Protein Expression and Purification Services
Signalling Factory
In the most cases, the workflow from the decision about protein purification to pure protein could be divided into five main steps:
I. Choice of the Expression System
II. Subcloning into suitable Expression Vector
III. Expression Optimization
IV. Protein Expression at the desired Scale
V. Protein Extraction & Purification
However not all groups can perform all these steps by themselves either due to lacking of skills or proper equipment. Our facility provides a diverse expertise and infrastructure for a small and large scale of protein expression and purification, which make it possible to help you at the certain step as well as undertake a task for the whole process.
Currently we offer two main expression systems for protein production: bacterial and mammalian cells. Using these two systems we can cover many classes of proteins, including antibodies, enzymes, grows and transcription factors, chemokines, phytochromes and many others.
If you are interested in using our protein expression and purification service, fill out the 
Protein Service Request Form and send it per mail to toolbox@bioss.uni-freiburg.de
Bacterial Expression System
For unknown proteins, we typically screen different strains of E. coli with our optimized vectors. Variable (auto)induction methods and purification schemes could be used to acquire desired protein amount. We have expressed and purified hundreds of cytoplasmic and periplasmic proteins in E. coli. This allows us quite often skip the optimization of protein expression and directly go for larger scale expression.
Using E. coli system, we can produce proteins at microgram to gram level. In the last case we usually culture cells at very high density (OD600 > 120) in feed batch mode in our 10 L BioFlo 415 Fermenter with final yield of bacterial pellet about 1.2 kg
Mammalian Expression System
Mammalian cell cultures are the system of choice for the expression of secreted and transmembrane proteins or if mammalian-specific post-translation modifications are required. We conduct protein expression in mammalian cell lines via plasmid transient transfection, stable cell line establishment, retrovirus or lentivirus transduction. We are able to use our fluorescent proteins and other expression tags for monitoring expression, or provide different drug-resistant genes if established cell lines are used for long term expression projects.
We have established the method for large scale transient transfection, which allows us production of some proteins at the level of several hundred milligrams per liter of suspension cells. Two autoclavable benchtop cell culture bioreactors could be used for scaling up the expression system. The CelliGen 310 (2.5 L and 14 L) can be operated in batch, fed-batch and perfusion mode independently of each other or connected in seri