Crucial role of the hydroxyl group orientation in Langmuir monolayers organization–The case of 7-hydroxycholesterol epimers

Wnętrzak, Anita; Chachaj‐Brekiesz, Anna; Janikowska-Sagan, Maria; Rodriguez, J. L.; Condé, J.; Dynarowicz-Łątka, Patrycja

doi:10.1016/j.colsurfa.2018.12.025

Cited by 19 publications

(10 citation statements)

References 59 publications

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“…Upon increasing the lateral pressure the sterol switches from horizontal to vertical orientation, with one OH group detaching from the air-water interface. The blue-colored data in the inset of Figure 5 reproduce an isotherm that was recorded by Wnętrzak et al [27] (Figure 2A in that publication). We extract a 0 = 0.36 nm 2 and a point of inflection at a = 0.54 nm 2 with a pressure of Π = 18 mN/m.…”

Section: Application Of Our Theoretical Model To Experimental Isothermssupporting

confidence: 72%

“…(Recall that because of the scaling by the thermal energy unit this actually means a 0 Π/k B T = 0.4 nm 2 27 mN/m/(4.14 × 10 −21 J) = 2.61.) We now solve Equation (27) for λ, yielding…”

Section: Application Of Our Theoretical Model To Experimental Isothermsmentioning

confidence: 99%

“…The green-colored data set is for a monolayer composed of the synthetic alpha-helical lipopeptide BBC16, adopted from Figure 1 of Strzalka et al [ 35 ]. The blue-colored data set shown in the inset is for 7

-hydroxycholesterol, adopted from Figure 2A of Wnętrzak et al [ 27 ]. For all four isotherms, we have marked the relevant point of inflection with a filled black circle.…”

Section: Figurementioning

confidence: 99%

“…There are many examples for such shoulders and their interpretation in terms of orientational changes. Cyclosporin A [ 21 ], amphotericin B [ 22 , 23 ], nystatin [ 24 ], stearylspermine [ 25 ], monoacylated

-cyclodextrins [ 26 ], cholesterol derivatives such as 7

-hydroxycholesterol [ 27 ] or oxysterol [ 28 , 29 ], carboxylic acid with a symmetrical triphenylbenzene ring system [ 30 ], certain dumbbell-like molecules like amphiphilic bistable rotaxanes [ 31 ] or polyoxometalate (POM)-based inorganic–organic–inorganic molecular hybrids [ 32 ], tri-podal amphiphiles [ 33 ], and alpha-helical peptides [ 34 , 35 , 36 ] have all been reported to undergo orientational adjustments—typically between two orientations—when being used as surface-active molecules in Langmuir monolayers at varying lateral pressure. Other examples include organic–inorganic nanoparticles such as derivatives of varying amphiphilicity of fully condensed polyhedral oligomeric silsesquioxanes (POSS) [ 37 ], matrix organosilane amphiphiles (and also mixed monolayers of vitamin

mimics with these organosilane amphiphiles) [ 38 ], and organic–inorganic hybrid molecular films consisting of a Keggin-type polyoxometalate PW

and a series of gemini amphiphiles with various lengths of the flexible spacers [ 39 ].…”

Section: Introductionmentioning

confidence: 99%

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Incorporation of Molecular Reorientation into Modeling Surface Pressure-Area Isotherms of Langmuir Monolayers

2021

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Langmuir monolayers can be assembled from molecules that change from a low-energy orientation occupying a large cross-sectional area to a high-energy orientation of small cross-sectional area as the lateral pressure grows. Examples include cyclosporin A, amphotericin B, nystatin, certain alpha-helical peptides, cholesterol oxydation products, dumbbell-shaped amphiphiles, organic–inorganic nanoparticles and hybrid molecular films. The transition between the two orientations leads to a shoulder in the surface pressure-area isotherm. We propose a theoretical model that describes the shoulder and can be used to extract the energy cost per molecule for the reorientation. Our two-state model is based on a lattice–sublattice approximation that hosts the two orientations and a corresponding free energy expression which we minimize with respect to the orientational distribution. Inter-molecular interactions other than steric repulsion are ignored. We provide an analysis of the model, including an analytic solution for one specific lateral pressure near a point of inflection in the surface pressure-area isotherm, and an approximate solution for the entire range of the lateral pressures. We also use our model to estimate energy costs associated with orientational transitions from previously reported experimental surface pressure-area isotherms.

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Section: Application Of Our Theoretical Model To Experimental Isothermssupporting

confidence: 72%

Section: Application Of Our Theoretical Model To Experimental Isothermsmentioning

confidence: 99%

-hydroxycholesterol, adopted from Figure 2A of Wnętrzak et al [ 27 ]. For all four isotherms, we have marked the relevant point of inflection with a filled black circle.…”

Section: Figurementioning

confidence: 99%

-cyclodextrins [ 26 ], cholesterol derivatives such as 7

mimics with these organosilane amphiphiles) [ 38 ], and organic–inorganic hybrid molecular films consisting of a Keggin-type polyoxometalate PW

and a series of gemini amphiphiles with various lengths of the flexible spacers [ 39 ].…”

Section: Introductionmentioning

confidence: 99%

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Incorporation of Molecular Reorientation into Modeling Surface Pressure-Area Isotherms of Langmuir Monolayers

2021

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“…The most energetically preferred arrangement for these molecules will prevent the formation of bilayers due to the hydrophobic interaction. On the other hand, the 25-OH and 27-OH systems, due to the hydrogen bonds formed by oxygen atoms from hydroxyl moieties at C(3) and C (25) or C (27), respectively, can easily form bilayers at the water/air boundary.…”

Section: Surface Activity Of 24-oh Is Strikingly Differentmentioning

confidence: 99%

Site of the Hydroxyl Group Determines the Surface Behavior of Bipolar Chain-Oxidized Cholesterol Derivatives─Langmuir Monolayer Studies Supplemented with Theoretical Calculations

et al. 2023

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Cholesterol oxidation products (called oxysterols) are involved in many biological processes, showing both negative (e.g., neurodegenerative) and positive (e.g., antiviral and antimicrobial) effects. The physiological activity of oxysterols is undoubtedly closely related to their structure (i.e., the type and location of the additional polar group in the cholesterol skeleton). In this paper, we focus on determining how a seemingly minor structural change (introduction of a hydroxyl moiety at C(24), C(25), or C(27) in the isooctyl chain of cholesterol) affects the organization of the resulting molecules at the phase boundary. In our research, we supplemented the classic Langmuir monolayer technique, based on the surface pressure and electric surface potential isotherms, with microscopic (BAM) and spectroscopic (PM-IRRAS) techniques, as well as theoretical calculations (DFT and MD). This allowed us to show that 24-OH behaves more like cholesterol and forms stable, rigid monolayers. On the other hand, 27-OH, similar to 25-OH, undergoes the phase transition from monolayer to bilayer structures. Theoretical calculations enabled us to conclude that the formation of bilayers from 27-OH or 25-OH is possible due to the hydrogen bonding between adjacent oxysterol molecules. This observation may help to understand the factors responsible for the unique biological activity (including antiviral and antimicrobial) of 27-OH and 25-OH compared to other oxysterols.

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The Structure of Oxysterols Determines Their Behavior at Phase Boundaries: Implications for Model Membranes and Structure–Activity Relationships

Wnętrzak,

Chachaj-Brekiesz,

Kobierski

et al. 2023

Advances in Experimental Medicine and Biology

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Crucial role of the hydroxyl group orientation in Langmuir monolayers organization–The case of 7-hydroxycholesterol epimers

Cited by 19 publications

References 59 publications

Incorporation of Molecular Reorientation into Modeling Surface Pressure-Area Isotherms of Langmuir Monolayers

Incorporation of Molecular Reorientation into Modeling Surface Pressure-Area Isotherms of Langmuir Monolayers

Site of the Hydroxyl Group Determines the Surface Behavior of Bipolar Chain-Oxidized Cholesterol Derivatives─Langmuir Monolayer Studies Supplemented with Theoretical Calculations

The Structure of Oxysterols Determines Their Behavior at Phase Boundaries: Implications for Model Membranes and Structure–Activity Relationships

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