Quantum Dot-Enriched Cas Proteins for RNA Purification
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Solution Overview
Problem
Current nucleic acid detection methods destroy the detected nucleic acid, and there is a need for techniques to enrich specifically sought-after sequences from complex mixtures where the target is present in minute amounts, necessitating excessive sample amounts for sequencing.
Innovation Solution
The use of mutated Cas proteins (such as dCas13, dCas12, or dCas9) that bind target RNA or DNA specifically, using guide RNA molecules and quantum dots to concentrate and purify the target sequences without destroying them, allowing for direct processing via sequencing technologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current nucleic acid detection methods are used, then detection sensitivity is improved, but the detected nucleic acid is destroyed
Solution Approach 1:
The patent introduces an intermediary system consisting of guide RNA molecules that direct Cas proteins to target sequences, and quantum dots that serve as physical carriers for enrichment. This intermediary approach allows detection and enrichment without direct destruction of the target nucleic acid, resolving the contradiction between detection sensitivity and nucleic acid integrity
Solution Approach 2:
The method creates a physical copy/enrichment of the target sequence by binding Cas proteins (guided by crRNA) to the target RNA, which then associates with quantum dots. This copying mechanism allows the target to be enriched and detected without destroying the original molecule, maintaining integrity while achieving sensitivity
2Measurement precision
If conventional sequencing preparation methods are used, then sequencing coverage is improved, but excessive sample amounts are required
Solution Approach 1:
The patent extracts and enriches specifically sought-after sequences from complex environmental mixtures using guide RNA-directed Cas protein binding followed by quantum dot association. This extraction of target sequences from background noise allows achieving sufficient sequencing coverage with minimal sample amounts, as only the relevant targets are enriched for sequencing
Solution Approach 2:
The invention creates a composite structure where Cas proteins, guide RNA, and quantum dots work together as an integrated enrichment system. This composite approach enables highly specific enrichment of target sequences from complex mixtures, reducing the total sample amount needed while maintaining sequencing coverage
3Measurement precision
If quantum dots are used to bind Cas proteins, then enrichment specificity is improved, but device complexity increases
Solution Approach 1:
The patent utilizes quantum dots, which are characterized by their size-dependent optical properties and fluorescence emission. The quantum dots can be detected and tracked through their optical signals, providing a means to monitor and verify the enrichment process without adding significant operational complexity to the overall system
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
Enables sequence-specific enrichment and purification of long RNA or DNA sequences from complex matrices, reducing sample requirements and maintaining sequence integrity for subsequent analysis, facilitating efficient and non-destructive analysis suitable for modern sequencing technologies.
Implementation Method 1
a first surface functionalized to bind to the Cas protein
Implementation Method 2
allowing the QD nanoparticle binds to the complex to form a QD-complex
Implementation Method 3
digesting the Cas13 protein in the QD-complex with a protease to release the target RNA
Implementation Method 4
the crRNA is capable of binding to both the Cas13 protein and to the target RNA
Data Source
AI summary
One can enrich nucleic acid (RNA or DNA) from within a complex mixture in a sequence-specific manner by using a mutant of a Cas enzyme lacking nuclease activity, for example a mutant of Cas13a (dCas) from Leptotrichia wadeii. The nucleic acid is bound by the mutant protein as directed by guide RNA molecules (crRNA) and purified after association with an appropriate surface, such as quantum dots or functionalized beads. The nucleic acid is separated from the Cas and purified after precipitation or interaction with another surface. The resulting product can be directly processed via long-read sequencing.