It enables the pump to use redox reactions and heat to fish two cyclobis(paraquat-p-phenylene) rings out of solution and thread them, one at a time, onto a dumbbell-shaped molecule, where the rings become trapped in a high energy state. To start the pumping process, the ring in solution and viologen on the dumbbell are reduced, making them mutually attractive. The attraction pulls the ring over a dimethylpyridinium end cap on the dumbbell, and the ring forms a complex with viologen. Oxidation then returns the ring and viologen to their original states, making them repel one another and driving the ring toward an isopropylphenylene barrier. Mild heating enables the ring to slip over the barrier. This traps the ring, far from equilibrium, on an oligomethylene chain terminated with a diisopropylphenyl end cap. The second ring slips onto the dumbbell the same way. It takes about two hours to capture each ring. Relative to previous work in the field, “the most remarkable improvement” of the new study is that it got two rings together onto a chain instead of just one, Sauvage says. Stoddart notes that the design is so versatile that threading more than two rings, and even an unlimited number, may eventually be possible. /articles/93/i21/Molecular-Pump-Mimics-Natural-Carrier.html 20150521 Molecular Machines: Synthetic system threads two rings onto a dumbbell-shaped rod News of The Week 93 21 /magazine/93/09321.html /departments/.html /collections/notw.html Molecular Pump Mimics Natural Carrier Proteins Science & Technology Stu Borman This animation shows the steps and energetics (E) of the pumping mechanism used to move two rings onto the right side a dumbbell-shaped molecule.
by Stu Borman |
May 21, 2015