Dietary fibre and colonic neoplasia.

Dietary plant fibre, or plantix, is thought to play a significant role in the pathogenesis of colon cancer in humans. It is a complex polymeric substance that has several distinct components resistant to hydrolysis by the digestive enzymes of humans. These components include cellulose, hemicelluloses, pectins, lignin, gums, mucilages and, in certain instances, algal polysaccharides. These polymers have different physicochemical properties, and recent evidence from experimental studies in animals treated with carcinogens suggests that some may exert protective effects in the intestine and others may enhance colon carcinogenesis. This review synthesizes information on the chemical composition, methods of analysis and physicochemical properties of dietary plant fibre and reviews available studies examining the role of fibre in colonic neoplasia in animals and humans.     

Patterson methods in fibre diffraction analysis.

The potential of the Patterson methods for X-ray diffraction studies of textures is examined in DNA fibres. Patterson analysis, which is rarely used in these situations, is shown to yield important information on the preliminary interpretation of diffraction patterns and to increase the reliability of the three-dimensional structural pattern obtained for polymeric molecules. We also show how the screw symmetry of helical molecules can be used to calculate their electron density by means of the three-dimensional Patterson function.