Enhanced electron-density envelopes by extended solvent definition

Extended delineation of water molecules, monitored using R-free values, afforded considerable improvement in quality of electron-density maps for structure determination of mammalian class I and E. coli class II aldolases. Augmented solvent definition results in an additional decrease in R-free values of 3-4% and is reflected in significantly enhanced electron-density envelopes enabling tracing of amino-acid sequences through regions of otherwise discontinuous or weak electron density.