PH-DEPENDENT SPECIFIC BINDING AND COMBING OF DNA

Recent developments in the rapid sequencing, mapping, and analysis of DNA rely on the specific binding of DNA to specially treated surfaces. We show here that specific binding of DNA via its unmodified extremit ies can be achieved on a great variety of surfaces by a judicious choi ce of the pH. On hydrophobic surfaces the best binding efficiency is r eached at a pH of similar to 5.5. At that pH a similar to 40-kbp DNA i s 10 times more likely to bind by an extremity than by a midsegment, A model is proposed to account for the differential adsorption of the m olecule extremities and midsection as a function of pH. The pH-depende nt specific binding can be used to align anchored DNA molecules by a r eceding meniscus, a process called molecular combing. The resulting pr operties of the combed molecules will be discussed.