An alternative to Mol. Probes beads are those from other companies. They can be much cheaper at times, and provide quite a bit more information about the homogeneity (or not) of the beads you buy. There are two companies that specialize in the beads, but I could only dredge up one of them (the other is buried somewhere around here and refers to a company named Interfacial Sciences or something similar in the West USA). Sorry to be inconclusive, but here is the other alternative... Bangs Laboratories 979 Keystone Way Carmel, IN 46032-2823 tel:317-844-7176 fax:317-575-8801 email: [log in to unmask] Hope this helps. Bon chance. Chip *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* Chip Montrose Johns Hopkins University tel: 410-955-9681 Ross 930 FAX: (410) 955-9677 720 Rutland Avenue email: [log in to unmask] Baltimore, MD 21205 *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*