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Minkov IL, Arabadzhieva D, Salama IE, Mileva E, Slavchov RI. Barrier kinetics of adsorption-desorption of alcohol monolayers on water under constant surface tension. SOFT MATTER 2019; 15:1730-1746. [PMID: 30657160 DOI: 10.1039/c8sm02076k] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The desorption of spread decanol and dodecanol monolayers at controlled constant surface tension is shown to proceed under mixed barrier-diffusion control; the role of the convective diffusion is also discussed. The desorption rate is measured as a function of the density of the monolayer and the temperature. The rate of barrier desorption increases as the monolayer approaches the collapse point, reaching an infinite value. The average desorption time of an adsorbed dodecanol molecule increases linearly with the area per molecule, and is phase-specific - it is higher for the liquid condensed state of the monolayer than for the liquid expanded. The desorption rate increases with temperature; the activation energy for desorption is independent of the compression and the surface phase. The increase of the intensity of convection is shown to produce a vanishingly thin diffusion layer and causes the desorption to proceed under pure barrier control. A schematic map of the adsorption-desorption regimes acting as a function of time and intensity of the convection is constructed. General expressions for the rate of adsorption and desorption of alcohols are formulated.
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Affiliation(s)
- Ivan L Minkov
- Department of Physical Chemistry, Faculty of Chemistry and Pharmacy, Sofia University, 1 J. Bourchier Blvd., 1164 Sofia, Bulgaria
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Diociaiuti M, Giordani C, Kamel GS, Brasili F, Sennato S, Bombelli C, Meneses KY, Giraldo MA, Bordi F. Monosialoganglioside-GM1 triggers binding of the amyloid-protein salmon calcitonin to a Langmuir membrane model mimicking the occurrence of lipid-rafts. Biochem Biophys Rep 2016; 8:365-375. [PMID: 28955978 PMCID: PMC5614544 DOI: 10.1016/j.bbrep.2016.10.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 09/08/2016] [Accepted: 10/10/2016] [Indexed: 12/18/2022] Open
Abstract
GM1 ganglioside is known to be involved in the amyloid-associated diseases and it is a crucial factor for the assembly of amyloid proteins on lipid-rafts, which are lipid structures located on the synaptic plasma membranes. Due to its slow aggregation rate, we employed salmon calcitonin (sCT) as a suitable probe representative of amyloid proteins, to study the interaction between this class of proteins and a membrane model. Here, we prepared a neuronal membrane model by depositing onto mica two Langmuir-Blodgett films in liquid-condensed phase: the outer monolayer was characterized by high content of GM1 (50%) and minority parts of cholesterol and POPC (25-25%), while the inner one by plain POPC. To deeply investigate the interaction of sCT with this model and the role-played by GM1, we prepared the outer leaflet adding sCT at a concentration such that the number of proteins equals that of GM1. Atomic Force Microscopy revealed the occurrence of two distinct kinds of flat surfaces, with globular aggregates localized exclusively on top of the highest one. To unravel the nature of the interaction, we studied by ζ-potential technique liposomes composed as the outer leaflet of the model. Results demonstrated that an electrostatic interaction sCT-GM1 occurred. Finally, to investigate the interaction thermodynamics between sCT and the outer leaflet, Langmuir films as the outer monolayer and containing increasing content of sCT were studied by compression isotherms and Brewster Angle Microscopy experiments. Based on the all body of results we propose an interaction model where GM1 plays a pivotal role.
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Affiliation(s)
- Marco Diociaiuti
- Dipartimento di Tecnologie e Salute, Istituto Superiore di Sanità, I-00161 Roma, Italy
- Correspondence to: Dipartimento di Tecnologie e Salute, Istituto Superiore di Sanità, viale Regina Elena 299, 00161 Roma, Italy.
| | - Cristiano Giordani
- Dipartimento di Tecnologie e Salute, Istituto Superiore di Sanità, I-00161 Roma, Italy
- Instituto de Física, Universidad de Antioquia, Medellín, Colombia
| | - Gihan S. Kamel
- Department of Physics, Faculty of Science, Helwan University, Cairo, Egypt
- Dipartimento di Fisica and ISC-CNR, Sapienza Università di Roma, I-00185 Roma, Italy
| | - Francesco Brasili
- Dipartimento di Fisica and ISC-CNR, Sapienza Università di Roma, I-00185 Roma, Italy
| | - Simona Sennato
- Dipartimento di Fisica and ISC-CNR, Sapienza Università di Roma, I-00185 Roma, Italy
| | - Cecilia Bombelli
- CNR, Istituto di Metodologie Chimiche, Sezione Meccanismi di Reazione, c/o Dipartimento di Chimica, Università degli Studi di Roma “Sapienza”, I-00185 Roma, Italy
| | - Karen Y. Meneses
- Instituto de Física, Universidad de Antioquia, Medellín, Colombia
| | - Marco A. Giraldo
- Instituto de Física, Universidad de Antioquia, Medellín, Colombia
| | - Federico Bordi
- Dipartimento di Fisica and ISC-CNR, Sapienza Università di Roma, I-00185 Roma, Italy
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