Commercially available cellulose nanocrystals (CNCs) are typically manufactured via sulfuric acid hydrolysis which adds a surface sulfate half-ester functionality. Here, we observe the reciprocal effect of sulfate half-ester groups and oxidative modification of CNCs, where the oxidation is targeted for the hydroxyl groups but the sulfate half-esters groups and their electro-chemical properties are affected. We demonstrate periodate and enzymatic oxidation. Periodate oxidation is a modification that introduces aldehyde functionality to cellulose at carbons in positions 2 and 3 in the anhydroglucose unit while the sulfate half-ester groups are considered to be located in carbon in position 6. However, we demonstrate that the charged groups, which decrease along with the modification, slowed down the oxidation reaction. The presence of sulfate groups has also been shown to slow down enzymatic hydrolysis by canonical cellulases. Here we extend the enzymatic observations to Lytic polysaccharide monooxygenases (LPMOs). We will present findings on oxidation kinetics, product composition and dimensions, and colloidal properties of the suspensions.