We can get the mass of live cells by quantitative phase imaging, but we would also like to know the mass of total DNA within these cells. We wonder how reliable Hoechst 33342 labeling is on total DNA, since it only labels contiguous A-T base pairs. Can we use quantitative phase imaging to determine the total DNA mass in mammalian cells? If so, what is the best way to do so? If not, what other methods do you suggest?
Julien,
That mass would actual depend on the cytogenetic status, i.e. ploidity, of the cell or line. This status may even vary with prolonged culture time and is therefore quite inconsistently reported in the literature for most lines. However, on average, that may not matter a lot to you. Human lines, like your HT1080 fibrosarcoma cells or esp. the HeLa adenocarcinoma cells, are often hyperploid. If you know the number of base pairs in the genome (e.g. COS-7 = monkey!) of your cell of interest, which is about 3 billion in the haploid human genome, you may calculate as follows: 3x10^9 bp x 2 (diploid) x 660 (AVGed MW of 1 bp) x 1.67x10^-12pg ("weight in dalton") = 6.6pg/ diploid primary cell. Without having own experiences with Hoechst 33342, you may test this empirically by using single cells from the different lines with different ploidities. Hope this helps. Good luck!
Absolutly not my working field, but look here: http://www.ncbi.nlm.nih.gov/pubmed/16942746
Julien,
That mass would actual depend on the cytogenetic status, i.e. ploidity, of the cell or line. This status may even vary with prolonged culture time and is therefore quite inconsistently reported in the literature for most lines. However, on average, that may not matter a lot to you. Human lines, like your HT1080 fibrosarcoma cells or esp. the HeLa adenocarcinoma cells, are often hyperploid. If you know the number of base pairs in the genome (e.g. COS-7 = monkey!) of your cell of interest, which is about 3 billion in the haploid human genome, you may calculate as follows: 3x10^9 bp x 2 (diploid) x 660 (AVGed MW of 1 bp) x 1.67x10^-12pg ("weight in dalton") = 6.6pg/ diploid primary cell. Without having own experiences with Hoechst 33342, you may test this empirically by using single cells from the different lines with different ploidities. Hope this helps. Good luck!
Julien,
I fully agree with Holger Jahr. In addition cell lines will give you a lot of problems due to duplications, etc. You may check in primary lymphocytes. I believe that Hoechst 33342 will work, otherwise you can use DAPI
As far as I know, a rough estimation is about 6 picograms of DNA for a human cell.
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