Determination of molecular size of O-(2-hydroxyethyl)cellulose (HEC) and its relationship to the mechanism of enzymatic hydrolysis by cellulases

Z-average root mean square end-to-end distance 〈ro2〉z1/2 and radius of gyration 〈so2〉z1/2 for 13 samples of O-(2-hydroxyethyl)cellulose (HEC) of different molecular weights were derived from Gel Permeation Chromatography and intrinsic viscosity measurements with water as a solvent. At 40 °C and pH 4.5, contraction of chain dimensions is observed, compared with the sizes observed under neutral conditions at room temperature. The effect is lower for samples with higher molecular weights. Values of 〈ro2〉40/DPz also indicate that chain flexibility increases at higher temperature and acidic conditions. From the analysis of molecular weight dependence of 〈so2〉 z1/2, Flory exponent υ was derived at 40 °C and pH 4.5. A value of υ = 0.70 ± 0.02 was recorded, which indicates that a relatively stiff chain is present under these conditions. Finally, different equations to calculate persistence length Lp were evaluated. Values in the range of 260–400 Å were derived for persistence length. Implications of chain conformation in the enzymatic action of cellulases are also discussed.