Single-particle approaches in the analysis of small 2D crystals of the mitochondrial channel VDAC

It has been difficult to obtain better than moderate resolution in analysis of electron microscopic images of small, 2D crystals with variable lattice parameters, e.g., crystals of the channel VDAC generated by phospholipase treatment of outer mitochondrial membranes. We demonstrate that applying si ngle-particle analysis methods to correlation-averaged images can lead to s ignificant improvements in the attainable resolution. Application of a soft -edged fitted mask passing only the central unit cell, and excluding the po sitionally variable adjacent unit cells, allows improved alignment and more sensitive multivariate statistical analysis, needed to guide intelligent m erging of data from different crystals. (C) 2001 Academic Press.