Ligation sequencing gDNA - Multiplex Ligation Sequencing Kit V14 XL (SQK-MLK114.96-XL)

Oxford Nanopore Technologies
Document type icon

PromethION: Protocol

Ligation sequencing gDNA - Multiplex Ligation Sequencing Kit V14 XL (SQK-MLK114.96-XL) V MLK_9193_v114_revB_30Sep2024

  • For barcoding of native genomic DNA libraries
  • Requires the Multiplex Ligation Sequencing Kit V14 XL
  • No PCR required
  • Features 96 unique barcodes
  • Enables low-plex sequencing
  • Allows analysis of native DNA
  • Compatible with R10.4.1 flow cells

For Research Use Only

FOR RESEARCH USE ONLY

Overview

  • For barcoding of native genomic DNA libraries
  • Requires the Multiplex Ligation Sequencing Kit V14 XL
  • No PCR required
  • Features 96 unique barcodes
  • Enables low-plex sequencing
  • Allows analysis of native DNA
  • Compatible with R10.4.1 flow cells

For Research Use Only

Document version: MLK_9193_v114_revB_30Sep2024

1. Overview of the protocol

Introduction to the manual Multiplex Ligation Sequencing Kit V14 XL protocol

This protocol describes how to carry out native barcoding of genomic DNA using the Multiplex Ligation Sequencing Kit V14 XL (SQK-MLK114.96-XL). This kit is designed to enable low-plex sequencing.

This manual protocol outlines sample preparation with two options for low-plex sequencing:

  • Two samples across one flow cell. Allowing users to sequence up to 96 samples across 48 flow cells, reducing cost per sample.
  • Three samples across two flow cells. Allowing users to sequence up to 96 samples across 64 flow cells, maximising data output.

Using this protocol provides users with an easy workflow for whole genome sequencing (WGS), while enabling scalability options to best suit their sequencing requirements.

To efficiently load multiple PromethION Flow Cells, we recommend using the Loading multiple PromethION Flow Cells protocol as a guideline.

Steps in the sequencing workflow:

Prepare for your experiment You will need to:

  • Extract your DNA, and check its length, quantity and purity. The quality checks performed during the protocol are essential in ensuring experimental success.
  • Ensure you have your sequencing kit, the correct equipment and third-party reagents
  • Download the software for acquiring and analysing your data
  • Check your flow cell to ensure it has enough pores for a good sequencing run

Library preparation

The table below is an overview of the steps required in the library preparation, including timings and optional stopping points.

Library preparation Process Time Stop option
DNA repair and end-prep Repair the fragmented DNA and prepare the DNA ends for barcode attachment 35 minutes 4°C overnight
Native barcode ligation Ligate the native barcodes to the DNA ends 60 minutes 4°C overnight
Adapter ligation and clean-up Attach the sequencing adapters to the barcoded DNA ends 50 minutes 4°C short-term storage or for repeated use, such as re-loading your flow cell
-80°C for single-use, long-term storage.
We strongly recommend sequencing your library as soon as it is adapted.
Priming and loading the flow cell Prime the flow cell and load the prepared library for sequencing 5 minutes

*Please note, timing estimates will vary depending on the number of samples being processed, number of pools generated, number of flow cells loaded and user experience.


MLK11496 workflow image loading options

Sequencing

You will need to:

  • Start a sequencing run using the MinKNOW software, which will collect raw data from the device and convert it into basecalled reads
  • Demultiplex barcoded reads in MinKNOW or the Guppy software
  • (Optional): Start the EPI2ME software and select a workflow for further analysis
IMPORTANT

We do not recommend mixing barcoded libraries with non-barcoded libraries prior to sequencing.

IMPORTANT

Optional fragmentation and size selection

By default, the protocol contains no DNA fragmentation step, however in some cases it may be advantageous to fragment your sample. For example, when working with lower amounts of input gDNA (100 ng – 500 ng), fragmentation will increase the number of DNA molecules and therefore increase throughput. Instructions are available in the DNA Fragmentation section of Extraction methods.

Additionally, we offer several options for size-selecting your DNA sample to enrich for long fragments - instructions are available in the Size Selection section of Extraction methods.

IMPORTANT

Compatibility of this protocol

This protocol should only be used in combination with:

  • Multiplex Ligation Sequencing Kit V14 XL (SQK-MLK114.96-XL)
  • R10.4.1 flow cells (FLO-PRO114M)
  • Sequencing Auxiliary Vials V14 (EXP-AUX003)
  • Native Barcoding Auxiliary Kit V14 (EXP-NBA114)
  • Flow Cell Wash Kit (EXP-WSH004)
  • Flow Cell Wash Kit XL (EXP-WSH004-XL)
  • PromethION 24/48 device - PromethION IT requirements document

2. Equipment and consumables

Materials
  • Multiplex Ligation Sequencing Kit V14 XL (SQK-MLK114.96-XL)
  • 1000 ng gDNA per sample
Consumables
  • PromethION Flow Cell
  • NEB Blunt/TA Ligase Master Mix (NEB, M0367)
  • NEBNext FFPE Repair Mix (NEB, M6630)
  • NEBNext Ultra II End repair/dA-tailing Module (NEB, E7546)
  • NEBNext Quick Ligation Module (NEB, E6056)
  • Eppendorf twin.tec® PCR plate 96 LoBind, semi-skirted (Eppendorf™, cat # 0030129504) with heat seals
  • 0.2 ml thin-walled PCR tubes
  • 1.5 ml Eppendorf DNA LoBind tubes
  • 2 ml Eppendorf DNA LoBind tubes
  • Nuclease-free water (e.g. ThermoFisher, AM9937)
  • Freshly prepared 80% ethanol in nuclease-free water
  • Qubit™ Assay Tubes (Invitrogen, Q32856)
  • Qubit dsDNA HS Assay Kit (Invitrogen, Q32851)
Equipment
  • PromethION sequencing device
  • PromethION Flow Cell Light Shield
  • Hula mixer (gentle rotator mixer)
  • Microfuge
  • Magnetic rack
  • Magnetic rack
  • Vortex mixer
  • Thermal cycler
  • Multichannel pipette and tips
  • P1000 pipette and tips
  • P200 pipette and tips
  • P100 pipette and tips
  • P20 pipette and tips
  • P10 pipette and tips
  • P2 pipette and tips
  • Ice bucket with ice
  • Timer
  • Qubit fluorometer (or equivalent)
Optional equipment
  • Agilent Bioanalyzer (or equivalent)
  • Eppendorf 5424 centrifuge (or equivalent)

For this protocol, you will need 1000 ng gDNA per sample.

Input DNA

How to QC your input DNA

It is important that the input DNA meets the quantity and quality requirements. Using too little or too much DNA, or DNA of poor quality (e.g. highly fragmented or containing RNA or chemical contaminants) can affect your library preparation.

For instructions on how to perform quality control of your DNA sample, please read the Input DNA/RNA QC protocol.

Chemical contaminants

Depending on how the DNA is extracted from the raw sample, certain chemical contaminants may remain in the purified DNA, which can affect library preparation efficiency and sequencing quality. Read more about contaminants on the Contaminants page of the Community.

Convenient reagent kits are available on request from NEB for the Multiplex Ligation Sequencing Kit V14 XL.

The NEB Next® Companion Module contains the appropriate reagents and the required volumes for the Multiplex Ligation Sequencing Kit V14 XL. For more information from NEB, please see "Find Products for Nanopore Sequencing".

Third-party reagents

We have validated and recommend the use of all the third-party reagents used in this protocol. Alternatives have not been tested by Oxford Nanopore Technologies.

For all third-party reagents, we recommend following the manufacturer's instructions to prepare the reagents for use.

Check your flow cell

We highly recommend that you check the number of pores in your flow cell prior to starting a sequencing experiment. This should be done within 12 weeks of purchasing for MinION/GridION/PromethION or within four weeks of purchasing Flongle Flow Cells. Oxford Nanopore Technologies will replace any flow cell with fewer than the number of pores in the table below, when the result is reported within two days of performing the flow cell check, and when the storage recommendations have been followed. To do the flow cell check, please follow the instructions in the Flow Cell Check document.

Flow cell Minimum number of active pores covered by warranty
Flongle Flow Cell 50
MinION/GridION Flow Cell 800
PromethION Flow Cell 5000
IMPORTANT

The Native Adapter (NA) used in this kit and protocol is not interchangeable with other sequencing adapters.

Multiplex Ligation Sequencing Kit V14 XL (SQK-MLK114.96-XL) contents

MLK114.96-XL tubes

Name Acronym Cap colour Number of vials Fill volume per vial (µl)
Native Adapter NA Green 1 320
Sequencing Buffer SB Red 4 1,700
Library Beads LIB Pink 4 1,800
Library Solution LIS White cap, pink sticker 4 1,800
EDTA EDTA Clear 1 700
Elution Buffer EB Clear cap, black label 1 10,000
Long Fragment Buffer LFB Clear cap, orange label 1 20,000
Flow Cell Flush FCF Clear cap, light blue label 6 15,500
Flow Cell Tether FCT White cap, purple sticker 2 1,600
AMPure XP Beads AXP Clear cap 1 6,000
Native Barcodes NB01-96 N/A 1 plate 8 µl per well

Note: This product contains AMPure XP Reagent manufactured by Beckman Coulter, Inc. and can be stored at -20°C with the kit without detriment to reagent stability.

The barcodes are orientated in columns in the barcode plate.

2021-09-14 Native Barcoding 96 kit contents v2 columns

To maximise the use of the Multiplex Ligation Sequencing Kit V14 XL, the Native Barcode Auxiliary V14 (EXP-NBA114) and the Sequencing Auxiliary Vials V14 (EXP-AUX003) expansion packs are available.

These expansion packs provide extra library preparation and flow cell priming reagents to allow users to get the most out of their use of the Multiplex Ligation Sequencing Kit V14 XL (SQK-MLK114.96-XL).

Both expansion packs used together will provide enough reagents for 12 reactions. For customers requiring extra EDTA to maximise the use of barcodes, we recommend using 0.25 M EDTA and adding 4 µl.

Native Barcode Auxiliary V14 (EXP-NBA114) contents:

EXP-NBA114 tubes

Name Acronym Cap colour No. of vials Fill volume per vial (µl)
Native Adapter NA Green 2 40
AMPure XP Beads AXP Amber 1 400
Long Fragment Buffer LFB Orange 2 1,800
Short Fragment Buffer SFB Clear 2 1,800

Note: This Product contains AMPure XP Reagent manufactured by Beckman Coulter, Inc. and can be stored at -20°C with the kit without detriment to reagent stability.

Sequencing Auxiliary Vials V14 (EXP-AUX003) contents:

EXP-AUX003 bottles

Name Acronym Cap colour No. of vials Fill volume per vial (μl)
Elution Buffer EB Black 2 500
Sequencing Buffer SB Red 2 700
Library Solution LIS White cap, pink label 2 600
Library Beads LIB Pink 2 600
Flow Cell Flush FCF light blue label 2 8,000
Flow Cell Tether FCT Purple 2 200

Native barcode sequences

Component Forward sequence Reverse sequence
NB01 CACAAAGACACCGACAACTTTCTT AAGAAAGTTGTCGGTGTCTTTGTG
NB02 ACAGACGACTACAAACGGAATCGA TCGATTCCGTTTGTAGTCGTCTGT
NB03 CCTGGTAACTGGGACACAAGACTC GAGTCTTGTGTCCCAGTTACCAGG
NB04 TAGGGAAACACGATAGAATCCGAA TTCGGATTCTATCGTGTTTCCCTA
NB05 AAGGTTACACAAACCCTGGACAAG CTTGTCCAGGGTTTGTGTAACCTT
NB06 GACTACTTTCTGCCTTTGCGAGAA TTCTCGCAAAGGCAGAAAGTAGTC
NB07 AAGGATTCATTCCCACGGTAACAC GTGTTACCGTGGGAATGAATCCTT
NB08 ACGTAACTTGGTTTGTTCCCTGAA TTCAGGGAACAAACCAAGTTACGT
NB09 AACCAAGACTCGCTGTGCCTAGTT AACTAGGCACAGCGAGTCTTGGTT
NB10 GAGAGGACAAAGGTTTCAACGCTT AAGCGTTGAAACCTTTGTCCTCTC
NB11 TCCATTCCCTCCGATAGATGAAAC GTTTCATCTATCGGAGGGAATGGA
NB12 TCCGATTCTGCTTCTTTCTACCTG CAGGTAGAAAGAAGCAGAATCGGA
NB13 AGAACGACTTCCATACTCGTGTGA TCACACGAGTATGGAAGTCGTTCT
NB14 AACGAGTCTCTTGGGACCCATAGA TCTATGGGTCCCAAGAGACTCGTT
NB15 AGGTCTACCTCGCTAACACCACTG CAGTGGTGTTAGCGAGGTAGACCT
NB16 CGTCAACTGACAGTGGTTCGTACT AGTACGAACCACTGTCAGTTGACG
NB17 ACCCTCCAGGAAAGTACCTCTGAT ATCAGAGGTACTTTCCTGGAGGGT
NB18 CCAAACCCAACAACCTAGATAGGC GCCTATCTAGGTTGTTGGGTTTGG
NB19 GTTCCTCGTGCAGTGTCAAGAGAT ATCTCTTGACACTGCACGAGGAAC
NB20 TTGCGTCCTGTTACGAGAACTCAT ATGAGTTCTCGTAACAGGACGCAA
NB21 GAGCCTCTCATTGTCCGTTCTCTA TAGAGAACGGACAATGAGAGGCTC
NB22 ACCACTGCCATGTATCAAAGTACG CGTACTTTGATACATGGCAGTGGT
NB23 CTTACTACCCAGTGAACCTCCTCG CGAGGAGGTTCACTGGGTAGTAAG
NB24 GCATAGTTCTGCATGATGGGTTAG CTAACCCATCATGCAGAACTATGC
NB25 GTAAGTTGGGTATGCAACGCAATG CATTGCGTTGCATACCCAACTTAC
NB26 CATACAGCGACTACGCATTCTCAT ATGAGAATGCGTAGTCGCTGTATG
NB27 CGACGGTTAGATTCACCTCTTACA TGTAAGAGGTGAATCTAACCGTCG
NB28 TGAAACCTAAGAAGGCACCGTATC GATACGGTGCCTTCTTAGGTTTCA
NB29 CTAGACACCTTGGGTTGACAGACC GGTCTGTCAACCCAAGGTGTCTAG
NB30 TCAGTGAGGATCTACTTCGACCCA TGGGTCGAAGTAGATCCTCACTGA
NB31 TGCGTACAGCAATCAGTTACATTG CAATGTAACTGATTGCTGTACGCA
NB32 CCAGTAGAAGTCCGACAACGTCAT ATGACGTTGTCGGACTTCTACTGG
NB33 CAGACTTGGTACGGTTGGGTAACT AGTTACCCAACCGTACCAAGTCTG
NB34 GGACGAAGAACTCAAGTCAAAGGC GCCTTTGACTTGAGTTCTTCGTCC
NB35 CTACTTACGAAGCTGAGGGACTGC GCAGTCCCTCAGCTTCGTAAGTAG
NB36 ATGTCCCAGTTAGAGGAGGAAACA TGTTTCCTCCTCTAACTGGGACAT
NB37 GCTTGCGATTGATGCTTAGTATCA TGATACTAAGCATCAATCGCAAGC
NB38 ACCACAGGAGGACGATACAGAGAA TTCTCTGTATCGTCCTCCTGTGGT
NB39 CCACAGTGTCAACTAGAGCCTCTC GAGAGGCTCTAGTTGACACTGTGG
NB40 TAGTTTGGATGACCAAGGATAGCC GGCTATCCTTGGTCATCCAAACTA
NB41 GGAGTTCGTCCAGAGAAGTACACG CGTGTACTTCTCTGGACGAACTCC
NB42 CTACGTGTAAGGCATACCTGCCAG CTGGCAGGTATGCCTTACACGTAG
NB43 CTTTCGTTGTTGACTCGACGGTAG CTACCGTCGAGTCAACAACGAAAG
NB44 AGTAGAAAGGGTTCCTTCCCACTC GAGTGGGAAGGAACCCTTTCTACT
NB45 GATCCAACAGAGATGCCTTCAGTG CACTGAAGGCATCTCTGTTGGATC
NB46 GCTGTGTTCCACTTCATTCTCCTG CAGGAGAATGAAGTGGAACACAGC
NB47 GTGCAACTTTCCCACAGGTAGTTC GAACTACCTGTGGGAAAGTTGCAC
NB48 CATCTGGAACGTGGTACACCTGTA TACAGGTGTACCACGTTCCAGATG
NB49 ACTGGTGCAGCTTTGAACATCTAG CTAGATGTTCAAAGCTGCACCAGT
NB50 ATGGACTTTGGTAACTTCCTGCGT ACGCAGGAAGTTACCAAAGTCCAT
NB51 GTTGAATGAGCCTACTGGGTCCTC GAGGACCCAGTAGGCTCATTCAAC
NB52 TGAGAGACAAGATTGTTCGTGGAC GTCCACGAACAATCTTGTCTCTCA
NB53 AGATTCAGACCGTCTCATGCAAAG CTTTGCATGAGACGGTCTGAATCT
NB54 CAAGAGCTTTGACTAAGGAGCATG CATGCTCCTTAGTCAAAGCTCTTG
NB55 TGGAAGATGAGACCCTGATCTACG CGTAGATCAGGGTCTCATCTTCCA
NB56 TCACTACTCAACAGGTGGCATGAA TTCATGCCACCTGTTGAGTAGTGA
NB57 GCTAGGTCAATCTCCTTCGGAAGT ACTTCCGAAGGAGATTGACCTAGC
NB58 CAGGTTACTCCTCCGTGAGTCTGA TCAGACTCACGGAGGAGTAACCTG
NB59 TCAATCAAGAAGGGAAAGCAAGGT ACCTTGCTTTCCCTTCTTGATTGA
NB60 CATGTTCAACCAAGGCTTCTATGG CCATAGAAGCCTTGGTTGAACATG
NB61 AGAGGGTACTATGTGCCTCAGCAC GTGCTGAGGCACATAGTACCCTCT
NB62 CACCCACACTTACTTCAGGACGTA TACGTCCTGAAGTAAGTGTGGGTG
NB63 TTCTGAAGTTCCTGGGTCTTGAAC GTTCAAGACCCAGGAACTTCAGAA
NB64 GACAGACACCGTTCATCGACTTTC GAAAGTCGATGAACGGTGTCTGTC
NB65 TTCTCAGTCTTCCTCCAGACAAGG CCTTGTCTGGAGGAAGACTGAGAA
NB66 CCGATCCTTGTGGCTTCTAACTTC GAAGTTAGAAGCCACAAGGATCGG
NB67 GTTTGTCATACTCGTGTGCTCACC GGTGAGCACACGAGTATGACAAAC
NB68 GAATCTAAGCAAACACGAAGGTGG CCACCTTCGTGTTTGCTTAGATTC
NB69 TACAGTCCGAGCCTCATGTGATCT AGATCACATGAGGCTCGGACTGTA
NB70 ACCGAGATCCTACGAATGGAGTGT ACACTCCATTCGTAGGATCTCGGT
NB71 CCTGGGAGCATCAGGTAGTAACAG CTGTTACTACCTGATGCTCCCAGG
NB72 TAGCTGACTGTCTTCCATACCGAC GTCGGTATGGAAGACAGTCAGCTA
NB73 AAGAAACAGGATGACAGAACCCTC GAGGGTTCTGTCATCCTGTTTCTT
NB74 TACAAGCATCCCAACACTTCCACT AGTGGAAGTGTTGGGATGCTTGTA
NB75 GACCATTGTGATGAACCCTGTTGT ACAACAGGGTTCATCACAATGGTC
NB76 ATGCTTGTTACATCAACCCTGGAC GTCCAGGGTTGATGTAACAAGCAT
NB77 CGACCTGTTTCTCAGGGATACAAC GTTGTATCCCTGAGAAACAGGTCG
NB78 AACAACCGAACCTTTGAATCAGAA TTCTGATTCAAAGGTTCGGTTGTT
NB79 TCTCGGAGATAGTTCTCACTGCTG CAGCAGTGAGAACTATCTCCGAGA
NB80 CGGATGAACATAGGATAGCGATTC GAATCGCTATCCTATGTTCATCCG
NB81 CCTCATCTTGTGAAGTTGTTTCGG CCGAAACAACTTCACAAGATGAGG
NB82 ACGGTATGTCGAGTTCCAGGACTA TAGTCCTGGAACTCGACATACCGT
NB83 TGGCTTGATCTAGGTAAGGTCGAA TTCGACCTTACCTAGATCAAGCCA
NB84 GTAGTGGACCTAGAACCTGTGCCA TGGCACAGGTTCTAGGTCCACTAC
NB85 AACGGAGGAGTTAGTTGGATGATC GATCATCCAACTAACTCCTCCGTT
NB86 AGGTGATCCCAACAAGCGTAAGTA TACTTACGCTTGTTGGGATCACCT
NB87 TACATGCTCCTGTTGTTAGGGAGG CCTCCCTAACAACAGGAGCATGTA
NB88 TCTTCTACTACCGATCCGAAGCAG CTGCTTCGGATCGGTAGTAGAAGA
NB89 ACAGCATCAATGTTTGGCTAGTTG CAACTAGCCAAACATTGATGCTGT
NB90 GATGTAGAGGGTACGGTTTGAGGC GCCTCAAACCGTACCCTCTACATC
NB91 GGCTCCATAGGAACTCACGCTACT AGTAGCGTGAGTTCCTATGGAGCC
NB92 TTGTGAGTGGAAAGATACAGGACC GGTCCTGTATCTTTCCACTCACAA
NB93 AGTTTCCATCACTTCAGACTTGGG CCCAAGTCTGAAGTGATGGAAACT
NB94 GATTGTCCTCAAACTGCCACCTAC GTAGGTGGCAGTTTGAGGACAATC
NB95 CCTGTCTGGAAGAAGAATGGACTT AAGTCCATTCTTCTTCCAGACAGG
NB96 CTGAACGGTCATAGAGTCCACCAT ATGGTGGACTCTATGACCGTTCAG

3. DNA repair and end-prep

Materials
  • 1000 ng gDNA per sample
  • AMPure XP Beads (AXP)
Consumables
  • NEBNext FFPE DNA Repair Mix (NEB, M6630)
  • NEBNext® Ultra II End Repair / dA-tailing Module (NEB, E7546)
  • Nuclease-free water (e.g. ThermoFisher, AM9937)
  • Freshly prepared 80% ethanol in nuclease-free water
  • 0.2 ml thin-walled PCR tubes
  • 1.5 ml Eppendorf DNA LoBind tubes
  • Qubit dsDNA HS Assay Kit (Invitrogen, Q32851)
  • Qubit™ Assay Tubes (Invitrogen, Q32856)
Equipment
  • P1000 pipette and tips
  • P100 pipette and tips
  • P10 pipette and tips
  • Thermal cycler
  • Ice bucket with ice
  • Microfuge
  • Hula mixer (gentle rotator mixer)
  • Magnetic rack
  • Qubit fluorometer (or equivalent)
IMPORTANT

Optional fragmentation and size selection

By default, the protocol contains no DNA fragmentation step, however in some cases it may be advantageous to fragment your sample. For example, when working with lower amounts of input gDNA (100 ng – 500 ng), fragmentation will increase the number of DNA molecules and therefore increase throughput. Instructions are available in the DNA Fragmentation section of Extraction methods.

Additionally, we offer several options for size-selecting your DNA sample to enrich for long fragments - instructions are available in the Size Selection section of Extraction methods.

Thaw the AMPure XP Beads (AXP) at room temperature and mix by vortexing. Keep the beads at room temperature.

Prepare the NEBNext FFPE DNA Repair Mix and NEBNext Ultra II End Repair / dA-tailing Module reagents in accordance with manufacturer’s instructions, and place on ice.

For optimal performance, NEB recommend the following:

  1. Thaw all reagents on ice.

  2. Flick and/or invert the reagent tubes to ensure they are well mixed.
    Note: Do not vortex the FFPE DNA Repair Mix or Ultra II End Prep Enzyme Mix.

  3. Always spin down tubes before opening for the first time each day.

  4. The Ultra II End Prep Buffer and FFPE DNA Repair Buffer may have a little precipitate. Allow the mixture to come to room temperature and pipette the buffer up and down several times to break up the precipitate, followed by vortexing the tube for 30 seconds to solubilise any precipitate.
    Note: It is important the buffers are mixed well by vortexing.

  5. The FFPE DNA Repair Buffer may have a yellow tinge and is fine to use if yellow.

IMPORTANT

Do not vortex the NEBNext FFPE DNA Repair Mix or NEBNext Ultra II End Prep Enzyme Mix.

In clean 0.2 ml thin-walled PCR tubes, aliquot 1000 ng per sample.

Make up each sample to 12 µl using nuclease-free water. Mix gently by pipetting and spin down.

Combine the following components per sample:

Between each addition, pipette mix 10 - 20 times.

Reagent Volume
DNA sample 12 µl
NEBNext FFPE DNA Repair Buffer 0.875 µl
Ultra II End-prep reaction buffer 0.875 µl
Ultra II End-prep enzyme mix 0.75 µl
NEBNext FFPE DNA Repair Mix 0.50 µl
Total 15 µl
TIP

When processing increased numbers of samples, we recommend making up a mastermix of the reagents for the total number of samples and adding 3 µl to each individual sample.

Ensure the components are thoroughly mixed by pipetting and spin down briefly.

Using a thermal cycler, incubate at 20°C for 5 minutes and 65°C for 5 minutes.

Transfer each sample to clean 1.5 ml Eppendorf DNA LoBind tube.

Resuspend the AMPure XP beads (AXP) by vortexing.

Add 15 µl of resuspended AMPure XP Beads (AXP) to each end-prep reaction and mix by flicking the tube.

Incubate on a Hula mixer (rotator mixer) for 5 minutes at room temperature.

Prepare 500 μl of 80% ethanol in nuclease-free water per sample.

Spin down the samples and pellet the beads on a magnet until the eluate is clear and colourless. Keep the tubes on the magnet and pipette off the supernatant.

Keep the tubes on the magnet and wash the beads with 200 µl of freshly prepared 80% ethanol without disturbing the pellet. Remove the ethanol using a pipette and discard.

If the pellet was disturbed, wait for beads to pellet again before removing the ethanol.

Repeat the previous step.

Briefly spin down and place the tubes back on the magnet. Pipette off any residual ethanol. Allow to dry for 30 seconds, but do not dry the pellet to the point of cracking.

Remove the tubes from the magnetic rack and resuspend the pellet in 10 µl nuclease-free water. Spin down and incubate for 2 minutes at room temperature.

Pellet the beads on a magnet until the eluate is clear and colourless.

Remove and retain 10 µl of eluate for each sample into clean 1.5 ml Eppendorf DNA LoBind tubes, individually.

Note: If users are having difficulty retaining 10 µl without disturbing the beads, 8.5 µl can be retained instead, allowing 1 µl for quantification and 7.5 µl to be taken forward into the Native Barcode Ligation step.

CHECKPOINT

Quantify 1 µl of each eluted sample using a Qubit fluorometer.

Keeping your samples separate, sandardise them to an equimolar mass.

Make up the volume of each sample to 7.5 µl using nuclease-free water.

END OF STEP

Take forward the equimolar samples in 7.5 µl to be barcoded and pooled in the native barcode ligation step. However, at this point it is also possible to store the sample at 4°C overnight.

4. Native barcode ligation

Materials
  • Native Barcodes (NB01-NB96)
  • EDTA (EDTA)
  • AMPure XP Beads (AXP)
Consumables
  • Nuclease-free water (e.g. ThermoFisher, cat # AM9937)
  • Freshly prepared 80% ethanol in nuclease-free water
  • NEB Blunt/TA Ligase Master Mix (NEB, M0367)
  • 1.5 ml Eppendorf DNA LoBind tubes
  • Qubit dsDNA HS Assay Kit (Invitrogen, Q32851)
  • Qubit™ Assay Tubes (Invitrogen, Q32856)
Equipment
  • Magnetic rack
  • Vortex mixer
  • Hula mixer (gentle rotator mixer)
  • Microfuge
  • Thermal cycler
  • Ice bucket with ice
  • P1000 pipette and tips
  • P100 pipette and tips
  • P10 pipette and tips
Optional equipment
  • Qubit fluorometer (or equivalent for QC check)

Prepare the NEB Blunt/TA Ligase Master Mix according to the manufacturer's instructions, and place on ice:

  1. Thaw the reagents at room temperature.

  2. Spin down the reagent tubes for 5 seconds.

  3. Ensure the reagents are fully mixed by performing 10 full volume pipette mixes.

Thaw the EDTA at room temperature and mix by vortexing. Then spin down and place on ice.

Thaw the native barcodes at room temperature. Use one barcode per sample. Individually mix the barcodes by pipetting, spin down, and place them on ice.

Select a unique barcode for each sample to be run in a group:

  • For two samples on one flow cell, select two unique barcodes, one for each sample.
  • For three samples on two flow cells, select three unique barcodes, one for each sample.

In clean 1.5 ml Eppendorf DNA LoBind tubes, add the reagents in the following order per sample:

Reagent Volume
End-prepped DNA 7.5 µl
Native barcode 2.5 µl
Blunt/TA Ligase Master Mix 10 µl
Total 20 µl

Thoroughly mix the reaction by gently pipetting and briefly spinning down.

Incubate for 20 minutes at room temperature.

Add 4 µl of EDTA to each tube and mix thoroughly by pipetting and spin down briefly.

Note: EDTA is added at this step to stop the reaction.

Pool each group of two or three uniquely barcoded samples in a clean 1.5 ml Eppendorf DNA LoBind tube.

For example:

  • Up to 48 pools of two differentially barcoded samples
  • Up to 32 pools of three differentially barcoded samples

Ensure the beads are at room temperature and resuspend the AMPure XP beads (AXP) by vortexing.

Add AMPure XP Beads (AXP) to the pooled reaction in a 0.4X ratio and mix by pipetting. The volume for AMPure XP Beads (AXP) will vary depending on the number of barcoded samples in the pool:

  • For two barcoded samples add 19 µl of AMPure XP Beads (AXP)
  • For three barcoded samples add 29 µl of AMPure XP Beads (AXP)

Incubate on a Hula mixer (rotator mixer) for 10 minutes at room temperature.

Prepare 1 ml of fresh 80% ethanol in nuclease-free water per barcoded sample pool.

Spin down the sample for 5 seconds and pellet on a magnet for 5 minutes. Keep the tube on the magnetic rack until the eluate is clear and colourless, and pipette off the supernatant.

Keep the tube on the magentic rack and wash the beads with 200 µl of freshly prepared 80% ethanol without disturbing the pellet. Remove the ethanol using a pipette and discard.

Repeat the previous step.

Spin down and place the tube back on the magnetic rack. Pipette off any residual ethanol. Allow the pellet to dry for ~30 seconds, but do not dry the pellet to the point of cracking.

Remove the tube from the magnetic rack and resuspend the pellet in 35 µl nuclease-free water by gently flicking.

Incubate for 10 minutes at 37°C. Every 2 minutes, agitate the sample by gently flicking for 10 seconds to encourage DNA elution.

Spin down the tube for 5 seconds and pellet the beads on a magnetic rack until the eluate is clear and colourless.

Remove and retain 35 µl of eluate into a clean 1.5 ml Eppendorf DNA LoBind tube.

CHECKPOINT

Quantify 1 µl of eluted sample using a Qubit fluorometer.

END OF STEP

Take forward the barcoded DNA library to the adapter ligation and clean-up step. However, you may store the sample at 4°C overnight.

5. Adapter ligation and clean-up

Materials
  • Native Adapter (NA)
  • Long Fragment Buffer (LFB)
  • Elution Buffer (EB)
  • AMPure XP Beads (AXP)
Consumables
  • NEBNext® Quick Ligation Module (NEB, E6056)
  • 1.5 ml Eppendorf DNA LoBind tubes
  • Qubit™ Assay Tubes (Invitrogen, Q32856)
  • Qubit dsDNA HS Assay Kit (ThermoFisher, cat # Q32851)
Equipment
  • Microfuge
  • Magnetic rack
  • Vortex mixer
  • Hula mixer (gentle rotator mixer)
  • Thermal cycler
  • P1000 pipette and tips
  • P200 pipette and tips
  • P100 pipette and tips
  • P20 pipette and tips
  • P10 pipette and tips
  • Ice bucket with ice
  • Qubit fluorometer (or equivalent for QC check)
IMPORTANT

The Native Adapter (NA) used in this kit and protocol is not interchangeable with other sequencing adapters.

Prepare the NEBNext Quick Ligation Reaction Module according to the manufacturer's instructions, and place on ice:

  1. Thaw the reagents at room temperature.

  2. Spin down the reagent tubes for 5 seconds.

  3. Ensure the reagents are fully mixed by performing 10 full volume pipette mixes. Note: Do NOT vortex the Quick T4 DNA Ligase.

The NEBNext Quick Ligation Reaction Buffer (5x) may have a little precipitate. Allow the mixture to come to room temperature and pipette the buffer up and down several times to break up the precipitate, followed by vortexing the tube for several seconds to ensure the reagent is thoroughly mixed.

IMPORTANT

Do not vortex the Quick T4 DNA Ligase.

Spin down the Native Adapter (NA) and Quick T4 DNA Ligase, pipette mix and place on ice.

Thaw the Elution Buffer (EB) at room temperature and mix by vortexing. Then spin down and place on ice.

To enrich for DNA fragments of 3 kb or longer, thaw one tube of Long Fragment Buffer (LFB) at room temperature, mix by vortexing, spin down and place on ice.

In a 1.5 ml Eppendorf LoBind tube, mix in the following order:

Between each addition, pipette mix 10 - 20 times.

Reagent Volume
Pooled barcoded sample 30 µl
Native Adapter (NA) 5 µl
NEBNext Quick Ligation Reaction Buffer (5X) 10 µl
Quick T4 DNA Ligase 5 µl
Total 50 µl

Thoroughly mix the reaction by gently pipetting and briefly spinning down.

Incubate the reaction for 10 minutes at room temperature.

IMPORTANT

The next clean-up step uses Long Fragment Buffer (LFB) rather than 80% ethanol to wash the beads. The use of ethanol will be detrimental to the sequencing reaction.

Resuspend the AMPure XP Beads (AXP) by vortexing.

Add 20 µl of resuspended AMPure XP Beads (AXP) to the reaction and mix by pipetting.

Incubate on a Hula mixer (rotator mixer) for 10 minutes at room temperature.

Spin down the sample and pellet on the magnetic rack. Keep the tube on the magnet and pipette off the supernatant.

Wash the beads by adding 125 μl Long Fragment Buffer (LFB). Flick the beads to resuspend, spin down, then return the tube to the magnetic rack and allow the beads to pellet. Remove the supernatant using a pipette and discard.

Repeat the previous step.

Spin down and place the tube back on the magnet. Pipette off any residual supernatant. Allow to dry for ~30 seconds, but do not dry the pellet to the point of cracking.

Remove the tube from the magnetic rack and resuspend pellet in 35 µl Elution Buffer (EB).

Spin down and incubate for 10 minutes at 37°C. Every 2 minutes, agitate the sample by gently flicking for 10 seconds to encourage DNA elution.

Pellet the beads on a magnet until the eluate is clear and colourless, for at least 1 minute.

Remove and retain 35 µl of eluate containing the DNA library into a clean 1.5 ml Eppendorf DNA LoBind tube.

Dispose of the pelleted beads

CHECKPOINT

Quantify 1 µl of eluted sample using a Qubit fluorometer.

Make up each library to 32 µl at 50 fmol, using Elution Buffer (EB).

  • For two samples on one flow cell, make one DNA library from your eluate.
  • For three samples on two flow cells, make two DNA libraries from your eluate.

Note: If there is insufficient DNA to obtain 50 fmol, take forward the full volume of eluate as your DNA library and load onto one flow cell.

IMPORTANT

Where possible, we recommend loading ~50 fmol of this final prepared library onto the R10.4.1 flow cell for our Multiplex Ligation Sequencing V14 protocol.

END OF STEP

The prepared library is used for loading into the flow cell. Store the library on ice or at 4°C until ready to load.

TIP

Library storage recommendations

We recommend storing libraries in Eppendorf DNA LoBind tubes at 4°C for short-term storage or repeated use, for example, re-loading flow cells between washes. For single use and long-term storage of more than 3 months, we recommend storing libraries at -80°C in Eppendorf DNA LoBind tubes.

OPTIONAL ACTION

If quantities allow, the library may be diluted in Elution Buffer (EB) for splitting across multiple flow cells.

Depending on how many flow cells the library will be split across, more Elution Buffer (EB) than what is supplied in the kit will be required.

6. Priming and loading multiple flow cells on a PromethION

Materials
  • Sequencing Buffer (SB)
  • Library Beads (LIB)
  • Library Solution (LIS)
  • Flow Cell Tether (FCT)
  • Flow Cell Flush (FCF)
Consumables
  • PromethION Flow Cell
  • 1.5 ml Eppendorf DNA LoBind tubes
  • 2 ml Eppendorf DNA LoBind tubes
Equipment
  • PromethION 2 Solo device
  • PromethION sequencing device
  • P1000 pipette and tips
  • P200 pipette and tips
  • P20 pipette and tips
IMPORTANT

This kit is only compatible with R10.4.1 flow cells (FLO-PRO114M).

Using the Library Solution

For most sequencing experiments, use the Library Beads (LIB) for loading your library onto the flow cell. However, for viscous libraries it may be difficult to load with the beads and may be appropriate to load using the Library Solution (LIS).

Thaw the Sequencing Buffer (SB), Library Beads (LIB) or Library Solution (LIS, if using), Flow Cell Tether (FCT) and Flow Cell Flush (FCF) at room temperature, before mixing by vortexing. Then spin down before storing on ice.

IMPORTANT

Scale up reagent volumes as needed.

Ensure to prepare enough reagents for the total number of flow cells being processed and to take into account extra volume required for pipetting errors.

TIP

Each vial provides enough reagent for the preparation of 12 samples. Thaw the appropriate number of vials of each reagent.

Prepare the flow cell priming mix in a suitable tube for the number of flow cells to flush. Once combined, mix well by briefly vortexing.

Reagents Volume per flow cell
Flow Cell Flush (FCF) 1,170 µl
Flow Cell Tether (FCT) 30 µl
Total volume 1,200 µl
IMPORTANT

After taking flow cells out of the fridge, wait 20 minutes before inserting the flow cell into the PromethION for the flow cell to come to room temperature. Condensation can form on the flow cell in humid environments. Inspect the gold connector pins on the top and underside of the flow cell for condensation and wipe off with a lint-free wipe if any is observed. Ensure the heat pad (black pad) is present on the underside of the flow cell.

For PromethION 2 Solo, load the flow cell(s) as follows:

  1. Place the flow cell flat on the metal plate.

  2. Slide the flow cell into the docking port until the gold pins or green board cannot be seen.

J2068 FC-into-P2-animation V5

For the PromethION 24/48, load the flow cell(s) into the docking ports:

  1. Line up the flow cell with the connector horizontally and vertically before smoothly inserting into position.
  2. Press down firmly onto the flow cell and ensure the latch engages and clicks into place.

Step 1a V3

Step 1B

IMPORTANT

Insertion of the flow cells at the wrong angle can cause damage to the pins on the PromethION and affect your sequencing results. If you find the pins on a PromethION position are damaged, please contact support@nanoporetech.com for assistance.

Screenshot 2021-04-08 at 12.08.37

If not already completed, perform a flow cell check on all flow cells.

Please refer to the Flow Cell Check protocol for further information.

Slide the inlet port cover clockwise to open.

Prom loading 2

IMPORTANT

Take care when drawing back buffer from the flow cell. Do not remove more than 20-30 µl, and make sure that the array of pores are covered by buffer at all times. Introducing air bubbles into the array can irreversibly damage pores.

After opening the inlet port, draw back a small volume to remove any air bubbles:

  1. Set a P1000 pipette tip to 200 µl.
  2. Insert the tip into the inlet port.
  3. Turn the wheel until the dial shows 220-230 µl, or until you see a small volume of buffer entering the pipette tip.

Step 3 v1

Load 500 µl of the priming mix into the flow cell via the inlet port, avoiding the introduction of air bubbles. Wait five minutes. During this time, prepare the library for loading using the next steps in the protocol.

Step 4 v1

Thoroughly mix the contents of the Library Beads (LIB) by pipetting.

IMPORTANT

The Library Beads (LIB) tube contains a suspension of beads. These beads settle very quickly. It is vital that they are mixed immediately before use.

We recommend using the Library Beads (LIB) for most sequencing experiments. However, the Library Solution (LIS) is available for more viscous libraries.

In a new 1.5 ml Eppendorf DNA LoBind tube, prepare the library for loading as follows:

Reagent Volume per flow cell
Sequencing Buffer (SB) 100 µl
Library Beads (LIB) thoroughly mixed before use, or Library Solution (LIS) 68 µl
DNA library 32 µl
Total 200 µl

Note: Library loading volume has been increased to improve array coverage.

OPTIONAL ACTION

The Multiplex Ligation Kit V14 XL is designed for users running multiple flow cells. When handling multiple DNA libraries, the Sequencing Buffer (SB) and Library Beads (LIB) can be combined in a master mix:

  1. Mix the Sequencing Buffer (SB) and Library Beads (LIB) as described above, scaling up the final volume for the appropriate number of samples and adding up to 20% excess of each reagent.
  2. Mix the master mix by pipetting immediately before adding to the DNA samples.
  3. Pipette 168 µl of the master mix into each DNA sample-containing tube.
  4. Mix the samples by pipetting.

Complete the flow cell priming by slowly loading 500 µl of the priming mix into the inlet port.

Step 5 v1

Mix the prepared library gently by pipetting up and down just prior to loading.

Load 200 µl of library into the inlet port using a P1000 pipette.

Step 6 v1

Close the valve to seal the inlet port and close the PromethION lid when ready.

Wait a minimum of 10 minutes after loading the flow cells onto the PromethION before initiating any experiments. This will help to increase the sequencing output.

Picture7

IMPORTANT

Install the light shield on your flow cell as soon as library has been loaded for optimal sequencing output.

We recommend leaving the light shield on the flow cell when library is loaded, including during any washing and reloading steps. The shield can be removed when the library has been removed from the flow cell.

If the light shield has been removed from the flow cell, install the light shield as follows:

  1. Align the inlet port cut out of the light shield with the inlet port cover on the flow cell. The leading edge of the light shield should sit above the flow cell ID.
  2. Firmly press the light shield around the inlet port cover. The inlet port clip will click into place underneath the inlet port cover.

J2264 - Light shield animation PromethION Flow Cell 8a FAW

J2264 - Light shield animation PromethION Flow Cell 8b FAW

For multiple flow cell washing, use the same experiment name and identifying sample IDs for all runs to enable all flow cells to be paused simultaneously.

Screenshot 2023-02-14 114901

7. Data acquisition and basecalling

Overview of nanopore data analysis

For a full overview of nanopore data analysis, which includes options for basecalling and post-basecalling analysis, please refer to the Data Analysis document.

How to start sequencing

The sequencing device control, data acquisition and real-time basecalling are carried out by the MinKNOW software. Please ensure MinKNOW is installed on your computer or device. There are multiple options for how to carry out sequencing:

1. Data acquisition and basecalling in real-time using MinKNOW on a computer

Follow the instructions in the MinKNOW protocol beginning from the "Starting a sequencing run" section until the end of the "Completing a MinKNOW run" section.

2. Data acquisition and basecalling in real-time using the GridION device

Follow the instructions in the GridION user manual.

3. Data acquisition and basecalling in real-time using the MinION Mk1C device

Follow the instructions in the MinION Mk1C user manual.

4. Data acquisition and basecalling in real-time using the PromethION device

Follow the instructions in the PromethION user manual or the PromethION 2 Solo user manual.

5. Data acquisition using MinKNOW on a computer and basecalling at a later time using MinKNOW

Follow the instructions in the MinKNOW protocol beginning from the "Starting a sequencing run" section until the end of the "Completing a MinKNOW run" section. When setting your experiment parameters, set the Basecalling tab to OFF. After the sequencing experiment has completed, follow the instructions in the Post-run analysis section of the MinKNOW protocol.

8. Downstream analysis

Post-basecalling analysis

There are several options for further analysing your basecalled data:

1. EPI2ME workflows

For in-depth data analysis, Oxford Nanopore Technologies offers a range of bioinformatics tutorials and workflows available in EPI2ME, which are available in the EPI2ME section of the Community. The platform provides a vehicle where workflows deposited in GitHub by our Research and Applications teams can be showcased with descriptive texts, functional bioinformatics code and example data.

2. Research analysis tools

Oxford Nanopore Technologies' Research division has created a number of analysis tools, that are available in the Oxford Nanopore GitHub repository. The tools are aimed at advanced users, and contain instructions for how to install and run the software. They are provided as-is, with minimal support.

3. Community-developed analysis tools

If a data analysis method for your research question is not provided in any of the resources above, please refer to the resource centre and search for bioinformatics tools for your application. Numerous members of the Nanopore Community have developed their own tools and pipelines for analysing nanopore sequencing data, most of which are available on GitHub. Please be aware that these tools are not supported by Oxford Nanopore Technologies, and are not guaranteed to be compatible with the latest chemistry/software configuration.

9. Flow cell reuse and returns

Materials
  • Flow Cell Wash Kit (EXP-WSH004)

After your sequencing experiment is complete, if you would like to reuse the flow cell, please follow the Flow Cell Wash Kit protocol and store the washed flow cell at 2-8°C.

The Flow Cell Wash Kit protocol is available on the Nanopore Community.

TIP

We recommend you to wash the flow cell as soon as possible after you stop the run. However, if this is not possible, leave the flow cell on the device and wash it the next day.

Alternatively, follow the returns procedure to flush out the flow cell ready to send back to Oxford Nanopore.

Instructions for returning flow cells can be found here.

Note: All flow cells must be flushed with deionised water before returning the product.

IMPORTANT

If you encounter issues or have questions about your sequencing experiment, please refer to the Troubleshooting Guide that can be found in the online version of this protocol.

10. Issues during DNA/RNA extraction and library preparation for Kit 14

Below is a list of the most commonly encountered issues, with some suggested causes and solutions.

We also have an FAQ section available on the Nanopore Community Support section.

If you have tried our suggested solutions and the issue still persists, please contact Technical Support via email (support@nanoporetech.com) or via LiveChat in the Nanopore Community.

Low sample quality

Observation Possible cause Comments and actions
Low DNA purity (Nanodrop reading for DNA OD 260/280 is <1.8 and OD 260/230 is <2.0–2.2) The DNA extraction method does not provide the required purity The effects of contaminants are shown in the Contaminants document. Please try an alternative extraction method that does not result in contaminant carryover.

Consider performing an additional SPRI clean-up step.
Low RNA integrity (RNA integrity number <9.5 RIN, or the rRNA band is shown as a smear on the gel) The RNA degraded during extraction Try a different RNA extraction method. For more info on RIN, please see the RNA Integrity Number document. Further information can be found in the DNA/RNA Handling page.
RNA has a shorter than expected fragment length The RNA degraded during extraction Try a different RNA extraction method. For more info on RIN, please see the RNA Integrity Number document. Further information can be found in the DNA/RNA Handling page.

We recommend working in an RNase-free environment, and to keep your lab equipment RNase-free when working with RNA.

Low DNA recovery after AMPure bead clean-up

Observation Possible cause Comments and actions
Low recovery DNA loss due to a lower than intended AMPure beads-to-sample ratio 1. AMPure beads settle quickly, so ensure they are well resuspended before adding them to the sample.

2. When the AMPure beads-to-sample ratio is lower than 0.4:1, DNA fragments of any size will be lost during the clean-up.
Low recovery DNA fragments are shorter than expected The lower the AMPure beads-to-sample ratio, the more stringent the selection against short fragments. Please always determine the input DNA length on an agarose gel (or other gel electrophoresis methods) and then calculate the appropriate amount of AMPure beads to use. SPRI cleanup
Low recovery after end-prep The wash step used ethanol <70% DNA will be eluted from the beads when using ethanol <70%. Make sure to use the correct percentage.

11. Issues during the sequencing run for Kit 14

Below is a list of the most commonly encountered issues, with some suggested causes and solutions.

We also have an FAQ section available on the Nanopore Community Support section.

If you have tried our suggested solutions and the issue still persists, please contact Technical Support via email (support@nanoporetech.com) or via LiveChat in the Nanopore Community.

Fewer pores at the start of sequencing than after Flow Cell Check

Observation Possible cause Comments and actions
MinKNOW reported a lower number of pores at the start of sequencing than the number reported by the Flow Cell Check An air bubble was introduced into the nanopore array After the Flow Cell Check it is essential to remove any air bubbles near the priming port before priming the flow cell. If not removed, the air bubble can travel to the nanopore array and irreversibly damage the nanopores that have been exposed to air. The best practice to prevent this from happening is demonstrated in this video.
MinKNOW reported a lower number of pores at the start of sequencing than the number reported by the Flow Cell Check The flow cell is not correctly inserted into the device Stop the sequencing run, remove the flow cell from the sequencing device and insert it again, checking that the flow cell is firmly seated in the device and that it has reached the target temperature. If applicable, try a different position on the device (GridION/PromethION).
MinKNOW reported a lower number of pores at the start of sequencing than the number reported by the Flow Cell Check Contaminations in the library damaged or blocked the pores The pore count during the Flow Cell Check is performed using the QC DNA molecules present in the flow cell storage buffer. At the start of sequencing, the library itself is used to estimate the number of active pores. Because of this, variability of about 10% in the number of pores is expected. A significantly lower pore count reported at the start of sequencing can be due to contaminants in the library that have damaged the membranes or blocked the pores. Alternative DNA/RNA extraction or purification methods may be needed to improve the purity of the input material. The effects of contaminants are shown in the Contaminants Know-how piece. Please try an alternative extraction method that does not result in contaminant carryover.

MinKNOW script failed

Observation Possible cause Comments and actions
MinKNOW shows "Script failed"
Restart the computer and then restart MinKNOW. If the issue persists, please collect the MinKNOW log files and contact Technical Support. If you do not have another sequencing device available, we recommend storing the flow cell and the loaded library at 4°C and contact Technical Support for further storage guidance.

Pore occupancy below 40%

Observation Possible cause Comments and actions
Pore occupancy <40% Not enough library was loaded on the flow cell 50 fmol of good quality library can be loaded on to a PromethION flow cell. Please quantify the library before loading and calculate mols using tools like the Promega Biomath Calculator, choosing "dsDNA: µg to pmol"
Pore occupancy close to 0 The Multiplex Ligation Kit was used, and ethanol was used instead of LFB at the wash step after sequencing adapter ligation Ethanol can denature the motor protein on the sequencing adapters. Make sure the LFB buffer was used after ligation of sequencing adapters.
Pore occupancy close to 0 No tether on the flow cell Tethers are adding during flow cell priming (FCT tube). Make sure FCT was added to FCF before priming.

Shorter than expected read length

Observation Possible cause Comments and actions
Shorter than expected read length Unwanted fragmentation of DNA sample Read length reflects input DNA fragment length. Input DNA can be fragmented during extraction and library prep.

1. Please review the Extraction Methods in the Nanopore Community for best practice for extraction.

2. Visualise the input DNA fragment length distribution on an agarose gel before proceeding to the library prep. DNA gel2 In the image above, Sample 1 is of high molecular weight, whereas Sample 2 has been fragmented.

3. During library prep, avoid pipetting and vortexing when mixing reagents. Flicking or inverting the tube is sufficient.

Large proportion of unavailable pores

Observation Possible cause Comments and actions
Large proportion of unavailable pores (shown as blue in the channels panel and pore activity plot)

image2022-3-25 10-43-25 The pore activity plot above shows an increasing proportion of "unavailable" pores over time.		 Contaminants are present in the sample Some contaminants can be cleared from the pores by the unblocking function built into MinKNOW. If this is successful, the pore status will change to "sequencing pore". If the portion of unavailable pores stays large or increases:

1. A nuclease flush using the Flow Cell Wash Kit (EXP-WSH004) can be performed, or
2. Run several cycles of PCR to try and dilute any contaminants that may be causing problems.

Large proportion of inactive pores

Observation Possible cause Comments and actions
Large proportion of inactive/unavailable pores (shown as light blue in the channels panel and pore activity plot. Pores or membranes are irreversibly damaged) Air bubbles have been introduced into the flow cell Air bubbles introduced through flow cell priming and library loading can irreversibly damage the pores. Watch the Priming and loading your flow cell video for best practice
Large proportion of inactive/unavailable pores Certain compounds co-purified with DNA Known compounds, include polysaccharides, typically associate with plant genomic DNA.

1. Please refer to the Plant leaf DNA extraction method.
2. Clean-up using the QIAGEN PowerClean Pro kit.
3. Perform a whole genome amplification with the original gDNA sample using the QIAGEN REPLI-g kit.
Large proportion of inactive/unavailable pores Contaminants are present in the sample The effects of contaminants are shown in the Contaminants Know-how piece. Please try an alternative extraction method that does not result in contaminant carryover.

Temperature fluctuation

Observation Possible cause Comments and actions
Temperature fluctuation The flow cell has lost contact with the device Check that there is a heat pad covering the metal plate on the back of the flow cell. Re-insert the flow cell and press it down to make sure the connector pins are firmly in contact with the device. If the problem persists, please contact Technical Services.

Failed to reach target temperature

Observation Possible cause Comments and actions
MinKNOW shows "Failed to reach target temperature" The instrument was placed in a location that is colder than normal room temperature, or a location with poor ventilation (which leads to the flow cells overheating) MinKNOW has a default timeframe for the flow cell to reach the target temperature. Once the timeframe is exceeded, an error message will appear and the sequencing experiment will continue. However, sequencing at an incorrect temperature may lead to a decrease in throughput and lower q-scores. Please adjust the location of the sequencing device to ensure that it is placed at room temperature with good ventilation, then re-start the process in MinKNOW. Please refer to this FAQ for more information on MinION temperature control.

Last updated: 9/30/2024

Document options

PromethION