Table 3. Second-order rate constants for formation of DNA–DNA and DNA–RNA duplexes from the single strands (using fluorescein-labeled DNA 2/RNA 2).

DNA 1 sample	DNA 2	DNA 2	RNA 2
	100 mM NaCl (M–1s–1)	500 mM NaCl (M–1s–1)	100 mM NaCl (M–1s–1)
O-Propyl	9.08 (± 0.2) × 104	4.46 (± 0.1) × 105	1.20 (± 0.02) × 105
O-Methoxyethyl	1.45 (± 0.03) × 105	5.91 (± 0.12) × 105	3.77 (± 0.07) × 105
O-Aminopropyl	5.60 (± 0.1) × 107	3.19 (± 0.06) × 107	4.90 (± 0.1) × 107
Control (P=O)	5.28 (± 0.1) × 105	7.22 (± 0.15) × 106	9.96 (± 0.02) × 105
Fluoro (P=S)	1.18 (± 0.02) × 106	2.47 (± 0.05) × 106	n.d.
Control (P=S)	1.01 (± 0.02) × 106	7.36 (± 0.15) × 106	1.50 (± 0.03) × 106

Measured in 10 mM phosphate buffer pH 7.0, 20°C, 100 or 500 mM NaCl using a stopped-flow analyzer in emission mode.

n.d., not done.