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Characterization and validation of an in vivo confocal Raman spectroscopy led tri‐method approach in the evaluation of the lip barrier
摘要： Background/Aim: It was the aim to establish and validate in vivo confocal Raman spectroscopy for characterization of the lip barrier in conjunction with transepidermal water loss (TEWL) and skin capacitance assessments. For the first time in vivo, barrier-relevant components of the lip (derived, natural moisturizing factors (NMFs) and ceramides are described. Methods: In 32 healthy volunteers, a dental tongue fixation device was inserted to prevent both voluntary and involuntary lip moisturization during measurements. Seventeen individual parameters relating to water, ceramide, and NMF content were assessed via Raman spectroscopy. Additionally, corneometry and TEWL were measured. To give a guidance for the required volunteer group size of future lip barrier studies for all test parameters, coefficients of variation (CV) were calculated and plots showing the required sample size for a given percentage treatment effect. Results: Raman spectroscopy assessed parameters on the lower lip comprehensively characterized the state of the lip barrier. Parameter variability was sufficiently low to corroborate changes in most parameters using relatively small study populations. Conclusions: Lip skin is comparatively well hydrated. Biophysical measurement of the lip barrier function is a challenge, as unconscious licking of the lower lip has to be prevented. In vivo confocal Raman spectroscopy provides insightful parameters for the characterization of the lip barrier and sufficiently low inter-individual variability to assess relatively small parameter changes employing relatively few study subjects. Differences at the molecular level and at a high spatial resolution are detectable, and these insights might provide a breakthrough in the evaluation of lip barrier function and developing solutions for lip care.
关键词： lip skin measurements,closed chamber transepidermal water loss,lip stratum corneum,skin hydration capacitance,Raman spectroscopy
更新于2025-09-12 10:27:22
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[Advances in Experimental Medicine and Biology] Glycobiophysics Volume 1104 || Synchrotron-Radiation Vacuum-Ultraviolet Circular-Dichroism Spectroscopy for Characterizing the Structure of Saccharides
摘要： Circular-dichroism (CD) spectroscopy is a powerful tool for analyzing the structures of chiral molecules and biomolecules. The development of CD instruments using synchrotron radiation has greatly expanded the utility of this method by extending the spectra to the vacuum-ultraviolet (VUV) region below 190 nm and thereby yielding information that is unobtainable by conventional CD instruments. This technique is especially advantageous for monitoring the structure of saccharides that contain hydroxy and acetal groups with high-energy transitions in the VUV region. Combining VUVCD spectra with theoretical calculations provides new insight into the contributions of anomeric hydroxy groups and rotational isomers of hydroxymethyl groups to the dynamics, intramolecular hydrogen bonds, and hydration of saccharides in aqueous solution.
关键词： Glycoprotein,Hydration,Circular dichroism,Synchrotron radiation,Time-dependent density functional theory,Molecular dynamics simulation,Saccharide,Intramolecular hydrogen bond,Solution structure,Structural dynamics,Vacuum ultraviolet,Glycosaminoglycan
更新于2025-09-10 09:29:36
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Use of iodine for improving phase quantification using x-ray tomography
摘要： X-ray computed tomography (CT) has been used to quantify pore structure and crack characterization in cementitious materials. However, similar contrast (greyscale values) of the hydration products in the reconstructed image volume has limited the ability to quantify these phases, and this remains a significant need to further the impact of this experimental method. The goal of this research was to improve the ability to quantify synthesized hydration products by incorporating a contrast agent to improve segmentation between the four main hydration products in portland cement; C-S-H, calcium hydroxide (CH), monosulfate (AFm), and ettringite (AFt). Pure C-S-H, CH, and AFt, and a pure and modified AFm, with iodine as a contrast agent, were synthesized for investigation by x-ray CT. Multi-energy scans were used to isolate individual phases using a synchrotron radiation facility. Using iodine as a contrast agent resulted in accurate quantification of the four main hydration products.
关键词： Composite (E),Hydration products (B),Image analysis (B),X-ray tomography,Cement (D)
更新于2025-09-10 09:29:36
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Small-Angle Neutron Scattering Reveals Energy Landscape for Rhodopsin Photoactivation
摘要： Knowledge of the activation principles for G-protein-coupled receptors (GPCRs) is critical to development of new pharmaceuticals. Rhodopsin is the archetype for the largest GPCR family, yet the changes in protein dynamics that trigger signaling are not fully understood. Here we show that rhodopsin can be investigated by small-angle neutron scattering (SANS) in fully protiated detergent micelles under contrast matching to resolve light-induced changes in the protein structure. In SANS studies of membrane proteins, the zwitterionic detergent [(Cholamidopropyl)dimethylammonio]-propanesulfonate (CHAPS) is advantageous because of the low contrast difference between the hydrophobic core and hydrophilic head groups as compared to alkyl glycoside detergents. Combining SANS results with quasielastic neutron scattering (QENS) reveals how changes in volumetric protein shape are coupled (slaved) to the aqueous solvent. Upon light exposure rhodopsin is swollen by penetration of water into the protein core, allowing interactions with effector proteins in the visual signaling mechanism.
关键词： Detergent,Neutron Scattering,Hydration,GPCR,Protein Dynamics,Vision,Membrane Proteins,Energy landscape,Slaving,Rhodopsin
更新于2025-09-10 09:29:36
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Non-monotonous wetting of graphene-mica and MoS2-mica interfaces with a molecular layer of water
摘要： Hydration of interfaces with a layer of water is a ubiquitous phenomenon, which has important implications for numerous natural and technologically important processes. Nevertheless, at the nanoscale the understanding of the wetting process is still limited, since it is experimentally difficult to follow. Here, graphene and monolayers of MoS2 deposited on dry mica are used to investigate wetting of the 2D material-mica interfaces with a molecularly thin layer of water employing scanning force microscopy in different modes. Wetting occurs non-monotonously in time and space for both types of interfaces. It starts at relative humidities (RH) of 10-17 % for graphenes and 8-9 % for MoS2, and it concludes with a homogeneous layer at 25-30 % and 15-20 %, respectively. Investigation of the process at the graphene-mica interface indicates that up to about 25 % RH, initially a highly compliant and unstable layer of water spreads, which subsequently stabilizes by developing labyrinthine nanostructures. Moreover, these nanostructures exhibit distinct mechanical deformability and dissipation, which is ascribed to different densities of the confined water layer. The laterally structured morphology is explained by the interplay of counteracting long-range dipole-dipole repulsion and short-range line tension, with the latter caused at least in part by the mechanical deformation of the 2D material. The proposed origins of the interactions are common for thin layers of polar molecules at interfaces, implying that the lateral structuring of thin wetting layers at sub-monolayer concentrations may also be a quite general phenomenon.
关键词： confinement,energy dissipation,hydration,slit pore,nanostructures,mechanical compliance,2D material
更新于2025-09-10 09:29:36
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Adsorption properties of the tetragonal P4/nmm WO3 (100) surface toward molecules involved in the hydration of ethylene
摘要： Industrial demand for ethanol has stimulated research on improved catalysts for ethylene hydration. WO3 and other tungsten-based catalysts have been used in direct hydration of ethylene to ethanol, showing high conversion rate and selectivity toward this reaction. By using first-principles calculations based on spin polarized density functional theory, including also dispersion forces, this paper presents the adsorption properties of molecules involved in the ethylene hydration on the tetragonal P4/nmm WO3 (100) surface. The inclusion of dispersion forces, improved our lattice parameters prediction with respect to previous theoretical studies. For the WO3 tetragonal crystal, the (100) surface contains five chemically distinct atoms: a five-fold coordinate W5c, three different types of two-fold binding oxygen O2c, and a single-coordinated oxygen O1c. The energetically favored adsorption sites of water, ethylene, and ethanol (including also hydrogen) are determined here for the first time on this surface. The surface presents high reactivity towards water and ethylene, the single-fold coordinated oxygens stabilize the adsorbed molecules and after adsorption the tungsten atoms take a W6c role. The obtained configurations of the reactants suggest a Rideal-Eley mechanism of the ethylene over adsorbed water. These results reveal the interactions between the selected tetragonal WO3 surface and the molecules involved in the hydration of ethylene, which ultimately determine the reaction mechanism for ethanol production.
关键词： DFT,hydration,tetragonal phase,ethylene,dispersion forces,WO3,tungsten oxide
更新于2025-09-09 09:28:46
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: <i>Ab initio</i> lattice dynamical perspective
摘要： The hydration and ammonization of ZrW2O8 is known to lead to positive and negative thermal expansion behavior, respectively. We report ab initio calculations to understand this anomalous behavior. We identify the crucial low-energy phonon modes involving translations, rotations, and distortions of WO4 and ZrO6 polyhedra, which lead to negative thermal expansion in ZrW2O8 in pure and ammoniated forms; however, the rotation and distortion motions get inhibited on hydration and lead to positive thermal expansion. We demonstrate that the thermal expansion coef?cient could be tailored by engineering the phonon dynamics of a material.
关键词： ZrW2O8,hydration,phonon dynamics,ab initio calculations,ammonization,thermal expansion
更新于2025-09-04 15:30:14
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Direct Observation of Ion Pairing in Aqueous Nitric Acid Using 2D Infrared Spectroscopy
摘要： Ion-ion interactions and ion pairing play an important role in the properties of concentrated electrolyte solutions, yet remain difficult to study due to the heterogeneous and highly dynamic behavior of these systems. In concentrated acid solutions these questions take on a further level of complexity, because the structure of the aqueous proton itself is uncertain, and may be influenced by the counterion. Here, we address these questions by studying the IR spectra of nitric acid as a function of concentration in H2O, and comparing these to the spectra of several alkali nitrate salts. We show how the close proximity between cations and NO3– ions in solution at high concentration affect the IR spectra, and therefore the molecular structures. Using 2D IR spectroscopy, we demonstrate the formation of contracted ion pair configurations in nitric acid solutions between NO3– ions and H+(aq) via the observation of a distinct anisotropic intermolecular crosspeak between these species. By studying the concentration dependence of this spectral feature, we show that this ion-paired configuration exists in solution at concentrations as low as 2M, and suggests that the structure of H+(aq) solvation complex in these ion pairs differs from the structure in bulk solution.
关键词： 2D IR spectroscopy,Proton hydration,Aqueous nitric acid,Ion pairing,Vibrational spectroscopy
更新于2025-09-04 15:30:14
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Drying process of water in a Nafion membrane embedded in the fuel cell analyzed by coherent anti-Stokes Raman scattering spectroscopy
摘要： A coherent anti-Stokes Raman scattering (CARS) spectroscopy system was designed to measure the transient behavior of the humidi?cation of a Na?on membrane used in a polymer electrolyte fuel cell (PEFC). We observed a variation in the intensity of the O–H stretching vibration peak of water during dry and wet gas ?ow. From our measurements, we found that our system showed a high time resolution enough to measure humidi?cation variation in a Na?on membrane in a PEFC. The high acquisition rate revealed the nonequilibrium process of the dehydration or hydration of the Na?on membrane through the temporal variation in the intensity of the O–H stretching vibration peak. The peak consisted of three peaks, suggesting that water molecules hydrated with di?erent bonding energies. The transient behavior of the peaks was probably attributed to the motion of hydration molecules in the proton channel. ? 2018 The Japan Society of Applied Physics
关键词： CARS spectroscopy,O–H stretching vibration,hydration,Na?on membrane,PEFC
更新于2025-09-04 15:30:14