NP-enzyme interactions were studied by monitoring the secondary structure content using circular dichroism (CD) measurements. All CD measurements were performed on Applied Photophysics Ltd Chirascan™ using a Hellma Quarts Suprasil® cuvette with 1 mm path length at 25°C. All spectra were recorded at 190-280 nm, using a 1 nm wavelength increments with a 0.4 s dwell time and a bandwidth of 1 nm. For each sample, 3 individual spectra were recorded, corrected for background contributions by subtracting appropriate blanks, and averaged.