Zhengyan Wu

The protective antigen component of anthrax toxin forms a homoheptameric pore in the endosomal membrane, creating a narrow passageway for the enzymatic components of the toxin to enter the cytosol. We found that, during conversion of the heptameric precursor to the pore, the seven phenylalanine-427 residues converged within the lumen, generating a radially symmetric heptad of solvent-exposed aromatic rings. This "phi-clamp" structure was required for protein translocation and comprised the major conductance-blocking site for hydrophobic drugs and model cations. We conclude that the phi clamp serves a chaperone-like function, interacting with hydrophobic sequences presented by the protein substrate as it unfolds during translocation.

In this work, a pH-responsively controlled-release chlorpyrifos (PRCRC) was developed using a nanosystem consisting of chlorpyrifos (CPF), polydopamine (PDA), attapulgite (ATP), and calcium alginate (CA). Therein, CPF was adsorbed in the nanonetwork-structured PDA-modified ATP (PA) to obtain CPF-PA through hydrogen bonds and electrostatic attraction. Subsequently, CPF-PA combined with CA to form porous CPF-PA-CA hydrogel spheres (actually PRCRC) through cross-linking reaction, wherein PA acted as the skeleton. PRCRC spheres tended to collapse in alkaline solution and promoted the release of CPF, thus displayed a good pH-responsively controlled release performance, which was proved by the control efficacy test on grubs. Besides, the system could effectively protect CPF molecules from degradation under ultraviolet light. Importantly, the PA-CA hydrogel possessed a benign biocompatibility on Escherichia coli and foxtail millet, showing a high biosafety. Therefore, this work provides a promising approach to improve the utilization efficiency and prolong duration of pesticide, which might have a huge potential application prospect.