The kinetics of oxidation of fats

A novel view on the mechanism of biological activity of antifreeze proteins

“…(23)) show that in water, Δ H (1) ≈ −6.0 kJ/mol ≈ −2.6 k B T 0 , so that An experimental estimate of B (≈ 0.85 k B T 0 near T 0 = 273 К) follows from the free energy of the ice/water interface (24), ≈32 erg/cm 2 , and because an H 2 O molecule occupies ≈ 10Å 2 of the interface B ≈ 320 × 10 −16 erg ≈ 1.9 kJ/mol, or B ≈ 0.85 k B T 0 per one surface H 2 O molecule. Thus, As a result, the transition state free energy for the pathway of a 3D ice crystal formation is estimated as Then, according to the transition state theory(25, 26) 25,26 , the time of appearance of an ice nucleus around one given H 2 O molecule can be estimated as , where τ is the time of addition of one more water molecule to the ice; it is no less than τ 0 ∼10 −12 s, the typical time of thermal vibrations at ≈273°K, or rather ∼10 −11 s, the time of overturning (27) of an H 2 O molecule diffusing in the water at ≈273°К. More accurately, the value of τ is estimated as the difference between the rates of water attachment to and detachment from the ice (17): , where ε ≈51 kJ/mol is the energy of ice sublimation (23); at T ≈273°К this gives Since after the formation of the ice nucleus the remaining H 2 O molecules attach to it more or less independently, the τ value is both the time of attachment of one H 2 O molecule to the ice and the time of growth of one layer of H 2 O molecules upon the ice.…”