Understanding the basics of concentrations

Use this category for general molecular biology questions that don't fit specifically into any of the categories above, including software questions

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Postby John Buckels » Feb 08 2007 12:11 pm

OK thanks!
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Postby Morgan » Feb 28 2007 1:19 am

mdfenko wrote:
John Buckels wrote:Do you find it often falls out of solution at room temp?

no. it has only crystallized when it was accidently stored in the cold room.


You mean it never occur at room temperature?

can You justify this?
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Postby mdfenko » Mar 02 2007 4:26 pm

Morgan wrote:
mdfenko wrote:
John Buckels wrote:Do you find it often falls out of solution at room temp?

no. it has only crystallized when it was accidently stored in the cold room.


You mean it never occur at room temperature?

can You justify this?

as long as it doesn't significantly evaporate. we have never seen it crystallize at room temperature.
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Question 11?

Postby conny » Apr 06 2007 10:32 pm

Mr Buckels... is there some kind of tricks in Q11? :shock:
How do you add 1x buffer and BSA?

I guess I will dilute them before setting up the reaction in practical.

And btw, thanks for posting. It is really useful.
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Re: Question 11?

Postby mdfenko » Apr 09 2007 10:32 am

conny wrote:Mr Buckels... is there some kind of tricks in Q11? :shock:
How do you add 1x buffer and BSA?

I guess I will dilute them before setting up the reaction in practical.

And btw, thanks for posting. It is really useful.

you add concentrated buffer and bsa so that at final volume the concentration is 1x.
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About concentrations...

Postby marinmea » Feb 04 2008 11:08 am

...hi there...
I've got a chemical in a very weird format:
N Methyl N nitro Nitrosoguanidine (wetted with ca. 50% water, containing 5g on a dry weight basis). MW 147.05
5% solubility in water
Here you have the safety data sheet:
[b]dohs.ors.od.nih.gov/pdf/1-methyl-3-nitro-1-nitrosoguanidine%20REVISED.pdf -[/b]
How could I get a final concentration of 100 uM?
Thanks for your help!
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Postby mdfenko » Feb 05 2008 10:27 am

5gm of compound (the water added for stabilization does not matter for this purpose). the formula weight is 147.05gm/mole.

so, 5/147.05=0.034moles=34mmoles. if you dissolve the whole thing in a final volume of 1liter then the concentration will be 34mM (if the solid is 97% then it will be 32.982mM~33mM).

you would then dilute (34/0.1) 340 times (1ml + 339 ml diluent) to make it 100uM.

you could dissolve the 5gm in a final volume of 100ml (5%=maximum solubility). then it would be 340mM. take 0.1ml and dilute to 340ml and you would have 100uM.
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Re: Understanding the basics of concentrations

Postby JMG » Aug 18 2010 9:49 pm

(A fun post)

Here is the direct link to the Sigma product sheet showing the 5M NaCl solution.

Made by 292.2g of NaCl in 1 Liter of (cell culture grade, most likely deionized etc.) water.

http://www.sigmaaldrich.com/etc/mediali ... p59222.pdf

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Re: Understanding the basics of concentrations

Postby relaxin » Aug 19 2010 8:37 am

I took a look of the 5M NaCl datasheet. I do not find anything funny.

It states the concentration is "292.2 g NaCl/liter", not "292.2 g NaCl in 1 liter of water" as you said it.
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Re: Understanding the basics of concentrations

Postby JMG » Aug 19 2010 10:41 am

relaxin,

You and I are saying the same thing - but perhaps in different languages.

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Re: Understanding the basics of concentrations

Postby relaxin » Aug 19 2010 11:31 am

To any biochemist, "292.2 g/liter of NaCl in water" means "292.2 g NaCl per liter of solution and the solvent is water". Since it is 5 M, it is a lot of salt, when you mix 292.2 g of NaCl with 1 liter of water, the final volume will be over 1 liter.

This has nothing to do with language. That is the definition of molarity, 5 moles of NaCl per liter of solution.
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Re: Understanding the basics of concentrations

Postby JMG » Aug 19 2010 11:38 am

Agreed - my first statement on this was flawed.
I should have clarified "1 Liter final solution volume"
rather than "1 Liter of water" being combined with
292.2 g NaCl. A tired oversight.

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Re: Understanding the basics of concentrations

Postby gandhini » Sep 27 2010 10:02 pm

Really informative post!!!
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Re: Understanding the basics of concentrations

Postby semac » Oct 09 2012 9:06 am

Thank you John for this post, I had some problems with concentrations when I was younger but I would like to draw your attention to this free software, Andrew Assistant. It allows to describe a protocol on a screen with a virtual pipette, and verifies all concentrations for every reagent at every single step. If you add that you can make serial dilutions in few clicks, or automatically compute the dilution factors to achieve a certain concentration. Honestly it is very usefull!

http://www.andrewalliance.com/free-pipetting-biology-protocol-design-with-andrew-assistant/

Regards,

IS
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Reason: activate link. this is blatant advertizing but i thought the free software may be useful so i approved the post.
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Re: Understanding the basics of concentrations

Postby tamali.sinha » Jul 05 2017 5:48 am

Very nice post. A lot of my doubts have been cleared. thank u
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