A fast and inexpensive procedure for drying polyacrylamide gels.

spective gel image revealed that the density of the area between 200 and 1600 bp was very similar in all of the four lanes. Therefore, volume-corrected calculation of this experiment (Fig. 1B, filled columns) displayed results comparable to the densitometric analysis of Fig. 1A (shown in Fig. 1B, open columns). Thus, this method offers reproducible results as a function of cell number but independent of the volume loaded on the gel. To study the detection limits of this new method we further decreased the cell number (Fig. 2). GH3 cells (0.25 3 10, 0.125 3 10, and 62,500) were treated with okadaic acid and apoptotic DNA fragments were isolated as mentioned above. The TE volume to elute the DNA from the miniprep column was decreased to 30 ml and the eluate was completely loaded on the agarose gel. Distinct DNA bands were clearly visible at cell numbers of 0.25 3 10 (Fig. 2A, lane 6) and 0.125 3 10 (lane 4), while the laddering from 62,500 treated cells appeared very faint (lane 2). In contrast to the optical impression, densitometric scanning of the gel image revealed an OD intensity of specific as well as background signals in good agreement to the cell number (Fig. 2B) even at 62,500 cells. Thus, additional densitometric analysis showed successful discrimination of the bands between 200 and 1600 bp at all three cell numbers (Fig. 2C). In conclusion, the use of modified lysis and precipitation conditions allowed the successful rapid isolation of visible discrete apoptotic DNA fragments from as less as 0.125 3 10 cells. Densitometric analsis of the laddering was even more sensitive and llowed analysis down to 62,500 cells. With this modfied miniprep spin column protocol at least 12 samles can be processed in about 1 h. Further experients have shown that the technique is successfully pplicable to the study of drug-induced apoptosis in ther adherent cell lines as well as cells growing in uspension cultures.