J 1000 series

Fluorescence spectra were recorded using a fluorescence spectrophotometer (Hitachi F-7000). UVevis absorbance was measured using a UVevis spectrophotometer (Lambda 35, PerkinElmer) to ensure the absence of large nanoparticles (NPs), which commonly show a maximum absorption peak at about 520 nm. UV light with the excitation of 365 nm was used. To study the protein conformation, far-UV circular dichroism (CD, J-1000 series, JASCO) was employed. The oxidation state of core Au atoms was examined by X-ray photoelectron spectroscopy (XPS, ULVAC-PHI, Inc.). The morphological characterisation of RNase A/AuNCs was carried out using a high-resolution transmission electron microscope (HRTEM, FEI Tecnai G2 F20 X-Twin). The Fourier transform infrared spectroscopy (FTIR) spectra of FA, rGO and FA-rGO were recorded on an FTIR spectrometer (PerkinElmer Frontier).

Far-UV CD spectra of samples were measured in 1.0 mm path length quartz cuvette from 190 nm to 240 nm wavelength using the J-1000 series JASCO (Easton, MD, USA) spectrophotometer system. The bandwidth was set at 0.5 mm, and values of three spectra were averaged to obtain a single spectrum. We obtained the spectra at 25 °C in the presence of 20 mM sodium phosphate buffer, pH 7.4. Buffer baselines were measured to normalize the CD scans of samples. For temperaturedependent far-UV CD scans, spectra were measured at every 10 °C from 30 °C to 90 °C.