Software for handling macromolecular envelopes

Macromolecular phase-refinement and phase-extension calculations using real-space electron-density averaging techniques require accurate envelopes (or masks) to define the boundaries of each domain or molecule whose density is to be averaged. An extensive set of tools, implemented in four computer programs (O, MAMA, COMA and MASKIT) are described which can be used to generate such envelopes (either from an atomic model or based on local density-correlation maps), to improve them, to remove overlap owing to crystallographic or non-crystallographic symmetry, to display them and to manipulate them in a variety of manners.

Ultrastructure of Intranuclear Round Bodies of Enta-Moeba Histolytica After Dnasa and Rnasa Treatment

Recent morphological studies of E. histolytica have revealed the presence of several intranuclear structures which are clearly distinguished from other nuclear components. These are round membrane bound bodies of variable marked electron density averaging from 15 to 40 milimicra in diameter (Fig. 1). Their intranuclear location and persistance within the nucleus along the various stages of the life cycle of E. histolytica seems to indicate that these structures may have a functional role in the nucleus. The present study was undertaken to determine the existence of DNA and RNA in this intranuclear structures.Trophozoites of E. histolytica ABRM strains obtained from monoxenic cultures were fixed for 35 minutes in 2.5% Glutaraldehyde, 0.1M sodium cacodilate buffer.