1. What is Efficiency of Energy Transfer?

The Efficiency of Energy Transfer describes the efficiency of energy transfer between two light-sensitive molecules (chromophores) in Fluorescence Resonance Energy Transfer (FRET) processes. It quantifies how effectively energy is transferred from a donor molecule to an acceptor molecule.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( E \) — Efficiency of Energy Transfer (unitless, range 0-1)
• \( \zeta_{DA} \) — Donor fluorescence lifetime in the presence of an acceptor (seconds)
• \( \zeta_D \) — Donor fluorescence lifetime in the absence of an acceptor (seconds)

Explanation: The efficiency is calculated by comparing the donor's fluorescence lifetime with and without the presence of an acceptor molecule. A higher efficiency indicates more effective energy transfer.

3. Importance of FRET Efficiency Calculation

Details: FRET efficiency calculation is crucial for studying molecular interactions, protein-protein interactions, and distance measurements at the nanoscale level in biological systems. It helps researchers understand molecular proximity and interactions in live cells.

4. Using the Calculator

Tips: Enter donor lifetime with FRET and donor lifetime without FRET in seconds. Both values must be positive, and the donor lifetime with FRET should be less than or equal to the donor lifetime without FRET.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range for FRET efficiency?
A: FRET efficiency typically ranges from 0 (no energy transfer) to 1 (complete energy transfer), though values between 0.1 and 0.9 are most commonly observed in biological systems.

Q2: How does distance affect FRET efficiency?
A: FRET efficiency is highly distance-dependent, decreasing with the sixth power of the distance between donor and acceptor molecules (Förster radius typically 1-10 nm).

Q3: What factors can affect fluorescence lifetime measurements?
A: Environmental factors such as pH, temperature, solvent polarity, and the presence of quenchers can affect fluorescence lifetime measurements and thus FRET efficiency calculations.

Q4: Can this formula be used for all FRET pairs?
A: Yes, this lifetime-based method is generally applicable to all FRET pairs, though the specific Förster radius and other parameters may vary between different donor-acceptor pairs.

Q5: What are the advantages of lifetime-based FRET measurements?
A: Lifetime measurements are less affected by concentration variations, photobleaching, and excitation intensity fluctuations compared to intensity-based FRET measurements.