Fig. 8. (a) The hydrolysis of 1,4-beta-linkages between N-acetyl-d-glucosamine (NAG) and N-acetylmuramic acid (NAM) residues in peptidoglycans of Gram-positive bacterial cell walls. The absorbance of the cell suspension at 450 nm was monitored to evaluate their catalytic activity and the rate of absorbance decrease was proportional to its activity. (b) Compared to native lysozyme (red), disulfide-modified lysozyme retained 86% activity (blue). The calculation details are shown in Section 8.3 of the ESI.† (c) Statistical modified lysozyme based on NHS ester chemistry resulted in total loss of the catalytic activity. The calculation details were shown in ESI.†.