Distinct Solubilization Mechanisms of Medroxyprogesterone in Gemini Surfactant Micelles: A Comparative Study with Progesterone.

The solubilization behavior of medroxyprogesterone (MP) within gemini surfactant micelles (14-6-14,2Br) was investigated and compared with that of progesterone to uncover distinct solubilization mechanisms. We employed H-NMR and 2D ROESY spectroscopy to elucidate the spatial positioning of MP within the micelle, revealing that MP integrates more deeply into the micellar core. This behavior is linked to the unique structural features of MP, particularly its 17β-acetyl group, which promotes enhanced interactions with the hydrophobic regions of the micelle, while the 6α-methyl group interacts with the hydrophilic regions of the micelle.

Ionic Distribution of an Unequal Electrolyte Near an Air/Water Surface.

The distribution of electrolytes near the air/water surface plays an essential role in many processes. While the general distribution is governed by classic Poisson-Boltzmann statistics, the analytical solution is only available for symmetric electrolytes. From the recent studies in the literature, it is evident that surface adsorption is dependent on specific ions as well as the H-bond structure at the surface.

A Sigma Receptor Agonist Alters Fluidity and Stability of Lipid Monolayers.

Interactions between the sigma receptor agonist PRE-084 and various lipid monolayers, including dipalmitoylphosphatidylcholine (DPPC), DPP-ethanolamine (DPPE), DPP-glycerol (DPPG), DPP-serine (DPPS), palmitoylsphingomyelin (PSM), and cholesterol (Ch), were investigated to elucidate the effects of PRE-084 on membrane fluidity and stability. Their interactions with sigma receptor agonists have potential implications for neuroprotection, antidepressant, analgesic, and cognitive enhancement effects. In this study, we observed that the presence of PRE-084 in the subphase led to increased fluidity in DPPC and DPPE monolayers, whereas decreasing fluidity was observed in DPPG, DPPS, and PSM monolayers.

Interplay of long-chain tetrazine derivatives and biomembrane components at the air-water interface.

Tetrazine (Tz) is an emerging bioorthogonal ligand that is expected to have applications (e.g., bioimaging) in chemistry and chemical biology.

Inverse electron-demand diels-alder reactions of tetrazine and norbornene at the air-water interface.

The surface chemistry of the inverse electron-demand Diels-Alder (IEDDA) reaction at the air-water interface is elucidated. Tetrazine (C18-Tz) and norbornene derivatives (C16-NCA) were used as the reactants. Langmuir monolayers of C18-Tz, C16-NCA, and their binary mixtures were prepared on aqueous substrates.

Inverse Electron Demand Diels-Alder Reactions in the Liposomal Membrane Accelerates Release of the Encapsulated Drugs.

Bio-orthogonal inverse electron demand Diels-Alder (IEDDA) reactions between liposomes containing a tetrazine-based (Tz) compound and 2-norbornene (2-NB) could be a novel trigger for accelerating drug release from the liposomes temporary membrane destabilization, as shown in our previous report. Herein, we evaluated the drug release using NB derivatives with carboxyl groups [5-norbornene-2-carboxylic acid (NBCOOH) and 5-norbornene-2,3-dicarboxylic acid (NB(COOH))] to investigate the effects of substituents at the NB backbone on the drug release rate. First, POTz-liposome composed of a Tz compound (2-hexadecyl--(6-(6-(pyridin-2-yl)-1,2,4,5-tetrazin-3-yl)pyridin-3-yl)octadecanamide) and 1-palmitoyl-2-oleoyl--glycero-3-phosphatidylcholine (POPC) were prepared.

How Self-Assembled Nanodomains Can Impact the Organization of a Phospholipid Monolayer-Flower-Like Arrays.

We found that monolayers of dipalmitoylphosphatidylcholine (DPPC) and semi-fluorinated tetrablock di(F10H16) self-assemble to form a new type of large, complex flower-like patterns on the surface of water and on solid substrates. The hierarchical organization of these unusual self-assemblies was investigated using compression and surface potential isotherms, in situ fluorescence and Brewster angle microscopies, and atomic force microscopy after transfer.

Surface Potential of the Air/Water Interface.

The surface charge/surface potential of the air/water interface plays a key role in many natural and industrial processes. Since the first decade of the 20 century, there are many theoretical proposals to describe the surface charge in the presence of different moieties. However, a complete and consistent description of the interfacial layer remains elusive.

Solubilization of Progesterone and its Derivatives into Gemini Surfactant Solutions.

The solubilization of poorly water-soluble progesterone derivatives into micelles of a gemini surfactant was investigated in an aqueous medium. The aqueous solubility at different temperatures was determined spectroscopically using an ultraviolet visible light spectrophotometer. Thermodynamic parameters for the solubilization were calculated under the basis of the solubility change against temperature.

Lateral interaction of cholesterol with a semifluorinated amphiphile at the air-water interface.

Lipid rafts consisting mainly of sphingomyelin and cholesterol (Ch) on biomembrane surfaces are deeply related to cellular processes such as protein trafficking and signal transduction. During the processes, the raft microdomains affect the fluidty of biological membranes, which is controlled to large extents by Ch. In this paper, we have investigated the interaction between Ch and a semiflurinated alcohol (F6H9OH) from the aspect of a fluidty control using surface chemistry.

Monolayers of a tetrazine-containing gemini amphiphile: Interplays with biomembrane lipids.

The property of a newly synthesized tetrazine derivative comprised of double C18-saturated hydrocarbon chain (C18-rTz-C18) has been studied in situ at the air-water interface. C18-rTz-C18 or a gemini amphiphile contributes to restriction of its tetrazine moiety on the interface, which is expected to be used for bioimaging and analytical reagents. Herein, to understand lateral interactions between Tz and biomembrane constituents, we investigated the interfacial behavior of Langmuir monolayers composed of C18-rTz-C18 and biomembrane lipids such as DPPC, DPPG, DPPE, PSM, and Cholesterol (Ch).

Interfacial Properties of Binary Systems Composed of DPPC and Perfluorinated Double Long-Chain Salts with Divalent Counterions of Separate Electric Charge.

The interfacial behavior of binary monolayers of 1,1'-(1,ω-alkanediyl)-bispyridinium perfluorotetradecanecarboxylate (CnBP(FC14), n = 2, 6, or 10) and dipalmitoylphosphatidylcholine (DPPC) was studied using surface pressure (π)-area (A) and surface potential (ΔV)-A isotherm measurements and morphological observations. In a previous study, we showed that the spacer moieties of C2BP(FC14) and C6BP(FC14) are completely dissociated after spreading on 0.15 M NaCl, whereas the C10BP(FC14) spacer moieties do not dissociate in the monolayer state.

Ionic Nature of a Gemini Surfactant at the Air/Water Interface.

The ionic state of an adsorbed gemini surfactant at the air/water interface was investigated using a combination of surface potential and surface tension data. The combined model was developed and successfully described the experimental data. The results verified the existence of three ionic states of the gemini surfactant in the interfacial zone.

β-Galactosidase Langmuir Monolayer at Air/X-gal Subphase Interface.

This article investigates the surface chemistry properties of the β-galactosidase monolayer at the air-subphase interface at the vicinity of its substrate, X-gal. We have demonstrated that the β-galactosidase in the monolayer form remained active and performed hydrolysis of the X-gal in the subphase. We investigated the β-galactosidase Langmuir monolayer in absence and presence of X-gal in the subphase of varying concentration of X-gal with the sodium chloride solution.

Interactions of a Tetrazine Derivative with Biomembrane Constituents: A Langmuir Monolayer Study.

Tetrazine (Tz) is expected to be used for bioimaging and as an analytical reagent. It is known to react very fast with trans-cyclooctene under water in organic chemistry. Here, to understand the interaction between Tz and biomembrane constituents, we first investigated the interfacial behavior of a newly synthesized Tz derivative comprising a C18-saturated hydrocarbon chain (rTz-C18) using a Langmuir monolayer spread at the air-water interface.

Fluidizing and Solidifying Effects of Perfluorooctylated Fatty Alcohols on Pulmonary Surfactant Monolayers.

Pulmonary surfactant (PS) preparations based mainly on bovine or porcine extracts are commonly administered to patients with neonatal respiratory distress syndrome (NRDS) for therapy. The preparations are sufficiently effective to treat NRDS; however, they are associated with a risk of infection and involve costly purification procedures to achieve batch-to-batch reproducibility. Therefore, we investigated the mechanism and interfacial behavior of synthetic PS preparations containing a mimicking peptide (KLLKLLLKLWLKLLKLLL, Hel 13-5).

New adsorption model -- theory, phenomena and new concept.

According to the conventional Gibbs adsorption model, which is a common assumption about the molecular concentration at surfaces, the adsorbed film of soluble amphiphiles is located at the air/solution interface just like Langmuir monolayer which is illustrated in many physical chemistry text books on "Colloid and Interface Science". According to many proofs of the experimental results here, the newer idea for the surface adsorption is confirmed and explained, which is quite different from the conventional Gibbs surface excess model at the air/solution interface.

Molecular dynamics investigation on adsorption layer of alcohols at the air/brine interface.

Alcohols are a significant group of surfactants which have been employed extensively in industry to improve the interfacial effects. Recently, the change in surface potential (ΔV) of two isomeric hexanols, methyl isobutyl carbinol (MIBC) and 1-hexanol, was investigated by using an ionizing (241)Am electrode. It clearly showed the opposite effects between MIBC and 1-hexanol in the interfacial zone: one enhanced the presence of cations, whereas the other enhanced the presence of anions.

Effect of serum, cholesterol and low density lipoprotein on the functionality and structure of lung surfactant films.

Lung surfactant is a complex mixture of lipid and protein, responsible for alveolar stability, becomes dysfunctional due to alteration of its structure and function by leaked serum materials in disease. Serum proteins, cholesterol and low density lipoprotein (LDL) were studied with bovine lipid extract surfactant (BLES) using Langmuir films, and bilayer dispersions using Raman spectroscopy. While small amount of cholesterol (10 wt%) and LDL did not significantly affect the adsorption and surface tension lowering properties of BLES.

Interfacial behavior of pulmonary surfactant preparations containing egg yolk lecithin.

Mammalian lungs are covered with lipid-protein complexes or pulmonary surfactants. In this work, which aimed towards the less expensive production of artificial pulmonary surfactants, we produced surfactants composed of egg yolk lecithin (eggPC), palmitic acid, and hexadecanol (= 0.30/0.

Solubilization of n-alkylbenzenes into gemini surfactant micelles in aqueous medium.

Solubilization of benzene, toluene, ethylbenzene, n-propylbenzene, n-butylbenzene, and n-pentylbenzene into micelles of decanediyl-1-10-bis(dimethyltetradecylammonium bromide) (14-10-14,2Br(-)) has been investigated in the temperature range from 288.2 to 308.2 K.

Improvement of pulmonary surfactant activity by introducing D-amino acids into highly hydrophobic amphiphilic α-peptide Hel 13-5.

The high costs of artificial pulmonary surfactants, ranging in hundreds per kilogram of body weight, used for treating the respiratory distress syndrome (RDS) premature babies have limited their applications. We have extensively studied soy lecithins and higher alcohols as lipid alternatives to expensive phospholipids such as DPPC and PG. As a substitute for the proteins, we have synthesized the peptide Hel 13-5D3 by introducing D-amino acids into a highly lipid-soluble, basic amphiphilic peptide, Hel 13-5, composed of 18 amino acid residues.

Two-component Langmuir monolayers and LB films of DPPC with partially fluorinated alcohol (F8H9OH).

The interaction of (perfluorooctyl)nonanol (F8H9OH) with dipalmitoylphosphatidylcholine (DPPC) was systematically studied in two-component monolayers at air-water interface. The thermodynamic property and phase morphology of the monolayers were investigated by isotherm measurements and several microscopic methods such as Brewster angle microscopy, fluorescence microscopy, and atomic force microscopy (AFM). The AFM topographies for Langmuir-Blodgett films of F8H9OH exhibit the formation of monodispersed surface micelles.

Interfacial properties in Langmuir monolayers and LB films of DPPC with partially fluorinated alcohol (F8H7OH).

Two-component interactions between (perfluorooctyl) heptanol (F8H7OH) and dipalmitoylphosphatidylcholine (DPPC), which is a major component of pulmonary surfactants in mammals, were systematically elucidated using Langmuir monolayers and Langmuir-Blodgett (LB) films of the compounds. The interactions such as the miscibility of the compounds and their phase behavior were examined from thermodynamic and morphological perspectives. The surface pressure (π)-molecular area (A) and surface potential (ΔV)-A isotherms of the binary monolayers containing F8H7OH in different mole fractions (XF8H7OH) were measured simultaneously.