The Xcell II Blot module comes from Invitrogen, which now markets the Novex range of protein electrophoresis products. This blot module can be used for the transfer step in western, Southern or northern blotting. Instead of being a complete and separate piece of apparatus for blotting, the XCell II Blot Module is designed to fit into either the XCell SureLock Mini-Cell or the XCell II Mini-Cell, in place of the gel/buffer core assembly (an older version of the modules only fit the XCell II Mini-Cell). As such, this simple module allows Novex protein electrophoresis apparatus to also perform transfer procedures.
My experience with this module has been for western blotting, although different transfers are performed in a similar manner. The module comes in two halves, the bottom half forms a convenient ‘dish’ in which blots are assembled. Transfers are set up as usual with gels, blotting membranes and presoaked blotting paper and pads forming the sandwich. Once the top half of the module is added, the complete module is slotted into the mini-cell on guide rails. The mini-cell and the module are asymmetric so that the module can only be positioned in one orientation, this ensures that the cathode - the ‘dish’ in which blots are assembled - is always the cathode so that transfers occur in the correct direction (if sandwiches are ordered correctly). Another advantage of the design is that the large platinized-titanium and stainless-steel electrodes generate even field strengths for efficient transfer. Thus, transfers are easy and quick to set up: there are no clips, clamps or hinges to fiddle with and once in the mini-cell, the module is simply held by a wedge or cam (depending upon the mini-cell used).
Once in place, the central core of the module is filled with only 200 ml of the transfer buffer, the chamber around the blot module is filled with 600 ml of water to aid heat dissipation and the mini-cell lid is put in place for connection to a power pack. For western blots, either one or two gels can be transferred at a time and blots can be up to 9 cm square, or the size of the NovexÒ gel that you just ran in the mini-cell. The transfers are called ‘semi-wet’ and have the advantage of complete saturation afforded by a wet transfer without the large volumes of buffer.
The instruction manual for the module comes with a table of recommended transfer conditions. This table considers buffers, membranes, voltages and durations for the different types of blots. All common transfer membranes, such as nitrocellulose, PVDF and nylon, can be used and common transfer buffers can also be used with the module. For westerns, Novex transfer buffers are also available which are supplied as 20´ stocks that are diluted with methanol and water. The NuPAGE transfer buffer I have tried with western blots from NuPAGE gels have yielded excellent results. Westerns can be performed in a few hours or over night, but the transfer has to be done in a cold room. As such, any transfer that can be done with a separate apparatus can also be carried out with this module.
Overall, this module is easy and quick to use and also gives good transfers. The module costs $250 and so also represents good value for money if your lab already possesses NovexÒ mini-cells.
Peter Haggie, Ph.D.
Post-Doctoral Fellow
Unversity of California, San Francisco