Abstract: Methods of identifying a fusion inhibitor and inhibitors of gp41-mediated membrane fusion are disclosed. The methods comprise, for example, providing a first helical polypeptide comprising a sequence of IQN17 (SEQ ID NO: 1); providing a second helical polypeptide of 34 or less than 34 amino acids comprising the amino acid sequence W-X1-X2-W-X3-X4-X5-I, wherein X1, X2, X3, X4, and X5 are each independently chosen from any amino acid except proline; measuring, by capillary zone electrophoresis, the degree of complex formation between these peptides; and comparing the measured degree of complex formation to the degree in the presence of a test composition.