![]() ![]() Here, we study interfacial systems of increasing complexity-from a single immobilized multimodal ligand to high density surfaces-to better understand how ligand behavior is affected by the presence of a surface and the presence of other ligands in the vicinity, and how this behavior scales to more » larger systems. ![]() Recently, we used molecular dynamics (MD) simulations to show that ligands immobilized on surfaces can interact and associate with neighboring ligands to form hydrophobic and charge patches, which may have important implications for the nature of protein–surface interactions. Multimodal chromatography uses multiple modes of interaction such as charge, hydrophobic, or hydrogen bonding to separate proteins. This new understanding of multimodal surfaces has important implications for developing improved predictive models and designing new classes of multimodal separation materials. This clustering phenomenon is likely to play a key role in governing protein–surface interactions in multimodal chromatography. Finally, we developed an approach for quantifying differences in the observed surface patterns by calculating distributions of the patch more » size and patch length. Further, the use of flexible linkers enabled hydrophobic groups to collapse to the surface, reducing their accessibility. In addition, the introduction of a flexible linker (corresponding to the commercially available ligand) enhanced cluster formation and allowed aggregation to occur at lower surface densities. On the other hand, lowering the surface density to 1 ligand/3 nm 2 reduced or eliminated this aggregation behavior. For aggregating ligands, we report this resulted in the formation of a surface pattern that contained relatively large patches of hydrophobicity and charge whose sizes exceeded the length scale of the individual ligands. We found that ligands that were flexible and terminated in a hydrophobic group had a propensity to aggregate on the surface, while less flexible ligands containing a hydrophobic group closer to the surface did not aggregate. In this work, we performed molecular dynamics simulations of a series of multimodal cation-exchange ligands immobilized on a hydrophilic self-assembled monolayer surface at the commercially relevant surface density (1 ligand/nm2). In addition, recommended screening strategies are presented where a sequential approach and Design of Experiments are used and discussed.Multimodal chromatography is a powerful tool which uses multiple modes of interaction, such as charge and hydrophobicity, to purify protein-based therapeutics. To use the full potential of Capto S, we show how to thoroughly screen the loading parameters, conductivity and pH. Capto S is a strong cation exchanger designed for capture and intermediate purification of recombinant proteins and as a second step in MAb purification. Previously launched products on this platform include Capto Q, Capto MMC and the MabSelect™ family. The medium combines high rigidity with high dynamic binding capacity (DBC) and fast mass transfer to allow faster purification, more flexible process design and maximum cost efficiency. This has recently been used in the development of a new cation exchange medium, Capto™ S, and gives a substantial increase in binding capacity compared to the corresponding media without dextran.Ĭapto S is a chromatography medium based on the novel high flow agarose platform. A technique for significantly improving the capacity and mass transfer properties of ion exchange media is modification of the porous base matrix with a surface extender such as dextran. Increasing expression levels of recombinant proteins and the need for improved productivity and overall process economy puts extra demand on the next generation of chromatography media for the bio-pharmaceutical industry. ![]()
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