[evidenso]

Hello
Im a physics who need at little help in some practical chemistry. Well I have got 0.5 mg of some proteine.

http://www.sigmaaldrich.com/catalog/search/ProductDetail/SIGMA/R9388

Well I need to know how many mg/L of protein there are in the solution? Is it possible to calculate this or is it impossible? Is'n it weird to not write down the concentration?

[Arkcon]

Dunno where you got your value for protein concentration, because that page doesn't have it listed, just the molarity of the buffer components.. You may have to call or write or email them to see if this product they're selling is fit for whatever purpose you plan to put it to.  If they want you to buy it, they'll have to give you the info.

To answer your question, with the right info, we can calculate mg per L, given total mass of active and total volume.

[ndhoot]

Typically, the way these proteins are used is that the contents of the vial are diluted in a known volume of the buffer solution such that the entire contents of the vial are transferred to the dilute solution. The diluted solution is then frozen in small portions so that you only take portions that you need at a time. This way you dont subject the protein to repeated freezing and thawing cycles which can damage the protein (this protein is stored at -20C).

So for example, you get 0.5 mg of the protein in a vial. You dilute the contents of the vial to 10 ml using buffer solution. Now you have 10 ml solution with 0.5 mg protein in it. You will have to rinse the vial several times with the buffer solution to ensure that you get all the protein into your diluted solution. You can always call and ask Sigma Tech support for tips on how to use the product and they will probably recommend what buffer to dilute it in. Most likely the buffer that it comes in would be adequate.

Hope this helps.