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Aquaphotomics - Exploring Water Molecular Systems in Nature

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Analytical Chemistry".

Deadline for manuscript submissions: closed (30 June 2022) | Viewed by 60679

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Special Issue Editors


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Guest Editor
Aquaphotomics Research Department, Graduate School of Agriculture Sciences Kobe University, Kobe 657-8501, Japan
Interests: aquaphotomics; water; light; spectroscopy; chemometrics; non-invasive biomeasurements; water molecular structure; water functionality

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Co-Guest Editor
Aquaphotomics Research Department, Graduate School of Agriculture Sciences Kobe University, Kobe 657-8501, Japan
Interests: aquaphotomics; water; light; spectroscopy; chemometrics; non-invasive bio measurements; water molecular structure; water functionality

Special Issue Information

Dear Colleagues,

Aquaphotomics as a new “omics” science was established in 2005, guided by the vision to explore the biological world and the aqueous systems using light–water interaction. In the past, water was seen as a passive element, an inert molecule, hindering useful spectral signals. A radical new approach in spectroscopy—using water–light interaction—opened a new door for the world of science. Water as an active factor, a biomolecule in its own right, one which builds miscellaneous structures leading to various functionalities, has been recognized and is slowly becoming a new interdisciplinary scientific platform connecting sciences and technology.

The mission of aquaphotomics is to understand the role of water, a simple but sophisticated molecule that connects everything with its rhythm and ability for self-organization. All spectroscopy techniques are crucially important for aquaphotomics, whether they cover visible light, infrared (IR), near-infrared (NIR), ultraviolet (UV), Raman, or Terahertz frequencies. The water spectra of the systems under various perturbations create a large ocean of data. Thanks to the advancement of computer science, data analysis, and new measurement technologies, in recent years, the spectral studies of water are expanding in a wide variety of disciplines, providing a common platform for diverse technological applications.

This Special Issue of Molecules is devoted to learning and spreading new knowledge regarding features and functionalities of this most incredibly versatile molecule, water, and the connections and networks it creates, from which different functionalities arise. In these unprecedented times of a worldwide pandemic, we hope that this Special Issue will, just like water, make connections and motivate many people to know more about life and the surrounding world, a paradigm shift that will change our collective attitude toward nature.

The Special Issue welcomes articles that examine the state of the art in water research using spectroscopy, water structure and science, spectral preprocessing and analysis, emerging areas of applications of aquaphotomics knowledge, and future directions of development. All scientists working in these emerging and promising fields of research are strongly encouraged to submit their original papers and review works for publication in this Special Issue.

Prof. Dr. Roumiana Tsenkova
Prof. Dr. Jelena Muncan
Guest Editors

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Keywords

  • aquaphotomics
  • water
  • spectra
  • chemometrics
  • non-destructive measurements
  • biomeasurement
  • band assignment
  • functionality

Published Papers (22 papers)

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Editorial

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10 pages, 1537 KiB  
Editorial
Aquaphotomics—Exploring Water Molecular Systems in Nature
by Jelena Muncan and Roumiana Tsenkova
Molecules 2023, 28(6), 2630; https://doi.org/10.3390/molecules28062630 - 14 Mar 2023
Cited by 3 | Viewed by 1740
Abstract
Since its birth in 2005, when introduced by Prof [...] Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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Research

Jump to: Editorial, Review

35 pages, 7170 KiB  
Article
Aquaphotomic Study of Effects of Different Mixing Waters on the Properties of Cement Mortar
by Jelena Muncan, Satoshi Tamura, Yuri Nakamura, Mizuki Takigawa, Hisao Tsunokake and Roumiana Tsenkova
Molecules 2022, 27(22), 7885; https://doi.org/10.3390/molecules27227885 - 15 Nov 2022
Cited by 1 | Viewed by 2510
Abstract
The mixing water used for cement concrete has a significant effect on the physical properties of the material after hardening; however, other than the upper limit for the mixed impurities, not enough consideration has been given to the functions and characteristics of water [...] Read more.
The mixing water used for cement concrete has a significant effect on the physical properties of the material after hardening; however, other than the upper limit for the mixed impurities, not enough consideration has been given to the functions and characteristics of water at the molecular level. In this study, we investigated the effect of four different types of water (two spring-, mineral waters, tap water and distilled water) on the drying shrinkage of the hardened cement by comparing the material properties of the concrete specimens and analyzing the molecular structure of the water and cement mortar using aquaphotomics. The near infrared (NIR) spectra of waters used for mixing were acquired in the transmittance mode using a high-precision, high-accuracy benchtop spectrometer in the range of 400–2500 nm, with the 0.5 nm step. The NIR spectra of cement paste and mortar were measured in 6.2 nm increments in the wavelength range of 950 nm to 1650 nm using a portable spectrometer. The measurements of cement paste and mortar were performed on Day 0 (immediately after mixing, cement paste), 1 day, 3 days, 7 days, and 28 days after mixing (cement mortar). The spectral data were analyzed according to the aquaphotomics’ multivariate analysis protocol, which involved exploration of raw and preprocessed spectra, exploratory analysis, discriminating analysis and aquagrams. The results of the aquaphotomics’ analysis were interpreted together with the results of thermal and drying shrinkage measurements. Together, the findings clearly demonstrated that the thermal and drying shrinkage properties of the hardened cement material differed depending on the water used. Better mechanical properties were found to be a result of using mineral waters for cement mixing despite minute differences in the chemical content. In addition, the aquaphotomic characterization of the molecular structure of waters and cement mortar during the initial hydration reaction demonstrated the possibility to predict the characteristics of hardened cement at a very early stage. This provided the rationale to propose a novel evaluation method based on aquaphotomics for non-invasive evaluation and monitoring of cement mortar. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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21 pages, 4259 KiB  
Article
Pilot Aquaphotomic Study of the Effects of Audible Sound on Water Molecular Structure
by Aleksandar Stoilov, Jelena Muncan, Kiyoko Tsuchimoto, Nakanishi Teruyaki, Shogo Shigeoka and Roumiana Tsenkova
Molecules 2022, 27(19), 6332; https://doi.org/10.3390/molecules27196332 - 26 Sep 2022
Cited by 2 | Viewed by 4063
Abstract
Sound affects the medium it propagates through and studies on biological systems have shown various properties arising from this phenomenon. As a compressible media and a “collective mirror”, water is influenced by all internal and external influences, changing its molecular structure accordingly. The [...] Read more.
Sound affects the medium it propagates through and studies on biological systems have shown various properties arising from this phenomenon. As a compressible media and a “collective mirror”, water is influenced by all internal and external influences, changing its molecular structure accordingly. The water molecular structure and its changes can be observed as a whole by measuring its electromagnetic (EMG) spectrum. Using near-infrared spectroscopy and aquaphotomics, this pilot study aimed to better describe and understand the sound-water interaction. Results on purified and mineral waters reported similar effects from the applied 432 Hz and 440 Hz frequency sound, where significant reduction in spectral variations and increased stability in water were shown after the sound perturbation. In general, the sound rearranged the initial water molecular conformations, changing the samples’ properties by increasing strongly bound, ice-like water and decreasing small water clusters and solvation shells. Even though there was only 8 Hz difference in applied sound frequencies, the change of absorbance at water absorbance bands was specific for each frequency and also water-type-dependent. This also means that sound could be effectively used as a perturbation tool together with spectroscopy to identify the type of bio, or aqueous, samples being tested, as well as to identify and even change water functionality. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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14 pages, 3445 KiB  
Article
Water as a Probe for Standardization of Near-Infrared Spectra by Mutual–Individual Factor Analysis
by Xiaoyu Cui
Molecules 2022, 27(18), 6069; https://doi.org/10.3390/molecules27186069 - 17 Sep 2022
Cited by 1 | Viewed by 1148
Abstract
The standardization of near-infrared (NIR) spectra is essential in practical applications, because various instruments are generally employed. However, standardization is challenging due to numerous perturbations, such as the instruments, testing environments, and sample compositions. In order to explain the spectral changes caused by [...] Read more.
The standardization of near-infrared (NIR) spectra is essential in practical applications, because various instruments are generally employed. However, standardization is challenging due to numerous perturbations, such as the instruments, testing environments, and sample compositions. In order to explain the spectral changes caused by the various perturbations, a two-step standardization technique was presented in this work called mutual–individual factor analysis (MIFA). Taking advantage of the sensitivity of a water probe to perturbations, the spectral information from a water spectral region was gradually divided into mutual and individual parts. With aquaphotomics expertise, it can be found that the mutual part described the overall spectral features among instruments, whereas the individual part depicted the difference of component structural changes in the sample caused by operation and the measurement conditions. Furthermore, the spectral difference was adjusted by the coefficients in both parts. The effectiveness of the method was assessed by using two NIR datasets of corn and wheat, respectively. The results showed that the standardized spectra can be successfully predicted by using the partial least squares (PLS) models developed with the spectra from the reference instrument. Consequently, the MIFA offers a viable solution to standardize the spectra obtained from several instruments when measurements are affected by multiple factors. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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22 pages, 4215 KiB  
Article
Investigation of Water Interaction with Polymer Matrices by Near-Infrared (NIR) Spectroscopy
by Vanessa Moll, Krzysztof B. Beć, Justyna Grabska and Christian W. Huck
Molecules 2022, 27(18), 5882; https://doi.org/10.3390/molecules27185882 - 10 Sep 2022
Cited by 6 | Viewed by 2784
Abstract
The interaction of water with polymers is an intensively studied topic. Vibrational spectroscopy techniques, mid-infrared (MIR) and Raman, were often used to investigate the properties of water–polymer systems. On the other hand, relatively little attention has been given to the potential of using [...] Read more.
The interaction of water with polymers is an intensively studied topic. Vibrational spectroscopy techniques, mid-infrared (MIR) and Raman, were often used to investigate the properties of water–polymer systems. On the other hand, relatively little attention has been given to the potential of using near-infrared (NIR) spectroscopy (12,500–4000 cm−1; 800–2500 nm) for exploring this problem. NIR spectroscopy delivers exclusive opportunities for the investigation of molecular structure and interactions. This technique derives information from overtones and combination bands, which provide unique insights into molecular interactions. It is also very well suited for the investigation of aqueous systems, as both the bands of water and the polymer can be reliably acquired in a range of concentrations in a more straightforward manner than it is possible with MIR spectroscopy. In this study, we applied NIR spectroscopy to investigate interactions of water with polymers of varying hydrophobicity: polytetrafluoroethylene (PTFE), polypropylene (PP), polystyrene (PS), polyvinylchloride (PVC), polyoxymethylene (POM), polyamide 6 (PA), lignin (Lig), chitin (Chi) and cellulose (Cell). Polymer–water mixtures in the concentration range of water between 1–10%(w/w) were investigated. Spectra analysis and interpretation were performed with the use of difference spectroscopy, Principal Component Analysis (PCA), Median Linkage Clustering (MLC), Partial Least Squares Regression (PLSR), Multivariate Curve Resolution Alternating Least Squares (MCR-ALS) and Two-Dimensional Correlation Spectroscopy (2D-COS). Additionally, from the obtained data, aquagrams were constructed and interpreted with aid of the conclusions drawn from the conventional approaches. We deepened insights into the problem of water bands obscuring compound-specific signals in the NIR spectrum, which is often a limiting factor in analytical applications. The study unveiled clearly visible trends in NIR spectra associated with the chemical nature of the polymer and its increasing hydrophilicity. We demonstrated that changes in the NIR spectrum of water are manifested even in the case of interaction with highly hydrophobic polymers (e.g., PTFE). Furthermore, the unveiled spectral patterns of water in the presence of different polymers were found to be dissimilar between the two major water bands in NIR spectrum (νs + νas and νas + δ). Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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12 pages, 5434 KiB  
Article
Intermolecular Interaction of Tetrabutylammonium and Tetrabutylphosphonium Salt Hydrates by Low-Frequency Raman Observation
by Yasuhiro Miwa, Tomoki Nagahama, Harumi Sato, Atsushi Tani and Kei Takeya
Molecules 2022, 27(15), 4743; https://doi.org/10.3390/molecules27154743 - 25 Jul 2022
Cited by 3 | Viewed by 1650
Abstract
Semi-clathrate hydrates are attractive heat storage materials because the equilibrium temperatures, located above 0 °C in most cases, can be changed by selecting guest cations and anions. The equilibrium temperatures are influenced by the size and hydrophilicity of guest ions, hydration number, crystal [...] Read more.
Semi-clathrate hydrates are attractive heat storage materials because the equilibrium temperatures, located above 0 °C in most cases, can be changed by selecting guest cations and anions. The equilibrium temperatures are influenced by the size and hydrophilicity of guest ions, hydration number, crystal structure, and so on. This indicates that intermolecular and/or interionic interaction in the semi-clathrate hydrates may be related to the variation of the equilibrium temperatures. Therefore, intermolecular and/or interionic interaction in semi-clathrate hydrates with quaternary onium salts was directly observed using low-frequency Raman spectroscopy, a type of terahertz spectroscopy. The results show that Raman peak positions were mostly correlated with the equilibrium temperatures: in the semi-clathrate hydrates with higher equilibrium temperatures, Raman peaks around 65 cm−1 appeared at a higher wavenumber and the other Raman peaks at around 200 cm−1 appeared at a lower wavenumber. Low-frequency Raman observation is a valuable tool with which to study the equilibrium temperatures in semi-clathrate hydrates. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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17 pages, 3079 KiB  
Article
Performance Improvement of NIR Spectral Pattern Recognition from Three Compensation Models’ Voting and Multi-Modal Fusion
by Niangen Ye, Sheng Zhong, Zile Fang, Haijun Gao, Zhihua Du, Heng Chen, Lu Yuan and Tao Pan
Molecules 2022, 27(14), 4485; https://doi.org/10.3390/molecules27144485 - 13 Jul 2022
Cited by 3 | Viewed by 1291
Abstract
Inspired by aquaphotomics, the optical path length of measurement was regarded as a perturbation factor. Near-infrared (NIR) spectroscopy with multi-measurement modals was applied to the discriminant analysis of three categories of drinking water. Moving window-k nearest neighbor (MW-kNN) and Norris derivative filter [...] Read more.
Inspired by aquaphotomics, the optical path length of measurement was regarded as a perturbation factor. Near-infrared (NIR) spectroscopy with multi-measurement modals was applied to the discriminant analysis of three categories of drinking water. Moving window-k nearest neighbor (MW-kNN) and Norris derivative filter were used for modeling and optimization. Drawing on the idea of game theory, the strategy for two-category priority compensation and three-model voting with multi-modal fusion was proposed. Moving window correlation coefficient (MWCC), inter-category and intra-category MWCC spectra, and k-shortest distances plotting with MW-kNN were proposed to evaluate weak differences between two spectral populations. For three measurement modals (1 mm, 4 mm, and 10 mm), the optimal MW-kNN models, and two-category priority compensation models were determined. The joint models for three compensation models’ voting were established. Comprehensive discrimination effects of joint models were better than their sub-models; multi-modal fusion was better than single-modal fusion. The best joint model was the dual-modal fusion of compensation models of one- and two-category priority (1 mm), one- and three-category priority (10 mm), and two- and three-category priority (1 mm), validation’s total recognition accuracy rate reached 95.5%. It fused long-wave models (1 mm, containing 1450 nm) and short-wave models (10 mm, containing 974 nm). The results showed that compensation models’ voting and multi-modal fusion can effectively improve the performance of NIR spectral pattern recognition. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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12 pages, 2631 KiB  
Article
Changes in Water Properties in Human Tissue after Double Filtration Plasmapheresis—A Case Study
by Felix Scholkmann and Roumiana Tsenkova
Molecules 2022, 27(12), 3947; https://doi.org/10.3390/molecules27123947 - 20 Jun 2022
Cited by 2 | Viewed by 2658
Abstract
Double-filtration plasmapheresis (DFPP) is a blood cleaning technique that enables the removal of unwanted substances from the blood. In our case study, we performed near-infrared (NIR) spectroscopy measurements on the human hand tissue before and after a specific DFPP treatment (INUSpheresis with a [...] Read more.
Double-filtration plasmapheresis (DFPP) is a blood cleaning technique that enables the removal of unwanted substances from the blood. In our case study, we performed near-infrared (NIR) spectroscopy measurements on the human hand tissue before and after a specific DFPP treatment (INUSpheresis with a TKM58 filter), along with NIR measurements of the substances extracted via DFPP (eluate). The spectral data were analyzed using the aquaphotomics approach. The analysis showed that the water properties in the tissue change after DFPP treatment, i.e., an increase in small water clusters, free water molecules and a decrease in hydroxylated water as well as superoxide in hydration shells was noted. The opposite effect was observed in the eluates of both DFPP treatments. Our study is the first that documents changes in water spectral properties after DFPP treatments in human tissue. The changes in tissue water demonstrated by our case study suggest that the positive physiological effects of DFPP in general, and of INUSpheresis with the TKM58 filter in particular, may be associated with improvements in water quality in blood and tissues. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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13 pages, 2428 KiB  
Article
Increase in the Intracellular Bulk Water Content in the Early Phase of Cell Death of Keratinocytes, Corneoptosis, as Revealed by 65 GHz Near-Field CMOS Dielectric Sensor
by Keiichiro Shiraga, Yuichi Ogawa, Shojiro Kikuchi, Masayuki Amagai and Takeshi Matsui
Molecules 2022, 27(9), 2886; https://doi.org/10.3390/molecules27092886 - 30 Apr 2022
Cited by 2 | Viewed by 1817
Abstract
While bulk water and hydration water coexist in cells to support the expression of biological macromolecules, how the dynamics of water molecules, which have long been only a minor role in molecular biology research, relate to changes in cellular states such as cell [...] Read more.
While bulk water and hydration water coexist in cells to support the expression of biological macromolecules, how the dynamics of water molecules, which have long been only a minor role in molecular biology research, relate to changes in cellular states such as cell death has hardly been explored so far due to the lack of evaluation techniques. In this study, we developed a high-precision measurement system that can discriminate bulk water content changes of ±0.02% (0.2 mg/cm3) with single-cell-level spatial resolution based on a near-field CMOS dielectric sensor operating at 65 GHz. We applied this system to evaluate the temporal changes in the bulk water content during the cell death process of keratinocytes, called corneoptosis, using isolated SG1 (first layer of stratum granulosum) cells in vitro. A significant irreversible increase in the bulk water content was observed approximately 1 h before membrane disruption during corneoptosis, which starts with cytoplasmic high Ca2+ signal. These findings suggest that the calcium flux may have a role in triggering the increase in the bulk water content in SG1 cells. Thus, our near-field CMOS dielectric sensor provides a valuable tool to dissect the involvement of water molecules in the various events that occur in the cell. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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20 pages, 5882 KiB  
Article
Identification of Stingless Bee Honey Adulteration Using Visible-Near Infrared Spectroscopy Combined with Aquaphotomics
by Muna E. Raypah, Ahmad Fairuz Omar, Jelena Muncan, Musfirah Zulkurnain and Abdul Rahman Abdul Najib
Molecules 2022, 27(7), 2324; https://doi.org/10.3390/molecules27072324 - 03 Apr 2022
Cited by 12 | Viewed by 4522
Abstract
Honey is a natural product that is considered globally one of the most widely important foods. Various studies on authenticity detection of honey have been fulfilled using visible and near-infrared (Vis-NIR) spectroscopy techniques. However, there are limited studies on stingless bee honey (SBH) [...] Read more.
Honey is a natural product that is considered globally one of the most widely important foods. Various studies on authenticity detection of honey have been fulfilled using visible and near-infrared (Vis-NIR) spectroscopy techniques. However, there are limited studies on stingless bee honey (SBH) despite the increase of market demand for this food product. The objective of this work was to present the potential of Vis-NIR absorbance spectroscopy for profiling, classifying, and quantifying the adulterated SBH. The SBH sample was mixed with various percentages (10–90%) of adulterants, including distilled water, apple cider vinegar, and high fructose syrup. The results showed that the region at 400–1100 nm that is related to the color and water properties of the samples was effective to discriminate and quantify the adulterated SBH. By applying the principal component analysis (PCA) on adulterants and honey samples, the PCA score plot revealed the classification of the adulterants and adulterated SBHs. A partial least squares regression (PLSR) model was developed to quantify the contamination level in the SBH samples. The general PLSR model with the highest coefficient of determination and lowest root means square error of cross-validation (RCV2=0.96 and RMSECV=5.88 %) was acquired. The aquaphotomics analysis of adulteration in SBH with the three adulterants utilizing the short-wavelength NIR region (800–1100 nm) was presented. The structural changes of SBH due to adulteration were described in terms of the changes in the water molecular matrix, and the aquagrams were used to visualize the results. It was revealed that the integration of NIR spectroscopy with aquaphotomics could be used to detect the water molecular structures in the adulterated SBH. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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17 pages, 24204 KiB  
Article
Aquaphotomic, E-Nose and Electrolyte Leakage to Monitor Quality Changes during the Storage of Ready-to-Eat Rocket
by Laura Marinoni, Marina Buccheri, Giulia Bianchi and Tiziana M. P. Cattaneo
Molecules 2022, 27(7), 2252; https://doi.org/10.3390/molecules27072252 - 30 Mar 2022
Cited by 6 | Viewed by 2149
Abstract
The consumption of ready-to-eat (RTE) leafy vegetables has increased rapidly due to changes in consumer diet. RTE products are perceived as fresh, high-quality, and health-promoting. The monitoring of the RTE quality is crucial in relation to safety issues. This study aimed to evaluate [...] Read more.
The consumption of ready-to-eat (RTE) leafy vegetables has increased rapidly due to changes in consumer diet. RTE products are perceived as fresh, high-quality, and health-promoting. The monitoring of the RTE quality is crucial in relation to safety issues. This study aimed to evaluate the maintenance of RTE rocket salad freshness packed under modified atmospheres. A portable E-nose, the electrolyte leakage test (which measures the index of leaf damage—ILD), and NIR spectroscopy and Aquaphotomics were employed. Two trials were carried out, using the following gas mixtures: (A) atmospheric air (21% O2, 78% N2); (B) 30% O2, 70% N2; (C) 10% CO2, 5% O2, 85% N2. Samples were stored at 4 °C and analyzed at 0, 1, 4, 7, 11, and 13 days. ANOVA, PCA, PLS were applied for data processing. E-nose and ILD results identified the B atmosphere as the best for maintaining product freshness. NIR spectroscopy was able to group the samples according to the storage time. Aquaphotomics proved to be able to detect changes in the water structure during storage. These preliminary data showed a good agreement NIR/ILD suggesting the use of NIR for non-destructive monitoring of the damage to the plant membranes of RTE rocket salad. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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9 pages, 3314 KiB  
Article
Analysis of Vicinal Water in Soft Contact Lenses Using a Combination of Infrared Absorption Spectroscopy and Multivariate Curve Resolution
by Shoichi Maeda, Shunta Chikami, Glenn Villena Latag, Subin Song, Norio Iwakiri and Tomohiro Hayashi
Molecules 2022, 27(7), 2130; https://doi.org/10.3390/molecules27072130 - 25 Mar 2022
Cited by 1 | Viewed by 2878
Abstract
In this paper, we propose a new spectroscopic method to explore the behavior of molecules near polymeric molecular networks of water-containing soft materials such as hydrogels. We demonstrate the analysis of hydrogen bonding states of water in the vicinity of hydrogels (soft contact [...] Read more.
In this paper, we propose a new spectroscopic method to explore the behavior of molecules near polymeric molecular networks of water-containing soft materials such as hydrogels. We demonstrate the analysis of hydrogen bonding states of water in the vicinity of hydrogels (soft contact lenses). In this method, we apply force to hydrated contact lenses to deform them and to modulate the ratio between the signals from bulk and vicinal regions. We then collect spectra at different forces. Finally, we extracted the spectra of the vicinal region using the multivariate curve resolution-alternating least square (MCR-ALS) method. We report the hydration states depending on the chemical structures of hydrogels constituting the contact lenses. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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16 pages, 3474 KiB  
Article
Revealing the Effect of Heat Treatment on the Spectral Pattern of Unifloral Honeys Using Aquaphotomics
by Zsanett Bodor, Csilla Benedek, Balkis Aouadi, Viktoria Zsom-Muha and Zoltan Kovacs
Molecules 2022, 27(3), 780; https://doi.org/10.3390/molecules27030780 - 25 Jan 2022
Cited by 6 | Viewed by 2816
Abstract
In this study we aimed to investigate the effect of heat treatment on the spectral pattern of honey using near infrared spectroscopy (NIRS). For the research, sunflower, bastard indigo, and acacia honeys were collected from entrusted beekeepers. The honeys were not subject to [...] Read more.
In this study we aimed to investigate the effect of heat treatment on the spectral pattern of honey using near infrared spectroscopy (NIRS). For the research, sunflower, bastard indigo, and acacia honeys were collected from entrusted beekeepers. The honeys were not subject to any treatment before. Samples were treated at 40 °C, 60 °C, 80 °C, and 100 °C for 60, 120, 180, and 240 min. This resulted in 17 levels, including the untreated control samples. The 5-hydroxymethylfurfural (HMF) content of the honeys was determined using the Winkler method. NIRS spectra were recorded using a handheld instrument. Data analysis was performed using ANOVA for the HMF content and multivariate analysis for the NIRS data. For the latter, PCA, PCA-LDA, and PLSR models were built (using the 1300–1600 nm spectral range) and the wavelengths presenting the greatest change induced by the perturbations of temperature and time intervals were collected systematically, based on the difference spectra and the weights of the models. The most contributing wavelengths were used to visualize the spectral pattern changes on the aquagrams in the specific water matrix coordinates. Our results showed that the heat treatment highly contributed to the formation of free or less bonded water, however, the changes in the spectral pattern highly depended on the crystallization phase and the honey type. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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18 pages, 3097 KiB  
Article
Aquaphotomics Research of Cold Stress in Soybean Cultivars with Different Stress Tolerance Ability: Early Detection of Cold Stress Response
by Jelena Muncan, Balasooriya Mudiyanselage Siriwijaya Jinendra, Shinichiro Kuroki and Roumiana Tsenkova
Molecules 2022, 27(3), 744; https://doi.org/10.3390/molecules27030744 - 24 Jan 2022
Cited by 8 | Viewed by 4827
Abstract
The development of non-destructive methods for early detection of cold stress of plants and the identification of cold-tolerant cultivars is highly needed in crop breeding programs. Current methods are either destructive, time-consuming or imprecise. In this study, soybean leaves’ spectra were acquired in [...] Read more.
The development of non-destructive methods for early detection of cold stress of plants and the identification of cold-tolerant cultivars is highly needed in crop breeding programs. Current methods are either destructive, time-consuming or imprecise. In this study, soybean leaves’ spectra were acquired in the near infrared (NIR) range (588–1025 nm) from five cultivars genetically engineered to have different levels of cold stress tolerance. The spectra were acquired at the optimal growing temperature 27 °C and when the temperature was decreased to 22 °C. In this paper, we report the results of the aquaphotomics analysis performed with the objective of understanding the role of the water molecular system in the early cold stress response of all cultivars. The raw spectra and the results of Principal Component Analysis, Soft Independent Modeling of Class Analogies and aquagrams showed consistent evidence of huge differences in the NIR spectral profiles of all cultivars under normal and mild cold stress conditions. The SIMCA discrimination between the plants before and after stress was achieved with 100% accuracy. The interpretation of spectral patterns before and after cold stress revealed major changes in the water molecular structure of the soybean leaves, altered carbohydrate and oxidative metabolism. Specific water molecular structures in the leaves of soybean cultivars were found to be highly sensitive to the temperature, showing their crucial role in the cold stress response. The results also indicated the existence of differences in the cold stress response of different cultivars, which will be a topic of further research. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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11 pages, 5444 KiB  
Article
Raman Spectroscopy-Based Assessment of the Liquid Water Content in Snow
by Ettore Maggiore, Matteo Tommasini and Paolo Maria Ossi
Molecules 2022, 27(3), 626; https://doi.org/10.3390/molecules27030626 - 19 Jan 2022
Cited by 4 | Viewed by 1627
Abstract
In snow, water coexists in solid, liquid and vapor states. The relative abundance of the three phases drives snow grain metamorphism and affects the physical properties of the snowpack. Knowledge of the content of the liquid phase in snow is critical to estimate [...] Read more.
In snow, water coexists in solid, liquid and vapor states. The relative abundance of the three phases drives snow grain metamorphism and affects the physical properties of the snowpack. Knowledge of the content of the liquid phase in snow is critical to estimate the snowmelt runoff and to forecast the release of wet avalanches. Liquid water does not spread homogeneously through a snowpack because different snow layers have different permeabilities; therefore, it is important to track sudden changes in the amount of liquid water within a specific layer. We reproduced water percolation in the laboratory, and used Raman spectroscopy to detect the presence of the liquid phase in controlled snow samples. We performed experiments on both fine- and coarse-grained snow. The obtained snow spectra are well fitted by a linear combination of the spectra typical of liquid water and ice. We progressively charged snow with liquid water from dry snow up to soaked snow. As a result, we exploited continuous, qualitative monitoring of the evolution of the liquid water content as reflected by the fitting coefficient c. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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13 pages, 1174 KiB  
Article
Bovine Respiratory Syncytial Virus (BRSV) Infection Detected in Exhaled Breath Condensate of Dairy Calves by Near-Infrared Aquaphotomics
by Mariana Santos-Rivera, Amelia R. Woolums, Merrilee Thoresen, Florencia Meyer and Carrie K. Vance
Molecules 2022, 27(2), 549; https://doi.org/10.3390/molecules27020549 - 16 Jan 2022
Cited by 8 | Viewed by 2257
Abstract
Bovine respiratory syncytial virus (BRSV) is a major contributor to respiratory disease in cattle worldwide. Traditionally, BRSV infection is detected based on non-specific clinical signs, followed by reverse transcriptase-polymerase chain reaction (RT-PCR), the results of which can take days to obtain. Near-infrared aquaphotomics [...] Read more.
Bovine respiratory syncytial virus (BRSV) is a major contributor to respiratory disease in cattle worldwide. Traditionally, BRSV infection is detected based on non-specific clinical signs, followed by reverse transcriptase-polymerase chain reaction (RT-PCR), the results of which can take days to obtain. Near-infrared aquaphotomics evaluation based on biochemical information from biofluids has the potential to support the rapid identification of BRSV infection in the field. This study evaluated NIR spectra (n = 240) of exhaled breath condensate (EBC) from dairy calves (n = 5) undergoing a controlled infection with BRSV. Changes in the organization of the aqueous phase of EBC during the baseline (pre-infection) and infected (post-infection and clinically abnormal) stages were found in the WAMACS (water matrix coordinates) C1, C5, C9, and C11, likely associated with volatile and non-volatile compounds in EBC. The discrimination of these chemical profiles by PCA-LDA models differentiated samples collected during the baseline and infected stages with an accuracy, sensitivity, and specificity >93% in both the calibration and validation. Thus, biochemical changes occurring during BRSV infection can be detected and evaluated with NIR-aquaphotomics in EBC. These findings form the foundation for developing an innovative, non-invasive, and in-field diagnostic tool to identify BRSV infection in cattle. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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15 pages, 4361 KiB  
Article
Correction of Temperature Variation with Independent Water Samples to Predict Soluble Solids Content of Kiwifruit Juice Using NIR Spectroscopy
by Harpreet Kaur, Rainer Künnemeyer and Andrew McGlone
Molecules 2022, 27(2), 504; https://doi.org/10.3390/molecules27020504 - 14 Jan 2022
Cited by 7 | Viewed by 2509
Abstract
Using the framework of aquaphotomics, we have sought to understand the changes within the water structure of kiwifruit juice occurring with changes in temperature. The study focuses on the first (1300–1600 nm) and second (870–1100 nm) overtone regions of the OH stretch of [...] Read more.
Using the framework of aquaphotomics, we have sought to understand the changes within the water structure of kiwifruit juice occurring with changes in temperature. The study focuses on the first (1300–1600 nm) and second (870–1100 nm) overtone regions of the OH stretch of water and examines temperature differences between 20, 25, and 30 °C. Spectral data were collected using a Fourier transform–near-infrared spectrometer with 1 mm and 10 mm transmission cells for measurements in the first and second overtone region, respectively. Water wavelengths affected by temperature variation were identified. Aquagrams (water spectral patterns) highlight slightly different responses in the first and second overtone regions. The influence of increasing temperature on the peak absorbance of the juice was largely a lateral wavelength shift in the first overtone region and a vertical amplitude shift in the second overtone region of water. With the same data set, we investigated the use of external parameter orthogonalisation (EPO) and extended multiple scatter correction (EMSC) pre-processing to assist in building temperature-independent partial least square regression models for predicting soluble solids concentration (SSC) of kiwifruit juice. The interference component selected for correction was the first principal component loading measured using pure water samples taken at the same three temperatures (20, 25, and 30 °C). The results show that the EMSC method reduced SSC prediction bias from 0.77 to 0.1 °Brix in the first overtone region of water. Using the EPO method significantly reduced the prediction bias from 0.51 to 0.04 °Brix, when applying a model made at one temperature (30 °C) to measurements made at another temperature (20 °C) in the second overtone region of water. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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11 pages, 2137 KiB  
Article
Interactions of Linearly Polarized and Unpolarized Light on Kiwifruit Using Aquaphotomics
by Damenraj Rajkumar, Rainer Künnemeyer, Harpreet Kaur, Jevon Longdell and Andrew McGlone
Molecules 2022, 27(2), 494; https://doi.org/10.3390/molecules27020494 - 13 Jan 2022
Cited by 2 | Viewed by 3087
Abstract
Near infrared (NIR) spectroscopy is an important tool for predicting the internal qualities of fruits. Using aquaphotomics, spectral changes between linearly polarized and unpolarized light were assessed on 200 commercially grown yellow-fleshed kiwifruit (Actinidia chinensis var. chinensis ‘Zesy002’). Measurements were performed on [...] Read more.
Near infrared (NIR) spectroscopy is an important tool for predicting the internal qualities of fruits. Using aquaphotomics, spectral changes between linearly polarized and unpolarized light were assessed on 200 commercially grown yellow-fleshed kiwifruit (Actinidia chinensis var. chinensis ‘Zesy002’). Measurements were performed on different configurations of unpeeled (intact) and peeled (cut) kiwifruit using a commercial handheld NIR instrument. Absorbance after applying standard normal variate (SNV) and second derivative Savitzky–Golay filters produced different spectral features for all configurations. An aquagram depicting all configurations suggests that linearly polarized light activated more free water states and unpolarized light activated more bound water states. At depth (≥1 mm), after several scattering events, all radiation is expected to be fully depolarized and interactions for incident polarized or unpolarized light will be similar, so any observed differences are attributable to the surface layers of the fruit. Aquagrams generated in terms of the fruit soluble solids content (SSC) were similar for all configurations, suggesting the SSC in fruit is not a contributing factor here. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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14 pages, 3897 KiB  
Article
NIRS and Aquaphotomics Trace Robusta-to-Arabica Ratio in Liquid Coffee Blends
by Balkis Aouadi, Flora Vitalis, Zsanett Bodor, John-Lewis Zinia Zaukuu, Istvan Kertesz and Zoltan Kovacs
Molecules 2022, 27(2), 388; https://doi.org/10.3390/molecules27020388 - 08 Jan 2022
Cited by 4 | Viewed by 2105
Abstract
Coffee is both a vastly consumed beverage and a chemically complex matrix. For a long time, an arduous chemical analysis was necessary to resolve coffee authentication issues. Despite their demonstrated efficacy, such techniques tend to rely on reference methods or resort to elaborate [...] Read more.
Coffee is both a vastly consumed beverage and a chemically complex matrix. For a long time, an arduous chemical analysis was necessary to resolve coffee authentication issues. Despite their demonstrated efficacy, such techniques tend to rely on reference methods or resort to elaborate extraction steps. Near infrared spectroscopy (NIRS) and the aquaphotomics approach, on the other hand, reportedly offer a rapid, reliable, and holistic compositional overview of varying analytes but with little focus on low concentration mixtures of Robusta-to-Arabica coffee. Our study aimed for a comparative assessment of ground coffee adulteration using NIRS and liquid coffee adulteration using the aquaphotomics approach. The aim was to demonstrate the potential of monitoring ground and liquid coffee quality as they are commercially the most available coffee forms. Chemometrics spectra analysis proved capable of distinguishing between the studied samples and efficiently estimating the added Robusta concentrations. An accuracy of 100% was obtained for the varietal discrimination of pure Arabica and Robusta, both in ground and liquid form. Robusta-to-Arabica ratio was predicted with R2CV values of 0.99 and 0.9 in ground and liquid form respectively. Aquagrams results accentuated the peculiarities of the two coffee varieties and their respective blends by designating different water conformations depending on the coffee variety and assigning a particular water absorption spectral pattern (WASP) depending on the blending ratio. Marked spectral features attributed to high hydrogen bonded water characterized Arabica-rich coffee, while those with the higher Robusta content showed an abundance of free water structures. Collectively, the obtained results ascertain the adequacy of NIRS and aquaphotomics as promising alternative tools for the authentication of liquid coffee that can correlate the water-related fingerprint to the Robusta-to-Arabica ratio. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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Review

Jump to: Editorial, Research

18 pages, 6391 KiB  
Review
Preprocessing NIR Spectra for Aquaphotomics
by Jean-Michel Roger, Alexandre Mallet and Federico Marini
Molecules 2022, 27(20), 6795; https://doi.org/10.3390/molecules27206795 - 11 Oct 2022
Cited by 12 | Viewed by 2065
Abstract
Even though NIR spectroscopy is based on the Beer–Lambert law, which clearly relates the concentration of the absorbing elements with the absorbance, the measured spectra are subject to spurious signals, such as additive and multiplicative effects. The use of NIR spectra, therefore, requires [...] Read more.
Even though NIR spectroscopy is based on the Beer–Lambert law, which clearly relates the concentration of the absorbing elements with the absorbance, the measured spectra are subject to spurious signals, such as additive and multiplicative effects. The use of NIR spectra, therefore, requires a preprocessing step. This article reviews the main preprocessing methods in the light of aquaphotomics. Simple methods for visualizing the spectra are proposed in order to guide the user in the choice of the best preprocessing. The most common chemometrics preprocessing are presented and illustrated by three real datasets. Some preprocessing aims to produce a spectrum as close as possible to the absorbance that would have been measured under ideal conditions and is very useful for the establishment of an aquagram. Others, dedicated to the improvement of the resolution of the spectra, are very useful for the identification of the peaks. Finally, special attention is given to the problem of reducing multiplicative effects and to the potential pitfalls of some very popular methods in chemometrics. Alternatives proposed in recent papers are presented. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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19 pages, 1507 KiB  
Review
Water as a Link between Membrane and Colloidal Theories for Cells
by E. Anibal Disalvo, A. Sebastian Rosa, Jimena P. Cejas and María de los A. Frias
Molecules 2022, 27(15), 4994; https://doi.org/10.3390/molecules27154994 - 05 Aug 2022
Cited by 3 | Viewed by 2302
Abstract
This review is an attempt to incorporate water as a structural and thermodynamic component of biomembranes. With this purpose, the consideration of the membrane interphase as a bidimensional hydrated polar head group solution, coupled to the hydrocarbon region allows for the reconciliation of [...] Read more.
This review is an attempt to incorporate water as a structural and thermodynamic component of biomembranes. With this purpose, the consideration of the membrane interphase as a bidimensional hydrated polar head group solution, coupled to the hydrocarbon region allows for the reconciliation of two theories on cells in dispute today: one considering the membrane as an essential part in terms of compartmentalization, and another in which lipid membranes are not necessary and cells can be treated as a colloidal system. The criterium followed is to describe the membrane state as an open, non-autonomous and responsive system using the approach of Thermodynamic of Irreversible Processes. The concept of an open/non-autonomous membrane system allows for the visualization of the interrelationship between metabolic events and membrane polymorphic changes. Therefore, the Association Induction Hypothesis (AIH) and lipid properties interplay should consider hydration in terms of free energy modulated by water activity and surface (lateral) pressure. Water in restricted regions at the lipid interphase has thermodynamic properties that explain the role of H-bonding networks in the propagation of events between membrane and cytoplasm that appears to be relevant in the context of crowded systems. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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11 pages, 1209 KiB  
Review
Chemometrics: An Excavator in Temperature-Dependent Near-Infrared Spectroscopy
by Yan Sun, Wensheng Cai and Xueguang Shao
Molecules 2022, 27(2), 452; https://doi.org/10.3390/molecules27020452 - 11 Jan 2022
Cited by 12 | Viewed by 4532
Abstract
Temperature-dependent near-infrared (NIR) spectroscopy has been developed and taken as a powerful technique for analyzing the structure of water and the interactions in aqueous systems. Due to the overlapping of the peaks in NIR spectra, it is difficult to obtain the spectral features [...] Read more.
Temperature-dependent near-infrared (NIR) spectroscopy has been developed and taken as a powerful technique for analyzing the structure of water and the interactions in aqueous systems. Due to the overlapping of the peaks in NIR spectra, it is difficult to obtain the spectral features showing the structures and interactions. Chemometrics, therefore, is adopted to improve the spectral resolution and extract spectral information from the temperature-dependent NIR spectra for structural and quantitative analysis. In this review, works on chemometric studies for analyzing temperature-dependent NIR spectra were summarized. The temperature-induced spectral features of water structures can be extracted from the spectra with the help of chemometrics. Using the spectral variation of water with the temperature, the structural changes of small molecules, proteins, thermo-responsive polymers, and their interactions with water in aqueous solutions can be demonstrated. Furthermore, quantitative models between the spectra and the temperature or concentration can be established using the spectral variations of water and applied to determine the compositions in aqueous mixtures. Full article
(This article belongs to the Special Issue Aquaphotomics - Exploring Water Molecular Systems in Nature)
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