Utilization of a precolumn with size exclusion and reversed-phase modes for size-exclusion chromatographic analysis of polysorbate-containing protein aggregates.

Size-exclusion chromatography (SEC) is a useful method for quantification of protein aggregates because of its high throughput capacity and highly quantitative performance. One of the problems in this method concerns polysorbates, which are well-known additives for protein-containing products to prevent protein aggregation, but frequently interfere with the photometric detection of protein aggregates. We developed a new SEC method that can separate polysorbates from protein sample solutions in an on-line mode with a precolumn with size exclusion and reversed-phase mixed modes. The precolumn can effectively trap polysorbates in aqueous mobile phase, and the trapped polysorbates are easily eluted with acetonitrile-containing aqueous mobile phase to clean the precolumn. Small parts of protein aggregates may be also trapped on the precolumn depending on temperature and proteins. Setting appropriate column temperature can minimize such inconvenient trapping of aggregates.

A triruthenium carbonyl cluster bearing a bridging acenaphthylene ligand: an efficient catalyst for reduction of esters, carboxylic acids, and amides by trialkylsilanes.

An efficient reduction of carboxylic acids, esters, and amides with trialkylsilanes is accomplished using a triruthenium carbonyl cluster bearing a bridging acenaphthylene ligand, (mu(3),eta(2):eta(3):eta(5)-acenaphthylene)Ru(3)(CO)(7), as the catalyst. Preactivation of the catalyst by hydrosilanes accelerates the reactions. Sterically small trialkylsilanes are effective in these reactions. Reduction of carboxylic acids and amides efficiently produces the corresponding silyl ethers and amines, respectively. Reduction of esters gives a mixture of silyl and alkyl ethers, but can be controlled by changing the silanes and solvents.