A Method for Determining the Sedimentation Behavior of Enzymes: Application to Protein Mixtures

Escherichia coli is the predominant nonpathogenic facultative flora of the human intestine. Some E. coli strains, however, have developed the ability to cause disease of the gastrointestinal, urinary, or central nervous system in even the most robust human hosts. Diarrheagenic strains of E. coli can be divided into at least six different categories with corresponding distinct pathogenic schemes. Taken together, these organisms probably represent the most common cause of pediatric diarrhea worldwide. Several distinct clinical syndromes accompany infection with diarrheagenic E. coli categories, including traveler’s diarrhea (enterotoxigenic E. coli), hemorrhagic colitis and hemolytic-uremic syndrome (enterohemorrhagic E. coli), persistent diarrhea (enteroaggregative E. coli), and watery diarrhea of infants (enteropathogenic E. coli). This review discusses the current level of understanding of the pathogenesis of the diarrheagenic E. coli strains and describes how their pathogenic schemes underlie the clinical manifestations, diagnostic approach, and epidemiologic investigation of these important pathogens.

Diarrheagenic Escherichia coli

Protein and cell membrane iodinations with a sparingly soluble chloroamide, 1,3,4,6-tetrachloro-3a,6a-diphrenylglycoluril.

Enzyme-linked immunosorbent assay (ELISA). Quantitative assay of immunoglobulin G.

Enzyme-linked immunosorbent assay, ELISA

CONVENTIONAL nonspecific precipitation methods sometimes depend on affinities which can be used in a more selective fashion by modern chromatographic techniques. The affinity of proteins for heavy metal ions, for example, may provide a basis for their purification and analysis. A highly flexible method based on such affinities is described here.

Metal chelate affinity chromatography, a new approach to protein fractionation

Biologically active proteins and polypeptides can be coupled by various means to cellulose, starch and cross-linked polysaccharide gels such as ‘Sephadex’. The use of cyanogen halides for this purpose gives a high yield of bound polypeptide or protein which retains a substantial part of its activity.

Chemical Coupling of Peptides and Proteins to Polysaccharides by Means of Cyanogen Halides

We wish to report a simple and rapid method for the fractionation of water-soluble substances. The method is based on a column procedure similar to chromatography in which the stationary phase is comprised of a new type of gel. These gels consist of hydrophilic chains which are cross-linked. They are devoid of ionic groups, the polar character being almost entirely due to the high content of hydroxyl groups. While water-insoluble, the gels are never-theless capable of considerable swelling. The fractionation depends primarily on differences in molecular size although phenomena have been observed which indicate the influence of other factors.

Gel filtration: a method for desalting and group separation.

WE have reported a method for transforming polysaccharides into reactive derivatives useful for coupling proteins to carbohydrates1 which consists in treating the polysaccharide with cyanogen halide. Imino carbonic acid esters are probably formed and these react with the primary amino groups of proteins and other substances. This method of activation and coupling is gentle and therefore particularly useful for the production of immunosorbents and insoluble enzymes.

Jerker Porath

Papers

Metal chelate affinity chromatography, a new approach to protein fractionation

Chemical Coupling of Peptides and Proteins to Polysaccharides by Means of Cyanogen Halides

Gel filtration: a method for desalting and group separation.

Chemical Coupling of Proteins to Agarose

Isolation of phosphoproteins by immobilized metal (Fe3+) affinity chromatography.