COVID-19 has affected the entire world due to the rapid spread of SARS-CoV-2, mainly through airborne particles from saliva, which, being easily obtained, help monitor the progression of the disease. ...Fourier transform infrared (FTIR) spectra combined with chemometric analysis could increase the diagnostic efficiency of the disease. However, two-dimensional correlation spectroscopy (2DCOS) is superior to conventional spectra as it helps to resolve the minute overlapped peaks. In this work, we aimed to use 2DCOS and receiver operating characteristic (ROC) analyses to compare the immune response in saliva associated with COVID-19, which could be important in biomedical diagnosis. FTIR spectra of human saliva samples from male (575) and female (366) patients ranging from 20 to 85 ± 2 years of age were used for the study. Age groups were segregated as G1 (20–40 ± 2 years), G2 (45–60 ± 2 years), and G3 (65–85 ± 2 years). The results of the 2DCOS analysis showed biomolecular changes in response to SARS-CoV-2. 2DCOS analyses of the male G1 + (1579,1644) and -(1531,1598) cross peaks evidenced changes such as amide I > IgG. Female G1 cross peaks -(1504,1645), (1504,1545) and -(1391,1645) resulted in amide I > IgG > IgM. The asynchronous spectra in 1300–900 cm-1 of the G2 male group showed that IgM is more important in diagnosing infections than IgA. Female G2 asynchronous spectra -(1027,1242) and + (1068,1176) showed that IgA > IgM is produced against SARS-CoV-2. The G3 male group evidenced antibody changes in IgG > IgM. The absence of IgM in the female G3 population diagnoses a specifically targeted immunoglobulin associated with sex. Moreover, ROC analysis showed sensitivity (85–89 % men; 81–88 % women) and specificity (90–93 % men; 78–92 % women) for the samples studied. The general classification performance (F1 score) of the studied samples is high for the male (88–91 %) and female (80–90 %) populations. This high PPV (positive predictive value) and NPV (negative predictive value) verify our segregation of COVID-19 positive and negative sample groups. Therefore, 2DCOS with ROC analysis using FTIR spectra have the potential for a non-invasive approach to monitoring COVID-19.
•2DCOS analysis showed biomolecular changes in response to SARS-CoV-2.•2DCOS analyses of the male G1 evidenced changes such as amide I > IgG.•Asynchronous spectra in 1300–900 cm−1 of the G2 male group showed that IgM is more important in diagnosing infections.•Absence of IgM in the female G3 population diagnoses a specifically targeted immunoglobulin associated with sex.•2DCOS with ROC analysis have the potential for a non-invasive approach to monitoring COVID-19.
The chemical composition and structure of the stratum corneum (SC) play a crucial role in the skin barrier function. Therefore, accurately determining the SC thickness and studying the changes in ...lipid and keratin structure and distribution within it are key aspects of skin barrier research. Currently, there are limited analytical tools and data analysis methods available for real-time and online studies of SC composition and structural changes. In this study, we focus on depth as a perturbation and employ confocal Raman microscopy combined with moving-window two-dimensional correlation spectroscopy (MW2D) technique to investigate the SC thickness. Additionally, we employ confocal Raman microscopy combined with perturbation-correlation moving-window two-dimensional correlation spectroscopy (PCMW2D) to precisely characterize the stratification of the SC. Furthermore, the two-dimensional correlation spectroscopy (2DCOS) method is utilized to examine the content of various conformations in the keratin secondary structure within the SC, as well as the subtle interrelationships between lipid and keratin structures.
2DCOS analysis of dynamic spectra, which can be approximated in the form of a polynomial function by the least squares curve fitting method, is carried out. Curve fitting provides a practical way of ...condensing a large spectral dataset in terms of a small number of fitting parameters and filtering out noise and superfluous spectral intensity variations from the raw spectra. Pertinent features of the findings are illustrated by using a simple simulated spectral data subjected to curve fitting with polynomials. Closed-form analytical expressions for 2D correlation spectra are obtained from the polynomial functions used for the curve fitting and their Hilbert transform counterpart. Such analytical expressions provide useful insight into the inner working of 2DCOS analysis, especially the role of slope and curvature of spectral intensity variations, in determining the signs of cross peaks used in the interpretation of 2D spectra.
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•2DCOS analysis of polynomials is explored.•Raw spectra may be converted to polynomials by curve fitting.•Analytical expressions for 2D correlation spectra in the closed form.•Insight into the role of trends and curvatures of dynamic spectra.
Dissolved organic matter (DOM) with complex functional groups affects the trace of binding and transformation of hexavalent chromium (Cr(VI)) in the environment. However, the mechanisms and ...quantitative indicators are still ambiguous. In this study, the perspectives of spectroscopy with synchronous and excitation-emission matrix (EEM) fluorescence, and ultraviolet-visible (UV–vis) were employed to probe the interaction of DOM and Cr(VI). The spectroscopic parameters with Dslope240–280 (the slope of the log-transformed absorbance in the range of 240–280 nm), DSlope325–375 (the slope of the log-transformed absorbance in the range of 325–375 nm), SR (the ratio of the slope of the log-transformed absorption coefficient with 275–295 nm to 350–400 nm), SFI (specific fluorescence intensities), AvgFI/AvgUVA (the ratio of average fluorescence to average UV), and SS (Stokes shift) of UV–vis and fluorescence were extracted to characterize the DOM properties. The UV–vis results showed carboxylic-like and total phenolic/carboxylic-like groups were contributed to the complexation of Cr, which resulted in forming macromolecular aggregates, however, the degree of participation of different functional groups was uneven and the binding sequence depended on the types of fractions especially the ratio of protein. Meanwhile, the EEM results proved interaction between DOM and Cr also affected the hydrophobicity and quantum yield of solutions. In addition, according to the change orders of substances and functional groups by Two-dimensional correlation spectroscopy (2DCOS) analysis, aromatic amino acids substances were much more sensitive binding onto Cr than fulvic-like fractions and humic-like fractions, and the mechanisms for Cr(VI) retention were developed. Statistical analysis results showed that SR and SFI were significantly correlated with the concentration of Cr(VI), and multiple linear regression models were developed to predict concentrations of Cr(VI). Moreover, it was found the goodness of fit of SFI was better than that of SR at low Cr concentrations, but opposite at high concentrations.
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•Aromatic amino acids were much more sensitive binding onto Cr than fulvic and humic-like.•The binding sequence of functional groups depended on the proportion of protein.•Models for predict concentrations of Cr(VI) with SFI and SR were established.•SFI fitting was more suitable than SR at low concentration, but opposite at high.
Based on the systematic analysis of heartwood and alcohol extractives of D. ebenum, D. philippinensis and D. celebica by the three-step infrared spectroscopy (FT-IR, SD-IR and 2DCOS-IR), the three ...similar Diospyros wood are successful distinguished. In FT-IR spectra, the principal chemical components of heartwood are characterized for cellulose (the bands at around ∼1370, ∼1158, ∼1034 and ∼895 cm−1), lignin (the bands around ∼2935, ∼1510, ∼1462 and ∼1426 cm−1) and calcium oxalate (peaks at ∼1615, ∼1318 and ∼781 cm−1). The correlation coefficient among samples and standard material give the result that D. ebenum is lignin-rich and D. celebica is resin-rich, while D. philippinensis contains more calcium oxalate. In SD-IR spectra, D. philippinensis and D. celebica have peaks at 1731 cm−1 mean they contain more resin. Besides, the alcohol extracts of D. ebenum possesses stronger peak at 1651, 1632, 1584 and 1388 cm−1 which can be characterized for naphthalene derivatives component. Through the 2DCOS-IR synchronous spectra, the C–H of lignin (the auto peaks at ∼1450 and ∼1460 cm−1) of three heartwoods show strong intensity. Lignin shows high thermal sensitivity in D. ebenum, while it is similar sensitive with cellulose in D. philippinensis, but it is slightly lower thermal perturbation than cellulose in D. celebica.
Meanwhile, the thermal sensitivity of Si–O and Si–C of alcohol extractives are different in the range of 935–1255 cm−1. In addition, the difference in thermal perturbation of CO and CN of resin and naphthalene derivatives could also be considered as the key factors to discriminate them. This research demonstrated that the FT-IR and 2DCOS-IR could analyze and discriminate confused ebony wood comprehensively.
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•D. ebenum is lignin-rich and D. philippinensis contains more calcium oxalate.•The C–H of lignin of three heartwoods show dominant intensity in 2DCOS-IR spectra.•There are naphthalene derivatives component in alcohol extractives.•The thermal sensitivity of CO and CN of naphthalene derivatives is different.
Two-dimensional correlation spectroscopy (2DCOS) without a priori knowledge of meaningful spectral sampling order is considered. Construction of synchronous 2D correlation spectrum does not require ...the knowledge of sampling order, and disrelation spectrum derived from synchronous spectrum possesses useful features similar to those of asynchronous spectrum. Disrelation analysis may provide enhanced spectral resolution and distinction of bands arising from different sources but not the sequential order of intensity variations. Dataset sampled in an arbitrary or scrambled order may be reassembled into a more structured form by rank ordering the spectra with the intensity of a select band. If there is no meaningful data structure, asynchronous 2D correlation should not be attempted, although synchronous and disrelation spectra may still be useful. The intrinsic ambiguity in the direction of sampling order may sometimes be resolved using additional physical information known about the sample system.
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•Data without prior knowledge of sampling order may be analyzed using synchronous correlation and disrelation spectra.•Disrelation spectrum for enhanced spectral resolution and distinction or classification of bands from different sources.•Dataset may sometimes be reassembled in a structured form for standard 2DCOS using the ranking of select band intensity.
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•The applications of IR for identification different processed products of SZ.•The effectiveness of 2DCOS in qualitative and quantitative analysis.•Different processed products can be ...identified by 2DCOS synchronous spectroscopy.•5-HMF can be accurately predicted by the 2DCOS variable selection method.
The fruit of Crataegus sp. is known as “Shanzha (SZ)” in China and is widely used in the food, beverage, and traditional Chinese medicine (TCM) industries. SZ usually requires thermal processing to reduce the irritation of its acidity to the gastric mucosa. Different processed products of SZ resulting from thermal processing have different or even opposite functions in clinical applications. In addition, 5-hydroxymethylfurfural (5-HMF) intermediates produced during thermal processing are carcinogenic to humans. Therefore, the aim of this study was to explore a rapid and accurate method by Fourier transform infrared spectroscopy (FT-IR) for the identification of different processed products and the determination of 5-HMF in extracts. In qualitative identification, a three-stage infrared spectroscopy identification method (raw spectra, the second derivative spectra, and two-dimensional correlation (2DCOS) spectra) was developed to distinguish different processed products of SZ step by step. In quantitative determination, partial least squares regression combined with different variable selection methods, especially the 2DCOS method, was applied to determine the 5-HMF content. The results show that temperature-induced 2DCOS synchronous spectra can effectively identify different processed products of SZ by shape, intensity, and position of auto-peaks or cross-peaks, and the variables selected by power spectra from concentration-induced 2DCOS synchronous spectra have better prediction ability for 5-HMF compared to full variables. The above results demonstrate that 2D-COS analysis is a potential tool in qualitative and quantitative analysis, which can improve sample identification accuracy and determination capabilities. This study not only establishes a rapid and accurate method for the identification of different processed products but also provides a practical reference for food safety and the efficient use of TCM.
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•NIR spectroscopy was evaluated to monitor the drying process of Kakadu plum.•2 dimensional spectroscopy was utilised to interpret the NIR spectra.•Freeze dried samples had similar ...moisture content compared with oven dry.
The effect of drying (oven and freeze-drying) and the addition of maltodextrin as a carrier to Kakadu plum (Terminalia ferdinandiana) puree powder samples were evaluated using a combination of two dimensional (2DCOS) and near infrared (NIR) spectroscopy. Fruit powder samples were obtained from an experiment where oven and freeze-drying methods were compared together with the addition of seven levels of maltodextrin to the samples (control, 5, 7.5, 10, 15, 20 and 25% w/w). Samples were scanned using a FT-NIR instrument (Tango, Bruker, Germany) and data analysed using 2DCOS. Asynchronous and synchronous 2DCOS spectroscopy were used to analyse and interpret the effects of the method of drying and the addition of maltodextrin on the NIR spectra of the fruit samples. The utilization of 2DCOS combined with NIR spectroscopy showed how the drying method affect the NIR spectra and thus the main implications of developing an effective, quick, and easy to use protocol for determining the drying method.
Dissolved organic matter (DOM) which can help the transportation of nutrients and pollutants plays essential role in the aquatic ecosystems. However, the dynamics of individual DOM component under ...the change of latitude have not been elucidated to date. The composition and dynamics of DOM were assessed in this study. Two individual parallel factor analysis (PARAFAC) components were found in each sampling site in Heilongjiang. To further characterize the inner change of the identified PARAFAC components, two-latitude correlation spectroscopy (2DCOS) technique was applied to the excitation loadings data. Interestingly, not all the fluorophore in a PARAFAC component change in the same direction as the overall change of a component. From upstream to downstream, the peak A1 in PARAFAC component C1 showed a downward trend, but peak A2 presented an upward trend. In PARAFAC component C2, the peak T2 and peak T3 showed an inverse changing trend under latitude perturbation. Furthermore, basic nutrients parameters in Heilongjiang were also characterized in each sampling sites. The relationships between DOM and nutrients showed that component C1 made a significant contribution to chemical oxygen demand (COD) and biochemical oxygen demand (BOD5). The evolutions of DOM peak A1 and peak A2 were accompanied by the changing of Total phosphorus (TP). The findings in this study could make a contribution to explore the fate of DOM in high humic-like substance containing river.
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•ResNet model does not need complex data processing.•ResNet model was used to accurately identify 622 fruiting bodies of bolete.•Synchronous 2DCOS spectral model has good ...discrimination performance.•ResNet model has good performance and does not have the problem of over fitting.
Food safety is an important topic of social concern. There are many species of bolete on the market, and shoddy products often occur. This phenomenon not only disrupts the market order, infringes on the rights and interests of consumers, and even endangers the lives of consumers. Therefore, it is of great significance to find a comprehensive, efficient and modern technology to identify and evaluate it in order to ensure its quality and safety. Spectroscopy analysis is fast, nondestructive and green. In our research, a fast and reliable bolete species identification method was established by combining Fourier transform near infrared spectroscopy (FT-NIR) with random forest (RF) method. In order to adapt to the development of the times, a practical method beyond traditional spectral analysis is established. Therefore, we establish a residual convolution neural network model (ResNet). The results show that the classification accuracy of the model is low and the out of bag error (OOB) error is high. After data preprocessing, the accuracy of RF model can be significantly improved. ResNet model has absolute advantages in bolete species identification. It is hardly affected by factors such as data type and sample size. Its overall recognition ability is obviously better than RF model. By comparing the identification accuracy and market application prospect of the two models, this research believes that ResNet model is more suitable for the identification of bolete species. In addition, the method can also be extended to the further study of other food, medicinal plants and agricultural products.
