Levels of Structure in Protein
Primary: A description of all covalent bonds. The sequence of AA residues
Secondary: particularly stable arrangements of AA giving rise to recurring structural patterns.
Tertiary: All aspects of the 3D folding of a polypeptide.
Quaternary: The spatial arrangement of multisubunits protein
Protein Purification
Crude extract: breaking cells, by osmosis lysis or homogenization.
Fractionation: separate proteins into different fraction based on size of charge.
Salting out: The solubility of proteins is lowered at high salt concentration. Ammonium sulfate ((NH4)2SO4).
Dialysis is a procedure to separate proteins from solvents
Protein Purification: Column Chromatography
Ion-exchange Chromatography
-Cation exchangers contain negatively charged polymer
-Anion exchangers contain positively charged polymer.
-Is effected by pH
