Fluorescence and Quenching

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Questions and Answers

What is the process known as the emission of light from any substance?

Phosphorescence

Luminescence (correct)

Stokes shift

Fluorescence

What is typically observed at lower energies or longer wavelengths in fluorescence?

Internal conversion

Excited-state reactions

Stokes shift (correct)

Energy transfer

What principle states that the same fluorescence spectrum is generally observed irrespective of the excitation wavelength?

Solvent effects

Kasha’s Rule (correct)

Complex formation

The Franck-Condon Principle

What is plotted as fluorescence intensity versus wavelength or wavenumber?

Fluorescence emission spectrum Signup and view all the answers

What occurs when the nuclei does not have time to adjust after an energetic transition?

The Franck-Condon Principle Signup and view all the answers

What is the decay to higher vibrational energy levels of S0 called?

Internal conversion Signup and view all the answers

What is the process of emission of light from any substance other than fluorescence?

Luminescence Signup and view all the answers

What is fluorescence anisotropy based on?

Difference in physical property of a material along different axes Signup and view all the answers

What decreases measured anisotropy in fluorescence anisotropy measurements?

Rotational diffusion Signup and view all the answers

What is resonance energy transfer (RET) based on?

Emission spectrum of a donor overlapping with the absorption spectrum of an acceptor Signup and view all the answers

What is steady-state fluorescence measurement performed with?

Constant illumination and observation Signup and view all the answers

What is lost in the time averaging process in time-resolved fluorescence?

Molecular information Signup and view all the answers

What does the Perrin equation relate to in fluorescence measurements?

Intensity and anisotropy at t = 0 Signup and view all the answers

What is the Förster distance (R0) related to in resonance energy transfer (RET)?

Distance between the donor and acceptor Signup and view all the answers

What are intrinsic fluorophores?

Fluorophores that occur naturally Signup and view all the answers

What is fluorescence correlation spectroscopy (FCS) based on?

Temporal fluctuations occurring in a small observed volume Signup and view all the answers

What does fluorescence polarization or anisotropy indicate?

Molecular size and rotation speed Signup and view all the answers

What does quenching of fluorescence reveal?

Whether quenching is due to diffusion or to complex formation Signup and view all the answers

What is the main characteristic of single molecule detection (SMD)?

Gives very high obtainable sensitivity Signup and view all the answers

What is the main principle of resonance energy transfer (RET)?

Transfer of energy from an excited donor molecule to an acceptor molecule Signup and view all the answers

What are extrinsic fluorophores?

Fluorophores added to a sample that does not display the desired spectral properties Signup and view all the answers

What is the main purpose of emission spectra and the Stokes shift in fluorescence?

To provide molecular information Signup and view all the answers

What characteristic indicates whether a fluorophore is suitable for a sample being studied?

Does not substantially perturb the biomolecule or process being studied Signup and view all the answers

According to Kasha’s Rule, from which level do molecules emit?

S2 level Signup and view all the answers

What determines the emitted photons and interaction time for a fluorophore?

Quantum yield and lifetime Signup and view all the answers

What type of quenching decreases intensity and can be collisional or static?

Fluorescence quenching Signup and view all the answers

Which principle explains fast absorption and longer emission timescales?

Franck-Condon principle Signup and view all the answers

What provides information on dynamic processes in solution or macromolecules?

Quenching Signup and view all the answers

What is directionally dependent and differs from isotropy?

Fluorescence anisotropy Signup and view all the answers

Which of the following is a common quencher for fluorescence?

O2 Signup and view all the answers

Study Notes

Fluorescence and Quenching in Molecular Processes

Fluorophores exist in two ionization states with different absorption and emission spectra
Kasha’s Rule states that molecules emit from the S2 level
Symmetry of absorbance and emission spectra is due to similar transitions and vibrational energy levels of S0 and S1
Quantum yield and lifetime determine emitted photons and interaction time for the fluorophore
Fluorescence quenching decreases intensity and can be collisional or static
Stern-Volmer equation includes constants and quencher concentration
Common quenchers include O2, halogens, amines, and electron-deficient molecules
Quenching provides information on dynamic processes in solution or macromolecules
Franck-Condon principle explains fast absorption and longer emission timescales
Fluorescence anisotropy is directionally dependent and differs from isotropy

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Description

Test your knowledge of fluorescence and quenching in molecular processes with this quiz. Explore topics such as fluorophore ionization states, Kasha's Rule, quantum yield, fluorescence quenching, Stern-Volmer equation, common quenchers, Franck-Condon principle, and fluorescence anisotropy.