Enhanced Adapter Ligation for NGS Library Preparation

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Solution Overview

Problem

Current next-generation sequencing (NGS) technologies face challenges in library preparation due to low yields, particularly due to damaged 5' ends from physical fragmentation and inefficient adapter ligation, leading to reduced library complexity and increased PCR duplicates from insufficient DNA input.

Innovation Solution

An enhanced adapter ligation method is introduced, which involves dephosphorylation of DNA fragments, trimming of damaged 3' bases, and strategic use of modified adapters to prevent concatamer formation and adapter dimerization, allowing for efficient ligation of adapters to both ends of DNA fragments, even with reduced DNA input.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If physical fragmentation is used to fragment DNA, then DNA size distribution can be controlled, but DNA ends are damaged and conventional polishing is insufficient to generate ligation-compatible ends

Engineering Contradiction:

ImproveDNA size distribution controlVSAvoidligation compatibility of DNA ends

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies preliminary action by performing end-repair and phosphorylation treatments on physically fragmented DNA ends before adapter ligation. This pre-processing ensures that damaged 5' and 3' ends are repaired and made ligation-competent, resolving the contradiction between controlled fragmentation and ligation compatibility.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces enzymatic intermediaries (polymerases, phosphatases, and ligases) that mediate the conversion of damaged physical fragmentation ends into ligation-compatible ends. These enzymes act as intermediaries between the physical fragmentation process and the adapter ligation step, enabling efficient library construction.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If conventional adapter ligation is performed on both strands simultaneously, then the process is simplified, but it remains unknown which strand is limiting and efficiency is reduced

Engineering Contradiction:

Improveprocess simplicityVSAvoidadapter ligation efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent segments the adapter ligation process into strand-specific reactions, separately optimizing ligation for each strand. This segmentation allows identification of the limiting strand and enables targeted optimization of ligation conditions for each strand, thereby improving overall efficiency while maintaining procedural simplicity.

Inventive Principle:

Principle #1Segmentation

3Quantity of substance

If DNA input is reduced to handle limited samples, then sample preservation is improved, but library complexity decreases and PCR duplicates increase

Engineering Contradiction:

ImproveDNA input quantityVSAvoidlibrary complexity and data quality

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies parameter changes by optimizing enzymatic reaction conditions (enzyme concentrations, incubation times, temperatures) to maximize adapter ligation efficiency at low DNA inputs. These parameter optimizations ensure high library complexity and minimal PCR duplicates even when working with limited DNA quantities.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces enhanced enzymatic intermediaries that facilitate efficient adapter ligation under low-input conditions, preserving library complexity and reducing PCR artifact formation.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Reliability

If enzymatic digestion is used to fragment DNA, then DNA ends are suitable for polishing and ligation, but it is difficult to control the reaction and produce fragments of predictable length

Engineering Contradiction:

Improveligation compatibility of DNA endsVSAvoidDNA fragment length control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent uses enzymatic intermediaries (polymerases and phosphatases) to process the ends of physically fragmented DNA, providing the ligation compatibility that enzymatic digestion would otherwise ensure, while maintaining the length control advantages of physical methods.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 method significantly increases library yield and enables the construction of high-quality libraries from lower DNA quantities, reducing PCR duplicates and improving sequencing data output.

Implementation Method 1

The 5′-3′ polymerase and the 3′-5′ exonuclease activities of T4 DNA polymerase excise 3′ overhangs and fill-in 3′ recessed ends

Methodology Applied

Scientific Effect3'-5' exonuclease activity: Enzyme

Implementation Method 2

The 5′-3′ polymerase and the 3′-5′ exonuclease activities of T4 DNA polymerase excise 3′ overhangs and fill-in 3′ recessed ends

Methodology Applied

Scientific EffectDNA polymerase activity: Enzyme

Implementation Method 3

The T4 polynucleotide kinase in the polishing mix adds a phosphate to the 5′ ends of DNA fragments that can be lacking such, thus making them ligation-compatible to NGS adapters

Methodology Applied

Scientific EffectPhosphorylation: Enzyme