Reconstitution of a hygroscopic protein. - (Jul/05/2015 )

Hi all, I have a big doubt about a step on this protocol.

We talk about a protein lyophilized, hygroscopic.

Handling procedure:

1) set balance to zero

2)Remove cap from vial

3)Weigh the protein into weighing device

4) Close vial

5) Reord mass of the Protein in the weighing device

6) Transfer Protein into a sample dilution vassel

7)Weigh back weighing device on the balance, record mass and calculate mass of Protein transferred to the sample dilution vessel

8)dissolve protein in sample dilution vessel in an apropriate amount of 60% (v/v) ethanol

9) Calculate protein concetration on the basis of the protein content of dry substance.

10) close vial and store the protein.

I have doubts about the step 7. What do they mean with "calculate mass" ? could be something connceted with the poit that this protein is hygroscopic? How can I do this step?

thank you in advance for any reply.

This step means that despite having X amount of protein in the initial tray, it is very unlikely that you will have moved all of it to the dilution vessel, hence there will be some left in the tray (amount Y). You subtract the mass left behind from that weighed in the first place, to calculate the total amount of protein you have in the dilution vessel, and dilute according to this calculation.

i.e. X-Y= total protein in dilution.

I wonder: why the firsts step? Why not just adding the protein directly to the "sample dilution vassel" ?

Measuring the mass twice, seems pointless.

I really do not understand the set up as it is given.