Bio Focus: Graphene serves as trans-electrode membrane for DNA molecules
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aij /a0
t (s)
aij aij Measurement of normal modes and density of states in a disordered colloidal crystal, where ∆aij/āij stands for probability distribution of temporal fluctuations in nearest-neighbor spacing, ∆āij/a0 indicates the probability distribution of nearest-neighbor spacing in the equilibrium configuration, and ∆t (s) is change in time in seconds. Reproduced with permission from Science 329 (2010) DOI: 10.1126/ science.1187988; p.656. © 2010 AAAS.
Bio Focus Graphene serves as trans-electrode membrane for DNA molecules
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esearchers S. Garaj, D. Branton, and J.A. Golovchenko of Harvard University, and their colleagues from Harvard and the Massachusetts Institute of Technology have demonstrated that graphene can act as an artificial membrane separating two liquid reservoirs. As reported in the cover story of the September 9th issue of Nature (DOI: 10.1038/ nature09379; p. 190), by drilling a nanopore in the graphene membrane, the researchers were able to measure exchange of ions through the pore and demonstrated that a long DNA molecule can be pulled through the graphene nanopore just as a thread is pulled through the eye of a needle. “By measuring the flow of ions passing through a nanopore drilled in graphene we have demonstrated that the thickness of graphene immersed in liquid is less than 1 nm thick, or many times thinner than the very thin membrane which separates a single animal or human cell from its surrounding environment,” said lead author Slaven Garaj, a research associate in the Department of Physics at Harvard. “This makes graphene the thinnest membrane able to separate two liquid compartments
disordered atomic system have not been experimentally measured because tracking the dynamics of individual atoms directly is experimentally not feasible. Normal modes and the DOS of any material provide a basis for understanding thermal, mechanical, and transport properties. As reported in the August 6th issue of Science (DOI: 0.1126/ science.1187988; p. 656), the researchers experimentally measured the normal modes and the energies of the normal modes. From these experiments, they deduced the average particle separations to demonstrate the high degree of geometrical order in their system. The figure shows an average mean squared displacement (MSD) with
a clear plateau which is an indication of solid-like behavior and the absence of diffusion. The team in determining the normal modes observed the spectrum energy eigenvalues converged by 20,000 independent observations of the displacement field. The researchers observed a Debyelike behavior at low energies, with a Boson peak at higher energy. According to the researchers, this general procedure will be a vital tool to identify the impacts at particle level of different types of disorder on the structure of the normal modes and elasticity that are present in various atomic, molecular, and colloidal crystals and glasses. Jean L.W. Njoroge
from each other. The thickness of the membrane was determined by its interaction with water
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