Iodoacetamide

[unigirl]

Is it possible to make a 50ml stock solution of iodoacetamide? We have a 25g vial of iodoacetamide to hand (in darkness!) and plan to use the solution on cysteine residues in peptide sequencing.

Thanks

[Peter Pedant]

yes it is apparently

goggle iodoacetamide stock solution
and it will tell you how to do it

and good luck with the peptide sequencing

[theprof]

OK folks, let’s ignore the all encompassing wisdom of Google for once and base the answer on extensive experience of protein sequencing and the associated chemistry.

It’s not possible to store stock solutions of iodoacetamide. Stock solutions of iodoacetamide are highly unstable. I have in the past used solutions that have been stored at -25 degrees C in quantities of no more than 1ml within two weeks of preparation but there are issues with reaction rates in some circumstances.

All solutions of iodoacetamide must be freshly prepared and are best used within hours. I do sympathise as a stock solution would be a great time-saver. If budget restrictions aren’t an issue, I’d take a look at the pre-packaged vials obtainable from Sigma-Aldrich or Fisher Scientific typically of around 50mg. They simplify the solution preparation tremendously. Be sure to keep the vial and resulting solution below 8 degrees C and ensure that darkness is maintained throughout the use of the iodoacetamide.

There are some anecdotal reports of instability of old samples of iodoacetamide so that could be another reason for the purchase of fresh stock – my university stockrooms and science park labs are currently replenished monthly with these alkylating reagents. Is there a production date on the 25g vial? If it was manufactured by BDH, I'd bin it (showing my age here!) Don’t forget to use HPLC grade solvents throughout.

[wildwood]

By golly, Prof. That's exactly what I was going to write. You beat me to it. lol

[theprof]

If I'd known you were going to be along wildwood, I'd have left it to you!