Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy最新文献

Albumin is undoubtedly the most studied protein thanks to its widespread diffusion and biochemistry; despite its binding ability towards different dyes, provoking dye's colour change, has been exploited for decades for quantification purposes, the joint effect of working pH, ionic strength, and dye's pK_a still remains only sporadically discussed. In the present study, the interaction of Bovine Serum Albumin (BSA) with five dyes belonging to the sulfonephthalein group, Bromophenol Blue (BPB, pK_a = 3.75), Bromocresol Green (BCG, pK_a = 4.42), Chlorophenol Red (CPR, pK_a = 5.74), Bromocresol Purple (BCP, pK_a = 6.05) and Bromothymol Blue (BTB, pK_a = 6.72), is investigated at four working pH values (3.5, 6.0, 7.5 and 9.0) and two ionic strength conditions by UV-Vis spectroscopy. Principal Component Analysis is then applied to rationalize dye behavior upon BSA addition at each pH value and to summarize the protein effect on dyes' spectral features, identifying three general behaviors. The most relevant systems are then submitted to further characterization involving a solution equilibria study aimed at determining conditional binding constants for the selected DSA-dye adducts and fluorescence, CD, and ¹H NMR spectroscopy to evaluate the binding effect on the species involved.

Esophageal cancer is one of the leading causes of cancer-related deaths worldwide. The identification of residual tumor tissues in the surgical margin of esophageal cancer is essential for the treatment and prognosis of cancer patients. But the current diagnostic methods, either pathological frozen section or paraffin section examination, are laborious, time-consuming, and inconvenient. Raman spectroscopy is a label-free and non-invasive analytical technique that provides molecular information with high specificity. Here, we report the use of a portable Raman system and machine learning algorithms to achieve accurate diagnosis of esophageal tumor tissue in surgically resected specimens. We tested five machine learning-based classification methods, including k-Nearest Neighbors, Adaptive Boosting, Random Forest, Principal Component Analysis-Linear Discriminant Analysis, and Support Vector Machine (SVM). Among them, SVM shows the highest accuracy (88.61 %) in classifying the esophageal tumor and normal tissues. The portable Raman system demonstrates robust measurements with an acceptable focal plane shift of up to 3 mm, which enables large-area Raman mapping on resected tissues. Based on this, we finally achieve successful Raman visualization of tumor boundaries on surgical margin specimens, and the Raman measurement time is less than 5 min. This work provides a robust, convenient, accurate, and cost-effective tool for the diagnosis of esophageal cancer tumors, advancing toward Raman-based clinical intraoperative applications.

In this study, AgNPs-loaded polyurethane-sodium alginate (PU-S/Alg) composite polymers were prepared by precipitation polymerization and in-situ reduction method. Their catalytic potential was evaluated for the reduction of methyl orange (MO), brilliant blue (BB), Rhodamine B (RhB), 4-nitroaniline (4-NA), and 4-nitrophenol (4-NP). Successful preparation of samples was confirmed by UV-Visible spectrophotometry (UV-Visible), Fourier transform infrared (FTIR), and Scanning electron microscopy (SEM) analysis. During the catalytic study, the value of k_app for the reduction of MO in the presence of NaBH₄ and catalyst was found 0.488 min^-1 while, in the presence of NaBH₄ and catalyst alone, were found as 0.9 × 10^-4 and 0.8 × 10^-5 min^-1, respectively which indicates the role of catalyst in making the reaction speedy. The value of k_app for the reduction of BB, RhB, 4-NA, and 4-NP was found as 0.764, 0.475, 0.212 and 0.757 min^-1, respectively. Simultaneous reduction of dyes induced a decreased reaction completion time under the same reaction conditions. A slight increase in the value of k_app for the catalytic reduction of MO was also observed when reactions were performed in the presence of ionic media of different salts such as NaCl, KCl, CaCl_2, and MnCl₂. The rate of reduction of MO was increased with the increase in ionic strength of the medium. However, the presence of SDS (surfactant) in the reaction mixture induced the decreased activity of the catalyst and increased reaction completion time. The same value of k_app for the reduction of MO was observed in the case of freshly prepared and several days old nanocomposite catalyst. These results illustrate the stability and maintained catalytic potential of metal NPs for a prolonged time. Our reported catalyst also showed good potential for the treatment of dyes-polluted textile industry wastewater.

This study focuses on the adsorption process of L-cysteine (Cys), a sulfur-containing amino acid, onto monolayers of gold nanoparticles (AuNPs) prepared through distinct protocols on mica substrates. Two types of AuNPs were prepared using two different methods: the first employed a physical approach, which combined the Inert Gas Condensation (IGC) technique with the magnetron sputtering method, while the second utilized a chemical method involving the reduction of tetrachloroauric acid with trisodium citrate (TC). The characterization of AuNPs was performed using transmission electron microscopy (TEM) and atomic force microscopy (AFM), of up to 5 ± 1.3 nm for bare AuNPs obtained through vacuum techniques, and up to 12 ± 5 nm for negatively charged, citrate-stabilized TCAuNPs(-). The application of spectroscopic techniques based on the surface-enhanced effects allows for describing the adsorption process in both micro- and nanoscale systems: Cys/bare AuNPs and Cys/ TCAuNPs(-). The commonly used surface-enhanced Raman spectroscopy (SERS) technique provided insights into adsorption behaviours at the microscale level. In the case of TCAuNPs(-), an interaction involving the lone electron pair of sulfur (S) atom and metal surface, while on the bare AuNPs, S is adsorbed on the surface, but the cleavage of the SH group is not discernible. Nanoscale analysis was complemented using AFM combined with the surface-enhanced infrared absorption spectroscopy (AFM-SEIRA) technique. AFM-SEIRA map indicated the formation of hot spot which were predominantly located between aggregated TCAuNPs(-) and on specific NPs surfaces (area between NPs and gold-coated tip). Results from the SERS and AFM-SEIRA techniques were in good agreement, underscoring the comprehensive understanding achieved through the chosen experimental approach regarding the Cys interactions with layers of AuNPs.

A novel bis(salamo)-type sensor FT for fluorescence-colorimetric recognition of Fe³⁺/Cu²⁺ has been created, which revealed significant fluorescent performance and colorimetric sensing ability for Cu²⁺ and Fe³⁺ ions, superior to other related competitive metal ions. Interestingly, the binding of the FT probe with Cu²⁺ ions manifested an instant color change from colorless to red in sunlight, which is detectable by the naked-eye, and a fluorescence turn-off response under UV light for Fe³⁺ and Cu²⁺. The results demonstrated that the probe exhibits better sensitivity, greater affinity and lower limit of detection leading to quick response time in an aquo-organic medium. The excited state property of the FT probe and in the presence of Cu²⁺/Fe³⁺ was evaluated on the basis of DFT & TD-DFT results. Furthermore, test strips have been provided for convenient monitoring of Cu²⁺ and Fe³⁺ ions by naked eye and fluorescence method.