectral blue shift of B850 exerts little effect on the overall structure of the cyclic aggregate, therefore favoring the formation of carotenoid triplet state.

Peptide photocaging:A brief account of the chemistry and biological applications

Light is arguably the most convement non-invasive stimulant to perturb or control specinc cnemical reactions in the biological systems. Upon light illumination, photosensitive molecules incur conformational changes or formation/breaking of chemical bonds. Consequently, these molecules can be used to transfer signals from one location to another in the cell, from outside of the cell to the inside, or from a light bulb to the interior of animal tissues. The development of the photochemical reactions of organic compounds has paved the road towards their use in peptides and peptide-based biological applications. In this mini-review, we summarized the state-of-the-art development of photo-protecting groups for peptide photocaging including the un-caging mechanism of different PPGs, the synthesis of photo-caged peptides, and the recent applications of peptide photocaging in chemical biology.