Weighing and imaging molecules one at a time Bu

Weighing and imaging molecules one at a time

But mass spectrometry often cannot discriminate subtle but crucial differences in molecules having similar mass-to-charge ratios. "With mass spectrometry today," explains Roukes, "large molecules and molecular complexes are first chopped up into many smaller pieces, that is, into smaller molecule fragments that existing instruments can handle. These different fragments are separately analyzed, and then bioinformatics—involving computer simulations—are used to piece the puzzle back together. But this reassembly process can be thwarted if pieces of different complexes are mixed up together."

With their devices, Roukes and his colleagues can measure the mass of an individual intact molecule. Each device—which is only a couple millionths of a meter in size or smaller—consists of a vibrating structure called a nanoelectromechanical system (NEMS) resonator. When a particle or molecule lands on the nanodevice, the added mass changes the frequency at which the structure vibrates, much like putting drops of solder on a guitar string would change the frequency of its vibration and resultant tone. The induced shifts in frequency provide information about the mass of the particle. But they also, as described in the new paper, can be used to determine the three-dimensional spatial distribution of the mass: i.e., the particle's shape


Read more at: http://phys.org/news/2015-04-reveal-mass-molecules.html#jCp


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