Evidence of Conformational Changes in Adsorbed Lysozyme Molecule on Silver Colloids Abstract Goutam Chandra $^{1}$, Kalyan S. Ghosh$^{2}$, Swagata Dasgupta2 and Anushree Roy 1 $^{1}$Department of Physics, Indian Institute of Technology, Kharagpur 721302, India $^{2}$Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India In this article, we discuss metal-protein interactions in the Ag-lysozyme complex by spectro- scopic measurements. The analysis of the variation in relative intensities of SERS bands reveal the orientation and the change in conformation of the protein molecules on the Ag surface with time. The interaction kinetics of metal-protein complexes has been analyzed over a period of three hours via both Raman and absorption measurements. Our analysis indicates that the Ag nanoparticles most likely interact with Trp-123 which is in close proximity to Phe-34 of the lysozyme molecule. Keywords : Lysozyme, Ag colloids, SERS, optical absorption 1 arXiv:1001.0284v2 [physics.bio-ph] 6 Jan 2010