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Electrophoresis combs - Mini-plus vs Midi - (Feb/26/2013 )


I am planning on ordering a new comb for my GeneMate "Mini-Plus Horizontal Gel System (9x11cm)", one which will provide more loading volume than my current 10-well, 1.5mm comb.
The problem is that I couldn't find an 8-well, 1.5mm thick comb which I looked forward to buying.

Here is the catalog:
Only an 8-well, 1.0mm comb is for sale, which I believe holds the same volume as the 10-well 1.5mm which I already have.

Currently I am looking for an alternative comb to purchase.

1. Can somebody please tell me what a "9-well comb, multichannel compatible, 1.5mm thickness" is? Will this comb hold more volume than my 10-well, 1.5mm comb? Or is it the same-sized wells, just with more space in between each well? I don't want to risk buying these because each cost ~$50.

2. Also, because the "Midi" Horizontal Gel System (12x14cm) has an 8-well, 1.5mm comb available on the catalog, I was wondering if that would fit into my "Mini-Plus" casting tray if I decide to get it. I understand that my "Mini-Plus" width is 9cm and that the "Midi" width is 12cm, but can I still buy a "Midi" comb and use it for my "Mini-Plus"casting tray?

3. My last choice is to go with the "Mini-Plus" 5-well, 1.0mm comb. This, definitely will hold more than enough volume -- it's just that sometimes I have more than 5 samples to load at once.

Does anybody have an idea which comb I should buy? I am open to any suggestions. Thank you for your support!!

-Tom Jerry-

How big do you need your well to be? ie: how much volume would you like to load? In my old lab we used to just tape together 2 or more wells of the comb, to make a "super well" so we could load all our PCR product for gel extraction (made it easier and faster than having to cut several lanes, also reduce the amount of extra agarose around the band).

Just an idea ;)

-almost a doctor-

Thank you very much for your response and suggestion :)

Yes, I usually use the 10-well 1.5mm comb with 0.75g/75mL (1%) agarose to load my purified and digested PCR products (36 total µL). Like you have mentioned, my goal here is to use the least amount of agarose necessary to reduce the agarose that I have to clean off when I'm gel-extracting and cutting out the bands. We've managed to barely fit our 36 µL by taping around the wells to increase their volumes. Maybe I'm just lazy, but I thought this was a bit time-consuming. Since I'm about to receive a grant for my lab, I wanted to just buy a new comb that could create more loading space so we won't have to bother dealing with the tape every time. But at the same time each comb is $50 so I didn't want to risk buying a new comb that won't solve our problem. I also didn't want to get the 5-well comb because although it would definitely fit the entire sample, there's a lot of agarose around each band to clean up. Currently I'm waiting for the bioexpress person to reply. I've asked them if each well in the "9-well comb, multichannel compatible, 1.5mm thickness" will fit more than the wells I have now. I'm a bit curious about how this "multichannel compatible" comb is different from any of the standard ones that they sell. As long as this "multichannel compatible" comb still provides more volume than my 10-well combs, I'm happy. Too bad they don't provide pictures for these products.

Again, thank you for advice. Perhaps this taping process is something that I just have to bear with, which, I guess is not that bad.
I will see what the bioexpress person says about the 9-well multichannel compatible comb, if they even reply.


-Tom Jerry-

When I came to lab, I reduced the usual PCR volume from 50 to 20 ul, which subsequently lead also to the fact, that whole amount could be put into well. Since before digestion, the product is purified by MinElute kit with elution volume 10 ul, all restrictions can be also done in 20ul reactions and thicker combs are not needed (our system has possible variants up to 2mm thickness).

But aside this, I think the 9-well comb is what you look for, since it has less wells and is more thick, the multichannel compatibility only means, that the wells are separated and sized in a way, that can be operated with a multichannel pipette. Anyway our system manufacturer always specifies maximum sample volume for 5mm gel for each comb (though it's bit overestimated), so this way you can compare, maybe such information is available for yours too.


Thank you Trof for your advice,

It is indeed a great idea to reduce the PCR, digestion, and elution volumes. I will consider modifying my protocols. If this works, I may not have to purchase a comb after all
Thank you for also clarifying what "multichannel compatibility" means. Hopefully my manufacturer will tell me that the wells of the 9-well 1.5mm comb are larger than those of the 10-well 1.5mm, as it could just be that they have the same size but just more "spaced out". As you have suggested, I look forward to asking them also about the max well volumes of each of the combs they sell.

Thank you again,

-Tom Jerry-

although isc bioexpress is a distributor, you can ask if they will sell custom combs.


I see, thank you for the information!

-Tom Jerry-

Thank you everybody for all of your help!
Fortunately, I have been able to obtain the dimensions of the wells for the "10-well, 1.5mm" gel comb which I have and the "9-well, multichannel compatible, 1.5mm" comb which I was thinking of ordering.

Here are the details, for those who are interested.

The comb is made to fit the width of the gel tray, so combs for the E-4109-1 (9 x 11 gel size) will have product numbers that begin with E-4109.

The width of the tooth is one factor in determining the volume of the well. The placement of the comb into the gel tray leaves 0.2 cm of agarose under the sample well, so that a 0.5 cm thick gel will have a sample well that is 0.3 cm deep. Loading volume is calculated as: Thickness of the tooth (1.0 or 1.5mm) x Width of the tooth x Depth of the sample well (Gel thickness – 0.2 cm).


(9 well, 1.5mm)
7.2 mm
7.2 x 1.5 x 3 = 32.4 microliters
(10 well, 1.5mm)
6.8 mm
6.8 x 1.5 x 3 = 30.6 microliters

I plan to order this 9-well comb, as it will likely fit my sample volumes.
Thank you to all of those who replied.


-Tom Jerry-

Hey I noticed you're having trouble finding the gel comb you need. I had the same problem with a Bio-rad electrophoresis system recently. I found a website that specializes in custom combs with any number of wells or thickness and just ordered one through them. It's if you still need any custom gel combs. Hopefully that helps! smile.png