Electron Density Map Generation for Flexible Macromolecules
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Solution Overview
Problem
Existing methods for obtaining three-dimensional electron density maps of flexible macromolecules in solution fail to capture dynamic structures, averaging out the electron density and losing molecular characteristics.
Innovation Solution
An electron density map specifying apparatus and method that generates multiple electron density maps by randomly assigning electron densities to voxels, calculates scaling structure factors, and selects a representative map based on correlation and convergence criteria, using χ² as an index to ensure accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an electron density map is obtained by averaging multiple electron density maps, then the calculation is reasonable for rigid molecules, but the dynamic structures of flexible molecules are averaged out and the electron density lacks molecular characteristics
Solution Approach 1:
The patent divides the electron density map into multiple discrete voxel units and processes each voxel independently through iterative searching. This segmentation allows the method to capture local dynamic variations in flexible molecules rather than averaging them out, while still maintaining overall structural accuracy through the collective contribution of individual voxels.
Solution Approach 2:
The patent introduces a flexibility parameter that dynamically adjusts the electron density calculation based on molecular rigidity. For flexible molecules, the method allows greater variation in electron density across different conformations, preserving dynamic structural information. For rigid molecules, the method converges to a stable averaged solution, maintaining calculation reliability.
2Measurement precision
If the volume of a cube in real space is represented by a voxel discretized in an N×N×N grid, then the electron density map can be calculated iteratively, but the computational complexity increases with higher resolution
Solution Approach 1:
The patent implements an iterative searching method that progressively refines electron density values from coarse to fine resolution. Instead of calculating all N×N×N voxels simultaneously at full resolution, the method performs partial iterations that converge to the final solution, reducing computational complexity while maintaining measurement precision.
Solution Approach 2:
The patent employs continuous iterative optimization where each iteration builds upon the previous results. The electron density calculation continues through multiple cycles of structure factor computation and refinement, maintaining useful computational action throughout the process rather than requiring complete recalculation, thus managing complexity while achieving high resolution.
3Reliability
If multiple electron density maps are generated for a particular voxel size, then the statistical reliability improves, but the calculation time increases
Solution Approach 1:
The patent performs preliminary calculations to determine optimal convergence criteria and voxel size parameters before generating multiple electron density maps. By pre-establishing the search parameters and convergence thresholds, the method reduces redundant computations in subsequent iterations, improving statistical reliability while minimizing calculation time.
Solution Approach 2:
The patent implements feedback mechanisms where each generated electron density map is evaluated against convergence criteria and statistical metrics. Maps that meet reliability thresholds are retained while others are discarded or refined, providing feedback that guides subsequent generations. This selective process improves overall statistical reliability without requiring an excessive number of calculations.
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
Accurately reproduces electron density maps of flexible macromolecules in solution, capturing dynamic structures and molecular characteristics, enabling precise visualization of biomacromolecules without prior information.
Implementation Method 1
When X-rays are applied to biomacromolecules that are in a state free to move in a solution, a ring-shaped scattered ray is generated instead of a spot. A technique is known in which such a scattered ray is detected, and a three-dimensional electron density map of a target molecule is obtained from the acquired measured X-ray scattering profile
Data Source
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AI summary
An electron density map specifying apparatus, system, method, and program capable of accurately reproducing an electron density map of a macromolecule in a solution having a dynamically fluctuating structure are provided. An electron density map specifying apparatus 200 for specifying an electron density map of a macromolecule in a solution, comprises an electron density map generating section 221 for generating a plurality of electron density maps from a measured X-ray scattering profile acquired by measuring a sample, an index calculating section 226 for calculating an index representing a degree of coincidence between an X-ray scattering profile calculated from each of the plurality of electron density maps and the measured X-ray scattering profile, and an electron density map selecting section 258 for selecting a representative electron density map from the plurality of electron density maps based on the calculated index.