Surface behavior of prostaglandins (PGs)

Abstract

This study establishes some correlations between molecular structure and surface function of six prostaglandins in a model membrane system. Using spread films at the air/water interface, we determined surface pressure and surface potential of PGs A₁, A₂, E₁, E₂, F_1α and F_2α. All the PGs formed films with low pressure (0 to 9 dyne/cm) and relatively low surface potentials (ΔV = 10 to 250mV). On 0.15M NaCl, the ∏ and ΔV values were in the order E₁ > F_1α > A₁ > F_1α > A₁ > F_2α = A₂ > E₂ and F_1α > E₁ > A₁ > A₂ > F_2α > E₂ respectively. Clearly, the cis unsaturation in the carboxylic chain of the PG₂ series conferred greater instability to the films, as indicated by the lowest Π and ΔV values. Also, members of the PG₁ series penetrated films of dipalmitoyl phosphatidyl choline (DPPC) better than PG₂ did, the ablest being E₁ (ΔΠ = 12 dyne/cm) and the poorest F_2α (ΔΠ = 2 dyne/cm); penetration of E₁ and F_2α was independent of the initial pressure (Π_i) of the DPPC film, whereas with A₁ and F_1α ΔΠ decreased as Π_i increased. The PGs expressed marked discriminating capacities for the electrolyte, as indicated by differences in their Πand ΔV responses to Na⁺ and Ca⁺⁺ as well as for the lipid, as indicated by different penetration (ΔΠ values) into DPPC films.