Resonance Energy Transfer

Resonance energy transfer is also a nonradiative pathway, but it requires a stringent set of conditions, unlike the nonfluorescent deactivation pathways mentioned above. In resonance energy transfer, the excited dye is a FRET donor (D) which becomes deactivated via transfer of some of its excited-state energy to a compatible acceptor (A) molecule (Fig. 1B). Because it does not involve the emission of photons from the donor, FRET is more correctly referred to as ''Forster resonance energy transfer,'' or simply RET.[2] Efficient energy transfer from excited D to A requires that 1) the fluorescence emission spectrum of D and the absorption spectrum of A be overlapping (resonant frequencies as shown in Fig. 2A); 2) the distance between D and A be within 10 to 100 A (1-10 nm); 3) the dipole moments of D and A be approximately parallel to one another. If A is also a fluorescent molecule, FRET results in an increase in fluorescence emission from A (Fig. 1B, indicated by the wavy arrow depopulating A*) in addition to the decrease in fluorescence emission from D. If A is a nonfluorescent molecule, the net result of FRET is a decrease in fluorescence emission from D. In this case, A is a fluorescence quencher and A* becomes exclusively depopulated by nonfluorescent pathways (Fig. 1B, dashed arrow).

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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