Spreadsheet software for thermodynamic melting point prediction of oligonucleotide hybridization with and without mismatches

The use of thermodynamic parameters for the calculation of oligonucleotide duplex stability provides the best estimates of oligonucleotide melting tem peratures (T-m). Such estimates can be used for evidence-based design of mo lecular biological experiments in which oligonucleotide melting behavior is a critical issue, such as temperature or denaturing gradient gel electroph oreses, Southern blotting or hybridization probe assays on the LightCycler( TM) We have developed a user friendly program for T-m calculation of matche d and mismatched probes using the spreadsheet software Microsoft Excel(R). The most recently published values for entropy and enthalpy of Watson-Crick pairs are used, and salt and oligonucleotide concentrations are considered . The 5' and 3' end stability is calculated for the estimation of primer sp ecificity. In addition, the influence of all possible mutations under a giv en probe can be calculated automatically. The experimental evaluation of pr edicted T-m with the LightCycler; based on 14 hybridization probes for diff erent gene loci, showed an excellent fit between measured results and val l ies predicted with the thermodynamic model in 14 matched 25 single mismatch ed and 8 two-point mismatched assays (r = 0.98; Sy.x = 0.90; y = 1.01 x -0. 38). This program is extremely useful for the de sign of oligonucleotide pr obes because the use of probes that do not discriminate with a reasonable T -m difference between wild-type and mutation can be avoided in advance.