Total External Reflection X-ray Absorption Spectroscopy Reveals a Zinc Coordination Shell in Phospholipid Langmuir−Blodgett Films

Abstract

We have studied the local environment of zinc in phospholipid Langmuir−Blodgett films with extended X-ray absorption fine structure spectroscopy in total reflection conditions (reflEXAFS). Mono- and multilayer films made of dilauroyl-phosphatidic acid (DLPA) and monolayer films made of dimyristoyl-phosphatidylcholine (DMPC) were deposited on quartz slides from ZnCl2 solutions, and their molecular order was checked by means of X-ray reflectivity measurements. A very good signal-to-noise ratio in the reflEXAFS spectra of both multi- and monomolecular films was obtained. The theoretical fits to the experimental data show that zinc coordinates four atoms about 0.20 nm distant in both acidic DLPA and neutral DMPC films, while in water solutions, zinc coordinates six atoms about 0.21 nm distant.

Application of zinc and calcium acetate to precipitate milk fat globule membrane components from a dairy by-product

“…These results may be due to how zinc and calcium interact with MFGM components. Zinc forms a tetracoordination complex with membrane phospholipids in a tetrahedral geometry, whereas calcium forms a hexacoordination complex in an octahedral geometry (Binder et al, 2001;D'Acapito et al, 2002;Damodaran, 2010). The differences in the geometry of the salt-MFGM complexes may lead to more opportunity for zinc to interact with the protein present in the β stream.…”

The ReflEXAFS station at the GILDA beamline (BM08) of ESRF

“…Finally, further examples of investigations carried out using this apparatus can be found in the literature, such as studies on the oxidation of metals (D'Acapito et al, 2000), structure of multilayers (Staub et al, 2001), lipid Langmuir±Blodgett ®lms (D'Acapito, Relini et al, 2002) and semiconductor thin ®lms (D'Acapito, Davoli et al, 2002).…”

The multi-purpose hard X-ray beamline BL10 at the DELTA storage ring

“…Reflection-mode grazing-incidence X-ray absorption spectroscopy is an excellent method for studying the near-surface structure of thin films, surfaces, adsorbates, etc. (see, for example, Heald et al, 1988;Borthen & Strehblow, 1995;Jiang & Crozier, 1998;d'Acapito et al, 2002;Lü tzenkirchen-Hecht et al, 2003). It has intensively been used in the past for the study of oxide layers on metals and alloys, owing to its capability to investigate the structure and the valence of dis- Transmission-mode X-ray absorption spectrum of a polycrystalline zinc foil at the Zn K-edge at liquid-nitrogen temperature (77 K).…”