Labeled reactant compositions, and particularly labeled nucleic acid reaction compositions, that include structural components that maintain potentially damaging labeling components sufficiently distal from the reactant portion of the molecule such that damaging effects of the label group on other reaction components, such as enzymes, are reduced, minimized andor eliminated. The switch uses multiple switch control circuits each coupled to one FCAL network and all connected to a crossbar switch. The opposite electrode comprises a clamping mechanism that clamps the front board to support it.