DAN BRANTON
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JENE GOLOVCHENKO
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We are developing a single channel recording method that (1) translates
DNA bases into electronic signals directly and quickly; (2) does
so in a manner that is compatible with high levels of nano-fabrication;
(3) can read very long stretches of DNA so that errors associated
with repetitive sequences and the assembly of contiguous elements
can be minimized. We believe these design criteria can be met
by an instrument which draws single molecules of DNA through a
small channel or pore that is integral to a sensitive detector.
Thus far, we have been able to show that an electric field can
drive single stranded RNA and DNA molecules through a ca. 2 nm diameter ion channel in a lipid bilayer membrane. Because
the channel diameter was selected to accommodate only a single
strand of RNA or DNA, each polymer must travers the membrane as
an extended chain. During its traverse, the DNA partially blocks
the channel. As a result the passage of each molecule is detected
as a transient decrease of ionic current whose duration is proportional
to polymer length and whose magnitude is dependent on the nature
of the passing nucleotide. Channel blockades can therefore be
used to measure polynucleotide length and to distinguish between
purines and pyrimidines. With further improvements, the method
could in principle provide direct, high-speed detection of the
sequence of bases in single molecules of DNA or RNA.
References:
Experimental work:
1. Kasianowicz, J. et al. (1996) Characterization of individual polynucleotide molecules using a membrane channel. P.N.A.S., USA 93:13770-13773.
Related Theory:
2. Sung, W. and Park, P.J. (1996) Polymer translocation through a pore in a membrane. Phys. Rev. Lett. 77:783-786.
3. Zimm, B. H. and Levene, S. D. (1992). Problems and prospects in the theory of gel electrophoresis of DNA. Q Rev. Biophys. 25:171-204.