Mechanistic Insights into the Folding Mechanism of Region V in Ice-Binding Protein Secreted by Marinomonas primoryensis Revealed by Single-Molecule Force Spectroscopy.

The Gram-negative bacteria Marinomonas primoryensis secrete an ice-binding protein (MpIBP), which is a vital bacterial adhesin facilitating the adaptation and survival of the bacteria in the harsh Antarctic environment. The C-terminal region of MpIBP, known as region V (RV), is the first domain to be exported into the Ca2+-rich extracellular environment and acts as a folding nucleus for the entire adhesin. However, the mechanisms underlying the secretion and folding of RV remain poorly understood. Here, we used optical tweezers (OT) to investigate the secretion and folding mechanisms of RV at the single-molecule level. In the absence of Ca2+, apo-RV remains unstructured, while Ca2+-bound RV folds into a mechanically stable structure. The folding of RV could occur via the formation of an intermediate state. Even though this folding intermediate is "hidden" during the folding process of wild type RV in vitro, it likely forms in vivo and plays an important role in facilitating protein secretion. Additionally, our results revealed that the N-terminal part of the RV can significantly stabilize its C-terminal structure. Our study paves the way for further investigations into the structure and functions of MpIBP that help bacteria survive in challenging environments.

Dielectric engineering enable to lateral anti-ambipolar MoTe2heterojunction.

Atomically two-dimensional (2D) materials have generated widespread interest for novel electronics and optoelectronics. Specially, owing to atomically thin 2D structure, the electronic bandgap of 2D semiconductors can be engineered by manipulating the surrounding dielectric environment. In this work, we develop an effective and controllable approach to manipulate dielectric properties of h-BN through gallium ions (Ga+) implantation for the first time. And the maximum surface potential difference between the intrinsic h-BN (h-BN) and the Ga+implanted h-BN (Ga+-h-BN) is up to 1.3 V, which is characterized by Kelvin probe force microscopy. More importantly, the MoTe2transistor stacked on Ga+-h-BN exhibits p-type dominated transfer characteristic, while the MoTe2transistor stacked on the intrinsic h-BN behaves as n-type, which enable to construct MoTe2heterojunction through dielectric engineering of h-BN. The dielectric engineering also provides good spatial selectivity and allows to build MoTe2heterojunction based on a single MoTe2flake. The developed MoTe2heterojunction shows stable anti-ambipolar behaviour. Furthermore, we preliminarily implemented a ternary inverter based on anti-ambipolar MoTe2heterojunction. Ga+implantation assisted dielectric engineering provides an effective and generic approach to modulate electric bandgap for a wide variety of 2D materials. And the implementation of ternary inverter based on anti-ambipolar transistor could lead to new energy-efficient logical circuit and system designs in semiconductors.