Ligation sequencing amplicons (SQK-LSK110)

Version for device: Flongle

Other available device versions: MinION

1. Important This is a Legacy product

   This kit is soon to be discontinued and we recommend all customers to upgrade to the latest chemistry for their relevant kit which is available on the Store. If customers require further support for any ongoing critical experiments using a Legacy product, please contact Customer Support via email: support@nanoporetech.com. For further information on please see the product update page.

2. Ligation Sequencing Kit features

   This kit is recommended for users who:

   • want to optimise their sequencing experiment for throughput
   • would like to utilise upstream processes such as size selection, whole genome amplification, or enrichment for long reads
3. Introduction to the Ligation Sequencing protocol for amplicons

   This protocol describes how to carry out sequencing of an amplicon sample using the Ligation Sequencing Kit (SQK-LSK110). It is highly recommended that a Lambda control experiment is completed first to become familiar with the technology.

   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

   You will need to:
   - Amplify your DNA sample
   - Repair the DNA, and prepare the DNA ends for adapter attachment
   - Attach sequencing adapters supplied in the kit to the DNA ends
   - Prime the flow cell, and load your DNA library into the flow cell

   

   Sequencing and analysis

   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
   - Start the EPI2ME software and select a workflow for further analysis (this step is optional)

4. Important Compatibility of this protocol

   This protocol should only be used in combination with:

   • Ligation Sequencing Kit (SQK-LSK110)
   • Flongle Sequencing Expansion (EXP-FSE001)
   • Control Expansion (EXP-CTL001)
   • Flongle Flow Cell R9.4.1 (FLO-FLG001)

1. Important Flongle Sequencing Expansion

   There are three buffers that come into direct contact with a flow cell at the point of loading (Sequencing Buffer, Flush Buffer/Flow Cell Flush, and Loading Beads/Library Beads or Loading Solution/Library Solution). We have found that there is a very low level of contaminants seeping out of the plastic vials that contain these buffers, and this impacts the robustness of the Flongle flow cell system (MinION and PromethION are not impacted by this).

   

   To rapidly deploy this to Flongle users, we have produced a Flongle Sequencing Expansion (EXP-FSE001 and EXP-FSE002), which can perform 12 Flongle flow cell loads in total. The buffers in the Flongle Sequencing Expansion are shipped in glass vials to avoid the contaminant seeping issue. It is important to use these buffers when using Flongle Flow Cells.

   To load a library onto your Flongle flow cell, you will need to use the following components:

   Flongle Sequencing Expansion (EXP-FSE001) components

   • Sequencing Buffer II (SBII)
   • Flush Buffer (FB)
   • Loading Beads II (LBII) or Loading Solution (LS)

   Sequencing or Flow Cell Priming Kit components

   • Flush Tether (FLT)

   Flongle Sequencing Expansion (EXP-FSE002) components for Kit 14

   • Sequencing Buffer (SB)
   • Flow Cell Flush (FCF)
   • Library Beads (LIB)
   • Library Solution (LIS)

   Oxford Nanopore Technologies deem the useful life of the Flongle Flow Cell Priming Kit to be 6 months from receipt by the customer.

2. For this protocol, you will need 50-100 fmol amplicon DNA.
3. 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.

4. NEBNext® Companion Module for Oxford Nanopore Technologies® Ligation Sequencing

   For customers new to nanopore sequencing, we recommend buying the NEBNext® Companion Module for Oxford Nanopore Technologies® Ligation Sequencing (catalogue number E7180S or E7180L), which contains all the NEB reagents needed for use with the Ligation Sequencing Kit.

   Please note, for our amplicon protocols, NEBNext FFPE DNA Repair Mix and NEBNext FFPE DNA Repair Buffer are not required.

5. Ligation Sequencing Kit (SQK-LSK110) contents

   

   Name	Acronym	Cap colour	No. of vials	Fill volume per vial (µl)
   DNA CS	DCS	Yellow	1	35
   Adapter Mix F	AMX-F	Green	1	40
   Ligation Buffer	LNB	Clear	1	200
   L Fragment Buffer	LFB	White cap, orange stripe on label	2	1,800
   S Fragment Buffer	SFB	Grey	2	1,800
   Sequencing Buffer II	SBII	Red	1	500
   Elution Buffer	EB	Black	1	200
   Loading Beads II	LBII	Pink	1	360
   Loading Solution	LS	White cap, pink sticker on label	1	360
   Flush Buffer	FB	Blue	6	1,170
   Flush Tether	FLT	Purple	1	200

6. Flongle Sequencing Expansion (EXP-FSE001) contents

   

   Name	Acronym	Cap colour	Number of vials	Fill volume per vial (µl)
   Sequencing Buffer II	SBII	Blue	1	180
   Loading Beads II	LBII	Blue	1	120
   Loading Solution	LS	Blue	1	120
   Flush Buffer	FB	Blue	2	702

   Oxford Nanopore Technologies deem the useful life of the Flow Cell Expansion to be 6 months from receipt by the customer.

7. Important Please note that Oxford Nanopore Technologies deem the useful life of the Flongle Sequencing Expansion (EXP-FSE001) to be 6 months from receipt by the customer.

1. MinION Mk1B IT requirements

   Sequencing on a MinION Mk1B requires a high-spec computer or laptop to keep up with the rate of data acquisition. Read more in the MinION Mk1B IT Requirements document.

2. MinION Mk1C IT requirements

   The MinION Mk1C contains fully-integrated compute and screen, removing the need for any accessories to generate and analyse nanopore data. Read more in the MinION Mk1C IT requirements document.

3. Software for nanopore sequencing

   MinKNOW

   The MinKNOW software controls the nanopore sequencing device, collects sequencing data and basecalls in real time. You will be using MinKNOW for every sequencing experiment to sequence, basecall and demultiplex if your samples were barcoded.

   For instructions on how to run the MinKNOW software, please refer to the MinKNOW protocol.

   EPI2ME (optional)

   The EPI2ME cloud-based platform performs further analysis of basecalled data, for example alignment to the Lambda genome, barcoding, or taxonomic classification. You will use the EPI2ME platform only if you would like further analysis of your data post-basecalling.

   For instructions on how to create an EPI2ME account and install the EPI2ME Desktop Agent, please refer to the EPI2ME Platform protocol.

4. 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

1. Important Flongle Sequencing Expansion

   There are three buffers that come into direct contact with a flow cell at the point of loading (Sequencing Buffer, Flush Buffer/Flow Cell Flush, and Loading Beads/Library Beads or Loading Solution/Library Solution). We have found that there is a very low level of contaminants seeping out of the plastic vials that contain these buffers, and this impacts the robustness of the Flongle flow cell system (MinION and PromethION are not impacted by this).

   

   To rapidly deploy this to Flongle users, we have produced a Flongle Sequencing Expansion (EXP-FSE001 and EXP-FSE002), which can perform 12 Flongle flow cell loads in total. The buffers in the Flongle Sequencing Expansion are shipped in glass vials to avoid the contaminant seeping issue. It is important to use these buffers when using Flongle Flow Cells.

   To load a library onto your Flongle flow cell, you will need to use the following components:

   Flongle Sequencing Expansion (EXP-FSE001) components

   • Sequencing Buffer II (SBII)
   • Flush Buffer (FB)
   • Loading Beads II (LBII) or Loading Solution (LS)

   Sequencing or Flow Cell Priming Kit components

   • Flush Tether (FLT)

   Flongle Sequencing Expansion (EXP-FSE002) components for Kit 14

   • Sequencing Buffer (SB)
   • Flow Cell Flush (FCF)
   • Library Beads (LIB)
   • Library Solution (LIS)

   Oxford Nanopore Technologies deem the useful life of the Flongle Flow Cell Priming Kit to be 6 months from receipt by the customer.

2. Prepare the DNA in nuclease-free water
   • Transfer 50-100 fmol amplicon DNA into a 1.5 ml Eppendorf DNA LoBind tube
   • Adjust the volume to 24.5 μl with nuclease-free water
   • Mix thoroughly by flicking the tube to avoid unwanted shearing
   • Spin down briefly in a microfuge

3. Thaw DNA Control Sample (DCS) at room temperature, spin down, mix by pipetting, and place on ice.
4. Prepare the 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 reagent tube to ensure they are well mixed.
   3. Always spin down tubes before opening for the first time each day.
   4. The Ultra II End prep 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 several seconds to ensure the reagent is thoroughly mixed.

5. Important Do not vortex the NEBNext Ultra II End Prep Enzyme Mix.
6. Important It is important that the NEBNext Ultra II End Prep Reaction Buffer is mixed well by vortexing.

   Check for any visible precipitate; vortexing for at least 30 seconds may be required to solubilise all precipitate.

7. In a 0.2 ml thin-walled PCR tube, mix the following:

   Reagent	Volume
   DCS	0.5 µl
   DNA	24.5 µl
   Ultra II End-prep Reaction Buffer	3.5 µl
   Ultra II End-prep Enzyme Mix	1.5 µl
   Total	30 µl

8. Ensure the components are thoroughly mixed by pipetting, and spin down.
9. Using a thermal cycler, incubate at 20°C for 5 minutes and 65°C for 5 minutes.
10. Important AMPure XP bead clean-up

    It is recommended that the repaired/end-prepped DNA sample is subjected to the following clean-up with AMPure XP beads. This clean-up can be omitted for simplicity and to reduce library preparation time. However, it has been observed that omission of this clean-up can: reduce subsequent adapter ligation efficiency, increase the prevalence of chimeric reads, and lead to an increase in pores being unavailable for sequencing. If omitting the clean-up step, proceed to the next section.

11. Resuspend the AMPure XP beads by vortexing.
12. Transfer the DNA sample to a clean 1.5 ml Eppendorf DNA LoBind tube.
13. Add 30 µl of resuspended AMPure XP beads to the end-prep reaction and mix by flicking the tube.
14. Incubate on a Hula mixer (rotator mixer) for 5 minutes at room temperature.
15. Prepare 500 μl of fresh 70% ethanol in nuclease-free water.
16. Spin down the sample and pellet on a magnet until supernatant is clear and colourless. Keep the tube on the magnet, and pipette off the supernatant.
17. Keep the tube on the magnet and wash the beads with 200 µl of freshly prepared 70% ethanol without disturbing the pellet. Remove the ethanol using a pipette and discard.
18. Repeat the previous step.
19. Spin down and place the tube 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.
20. Remove the tube from the magnetic rack and resuspend the pellet in 31 µl nuclease-free water. Incubate for 2 minutes at room temperature.
21. Pellet the beads on a magnet until the eluate is clear and colourless, for at least 1 minute.
22. Remove and retain 31 µl of eluate into a clean 1.5 ml Eppendorf DNA LoBind tube.
23. Quantify 1 µl of eluted sample using a Qubit fluorometer.
24. End of Step Take forward the repaired and end-prepped DNA into the adapter ligation step. However, at this point it is also possible to store the sample at 4°C overnight.

1. Important Although the recommended 3rd party ligase is supplied with its own buffer, the ligation efficiency of Adapter Mix F (AMX-F) is higher when using Ligation Buffer supplied within the Ligation Sequencing Kit.
2. Spin down the Adapter Mix F (AMX-F) and Quick T4 Ligase, and place on ice.
3. Thaw Ligation Buffer (LNB) at room temperature, spin down and mix by pipetting. Due to viscosity, vortexing this buffer is ineffective. Place on ice immediately after thawing and mixing.
4. Thaw the Elution Buffer (EB) at room temperature and mix by vortexing. Then spin down and place on ice.
5. Important Depending on the wash buffer (LFB or SFB) used, the clean-up step after adapter ligation is designed to either enrich for DNA fragments of >3 kb, or purify all fragments equally.
   • To enrich for DNA fragments of 3 kb or longer, use Long Fragment Buffer (LFB)
   • To retain DNA fragments of all sizes, use Short Fragment Buffer (SFB)
6. 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.
7. To retain DNA fragments of all sizes, thaw one tube of Short Fragment Buffer (SFB) at room temperature, mix by vortexing, spin down and place on ice.
8. In a 1.5 ml Eppendorf DNA LoBind tube, mix in the following order:

   Reagent	Volume
   DNA sample from the previous step	30 µl
   Ligation Buffer (LNB)	12.5 µl
   NEBNext Quick T4 DNA Ligase	5 µl
   Adapter Mix F (AMX-F)	2.5 µl
   Total	50 µl

9. Ensure the components are thoroughly mixed by pipetting, and spin down.
10. Incubate the reaction for 10 minutes at room temperature.
11. Important If you have omitted the AMPure purification step after DNA repair and end-prep, do not incubate the reaction for longer than 10 minutes.
12. Resuspend the AMPure XP beads by vortexing.
13. Add 20 µl of resuspended AMPure XP beads to the reaction and mix by flicking the tube.
14. Incubate on a Hula mixer (rotator mixer) for 5 minutes at room temperature.
15. Spin down the sample and pellet on a magnet. Keep the tube on the magnet, and pipette off the supernatant when clear and colourless.
16. Wash the beads by adding either 125 μl Long Fragment Buffer (LFB) or 125 μl Short Fragment Buffer (SFB). Flick the beads to resuspend, then return the tube to the magnetic rack and allow the beads to pellet. Remove the supernatant using a pipette and discard.
17. Repeat the previous step.
18. 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.
19. Remove the tube from the magnetic rack and resuspend pellet in 7 µl Elution Buffer (EB). Incubate for 10 minutes at room temperature. For high molecular weight DNA, incubating at 37° C can improve the recovery of long fragments.
20. Pellet the beads on a magnet until the eluate is clear and colourless, for at least 1 minute.
21. Remove and retain 7 µl of eluate containing the DNA library into a clean 1.5 ml Eppendorf DNA LoBind tube.

    Dispose of the pelleted beads

22. Quantify 1 µl of eluted sample using a Qubit fluorometer.
23. 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.
24. Important Following standard input recommendations, the protocol should produce enough final library (adapted DNA in EB) to load at least two Flongle flow cells. We recommend reserving enough library to load a second Flongle flow cell. We recommend loading 3-20 fmol of this final prepared library onto the flow cell. Loading more than 20 fmol can have a detrimental effect on throughput. Dilute the library in EB or nuclease-free water up to a final volume of 5 μl.
25. 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, reloading 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.
    For further information, please refer to the DNA library stability Know-How document.

26. Optional Action

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

    Additional buffer for doing this can be found in the Sequencing Auxiliary Vials expansion (EXP-AUX002), available to purchase separately. This expansion also contains additional vials of Sequencing Buffer II (SBII) and Loading Beads II (LBII), required for loading the libraries onto flow cells.

1. Important Flongle Sequencing Expansion

   There are three buffers that come into direct contact with a flow cell at the point of loading (Sequencing Buffer, Flush Buffer/Flow Cell Flush, and Loading Beads/Library Beads or Loading Solution/Library Solution). We have found that there is a very low level of contaminants seeping out of the plastic vials that contain these buffers, and this impacts the robustness of the Flongle flow cell system (MinION and PromethION are not impacted by this).

   

   To rapidly deploy this to Flongle users, we have produced a Flongle Sequencing Expansion (EXP-FSE001 and EXP-FSE002), which can perform 12 Flongle flow cell loads in total. The buffers in the Flongle Sequencing Expansion are shipped in glass vials to avoid the contaminant seeping issue. It is important to use these buffers when using Flongle Flow Cells.

   To load a library onto your Flongle flow cell, you will need to use the following components:

   Flongle Sequencing Expansion (EXP-FSE001) components

   • Sequencing Buffer II (SBII)
   • Flush Buffer (FB)
   • Loading Beads II (LBII) or Loading Solution (LS)

   Sequencing or Flow Cell Priming Kit components

   • Flush Tether (FLT)

   Flongle Sequencing Expansion (EXP-FSE002) components for Kit 14

   • Sequencing Buffer (SB)
   • Flow Cell Flush (FCF)
   • Library Beads (LIB)
   • Library Solution (LIS)

   Oxford Nanopore Technologies deem the useful life of the Flongle Flow Cell Priming Kit to be 6 months from receipt by the customer.

2. Important Do NOT touch the reverse side of the Flongle flow cell array or the contact pads on the Flongle adapter. ALWAYS wear gloves when handling Flongle flow cells and adapters to avoid damage to the flow cell or adapter.

   

3. The diagram below shows the components of the Flongle flow cell:

   

   The seal tab, air vent, waste channel, drain port and sample port are visible here. The sample port, drain port and air vent only become accessible once the seal tab is peeled back.

4. Thaw the Sequencing Buffer II (SBII), Loading Beads II (LBII) and Flush Buffer (FB) from the Flongle Sequencing Expansion and Flush Tether (FLT) from the Ligation Sequencing Kit (SQK-LSK110) at room temperature.
5. Mix the Sequencing Buffer II (SBII), Flush Buffer (FB) and Flush Tether (FLT) tubes by vortexing and spin down at room temperature.
6. In a fresh 1.5 ml Eppendorf DNA LoBind tube, mix 117 µl of Flush Buffer (FB) with 3 µl of Flush Tether (FLT) and mix by pipetting.
7. Place the Flongle adapter into the MinION or one of the five GridION positions.

   The adapter should sit evenly and flat on the MinION Mk1B or GridION platform. This ensures the flow cell assembly is flat during the next stage.

8. Important The adapter needs to be plugged into your device, and the device should be plugged in and powered on before inserting the Flongle flow cell.

   

9. Place the flow cell into the Flongle adapter, and press the flow cell down until you hear a click.

   The flow cell should sit evenly and flat inside the adapter, to avoid any bubbles forming inside the fluidic compartments.

   

10. Important How to prime and load a Flongle flow cell

11. Peel back the seal tab from the Flongle flow cell, up to a point where the sample port is exposed, as follows:

    1. Lift up the seal tab:
       
       
       

    2. Pull the seal tab to open access to the sample port:
       
       
       

    3. Hold the seal tab open by using adhesive on the tab to stick to the MinION Mk 1B lid:
       

12. To prime your flow cell with the mix of Flush Buffer (FB) and Flush Tether (FLT) that was prepared earlier, ensure that there is no air gap in the sample port or the pipette tip. Place the P200 pipette tip inside the sample port and slowly dispense the priming fluid into the Flongle flow cell by slowly pipetting down. We also recommend twisting the pipette plunger down to avoid flushing the flow cell too vigorously.

    

13. Vortex the vial of Loading Beads II (LBII). Note that the beads settle quickly, so immediately prepare the Sequencing Mix in a fresh 1.5 ml Eppendorf DNA LoBind tube for loading the Flongle, as follows:

    Reagents	Volume
    Sequencing Buffer II (SBII)	15 µl
    Loading Beads II (LBII) mixed immediately before use, or Loading Solution (LS), if using. LS can be used instead of LBII when preparing libraries with the Ligation Sequencing Kit (SQK-LSK110)	10 µl
    DNA library	5 µl
    Total	30 µl

14. To add the Sequencing Mix to the flow cell, ensure that there is no air gap in the sample port or the pipette tip. Place the P200 tip inside the sample port and slowly dispense the Sequencing Mix into the flow cell by slowly pipetting down. We also recommend twisting the pipette plunger down to avoid flushing the flow cell too vigorously.

    

15. Seal the Flongle flow cell using the adhesive on the seal tab, as follows:

    1. Stick the transparent adhesive tape to the sample port.
       
       
       

    2. Replace the top (Wheel icon section) of the seal tab to its original position.
       

16. Replace the sequencing platform lid.

1. How to start sequencing

   Once you have loaded your flow cell, the sequencing run can be started on MinKNOW, our sequencing software that controls the device, data acquisition and real-time basecalling. For more detailed information on setting up and using MinKNOW, please see the MinKNOW protocol.

   MinKNOW can be used and set up to sequence in multiple ways:

   • On a computer either direcly or remotely connected to a sequencing device.
   • Directly on a GridION, MinION Mk1C or PromethION 24/48 sequencing device.

   For more information on using MinKNOW on a sequencing device, please see the device user manuals:

   • MinION Mk1C user manual
   • MinION Mk1B user manual
   • GridION user manual

   ---

   To start a sequencing run on MinKNOW:

   1. Navigate to the start page and click Start sequencing.
   

   2. Fill in your experiment details, such as name and flow cell position and sample ID.
   

   3. Select the sequencing kit used in the library preparation on the Kit page.
   

   4. Configure the sequencing parameters for your sequencing run or keep to the default settings on the Run options and Analysis tabs.

   Note: If basecalling was turned off when a sequencing run was set up, basecalling can be performed post-run on MinKNOW. For more information, please see the MinKNOW protocol.

   5. On the Output page, set up the output parameters or keep to the default settings.
   

   6. Click Start on the Review page to start the sequencing run.
   

2. Data analysis after sequencing

   After sequencing and basecalling, the data can be analysed. For further information about options for basecalling and post-basecalling analysis, please refer to the Data Analysis document.

   In the Downstream analysis section, we outline further options for analysing your data.

1. 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. 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, which 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.

1. 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.

2. 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.

3. 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.
   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.

1. 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.

2. 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.

3. 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.

4. Pore occupancy below 40%

   Observation	Possible cause	Comments and actions
   Pore occupancy <40%	Not enough library was loaded on the flow cell	Ensure the correct volume and concentration as stated on the appropriate protocol for your sequencing library is loaded onto the flow cell. Please quantify the library before loading and calculate fmols using tools like the Promega Biomath Calculator, choosing "dsDNA: µg to fmol"
   Pore occupancy close to 0	The Ligation Sequencing Kit was used, and sequencing adapters did not ligate to the DNA	Make sure to use the NEBNext Quick Ligation Module (E6056) and Oxford Nanopore Technologies Ligation Buffer (LNB, provided in the sequencing kit) at the sequencing adapter ligation step, and use the correct amount of each reagent. A Lambda control library can be prepared to test the integrity of the third-party reagents.
   Pore occupancy close to 0	The Ligation Sequencing Kit was used, and ethanol was used instead of LFB or SFB at the wash step after sequencing adapter ligation	Ethanol can denature the motor protein on the sequencing adapters. Make sure the LFB or SFB 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 (FLT tube for Kit 9, 10, 11, FCT for Kit 14, and FTU for ultra-long DNA kits). Make sure FLT/FCT/FTU was added to the buffer (FB for Kit 9, 10, 11, and FCF for Kit 14) before priming.

5. 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. 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.

6. 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) 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.

7. 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.

8. 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.

9. 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.