Hi all,
We would like to purchase 5 mg of phosphine-modified fluorescent dye for site-specific labeling of proteins containing the unnatural aminoacid azide-phenylalanine. We will be labeling small ~50 ul volumes of 10 uM protein with 10+ molar excess dye, and, therefore, will be using small amounts of the phosphine at a time. Once I open the original vial, what are the practical ways to preserve the rest of the reagent without losing reactivity?
Phosphines are oxygen sensitive so handle under nitrogen and store in glovebox or dessicator if you dont have glovebox.
Thank you, Greg. Should I carry out protein labelling under nitrogen (i.e. in a glovebox), too? The reaction is overnight at 4C.
Hi Andrey Revyakin, hosphines are generally considered to be air-sensitive, but the sensitivity to oxygen differs largely with the substituents. While simple alkyl-substituted phosphines can spontaneously ignite in air, others like triphenylphosphine are more or less air-sensitive. Apart from all this, it depends on which solvents you are using. If you work with inert organic solvents, I would suggest to run the entire reaction in the dry-box or under nitrogen using a Schlenk line. This would make sure that no oxidation (e.g. to the pphosphine oxide) will occur.
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