Low energy signals

PKA (A kinase) cAMP-dependent protein kinase cAMP Energy signaling (low energy signal)... 

Isocitrate dehydrogenase catalyzes the irreversible oxidative decar boxylation of isocitrate, yielding the first of three NADH molecules produced by the cycle, and the first release of C02 (see Figure 9.5). This is one of the rate-limiting steps of the TCA cycle. The enzyme is allosterically activated by ADP (a low-energy signal) and Ca, and is inhibited by ATP and NADH, whose levels are elevated when the cell has abundant energy stores. 

The hybrid has other advantages of sensitivity, low signal-to-noise ratio, fast switching between MS and MS/MS modes, use with continuous or pulsed ion sources, and use with high- or low-energy collision-induced ion decomposition. 

The methods for detection and quantitation of radiolabeled tracers are deterrnined by the type of emission, ie, y-, or x-rays, the tracer affords the energy of the emission and the efficiency of the system by which it is measured. Detection of radioactivity can be achieved in all cases using the Geiger counter. However, in the case of the radionucHdes that emit low energy betas such as H, large amounts of isotopes are required for detection and accurate quantitation of a signal. This is in most cases undesirable and impractical. Thus, more sensitive and reproducible methods of detection and quantitation have been developed. 

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