Metal nanoclusters (NCs) with unique chemical and physical properties have been extensively demonstrated to be emerging nanoantibiotics for fighting bacterial infections. Understanding the antibacterial mechanisms of metal nanoclusters is important for evaluating their clinical applications as nanoantibiotics. To understand the antibacterial mechanism, gold nanoclusters (AuNCs) were applied as an antibacterial agent for real-time observations of their interactions with bacteria by in situ transmission electron microscopy (TEM). In this work, a surface ligand of glutathione-conjugated (GSH)-AuNCs was prepared via a simple hydrothermal method. Optical and structural characterizations validated the successful preparation of GSH-AuNCs. Bacterial growth curves of Acetobacter aceti revealed that the antibacterial activity of GSH-AuNCs increased with the weight concentration. The antibacterial activity of GSH-AuNCs was confirmed by the intracellular reactive oxygen species (ROS) generation induced by GSH-AuNCs in A. aceti. Furthermore, real-time observations of interactions between GSH-AuNCs and A. aceti were made using in situ liquid cell TEM. Based on the results of real-time observations, GSH-AuNCs first attached onto the bacterial membranes of A. aceti by physical adsorption and then penetrated into A. aceti by internalization. Eventually, the production of intracellular ROS induced by GSH-AuNCs caused destruction of the bacterial membranes, which led to the death of A. aceti. After the bacterial membranes had been destroyed, A. aceti eventually died.

SynopsisWe report that aliphatic primary and secondary amines completely solubilize crosslinked silicone resins and rubber compositions at room temperature. The solubilization is attributed to nucleophilic cleavage of Si-0 bonds by amines, which apparently occurs selectively at crosslinking sites. The selectivity may reflect the presence of three oxygen atoma at such sites, which are expected to enhance the electrophilicity of silicon. On evaporation of amine, crosslinks are apparently regenerated as evidenced by solubility characteristics as well as f i l m properties of the reclaimed silicones. In addition to their theoretical interest, these results are potentially important from the standpoint of commercial applications as well, including the possible reclaiming of silicone-constituted furniture molds and the coating of heat-sensitive materials.During the course of studies on the application of solubility parameter methods for swelling cured we have found that aliphatic primary and secondary amines completely solubilize crosslinked siloxane polymers at room temperature. A major objective of this research was the development of solvent-based methods for facilitating the recovery of spores from plastic and rubbery materials utilized in spacecraft components. This goal was conveniently accomplished in high yields in the case of representative silicones by treatment with amines followed by plate counting methods (these results will be submitted elsewhere). Nevertheless, the unexpected finding of complete solubilization of cured silicones by amines prompted further studies on the nature of this interaction. The results are reported herein which indicate that amines react selectively at Si-0 crosslinking sites by nucleophilic substitution, as illustrated in eq. (1). Furthermore, the reversibility of this reaction is evidenced by the reformation of crosslinked sites on evaporation of amine. In addition to their theoretical interest, these results are potentially important from a technological standpoint as well, including the possible applications of reclaiming silicone-constituted furniture molds and coating of heat-sensitive materials.Initial studies were conducted with Dow Corning DC 840 silicone resin, which possesses a phenyl methyl polysiloxane backbone. The prepolymer also contains silanol (Si-OH) sites which are converted into Si-0-Si crosslinkages during curing. After curing at 24OOC for 1 hr, 50-mg samples (as cubes approximately 3 mm on a side) were suspended in 2 ml m i n e solvent

Global warming and climate change are among the most immediate challenges confronting humans in the 21st century. Artificial photosynthesis represents a promising approach to mitigating the environmental crisis. Recently, people demonstrated that interfacing semiconductor, polymer, or metal-based nanomaterials with specific bacteria can generate built-in artificial photosynthetic systems, enabling solar-to-fuel conversion by forming a basic photosynthetic unit from a network of light-harvesting receptors, molecular water splitting and CO2, or proton reduction machinery. As a cutting-edge research direction, several strategies have been employed to create the artificial photosynthetic biohybrids. Notably, understanding of the molecular basis of these photosynthetic biohybrid systems is the key to improving the solar-to-chemical conversion efficiency. In the current review, we highlight the study of charge uptake channels in biohybrid artificial photosynthetic systems using various nanomaterials and microbes. We emphasize the importance of fully understanding the structures and operating mechanisms of these hybrid systems, as well as the criterion to select suitable microbes and photosensitized nanomaterials.