DNA extraction

I have been moving forward with extraction of DNA from P. astreoides samples using the Qiagen DNeasy kit. On Monday/Tuesday I did 16 samples, then another 10 samples (actually 9; one was divided in two). For the first set of 16, I did an overnight lysis (6pm to 9am) with no homogenization. Most of the tissue was very loose and easily scraped off the skeleton or scooped from the bottom of the tube. My initial results (see previous post) suggested that larger quantities of tissue were more successful, so I was fairly generous with tissue quantity. I did two 200 ul elutions into two separate tubes. I measured DNA quantity in the first elution with the Qubit HS assay. Here are the results (again, for the first elution only):

Sample # Qubit conc. (ng/ul) Sample volume Total DNA quantity (ng)
15 5.92 200 1184
16 3.46 200 692
96 6.82 200 1364
19 5.4 200 1080
14 3.92 200 784
82 7.38 200 1476
98 7.92 200 1584
13 10.4 200 2080
12 3.1 200 620
18 5.88 200 1176
99 5.16 200 1032
17 10 200 2000
95 5.88 200 1176
11 10.4 200 2080
80 10.8 200 2160
81 8.82 200 1764

 

For the next set of 10 samples, I did a few things differently. Again, I tried to be generous with tissue quantity. For a few samples, the tissue volume of the pellet was nearly 100 ul. I ranked the tissue quantity on a scale of 1 to 10, 1 being the lowest. I also ranked the sample color after the lysis period to get a second qualitative measure of tissue quantity. I homogenized three of the most dense samples lightly with a plastic pestle (86, 90, 83). The lysis period was from 4:30pm to 9:30am. The lysis did not appear complete, so for the last hour of lysis, I added an additional 180 ul of buffer and 40 ul of proteinase K, and disrupted a few of the most dense samples by pipetting. Sam suggested elution with 50 ul instead of 200 ul, and reusing the original eluate for the second elution. I quantitated the DNA with both Nanodrop and Qubit for comparison. Here are the results:

Past_Dneasy2

Sample # Tissue quantity rank (1 = low) Color rank after lysis Nanodrop DNA conc. (ng/ul) Qubit conc. (ng/ul) Sample volume Total DNA quantity (ng)
87 1 1 166.2 45.6 50 2280
89 2 3 122.9 48 50 2400
85 3 4 313.9 143 50 7150
88b 4 2 214.2 121 50 6050
84 5 6 398.1 188 50 9400
91 6 9 329.7 194 50 9700
88a 7 5 292.6 182 50 9100
86 8 7 359.4 234 50 11700
90 9 8 312.3 218 50 10900
83 10 10 377.7 194 50 9700

The Nanodrop quantity estimates were approximately double those from the Qubit. Qubit values were used for estimation of total yield in the last column. Also, from my qualitative estimate of tissue quantity, it appears that higher quantities tended to be better. If you plot the data, there appears to be an asymptote, so I may have reached optimum tissue quantities.

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