Effect of cation enrichment on dipalmitoylphosphatidylcholine (DPPC) monolayers at the air-water interface
Research output: Contribution to journal › Research article › Contributed › peer-review
Contributors
Abstract
The effect of highly concentrated salt solutions of marine-relevant cations (Na+, K+, Mg2+, and Ca2+) on Langmuir monolayers of dipalmitoylphosphatidylcholine (DPPC) was investigated by means of surface pressure-area isotherms, Brewster angle microscopy (BAM), and infrared reflection-absorption spectroscopy (IRRAS). It was found that monovalent cations and Mg2+ have similar phase behavior, causing DPPC monolayers to expand, while Ca2+ induces condensation. All cations disrupted the surface morphology at high cation concentration, resulting in decreased reflectivity from the monolayer. Monolayer refractive index was calculated from BAM image intensity in the liquid condensed phase and decreased with increasing cation concentration, which suggests that orientation of the alkyl chains change. Monovalent ions increase ordering of the alkyl chains, more than divalents, yet have little interaction with the DPPC headgroup. Mg2+ induces gauche defects in the alkyl chain and increases headgroup hydration at low lipid coverage but increases chain ordering and dehydrates the headgroup at high lipid coverage. Ca2+ orders alkyl chains and dehydrates the phosphate moiety, independent of lipid phase. At the highest salt concentration investigated, significant narrowing of the asymmetric PO2- vibrational mode occurs and is attributed to considerable dehydration of the DPPC headgroup.
Details
Original language | English |
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Pages (from-to) | 353-364 |
Number of pages | 12 |
Journal | Journal of colloid and interface science |
Volume | 478 |
Publication status | Published - 15 Sept 2016 |
Peer-reviewed | Yes |
Externally published | Yes |
External IDs
ORCID | /0000-0002-8120-8553/work/161409575 |
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Keywords
Sustainable Development Goals
ASJC Scopus subject areas
Keywords
- Brewster angle microscopy (BAM), Cations, Dipalmitoylphosphatidylcholine (DPPC), Infrared reflection-absorption spectroscopy (IRRAS), Langmuir isotherms, Marine aerosols, Monolayers