SHG Microscopy for Sub-Diffraction Protein Crystal Detection
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Solution Overview
Problem
Current methods for detecting protein crystals are limited in sensitivity and selectivity, particularly for sub-diffraction limited crystals, and struggle to distinguish between protein crystals and amorphous aggregates, leading to inefficiencies in identifying conditions for generating diffraction-quality crystals.
Innovation Solution
The use of second harmonic generation (SHG) microscopy, which enables sensitive and selective imaging of protein microcrystals by producing a second harmonic generation signal, allowing for the detection of crystals with dimensions below the optical diffraction limit and distinguishing between protein crystals and amorphous aggregates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical detection methods (image analysis or birefringence) are used, then the detection process is simple and compatible with diverse platforms, but the detection limit is restricted to crystals with dimensions of several micrometers or larger
Solution Approach 1:
The patent uses fluorescent dyes as intermediary substances that selectively bind to protein crystals. These dyes act as mediators between the crystal structure and the detection system, enabling sensitive fluorescence-based detection of sub-diffraction limited crystals while maintaining compatibility with standard microscopy platforms.
Solution Approach 2:
The patent employs fluorescent dyes that exhibit specific optical properties when bound to protein crystals versus when solvated. The differential fluorescence signal (color change in optical detection) between bound and free dye molecules enables selective detection of crystals below the diffraction limit while rejecting background from solvated dye.
2Measurement precision
If fluorescent dyes are used to improve detection sensitivity, then sub-diffraction limited crystals can be detected, but significant background signal from solvated dye molecules and amorphous aggregates is introduced
Solution Approach 1:
The patent exploits the local quality difference in fluorescence properties between dye molecules bound to crystalline structures versus those in solution or bound to amorphous aggregates. By optimizing dye selection and imaging parameters, the method enhances signal from crystal-bound dye while suppressing background from solvated dye, achieving high contrast detection.
Solution Approach 2:
The patent changes multiple parameters including dye concentration, incubation time, washing steps, and microscopy imaging parameters (excitation intensity, detection wavelength, integration time) to optimize the signal-to-background ratio. These parameter adjustments maximize crystal detection sensitivity while minimizing background from solvated dye and amorphous aggregates.
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
This approach significantly reduces the detection limits for protein crystallization, enabling the identification of diffraction-quality protein crystals with improved sensitivity and selectivity, and is compatible with various protein crystallization platforms.
Implementation Method 1
subjecting a sample comprising protein in solid form to second order non-linear optical imaging; and detecting a second harmonic generation signal produced by a protein crystal
Data Source
AI summary
Methods for detecting and evaluating the quality of protein crystals are provided comprising subjecting a sample to second order non-linear optical imaging and detecting the second harmonic generation signal.