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    Electrocapillary Curves for the Polarisable Liquid-Liquid Interface in Presence of the Peptide Melittin
    (WALTER DE GRUYTER GMBH, 2016) Uyanik, Ibrahim; Cengeloglu, Yunus
    The adsorption of the anti-microbial peptide melittin at the polarisable water/1,2-DCE (W-DCE) interface is expected to manifest itself by changes in the interfacial tension. These interfacial tension changes during the peptide adsorption at the interface were measured by a custom-built quasi-elastic light scattering (QELS) setup. Electrocapillary curves obtained for melittin at physiological pH evidences the strong affinity of this peptide for the W-DCE interface. In other words, it is evident that at negative potentials the peptide are readily adsorbed and that at more positive potentials desorption of adsorbed peptide from the interface proceeds leading to an increase of interfacial tension.
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    Melittin Adsorption and Lipid Monolayer Disruption at Liquid-Liquid Interfaces
    (AMER CHEMICAL SOC, 2011) Mendez, Manuel A.; Nazemi, Zahra; Uyanik, Ibrahim; Lu, Yu; Girault, Hubert H.
    Melittin, a membrane-active peptide with antimicrobial activity, was investigated at the interface formed between two immiscible electrolyte solutions (ITIES) supported on a metallic electrode. Ion-transfer voltammetry showed well-defined semi-reversible transfer peaks along with adsorptive peaks. The reversible adsorption of melittin at the liquid-liquid interface is qualitatively discussed from voltammetric data and experimentally confirmed by real-time image analysis of video snapshots. It is also demonstrated that polarization of the water/1,2-DCE interface results in drastic drop shape variations caused by large variations of the interfacial tension. The experimental data also confirmed that maximum adsorption occurs near the ion transfer potential. Finally, the interaction of melittin with a monolayer of L-alpha-dipalmitoyl phosphatidylcholine (DPPC) was also investigated showing that melittin destabilizes the lipidic monolayer facilitating its desorption. The non-covalent complex formation between melittin and DPPC was confirmed by mass spectrometry.
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    Transfer of the protonable surfactant dipalmitoyl-phosphatidylcholine across a large liquid/liquid interface: a voltammetric study
    (SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY-TUBITAK, 2018) Uyanik, Ibrahim
    Adsorption behavior of the zwitterionic phospholipid dipalmitoyl-phosphatidylcholine (DPPC) at the polarizable liquid/liquid interface formed between water and 1,2-dichloroethane electrolyte solutions is studied taking into account both the pH of the aqueous phase and the concentration of the phospholipid in the organic phase by cyclic voltammetry. Experimental results showed that the adsorption of the phospholipid strongly depends on the pH of the aqueous phase, which determines the surface ionization of the polar head of the phospholipid molecule and hence the stability of the adsorbed layer of phospholipids.