Custom Premix Selecting "Custom Premix" option means that all of the beads you have chosen will be premixed in manufacturing before the kit is sent to you.
Confidence in your experimental results starts with knowing the upstream health status of your cells. For any researchers working with cultured or primary cells, confidence in experimental results begins with knowing cell health status.
PEGylation of lipids, liposomes or biomolecules often affords the activation of a functional group, e.g. the presentation of thiol groups for the reaction with MalPEG. Special spacers are needed for controlled cleavage under physiological conditions or just for sterical reasons.