Molecular Playground/Human Serum Albumin

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is the most abundant protein in the blood plasma, amounting to about 35 to 50 grams per liter of serum. It consists mostly of alpha helices that form several hydrophobic binding pockets throughout the molecule.

Being the major protein in blood, it functions to maintain the osmotic pressure and the pH of the blood. But most importantly, it functions to transport various substances through the bloodstream such as carbohydrates (e.g glucose), fatty acids (e.g. oleic acid), hormones (e.g. thyroxine, a thyroid hormone), and drugs (e.g. ibuprofen, an anti-inflammatory drug). HSA does not carry a specific cargo, although it does have preference for fat-soluble substances as it can bury the water-insoluble molecules into its hydrophobic core. Here, we can see HSA with both myristate (a fatty acid) and aspirin (a common analgesic) bound to its hydrophobic pockets.

Because HSA is very abundant in blood serum, most biomarker studies involving serum requires preliminary removal of HSA so that other non-abundant but otherwise important disease-indicating proteins can be detected. In our group, we exploit several properties of HSA in order to efficiently remove it from serum prior to biomarker analysis. These include its low isoelectric point (pI of about 4.7) due to a number of acidic residues, and its tendency to bind hydrophobic molecules through its hydrophobic pockets.

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