Spectral analysis for base composition of DNA undergoing melting.

A microcomputer-controlled spectrophotometer is described for obtaining the base composition of melting domains in DNA from derivative melting curves. Values have been determined for the differential molar extinction coefficients for the A-T and G-C base pair at the three wavelengths most useful for spectral analysis of base composition, 260, 270 and 282 nm. The average RMS error for these values was 29 l(mol X cm)-1 for the melting of 14 DNA specimens ranging in base composition from 0-0.72 F(G + C). A precision of approximately 1% in base composition of domains is possible. Such analysis is useful for confirming or establishing assignments of domains to particular subtransitional features in high resolution melting curves.