Protein Purification Methods
It is through protein purification methods that we have been able to study and understand proteins in detail. These methods, or derivatives of the methods, are used in the clinical labs to identify abnormal samples. Protein purification methods use fraction techniques which are in a large part based on:
solubility;
size;
charge;
binding specificity.
These properties of a protein are derived from the AA properties composing the protein. For example the molecular weight (MW) of a protein is just the summation of the masses of the individual AAs composing the protein. MW is usually expressed in daltons (Da) or kilodaltons (kDa). A Da is the same as an atomic mass unit which is approximately the mass of a nucleon and is equivalent to 1 g/mol.
To begin any sort of purification it is important that an assay be available to identify where the protein of interest is after the fractionation. Assays come in many different forms and depends in a large part on the type of protein you are trying to purify (i.e. is it an enzyme?). Commonly used assay technologies are:
spectroscopic (using Bradford reagent or a chromagenic substrate)
immunological (using a antibody that can recognize the protein of interest)
These will be discussed in more detail later.