Topographic nanomanufacturing with a depth precision down to atomic dimension is of importance for advancement of nanoelectronics with new functionalities. Here we demonstrate a mask-less and chemical-free nanolithography process for regio-specific removal of atomic layers on a single crystalline silicon surface via shear-induced mechanochemical reactions. Since chemical reactions involve only the topmost atomic layer exposed at the interface, the removal of a single atomic layer is possible and the crystalline lattice beneath the processed area remains intact without subsurface structural damages. Molecular dynamics simulations depict the atom-by-atom removal process, where the first atomic layer is removed preferentially through the formation and dissociation of interfacial bridge bonds. Based on the parametric thresholds needed for single atomic layer removal, the critical energy barrier for water-assisted mechanochemical dissociation of Si–Si bonds was determined. The mechanochemical nanolithography method demonstrated here could be extended to nanofabrication of other crystalline materials.

In plants, geranylgeranyl diphosphate (GGPP) is produced by plastidic GGPP synthase (GGPPS) and serves as a precursor for vital metabolic branches, including chlorophyll, carotenoid, and gibberellin biosynthesis. However, molecular mechanisms regulating GGPP allocation among these biosynthetic pathways localized in the same subcellular compartment are largely unknown. We found that rice contains only one functionally active GGPPS, OsGGPPS1, in chloroplasts. A functionally active homodimeric enzyme composed of two OsGGPPS1 subunits is located in the stroma. In thylakoid membranes, however, the GGPPS activity resides in a heterodimeric enzyme composed of one OsGGPPS1 subunit and GGPPS recruiting protein (OsGRP). OsGRP is structurally most similar to members of the geranyl diphosphate synthase small subunit type II subfamily. In contrast to members of this subfamily, OsGRP enhances OsGGPPS1 catalytic efficiency and specificity of GGPP production on interaction with OsGGPPS1. Structural biology and protein interaction analyses demonstrate that affinity between OsGRP and OsGGPPS1 is stronger than between two OsGGPPS1 molecules in homodimers. OsGRP determines OsGGPPS1 suborganellar localization and directs it to a large protein complex in thylakoid membranes, consisting of geranylgeranyl reductase (OsGGR), light-harvesting-like protein 3 (OsLIL3), protochlorophyllide oxidoreductase (OsPORB), and chlorophyll synthase (OsCHLG). Taken together, genetic and biochemical analyses suggest OsGRP functions in recruiting OsGGPPS1 from the stroma toward thylakoid membranes, thus providing a mechanism to control GGPP flux toward chlorophyll biosynthesis.T erpenoids are one of the largest and most structurally diverse classes of plant primary and secondary metabolites and are involved in numerous physiological and ecological processes ranging from growth and development to communication, environmental adaptation, and defense (1, 2). All terpenoids derive from the universal five-carbon (C 5 ) units, isopentenyl diphosphate (IPP) and its allylic isomer dimethylallyl diphosphate (DMAPP), which are synthesized in plants by two compartmentally separated, but metabolically cross-talking, isoprenoid pathways, the mevalonate and methylerythritol phosphate pathways (3). IPP and DMAPP are subsequently used by short-chain prenyltransferases (PTSs) to produce prenyl diphosphate precursors: geranyl diphosphate (GPP, C 10 ), farnesyl diphosphate (FPP, C 15 ), and geranylgeranyl diphosphate (GGPP, C 20 ) (2, 4, 5). Short-chain PTSs determine not only the chain length of their products but also the compartmental localization of product biosynthesis. By catalyzing the branch-point reactions, they control precursor flux toward various classes of terpenoids.Among the prenyl diphosphate intermediates, GGPP biosynthesis represents an essential metabolic node, as this precursor is shared by several vital metabolic pathways, particularly in plastids, including the biosynthesis of carotenoids and their derivatives (e.g., plant hormones abscisic acid and ...

Rapid gelation and on‐demand dissolution are key characteristics governing the effectiveness of clinic hydrogel wound dressings. Here, an injectable self‐healing hydrogel with rapid gelation and cysteine‐specific on‐demand dissolution is designed to be used as wound dressings. The hydrogel is prepared based on the formation of tandem dynamic covalent bonds comprised of CC double bonds produced through the catalysis‐free Knoevenagel condensation reaction and boronate ester linkages. The prepared hydrogel displays excellent injectability and self‐healing ability, showing rapid cysteine‐triggered on‐demand dissolution owing to the formation of the thiazolidino boronate complex. When used as dressings for healing full‐thickness wounds, the hydrogel shows favorable biocompatibility, achieves rapid wound closure in seconds, and fast on‐demand dissolution for dressing changes. These data highlight the utility of the designed tandem dynamic covalent bonds‐based hydrogel dressings for promising wound healing applications.