Table 1.

Polynucleotide and oligonucleotide samples used

Mixture	Nucleic acid	λ (nm)	ɛa (M−1 cm−1)	Tm (°C)
Sequenceb	[Poly(dA–dT)]2	262	6600	32.3
	Poly(dA)·poly(dT)	260	6000	39.7
	Poly(dA–dC)·poly(dG–dT)	258	6500	63.2
	Poly(dC)·poly(dG)	253	7400	73.1
	[Poly(dC–dG)]2	254	8400	87.8
Structurec	Poly(dA)·poly(dT)	260	6000	63.2
	Poly(rA)·poly(rU)	260	7140	52.6
	Poly(dA)·poly(rU)	257	6500	38.6
	Poly(rA)·poly(dT)	260	6230	60
Oligonucleotided	1. T2 (CC)10 T2 + T2 (GG)10 T2	260	133,148	51
		260	270 478
	2. T2 (AC)10 T2 + T2 (GT)10 T2	260	197 120	63.9
		260	237 000
	3. T2 (AG)10 T2 + T2 (CT)10 T2	260	263 907	71.9
		260	185 789

^aConcentration units of the extinction coefficient are expressed in terms bases for polynucleotides or strands for oligonucleotides. The molar extinction coefficients for single-stranded oligonucleotides were determined by means of a colorimetric phosphate assay (46).

^bThe concentration of each polynucleotide in this mixture is 40 µM (bp). The experiments were conducted in a buffer containing 1.5 mM Na₂HPO₄, 0.5 mM NaH₂PO₄ and 0.25 mM Na₂EDTA at pH 7.0.

^cThe concentration of each polynucleotide is 10 µM (bp). The experiments were conducted in a buffer containing 1.5 mM Na₂HPO₄, 0.5 mM NaH₂PO₄, 0.25 mM Na₂EDTA and 46.25 mM NaCl at pH 7.0.

^dThe concentration of each oligonucleotide is 2 µM (strand). The experiments were conducted in a buffer containing 6 mM Na₂HPO₄, 2 mM NaH₂PO₄, 1 mM Na₂EDTAand 185 mM NaCl at pH 7.0.