System Advancements - Fluidics, Immobilization, Detection

This sol-gel procedure is an elaboration on well established entrapment methods [29], but with the added advantage of stability and better flow properties. Interestingly, none of the examples presented thus far demonstrate competitive behavior between multiple ligands (i.e. displacement) in the FAC analysis of trimethoprim and pyrimethamine a reversed order of elution based on is described, but this could simply be due to the shift towards an on-rate limited situation for higher affinity compounds, as described earlier. Erosion of dynamic competition between ligands could occur if the sol-gel allows convective mixing of the entrapped protein however the bimodal pore structure of these materials would 

From this discussion, there is an obvious advantage to FAC in that the assay development approach is extremely flexible and adaptable to the requirements of the interaction to be studied. It is worth mentioning that the effort placed on creating a FAC cartridge is never wasted - it can be used as a simple capture/elute tool for alternative screening approaches, and even in preclinical studies that require methods for monitoring drug candidates and their active metabolites [30]. 

Inclusion of a second pump for effluent dilution and transfer supports both online and offline MS analysis. As shown above, fraction collection followed by LC/ MS analysis sigmficantly expands the performance characteristics of the FAC method, but the effluent can also be sampled for MALDI-based analysis. Advantages to this method include greater salt tolerance over the electrospray approach, extension to complex mixtures of protein and archiving of the mn. MALDI is generally considered to possess higher peak capadty than electrospray (at least 

More recently, Brennan has shown that FAC-MALDI-MS can be used to screen small molecules, relying upon MRM transitions to overcome the chemical noise generated by the matrix [16]. This is an acceptable approach for known compounds, but for ligand discovery from uncharacterized mixtures, ion selection 

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