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Mechanical activation of reactions can reduce significantly the amounts of solvent and energy required to form covalent organic bonds.

 

A modified atomic force microscope is used to probe activation effects that may accelerate reactions in a ball mill. 

Every animal secretes mucus, placing them among the most diverse biological materials. Mucus hydrogels are complex mixtures of water, ions, carbohydrates, and proteins. Uncertainty surrounding their composition and how interactions between components contribute to mucus function complicates efforts to exploit their properties. There is substantial interest in commercializing mucus from the garden snail,Cornu aspersum, for skincare, drug delivery, tissue engineering, and composite materials.C. aspersumsecretes three mucus—one shielding the animal from environmental threats, one adhesive mucus from the pedal surface of the foot, and another pedal mucus that is lubricating. It remains a mystery how compositional differences account for their substantially different properties. Here, we characterize mucus proteins, glycosylation, ion content, and mechanical properties that could be used to provide insight into structure-function relationships through an integrative “mucomics” approach. We identify macromolecular components of these hydrogels, including a previously unreported protein class termed Conserved Anterior Mollusk Proteins (CAMPs). Revealing differences betweenC. aspersummucus shows how considering structure at all levels can inform the design of mucus-inspired materials.

 

Tuning solubility and mechanical activation alters the stereoselectivity of the [2 + 2] photochemical cycloaddition of acenaphthylene. Photomechanochemical conditions produce the syn cyclobutane, whereas the solid-state reaction in the absence of mechanical activation provides the anti . When the photochemical dimerization occurs in a solubilizing organic solvent, there is no selectivity. Dimerization in H 2 O, in which acenaphthylene is insoluble, provides the anti product. DFT calculations reveal that insoluble and solid-state reactions proceed via a covalently bonded excimer, which drives anti selectivity. Alternatively, the noncovalently bound syn conformer is more mechanosusceptible than the anti , meaning it experiences greater destabilization, thereby producing the syn product under photomechanochemical conditions. Cyclobutanes are important components of biologically active natural products and organic materials, and we demonstrate stereoselective methods for obtaining syn or anti cyclobutanes under mild conditions and without organic solvents. With this work, we validate photomechanochemistry as a viable new direction for the preparation of complex organic scaffolds. 

Hypersurface photolithography (HP) is a printing method for fabricating structures and patterns composed of soft materials bound to solid surfaces and with ∼1 micrometer resolution in the x , y , and z dimensions. This platform leverages benign, low intensity light to perform photochemical surface reactions with spatial and temporal control of irradiation, and, as a result, is particularly useful for patterning delicate organic and biological material. In particular, surface-initiated controlled radical polymerizations can be leveraged to create arbitrary polymer and block-copolymer brush patterns. Here we will review advances in instrumentation architectures that have made these hypersurfaces possible, and the investigations and development of surface-based organic chemistry and grafted-from photopolymerizations that have arisen through these investigations. Over the course of this discussion, we describe specific applications that have benefited from HP. By combining organic chemistry with the instrumentation developed, HP has ushered in a new era of surface chemistry that will lead to new fundamental science and previously unimaginable technologies. 

Mucins are a highly glycosylated protein family that are secreted by animals for adhesion, hydration, lubrication, and other functions. Despite their ubiquity, animal mucins are largely uncharacterized. Snails produce mucin proteins in their mucous for a wide array of biological functions, including microbial protection, adhesion and lubrication. Recently, snail mucins have also become a lucrative source of innovation with wide ranging applications across chemistry, biology, biotechnology, and biomedicine. Specifically, snail mucuses have been applied as skin care products, wound healing agents, surgical glues, and to combat gastric ulcers. Recent advances in integrated omics (genomic, transcriptomic, proteomic, glycomic) technologies have improved the characterization of gastropod mucins, increasing the generation of novel biomaterials. This perspective describes the current research on secreted snail mucus, highlighting the potential of this biopolymer, and also outlines a research strategy to fulfill the unmet need of examining the hierarchical structures that lead to the enormous biological and chemical diversity of snail mucus genes. 

We report supramolecular photocatalytic hydrogels, produced by the enzymatically driven self-assembly of low molecular weight gelators (LMWGs). These LMWG precursors are composed of the organic chromophore diketopyrrolopyrrole (DPP), which is bi-functionalized with a series of amino acid (Phe, Tyr, Leu) methyl esters. In situ enzymatic hydrolysis of these photoactive precursors results in supramolecular hydrogels that provide a high density of photocatalytic sites. Under visible light irradiation these hydrophobic fibers recruit the reaction substrates and also produce 1 O 2 , which is used here for the photooxidation of thioanisole (aromatic substrate) and cyclohexyl methyl sulfide (aliphatic substrate), with yields as high as 100% and without over-oxidation. Finally, we demonstrate that the nature of the amino acids in the LWMGs has a central role in dictating J-/H-/mixed state aggregates, gel properties, and, hence, the efficiency of chemoselective photooxidation of thioanisole and cyclohexyl methyl sulfide inside these hydrogels.