Affinity Capture-Mass Spectrometry

AC-MS

SKi has pioneered the use of nanoporous silicon for affinity capture-mass spectrometry applications, combining the sensitivity of lable-free binding and the information richness inherent in mass spectrometry detection. Much like MS redefined liquid chromatography capability when incorporated as a detector, AC-MS redefines label free binding by e.g. :

AC-MS sketch

Figure 1 Sketch of fully on-line setup using SKi Pro and a generic MS. SKi Pro is shown with the SKi Bridge module and connected to any LC-MS system. Time synchronization is affected using SKi Pro as a contact closure master or slave.

Fully on-line affinity capture

In the past, biotech researchers wishing to perform affinity capture with MS would rely on off-line techniques. One might use some affinity capture matrix, affect elution and then carry the sample to the mass spec. With SKi Pro this is not necessary. This not only removes process complexities, it allows for an orthogonal means of evaluating the binding.

With SKi Pro, one always has the label free signal. The small molecules one analyzes using SKi Pro in refractive index mode gives a signal, albeit often a weak one. This signal may be used as a positive control, absent the MS, to verify that the protein ligand is not only bound, but performing well. For instance, one may, off line, immobilize a kinase and verify it is bound and binding using a staurosporin positive control. Then, the system can be used in concert with the MS to perform small molecule screening experiment, knowing with confidence the enzyme and conditions are well behaved.

SKi Bridge Interface

To combine the high pressure aqueous, salt containing world of label-free binding and the ultra-high pressure, organic, no-salt world of mass spectrometry, SKi has developed SKi Bridge. (full specifications)

SKi Bridge is effectively a fraction collector and timing synchronization tool when arranged as shown in figure 1. As can be seen in figure 2, the two, 2-port, 10-position valved are arranged so that both the sample and reference channel are collected at identical times, giving an on-line chemically tunable reference. The sample and reference channel may then be eluted separately into the MS, allowing the user to be confident that any particular signal is in fact a specific one.

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AC-MS sketch

Figure 2 Sketch of the SKi Bridge plumbing interface.