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16 pages, 3072 KiB

Open AccessArticle

The Effect of Selected Flavonoids and Lipoic Acid on Natural and Model Cell Membranes: Langmuir and Microelectrophoretic Methods

by Paulina Laszuk, Wiesław Urbaniak and Aneta D. Petelska

Molecules 2023, 28(3), 1013; https://doi.org/10.3390/molecules28031013 - 19 Jan 2023

Cited by 2 | Viewed by 1049

Abstract

The influence of kaempferol (K), myricetin (M) and lipoic acid (LA) on the properties of natural erythrocytes, isolated from animal blood and biological membrane models (monolayers and liposomes) made of phosphatidylcholine (PC), cholesterol (CHOL), and sphingomyelin (SM), CHOL in a ratio of 10:9, [...] Read more.

The influence of kaempferol (K), myricetin (M) and lipoic acid (LA) on the properties of natural erythrocytes, isolated from animal blood and biological membrane models (monolayers and liposomes) made of phosphatidylcholine (PC), cholesterol (CHOL), and sphingomyelin (SM), CHOL in a ratio of 10:9, was investigated. The Langmuir method, Brewster angle microscopy (BAM) and microelectrophoresis were used. The presented results showed that modification of liposomes with kaempferol, myricetin and lipoic acid caused changes in the surface charge density and the isoelectric point value. Comparing the tested systems, several conclusions were made. (1) The isoelectric point for the DPPC:Chol:M (~2.2) had lower pH values compared to lipoic acid (pH~2.5) and kaempferol (pH~2.6). (2) The isoelectric point for the SM-Chol with myricetin (~3.0) had lower pH values compared to kaempferol (pH~3.4) and lipoic acid (pH~4.7). (3) The surface charge density values for the DPPC:Chol:M system in the range of pH 2–9 showed values from 0.2 to −2.5 × 10⁻² C m⁻². Meanwhile, for the DPPC:Chol:K and DPPC:Chol:LA systems, these values were higher at pH~2 (0.7 × 10⁻² C m⁻² and 0.8 × 10⁻² C m⁻²) and lower at pH~9 (−2.1 × 10⁻² C m⁻² and −1.8 × 10⁻² C m⁻²), respectively. (4) The surface charge density values for the SM:Chol:M system in the range of pH 2–9 showed values from 0.5 to −2.3 × 10⁻² C m⁻². Meanwhile, for the DPPC:Chol:K and DPPC:Chol:LA systems, these values were higher at pH~2 (0.8 × 10⁻² C m⁻²), and lower at pH~9 (−1.0 × 10⁻² C m⁻² and −1.8 × 10⁻² C m⁻²), respectively. (5) The surface charge density values for the erythrocytes with myricetin in the range of pH 2–9 showed values from 1.0 to −1.8 × 10⁻² C m⁻². Meanwhile, for the erythrocytes:K and erythrocytes:LA systems, these values, at pH~2, were 1.3 × 10⁻² C m⁻² and 0.8 × 10⁻² C m⁻² and, at pH~9, −1.7 × 10⁻² C m⁻² and −1.0 × 10⁻² C m⁻², respectively. Full article

(This article belongs to the Special Issue Molecules at Interfaces)

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13 pages, 2691 KiB

Open AccessArticle

Dehydrochlorination of PCDDs on SWCN-Supported Ni₁₀ and Ni₁₃ Clusters, a DFT Study

by Silvia González, Martha Porras, Arianna Jimbo and Cesar H. Zambrano

Molecules 2022, 27(16), 5074; https://doi.org/10.3390/molecules27165074 - 10 Aug 2022

Cited by 1 | Viewed by 1304

Abstract

Polychlorinated dibenzo-p-dioxins (PCDDs) are known to be a group of compounds of high toxicity for animals and, particularly, for humans. Given that the most common method to destroy these compounds is by high-temperature combustion, finding other routes to render them less toxic is [...] Read more.

Polychlorinated dibenzo-p-dioxins (PCDDs) are known to be a group of compounds of high toxicity for animals and, particularly, for humans. Given that the most common method to destroy these compounds is by high-temperature combustion, finding other routes to render them less toxic is of paramount importance. Taking advantage of the physisorption properties of nanotubes, we studied the reactions of atomic hydrogen on physisorbed PCDDs using DFT; likewise, we investigated the reaction of molecular hydrogen on PCDDs aided by Ni₁₀ and Ni₁₃ clusters adsorbed on single-wall carbon nanotubes. Because dihydrogen is an easily accessible reactant, we found these reactions to be quite relevant as dehydrohalogenation methods to address PCDD toxicity. Full article

(This article belongs to the Special Issue Molecules at Interfaces)

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8 pages, 2626 KiB

Open AccessArticle

Successive Deprotonation Steering the Structural Evolution of Supramolecular Assemblies on Ag(111)

by Jiwei Shi, Zhanbo Li, Tao Lin and Ziliang Shi

Molecules 2022, 27(12), 3876; https://doi.org/10.3390/molecules27123876 - 16 Jun 2022

Cited by 2 | Viewed by 1589

Abstract

In this study, we demonstrate the structural evolution of a two-dimensional (2D) supramolecular assembly system, which is steered by the thermally activated deprotonation of the primary organic building blocks on a Ag(111) surface. Scanning tunneling microscopy revealed that a variety of structures, featuring [...] Read more.

In this study, we demonstrate the structural evolution of a two-dimensional (2D) supramolecular assembly system, which is steered by the thermally activated deprotonation of the primary organic building blocks on a Ag(111) surface. Scanning tunneling microscopy revealed that a variety of structures, featuring distinct structural, chiral, and intermolecular bonding characters, emerged with the gradual thermal treatments. According to our structural analysis, in combination with density function theory calculations, the structural evolution can be attributed to the successive deprotonation of the organic building blocks due to the inductive effect. Our finding offers a facile strategy towards controlling the supramolecular assembly pathways and provides a comprehensive understanding of the 2D crystal engineering on surfaces. Full article

(This article belongs to the Special Issue Molecules at Interfaces)

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15 pages, 3993 KiB

Open AccessCommunication

Comparison of Physical Adsorption and Covalent Coupling Methods for Surface Density-Dependent Orientation of Antibody on Silicon

by Katarzyna Gajos, Panagiota Petrou and Andrzej Budkowski

Molecules 2022, 27(12), 3672; https://doi.org/10.3390/molecules27123672 - 7 Jun 2022

Cited by 6 | Viewed by 1928

Abstract

The orientation of antibodies, employed as capture molecules on biosensors, determines biorecognition efficiency and bioassay performance. In a previous publication we demonstrated for antibodies attached covalently to silicon that an increase in their surface amount Γ, evaluated with ellipsometry, induces changes in their [...] Read more.

The orientation of antibodies, employed as capture molecules on biosensors, determines biorecognition efficiency and bioassay performance. In a previous publication we demonstrated for antibodies attached covalently to silicon that an increase in their surface amount Γ, evaluated with ellipsometry, induces changes in their orientation, which is traced directly using Time-of-Flight Secondary Ion Mass Spectroscopy combined with Principal Component Analysis. Here, we extend the above studies to antibodies adsorbed physically on a 3-aminopropyltriethoxysilane (APTES) monolayer. Antibodies physisorbed on APTES (0 ≤ Γ ≤ 3.5 mg/m²) reveal the Γ ranges for flat-on, side-on, and vertical orientation consistent with random molecular packing. The relation between orientation and Γ is juxtaposed for silicon functionalized with APTES, APTES modified with glutaraldehyde (APTES/GA) and N-hydroxysuccinimide-silane (NHS-silane). Antibody reorientation occurs at lower Γ values when physisorption (APTES) is involved rather than chemisorption (APTES/GA, NHS-silane). At high Γ values, comparable proportions of molecules adapting head-on and tail-on vertical alignment are concluded for APTES and the NHS-silane monolayer, and they are related to intermolecular dipole–dipole interactions. Intermolecular forces seem to be less decisive than covalent binding for antibodies on the APTES/GA surface, with dominant head-on orientation. Independently, the impact of glutaraldehyde activation of APTES on vertical orientation is confirmed by separate TOF-SIMS measurements. Full article

(This article belongs to the Special Issue Molecules at Interfaces)

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15 pages, 2028 KiB

Open AccessArticle

Adsorption Properties and Composition of Binary Kolliphor Mixtures at the Water–Air Interface at Different Temperatures

by Magdalena Szaniawska, Katarzyna Szymczyk, Anna Zdziennicka and Bronisław Jańczuk

Molecules 2022, 27(3), 877; https://doi.org/10.3390/molecules27030877 - 27 Jan 2022

Cited by 6 | Viewed by 2168

Abstract

The studies on the adsorption properties and composition of the adsorbed monolayer at the water–air interface of the binary Kolliphor^® ELP (ELP) and Kolliphor^® RH 40 (RH40) mixtures based on the measurements of the surface tension (γ_LV) of [...] Read more.

The studies on the adsorption properties and composition of the adsorbed monolayer at the water–air interface of the binary Kolliphor^® ELP (ELP) and Kolliphor^® RH 40 (RH40) mixtures based on the measurements of the surface tension (γ_LV) of their aqueous solution in the temperature range from 293 to 318 K were carried out. The γ_LV isotherms were described by the exponential function of the second order and the Szyszkowski equation as well as predicted by Fainerman and Miller equation. The obtained γ_LV isotherms were analyzed using the exponential function of the second order, the Szyszkowski, Fainerman and Miller as well as independent adsorption equations. The γ_LV isotherms were also used for determination of the Gibbs surface excess concentration of RH40, ELP and their mixture (Γ) at the water–air interface as well as the mixed monolayer composition. Based on Γ and the constant a in the Szyszkowski equation, the standard thermodynamic functions of adsorption were considered. From the consideration dealing with the γ_LV isotherms obtained by us, it results, among others, that these isotherms for the non-ideal solution of macromolecular surfactants mixture can be predicted using the Fainerman and Miller equation. From this consideration, it also results that a simple method proposed by us, based on the isotherms of RH40 and ELP, allows us to predict the composition of their mixed monolayer in the whole concentration range of RH40 and ELP in the bulk phase. Full article

(This article belongs to the Special Issue Molecules at Interfaces)

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15 pages, 2552 KiB

Open AccessArticle

Sonochemical Reaction of Bifunctional Molecules on Silicon (111) Hydride Surface

by Serge Ismael Zida, Yue-Der Lin and Yit Lung Khung

Molecules 2021, 26(20), 6166; https://doi.org/10.3390/molecules26206166 - 13 Oct 2021

Viewed by 1811

Abstract

While the sonochemical grafting of molecules on silicon hydride surface to form stable Si–C bond via hydrosilylation has been previously described, the susceptibility towards nucleophilic functional groups during the sonochemical reaction process remains unclear. In this work, a competitive study between a well-established [...] Read more.

While the sonochemical grafting of molecules on silicon hydride surface to form stable Si–C bond via hydrosilylation has been previously described, the susceptibility towards nucleophilic functional groups during the sonochemical reaction process remains unclear. In this work, a competitive study between a well-established thermal reaction and sonochemical reaction of nucleophilic molecules (cyclopropylamine and 3-Butyn-1-ol) was performed on p-type silicon hydride (111) surfaces. The nature of surface grafting from these reactions was examined through contact angle measurements, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Cyclopropylamine, being a sensitive radical clock, did not experience any ring-opening events. This suggested that either the Si–H may not have undergone homolysis as reported previously under sonochemical reaction or that the interaction to the surface hydride via a lone-pair electron coordination bond was reversible during the process. On the other hand, silicon back-bond breakage and subsequent surface roughening were observed for 3-Butyn-1-ol at high-temperature grafting (≈150 °C). Interestingly, the sonochemical reaction did not produce appreciable topographical changes to surfaces at the nano scale and the further XPS analysis may suggest Si–C formation. This indicated that while a sonochemical reaction may be indifferent towards nucleophilic groups, the surface was more reactive towards unsaturated carbons. To the best of the author’s knowledge, this is the first attempt at elucidating the underlying reactivity mechanisms of nucleophilic groups and unsaturated carbon bonds during sonochemical reaction of silicon hydride surfaces. Full article

(This article belongs to the Special Issue Molecules at Interfaces)

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19 pages, 4304 KiB

Open AccessArticle

Designing a Useful Lipid Raft Model Membrane for Electrochemical and Surface Analytical Studies

by Michalina Zaborowska, Damian Dziubak, Dorota Matyszewska, Slawomir Sek and Renata Bilewicz

Molecules 2021, 26(18), 5483; https://doi.org/10.3390/molecules26185483 - 9 Sep 2021

Cited by 12 | Viewed by 2281

Abstract

A model biomimetic system for the study of protein reconstitution or drug interactions should include lipid rafts in the mixed lipid monolayer, since they are usually the domains embedding membrane proteins and peptides. Four model lipid films composed of three components: 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), [...] Read more.

A model biomimetic system for the study of protein reconstitution or drug interactions should include lipid rafts in the mixed lipid monolayer, since they are usually the domains embedding membrane proteins and peptides. Four model lipid films composed of three components: 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), cholesterol (Chol) and sphingomyelin (SM) mixed in different molar ratios were proposed and investigated using surface pressure measurements and thermodynamic analysis of the monolayers at the air–water interface and imaged by Brewster angle microscopy. The ternary monolayers were transferred from the air–water onto the gold electrodes to form bilayer films and were studied for the first time by electrochemical methods: alternative current voltammetry and electrochemical impedance spectroscopy and imaged by atomic force microscopy. In excess of DOPC, the ternary systems remained too liquid for the raft region to be stable, while in the excess of cholesterol the layers were too solid. The layers with SM in excess lead to the formation of Chol:SM complexes but the amount of the fluid matrix was very low. The equimolar content of the three components lead to the formation of a stable and well-organized assembly with well-developed raft microdomains of larger thickness, surrounded by the more fluid part of the bilayer. The latter is proposed as a convenient raft model membrane for further physicochemical studies of interactions with drugs or pollutants or incorporation of membrane proteins. Full article

(This article belongs to the Special Issue Molecules at Interfaces)

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Review

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22 pages, 74668 KiB

Open AccessReview

Revealing DNA Structure at Liquid/Solid Interfaces by AFM-Based High-Resolution Imaging and Molecular Spectroscopy

by Ewelina Lipiec, Kamila Sofińska, Sara Seweryn, Natalia Wilkosz and Marek Szymonski

Molecules 2021, 26(21), 6476; https://doi.org/10.3390/molecules26216476 - 27 Oct 2021

Cited by 8 | Viewed by 3628

Abstract

DNA covers the genetic information in all living organisms. Numerous intrinsic and extrinsic factors may influence the local structure of the DNA molecule or compromise its integrity. Detailed understanding of structural modifications of DNA resulting from interactions with other molecules and surrounding environment [...] Read more.

DNA covers the genetic information in all living organisms. Numerous intrinsic and extrinsic factors may influence the local structure of the DNA molecule or compromise its integrity. Detailed understanding of structural modifications of DNA resulting from interactions with other molecules and surrounding environment is of central importance for the future development of medicine and pharmacology. In this paper, we review the recent achievements in research on DNA structure at nanoscale. In particular, we focused on the molecular structure of DNA revealed by high-resolution AFM (Atomic Force Microscopy) imaging at liquid/solid interfaces. Such detailed structural studies were driven by the technical developments made in SPM (Scanning Probe Microscopy) techniques. Therefore, we describe here the working principles of AFM modes allowing high-resolution visualization of DNA structure under native (liquid) environment. While AFM provides well-resolved structure of molecules at nanoscale, it does not reveal the chemical structure and composition of studied samples. The simultaneous information combining the structural and chemical details of studied analyte allows achieve a comprehensive picture of investigated phenomenon. Therefore, we also summarize recent molecular spectroscopy studies, including Tip-Enhanced Raman Spectroscopy (TERS), on the DNA structure and its structural rearrangements. Full article

(This article belongs to the Special Issue Molecules at Interfaces)

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