Structure of the automated plasmid preparation system. (A) Automated plate stacker for plate supply and collection. (B) Schematic representation of plate stacker. (C) Automated plasmid preparator. (D) Schematic representation of the stages of plasmid preparator. The supply stacker and collection stacker are connected to the plasmid preparator. These two stackers have fundamentally the same structure. In B, the numbered squares indicate stages. In the supply stacker, a set of 12 glass-filter plates is piled up on each stage. The 18 stages are designed on a single stacker. The stacked plates are sent from larger to smaller numbered stages and are supplied a set by set from stage 1 of the stacker to the plasmid preparator. For collection, the plates treated in the plasmid preparator are transferred to stage 18. After treatment of the 216 plates, the empty supply stacker can be detached from the plasmid preparator and a new stacker carrying the next 216 plates can be connected. After collection of the first 216 plates by the collection stacker, the empty collection stacker has to be reset. (D) Numbered squares indicate stages. As shown in Cand D, the plasmid preparator receives a set of plates onto the plate sorter [referred to as the dividing apparatus (DA)]. Here, the lowest plate is sorted and sent to stage 1 by conveyor belts. At stages 2 and 3, respectively, solutions 1 (I) and 2 (II) are dispensed by cylinder-type dispensers (blue stages). The neutralization solution (N) is dispensed at stage 4 by a replaceable-tip cylinder-type dispenser (green stage). Between stages 5 and 20, the vacuum pads are lifted up and vacuum filtration is achieved. At stages 9 and 11, washing solution (W) is dispensed by solenoid dispensers as described in Results (yellow stages). At stage 13, 80% ethanol (E) is dispensed by a cylinder-type dispenser. Residual liquid in each well after vacuum filtration is aspirated from above each plate by use of an automatic 96-nozzle aspirator [stages 8, 10, 12, and 14 (red stages)]. Warm air (60°C) is supplied at stages 19 and 20 to dry each well. The plate carrying the plasmid DNA is stacked in the stacking apparatus (SA). Then, a set of plates is sent and collected by the collection stacker.
