Online interactive fitting and simulation of protein circular dichroism spectra for use in education and for preliminary spectral analysis

Abstract

Far-UV circular dichroism (CD) spectroscopy provides a rapid, sensitive, nondestructive tool to analyze protein conformation by monitoring secondary structure composition. Originally intended for educational purposes, a spreadsheet-based program that implements a rudimentary routine for fitting and simulating far-UV protein CD spectra became quite used in research papers too, as it allowed very quick deconvolution of spectra into secondary structure compositions and easy simulation of spectra expected for defined secondary structure contents. To make such software more readily available, I present here an online version that runs directly on web browsers allowing even faster analyses on any modern device and without the need of any spreadsheet or third programs. The new version further extends the original capabilities to fit and simulate alpha, beta and random coil contents now including also beta turns; it allows to quickly select the effective spectral window used for fitting and enables interactive exploration of the effects of changes in secondary structure composition on the resulting spectra. The web app allows ubiquitous implementation in biophysics courses for example right on student smartphones, and seamless, rapid tests in research settings before moving to more advanced analysis programs (a few proposed here too). The web app is freely available without registration at http://lucianoabriata.altervista.org/jsinscience/cd/cd3.html