[a1079atw]

Hi all,

These 4 questions (I have no problem with the first one) are related. They are from a calculation refresher quiz so are not mean to be too difficult, but I have no idea how to approach them.

Here are the questions and why I'm stuck:



Thanks in advance. I am very desperate... I've asked my tutor but I still don't understand. Any help is appreciated.

EDIT: I don't know why I couldn't post the 2nd (EDIT*: AND 3RD) question. They are below in the comment section.

[a1079atw]

I don't know why I couldn't post the 2nd question, here it is:


Omg what and now the third question disappeared... Anyway here's the third question:

[mjc123]

Q1: Can you assume l = 1 cm? does it say so?

Q2: It asks for the concentration of the SAMPLE (or SAMLPE!) in capitals to draw your attention to it. In the sample (25 µL), not the well (200 µL).

Q3: Hard to answer without knowing the composition of the buffers. You have to work out how much Master Mix you need in order to get enough of the buffers for all the samples you have to run, e.g. if you had 100 samples you would want at least 1000µL of A, 500µL B and 250 µL C. You are told about the standard curve because you need to create it - you have to run the standards as well as your samples.

Q4: Why does it have to be x5 and x1000? You could use any combination that makes 5000. E.g. 5µL diluted to 500 µL (100x), then 5 µL of this solution diluted to 250 µL (50x).

[sjb]

Also, any reason the questions and answers are posted as images? Sure, in some cases this is important but it does help forum functionality if text can be used wherever possible.

[a1079atw]

Thanks for the reply, I will try to work on the questions again later (Don't have paper with me now).
And sorry about using images! I just thought my descriptions in blue will distinguish them better from the questions. (But now I realised I could've just make the questions bold...)

[a1079atw]

Ok for the Master Mix question, does that mean the solution will be:
You have 30*2 = 60 samples
So you want at least...
6000 uL of Buffer A = 6 mL
3000 uL of Buffer B = 3 mL
1500 uL of Buffer C = 1.5 mL
This is it?

And for the SAMLPE question (haha), does that mean when I got the c = 10 uM (following what I did in the above screenshot), it means 10 uMole in 25 uL (the sample used), so the actual concentration the question is asking for will be 10uMole/25uL = 0.4 mole/L = 0.4M?

Thanks in advance!

[mjc123]

First, the point about the standards (I take it) is that you have to run 30 samples and 6 standards, so you need 36*2 = 72 samples. (But I don't get what they mean by "The remaining 25 µl is going to be the standard/sample". Remaining 25 µl of what?)
Second: the symbol M means moles per litre, not moles (and not Moles, which never has a capital). "10µM in 25 µL" is meaningless - it does not mean 10 µmol in 25 µL. If you had 25 µL of sample and diluted it to the well volume of 200 µL, and measured a concentration of 10 µM in the well, what was the concentration in the original sample?