A novel projection approximation algorithm for the fast and accurate computation of molecular collision cross sections (I). Method

A projected superposition approximation (PSA) to compute molecular collision cross sections measured in ion-mobility experiments is developed. In the framework of the PSA, molecular collision cross sections are computed as a projection approximation modified to account for collective size and shape effects. Illustrative calculations on a range of molecular structures demonstrate that the PSA algorithm is able to handle the complex molecular shapes (concave, convex, pores, cavities, channels) as well as the range in molecular size typical to proteins. Our results indicate strong numerical agreement with the accurate trajectory method while only a small fraction of the computational demand is required. (C) 2011 Elsevier B.V. All rights reserved.