Peptide pairs which induce heterodimerization are useful components for the rational design of proteins. For this purpose, de novo peptide sequences were designed using first principles to have maximum hydrophobicity, helical propensity, and opposing charge. These peptides, (ALAR)4 and (ALAE)4, were expressed on the C-termini of monomeric fluorescent proteins mNeonGreen and mScarlet, respectively. The peptides P1 and P2, which form a coiled-coil, were also expressed on the C-termini of mNeonGreen and mScarlet, respectively. Peptides which form coiled-coils are utilized for de novo protein design because of their simple heptad repeat sequence and predictable interactivity. In this work, Forster Resonance Energy Transfer (FRET) and size exclusion chromatography are used to study the effect of these C-terminal peptides on the multimerization of larger proteins. This thesis first gives a brief background of structural biology and synthetic genomics to set the scene for de novo protein design, before telling the stories of the discovery and applications of the coiled-coil and Forster Resonance Energy Transfer. Finally, the evidence which indicates that peptide pairs (ALAR)4/(ALAE)4 and P1/P2 induce protein heterodimerization is presented and discussed.