An aliquot is a measured portion divided off from a larger, homogeneous stock. In peptide work it usually means transferring a reconstituted solution from its original vial into several smaller sterile vials, each holding roughly the volume a single experiment will consume.
Why aliquoting matters in peptide research
It addresses two distinct risks at once. The first is freeze–thaw damage: each round trip through the phase change concentrates solutes at the ice boundary and creates fresh air-water interfaces, both of which promote aggregation. Aliquoting means a stock is frozen once and each portion thawed once. The second is contamination: every needle entry into a stopper is an opportunity for microbial ingress and for stopper coring, so ten withdrawals from one vial carry more cumulative risk than one withdrawal from each of ten.
Sound practice is to mix the stock gently before splitting so every portion is truly representative, to leave headspace for expansion on freezing, and to label each vial with peptide, concentration, lot number and date. Use sterile empty vials and vial labels; the full procedure is in the aliquoting guide and the storage guide.