Cation exchange frontal chromatography for the removal of monoclonal antibody aggregates.

A low ligand density cation exchange (CEX) chromatography resin, Eshmuno® CP-FT resin, was investigated for the removal of aggregates from monoclonal antibody (mAb) feeds using a continuous loading process. Removing mAb aggregates with a CEX resin using continuous loading is advantageous relative to a bind/elute loading process, because the resin can use nearly its full capacity to bind the aggregates enabling much higher loadings. The removal of mAb aggregates with Eshmuno® CP-FT resin using a continuous loading process was found to be consistent with a frontal chromatography mechanism where the mAb monomer initially binds to the column and is subsequently displaced by dimers and higher molecular weight aggregates. The removal of mAb aggregates with Eshmuno® CP-FT resin using a continuous loading process was compared with six other commercially available strong CEX chromatography resins and found to correlate with their ionic densities, but not their mAb static binding capacities. The influence of pH, conductivity, residence time, and mAb concentration on the removal of aggregates with Eshmuno® CP-FT resin using a continuous loading process was also investigated. Finally, the percentage of aggregates in a mAb feed was varied to examine the effect on the removal of aggregates with Eshmuno® CP-FT resin using a continuous loading process.

Separating proteins with activated carbon.

Activated carbon is applied to separate proteins based on differences in their size and effective charge. Three guidelines are suggested for the efficient separation of proteins with activated carbon. (1) Activated carbon can be used to efficiently remove smaller proteinaceous impurities from larger proteins. (2) Smaller proteinaceous impurities are most efficiently removed at a solution pH close to the impurity's isoelectric point, where they have a minimal effective charge. (3) The most efficient recovery of a small protein from activated carbon occurs at a solution pH further away from the protein's isoelectric point, where it is strongly charged. Studies measuring the binding capacities of individual polymers and proteins were used to develop these three guidelines, and they were then applied to the separation of several different protein mixtures. The ability of activated carbon to separate proteins was demonstrated to be broadly applicable with three different types of activated carbon by both static treatment and by flowing through a packed column of activated carbon.

An improved Larock synthesis of quinolines via a Heck reaction of 2-bromoanilines and allylic alcohols.

A modified Larock method has been developed for the one-pot synthesis of substituted quinolines via a Heck reaction of 2-bromoanilines and allylic alcohols followed by dehydrogenation with diisopropyl azodicarboxylate (DIAD).

Three-step synthesis of end-substituted pentacenes.

A concise, three-step synthesis of 1,4,8,11-substituted 2,3,9,10-tetrakis(methoxycarbonyl)pentacenes from commercially available 1,2,4,5-tetrakis(bromomethyl)benzene was established. Efficient alkynylation, followed by formation of four fused rings via a zirconacyclopentadiene intermediate, and then oxidation with DDQ gave pentacenes 1a-c. The process was compatible with methyl, phenyl, and trimethylsilyl substituents, which have good solubility in various organic solvents.

A cyclodextrin-insulated anthracene rotaxane with enhanced fluorescence and photostability.

A beta-cyclodextrin anthracene rotaxane was synthesized and found to be significantly more resistant to fluorescence quenching and photobleaching than the uninsulated anthracene derivative.

The chain-length dependence test.

Trends obtained from systematic studies based on chain-length variation have provided valuable insight and understanding into the behavior of m-phenylene ethynylene foldamers. The generalization of this experimental approach, the chain-length dependence test, is useful for studying solution conformation, packing in the solid state, specific intrachain interactions, and the contributions of end groups to a particular property.

Supramolecular chelation based on folding.

Crystallographic analysis revealed that pyridine-palladium complexation is a good geometric match to the m-phenylene ethynylene (mPE) repeat unit and thus could serve as a reversible linking group to join oligomer segments together. A series of pyridine-terminated mPE oligomers were then synthesized and found to coordinate with palladium dichloride to give complexes effectively twice the length of the free oligomers. A quantitative analysis of these coordination equilibria by isothermal calorimetry found the ability of the pyridine end-group to form a coordination complex corresponded with their ability to fold. Oligomers that were able to form complexes of sufficient length to fold showed positive cooperativity based on experimental determination of their association constants with a palladium ion. We suggest that the additional free energy of complexation for the folded oligomers is analogous to chelation by multidentate ligands, but here the "multidentate ligand" is held together by supramolecular rather than covalent bonds.

A helicene-containing foldamer displaying highly solvent-dependent CD spectra.

[structure: see text] A m-phenylene ethynylene oligomer containing a helicene unit was synthesized to bias the twist sense of the folded helical conformation. The CD spectra of the helicene oligomer exhibited large Cotton effects that varied greatly with the solvent composition, including three separate conformational transitions.

A water-soluble m-phenylene ethynylene foldamer.

[reaction: see text] A water-soluble m-phenylene ethynylene (mPE) foldamer was realized by appending hexaethylene glycol side chains to the backbone repeat unit. UV spectra of the oligomer in aqueous solutions were consistent with a helical conformation. The association constant of the oligomer with (-)-alpha-pinene increased dramatically with increasing water composition, peaking at 90% water by volume in acetonitrile. The rate of the host/guest system's approach to equilibrium was found to decrease considerably with increasing water content.

Helical pitch of m-phenylene ethynylene foldamers by double spin labeling.

To investigate the helical conformation of oligo(m-phenylene ethynylene)s, a pair of TEMPO spin labels were appended to the backbone. The two TEMPO radicals were separated by the four, five, and six repeating units. ESR spectra of the labeled oligomers were measured in chloroform and in ethyl acetate solvents in which the oligomers are disordered and folded, respectively. The measurement and analysis of ESR spectra revealed that six repeating units make one helical turn.