The unique size and material dependent properties of nanoparticles have made them highly attractive for biological and medical applications. However, combining nanoparticles with biomolecules and biological environments has faced many challenges. These interface issues often involve protein denaturation, steric hindrance, and orientational issues for the biomolecule, which can impair function and decrease overall performance of the nanoparticle-biomolecule conjugate. Historically, our understanding of the physical and chemical properties of nanoparticle-biomolecule conjugates as appropriate tools and experimental techniques had to be determined. We discuss here selected examples investigating the fundamental physical properties of the interface between nanoparticles and DNA and proteins and protein coronas and how they have provided insight into the properties of the biomolecule when it is interfaced to a nanoparticle.