Structural Diversity Problems and the Solving Method for Antibody Light Chains

The structural diversity (heterogeneity) problem of antibodies has become a big subject along with the development of antibody drugs and catalytic antibodies. The detailed studies on the subject have not been conducted because many difficult and complex problems are existed in the phenomena. The heterogeneity problem is observed in a whole antibody as well as a catalytic antibody. The difficulty and complexity of the heterogeneity are in the generation of many isoforms caused by different charges, different molecular sizes, and/or modifications of amino acid residues. We found that the constant region domain of the antibody light chain also plays an important role in the heterogeneity. It is desirable that the antibody and/or the subunits must have a defined structure for practical use. We found interesting phenomena that copper ion can convert the multi-molecular forms of antibodies to mono-molecular forms. The ion contributed greatly to the enrichment of the dimer-form and the homogenation of the differently charged full-length and constant region domain of the light chain. The role of copper ion must be significant for preparing a single, defined, not multiple, isoform structure. Note that the big problem could be solved by using copper ion during the purification process

Cononsolvency of poly(carboxybetaine methacrylate) in water–ethanol mixed solvents

Cononsolvency refers to the phenomenon in which a polymer collapses in mixtures of good solvents with specific compositions. The coil-to-globule-to-coil transitions of a zwitterionic polymer, poly(2-[(N-2-methacryloyloxyethyl-N,N-dimethyl)ammonio]acetate) (PCB2), in water, ethanol, and water–ethanol mixed solvents were investigated and compared with those of poly[2-(methacryloyloxy)ethyl phosphorylcholine] (PMPC). PCB2 showed cononsolvency in water–ethanol mixed solvents with specific ethanol volume fractions. The reentrant square well-type sharp coil–globule transition was reproduced by a statistical mechanical model involving competitive hydrogen bonding and cooperative hydration. PCB2 showed a broader cononsolvency range than PMPC because of its lower association constants of water and ethanol and the marked competition for hydrogen bonding. The zwitterion-specific cononsolvency characteristics were rationalized with the electrostatic potentials and van der Waals energies of the zwitterions