The Use of Resin Coated Glass Beads in the Form of a Packed Bed for the Solid Phase Synthesis of Peptides

Abstract

Resin coated glass beads can be used for the solid phase synthesis of peptides. Coated glass beads, as supplied by Northgate Laboratories* for the solid phase synthesis of peptides readily form a packed bed with a low impedance to liquid flow. For the solvents and reagents, used in Peptide synthesis, the resistance to mass transfer through the resin film on the beads is small and one to two orders less than the Merrifield resin beads. The ultimate rate of synthesis is shown to be controlled by reaction velocities and not the rates of reagent transfer. The attachment of the first amino acid to the resin can be achieved by the same procedure as that used with Merrifield beads. Peptides can be cleaved from the resin by passing hydrogen bromide gas saturated with trifluoroacetic acid vapor through the dry bed of beads. For the highest purity and maximum yield the beads should carry 0.4 to 0.7% w/w of 0.5% cross-linked polystyrene resin and the chlorine content should be about 25% of the resin. Under optimum conditions the addition of one amino acid to a peptide being synthesized can be achieved in 25 minutes compared with the 4½ hours required for Merrifield beads. The tetrapeptides produced using the beads had an average purity of 96 to 97% which also compares well with the purity of the same product made from the Merrifield beads. Under optimum conditions the Northgate beads can produce the tetrapeptide L-leucyl-L-alanyl-glycyl-L-valine (leu-ala-gly-val) at a rate of 170 micrograms per minute per unit volume of substrate.