One of these macrocycles (MP40), with a molecular weight of 846 Da, actually traversed the membrane more rapidly than Propranolol. The particular P2CA used to create the macrocycle clearly had a significant effect on permeability. For example, four MPs with the same peptide component, but formed using different P2CAs (second row of Figure ), displayed significantly different permeabilities, ranging from -logPe = 4.6 to 6.0.