Problem |
Possible Cause |
Solution |
Step 3.3) Cannot form GΩ seal |
Surface of cell is not clean enough |
Clean further using positive pressure |
Step 3.3) Cell appears to deflate/die |
|
Prepare new pipette and target a new cell |
Step 3.4) Cannot determine terminal location of dendrites |
Alexafluor has not had enough time to diffuse throughout cell or concentration of Alexafluor is not high enough |
Check to make sure gain and exposure time on camera are high enough. Wait an additional 5 min before visualizing dendrites. If dendrites still are not visible, prepare solution with higher Alexafluor concentration. |
Step 4.1) Unable to aspirate all of cytoplasm |
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Step 5.5) Supernatant is not clear after 8 minutes |
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Gently pipette entire solution twice, while still on magnetic separator, and let sit for another 5 min |
Step 5.5) Pellet disperses during pipetting |
Sample is too far from magnet |
Keep tubes on magnetic separating device during all pipetting. Expel solution and allow beads to re-pellet for 5 min |
Step 5.7) After 5 min, samples still appear glossy |
Maximum amount of EtOH has not been removed |
Continue to monitor samples during drying. Every 2 min, use a P10 pipette and remove all EtOH at bottom of tube |
Step 8.9) Pellet had cracks before rehydration |
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Allow sample to rehydrate for a total of 4 min, rather than 2 (Step 8.10) |
Step 8.11) Small amount of bead was brought up with supernatant |
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Eject entire sample back into tube and place on magnetic separator for 1 min; Pipet up gently and make sure to avoid pellet |
Step 8.12) DNA smears are inconsistent and fluorescence scale continuously changes |
Too high DNA concentration for a HS chip |
Check concentration of sample and dilute between 1 - 10 ng/µL. Rerun bioanalyzer |
Step 8.12) Low molecular weight smear |
RNA Degradation |
Make sure to flash freeze cell immediately after collection. Discard this cDNA library |
Step 8.12) Fluctuating marker baseline in control lane |
Contamination or old reagent |
Discard DNA marker and employ new tube for Bioanalyzer run |
Step 8.12) No DNA smear |
Failure to expel cell |
Pull new needles with a slightly larger tip |
|
RNA Bead Failure |
Make sure beads have been fully resuspended before use and allow samples to incubate before placing on magnetic separator |
Step 8.12) Weak DNA smear |
Not enough amplification |
Employ more PCR cycles |
Step 8.12) DNA smear outside of 500bp-2Kb range |
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DNA smears below 0.5 and above 2 Kb are likely contamination. Discard sample |
Step 8.12) Regularly spaced spikes on DNA trace |
Contamination of sample |
Always wear fresh gloves and make new ethanol for rinses; filter tips should be used at all times |
Step 9.3) Unable to detect concentration of sample on fluorometer |
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Samples below detection level have too little DNA for tagmentation and cannot be used |
Step 10.10) Samples are not dry after 10 min |
Continue to remove excess EtOH |
Allow samples to airdry longer, check on them every minutes |
Step 10.13) Smear skewed toward 2Kb |
Incomplete fragmentation |
Re-dilute sample to a concentration of 0.15 ng/µL, rather than 0.2 ng/µL; rerun tagmentation |
Step 10.13) Smear skewed toward 200bp |
Too little DNA input |
Dilute sample less, try a concentration of 0.4 ng/µL; rerun tagmentation |
|
Tagmentation reaction too long |
Reduce reaction time of tagmentation to 8 min |
Step 10.13) Weak smears |
Improper Amplification of DNA |
Dilute sample to concentration of 0.4 ng/µL and rerun tagmentation |
Step 11.2) Maximum obtainable pool concentration is below 5 nM |
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Identify which sample(s) have significantly low concentrations and rerun tagmentation with new dilution |