Molecular muscle does the job
Chemists often wish they could reach into a test tube and physically force a chemical reaction — and now they’ve come pretty darn close. In a feat of molecular arm-twisting, researchers attached polymer chains to an extremely stable ring-shaped molecule and tore it in two (SN Online: 9/15/11). The new approach split the triazole ring, a compound found in many drugs and fungus-fighting chemicals, into its molecular building blocks, reversing the reaction that brought the ring together.
“It’s a way to almost literally put your hands on molecules and twist them or turn them in whatever way you want,” says Christopher Bielawski of the University of Texas at Austin, who led the research. Chemists often use heat to break compounds apart, but the approach can yield a variety of molecular pieces. And heat and other chemical tricks don’t work on the triazole ring, because it is too tough.
Bielawski and his students attached chains to opposite sides of the rings in solution and then inserted an ultrasound probe. The probe generated imploding bubbles, creating tiny pockets of suction that yanked on the polymer chains and tore open the rings. The technique reverses a reaction that was thought to go in only one direction, suggesting a new means for strong-arming other molecules into interesting new chemistry.
“This work is going to have a big impact,” says Virgil Percec of the University of Pennsylvania. “It opens the door to unexpected new opportunities.” — Rachel Ehrenberg
O. BOLTON AND A. MATZGER/ANGEWANDTE CHEMIE INTERNATIONAL EDITION 2011
Timely boom By reining in a supersensitive explosive with good old-fashioned TNT, chemists have created a new crystal that can be stored and transported safely and then quickly converted to an active, superexplosive form (SN: 10/22/11, p. 10).
Absent interface About a quarter of the molecules in water’s superthin surface layer can’t decide whether to be liquid or gas, but the ambiguity doesn’t affect the water below (SN: 7/2/11, p. 13).
Table gets flex The atomic weights of 10 chemical elements in the periodic table are listed as ranges rather than single numbers, the first phase in an overhaul of almost every element in the table (SN: 1/29/11, p. 5).
Microbial work-around Researchers discover the “methylaspartate cycle,” a means for synthesizing cellular building blocks cobbled together by salt-loving microbes (SN: 2/12/11, p. 14).
High blocker Modifying the active ingredient in marijuana, THC, may allow researchers to quash the high that THC produces. The dopey sensation is an unwanted side effect for some people who use marijuana for its medical effects (SN Online: 4/24/11).
Green flame fighters Flexible coatings mere billionths of a meter thick keep cotton clothing from going up in flames and plastic foam from melting — and they’re safer than the toxic flame retardants currently in use (SN: 9/24/11, p. 17).
Bottom up With the help of template molecules, scientists manage to string small biologically important molecules together into larger, ringed structures (SN: 1/29/11, p. 16).
DEET’s deets The repellent works its magic from afar by gumming up insects’ sniffing machinery (SN: 10/22/11, p. 10).
Lab relief Chemists have synthesized a pain-relieving extract, called conolidine, from the bark of a tropical shrub, paving the way for new drugs that lack the unwanted side effects of many opiate-based meds (SN Online: 5/23/11).
One poison A type of caterpillar makes cyanide via the same cellular machinery as its host plant, the first known example of organisms from different kingdoms evolving the same biochemical treachery (SN: 5/7/11, p. 11).
Python elixir A mix of fatty acid compounds identified in pythons can spur an exercise-like boost in the size of mouse hearts (SN: 12/3/11, p. 12).
Plastic isn’t over A new polymer can be heated and reconfigured into complex shapes without losing its strength, meaning broken bits can be repurposed
(SN: 12/17/11, p. 8).