Table 2.

DNA strand exchange in trans is independent of dsDNA melting temperature

ssDNA substrate (#)	Length (nucleotides)	dsDNA substrate (#)	ssDNA within filament (#)	Initial rate (%/min)a	Tm (°C); in 1 m NaCl
40	32	39, 40	43	2.5 ± 0.3	89
43	33	43, 72	5	1.9 ± 0.2	78.7
1	63	1, 2	9	1.1 ± 0.1	86.7
5	32	5, 6	43	1.0 ± 0.2	78.7
91	90	90, 91	71	0.2 ± 0.1	94.4
20	32	19, 20	43	0.1 ± 0.5	67.2
39	32	39, 40	43	0.1 ± 0.04	89

^aThe initial rate during the first 1–2 min (10–15 min for ssDNA #20, #39, and #91) of DNA strand exchange in trans was obtained by subtracting the rate of spontaneous thermal DNA strand exchange for each pair of DNA substrates, from the observed rate of RecA protein-promoted reaction. The spontaneous reaction rates (%/min) were 0.06, 0.12, 0.05, 0.1, 0.02, 0.13, and 0.03 for oligonucleotides #40, #43, #1, #5, #91, #20, and #39 respectively.