A general procedure for the reliable preparation of large quantities of insoluble transmembrane peptides has been developed. Optimal couplings were obtained during synthesis by using high-temperature couplings in conjunction with O-(7-azabenzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HATU) activation. Improved purification schemes were developed that use reverse- phase HPLC on a C1 column and elution with a 2:1 mixture of 1-propanol:1-butanol. Using these methods three very different transmembrane peptides all longer than 25 amino acids have been prepared: glycophorin-A, prion (110-137), and fibroblast growth factor receptor (368-397). (C) 1999 Academic Press.