What is Protein Purification

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By JeffreyThurber

Protein purification entails a sequence of processes meant to separate one or a few proteins from an intricate mixture, usually tissues, cells, or whole organisms. Protein purification is integral for characterizing the structure, function, and interactions of the protein in focus. The purification procedure may separate the non-protein and protein parts of the mixture and finally isolate the Fleet Bioprocessing desired protein parts from the rest of the undesired proteins. Isolating one protein from the rest is usually the most difficult aspect of the protein purification process. Separation stages typically exploit differences in physico-chemical properties, protein size, biological activity, and binding affinity. The final pure product is what is referred to as a protein isolate.

Its Purpose

The protein purification process can either be analytical or preparative. Preparative purifications produce relatively large quantities of purified proteins for consequential usage elsewhere. Some examples include preparing commercial products such as certain biopharmaceuticals (e.g., insulin), nutritional proteins (e.g., soy protein isolate), and enzymes (e.g., lactase). There are many preparative purifications stages employed to eliminate bi-products like host cell proteins that may pose a threat to the health of a patient. 1] On the other hand, analytical purification generates small amounts of protein suited for various analytical or research purposes, including recognition, quantification, and studies of the protein’s composition, post-translational changes, and function. Urease and pepsin were the first proteins to get purified, and the final product crystallized.

Purification strategies

Choosing the starting component is integral to the design of a protein purification process. In an animal or plant, a particular protein isn’t usually distributed homogenously; different tissues or organs have lower or higher protein concentration levels. Using the organs or tissues with high concentration levels reduces the volumes required to generate a specified amount of purified protein. If the protein is available in low quantities or it has an elevated value, scientists may opt to use recombinant DNA technology to create cells that will generate large amounts of the desired protein (this is what is referred to as an expression system). In recombinant expression, the protein will be tagged, e.g., by a Strep-tag or His-tag to enable purification, decreasing the number of purification stages needed.

An analytical protein purification uses three properties to isolate proteins. First, proteins can get purified depending on their isoelectric points by passing them through an ion exchange column or pH graded gel. Second, proteins can be isolated according to their molecular weight or size through sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis (SDS-PAGE) or size exclusion chromatography.

Proteins are usually purified utilising 2D-PAGE and are then examined by peptide mass fingerprinting to determine the protein identity. This is very beneficial for scientific reasons, and the detection limits for proteins these days are low, and only nanogram quantities of protein are enough for their analysis. Thirdly, proteins can be isolated by hydrophobicity/polarity through reversed-phase chromatography or high-performance liquid chromatography.

Protein purification usually involves one or more chromatographic stages. The chromatography procedure basically entails flowing the solution with the protein through a column packed with different materials. The column material interacts differently with various proteins and can hence the desired protein can be isolated by the time the solution passes the column or the conditions needed to remove the protein from the column. Proteins are usually identified as they come out of the column by their absorbance at 280nm.

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