There are several protein characterization tools aimed at characterizing various properties of the protein sample at the Faculty of Biochemistry and Molecular Medicine such as:
- Static light scattering (SLS): absolute molecular weight of the protein
- Dynamic light scattering (DLS): monodispersity of the protein sample
- Circular dichroism (CD) spectroscopy: secondary structure analysis and stability of the protein sample
- Surface plasmon resonance: protein-protein and protein-ligand interaction
- Isothermal titration calorimetry (ITC): protein-protein and protein-ligand interactions
- Spectrophotometer: enzyme kinetics and assays
- Multimode plate reader: biological assays
It is assumed that the protein has been well purified and is pure on an overloaded SDS-PAGE analysis. As a rule of thumb, the protein samples obtained from his-tag affinity chromatography are not pure enough. It is best to have at least one ion exchange column in the purification protocol, in order to avoid charge heterogeneity of the protein sample. The last purification step is always a size-exclusion column. The best crystallization results are obtained when using only the central part of the peak fractions. Each characterization technique has different requirements for buffer, buffer concentration and protein concentration. Consultation with the local staff is required to discuss these issues, as they depend also on the properties of the protein to be investigated. The X-ray homepage also provides an extensive set of bioinformatics links that should be consulted for characterizing the protein before starting the experimental work. Knowledge of the isoelectric point of the protein is important for setting up the ion exchange chromatography.
There is much more information available for the local users on the Protein Crystallography wiki, accessible to local users via the X-ray homepage.
Last updated: 12.9.2016