Pharmaceutical companies are using artificial intelligence to streamline the process of discovering new medicines. Machine-learning models can propose new molecules that have specific properties which could fight certain diseases, doing in minutes what might take humans months to achieve manually. But there's a major hurdle that holds these systems back: The models often suggest new molecular structures that are difficult or impossible to produce in a laboratory. If a chemist can't actually make the molecule, its disease-fighting properties can't be tested. A new approach from MIT researchers constrains a machine-learning model so it only suggests molecular structures that can be synthesized.
Researchers have controlled a chemical reaction by squeezing specially designed molecules between a pair of diamonds. This could be a more precise way to make custom molecules on demand for use in pharmaceuticals. There are several ways to initiate a chemical reaction that breaks molecular bonds or moves electrons around. You can add heat, electricity or light, or simply pull the molecule apart.
During a chemical reaction, the reorganization of solvent molecules not directly in contact with reactants and products is normally viewed as a simple diffusion response. Wang et al. studied molecular diffusion in six common reactions—including the copper-catalyzed click reaction and the Diels-Alder reaction—with pulsed-field gradient nuclear magnetic resonance. They observed a boost in mobility relative to Brownian diffusion that was stronger for the catalyzed reactions that were studied. The mobilities for the click reaction were verified with a microfluidic gradient method. They argue that energy release produces transient translational motion of reacting centers that mechanically perturbs solvent molecules. Science , this issue p.  Mobility of reactants and nearby solvent is more rapid than Brownian diffusion during several common chemical reactions when the energy release rate exceeds a threshold. Screening a family of 15 organic chemical reactions, we demonstrate the largest boost for catalyzed bimolecular reactions, click chemistry, ring-opening metathesis polymerization, and Sonogashira coupling. Boosted diffusion is also observed but to lesser extent for the uncatalyzed Diels-Alder reaction, but not for substitution reactions SN1 and SN2 within instrumental resolution. Diffusion coefficient increases as measured by pulsed-field gradient nuclear magnetic resonance, whereas in microfluidics experiments, molecules in reaction gradients migrate “uphill” in the direction of lesser diffusivity. This microscopic consumption of energy by chemical reactions transduced into mechanical motion presents a form of active matter. : /lookup/doi/10.1126/science.aba8425
Cosmic rays may have triggered chemical reactions to create some of the key building blocks needed for life in ice floating in the frigid space between stars. Astronomers have discovered that complex organic molecules like sugars and amides, which form a key part of proteins, can form in balls of ice between stars. It could help to support theories that life – or the precursors of life – formed far out into space and were carried to the Earth on comets. Some of the key building blocks for life could have formed in ice in interstellar space in chemical reactions driven by cosmic rays. The study also raises hopes that such interstellar balls of ice could have helped life to form on other planets.
Chemists have tied the tightest knot yet, a nano-sized structure with eight crossings and just 192 atoms. The advance could help researchers learn how to manipulate materials at the atom level to develop stronger, more flexible, and lighter-weight cloth or construction materials. The knot, described in today's issue of the journal Science, measures 20 nanometers in length, about 100,000 times smaller than the head of a pin. Why make a knot that's so small? I'll give you a two-part answer.