Effects of Chlorophenoxy Herbicides and Their Main Transformation Products on DNA Damage and Acetylcholinesterase Activity

Table 2

Thermodynamic parameters of DNA thermal denaturation, obtained by UV spectroscopy, in solutions with different herbicides^a,b.

Compound	𝑡𝑚/°C	−Δ(𝐻260 (85°C))	Δ(Δ𝐻^∘vH)/kJ mol^−1	Δ(Δ𝑆^∘vH)/kJ K^−1 mol^−1
MCPA	63.4±0.6	0.06	21±8	0.06±0.02
	63.9±0.4	0.07	0	0
Mecoprop	63.7±0.6	0.03	7±7	0.02±0.02
	63.7±0.6	0.06	31±8	0.09±0.02
2,4-D	63.0±0.3	0	14±6	0.04±0.01
	63.2±0.6	0.03	9±8	0.03±0.02
Dichlorprop	64.1±0.5	0.03	46±7	0.13±0.01
	64.7±0.5	0.05	29±7	0.08±0.01
2,4-Dichlorophenol	64.3±0.5	0.07	15±6	0.04±0.01
	64.0±0.5	0.09	33±6	0.09±0.01
4-Chloro-2-methylphenol	64.3±0.3	0	15±5	0.04±0.01
	64.3±0.4	0.05	30±6	0.08±0.01
2,4-Dichloro-6-nitrophenol	63.5±0.5	0.05	0	0.08±0.01
	63.6±0.4	0.05	4±6	0.08±0.01
4-Chloro-2-methyl-6-nitrophenol	67.9±0.5	0.05	0	0.08±0.01
	70.8±0.5	1	42±7	0.08±0.02

a[DNA] = 7.7 × 10⁻⁵ mol dm⁻³, phosphate buffer solution, ionic strength = 0.01 mol dm⁻³. For each herbicide or TP, the top values correspond to a concentration of 5.1×10⁻⁵ mol dm⁻³ and the bottom values to 1.0×10⁻⁴ mol dm⁻³.
^bΔ(𝐻₂₆₀ (85^∘C)) = 𝐻₂₆₀(85^∘C)_{(DNA+herbicideorTP)} − 𝐻₂₆₀(85^∘C)_(DNA); Δ(Δ𝐻^∘_vH) = Δ𝐻^∘_{vH(DNA+herbicideorTP)} − Δ𝐻^∘_vH(DNA); Δ(Δ𝑆^∘_vH) = Δ𝑆^∘_{vH(DNA+herbicideorTP)} − Δ𝑆^∘_vH(DNA).