Protein binding assay is used to test the protein binding extent. In other words, it’s to measure the binding level of a protein. Before finding out what protein binding assay is, the definition of protein binding should be clearly understood.
Generally, protein binding determines a drug’s efficacy in human bodies. It can both strengthen and weaken the effect of drugs, but in different ways. Protein binding, as it means literally, refers to protein making bond with other substances, which in the pharmacological context is the bond that drugs make to the molecules in blood, like red blood cells and membrane.
Protein binding level can be used to describe the drug efficiency. The drugs bound with other molecules won’t perform its medical properties, whilst the unbound drug will take the responsibility and carry out the tasks it shoulder. If 90% percent of a drug bond to other substance and become bound drugs, the rest 10% unbound drug will keep in the blood stream and take medical effect. That’s how protein binding determines drug efficacy. The bound drugs still can take effect but the ability will be detracted. The more bonds they make, the lower medical property level will be performed. Fewer bonds directly lead to smaller size, meaning better ability of passing through tissues.
How does the binding be made? That’s a kind of complicated question to answer. Proteins combine with other molecules including proteins at binding sites, a protein may contain several such sites, which are always in the form of indentations. The binding will be made when a molecule fit into the indentation. Thus more indentations a protein has, the bigger the protein will be after being bound. Protein binding will change with its surrounding alteration, like stress and pregnancy.
However, the indentation is not available for a fixed type of molecule; it can be filled by any molecules that fit to it chemically, which pose danger to bodies. If two drugs are taken by a patient at the same time, and both of them bond to a same type of molecule, but one is with stronger ability to combine with the targeted molecule, thus the other drug will remain more unbound and effective protein in the blood and take effect. In this way overdose situation may appear.
Protein binding assay is designed to identify the tendency of a protein to combine with other molecules. In the assay, plasma or tissue will be employed. With these substances, protein will be incubated for a certain period, and then they will pass through a very accurate filter. The unbound proteins can successfully pass the filter, however the bound ones can’t for that they are enlarged by the binding with other molecules.
Drug that are newly developed will be tested with protein binding assay to roughly determine the amount of free drug will be existed in blood stream and take effects, which is a must-have process before a newly invented drug can be put into market.