Proteins
•Complex, polymeric, asymmetric and sensitive molecules
•Contain covalent bound prosthetic groups and non-covalent bound cofactors
•Many non-covalent bounds e.g. Hydrogen-Bounds, Dipol-Interactions and Hydrophobic-Interactions
•“Weak” interactions are important for structure and function (activity) of the protein
􀃆In most cases the purification must be gentle!

Before the purification…
•Cultivation of bacteria
•Cell disruption: Periplasmic and cytoplasmic proteins are released
•Centrifugation leads to a soluble fraction(supernatant) which contains all soluble periplasmic and cytoplasmic proteins and a membrane fraction from which membrane bound proteins can be solubilised with detergents (e.g. Triton X-100)
•The soluble or membrane fraction are the start point of the further purification by chromatography
Cell disruption:􀃆French Press
􀃆                         Lysozyme
􀃆                         Ultrasonic

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