Structural basis for the assembly and electron transport mechanisms of the dimeric photosynthetic RC-LH1 supercomplex

The reaction center (RC) and light-harvesting complex 1 (LH1) form a RC-LH1 core supercomplex that is vital for the primary reactions of photosynthesis in purple photosynthetic bacteria. Some species possess the dimeric RC-LH1 complex with an additional polypeptide PufX, representing the largest photosynthetic complex in anoxygenic phototrophs. However, the details of the architecture and assembly mechanism of the RC-LH1 dimer are unclear. Here we report seven cryo-electron microscopy (cryo-EM) structures of RC-LH1 supercomplexes from Rhodobacter sphaeroides. Our structures reveal that two PufX polypeptides are positioned in the center of the S-shaped RC-LH1 dimer, interlocking association between the components and mediating RC-LH1 dimerization. Moreover, we identify a new transmembrane peptide, designated PufY, which is located between the RC and LH1 subunits near the LH1 opening. PufY binds a quinone molecule and prevents LH1 subunits from completely encircling the RC, creating a channel for quinone/quinol exchange. Genetic mutagenesis, cryo-EM structures, and computational simulations enable a mechanistic understanding of the assembly and electron transport pathways of the RC-LH1 dimer and elucidate the roles of individual components in ensuring the structural and functional integrity of the photosynthetic supercomplex.

The Succession of Flies of Forensic Importance Is Influenced by Volatiles Organic Compounds Emitted During the First Hours of Decomposition of Chicken Remains

After death, a series of primary reactions occur that produce volatile organic compounds (VOCs) that are released into the environment. In this study, we investigated if the succession of flies of forensic importance in the first hours after death is mediated by VOCs in order to better understanding of the ecology of necrophagous insects. In total, 685 adult insects (Diptera and Hymenoptera) were collected by traps baited with chicken remains at different decomposition times (0, 6, 12, 24, 36, or 48 h). Of the total of insects caught, individuals from six families of Diptera can be cataloged of forensic importance. The most abundant dipteran family was Piophilidae with 213 individuals, followed by Calliphoridae with 178 specimens. Of the total flies caught, 90% were females and the rest were males. Most of the caught females were categorized as gravid, which visited more often the decaying tissues compared to nongravid females. The abundance of the flies increased in the remains with a longer time of decomposition. Six VOCs emitted in different relative quantities were identified according to the decomposition time of the remains. An apparent association was observed between the emission of ρ-cresol with Lucilia eximia (Wiedemann), between the emission of phenol, dimethyl disulfide, and dimethyl trisulfide with Chrysomya rufifacies (Macquart), and between the emissions of indole with Cochliomyia macellaria (Fabricius).

Phosphotungstic acid as a novel acidic catalyst for carbohydrate protection and glycosylation

This work demonstrates the utilization of PTA as an acidic catalyst in primary reactions of carbohydrate. PTA can be widely used as a catalyst for carbohydrate chemistry. The reactions are executed at 0 °C or room temperature in good yields.

The Sonochemical Synthesis of Simple Organic Biomolecules in Aqueous Solutions Containing Dissolved Prebiotic Gases

This review considers the generation of relatively simple biomolecules, e.g., primary amino acids, resulting from the rapid collapse of bubbles in aqueous solutions containing various, low molar mass, gases. Some of the possible primary reactions occurring to produce the biomolecules are introduced and discussed. A brief discussion is included on the possible involvement of hydrodynamic cavitation, at the primordial seashore, as the initiating processes for the formation of the first organic molecules on prebiotic earth and the origins of life on Earth some 4 billion years ago.