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Dynamic protein structures are crucial for deciphering their diverse biological functions. Two-dimensional infrared (2DIR) spectroscopy stands as an ideal tool for tracing rapid conformational evolutions in proteins. However, linking spectral characteristics to dynamic structures poses a formidable challenge. Here, we present a pretrained machine learning model based on 2DIR spectra analysis. This model has learned signal features from approximately 204,300 spectra to establish a spectrum-structure correlation, thereby tracing the dynamic conformations of proteins. It excels in accurately predicting the dynamic content changes of various secondary structures and demonstrates universal transferability on real folding trajectories spanning timescales from microseconds to milliseconds. Beyond exceptional predictive performance, the model offers attention-based spectral explanations of dynamic conformational changes. Our 2DIR-based pretrained model is anticipated to provide unique insights into the dynamic structural information of proteins in their native environments.

Objectives: White spot lesions are more susceptible to staining agents due to their porous structure. This study examines the impact of white spot lesion treatments on discoloration caused by pediatric supplements. Method and materials: Three treatments (fluoride, casein phosphopeptide-amorphous calcium phosphate [CPP-ACP], resin infiltration), a control, and their respective syrup-based subgroups (iron and black elderberry syrups) were established, each with eight teeth. Artificial white spot lesions were induced, and weekly applications of fluoride varnish, daily applications of CPP-ACP paste, or a single resin infiltration procedure were performed on the white spot lesions within the treatment groups over 4 weeks. Simultaneously, samples were exposed daily to iron or black elderberry syrups. Spectrophotometer measurements were taken at baseline, after demineralization (T0), and after 1 (T1), 2 (T2), and 4 weeks (T4). ΔE00 values were calculated. Statistical analysis was conducted using a three-way mixed-design ANOVA, with the significance level set at P = .05. Results: At T4, ΔE00 values from all groups exceeded the clinical acceptability limit of 1.8. At T2 and T4, the ΔE00 values obtained from the black elderberry syrup subgroups were significantly higher (P < .001). At T4, the highest ΔE00 values were seen in the CPP-ACP groups (P < .001). The lowest ΔE00 values at T2 and T4 were observed in the resin infiltration groups (P < .05). Conclusions: Supplements containing ferrous sulfate and black elderberry extract caused color changes in white spot lesions that exceeded the clinical acceptability limit. Resin infiltration of white spot lesions provides advantages over remineralization treatments, particularly in minimizing discoloration induced by pediatric supplements. [ABSTRACT FROM AUTHOR]

Milk is a major dietary source of calcium; thus, accurate and precise quantification of calcium in milk and other dairy products is necessary for quality control. Conventional instrumental methods are sensitive and accurate but require expensive instrumentation, sample pretreatment, skilled personnel, and a long detection time. Herein, a microfluidic paper-based analytical device (µPAD) was developed to quantify calcium ions (Ca2+) in milk using a smartphone as a detector. The method utilized a complexometric reaction between Ca2+ and ethylene diamine tetraacetic acid with murexide as an indicator. The response was the average color intensity at the detection zones measured using the Color Picker application. The proposed µPAD exhibited a good linear detection range (1 to 10 mM), a low detection limit of 0.42 mM, and a short analysis time of 2 min. The determination of Ca2+ in milk samples using the proposed µPAD was consistent with a potentiometric method. The proposed µPAD demonstrates many advantages, including rapid detection, acceptable accuracy, low cost, low sample volume, and suitability for on-site quantification of Ca2+ in real samples. [ABSTRACT FROM AUTHOR]

This work reports the effect of adding Sm2O3 and silver nanoparticles, in small quantities up to 1 mol%, on the optical and structural properties of the B2O3-Li2O glass-ceramic system. The X-ray diffraction patterns of the samples show the presence of small quantities of the B2O3 crystalline phase, in addition to a major amorphous phase. Various structural units like BO3, BO4, and LiO4, present in the samples network, are responsible for the absorption bands from the FT-IR spectra. The optical spectra provided valuable information such as the identification of the observed electronic transitions, the energy gap, the refractive index, and metallization values. The luminescence data show the fact that with the addition of metallic NPs the quenching phenomenon can be observed after 0.5 mol% samarium ions. The studied systems are interesting for optical and semiconducting devices. [ABSTRACT FROM AUTHOR]

Background: The need to determine physical compatibility of intravenous admixtures is directly related to patient safety and patient outcomes. While the provision of multi-modal analgesic strategies has increased over the past decade, a paucity of data exists regarding physical compatibility of select medications. Objectives: To evaluate the physical compatibility of methocarbamol in Lactated Ringer's (LR), 0.45% normal saline (0.45% NaCl), and Plasma-Lyte A (PLA) at concentrations of 4, 10, and 20 mg/mL. Methods: Admixtures were prepared and evaluated using previously validated methods under a laminar flow hood using aseptic technique. Samples were prepared in a triplicate manner, 3 mL aliquots were placed into polymethyl methacrylate cuvettes for evaluation at time points 0, 1, 5, 8, and 24 hours. Visual inspection of samples included assignment of a number: 0—no precipitation, 1—trace evidence of precipitation, 2—slight haze, 3—medium haze, and 4—heavy precipitation. Any evidence of precipitation was considered significant. A variable wavelength spectrophotometer set at 547 nanometers was used to measure absorbance. A change in absorbance of ±0.010 was considered significant. A change in pH of ±0.1 was considered significant. Results: No significant changes occurred relating to visual inspection or absorbance across all concentrations and time points for LR; however, there was a significant change in pH across all concentrations at hour 5. In 0.45% NaCl and PLA, no remarkable changes occurred across all concentrations and time points regarding visual observation, spectrophotometric absorbance, and pH analysis. Conclusions: Methocarbamol at concentrations of 4, 10, and 20 mg/mL is physically compatible for up to 1 hour in LR. Methocarbamol is physically compatible in 0.45% NaCl and PLA for up to 24 hours. Chemical stability tests are warranted to confirm these findings. [ABSTRACT FROM AUTHOR]

Background: A decrease in oral pH levels may have detrimental effects on vacuum-formed retainers since an acidic oral environment could impact the mechanical and physical properties of these retainers. The present In vitro study aimed to evaluate the effect of simulated gastric acid at pH 4 and 1.2 on the surface microhardness, flexural strength, and color change of three different types of orthodontic retainer materials. Methods: A total of 144 vacuum-formed commercially available retainer materials: copolyesters, polypropylene, and PET-G (n = 48/group) were evaluated. Each specimen was immersed in distilled water, and then the specimens were divided into two subgroups: those with a pH of 4 and those with a pH of 1.2. The microhardness test was performed using Innovatest, the flexural strength was evaluated by a universal testing machine, and the color change was analyzed using a spectrophotometer. The data were analyzed using One-Way ANOVA and independent sample t test at a significance value of P ≤ 0.05. Results: Our findings indicated a significant decrease in flexural strength in all the experimental groups after immersion in pH 1.2 and 4 solutions (P < 0.001), with PET-G being the most affected material, followed by copolyester and polypropylene. Only copolyester demonstrated a significant decrease in surface microhardness following immersion in a pH 4 solution (P = 0.025). All materials exhibited the greatest degree of color alteration CP (P = 0.006), PP (P = 0.001), and PET-G (P = 0.009) respectively. Conclusion: The study concluded that copolyester adversely affects flexural strength, surface microhardness, and color when subjected to immersion in simulated gastric acid. Therefore, care is recommended for patients diagnosed with gastroesophageal reflux disease. [ABSTRACT FROM AUTHOR]

Microalgae are often used in different industrial sectors and can be used as indicators of aquatic environmental health. An essential step for cultivating microalgae is assessing the cell density, which is traditionally performed through cell counting by optical microscopy (OM). However, this method has limitations, mainly in terms of runtime and low reproducibility. Assessing the optical density (OD) by spectrophotometry was investigated as an affordable alternative. The OD of the green microalgae Desmodesmus subspicatus and Tetraselmis sp. was detected at 680 nm. The correlation between the cell density and OD was suitable for both microalgae and the accuracy was comparable to traditional OM counting. In toxicological tests, the OD technique allowed the monitoring of microalgal growth in the presence of the chemicals K2Cr2O7, KCl and sodium dodecyl sulfate. This study sheds some light on this well-known technique, which is an important contribution since few articles have explored its potentialities and fragilities. [ABSTRACT FROM AUTHOR]

For paediatric patients suffering from neurofibromatosis, Selumetinib (SEL) is the only approved drug. Here an original ecofriendly and high pace method is introduced using 96- microwell spectrophotometric assay (MW-SPA) to measure SEL content in bulk and commercial pharmaceutical formulation (Koselugo® capsules). This assay was relied on in-microwell formation of a coloured charge transfer complex (CTC) upon interaction of SEL with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The complex was fully characterized by spectrophotometric and computational studies. The CTC exhibited an absorbance maximum (λmax) at 440 nm. The ease of reaction occurrence, complex stability and its high absorptivity were proved by measuring its association constant (0.63 × 102 L/ mol), standard free energy change (-10.31 KJ/mol), molar absorptivity (ε) (3.78 × 103 L/mol/cm), and the SEL: DDQ stoichiometric ratio (1:1). Establishments of the optimum values of the applied conditions in 96-well assay plate were refined regarding DDQ concentration, reaction time, temperature, and solvents. Validation of the assay was according to the ICH guidelines. The assay was linear in SEL' concentrations ranged from 10 to 200 µg/well, with limits of detection and quantitation of 4.1 and 12.5 µg/well, respectively. Then, the assay was efficaciously adapted to accurately and precisely determine SEL content in bulk form and Koselugo® capsules. The assay environmental safety was documented by three different comprehensive metric tools. Additionally, assessment of the assay's rate demonstrated its high throughput, enabling the processing of large number of samples in pharmaceutical quality control laboratories. The successful development of this assay provides a valuable fast and green analytical tool for ensuring the quality control of SEL's bulk form and capsules. [ABSTRACT FROM AUTHOR]

Mn2+ is an essential cation extensively utilized in various industrial processes, including electrolytic manganese production, manganese dioxide manufacturing, and zinc processing. It also poses significant environmental challenges as a primary pollutant in Mn-containing wastewater and hazardous materials. Effective monitoring and control of Mn2+ in these processes are vital for improving resource conversion efficiency and minimizing pollutant production. However, the direct determination of high concentrations of Mn2+ remains challenging due to rapid reactions, which impede improvements in cleaner industrial production. Traditional detection method like potassium periodate spectrophotometry (PPS) method is limited to low concentrations and involve complex processes that contribute to secondary pollution. In this study, we evaluated the performance of four alternative methods—External Standard Calibration (EC), Area Under the Curve (AUC), Standard Addition (SA), and Multi-Energy Calibration (MEC)—for determining high-concentration Mn²⁺. The study found that the weak absorption characteristic of aqueous Mn²⁺ due to spin-forbidden transitions is advantageous for direct determination at high concentrations in its original valence state. By optimizing the optical path and wavelength, concentrations up to 50 g/L were detected, surpassing the PPS upper limit by 5000 times. Among the methods, EC demonstrated superior accuracy and precision, with a performance rate of 98.07% and a relative standard deviation of less than 1%. The EC method's minimal time consumption and cost-effectiveness make it suitable for automation and integration into industrial systems for continuous, real-time monitoring. This research offers valuable insights into high-concentration Mn2+ determination using spectrophotometry, highlighting the EC method's potential for real-time monitoring and its adaptability for large-scale industrial operations. The findings provide a substantial reference for the direct detection of other industrial components, promoting more efficient and environmentally friendly industrial practice. [ABSTRACT FROM AUTHOR]

Understanding the formation of multiple populations in globular clusters (GCs) represents a challenge for stellar population studies. Nevertheless, the outermost cluster regions, likely to hold clues about the initial configuration of GC stars, remain underexplored. We use synthetic spectra reflecting the chemical compositions of first- and second-population (1P, 2P) stars in 47 Tucanae to identify spectral regions sensitive to these populations. This led us to define new photometric bands that effectively distinguish 1P and 2P giant stars using Gaia XP spectra. Testing these filters, we constructed the pseudo two-colour diagrams dubbed chromosome maps (ChMs) and, for the first time, identified 1P and 2P stars in the cluster's outermost regions and beyond its tidal radius. We constructed similar diagrams for NGC 3201, NGC 6121, NGC 6752, and NGC 6397, thus exploring GCs with different metallicities. The ChMs effectively distinguished multiple populations in the outer regions of all clusters, except for the metal-poor NGC 6397. Our findings, together with literature results from more-internal regions, show that the 2P stars of 47 Tucanae are more-centrally concentrated than the 1P. A similar pattern is seen for 2P stars with extreme chemical composition of NGC 3201. The multiple populations of NGC 6121, and NGC 6752 share the same radial distributions. These radial behaviours are consistent with the GC formation scenarios where 2P stars originate in the central regions. Noticeably, results on NGC 3201 are in tension with the conclusion from recent work that its 1P is more centrally concentrated than the 2P and might form with more central concentration. [ABSTRACT FROM AUTHOR]

Remdesivir and moxifloxacin hydrochloride are among the most frequently co-administered drugs used for COVID-19 treatment. The current work aims to evaluate green spectrophotometric methodologies for estimating remdesivir and moxifloxacin hydrochloride in different matrices for the first time. The proposed approaches were absorbance subtraction, extended ratio subtraction and amplitude modulation methods. In order to determine the absorbance of the investigated medications in combination at the isoabsorptive point, the pure moxifloxacin hydrochloride absorbance factor is applied using the absorbance subtraction method, which modifies the zero absorption spectra of the drugs under investigation at the isoabsorptive point (229 nm). The spectrum of moxifloxacin hydrochloride is more extended in the plateau area between 340 and 400 nm, where remdesivir exhibits no absorption. So, also, the ratio spectra were successfully manipulated for quantification of the two drugs. Regarding the pharmacokinetic profile of remdesivir (Cmax 4420 ng/mL) and moxifloxacin hydrochloride (Cmax 3.56 µg/mL), the proposed methods were effectively used to spectrophotometrically determine remdesivir and moxifloxacin hydrochloride in plasma matrix. The new approach was validated using the ICH guidelines for specificity, linearity, precision, and accuracy. The greenness of the reported methodologies was evaluated using two metrics: the analytical eco-scale and the green analytical procedure index. [ABSTRACT FROM AUTHOR]

Novel, «green» and simple visible spectrophotometric procedures for the determination of six dihydropyridines CCBs (amlodipine besylate (AML), lacidipine (LAC), levamlodipine besylate (LAML), nifedipine (NIF), nimodipine (NIM) and nitrendipine (NIT)) through derivatization with the sulfophthalein dye bromophenol blue (BPB) have been developed. The optimal parameters for CCBs spectrophotometric analysis via complex formation using BPB were as follows: detection wavelength—596 nm, reaction time—5 min, ratio of reacting components—1:1, operating temperature—25 ± 2 °C. The concentration was linearly proportional to absorbance values in the range of 3.40—17.00 μg/mL (AML), 1.14—9.11 μg/mL (LAC), 1.14—9.08 μg/mL (LAML), 4.16—12.40 μg/mL (NIF), 0.84—5.86 μg/mL (NIM), 6.52—19.60 μg/mL (NIT). The developed methods are colorimetric and therefore does not require a UV instrument to quantify these drugs. The proposed approach was more efficient in terms of time reliability, sensitivity and «greenness» than other recorded spectrophotometric methods and can be easily implemented for routine pharmaceutical analysis. [ABSTRACT FROM AUTHOR]

Combining non-sedating antihistamines (NSAs) with montelukast (MON) has been found to significantly enhance the therapeutic efficacy against daytime and composite nasal symptoms, including rhinorrhea, sneezing, and itching. This article reviews the current analytical methods employed for the identification and quantitative determination of MON in combination with NSAs in various marketed formulations. The most commonly used methods for the determination of MON and NSAs in combination are chromatographic methods (high-performance liquid chromatography [HPLC] and thin-layer chromatography) and spectrometry methods (spectrofluorometry and spectrophotometry). Recent preferences in the analysis of MON and NSAs in combination samples prove the primacy of HPLC (61%) and confirm the general trends moving toward more sensitive methods, with a higher resolution potential, consumption of small quantities of samples and reagents, and requiring less analysis time. [ABSTRACT FROM AUTHOR]

Patients who undergo transcatheter aortic valve implantation (TAVI) may become pale during the early postoperative period. To clarify whether facial colors changed during the postoperative period, patients' skin color from before to 72 h after TAVI was measured spectrophotometrically. Factors associated with skin color were also investigated. Forehead skin color and vital signs were measured before TAVI and at 6, 18, and 72 h after TAVI in 11 patients scheduled for TAVI. Blood examinations were performed before and 18 and 72 h after TAVI. Skin color was assessed using a spectrophotometer and expressed as L* (lightness), a* (red/green), and b* (yellow/blue) according to the CIE1976L*a*b* color space. Skin lightness L* values increased at 6 and 18 h after TAVI and returned at 72 h after TAVI and a* values decreased at 6 h after TAVI. The b* values did not change perioperatively during TAVI. No associations were observed between the changes in skin color and changes in BP or laboratory data. The findings that the skin color became whitish and less reddish in the early postoperative period resembled that occurring during an acute inflammatory response. Observation of skin color is important to detect the possibility of postoperative complications. [ABSTRACT FROM AUTHOR]

Double beam UV-Vis spectrophotometry and high-performance liquid chromatography (HPLC) techniques have been used to determine the antibacterial fluorescent phloxine B dye in dental preparations. In the visible wavelength range of 400 to 800 nm, the spectrophotometric signal was obtained at λmax = 539 nm. The HPLC process used C-18 (5 μm) with a UV detector at 254 nm, 1.5 mL/min flow rate, 0.635 min retention time, and water, acetonitrile, and 2-propanol as the mobile phase. Several parameters have been used to analyze the performance of the HPLC and double-beam UV-Vis spectrophotometry apparatuses, including stability, detection and quantification limits, calibration curves, and repeatability. The study focused on the repeatability of spectrophotometric and HPLC procedures for 8 × 10–6 and 5 × 10–6 mol/L of phloxine B. The results showed that the standard deviation (STD) for ten spectrophotometric measurements and eight HPLC measurements, respectively, was ± 0.0004 and ± 2.487 with relative standard deviation (RSD%) of 0.048 and 1.05%. Throughout 90 min of the analysis period, the spectrophotometric and HPLC signals for 8 × 10–6 and 5 × 10–6 mol/L of phloxine B were shown to be exceptionally stable. The ranges of the calibration curves were 1 × 10-6–2 × 10–5 mol/L for the spectrophotometry and 1 × 10–5–1 × 10–4 mol/L for HPLC. Within the concentration ranges under consideration, they were assigned linear relations with correlation coefficients (r2) of 0.9995 for spectrophotometric and 0.99 for HPLC measurements. The detection limits for phloxine B were found to be 1.24 × 10–8 mol/L (0.0103 ppm) and 8.25 × 10–7 mol/L (0.068 ppm), respectively, using double-beam UV-visible spectrophotometry and HPLC methods. These techniques use recovery rates ranging from 95 to 111% to determine the phloxine B dye that has been spiked in disclosing tablets and toothpaste samples. [ABSTRACT FROM AUTHOR]

The peroxidase-like properties of a graphene oxide/platinum-cobalt nanocomposite and the rapid color development mechanism of 3,3′,5,5′-tetramethylbenzidine (TMB) through the decomposition of ·OH from H2O2 were utilized to prepare a nonlabelled, simple, and sensitive paper-based colorimetric sensor. This sensor allows visualization of the results and instantaneous detection, enabling quantitative measurement of H2O2. The graphene oxide/platinum cobalt composite was synthesized using a two-step procedure. Its properties were investigated using transmission electron microscopy (TEM), Raman spectroscopy, and energy-dispersive X-ray spectroscopy (EDS). The composite was subsequently transferred onto a paper substrate to create the colorimetric sensor. The optimal catalytic conditions were a composite concentration of 201.17 µg/mL, a color development time of 3 min, a TMB concentration of 2 mmol·L−1, and a pH of 4. Using the optimal conditions, the paper-based colorimetric sensor has a linear range for H2O2 from 1.0 × 10−5 to 0.1 mol·L−1, with a limit of detection of 1.0 × 10−6 mol·L−1 which is comparable or better than comparable methods. This paper-based colorimetric sensor has potential applications for the rapid determination of hydrogen peroxide. [ABSTRACT FROM AUTHOR]

A method with rapid, sensitive, accurate, and selective for estimation of local anesthetic procaine hydrochloride (PRO.HCl) is crucial, due to its bad damage to health if administrated excessively. In this work two spectrophotometric methods oxidative coupling and cloud point extraction (CPE) were utilized for determination of PRO.HCl in its standard state and pharmaceutical preparations. Method A, based on the oxidative coupling reaction using sodium hypochlorite as an oxidant and 2,5-dimethylphenol as coupling agent. The blue colored product has high absorption at 600 nm. Method B based on the CPE relying on the previous reaction, with addition of Triton X-114, after extracting the colored product, it was measured at 630 nm. Beer's law of both methods are linear in the concentration ranges 2.50-50 µg/mL (method A) and 1.25-3.75 µg/mL (method B). The molar absorptivity coefficients of methods (A) and (B) are 4.01 x 103 and 1.34 x 104 L/mol.cm, respectively. For (method A) limit of detection and limit of quantification were calculated and found that 0.26 µg/mL and 0.87 µg/mL, respectively, while for (method B) were found to be 0.16 and 0.54 µg/mL, respectively. Both methods (A and B) are applied to evaluate PRO.HCl in pharmaceutical preparations (injection). [ABSTRACT FROM AUTHOR]