In Protein Chemistry we use the latest technologies within protein purification and characterization. We strive to adapt the methods and the analytical tools to answer crucial questions in relation to the enzyme, substrates and products basic characteristics and in relation to their use in various applications.
Protein purification is carried out in the traditional way by using the various existing principles such as ion-exchange, hydrophobic interaction and size exclusion chromatography. However, often we develop our own methods based on specific adsorption e.g. via immobilized inhibitors. This enables us to obtain fast and efficient purification methods suitable for automation as is the case for e.g. proteases where high numbers of protease variants can be purified each week. We can run chromatographic purification in a scale from g to kg quantities. Highly purified proteins are a necessity to their functional study both on the basic characteristics and in the targeted application.
Protein structural characterization
The principles of automated Edman degradation together with mass spectrometry facilitated protein sequencing in a QTOF-instrument is used to characterize the primary structure. Also, we employ LC-ESI-MS and MALDI-MS as tools together with traditional HPLC mapping and in gel digestion of proteins. Furthermore, amino acid and carbohydrate composition analysis is carried out routinely. The structural information is used both for designing suitable primers for the subsequent cloning of novel proteins and in order to verify post-translational modifications. Also, we follow the latest trends within functional proteomics to obtain the combined information of enzyme activity analysis and structural characterization in order to identify completely new proteins.
Protein functional characterization
In order to study the catalysis of individual enzymes we employ a number of assays developed on our own for measuring kinetic constants as well as studying the binding of substrate/inhibitors. Basic characterization like temperature and pH-activity are carried out routinely with the targeted application in mind. Fast reactions are measured using stopped flow kinetics combined with fluorometry/UV-VIS. Also, ligand binding is studied e.g. by investigating thermodynamic parameters in isothermal titration calorimetry (ITC).
Together with structural determination of the often complex substrates and products using HPLC, NMR or other analytical tools this helps us in gaining crucial information regarding preferred substrates, specificities, binding constants and kinetic constants; knowledge we have used in developing e.g. lipases with new specificities. Furthermore, we learn about the effects of ligands like calcium in stabilizing the folded conformation of a protein (e.g. in amylases where we based upon calcium stabilization have developed new improved amylases for the starch industry). Also, the thermal stability and the susceptibility towards surfactants of the proteins are investigated using techniques like differential scanning calorimetry (DSC), circular dichroism spectroscopy (CD) or fluorescence unfolding, enabling us to identify stabilized enzymes for e.g. laundry detergents as well as for the development of ideal formulations for the storage of enzyme products.
We have our own organic synthesis laboratory, which provide support in the development of screening assays and elucidating the catalytical mechanism of a given enzyme by providing suitable new substrates/inhibitors. The analytical tools employed in organic synthesis can be helpful in developing an understanding of the enzymatic mechanism in the actual application. Also, organic chemistry is used in development of new immobilizing techniques and for the chemical modification of proteins e.g. decreasing the allergenicity of a given protein by derivatizing the protein surface.