# what dp you mean by "X" - General Lab (Feb/13/2006 )

I can not understand by X. IF YOU HAVE TO PREPARE 50 X TE then what is X. AND 10X TE.

Please explain

I don't know the exact term for 'x', but I think it simply tells how concentrate a solution is. For a 50x solution, you have to do a 1:50 dilution before use it by adding 1 volume of the solution to 49 volume of water or whatever. For a 10x PCR buffer, you always add 1 ul to a 10-ul PCR reaction.

But how to prepare STOCK. For Stock what is X. I can prepare 1 x from 10x but how to to prepare 10x. Please give me example for 10x TE and 50X TE. I am much confused.

X means 'times' or multiplication

50X TAE is 50 times as concentrated as 1X TAE

do you see?

so, you add 50 times as much stuff to the same amount of water (with correct molar ratios) to achieve a 50X solution

Hi, actually I think this is a good question, probably because I have ask the same thing in the past. Ok so 5 years later I think I can now answer this question - I could be wrong but the following logic works anyway.

X is a useful way to store a solution in a concentrated form. However it __does not __ tell you what the actual numerical molar concentration is - you need to look that up yourself - in other words its an arbitrary factor that you are someone has put on with respect to the working concentration. Its nice cause then you dont have to calcualte something everytime you need to do something - its even more useful if you are required to work with an assay that requires various concentration...wash with 10x, then again with 2x and so on...

example: say you are making a cake and the ingredient ask you to add 1 tsp of lemon juice with 2 tsp of salt and you call this solution LS - but later the instruction ask you to add double the amount - and you realize that you would need to make this cake over and over again in the next month - so you just simply double or quadriple everything and call that 2x or 4x - so now the instrcution is simply add 1x of LS and 2x of LS from your stock - see how much time you can save, but notice that LS 4x does not tell you about actual concentration.

It would be nice to actually write out the formula (ingredient) on the bottle though: for example how to make 10x TE buffer. I usually try to increase this as much as possible - that way you can just dilute it out.

al