The ability to affect protein stabilization is improving rapidly, yet work in this area still presents numerous challenges. Weak protein interactions may impact purification negatively, especially when concentrations are raised in the course of the procedure. This may result in aggregation and conformational instability, proving irresolvable for native proteins. An obvious solution lies in the use of computer modeling to reveal stabilizing mutational alterations into the molecule. Such redesigned molecules could lend themselves more effectively to a robust and efficient purification scheme.
Peter Tessier, Ph.D., assistant professor in the department of chemical and biological engineering at Rensselaer Polytechnic Institute, and his colleagues are investigating nanoparticle-based assays to measure weak protein interactions with the aim of generating proteins more sympathetic to purification protocols.
According to Dr. Tessier, at present no method exists for characterizing these interactions by high-throughput screening of hundreds of samples. His strategy exploits the separation-dependent optical properties between proteins immobilized on gold nanoparticles to detect weak self-interactions.
The Tessier group has further refined the procedures using biotin-avidin interactions to generate protein-nanoparticle conjugates that report protein self-interactions through changes in their optical properties. His approach will allow a broad range of technologically significant phenomena, including protein crystallization and aggregation, to be quantitatively evaluated. The longer-term goal of this work is to use these insights to engineer antibodies that have both high affinity and high resistance to aggregation.
“The technology is mature,” Dr. Tessier stated. “Finding high-performing antibodies is no longer a problem; so there is a broader desire to consider the biophysical properties of the formulation process. You can either deliver re-engineering proteins that you have already isolated, or you can be smarter about your choice of those proteins that you select early on.”
Tessier noted that companies such as Amgen are doing comprehensive studies early on from their candidate pool. For instance they can screen promising antibodies by evaluating their behavior on a protein A column, retaining those that bind effectively without undergoing irreversible changes. “Today there is no question about re-engineering. With that accomplished, the future lies in purification and related issues.”
The improvements in rapid screening, computer modeling, and protein purification protocols are bringing important advances to the industry. Combined with upstream advances, they are moving biologics down a path toward greater convenience and significant cost savings.