Jeudi 16 décembre 2004
Chemical reactions usually involve the study of a very large number ( 10^23) of reagents and various reaction pathways. It is therefore difficult, using these bulk methods, to study the existence of intermediate states or side reactions and the associated kinetic constants. A new technique has been developed in our laboratory that allows us to study a single chemical reaction, i.e. to observe individual binding events or bond-making and bond-breaking steps with sub-millisecond time-resolution.
The technique involves the recording of the ionic current driven through a single pore in a membrane. The pore (a protein) has been engineered such as to allow for a given chemical reaction to occur in its midst, in which case the current through the pore is reduced. The various chemical interactions observed in this way include the reversible association of proteins with various ligands, the formation of DNA duplexes and a variety of covalent reactions including light-activated ones. This single pore chemistry can be used as a very sensitive sensor for a variety of molecules. It can be used both to identify an analyte and measure its concentration. Further, several analytes can be detected simultaneously with a single sensor element.