Second Derivative Infrared Spectra Research Articles

One-dimensional convolutional neural networks with infrared spectroscopy for classifying the origin of printing paper

Herein, the challenge of accurately classifying the manufacturing origin of printing paper, including continent, country, and specific product, was addressed. One-dimensional convolutional neural network (1D CNN) models trained on infrared (IR) spectrum data acquired from printing paper samples were used for the task. The preprocessing of the IR spectra through a second-derivative transformation and the restriction of the spectral range to 1800 to 1200 cm-1 improved the classification performance of the model. The outcomes were highly promising. Models trained on second-derivative IR spectra in the 1800 to 1200-cm-1 range exhibited perfect classification for the manufacturing continent and country, with an impressive F1 score of 0.980 for product classification. Notably, the developed 1D CNN model outperformed traditional machine learning classifiers, such as support vector machines and feed-forward neural networks. In addition, the application of data point attribution enhanced the transparency of the decision-making process of the model, offering insights into the spectral patterns that affect classification. This study makes a considerable contribution to printing paper classification, with potential implications for accurate origin identification in various fields.

Application of FT-IR spectroscopy and chemometric technique for the identification of three different parts of Camellia nitidissima and discrimination of its authenticated product.

Camellia nitidissima C.W. Chi is a golden camellia recognized in Chinese herbology and widely used as tea and essential oil in Chinese communities. Due to its diverse pharmacological properties, it can be used to treat various diseases. However, unethical sellers adulterated the flower with other parts of Camellia nitidissima in their product. This study used an integrated tri-step infrared spectroscopy method and a chemometric approach to distinguish C. nitidissima’s flowers, leaves, and seeds. The three different parts of C. nitidissima were well distinguished using Fourier transform infrared spectroscopy (FT-IR), second-derivative infrared (SD-IR) spectra, and two-dimensional correlation infrared (2D-IR) spectra. The FT-IR and SD-IR spectra of the samples were subjected to principal component analysis (PCA), PCA-class, and orthogonal partial least square discriminant analysis (OPLS-DA) for classification and discrimination studies. The three parts of C. nitidissima were well separated and discriminated by PCA and OPLS-DA. The PCA-class model’s sensitivity, accuracy, and specificity were all >94%, indicating that PCA-class is the good model. In addition, the RMSEE, RMSEP, and RMSECV values for the OPLS-DA model were low, and the model’s sensitivity, accuracy, and specificity were all 100%, showing that it is the excellent one. In addition, PCA-class and OPLS-DA obtained scores of 27/32 and 26/32, respectively, for detecting adulterated and other TCM reference flower samples from C. nitidissima. Combining an infrared spectroscopic method with a chemometric approach proved that it is possible to differentiate distinct sections of C. nitidissima and discriminate adulterated samples of C.nitidissima flower.

Rapid Identification for the Pterocarpus Bracelet by Three-Step Infrared Spectrum Method

In order to explore a rapid identification method for the anti-counterfeit of commercial high value collections, a three-step infrared spectrum method was used for the pterocarpus collection identification to confirm whether a commercial pterocarpus bracelet (PB) was made from the precious species of Pterocarpus santalinus (P. santalinus). In the first step, undertaken by Fourier transform infrared spectroscopy (FTIR) spectrum, the absorption peaks intensity of PB was slightly higher than that of P. santalinus only at 1594 cm−1, 1205 cm−1, 1155 cm−1 and 836 cm−1. In the next step of second derivative IR spectra (SDIR), the FTIR features of the tested samples were further amplified, and the peaks at 1600 cm−1, 1171 cm−1 and 1152 cm−1 become clearly defined in PB. Finally, by means of two-dimensional correlation infrared (2DIR) spectrum, it revealed that the response of holocellulose to thermal perturbation was stronger in P. santalinus than that in PB mainly at 977 cm−1, 1008 cm−1, 1100 cm−1, 1057 cm−1, 1190 cm−1 and 1214 cm−1, while the aromatic functional groups of PB were much more sensitive to the thermal perturbation than those of P. santalinus mainly at 1456 cm−1, 1467 cm−1, 1518 cm−1, 1558 cm−1, 1576 cm−1 and 1605 cm−1. In addition, fluorescence microscopy was used to verify the effectiveness of the above method for wood identification and the results showed good consistency. This study demonstrated that the three-step IR method could provide a rapid and effective way for the anti-counterfeit of pterocarpus collections.

Fourier-Transform Infrared Spectroscopy for Discrimination of Cynomorium songaricum Inflorescence Samples from Different Origins

Cynomorium songaricum Rupr. has been used as a medicinal tonic in China for thousands of years. The Fourier-transform infrared (FT-IR) spectroscopy and second-derivative infrared (SD-IR) spectroscopy were used to study 200 samples of C. songaricum inflorescence collected at 20 sites in four different regions. A resemblance was found among the FT-IR spectra of samples from different origins and developed an IR fingerprint spectrum. The main absorption peaks in the range 1800-1200 cm-1 suggests that C. songaricum inflorescences may be rich in phenolic compounds, proteins and flavonoids. The SD-IR spectra of samples from different origins revealed an obvious intensity differences for peaks in the range 1800-1200 cm-1, especially for samples from Gansu province of China. An origin discrimination model based on principal component analysis is established. The prediction accuracy of the model is 87.25%. The results indicated that our origin discrimination model can differentiate production areas for C. songaricum.

Comparison of FTIR spectrum with chemometric and machine learning classifying analysis for differentiating guan-mutong a nephrotoxic and carcinogenic traditional chinese medicine with chuan-mutong

Chuan-Mutong (Clemetis spp.) is a precious medicinal herb in traditional Chinese medicine that possesses various therapeutic effects especially well known for its diuretic effect and widely used in Malaysia. However, there were several reported Chinese herb nephropathy cases due to the adulteration of Aristolochia spp. found in combinational herbal regimen. Guan-Mutong (Aristolochia manshuriensis), which looks similar in appearance and has similar therapeutic effects as Chuan-Mutong, has the possibility to substitute the Chuan-Mutong. Therefore, there is a necessity to differentiate the types of Mutong using analytical authentication methods. In this paper, a rapid and accurate method is proposed to discriminate Chuan-Mutong from Guan-Mutong by using tri-step fourier transform infrared spectroscopy (FT-IR) identification approaches. The method involves the deployment of FT-IR, second derivative infrared spectra (SD-IR), and two-dimensional correlation infrared spectra (2D-IR). In our approach, FT-IR spectra of Chuan-Mutong and Guan-Mutong were subjected to discrimination using principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), and machine learning classifiers (ML). Chuan-Mutong and Guan-Mutong can be clearly classified or discriminated against each other by ML, PLS-DA and PCA. The sensitivity, accuracy and specificity of ML were >90%, while the sensitivity, accuracy and specificity of PLS-DA were 100%. It is hence demonstrated that the infrared spectroscopic identification approach using PCA, PLS-DA and ML can be effectively used to differentiate Chuan-Mutong and Guan-Mutong. PLS-DA and ML provide a simple, fast, and high accuracy prediction to differentiate Chuan-Mutong and Guan-Mutong.

Fast Screening and Primary Diagnosis of COVID-19 by ATR FT-IR

Background: The outbreak of coronavirus disease 2019 (COVID-19) has led to substantial infections and mortality around the world. Fast screening and diagnosis are thus crucial to quick isolation and clinical intervention. Methods: Patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza A/B, and respiratory syncytial virus (RSV), as well as healthy controls, were included in this study. All viral infections were confirmed by reverse transcriptase PCR (RT-PCR). The serum samples were measured by attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR). Multivariate and statistical analysis was performed to differentiate between or among groups. Findings: We found that the most discriminatory bands for COVID-19 vs. control classification were amide I, amide II, and νs(PO2−) in original spectra and centered at 1632, 1545, 1400, 1079, and 1037 cm-1 in the second derivative infrared (SD-IR) spectra. Normal controls, non-severe, and severe COVID-19 patients were well separated by unsupervised methods. ATR FT-IR coupled with partial least square discriminant analysis (PLS-DA) was effective to differentiate COVID-19 from normal controls and other respiratory viral infections with the area under the receiver operating characteristic curve (AUROC) of 0·9866 (95%CI 0·9721-0·9939). Interpretation: The band centered at 1633 cm-1 in the SD-IR spectra is mainly attributed to the β-pleated sheet structure from immunoglobulins. Increases in antibody levels and dysregulation of phospholipids can be derived from the measured spectra. The serum FT-IR spectra exhibited “chemical fingerprints” towards different viral infections.Funding Statement: This work was funded by the National Natural Science Foundation of China (52041701).Declaration of Interests: The authors declare no competing interests.Ethics Approval Statement: This study was approved by the Ethics Committees from TsinghuaUniversity and Peking Union Medical College Hospital.

Application of mid-infared spectroscopy with multivariate analysis for the discrimination of toxic plant, Gelsemium elegans

Gelsemium elegans is a commonly used herb to treat different kinds of diseases. However, the indole alkaloid present in the plant might cause serious side effects. In this research, the infrared spectroscopic identification approach including Fourier transform infrared spectroscopy (FT-IR), Second derivative infrared spectra (SD-IR) and two-dimensional correlation infrared spectra (2D-IR) was used to develop a simple and rapid method to discriminate the stem, leaf and root of the Gelsemium elegans plant. This is because the stem, leaf and root contained different amount of indole alkaloid that contributed to the toxicity. Through this study, all the three parts were successfully identified and discriminated through the infrared spectroscopic identification method. The identification approach was also validated by comparing the samples of the mixture of both stem and root (SR) to the stem and root, respectively and also by comparing different plants with Gelsemium elegans plant. Besides that, all the samples of different parts of the Gelsemium elegans were analyzed with the Principal Component Analysis (PCA) and Soft Independent Modelling of Class Analogy (SIMCA) pattern recognition technique to test and verify the experimental results. The SIMCA model was validated by comparing 70 standard herbs to the model. From the results, macroscopic IR fingerprint method and the classification analysis successfully discriminate not only between Gelsemium elegans samples and standard herbs but also successfully distinguished the three different parts of Gelsemium elegans plant.

Rapid authentication and identification of different types of A. roxburghii by Tri-step FT-IR spectroscopy

Anoectochilus roxburghii (Wall.) Lindl. (Orchidaceae) is a precious traditional Chinese medicinal herb and has been perennially used to treat various illness. However, there were unethical sellers who adulterated wild A. roxburghii with tissue cultured and cultivated ones. Therefore, there is an urgent need for an effective authentication method to differentiate between these different types of A. roxburghii. In this research, the infrared spectroscopic tri-step identification approach including Fourier transform infrared spectroscopy (FT-IR), Second derivative infrared spectra (SD-IR) and two-dimensional correlation infrared spectra (2D-IR) was used to develop a simple and rapid method to discriminate between wild, cultivated and tissue cultivated A. roxburghii plant. Through this study, all three types of A. roxburghii plant were successfully identified and discriminated through the infrared spectroscopic tri-step identification method. Besides that, all the samples of wild, cultivated and tissue cultivated A. roxburghii plant were analysed with the Soft Independent Modelling of Class Analogy (SIMCA) pattern recognition technique to test and verify the experimental results. The results showed that the three types of A. roxburghii can be discriminated clearly as the recognition rate was 100% for all three types and the rejection rate was more than 60%. 70% of the validated samples were also identified correctly by the SIMCA model. The SIMCA model was also validated by comparing 70 standard herbs to the model. As a result, it was demonstrated that the macroscopic IR fingerprint method and the classification analysis could discriminate not only between the A. roxburghi samples and the standard herbs, it could also distinguish between the three different types of A. roxburghi plant in a direct, rapid and holistic manner.

Vasorelaxation Study and Tri-Step Infrared Spectroscopy Analysis of Malaysian Local Herbs.

Objectives:The aim of this paper is to investigate the activities of Malaysian local herbs (Clinacanthus nutans Lindau, Strobilanthes crispus, Murdannia bracteata, Elephantopus scaber Linn., Pereskia bleo, Pereskia grandifolia Haw., Vernonia amygdalina, and Swietenia macrophylla King) for anti-hypertensive and vasorelaxant activity. An infrared (IR) macro-fingerprinting technique consisting of conventional fourier transform IR (FTIR), second-derivative IR (SD-IR), and two-dimensional correlation IR (2D-correlation IR) analyses were used to determine the main constituents and the fingerprints of the Malaysian local herbs.Methods:The herbs were collected, ground into powder form, and then macerated by using three different solvents: distilled water, 50% ethanol, and 95% ethanol, respectively. The potentials of the extracts produced from these herbs for use as vasorelaxants were determined. Additionally, the fingerprints of these herbs were analyzed by using FTIR spectra, SD-IR spectra, and 2D-correlation IR spectra in order to identify their main constituents and to provide useful information for future pharmacodynamics studies.Results:Swietenia macrophylla King has the highest potential in terms of vasorelaxant activity, followed by Vernonia amygdalina, Pereskia bleo, Strobilanthes crispus, Elephantopus scaber Linn., Pereskia grandifolia Haw., Clinacanthus nutans Lindau, and Murdannia bracteata. The tri-step IR macro-fingerprint of the herbs revealed that most of them contained proteins. Pereskia bleo and Pereskia grandifolia Haw. were found to contain calcium oxalate while Swietenia macrophylla King was found to contain large amounts of flavonoids.Conclusion:The flavonoid content of the herbs affects their vasorelaxant activity, and the tri-step IR macro- fingerprint method can be used as an analytical tool to determine the activity of a herbal medicine in terms of its vasorelaxant effect.

Identification of the traditional Tibetan medicine “Shaji” and their different extracts through tri-step infrared spectroscopy

Hippophae rhamnoides subsp. sinensis Rousi, Hippophae gyantsensis (Rousi) Y. S. Lian, Hippophae neurocarpa S. W. Liu & T. N. He and Hippophae tibetana Schlechtendal are typically used under one name “Shaji”, to treat cardiovascular diseases and lung disorders in Tibetan medicine (TM). A complete set of infrared (IR) macro-fingerprints of these four Hippophae species should be characterized and compared simply, accurately, and in detail for identification. In the present study, tri-step IR spectroscopy, which included Fourier transform IR (FT-IR) spectroscopy, second derivative IR (SD-IR) spectroscopy and two-dimensional correlation IR (2D-IR) spectroscopy, was employed to discriminate the four Hippophae species and their corresponding extracts using different solvents. The relevant spectra exhibited the holistic chemical compositions and variations. Flavonoids, fatty acids and sugars were found to be the main chemical components. Characteristic peak positions, intensities and shapes derived from FT-IR, SD-IR and 2D-IR spectra provided valuable information for sample discrimination. Principal component analysis (PCA) of spectral differences was performed to illustrate the objective identification. Results showed that the species and their extracts can be clearly distinguished. Thus, a quick, precise and effective tri-step IR spectroscopy combined with PCA can be applied to identify and discriminate medicinal materials and their extracts in TM research.

Rapid Discrimination of Different Grades of White Croaker Surimi by Tri-Step Infrared Spectroscopy Combined with Soft Independent Modeling of Class Analogy (SIMCA)

White croaker surimi, an important raw material of traditional kamaboko industry, commonly has four grades, A, AA, FA, and SA which have distinct quality but are tough to be identified and discriminated rapidly and holistically by conventional methods. A Tri-step infrared spectroscopy, Fourier transform infrared spectroscopy (FT-IR) integrated with second derivative infrared (SD-IR) spectroscopy, and two-dimensional correlation infrared spectroscopy (2DCOS-IR), combined with statistical pattern recognition, was employed to rapidly characterize and discriminate four grades of white croaker surimi (A, AA, FA, and SA). The four surimis had similar IR, and SD-IR macro-fingerprints (similarity >0.9) especially for the absorption bands of amide groups due to proteins were the main compositions. However, relative contents of lipids in all surimis could be directly observed. Compared to the other three surimis, SA had a middle strong characteristic peak of lipids at 1745 cm−1, indicating that SA had the highest content of lipids. The sequence of lipid contents in the four surimis was SA > FA > AA > A, which was further verified by SD-IR spectra. Moreover, evident differences were disclosed visually in 2DCOS-IR spectra of 1680–1610 cm−1, indicating that the four surimis have fine differences in protein secondary structures. Furthermore, 76 parallel samples (18 A, 19 AA, 19 FA, and 20 SA) were objectively classified by soft independent modeling of class analogy (SIMCA) based on principal component regression (PCR). It has been demonstrated that the Tri-step infrared spectroscopy combined with cluster analysis could be a scientific and powerful tool for rapid discrimination and identification of different grades of surimi in a holistic manner.

Rapid discrimination of three marine fish surimi by Tri-step infrared spectroscopy combined with Principle Component Regression

A Tri-step infrared spectroscopy (Fourier transform infrared spectroscopy (FT-IR) integrated with second derivative infrared (SD-IR) spectroscopy and two-dimensional correlation infrared spectroscopy (2DCOS-IR)) combined with Principal Component Regression (PCR) were employed to characterize and discriminate three marine fish surimi (white croaker surimi (WCS), hairtail surimi (HS) and red coat surimi (RCS)). The three surimi had similar IR macro-fingerprints (similarity>0.7) especially for the absorption bands of amide groups. Compared to the other two surimi, however, RCS had a middle strong characteristic peak of lipids at 1745cm−1, indicating that RCS had the highest content of lipids. SD-IR spectra of the three surimi enhanced the spectral resolution and amplified the small differences, especially at about 1682cm−1, 1679cm−1, 1656cm−1 and 1631cm−1, suggesting that the three had different profiles of proteins. Moreover, evident differences were observed in 2DCOS-IR spectra of 1500–1800cm−1. WCS had one strong (1620cm−1) and three weak auto-peaks (1520cm−1, 1552cm−1, 1706cm−1). HS had three strong (1621cm−1, 1648cm−1, 1708cm−1) and two weak auto-peaks (1523cm−1, 1553cm−1), whereas RCS had one strong (1623cm−1) and three weak auto-peaks (1525cm−1, 1709cm−1, 1738cm−1). Furthermore, sixty batches of surimi (twenty for each surimi) were objectively classified by PCR. It was demonstrated that the Tri-step infrared spectroscopy combined with PCR could be applicable for discrimination of precious marine fish surimi in a direct, rapid and holistic manner.

Identification of some Piper crude drugs based on Fourier transform infrared spectrometry

The common peak ratio and variant peak ratio were calculated by FTIR spectroscopy of seven medicinal plants of Piper. The dual index sequence of common peak ratio and variant peak ratio was established, which showed the sibship of the medicinal plants. The common peak ratio of Piper kadsura (Choisy) Ohwi, Piper wallichii (Miq.) Hand.-Mazz. Piper laetispicum (C. DC.) was greater than 77%, and the variant peak ratio was less than 30%. The results showed the near sibship between the three drugs. The common peak ratio of Piper kadsura (Choisy) Ohwi, Piper nigrum L. and Piper boehmeriae folium Wall (Miq.) C. DC. Var. tonkinense (C. DC.) was about 61% which showed the farther sibship. The common peak ratio of Piper kadsura (Choisy) Ohwi and Piper betle (Linn.) was only 44%, which showed the farthest sibship. Piper kadsura (choisy) Ohwi and its adulterants, such as Piper wallichii (Miq.) Hand. -Mazz., Piper boehmeriaefolium Wall (Miq.) C. DC. Var. tonkinense C. DC. , Piper laetispicum C. DC., Piper nigrum L., could be identified by comparing their second order derivative IR spectrum of the samples. FTIR technique is a non-destructive analysis method which provides information of functional group, type and hydrogen bond without complex pretreatment procedures such as extraction and separatioin. FTIR method has some characteristics such as rapid and simple analysis procedure, good reproducibility, non-destructive testing, few amount of required sample and low cost and is environment-friendly. The method solved the problems of limit in resource of Piper kadsura (Choisy) Ohwi, many fakes and difficulties in identification, and brought the security for the clinical medication. FTIR provides a new method for identification of Piper kadsura (choisy) Ohwi and its fakes and meets the requirement for comprehensive analy sis and global analysis of traditional Chinese medicine.

Rapid identification of Pterocarpus santalinus and Dalbergia louvelii by FTIR and 2D correlation IR spectroscopy

Since Pterocarpus santalinus and Dalbergia louvelii, which are of precious Rosewood, are very similar in their appearance and anatomy characteristics, cheaper Hongmu D. louvelii is often illegally used to impersonate valuable P. santalinus, especially in Chinese furniture manufacture. In order to develop a rapid and effective method for easy confused wood furniture differentiation, we applied tri-step identification method, i.e., conventional infrared spectroscopy (FT-IR), second derivative infrared (SD-IR) spectroscopy and two-dimensional correlation infrared (2DCOS-IR) spectroscopy to investigate P. santalinus and D. louvelii furniture. According to FT-IR and SD-IR spectra, it has been found two unconditional stable difference at 848cm−1 and 700cm−1 and relative stable differences at 1735cm−1, 1623cm−1, 1614cm−1, 1602cm−1, 1509cm−1, 1456cm−1, 1200cm−1, 1158cm−1, 1055cm−1, 1034cm−1 and 895cm−1 between D. louvelii and P. santalinus IR spectra. The stable discrepancy indicates that the category of extractives is different between the two species. Besides, the relative stable differences imply that the content of holocellulose in P. santalinus is more than that of D. louvelii, whereas the quantity of extractives in D. louvelii is higher. Furthermore, evident differences have been observed in their 2DCOS-IR spectra of 1550–1415cm−1 and 1325–1030cm−1. P. santalinus has two strong auto-peaks at 1459cm−1 and 1467cm−1, three mid-strong auto-peaks at 1518cm−1, 1089cm−1 and 1100cm−1 and five weak auto-peaks at 1432cm−1, 1437cm−1, 1046cm−1, 1056cm−1 and 1307cm−1 while D. louvelii has four strong auto-peaks at 1465cm−1, 1523cm−1, 1084cm−1 and 1100cm−1, four mid-strong auto-peaks at 1430cm−1, 1499cm−1, 1505cm−1 and 1056cm−1 and two auto-peaks at 1540cm−1 and 1284cm−1. This study has proved that FT-IR integrated with 2DCOS-IR could be applicable for precious wood furniture authentication in a direct, rapid and holistic manner.

Differentiation of Rhizoma Curcumas Longae and Radix Curcumae by a Multistep Infrared Macro-Fingerprint Method

A multistep infrared macro-fingerprint method was applied to identify two Chinese herbal drugs, Rhizoma Curcumas Longae (RCL) and Radix Curcumae (RC). Fourier transform infrared (FT-IR) spectra of the two were similar to each other and consistent with the 11 peaks of the spectrum of starch. RCL had a characteristic absorption peak at approximately 1514 cm−1 that correlated to the strong peak near 1509 cm−1 of curcumin. Between 900 cm−1–1700 cm−1 of the second derivative infrared (SD-IR) spectra, with higher resolution, RCL, and curcumin had 10 common peaks. In the FT-IR and SD-IR spectra of the ethanol extract, the spectra of the RCL extract and curcumin were similar, but RC was different. According to the fingerprint characteristics of the infrared spectra for RC and its extracts, the strongest peak at 1055 cm−1; the C-O absorption peaks at 1124 cm−1, 1106 cm−1, and 996 cm−1; and the strong methylene peaks at 2925 cm−1 and 2853 cm−1 suggest that RC contains more saccharides. In the range of 1350 cm−1–1700 cm−1, RCL and RC had similar two-dimensional infrared (2D-IR) correlation spectra. Both of them had three autopeaks, but the autopeaks were located at 1458 cm−1, 1560 cm−1, and 1641 cm−1 for RCL and 1458 cm−1, 1560 cm−1, and 1669 cm−1 for RC, suggested that the aromatic components of the two were not identical. The average correlation for the 18 RCL and 18 RC samples were 0.9906 and 0.9878, respectively, and this method achieves a good classification of the sample type.

Study on Light Aging of Silk Fabric by Fourier Transform Infrared Spectroscopy and Principal Component Analysis

To investigate environmental effect on cultural materials, Fourier transform infrared technique (FTIR/ATR) was applied to analyze the silk aging process. Changes in chemical and conformational structures of silk fabric undergoing ultraviolet induced degradation were investigated. The IR spectra provided strong bands of photosensitive amide I, II, and III. For overlapping amide III region, both of the original and second-derivative IR spectra revealed that UV irradiation induced the structural transformation from β-sheet domain to β-turn conformation, which was supported by the increase of β-turn marker band at 1015 cm−1 associated with polyglycine. Additionally the reduced bands associated with (GlyAla)n segment at 1000 and 976 cm−1, and the decreased band at 1070 cm−1 related to β-sheet structure also illustrated the conformational transition. Furthermore, we applied a chemometric method of principal component analysis for the evaluation of silk degradation based on variations in amide I spectral region. The score plot using the first two principal components effectively summarized the general trend of silk-aging and revealed the quick degradation appeared in the initial stages (12 h and 24 h) and the 108-hr stage. This work provides a potential novel application of the infrared spectroscopy in noninvasive qualitative and quantitative investigation of silk degradation.

Structure of 4-(trimethylammonium)benzoate hydrate studied by X-ray diffraction, DFT calculations, NMR and FTIR spectra

► X-ray, DFT, FTIR, NMR of 4-(trimethylammonium)benzoate hydrate. ► Water molecule interacts with two 4-(trimethylammonium)benzoate molecules. ► The molecular structure is stabilized by hydrogen bonds and electrostatic interactions. The structure of 4-(trimethylammonium)benzoate hydrate ( 1 ) has been studied by X-ray diffraction, B3LYP/6-311++G(d,p) calculations, FTIR and NMR spectroscopic techniques. The crystals are monoclinic, space group P 2 1 /c. Water molecule interacts with two 4-(trimethylammonium)benzoate molecules via two O(1w)–H⋯O hydrogen bonds of the lengths 2.781(2) and 2.774(2) Å. The FTIR spectrum of the solid compound is consistent with the X-ray results. The second-derivative IR spectrum of 1 and calculated frequencies for the optimized structure 2 are used to explain frequencies in the experimental FTIR spectrum. The interpretation of 1 H and 13 C NMR spectra have been based on 2D experiments and calculated GIAO/B3LYP/6-311++G(d,p) magnetic isotropic shielding constants. Interesting are dimer structures ( 6 and 7 ) estimated by B3LYP/6-311++G(d,p) calculations, which are stabilized by N + ⋯O–C electrostatic interactions.

Additives affecting thermal stability of salmon calcitonin in aqueous solution and structural similarity in lyophilized solid form

The effects of additives on conformational stability and structural similarity of salmon calcitonin (sCT) in aqueous solution and lyophilized solid form were investigated by using transmission Fourier transform infrared (FT-IR) microspectroscopy with second-derivative spectral analysis. To compare the structural similarity between native sCT and lyophilized sCT samples with or without additive, the spectral correlation coefficient analysis between two second-derivative IR spectra was applied. Two types of additives were also selected: sugars/polols [trehalose, sucrose, mannitol and 2-hydroxypropyl-β-cyclodextrin (HP-βCD)] and polymers [dextran, heparin and human serum albumin (HSA)]. When trehalose, mannitol or dextran was respectively co-incubated with sCT in 40°C aqueous solution, these additives slightly changed the secondary conformation of sCT. However, sucrose or HP-βCD accelerated the intramolecular β-sheet formation of sCT due to the appearance of IR peak at 1631cm−1. A precipitation was occurred in the sCT aqueous solution after co-incubation with heparin or HSA, in which the ionic interaction and/or hydrophobic adsorption might be responsible for this result. A strong peak at 1630cm−1 (intramolecular β-sheet) with a minor peak at 1618cm−1 (intermolecular β-sheet) was also evidenced in the second-derivative IR spectrum of the sCT precipitate. The secondary conformation of native sCT after lyophilization was markedly altered from the predominant α-helix to random coil/β-sheet structures, but trehalose, mannitol or sucrose had the greatest stabilization effect on the lyophilized sCT due to a higher structural similarity. The secondary structure of sCT was perturbed during co-lyophilization with HP-βCD, dextran, heparin or HSA. The result of this study indicates that both mannitol and trehalose would serve as optimal stabilizers for sCT in both aqueous solution and lyophilized formulation.

FT-IR microscopic imaging of calcified deposit of rotator cuff tendonitis: A pilot study and a randomised identification of the compositional components after extrusion from tendon to muscle

Fourier transform infrared (FT-IR) microspectroscopy with mapping system was applied to identify and evaluate what difference in the distribution and compositional components of the calcified deposit of rotator cuff tendonitis after dislocation from tendon to muscle. A 49 year-old female patient suffered from severe shoulder pain was enrolled in this study. Diagnostic high-resolution ultrasonography (HRUS) was initially carried out to verify the calcific tendonitis. The calcified deposits were then examined by histopathologic assessment and FT-IR microspectroscopy. Diagnostic HRUS reveals that the calcified deposits were observed in the subscapularis tendon and infraspinatus muscle of the shoulder for this patient. FT-IR microspectroscopic imaging results clearly indicate that both IR spectra of the calcified deposits in tendon and muscle were almost the same as that of the IR spectrum of hydroxyapatite except the peak at 873 cm −1. It is also found that the peak intensity at 1030 cm −1 for tendon sample was somewhat more intense than that of the peak at 1031 cm −1 for muscle sample, implying that the calcified sample in the tendon seems to be mature than that in the muscle. The second-derivative IR spectra of two calcified samples exhibit two specific sharp peaks at 880 and 872 cm −1, indicating that the type A and type B carbonated apatites were markedly co-existed in both calcified deposits of tendon and muscle even the calcified deposit was dislocated from tendon to muscle. These carbonated apatites presented in the calcified deposits of either tendon or muscle of the shoulder were also consistent with the nodular or nodular nodular–cystic morphology of calcified plaque of the shoulder after HRUS examination.

Molecular structure of the 1:2 complex of 2-quinuclidinium-butyrate with p-hydroxybenzoic acid

The structure of the 1:2 complex of 2-quinuclidinium-butyrate, QNBu, with p-hydroxybenzoic acid, HBA, ( 1) has been determined by X-ray diffraction, DFT calculations, and the complex was characterized by FTIR and NMR spectroscopy. The crystals are triclinic, space group P 1 ¯ . The QNBu and HBA molecules are linked by medium-strong O H···O hydrogen bonds into a double strand related by two types of inversion centers, each inside different H-bonded rings. The O···O distances vary between 2.652(3) and 2.720(2) Å. The FTIR spectrum of the solid complex is consistent with the X-ray results. The second-derivative IR spectrum and calculated frequencies for the optimized structure of QNBu·2HBA were used to explain the FTIR spectrum in the carbonyl-carboxylate region. The interpretation of 1H and 13C NMR spectra has been based on 2D experiments and calculated GIAO/B3LYP/6-31G( d, p) magnetic isotropic shielding constants.