MAA adducts on the surface of BSA. This figure is an application example of using PyTMs to selectively modify only solvent-accessible residues. As described, a model of Bovine Serum Albumin (BSA) was used to sub-select surface atoms before introducing Malondialdehyde-acetaldehyde (MAA) adducts. The brown surface corresponds to the original unmodified BSA. Both unmodified Lysines (43/118) and MAA-Lysines (75/118) are depicted in stick representation, but colored black or red, respectively. A) An overview of MAA-modified BSA with opaque surface. Note the surface decoration by MAA adducts (red sticks). B) An identical image with transparent surface. Note how the inaccessible/unmodified Lysines (black sticks without adduct) are likely to be shielded from modification within the protein's interior volume. Additional MAA-modified-Lysines from the protein's distal surface are also visible.