High throughput single-molecule DNA screening based be electrophoresis

In electrophoresis, the migration velocity is used for sizing DNA and prote ins or for distinguishing molecules based on charge and hydrodynamic radius . Many protein and DNA assays relevant to disease diagnosis are based on su ch separations. However, standard protocols are not only slow (minutes to h ours) but also insensitive (many molecules in a detectable band). We succes sfully demonstrated a high-throughput imaging approach that allows determin ation of the individual electrophoretic mobilities of many molecules at a t ime. Each measurement only requires a few milliseconds to complete. This op ens up the possibility of screening single copies of DNA or proteins within single biological cells for disease markers without performing polymerase chain reaction or other biological amplification. The purpose is not to sep arate the DNA molecules but to identify each one on the basis of the measur ed electrophoretic mobility. We developed three different procedures to mea sure the individual molecular mobilities. The results correlate well with c apillary electrophoresis (CE) experiments for the same samples (2-49 kb dsD NA) under identical separation conditions. The implication is that any elec trophoresis protocols from slab gels to CE should be adaptable to single-mo lecule screening for disease diagnosis.