What is it about?
To study light absorbing proteins in laboratory setting, lasers are used to simulate the light that the protein would experience in its natural environment. The problem is that experiments of this type have been conducted using lasers much more powerful than the light the protein sees in nature. The excessive laser power being used in these experiments nullifies the biological relevance of the results. For example, it does not make sense to study the light absorbing protein responsible for human vision with a laser that is significantly more intense than sunlight. So how much laser power is too much? At what point does the behaviour of the protein in the lab no longer reflect what occurs in nature? Here we develop a purely theoretical framework starting with the Schrödinger equation to determine this laser intensity threshold and we see excellent agreement with experimental results.
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Why is it important?
The use of overpowered lasers to study light absorbing proteins is commonplace and needs to be prevented moving forward. The importance of preventing this systematic error from propagating further cannot be understated. This work provides a theoretical foundation to formulate guidelines for selecting the laser power used in these studies. Additionally, this work provides a metric to evaluate the validity of previously published results.
Perspectives
The theory presented here provides a starting point for the prediction of the laser intensity threshold for ionization if extended to higher orders. This could allow for laser ablation depths to be predicted theoretically which would be very useful for a wide variety of applications including laser surgery, mass spectrometry, etc. Additionally, the resonant enhancement factor presented here can be used to directly compare the laser intensities used in various experiments. This theory provides a good starting point for more work in this field.
William Francis
University of Toronto
Read the Original
This page is a summary of: Resonant multiphoton processes and excitation limits to structural dynamics, Structural Dynamics, March 2024, American Institute of Physics,
DOI: 10.1063/4.0000239.
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