Question

when fluorescent markers are attached to two ends of a holiday junction, the FRET signal is observed to jump between a high efficiency and low efficiency state because of the changes in the

choices

excitation intensity

excitation frequency

donor acceptor distance

twists in dna

Answer 1

SOL:

Fluorescent markers, or known as flourophore. Attached two end of holiday junction by FRET signal or FRET mesurement is one of the most powerful mobile holiday juction. The fundamental mechanism of FRET involves a donor fluorophore in an excited electronic state, which may transfer its excitation energy to a nearby acceptor fluorophore.The theory supporting energy transfer is based on the concept of treating an excited fluorophore as an oscillating dipole that can undergo an energy exchange with a second dipole having a similar resonance frequency. Resonance energy transfer is not sensitive to the surrounding solvent shell of a fluorophore. The major solvent impact on fluorophores involved in resonance energy transfer is the effect on spectral properties of the donor and acceptor.The phenomenon of FRET is not mediated by photon emission, and furthermore, does not even require the acceptor chromophore to be fluorescent. In most applications, however, both donor and acceptor are fluorescent, and the occurrence of energy transfer manifests itself through quenching of donor fluorescence and a reduction of the fluorescence lifetime, accompanied also by an increase in acceptor fluorescence emission,

FRET efficiency (E) varies as the inverse sixth power of the distance between the two molecules (denoted by r):

EFRET = 1/[1 + (r/R0)6]. R(0) is the characteristic distance,distance between the two molecules (r)

So, by above theory we can say that he FRET signal is observed to jump between a high efficiency and low efficiency state because of the changes in the donar and accepter distance.

note:- BY searching different papers i conclude this answer but still you have doubt you can go for further study.

Thank you.