Photoswitchable Species Detection Using Harmonic Fluorescence Signals
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Solution Overview
Problem
Existing methods for detecting and discriminating spectrally similar reversibly photoswitchable fluorescent proteins (RSFPs) face limitations in multiplexed fluorescence imaging, particularly due to narrow lifetime dispersion and the need for complex deconvolution or subtraction schemes, which affect signal-to-noise ratio and implementation complexity.
Innovation Solution
A method that utilizes harmonic components of the fluorescence signal, including quadrature components of odd harmonics and in-phase components of even harmonics, to detect and discriminate reversibly photoswitchable chemical species, such as RSFPs, by periodically modulating illumination at specific frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spectral discrimination is used to identify and discriminate fluorescent labels, then fluorescence imaging can be performed with high sensitivity and versatility, but the ability to discriminate fluorophores is limited to a maximum of four labels due to overlapping absorption and emission bands
Solution Approach 1:
The patent transitions from spectral discrimination (one dimension) to temporal discrimination by exploiting the time response of fluorescence to light variations. By modulating illumination at different frequencies and analyzing harmonic components at different time scales, the method adds a temporal dimension that enables discrimination of multiple spectrally similar fluorophores beyond the four-label limit of spectral methods.
Solution Approach 2:
The patent employs periodic modulation of illumination light at fundamental frequencies and analyzes harmonic components (second, third, and higher order harmonics) to discriminate fluorophores. Different fluorophores exhibit distinct harmonic responses to periodic illumination, enabling multiplexed detection through frequency-domain analysis rather than spectral separation.
2Measurement precision
If fluorescence lifetime imaging is used to distinguish fluorophores, then temporal information can be exploited, but the technique requires sophisticated instruments, fast electronics, and suffers from narrow lifetime dispersion requiring deconvolution or subtractive schemes
Solution Approach 1:
Instead of measuring absolute fluorescence lifetimes with complex time-correlated single photon counting electronics, the patent changes the approach by modulating illumination at specific fundamental frequencies and detecting harmonic components. This transforms the measurement from direct lifetime detection to frequency-response analysis, simplifying the instrumentation while maintaining discrimination capability.
Solution Approach 2:
The patent replaces the complex mechanical and electronic system of fast electronics and deconvolution algorithms with a simpler frequency-modulation approach. By using periodic illumination and detecting harmonic responses, the method eliminates the need for sophisticated time-correlation electronics and computationally intensive deconvolution procedures.
3Adaptability or versatility
If deconvolution or subtractive schemes are used in fluorescence lifetime imaging, then multiplexed observations can be achieved, but the signal-to-noise ratio decreases and implementation complexity increases
Solution Approach 1:
The patent uses periodic modulation of illumination at fundamental frequencies and detects harmonic components directly in the frequency domain. This avoids the need for subtractive schemes that combine multiple measurements, as each fluorophore's harmonic response can be independently measured and discriminated, preserving signal-to-noise ratio while enabling multiplexed observation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Improves discrimination of spectrally similar RSFPs with enhanced rejection of spectral interferences and provides quantitative information without requiring reference pixels or empirical optimization, facilitating real-time biological observations.
Implementation Method 1
illuminating the sample with a first light at a first wavelength suitable to be absorbed by the chemical species triggering a reaction affecting at least one optical property of the chemical species
Implementation Method 2
fluorescence imaging, and particularly fluorescence microscopy, has become essential for biology in view of the high sensitivity and versatility of fluorescent labels
Data Source
AI summary
A method for detecting a reversibly photoswitchable chemical species in a sample, includes the steps of: a) illuminating the sample with light suitable to be absorbed by the chemical species triggering a reaction affecting an optical property of the chemical species, the first light being periodically-modulated at a fundamental modulation frequency; b) measuring the evolution of the optical property; c) extracting at least one of an in-phase component at a frequency which is an even multiple of the fundamental modulation frequency; and a quadrature component at a frequency which is an odd multiple of the fundamental modulation frequency of a signal representing the evolution; and d) using the extracted component or components for detecting the chemical species. An apparatus for carrying out the method is also provided.