The samples which did not show a large divergence in R-value when compared to 100 nm AuNP-MUA-Cyt c Electro are presented in Figure 4B with the ligand termination conjugated to Lys 79 following Jain et al., 2021 . The Lys residues are a likely point for conjugation as they are positively charged, so would naturally have electrostatic interaction with the carboxyl group, while also containing amino groups which are required for covalent conjugation using EDC/NHS . Lys 25 and 27 are also highlighted as they too are potential conjugation sites and may be the label the heme ring and amino acid residues. In the structure of Cyt c, the heme/porphyrin ring was red, the Iron (Fe) at the centre of the heme\porphyrin ring was yellow, Cys was black, Glu was magenta, Leu was blue, and Lys was green.