Hydrophobic Cluster Formation in Aqueous Ethanol Solutions Probed by Soft X-ray Absorption Spectroscopy

Nagasaka, Masanari; Bouvier, Mathilde; Yuzawa, Hayato; Kosugi, Nobuhiro

doi:10.1021/acs.jpcb.2c02990

Cited by 11 publications

(8 citation statements)

References 75 publications

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“…We note that in the case of methanol–water mixtures there is abundant data, also from X-ray spectroscopy, that indicates the presence of chains and cage-like structures; see ref . However, the different strengths of the hydrophobic interaction of the methyl and ethyl groups implicate some structural differences in the two systems, especially in the middle-concentration region …”

Section: Cmj-pes Studies Of Ethanol–water Mixtures In the Bulk Phase:...mentioning

confidence: 78%

“…Several other techniques have been applied to ethanol–water and methanol–water mixtures, being relevant to the findings presented here, such as infrared spectroscopy, ,− NMR, , mass spectrometry, terahertz time-domain spectroscopy, X-ray and neutron diffraction experiments, NEXAFS, Compton scattering, and abundant molecular dynamics simulations; see ref . Many of these works have focused on explaining why the observed entropy increase upon mixing alcohol and water is much smaller than expected for an ideal solution.…”

Section: Cmj-pes Studies Of Ethanol–water Mixtures In the Bulk Phase:...mentioning

confidence: 99%

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Ethanol in Aqueous Solution Studied by Microjet Photoelectron Spectroscopy and Theory

et al. 2022

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Metrics & MoreArticle Recommendations CONSPECTUS: By combining results and analysis from cylindrical microjet photoelectron spectroscopy (cMJ-PES) and theoretical simulations, we unravel the microscopic properties of ethanol−water solutions with respect to structure and intermolecular bonding patterns following the full concentration scale from 0 to 100% ethanol content.In particular, we highlight the salient differences between bulk and surface. Like for the pure water and alcohol constituents, alcohol−water mixtures have attracted much interest in applications of X-ray spectroscopies owing to their potential of combining electronic and geometric structure probing. The water mixtures of the two simplest alcohols, methanol and ethanol, have generated particular attention due to their delicate hydrogen bonding networks that underlie their structural and thermodynamic properties. Macroscopically ethanol−water seems to mix very well, however microscopically this is not true. The aberrant thermodynamics of water−alcohol mixtures have been suggested to be caused by energy differences of hydrogen bonding between water−water, alcohol− alcohol and alcohol−water molecules. These networks may perturb the local character of the interaction between X-rays and matter, calling for analysis that go beyond the normally applied local selection and building block rules and that can combine the effects of light−matter, intra-and intermolecular interactions. However, despite decades of ongoing research there are still controversies of the precise nature of hydrogen bonding networks that underlie the mixing of these simple molecules. Our combined analysis indicates that at low concentration ethanol molecules form a film at the surface since ethanol at the surface can expose its hydrophobic part to the vacuum retaining its two (or three) possible hydrogen bonds, while water at the surface cannot retain all its four possible hydrogen bonds. Thus, ethanol at the surface becomes energetically favorable. Ethanol molecules show a tilting angle variation of the C−C axis with respect to the surface normal as large as 60°at very low concentration. In bulk, around ca. ten %, the ethanol oxygen atoms tend to make a third acceptor hydrogen bond to water molecules. At ca. 20 %, there is a U-shaped change in the CH 3 to CH 2 OH binding energy (BE) shift indicating the presence of ring-like agglomerates called clathrate structures. At the surface, between 5 and 25%, ethanol forms a closely packed layer with the smallest C−C tilting angle variation down to ∼20°. Above 25% and below the azeotrope at the surface, ethanol shows an increase in the tilting angle variation, while at very high ethanol concentrations water tends to move to the surface so giving a microscopic explanation of the azeotrope effect. This migration is connected to the presence of longer (shorter) ethanol chains in the bulk (surface). A brief comparison with discussions and predictions from other spectroscopic techniques is also given. We emphasize the execution of an integrated a...

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Section: Cmj-pes Studies Of Ethanol–water Mixtures In the Bulk Phase:...mentioning

confidence: 78%

Section: Cmj-pes Studies Of Ethanol–water Mixtures In the Bulk Phase:...mentioning

confidence: 99%

Ethanol in Aqueous Solution Studied by Microjet Photoelectron Spectroscopy and Theory

et al. 2022

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“…The self‐assembly behavior of ethanol‐water solutions is driven by hydrogen bonding between water as a proton donor and ethanol as a proton receptor under water ionization (Jiang et al, 2022), in which case, at higher initial ethanol concentration, a higher reinforcement will appear. Also, the hydrophobic interaction of the ethyl groups in ethanol molecules enhanced hydrogen bond structures in water (Nagasaka et al, 2022). Ågren et al (2022) showed that, at low concentrations, ethanol molecules form a film at the surface since ethanol at the surface can expose its hydrophobic part, while water at the surface cannot retain all its four possible hydrogen bonds.…”

Section: Resultsmentioning

confidence: 99%

Impact of falling‐film freeze concentration in a commercial Lager beer

Osorio

Moreno

Hernández

et al. 2023

J Food Process Engineering

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Innovations and technology are the driving forces for new beer industry products, especially in exploring new flavor profiles. Freeze concentration (FC) emerges as an alternative to take advantage of this opportunity. This work studied the falling‐film freeze concentration (FFFC) application on ethanol–water solutions and commercial beer. The effect of flow rate, freezing temperature, and initial concentration of ethanol in the model solution was studied, and the best conditions were found with a surface response analysis and then applied to a commercial beer. The effect on the sensory profile was determined by multidimensional approximation for the lager beer and the concentrated liquid. A significant effect of initial concentration and freezing temperature were found in the ethanol–water solutions, and the best condition was found at −25°C, 400 L/h, and 0.03 w/w, with a concentration index of 1.35. This condition was evaluated for commercial beer, where a concentration index of 1.18 was achieved, caused by solids in beer and molecular interactions of ethanol with other compounds. The sensory profile of a commercial lager beer was modified by increasing the intensity in 38% of the flavor descriptors and the preservation of the other 41% after applying FFFC. The effect of this technique in beer could be a novel method to produce beer products with new flavor profiles. Practical applications Innovations in science and technology added to the search for new flavors promote the development of new products in the beer industry. In this article, a potential use of this freeze concentration (FC) technology was identified for the development of new concentrated beer products. The impact of falling‐film FC in a commercial lager beer was studied. First, obtaining a concentrated beer from this technique was possible, with a higher concentration of total solids and ethanol. In addition, the beer's sensory profile was modified by applying FC, which resulted in an increase in the intensity of 38% of the descriptors and the preservation of 41%. It also allowed the appearance of new flavors and aromas.

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“…35 This result means that an appropriate amount of ethanol denatures the proteins, causing them to unfold to a certain extent, exposing the hydrophobic groups, and thus enhance their surface hydrophobic properties. However, if the ethanol content exceeds a certain content (>30% v/v), they tend to form clusters due to the strong hydrophobic effect of the ethyl groups, 29 which may also interact with the hydrophobic groups on the surface of the proteins resulting in a lower number of hydrophobic groups measured. With the increase in heating time, the S 0 of the proteins in the 0 and 20% ethanol solutions first increased to a maximum (at 4 and 6 h respectively) and then decreased, while the S 0 of the proteins in the 50% ethanol solution increased slowly until 8 h and then decreased.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…27 As a commonly used solvent in the food and pharmaceutical industries, ethanol can alter the structure of proteins, thereby enhancing their biological and functional properties. 28 Ethanol molecules can interact with the water molecules, especially at high volume fractions, 29,30 change the dielectric constant of the aqueous solvent, and can denature the natural proteins by changing their conformational states. 31,32 Ethanol can also affect the fibrillation process and fibril morphology by changing the structure and properties of native proteins during denaturation, although the exact mechanism is still unknown.…”

Section: ■ Introductionmentioning

confidence: 99%

Controlling Solvent Polarity to Regulate Protein Self-Assembly Morphology and Its Universal Insight for Fibrillation Mechanism

Zhang,

Jiang,

Dong

et al. 2024

Langmuir

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The mechanism of ethanol-induced fibrillation of β-lactoglobulin (β-lg) in the acidic aqueous solution upon heating was investigated using various techniques, mainly thioflavin T fluorescence, atomic force microscopy, nonreducing electrophoresis, mass spectrometry, Fourier transform infrared spectroscopy, and circular dichroism spectroscopy. The results showed that fibrillation occurred with a heating time increase, but high ethanol content slowed down the process. At a low ethanol volume fraction, peptides existed after heating for 2 h, with long and straight fibrils formed after 4−6 h, while at a high ethanol volume fraction, the proteins aggregated with very few peptides appeared at the early stage of heating, and short and curved fibrils formed after heating for 8 h. Ethanol weakened the hydrophobic interactions between proteins in the aqueous solution; therefore the latter could not completely balance the electrostatic repulsion, and thus suppressing the fibrillation process. It is believed that the fibrillation of β-lg in the acidic solution upon heating is mainly dominated by the polypeptide model; however, ethanol inhibited the hydrolysis of proteins, and the self-assembly mechanism changed to the monomer model.

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Hydrophobic Cluster Formation in Aqueous Ethanol Solutions Probed by Soft X-ray Absorption Spectroscopy

Cited by 11 publications

References 75 publications

Ethanol in Aqueous Solution Studied by Microjet Photoelectron Spectroscopy and Theory

Ethanol in Aqueous Solution Studied by Microjet Photoelectron Spectroscopy and Theory

Impact of falling‐film freeze concentration in a commercial Lager beer

Controlling Solvent Polarity to Regulate Protein Self-Assembly Morphology and Its Universal Insight for Fibrillation Mechanism

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