Photocleavage control of nucleated DNA nanosystems--the influence of surface strand sterics

We use sterically inaccessible 'seed' strands, released from a surface into solution by photocleavage to initiate a nucleated DNA polymerization reaction. We demonstrate control of the quantity of 'seed' release and that hairpin steric protection of the 'seed' leads to less 'leaky' surfaces. This polymerization is a model system for surface-photocleavage initiation of sub-stoichiometric reaction cascades; these cascades should find use as a component of labs-on-chips capable of bioanalytical and DNA-computing tasks.

Light-controlled tools

Spatial and temporal control over chemical and biological processes plays a key role in life, where the whole is often much more than the sum of its parts. Quite trivially, the molecules of a cell do not form a living system if they are only arranged in a random fashion. If we want to understand these relationships and especially the problems arising from malfunction, tools are necessary that allow us to design sophisticated experiments that address these questions. Highly valuable in this respect are external triggers that enable us to precisely determine where, when, and to what extent a process is started or stopped. Light is an ideal external trigger: It is highly selective and if applied correctly also harmless. It can be generated and manipulated with well-established techniques, and many ways exist to apply light to living systems--from cells to higher organisms. This Review will focus on developments over the last six years and includes discussions on the underlying technologies as well as their applications.

Photocontrolled binding and binding-controlled photochromism within anthracene-modified DNA

Modified DNA strands undergo a reversible light-induced reaction involving the intramolecular photodimerization of two appended anthracene tags. The photodimers exhibit markedly different binding behavior toward a complementary strand that depends on the number of bases between the modified positions. By preforming the duplex, photochromism can be suppressed, illustrating dual-mode gated behavior.