Recombinant Nucleosome Standards for Quantification Accuracy
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Solution Overview
Problem
Current nucleosome-based assays lack proper controls for quantification, relying on poorly defined exogenous chromatin preparations that introduce variability and cannot accurately determine if combinatorial marks are present on the same nucleosome.
Innovation Solution
The use of recombinant / semi-synthetic nucleosomes carrying histone and/or DNA modifications as fully defined quantification standards, allowing for accurate calibration and absolute quantification of single or combinatorial nucleosome modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If exogenous chromatin preparations are used as quantification standards, then the assay can be performed, but the quantification accuracy deteriorates due to poor definition and variability
Solution Approach 1:
The patent creates recombinant nucleosomes that are precise copies of endogenous nucleosomes, including identical histone variants, post-translational modifications, and DNA sequences. These recombinant copies serve as accurate quantification standards, eliminating the variability inherent in exogenous chromatin preparations while maintaining biological relevance for measuring nucleosome modifications in clinical samples
Solution Approach 2:
The patent systematically varies specific parameters of the recombinant nucleosomes, such as the type of histone modification (e.g., H3K4me3, H3K27ac), the DNA sequence, and the histone variant composition, to create a panel of standardized nucleosomes that can accurately quantify different modification states. This controlled parameter variation enables precise differentiation and quantification of various nucleosome modification patterns
2Loss of information
If exogenous chromatin preparations are used, then the assay can proceed, but the ability to determine combinatorial marks on the same nucleosome is lost
Solution Approach 1:
The patent segments the complex chromatin information into discrete, controllable elements by creating recombinant nucleosomes with specific combinations of histone modifications (e.g., H3K4me3 combined with H3K27ac). Each recombinant nucleosome represents a defined segment of epigenetic information, allowing precise determination of whether multiple modifications coexist on the same nucleosome particle rather than being lost in heterogeneous exogenous preparations
3Measurement precision
If recombinant nucleosomes are used as standards, then quantification accuracy improves, but the assay complexity increases
Solution Approach 1:
The recombinant nucleosome standards serve multiple functions simultaneously: they act as quantification references, positive controls, and calibration standards for different modification types. A single panel of recombinant nucleosomes with varying modifications can be used across multiple assays and applications, reducing overall complexity despite the initial investment in creating the standardized panel
Solution Approach 2:
The recombinant nucleosomes are prepared and characterized in advance before clinical assays are performed. This preliminary creation and validation of standardized nucleosome references eliminates the need for complex sample preparation and validation steps during actual patient sample analysis, simplifying the routine assay workflow while maintaining high quantification accuracy
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 provides stable and reliable calibration in biological samples, especially in plasma, enabling precise quantification of nucleosome modifications and potentially improving biomarker detection for diseases.
Implementation Method 1
adding one or more affinity reagents to the biological sample and recombinant nucleosome reference samples, wherein the affinity reagent targets modified histone or modified DNA
Data Source
Figure 1A~1C
Figure 2A~2B
Figure 3A~3C
AI summary
The invention relates to the use of recombinant / semi-synthetic nucleosomes carrying histone and/or DNA modifications as a reference standard for quantification of covalently modified (on the histone proteins or wrapping DNA), variant, or mutant nucleosomes (collectively "modified nucleosomes" or "nucleosome modifications") from a biological sample. The invention further relates to methods of using the assay to accurately quantify single or combinatorial nucleosome modifications as biomarkers of disease.