Dilution Question - Help! - 1/3 serial dilution?? (Jun/17/2008 )

Hello,

This isn't homework, believe it or not I'm actually doing a phd, but didn't know where else to ask as its very basic but i'm getting desperate!!

I want to start at 1200ng of protein in my first tube, and then have a third less in 7 subsequent tubes,
so, 1200, 400, 133.3, 44.4, 14.8, 4.9, 1.6, 0.5.

And these amounts all need to be in 50ul at the end.

So I need to start with 1800ng of protein... ? But what volume to I start with, and then transfer across etc?
I have been trying to figure it out for hours and I just can't do it!!
I am feeling very stupid today. 1:2 is easy enough (I think - i've been doing it for months but now doubting myself after thinking about it too much!)

And similarly, if i wanted to do 1:4's, and 1:5's, how do you work it out??

Thanks very much for any help, I just can not do it.

Hi there

We all have days where our brains go to sleep

You could add 1800ng in your first tube in a volume of 75ul.
Add 50ul of liquid in your other tubes, except the last one - add 25ul.
Take 25ul from the first first and add it to the second and so on.
Your volumes will all be 50ul

Clare

Hiya,

Thanks for that! I was sat in the pub last night doodling on a napkin when i figured it out! Why on earth couldn't i do it earlier??!!

I blame antihistamines making me drowsy!

Anyway, cheers again!

Hi there

We all have days where our brains go to sleep

You could add 1800ng in your first tube in a volume of 75ul.
Add 50ul of liquid in your other tubes, except the last one - add 25ul.
Take 25ul from the first first and add it to the second and so on.
Your volumes will all be 50ul

Clare

QUOTE (Flour Power @ Jun 17 2008, 05:04 PM)

Hello,

This isn't homework, believe it or not I'm actually doing a phd, but didn't know where else to ask as its very basic but i'm getting desperate!!

I want to start at 1200ng of protein in my first tube, and then have a third less in 7 subsequent tubes,
so, 1200, 400, 133.3, 44.4, 14.8, 4.9, 1.6, 0.5.

And these amounts all need to be in 50ul at the end.

So I need to start with 1800ng of protein... ? But what volume to I start with, and then transfer across etc?
I have been trying to figure it out for hours and I just can't do it!!
I am feeling very stupid today. 1:2 is easy enough (I think - i've been doing it for months but now doubting myself after thinking about it too much!)

And similarly, if i wanted to do 1:4's, and 1:5's, how do you work it out??

Thanks very much for any help, I just can not do it.

Yes, the last tube will have 0.82ng.

I have to be a little critical. You're a PhD candidate and you have to ask that simple question?

What department is this?