Simulation of FT-IR spectra and 2D-COS analysis for the thermal perturbation of apo-centrin

Simulated FT-IR spectra were generated for two-dimensional correlation analysis of a calcium-binding protein known as centrin in its apo-state during thermal perturbation to resolve correlation between side chains and backbone vibrational modes. We have added a simulation of the two-dimensional correlation to verify the correlations between side-chain modes and the vibrational modes associated with secondary structure. The simulation of the 2D-COS synchronous and asynchronous contour plots was achieved by simulating the underlying spectral components of the one-dimensional spectra. Specifically, the amide I′ and II bands in the spectral region of 1720–1500 cm−1 using the auto-peaks obtained from the experimental two-dimensional correlation analysis by curve-fitting routines. The curve-fitting analysis used both the number bands and band positions determined from the auto-peaks of the experimental 2D-COS. These curve-fitting routines use the number of bands, position, line shapeheight and bandwidth as parameters to fit the experimental data. Thus, allowing for the simulation of the exponential intensity decrease within the amide I′ band often observed in proteins as well as band shifts and bandwidth changes observed in the amide I′ and II bands. As a result, the simulations of the synchronous and asynchronous plots were achieved with matching phase information provided in the experimental contour plots. More importantly, the results presented prove the methods’ efficacy and viability for simulations of FT-IR spectra and 2D-COS for proteins.