Sequences: Enter one or more pairs of sequences, in 5'-to-3' order, separated by semicolons. The letters 'A', 'C', 'G', 'T' and 'U' are recognized as the corresponding nucleotides. (Us are converted to Ts for DNA and vice versa for RNA.) All other letters are treated as unknown nucleotides; such unknowns are not permitted to form base pairs. All non-alphabetic characters are stripped out prior to processing.

Energy Rules: Choose whether to interpret sequences as DNA (the default) or RNA. Enter a hybridization temperature in °C. For DNA rules only, enter the concentrations of Sodium and Magnesium ions. (Salt conditions for RNA are fixed at [Na+] = 1 M and [Mg++] = 0 M.) Oligomer mode is the default; if polymer mode is chosen, [Mg++] is ignored.

Total strand concentration: Enter the total strand concentration in moles per liter. For heterodimers, half of this value will be assigned to each sequence.