Tagmentation failure on fresh PBMC
Hi everyone, I've been following the Omni-ATAC-Seq assay and have 4 failed attempts to generate sample. 
I've started on freshly isolated PBMCs (50k, 100k, 100k) then dropped down to 50, 20, 10k. I began to think it was, perhaps my lysis buffer so I ran a DAPI nuclear stain to QC and it looked fine then proceeded to continue to transposition portion, heat at 37 degrees for 30 minutes.
I then purified what remained using the Qiagen MinElute kit as described in the kit and ran QC on the bioanalyser and my samples were undertagmented.
Could I be prepping the sample incorrectly? Prior to lysing, I do see a faint pellet, however after lysing, I do not see anything (difficult with just cell nuclear contents).
However I'm worried I'm aspirating the contents.
Has anyone ran ATAC-Seq on PBMCs and what cell concentration do you use?
Any other thoughts?
Stumped
I've started on freshly isolated PBMCs (50k, 100k, 100k) then dropped down to 50, 20, 10k. I began to think it was, perhaps my lysis buffer so I ran a DAPI nuclear stain to QC and it looked fine then proceeded to continue to transposition portion, heat at 37 degrees for 30 minutes.
I then purified what remained using the Qiagen MinElute kit as described in the kit and ran QC on the bioanalyser and my samples were undertagmented.
Could I be prepping the sample incorrectly? Prior to lysing, I do see a faint pellet, however after lysing, I do not see anything (difficult with just cell nuclear contents).
However I'm worried I'm aspirating the contents.
Has anyone ran ATAC-Seq on PBMCs and what cell concentration do you use?
Any other thoughts?
Stumped