ICeChIP Assay for Absolute Histone Density Quantification
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Solution Overview
Problem
Chromatin immunoprecipitation (ChIP) technology faces challenges in providing absolute measurements of histone modifications, leading to relative and inconsistent data due to antibody quality issues, lack of standardization, and variability in experimental conditions, making it difficult to compare results across samples and patients.
Innovation Solution
The development of Internal Standard Calibrated ChIP (ICeChIP) methods and materials that use reconstituted, semi-synthetic DNA-binding proteins with native-like affinity and specificity, along with barcode molecules, to transform pull-down assay results into standardized absolute units, enabling precise quantification of epitope densities and comparison across samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ChIP methods are used, then the assay can be performed with existing reagents and protocols, but the measurement precision and reliability are poor due to lack of standardization and antibody variability
Solution Approach 1:
The patent applies preliminary action by spiking the chromatin sample with a known amount of exogenous DNA (such as lambda DNA or other standardized DNA) before performing the ChIP assay. This pre-added standard serves as an internal reference that allows subsequent quantification of enrichment efficiency and enables conversion of relative ChIP signals into absolute measurements of DNA-protein complex density, thereby improving measurement precision without requiring complex instrumentation
Solution Approach 2:
The patent uses an intermediary approach by introducing a standardized DNA control substance that mediates between the ChIP assay process and the final quantification. This intermediary DNA standard undergoes the same experimental procedures as the test samples, allowing calculation of recovery efficiency and enabling accurate normalization across different experiments, antibodies, and conditions
2Reliability
If conventional ChIP methods are used, then the experimental procedure can be completed, but the reliability and reproducibility across different samples and patients are poor due to antibody quality issues and lack of standardization
Solution Approach 1:
The patent applies preliminary action by spiking the chromatin sample with a known amount of exogenous DNA (such as lambda DNA or other standardized DNA) before performing the ChIP assay. This pre-added standard serves as an internal reference that allows subsequent quantification of enrichment efficiency and enables conversion of relative ChIP signals into absolute measurements of DNA-protein complex density, thereby improving measurement precision without requiring complex instrumentation
Solution Approach 2:
The patent implements feedback by using the standardized DNA control to calculate enrichment efficiency and recovery rates, which then feed back into the data analysis to normalize and correct the ChIP results. This feedback mechanism allows for quantitative assessment of antibody performance and enables comparison across different experiments, improving reliability and reproducibility
3Measurement precision
If quantitative assessment of DNA-protein complex density is achieved through ICeChIP, then measurement precision and reliability improve, but the device complexity and procedural steps increase
Solution Approach 1:
The patent applies preliminary action by spiking the chromatin sample with a known amount of exogenous DNA (such as lambda DNA or other standardized DNA) before performing the ChIP assay. This pre-added standard serves as an internal reference that allows subsequent quantification of enrichment efficiency and enables conversion of relative ChIP signals into absolute measurements of DNA-protein complex density, thereby improving measurement precision without requiring complex instrumentation
Solution Approach 2:
The patent applies parameter changes by transforming the output data from relative enrichment ratios to absolute DNA-protein complex density values through mathematical conversion using the standardized control. This parameter transformation enables quantitative comparison across different samples and experiments while maintaining simplicity in the physical assay procedure
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
ICeChIP allows for accurate and reproducible measurement of histone modification densities, improving data interpretation and enabling reliable medical diagnostics and research by providing a standardized scale for comparing pull-down assay results, reducing experimental variability and enhancing the precision of data analysis.
Implementation Method 1
an affinity reagent that binds a particular protein or post-translational modification thereof to pull-down specific fragments of chromatin
Data Source
AI summary
One aspect of the present invention describes materials and methods of quantitatively measuring the density or percent occupancy of DNA binding proteins such as histones, histone variants, histone post translational modifications and transcription factors in chromatin at given DNA loci. One embodiment measures a factor's average quantity at specific gene loci, and controls for a number of pitfalls concerning antibody quality and handling issues. Other embodiments include calibrating and quantifying chromatin immunoprecipitation assays, assessing an affinity reagent specificity, as well as required reagents and their formulation in kits. Another embodiment allows for the diagnosis of a condition or disease by measuring the density of a histone modification at a genomic locus.