I'm preparing sperm lysates for mass spec, and I'm specifically interested in looking at oxidative modifications to proteins. I'd like to derivatize and enrich these samples prior to mass spec to improve detection of carbonylated proteins. I'm planning on using biotin hydrazide for derivatization. My plan is to derivatize samples and then store them at -80°C for up to 6 months prior to enrichment on an avidin affinity column and subsequent FASP tryptic digestion.

My questions are:

- is the use of a reducing agent (e.g. sodium cyanoborohydride, sodium triacetoxyborohydride) definitely required in order to stabilise the derivatization product, particularly given the length of storage?

- if a reducing agent is required, are there alternatives to the highly toxic sodium cyanoborohydride that can be used in aqueous buffers?