In this thesis, we demonstrate optical trapping of HSP90 proteins in plasmonic nanoapertures to study the HSP90 conformational change. This technique is label-free and non-destructive. The resonance of the bow tie shaped plasmonic nanoaperture is used to create a very strong electric field gradient force able to trap proteins. The resonance phenomenon is also used for detecting the trapping events, using the change in transmission that results from the presence of a protein in the trap. HSP90 can be trapped very stably for upwards of 30 seconds. The signal resulting from trapping HSP90 significantly differs from signals from bead traps, especially in the low-frequency regime. We observe strong evidence for a two level system when HSP90 was incubated with AMP-PNP which should slow down the conformational change (fit with R^2=0.9988). More work is required to demonstrate whether this two level system results from the conformational change. We conclude that there is a need for more advanced statistical methods to more conclusively prove that the HSP90 undergoes conformational change between two main levels and suggest further improvements to the experiments.