Dilution-titrate 2 fold definition

[biology_06er]

Hi there,

I have some sera and if it says "dilute sera in PBS-T (titrate 2 fold) starting at 1:200...what exactly does it mean...

I'm thinking say I start with a 1:200 1mL sample...take 5uL of sera and add 995uL of PBS-T..that would be my starting diltion right?..So titrating 2 fold would mean...?

Thanks in advance,
b_06er

[daniel.kurz]

My understanding is you do 1:200 then 1:100 then 1:50 then 1:25 then 1:12.5 and so on. The idea that I was taught when doing a 2 fold dilution is that you're diluting by a certain factor each time either 4 times, 3 times, or 2 times. That means taking that ratio and dividing by 2.

Your method of if you wanted 1000 uL as your final volume and removing 5 from 1000 and adding 5 of your sample is correct. You could do this for whatever final volume you want. For example a 1:200 dilution with a final volume of 600 uL would be 3 uL of sample into 597 uL of PBS-T. A 1:100 in 600 would simply be double that sample because you have altered by a factor of 2. So 6 into 594 uL.