资源环境科技发展态势分析平台

Strain engineering is a powerful tool with which to enhance semiconductor device performance(1,2). Halide perovskites have shown great promise in device applications owing to their remarkable electronic and optoelectronic properties(3-5). Although applying strain to halide perovskites has been frequently attempted, including using hydrostatic pressurization(6-8), electrostriction(9), annealing(10-12), van der Waals force(13), thermal expansion mismatch(14), and heat-induced substrate phase transition(15), the controllable and device-compatible strain engineering of halide perovskites by chemical epitaxy remains a challenge, owing to the absence of suitable lattice-mismatched epitaxial substrates. Here we report the strained epitaxial growth of halide perovskite single-crystal thin films on lattice-mismatched halide perovskite substrates. We investigated strain engineering of a-formamidinium lead iodide (alpha-FAPbI(3)) using both experimental techniques and theoretical calculations. By tailoring the substrate composition-and therefore its lattice parameter-a compressive strain as high as 2.4 per cent is applied to the epitaxial alpha-FAPbI(3) thin film. We demonstrate that this strain effectively changes the crystal structure, reduces the bandgap and increases the hole mobility of alpha-FAPbI(3). Strained epitaxy is also shown to have a substantial stabilization effect on the alpha-FAPbI(3) phase owing to the synergistic effects of epitaxial stabilization and strain neutralization. As an example, strain engineering is applied to enhance the performance of an alpha-FAPbI(3)-based photodetector.

The structure of human diacylglycerol O-acyltransferase 1, a membrane protein that synthesizes triacylglycerides, is solved with cryo-electron microscopy, providing insight into its function and mechanism of enzymatic activity.

Diacylglycerol O-acyltransferase 1 (DGAT1) synthesizes triacylglycerides and is required for dietary fat absorption and fat storage in humans(1). DGAT1 belongs to the membrane-bound O-acyltransferase (MBOAT) superfamily, members of which are found in all kingdoms of life and are involved in the acylation of lipids and proteins(2,3). How human DGAT1 and other mammalian members of the MBOAT family recognize their substrates and catalyse their reactions is unknown. The absence of three-dimensional structures also hampers rational targeting of DGAT1 for therapeutic purposes. Here we present the cryo-electron microscopy structure of human DGAT1 in complex with an oleoyl-CoA substrate. Each DGAT1 protomer has nine transmembrane helices, eight of which form a conserved structural fold that we name the MBOAT fold. The MBOAT fold in DGAT1 forms a hollow chamber in the membrane that encloses highly conserved catalytic residues. The chamber has separate entrances for each of the two substrates, fatty acyl-CoA and diacylglycerol. DGAT1 can exist as either a homodimer or a homotetramer and the two forms have similar enzymatic activity. The N terminus of DGAT1 interacts with the neighbouring protomer and these interactions are required for enzymatic activity.