An investigation on the vibrational analysis, molecular structure and interaction with the cellulase enzymes of the cellulose I alpha and cellulose I beta: DFT calculations, docking simulations

Molecular docking is one of the most widely used techniques for simulating molecular interactions between molecules and forecasting the mode of binding and affinities between them. Due to the presence of structure-function relationship, in this study firstly, the molecular structures of the cellulose I(alpha) and I(beta) molecules were optimized and their most stable structures were determined by density functional theory (DFT) using B3LYP method with 6-31G(d,p) basis set. The vibrational wavenumbers of 1-ring, 2-ring, 3-ring, and 4-ring structures of cellulose I(alpha) and I(beta) were calculated using the same level of theory. Reliable vibrational assignments were made based on potential energy distribution (PED %) of the vibrational modes. The energy gap (Eg = ELUMO - EHOMO) of the cellulose Ia and cellulose Ib was found to be 8.286 eV and 7.965 eV, respectively. To identify the molecular interactions between cellulose Ia and Ib ligands and the cellulase enzymes, molecular docking studies were performed. The molecular docking results revealed the strong interaction of the cellulose Ia and Ib with Endoglucanase enzyme (-6.4 and -6.3 kcal/mol, respectively), enzyme β-glucosidase (-5.3 and -5.2 kcal/mol, respectively), and Exoglucanase enzyme (-6.1 and -6.2 kcal/mol, respectively). KEY WORDS: Cellulose I alpha, Cellulose I beta, Density functional theory, Molecular docking Bull. Chem. Soc. Ethiop. 2025, 39(10), 2041-2064. DOI: https://dx.doi.org/10.4314/bcse.v39i10.12