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Amyloids and Heparin

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Amyloid proteins form fibers as they systematically stack in the presence of heparin. Examples of amyloids are the beta-amyloid and tau of Alzheimer’s disease, prions, and perhaps even sickle cell anemia fibers. Amyloids are proteins that stack into fibers and can be detected microscopically by binding particular stains, e.g. Congo Red. All of the amyloid proteins are also heparin binding, e.g. Alzheimer’s amyloid is 50% heparin sulfate. I surmise that the Congo Red is binding to the heparin-binding domains, because Congo Red also binds to cellulose and a particular lipopolysaccharide from Shigella flexneri. Antibodies and enzymes that bind to polysaccharides, bind through tryptophan residues that are flat, hydrophobic plates with regular spacing. The amyloid fibers presumably bind the broadly spaced hydrophobic surfaces of Congo Red by providing corresponding complementary hydrophobic regions of the basic amino acids that are grouped on the stacked amyloids. The interactions bet...

Antimicrobial Heparin binding Domains

Antimicrobial Digestion Stomach enzymes produce antimicrobial peptides and intestinal enzymes inactivate heparin-binding domains of pathogens The human digestive systems exhibits some amazing adaptations -- it can excise heparin-binding domains from ingested proteins and use them as antimicrobial peptides to inactivate ingested bacteria. Then in subsequent enzymatic steps in the intestines, the heparin-binding domains that otherwise could be used to adhere bacteria to the heparan sulfate proteoglycans of the intestinal lining, are chopped into inactive peptide fragments. I was trying to find a cheap heparin-binding protein to use for a variety of research projects and finally found it in the form of whey lactoferrin. This protein is available in a relatively pure form for about $1 per milligram. Alternatively, I could buy it as a nutriceutical in 250 mg capsules for $0.50 per capsule or 1/500th the cost. My next step was to purify the cheap lactoferrin by binding it to chromatograp...