Fluorescence Quantum Yield In FRET Calculator

Fluorescence Quantum Yield Formula:

\[ \phi = \frac{nPe}{nPa} \]

Fluorescence Quantum Yield (φ):

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1. What is Fluorescence Quantum Yield?

Fluorescence Quantum Yield is defined as the ratio of the number of photons emitted to the number of photons absorbed. It is a key parameter in fluorescence spectroscopy and FRET (Förster Resonance Energy Transfer) studies, measuring the efficiency of the fluorescence process.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ \phi = \frac{nPe}{nPa} \]

Where:

\( \phi \) — Fluorescence Quantum Yield
\( nPe \) — Number of Photons Emitted
\( nPa \) — Number of Photons Absorbed

Explanation: The quantum yield represents the efficiency of the fluorescence process, with values ranging from 0 (no fluorescence) to 1 (maximum efficiency where every absorbed photon results in an emitted photon).

3. Importance of Quantum Yield Calculation

Details: Accurate quantum yield measurement is crucial for characterizing fluorescent molecules, optimizing FRET efficiency, designing fluorescent probes, and comparing the brightness of different fluorophores.

4. Using the Calculator

Tips: Enter the number of photons emitted and absorbed as positive integers. The number of photons absorbed must be greater than zero for valid calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical quantum yield value for good fluorophores?
A: Good fluorophores typically have quantum yields between 0.5 and 1.0. Values above 0.7 are considered excellent for most applications.

Q2: How does quantum yield relate to FRET efficiency?
A: Quantum yield affects the brightness of both donor and acceptor fluorophores in FRET, which influences the overall FRET efficiency and the dynamic range of FRET-based measurements.

Q3: Can quantum yield be greater than 1?
A: No, quantum yield cannot exceed 1 as it represents the ratio of emitted to absorbed photons. However, in some special cases like photon upconversion, the apparent quantum yield might exceed 1.

Q4: What factors affect fluorescence quantum yield?
A: Quantum yield is affected by molecular structure, solvent environment, temperature, pH, and the presence of quenchers or FRET acceptors.

Q5: How is quantum yield measured experimentally?
A: Quantum yield is typically measured using comparative methods with standard fluorophores of known quantum yield or using integrating spheres for absolute measurements.