Due to the growing world population, there is an ever-increasing need to develop better receptors to recover and recycle phosphate for use in agricultural processes. This need is driven by both agricultural and environmental concerns because phosphate eutrophication has a damaging effect on fresh water supplies by fueling algal blooms. The air/water interface provides a unique region with a low dielectric constant to study the fundamental properties of surface binding. The work presented here provides a model system of phosphate binding to a guanidinium receptor, using the phospholipid DPPA and arginine as probe molecules to study the binding events. Surface pressure area isotherms and infrared reflection absorption spectroscopy (IRRAS) were used to determine surface binding constants of the phosphate-guanidinium interaction, which were greater than 103 M–1. The binding constant in bulk solution, determined by NMR titrations of phosphate and arginine, was on the order of 1 M–1. The over 1,000-fold difference in binding between the bulk and interface shows that the interface provides a region of enhanced binding. Molecular binding interactions were determined using a combination of techniques including Brewster angle microscopy (BAM) to study the morphology of this system, and IRRAS to elucidate the binding motif. This study demonstrates the utility of studying the mechanistic binding processes of organized monolayers which will be used as a basis to design new biologically-inspired synthetic receptors for phosphate capture.

In situ binding recognition of phospholipid-guanidinium interactions at the air/water interface

255th National Meeting (2018)

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