Structures of Native-like Nucleosomes: One Step Closer toward Understanding the Structure and Function of Chromatin

Genomic DNA in eukaryotes is organized into chromatin through association with core histone proteins to form nucleosomes. To understand the structure and function of chromatin, we must determine the structures of nucleosomes containing native DNA sequences. However, to date, our knowledge of nucleosome structures is mainly based on the crystallographic studies of the nucleosomes containing non-native DNA sequences. Here, we discuss the technical issues related to the determination of the nucleosome structures and review the few structural studies on native-like nucleosomes. We show how an antibody fragment-aided single-particle cryo-EM can be a useful method to determine the structures of nucleosomes containing genomic DNA. Finally, we provide a perspective for future structural studies of some native-like nucleosomes that play critical roles in chromatin functions.     

Recent Advanced Materials for Electrochemical and Photoelectrochemical Synthesis of Ammonia from Dinitrogen: One Step Closer to a Sustainable Energy Future

Ammonia (NH₃), an important raw material for chemical industry and agriculture, is also considered to be an intriguing energy storage and transportation media for chemical conversion schemes. The world's primary NH₃ supply is based on the natural nitrogen fixation by diazotrophs through an enzymatic nitrogenase process and the industrial nitrogen fixation through a traditional Haber–Bosch process. The natural synthesis of NH₃ can hardly meet the rapidly growing global demand. Meanwhile, the industrial NH₃ production is still dominated by the high‐temperature and high‐pressure reaction between nitrogen and hydrogen (N₂ + 3H₂ → 2NH₃), requiring intensive energy input and generating massive CO₂. Therefore, seeking a breakthrough in the development of catalysts toward efficient ammonia synthesis has become the frontier of energy and chemical conversion schemes. This review summarizes and discusses the recent progress on developing new strategies to optimize the efficiency of NH₃ production coupled with renewable energy sources, with a specific focus on electrocatalytic and photoelectrocatalytic conversion of N₂ to NH₃. The most recent advances in the development of catalytic materials, the design of the reaction systems, and the computational insights for electrochemical and photoelectrochemical ammonia synthesis are covered.     

One Step Membrane Incorporation of Viral Antigens as a Vaccine Candidate Against HIV

Liposomes can been used as potential immunoadjuvants, because they have the ability to elicit both a cellular mediated immune response and a humoral immune response. Studies have shown liposomes to be effective immunopotentiators in hepatitis A and influenza vaccines. For all these purposes, liposomes can be prepared by different methods. After disperging suitable membrane lipids in an aqueous phase and spontaneous formation of multilamellar large vesicles (MLV), mechanical procedures such as ultrasonication, homogenization by a French press or by other high pressure devices and, or extrusion through polycarbonate membranes with defined pore sizes lead to a reduction in size and number of lamellae of the vesicles. A second group of preparation procedures uses suitable detergents, e.g., bile salts or alkylglycosides. A third group of procedures starts with dissolving the lipids in an organic solvent and mixing it with an aqueous phase. The concentration of the organic solvent is then reduced by suitable procedures.

Here we present a new technique for the preparation of liposomes with associated membrane proteins, where lipid vesicles are formed immediately after injection into a micellar protein solution. The model membrane protein used for these studies is a truncated recombinant gp41 produced in E. coli. This viral membrane antigen is a possible candidate protein for the establishment of HIV-vaccines.

The data presented here, show an efficient and reproducible one step membrane protein encapsulation procedure into liposomes in a closed and sterile containment. We examined encapsulation efficiency, membrane protein conformation and immunogenicity of this possible liposomal vaccine candidate, which can be produced in GMP-compliant quality with the described technique.