CONTROLLED DENATURATION OF DNA BY GOLD NANOPARTICLES
DNA hybridization is widely used to detect target sequences, both in the laboratory and in clinical diagnosis. Before hybridization can occur, the DNA double helix must be denatured into single strands. This is accomplished by the heating of bulk DNA. However, newly emerging nanotechnology may allow specific individual DNA molecules to be dissociated when required.
Nanoparticles of about 1.4 nm and containing fewer than 100 atoms of gold are attached to double-stranded DNA. When the structure is exposed to radio waves (generated by an alternating magnetic field), the gold acts as an antenna. It absorbs energy and heats the DNA molecule to which it is attached. This melts the DNA double helix and converts it to single strands. Heating extends over a zone of about 10 nm so surrounding molecules are unaffected. The heat is dissipated in less than 50 picoseconds, so the DNA may be rapidly switched between the double- and single-stranded states by turning the magnetic field on and off. The procedure may be applied to dsDNA made of two separate single strands (Fig. 7.19) or to stem-and-loop structures formed by folding from a single strand of DNA.
Practical applications are several years away. However, because radio waves penetrate living tissue very effectively, it may eventually be possible to control the behavior of individual DNA molecules from outside an organism. Metal antennas of different materials or sizes could be used to tune different DNA molecules to radio waves of different frequencies.