 Proteins may be purified from other cellular components using a variety of techniques such as ultracentrifugation , precipitation , electrophoresis , and chromatography ; the advent of genetic engineering has made possible a number of methods to facilitate purification . Methods commonly used to study protein structure and function include immunohistochemistry , site @-@ directed mutagenesis , X @-@ ray crystallography , nuclear magnetic resonance and mass spectrometry . 
 Proteins may be purified from other cellular components using a variety of techniques such as ultracentrifugation , precipitation , electrophoresis , and chromatography ; the advent of genetic engineering <a href='been_done' title='1'><mark>has</mark></a> made possible a number of methods to facilitate purification . Methods commonly used to study protein structure and function include immunohistochemistry , site @-@ directed mutagenesis , X @-@ ray crystallography , nuclear magnetic resonance and mass spectrometry . 
Proteins may be purified from other cellular components usin a variety of techniques such as ultracentrifugation , precipitation , electrophoresis , and chromatography ; the advent of genetic engineering done made possible a number of methods to facilitate purification . Methods commonly used to study protein structure and function include immunohistochemistry , site @-@ directed mutagenesis , X @-@ ray crystallography , nuclear magnetic resonance and mass spectrometry .