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1.
Molecules ; 29(20)2024 Oct 18.
Artículo en Inglés | MEDLINE | ID: mdl-39459296

RESUMEN

The indiscriminate use of synthetic surfactants, despite their desirable properties, poses significant environmental risks to ecosystems. This study explores saponins extracted from quinoa (Chenopodium quinoa) residues as a sustainable alternative. Saponin extract (SE) with 42% purity, obtained through hydrodynamic cavitation and membrane technology, was analyzed to determine its techno-functional properties. The critical micelle concentration (CMC) was 1.2 g/L, reducing the surface tension (ST) from 72.0 mN/m to 50.0 mN/m. The effects of temperature (30-90 °C), pH (2-12), and salinity (10,000-150,000 ppm NaCl) on ST and the emulsification index (EI) were assessed using a Box-Behnken design. Optimized conditions yielded an ST of 49.02 mN/m and an EI of 63%. Given these characteristics, SE was evaluated as a detergent across diverse swatches. This study showcases the attributes of quinoa-derived saponins, highlighting their potential for eco-friendly detergent applications.


Asunto(s)
Chenopodium quinoa , Detergentes , Saponinas , Tensión Superficial , Tensoactivos , Chenopodium quinoa/química , Saponinas/química , Tensoactivos/química , Detergentes/química , Temperatura , Concentración de Iones de Hidrógeno , Extractos Vegetales/química , Micelas , Emulsiones/química
2.
J Phys Chem B ; 128(41): 10272-10285, 2024 Oct 17.
Artículo en Inglés | MEDLINE | ID: mdl-39378314

RESUMEN

Predicting the interfacial properties of peptides is important for replacing oil-derived surfactants in cosmetics, oil, and agricultural applications. This work validated experimentally the estimations of surface tension at the critical micelle concentration (STCMC) of six peptides performed through a random forest (RF) model in a previous contribution. In silico interfacial tensions of the peptides were obtained in the system decane-water, and dilational experiments were applied to elucidate the foaming potential. The RF model accurately classified the peptides into high and low potential to reduce the STCMC. The simulations at the decane-water interface correctly identified peptides with high, intermediate, and low interfacial properties, and the dilational rheology allowed the estimation of the possible potential of three peptides to produce foams. This study sets the basis for identifying surface-active peptides, but future work is necessary to improve the estimations and the correlation between dilational properties and foam stabilization.


Asunto(s)
Péptidos , Tensión Superficial , Agua , Péptidos/química , Agua/química , Micelas , Alcanos/química , Simulación por Computador , Tensoactivos/química
3.
World J Microbiol Biotechnol ; 40(11): 334, 2024 Oct 03.
Artículo en Inglés | MEDLINE | ID: mdl-39358641

RESUMEN

The use of biosurfactants represents a promising technology for remediating hydrocarbon pollution in the environment. This study evaluated a highly effective biosurfactant strain-Bacillus cereus GX7's ability to produce biosurfactants from industrial and agriculture organic wastes. Bacillus cereus GX7 showed poor utilization capacity for oil soluble organic waste but effectively utilized of water- soluble organic wastes such as starch hydrolysate and wheat bran juice as carbon sources to enhance biosurfactant production. This led to significant improvements in surface tension and emulsification index. Corn steep liquor was also effective as a nitrogen source for Bacillus cereus GX7 in biosurfactant production. The biosurfactants produced by strain Bacillus cereus GX7 demonstrated a remediation effect on oily beach sand, but are slightly inferior to chemical surfactants. Inoculation with Bacillus cereus GX7 (70.36%) or its fermentation solution (94.38%) effectively enhanced the degradation efficiency of diesel oil in polluted seawater, surpassing that of indigenous degrading bacteria treatments (57.62%). Moreover, inoculation with Bacillus cereus GX7's fermentation solution notably improved the community structure by increasing the abundance of functional bacteria such as Pseudomonas and Stenotrophomonas in seawater. These findings suggest that the Bacillus cereus GX7 as a promising candidate for bioremediation of petroleum hydrocarbons.


Asunto(s)
Bacillus cereus , Biodegradación Ambiental , Fermentación , Hidrocarburos , Agua de Mar , Tensoactivos , Bacillus cereus/metabolismo , Tensoactivos/metabolismo , Hidrocarburos/metabolismo , Agua de Mar/microbiología , Petróleo/metabolismo , Tensión Superficial
4.
Soft Matter ; 20(36): 7313-7320, 2024 Sep 18.
Artículo en Inglés | MEDLINE | ID: mdl-39248026

RESUMEN

In nature, bacteria often swim in complex fluids, but our understanding of the interactions between bacteria and complex surroundings is still evolving. In this work, rod-like Bacillus subtilis swims in a quasi-2D environment with aqueous liquid-liquid interfaces, i.e., the isotropic-nematic coexistence phase of an aqueous chromonic liquid crystal. Focusing on the bacteria motion near and at the liquid-liquid interfaces, we collect and quantify bacterial trajectories ranging across the isotropic to the nematic phase. Despite its small magnitude, the interfacial tension of the order of 10 µN m-1 at the isotropic-nematic interface justifies our observations that bacteria swimming more perpendicular to the interface have a higher probability of crossing the interface. Our force-balance model, considering the interfacial tension, further predicts how the length and speed of the bacteria affect their crossing behaviors. Investigating how a phase change affects bacterial motion, we also find, as soon as the bacteria cross the interface and enter the nematic phase, they wiggle less, but faster, and that this occurs as the flagellar bundles aggregate within the nematic phase. Given the ubiquity of multi-phases in biological environments, our findings will help to understand active transport across various phases.


Asunto(s)
Bacillus subtilis , Agua/química , Cristales Líquidos/química , Movimiento , Tensión Superficial
5.
PLoS One ; 19(9): e0309176, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-39325769

RESUMEN

This study uses numerical methods (ANSYS-Fluent) to investigate the viscous fingering of the displaced phase as a shear-thinning fluid in the classic three-dimensional Hele-Shaw cell. Comparing the behavior of fingerings with different properties on the upper and lower surfaces of a three-dimensional model, it was found that when the upper and lower surfaces are walls, under the combined action of moving contact lines and Saffman-Taylor instability, fingering splitting occurs at the tip, resulting in the appearance of two fingers at the interface. In addition, we have found that interfacial tension has a suppressive effect on short waves. As the interfacial tension increases, the velocity at the advancing tip decreases. Therefore, when the interface tension is 0, viscous fingering displacement reaches the farthest distance. We have also conducted research on the viscous fingering at different temperatures. The results indicate that increasing the temperature leads to a decrease in the viscosity of the displaced phase, making the flow more stable. As the temperature rises, the pressure gradient inside the flow path increases, pushing the viscous fingering further.


Asunto(s)
Modelos Teóricos , Viscosidad , Temperatura , Tensión Superficial , Hidrodinámica , Reología
6.
Food Res Int ; 195: 114963, 2024 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-39277235

RESUMEN

This study aimed to investigate the effect of oxidation on fish gelatin and its emulsifying properties. Fish gelatin was oxidized with varying concentrations of H2O2 (0-30 mM). Increased concentrations of the oxidant led to a decrease in amino acids in the gelatin, including glycine, lysine, and arginine. Additionally, the relative content of ordered secondary structure and triple helix fractions decreased. Zeta potential decreased, while particle size, surface hydrophobicity, and water contact angle increased. Regarding emulsifying behavior, oxidation promoted the adsorption of gelatin to the oil-water interface and reduced interfacial tension. With increased degrees of oxidation, the zeta potential and size of the emulsion droplets decreased. The oxidized gelatin exhibited better emulsifying activity but worse emulsifying stability. Based on these results, a mechanism for how oxidation affects the emulsifying properties of gelatin was proposed: the increase in gelatin's hydrophobicity and the decrease in triple helix structure induced by oxidation reduced the interfacial tension at the oil-water interface. This promoted protein adsorption at the oil-water interface, allowing the formation of smaller oil droplets and enhancing gelatin's emulsifying activity. However, the decrease in electrostatic repulsion between emulsion droplets and the decrease in solution viscosity increased the flocculation and aggregation of oil droplets, ultimately weakening the emulsifying stability of gelatin.


Asunto(s)
Emulsiones , Proteínas de Peces , Gelatina , Interacciones Hidrofóbicas e Hidrofílicas , Oxidación-Reducción , Gelatina/química , Emulsiones/química , Animales , Proteínas de Peces/química , Tamaño de la Partícula , Peróxido de Hidrógeno/química , Viscosidad , Aminoácidos/química , Tensión Superficial , Emulsionantes/química , Peces , Adsorción , Estructura Secundaria de Proteína
7.
Molecules ; 29(18)2024 Sep 10.
Artículo en Inglés | MEDLINE | ID: mdl-39339281

RESUMEN

In this paper, a series of tetrameric surfactants (4CnSAZs, n = 12, 14, 16) endowed with zwitterionic characteristic were synthesized by a simple and convenient method and their structures were characterized by FT-IR, 1H NMR and elemental analysis. Their physicochemical properties were studied using the Wilhelmy plate method, fluorescence spectra and dynamic light scattering technique. 4CnSAZs have higher surface activities and tend to adsorb at the air/water surface rather than self-assembling in aqueous solution. The thermodynamic parameters obtained from surface tension measurements show that both processes of adsorption and micellization of 4CnSAZs are spontaneous and that the micellization processes of 4CnSAZs are entropy-driven processes. Both adsorption and micellization of 4CnSAZs are inclined to occur with the increase of alkyl chain length or temperature. For 4C12SAZs, there are only small-size aggregates (micelles), while the large aggregates (vesicles) are observed at the alkyl length of 4CnSAZs of 14 or 16. This shows that the alkyl chain length for oligomeric surfactants has a greater sensitivity for aggregate growth. The aggregate morphologies obtained from the calculated values of critical packing parameter (p) for 4C14SAZs and 4C16SAZs can be supported by the DLS measurement results. The test results obtained by the separation-water-time method show that 4CnSAZs have good emulsification performance and that the prepared emulsions appear to exit in the form of multiple emulsions. In addition, 4CnSAZs have good antibacterial activities against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The present study reveals the unique behavior of a zwitterionic tetrameric surfactant and may give new insights into molecular design and synthesis of a high degree of surfactants with different structure characteristics for potential application in various industrial fields.


Asunto(s)
Antibacterianos , Tensoactivos , Tensoactivos/química , Tensoactivos/farmacología , Tensoactivos/síntesis química , Antibacterianos/farmacología , Antibacterianos/química , Antibacterianos/síntesis química , Tensión Superficial , Termodinámica , Emulsiones/química , Pruebas de Sensibilidad Microbiana , Micelas , Staphylococcus aureus/efectos de los fármacos , Adsorción , Propiedades de Superficie , Escherichia coli/efectos de los fármacos
8.
J Cell Biol ; 223(12)2024 Dec 02.
Artículo en Inglés | MEDLINE | ID: mdl-39297796

RESUMEN

Perilipins (PLINs), the most abundant proteins on lipid droplets (LDs), display similar domain organization including amphipathic helices (AH). However, the five human PLINs bind different LDs, suggesting different modes of interaction. We established a minimal system whereby artificial LDs covered with defined polar lipids were transiently deformed to promote surface tension. Binding of purified PLIN3 and PLIN4 AH was strongly facilitated by tension but was poorly sensitive to phospholipid composition and to the presence of diacylglycerol. Accordingly, LD coverage by PLIN3 increased as phospholipid coverage decreased. In contrast, PLIN1 bound readily to LDs fully covered by phospholipids; PLIN2 showed an intermediate behavior between PLIN1 and PLIN3. In human adipocytes, PLIN3/4 were found in a soluble pool and relocated to LDs upon stimulation of fast triglyceride synthesis, whereas PLIN1 and PLIN2 localized to pre-existing LDs, consistent with the large difference in LD avidity observed in vitro. We conclude that the PLIN repertoire is adapted to handling LDs with different surface properties.


Asunto(s)
Gotas Lipídicas , Tensión Superficial , Humanos , Gotas Lipídicas/metabolismo , Perilipinas/metabolismo , Perilipinas/genética , Perilipina-1/metabolismo , Perilipina-1/genética , Adipocitos/metabolismo , Triglicéridos/metabolismo , Transporte de Proteínas , Unión Proteica , Perilipina-2/metabolismo , Perilipina-2/genética , Fosfolípidos/metabolismo , Perilipina-3/metabolismo , Perilipina-3/genética , Perilipina-4
9.
Chemosphere ; 365: 143285, 2024 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-39243903

RESUMEN

This work highlights the biosurfactant production potential of yeasts from mangroves in northeastern Brazil. The biosurfactants were evaluated by their emulsifying capacity (EI24), with 6 isolates showing values between 50% and 62%. Surfactant properties from crude extract were measured using drop collapse, oil displacement, Parafilm® M, surface tension and critical micellar concentration tests. The effects of temperature, salinity, pH, and the ability to emulsify different hydrocarbons were analyzed, showing a promising potential of the yeast species investigated to tolerance to high temperatures and acidic pH, in addition to emulsifying different sources of hydrocarbons with environmental impact. It is important to note that the Pichia pseudolambica isolates showed a remarkable ability to reduce the surface tension of water, from 70.82 mN/m to 36.47 mN/m. In addition, the critical micellar concentration (CMC) values ranged from 7 to 16 mg/mL, highlighting the promising surfactant activity of these isolates for future applications. It was identified that the biosurfactant adhered to the yeast cell wall, and FTIR and 1H NMR spectroscopy analysis was carried out on the yeast biomass and its post-sonication supernatant. The results indicate the presence of characteristic functional groups and peaks found in biosurfactants of a glycolipid nature. Taking together the results reveals the promising potential of biosurfactant biosynthesis of P. pseudolambica yeast, a trait not reported in the literature so far for this species. P. pseudolambica presents a relevant metabolic potential for alternative substrate use and resilience to adverse conditions that could enable it to produce biosurfactants for the biotechnological remediation of areas contaminated by oil derivatives. The metabolic properties herein investigated, together with their presence in Brazilian mangroves, make P. pseudolambica an emerging candidate for developing industrial processes and sustainable strategies for the recovery of ecosystems impacted by oil spills, being positioned as a sustainable alternative to conventional surfactants.


Asunto(s)
Biodegradación Ambiental , Sedimentos Geológicos , Pichia , Tensoactivos , Tensoactivos/metabolismo , Brasil , Pichia/metabolismo , Sedimentos Geológicos/microbiología , Sedimentos Geológicos/química , Tensión Superficial , Humedales , Hidrocarburos/metabolismo
10.
J Exp Biol ; 227(19)2024 Oct 01.
Artículo en Inglés | MEDLINE | ID: mdl-39263756

RESUMEN

This study investigates how hibernation affects the surface activity of pulmonary surfactant with respect to temperature and breathing pattern. Surfactant was isolated from a hibernating species, the 13-lined ground squirrel, and a homeotherm, the rabbit, and analysed for biophysical properties on a constrained sessile drop surfactometer. The results showed that surfactant from ground squirrels reduced surface tension better at low temperatures, including when mimicking episodic breathing, as compared with rabbit surfactant. In addition, low temperature adaptation was also observed using only the hydrophobic components of surfactant from ground squirrels. Overall, the data support the conclusion that ground squirrel surfactant has adapted to maintain surface activity during low temperature episodic breathing patterns, and that temperature adaptation is maintained with the hydrophobic components of the surfactant.


Asunto(s)
Hibernación , Surfactantes Pulmonares , Sciuridae , Tensión Superficial , Temperatura , Animales , Sciuridae/fisiología , Surfactantes Pulmonares/química , Conejos , Hibernación/fisiología , Respiración
11.
ACS Biomater Sci Eng ; 10(10): 6690-6710, 2024 Oct 14.
Artículo en Inglés | MEDLINE | ID: mdl-39235368

RESUMEN

Embedded 3D printing (EMB3D) is an additive manufacturing technique that enables complex fabrication of soft materials including tissues and silicones. In EMB3D, a nozzle writes continuous filaments into a support bath consisting of a yield stress fluid. Lack of fusion defects between filaments can occur because the nozzle pushes support fluid into existing filaments, preventing coalescence. Interfacial tension was previously proposed as a tool to drive interfilament fusion. However, interfacial tension can also drive rupture and shrinkage of printed filaments. Here, we evaluate the efficacy of interfacial tension as a tool to control defects in EMB3D. Using polydimethylsiloxane (PDMS)-based inks with varying amounts of fumed silica and surfactant, printed into Laponite in water supports, we evaluate the effect of rheology, interfacial tension, print speeds, and interfilament spacings on defects. We print pairs of parallel filaments at varying orientations in the bath and use digital image analysis to quantify shrinkage, rupture, fusion, and positioning defects. By comparing disturbed filaments to printed pairs of filaments, we disentangle the effects of nozzle movement and filament extrusion. Critically, we find that capillary instabilities and interfilament fusion scale with the balance between support rheology and interfacial tension. Less viscous supports and higher interfacial tensions lead to more shrinkage and rupture at all points in the printing process, from relaxation after writing, to disturbance of the line, to writing of a second line. It is necessary to overextrude material to achieve interfilament fusion, particularly at high support viscosities and low interfacial tensions. Finally, fusion quality varies with printing orientation, and writing neighboring filaments causes displacement of existing structures. As such, specialized slicers are needed for EMB3D that consider the tighter spacings and orientation-dependent spacings necessary to achieve precise control over printed shapes.


Asunto(s)
Dimetilpolisiloxanos , Impresión Tridimensional , Siliconas , Siliconas/química , Dimetilpolisiloxanos/química , Silicatos/química , Reología , Tensión Superficial , Dióxido de Silicio/química , Tensoactivos/química
12.
Colloids Surf B Biointerfaces ; 244: 114178, 2024 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-39216440

RESUMEN

This article investigates the equilibrium arrangement, self-assembly process, and subsequent curing of amphiphilic snowman-shaped Janus particles at the oil-water interface. The independent Janus particles are in vertical equilibrium state and the contact position of the oil-water interface is at the largest cross section of the particle's hydrophobic phase. Under the effect of the surface tension and the adsorption of materials, Janus particles may form particle combinations including the particle pairs and the particle triangle, whose inner and outer sides have the liquid surface exhibiting completely opposite contact angles. Particle combinations form stable parallel double-chain structures with diverse shapes after the self-assembly process. However, the single Janus particles attain a state of mechanical equilibrium under the influence of surrounding particles, enabling them to assemble into regular array structures. The relationship of interfacial tension coefficient between phases can be changed by adjusting the oil-water system, which leads to variations in the self-assembly speed and the final arrangement results. The thin-film with uniformly distributed vertical particles is achieved by replacing the underlying deionized water with a curing agent. Based on the understanding of the interactions between irregularly shaped Janus particles at the oil-water interface, it will be convenient to achieve the controllable self-assembly and widely applications of these particles.


Asunto(s)
Aceites , Tensión Superficial , Agua , Agua/química , Aceites/química , Tamaño de la Partícula , Interacciones Hidrofóbicas e Hidrofílicas , Propiedades de Superficie , Adsorción
13.
Int J Biol Macromol ; 278(Pt 1): 134561, 2024 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-39127283

RESUMEN

Pickering emulsions were co-stabilized by nanoliposome (NL) and thermally denatured ovalbumin (DOVA) based on the induction of OVA with strong particle characteristics through thermal denaturation. DOVA-NL particles were spherical and their sizes were mainly distributed between 50 and 100 nm. The surface tension and interfacial tension of DOVA-NL were significantly reduced, and the surface hydrophobicity, amphiphilicity and free -SH content of DOVA were enhanced after complexation with NL. The content of α-helix and ß-sheet in DOVA decreased, whereas the content of ß-turn and random coil increased after complexation with NL. Hydrophobic interactions, hydrogen bonding and electrostatic forces played a vital role in the interactions between NL and DOVA, leading to conformational changes in DOVA. The number of binding sites between NL and DOVA was more than one, and the interaction between NL and DOVA was exothermic and spontaneous. The emulsification index showed that DOVA-NL-stabilized Pickering emulsions (DNPE) were significantly more stable than DOVA-stabilized emulsions. DOVA-NL particles adsorbed at the oil-water interface and the droplet size of DNPE was smaller than that of DOVA-stabilized emulsions. This study suggests that it may be an effective strategy to improve the stability of Pickering emulsions through co-stabilization with NL and DOVA.


Asunto(s)
Emulsiones , Liposomas , Ovalbúmina , Desnaturalización Proteica , Ovalbúmina/química , Emulsiones/química , Liposomas/química , Interacciones Hidrofóbicas e Hidrofílicas , Nanopartículas/química , Temperatura , Tensión Superficial , Tamaño de la Partícula , Enlace de Hidrógeno
14.
J Biotechnol ; 394: 85-91, 2024 Nov 10.
Artículo en Inglés | MEDLINE | ID: mdl-39178917

RESUMEN

The degummed wastewater from silk processing contains a huge amount of amino acids and polypeptides from sericin. The silk degumming water is far from being exploited fully. Sericin in the degumming water is generally wasted and causes environmental pollution. In this study, simulated silk degumming water was hydrolyzed by alkaline protease to produce abundant amino acids and polypeptides. After enzymatic hydrolysis, the maximum free amino groups concentration in the silk degumming water was approximately 54 mM. It facilitated the recycling of silk degumming water for the production of melanin-like amino acid surfactants as raw materials. 4-Tert-butylcatechol was used as the starting material to generate o-quinone via oxidation by ceric ammonium nitrate. o-Quinone was coupled with free amino groups in enzymatic hydrolysates of silk degumming water to synthesize a sericin-based amino acid surfactant as hydrophobic and hydrophilic group, respectively. Through the green and simple synthesis route, the product was characterized to have a novel melanin-like structure. The product exhibited superior surface-active properties by lowering the surface tension to 32.39 mN m-1. Furthermore, it demonstrated good foaming ability and foam stability, with the initial foam volume of 37 mL and the foam half-life time of more than 25 min. The product owned a good emulsification ability in the oil-water emulsion with delamination time of 297 s and 291 s for emulsion formed by soybean oil and liquid paraffin, respectively. The wetting time of the canvas sheet was only 134 s. Consequently, the product showed low surface tension, good foaming, emulsifying, and wetting properties.


Asunto(s)
Aminoácidos , Melaninas , Sericinas , Seda , Tensoactivos , Tensoactivos/química , Aminoácidos/química , Seda/química , Sericinas/química , Melaninas/química , Melaninas/metabolismo , Hidrólisis , Aguas Residuales/química , Agua/química , Tensión Superficial
15.
Int J Biol Macromol ; 278(Pt 2): 134818, 2024 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-39154679

RESUMEN

This study explored the relationship between pea protein foaming properties and their structure and physicochemical properties under neutral and acidic pH. Results showed that pH modified the zeta potential, particle size and surface tension due to electrostatic changes. FT-MIR and fluorescence spectra revealed pH-induced conformational changes, exposing hydrophobic groups and increasing sulfhydryl content, promoting protein aggregation. At pH 3, the highest foaming capacity (1.273) and lowest foam expansion (6.967) were observed, associated with increased surface hydrophobicity and net charges, ideal for creating light foams with high liquid incorporation for acidic beverages or fruit-based mousses. Pea protein isolate generated stable foams with foam volume stability between 86.662 % and 94.255 %. Although neutral pH conditions showed the highest foam volume stability, their air bubbles increased in size and transitioned from spherical to polyhedral shape, suitable for visual-centric applications, like cappuccino foam and beer-head retention. Foams at pH 5 exhibited the smallest bubbles and maintained their spherical shape, enhancing drainage resistance, beneficial for whipped toppings. Strong correlations (Pearson correlation coefficient higher than 0.600) were noted between the structure, surface and foaming properties, providing crucial insights into optimizing pea protein functionality across various pH conditions, enabling the development of plant-based foamed products with tailored properties.


Asunto(s)
Interacciones Hidrofóbicas e Hidrofílicas , Proteínas de Guisantes , Concentración de Iones de Hidrógeno , Proteínas de Guisantes/química , Relación Estructura-Actividad , Tensión Superficial , Tamaño de la Partícula , Pisum sativum/química , Agregado de Proteínas , Electricidad Estática
16.
Nat Commun ; 15(1): 6785, 2024 Aug 08.
Artículo en Inglés | MEDLINE | ID: mdl-39117639

RESUMEN

Lipopeptides can self-assemble into diverse nanostructures which can be programmed to incorporate peptide sequences to achieve a remarkable range of bioactivities. Here, the influence of peptide sequence and chirality on micelle structure and interactions is investigated in a series of lipopeptides bearing two lysine or D-lysine residues and tyrosine or tryptophan residues, attached to a hexadecyl lipid chain. All molecules self-assemble into micelles above a critical micelle concentration (CMC). Small-angle x-ray scattering (SAXS) is used to probe micelle shape and structure from the form factor and to probe inter-micellar interactions via analysis of structure factor. The CMC is obtained consistently from surface tension and electrical conductivity measurements. We introduce a method to obtain the zeta potential from the SAXS structure factor which is in good agreement with directly measured values. Atomistic molecular dynamics simulations provide insights into molecular packing and conformation within the lipopeptide micelles which constitute model self-assembling colloidal systems and biomaterials.


Asunto(s)
Coloides , Lipopéptidos , Lisina , Micelas , Simulación de Dinámica Molecular , Dispersión del Ángulo Pequeño , Tensoactivos , Difracción de Rayos X , Lipopéptidos/química , Tensoactivos/química , Coloides/química , Lisina/química , Secuencia de Aminoácidos , Tensión Superficial
17.
PLoS One ; 19(8): e0307489, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-39186480

RESUMEN

We propose a new framework for spherical charged compact objects admitting conformal motion in five-dimensional spacetime. The outer spacetime is considered as Reissner-Nordström to obtain matching conditions. The behavior of model characteristics like stress, pressure, and surface tension for the specific density profile is investigated by using Einstein's Maxwell field equations in a five-dimensional framework. For the proposed solution, all physical parameters behave very well even for variations in electric charge parameters. The existence of charged compact stars is also predicted by this study.


Asunto(s)
Movimiento (Física) , Modelos Teóricos , Algoritmos , Tensión Superficial
18.
Ann N Y Acad Sci ; 1538(1): 98-106, 2024 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-39091080

RESUMEN

Scientific progress within the last few decades has revealed the functional morphology of an insect's sticky footpads-a compliant pad that secretes thin liquid films. However, the physico-chemical mechanisms underlying their adhesion remain elusive. Here, we explore these underlying mechanisms by simultaneously measuring adhesive force and contact geometry of the adhesive footpads of live, tethered Indian stick insects, Carausius morosus, spanning more than two orders of magnitude in body mass. We find that the adhesive force we measure is similar to the previous measurements that use a centrifuge. Our measurements afford us the opportunity to directly probe the adhesive stress in vivo and use existing theory on capillary adhesion to predict the surface tension of the secreted liquid and compare it to previous assumptions. From our predictions, we find that the surface tension required to generate the adhesive stresses we observed ranges between 0.68 and 12 mN m - 1 ${\rm m}^{-1}$ . The low surface tension of the liquid would enhance the wetting of the stick insect's footpads and promote their ability to conform to various substrates. Our insights may inform the biomimetic design of capillary-based, reversible adhesives and motivate future studies on the physico-chemical properties of the secreted liquid.


Asunto(s)
Insectos , Tensión Superficial , Animales , Insectos/fisiología , Adhesividad , Capilares/fisiología , Fenómenos Biomecánicos
19.
Sci Rep ; 14(1): 20013, 2024 08 28.
Artículo en Inglés | MEDLINE | ID: mdl-39198595

RESUMEN

Tissue surface tension influences cell sorting and tissue fusion. Earlier mechanical studies suggest that multicellular spheroids actively reinforce their surface tension with applied force. Here we study this open question through high-throughput microfluidic micropipette aspiration measurements on cell spheroids to identify the role of force duration and spheroid deformability. In particular, we aspirate spheroid protrusions of mice fibroblast NIH3T3 and human embryonic HEK293T homogeneous cell spheroids into micron-sized capillaries for different pressures and monitor their viscoelastic creep behavior. We find that larger spheroid deformations lead to faster cellular retraction once the pressure is released, regardless of the applied force. Additionally, less deformable NIH3T3 cell spheroids with an increased expression level of alpha-smooth muscle actin, a cytoskeletal protein upregulating cellular contractility, also demonstrate slower cellular retraction after pressure release for smaller spheroid deformations. Moreover, HEK293T cell spheroids only display cellular retraction at larger pressures with larger spheroid deformations, despite an additional increase in viscosity at these larger pressures. These new insights demonstrate that spheroid viscoelasticity is deformation-dependent and challenge whether surface tension truly reinforces at larger aspiration pressures.


Asunto(s)
Elasticidad , Esferoides Celulares , Humanos , Ratones , Animales , Viscosidad , Células HEK293 , Esferoides Celulares/citología , Células 3T3 NIH , Tensión Superficial
20.
J Oleo Sci ; 73(9): 1159-1168, 2024 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-39168629

RESUMEN

Effects of tetrahydrofuran (THF) concentration on the mixed methane hydrate formation, dissociation, and stability were investigated. The experiment was conducted at 286.2 K and 6 MPa in a quiescent reactor. The presence of THF below 2.5 mol% did not show the evidence of hydrate formation. However, the concentration above 2.5 mol% enhanced the methane formation rate and the methane consumption. Increasing the THF concentration decreased the induction time as the result of the decrease in the surface tension. Moreover, the methane uptake and formation rate increased with the THF concentration due to the higher degree of hydrate nucleation. The methane recovery after the dissociation experiment showed up to 96%. Furthermore, the hydrate stability increased, and the hydrate dissociation kinetics decreased with the increase in the THF concentration. The optimum THF concentration to enhance and improve the hydrate formation kinetics and stability is its stoichiometric concentration.


Asunto(s)
Furanos , Metano , Agua , Furanos/química , Metano/química , Cinética , Agua/química , Tensión Superficial
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