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Akyl urea derivatives, either symmetrical or unsymmetrical in nature possessing a free N-H or N-alkyl moieties in the molecular framework of urea governs the excited state properties of acridinedione dye (ADR1) which is a resorcinol-based derivative. Fluorescence enhancement (FE) of ADR1 dye is observed on the addition of unsymmetrical urea derivatives, whereas a decrease in the fluorescence intensity resulted upon the addition of symmetrical urea derivatives. The nature of the urea derivatives controls the suppression of photoinduced electron transfer (PET) via space, which is the cause of the FE. FQ results from the donor and acceptor moieties of ADR1 dye promoting the PET process. Urea (U), symmetrical and unsymmetrical urea derivatives (except Tetramethyl urea (TMU)) results no significant shift of the localized excited (LE) state emission of ADR1 dye. Studies of the ADR1 dye’s fluorescence lifetime in the presence of urea compounds show a significant increase in lifetime. This phenomenon is explained by a significant difference in the hydrogen-bonding (HB) pattern, which causes variation in the microenvironment created by the solute molecules in the aqueous phase. Both the hydrophobic effects of the alkyl group substituents in the urea molecular framework and the HB interactions between the solute and solvent influence the excited state features of ADR1 dye. Further, the role of urea derivatives and ADR1 dye (both are considered as competitive guest molecules) energetics and molecular interactions were studied in the presence of host molecule, Human Serum Albumin (HSA). The binding energy (BE) and several bimolecular interactions driven by urea derivatives in the presence of ADR1-HSA complex in comparison with that of urea derivatives-HSA complex were investigated by molecular docking (Mol.Doc) methodology. Incorporating theoretical research along with steady state and time-resolved fluorescence investigations proved to be an effective method to evaluate the interactions of competing solutes comprising both hydrophobic and HB functional groups.

One of the most popular single-molecule approaches in biological science is single-molecule fluorescence microscopy, which will be the subject of the following section of this volume. Fluorescence methods provide the sensitivity required to study biology on the single-molecule level, but they also allow access to useful measurable parameters on time and length scales relevant for the biomolecular world. Before several detailed experimental approaches will be addressed, we will first give a general overview of single-molecule fluorescence microscopy. We start with discussing the phenomenon of fluorescence in general and the history of single-molecule fluorescence microscopy. Next, we will review fluorescent probes in more detail and the equipment required to visualize them on the single-molecule level. We will end with a description of parameters measurable with such approaches, ranging from protein counting and tracking, single-molecule localization super-resolution microscopy, to distance measurements with Förster resonance energy transfer and orientation measurements with fluorescence polarization., (© 2024. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

We outline our approach for studying the selective autophagy of peroxisomes (pexophagy), using fluorescence microscopy in tissue cell culture models. Ratiometric reporters, which specifically localize to peroxisomes, allow a quantitative assessment of pexophagy in fixed and live cells, as well as whole organisms. We discuss chemical and physiological inducers of pexophagy and any overlap with the induction of mitophagy., (© 2024. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

The article presents the history of the development and the current state of the apparatus for the detection of interferents and biological warfare simulants in the air with the laser-induced fluorescence (LIF) method. The LIF method is the most sensitive spectroscopic method and also enables the measurement of single particles of biological aerosols and their concentration in the air. The overview covers both the on-site measuring instruments and remote methods. The spectral characteristics of the biological agents, steady-state spectra, excitation–emission matrices, and their fluorescence lifetimes are presented. In addition to the literature, we also present our own detection systems for military applications.

The article presents the history of the development and the current state of the apparatus for the detection of interferents and biological warfare simulants in the air with the laser-induced fluorescence (LIF) method. The LIF method is the most sensitive spectroscopic method and also enables the measurement of single particles of biological aerosols and their concentration in the air. The overview covers both the on-site measuring instruments and remote methods. The spectral characteristics of the biological agents, steady-state spectra, excitation-emission matrices, and their fluorescence lifetimes are presented. In addition to the literature, we also present our own detection systems for military applications.

Objective: Improvement of methods for studying the processes of demineralization of hard tissues of temporary teeth., Material and Methods: The study included primaries second molars ( n =11). Samples of primary teeth were placed in a test tube with a demineralizing solution for - 1, 4, 8, 21 and 31 days. The of primary teeth samples were examined using methods - laser induced fluorescence (LIF) and autofluorescence microscopy (AFM). Assessment of the degree of demineralization of samples of temporary teeth was carried out according to the score scale developed by us., Results: The enamel of the samples is demineralized slowly and evenly for up to 8 days with minimal objective signs, starting from the 8th day of the experiment, there is a significant increase in demineralization indicators. By the 21st day, the peak of demineralization is reached with partial dissolution of the enamel, an increase in the fluorescence effect to 80 UE, and reaches a maximum of 4 points on the evaluation scale. Dentin's hard tissues are demineralized gradually without "sudden jumps" in the fluorescence effect and at the same rate throughout the experiment, reaching a maximum on 31 days (30 UE - LIF). Dentin demineralization is characterized by less dissolution, however, the phenomenon of delamination is determined by the type of exfoliation of the organic dentin matrix, starting from the 21st day of the experiment., Conclusion: Enamel and dentin of deciduous teeth demineralize at different rates and have a characteristic specificity of morphological changes. Logistic regression analysis showed the consistency of the classifier for the predictive accuracy of each unit of the proposed scale for assessing the degree of demineralization of temporary teeth samples.

Many biomolecular condensates, including nucleoli and stress granules, form via dynamic multivalent protein-protein and protein-RNA interactions. These molecular interactions nucleate liquid-liquid phase separation (LLPS) and determine condensate properties, such as size and fluidity. Here, we outline the experimental procedures for single-molecule fluorescence experiments to probe protein-RNA interactions underlying LLPS. The experiments include single-molecule Förster (Fluorescence) resonance energy transfer (smFRET) to monitor protein-induced conformational changes in the RNA, protein-induced fluorescence enhancement (PIFE) to measure protein-RNA encounters, and single-molecule nucleation experiments to quantify the association and buildup of proteins on a nucleating RNA. Together, these experiments provide complementary approaches to elucidate a molecular view of the protein-RNA interactions that drive ribonucleoprotein condensate formation., (© 2023. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

The optimal harvesting of table grapes is commonly determined based on technological and phenolic indices analyzed over the course of its maturity. The classical techniques used for these analyses are destructive, time-consuming, and work for a limited number of samples that may not represent the heterogeneity of the vineyard. This study aimed to follow the ripening season of table grapes using non-destructive tools as a rapid and accurate alternative for destructive techniques. Grape samples were collected from a Sugranineteen vineyard during the ripening season to measure the basic maturity indices via wet chemistry, and total polyphenols, anthocyanins, and flavonoids were evaluated by spectrophotometry. Fluorescent readings were collected from intact clusters with a portable optical sensor (Multiplex® 3, Force-A, France) that generates indices correlated to different maturity parameters. Results revealed strong relationships between the Multiplex® indices ANTH_RG and FERARI and the skin anthocyanin content, with R2 values equal to 0.9613 and 0.8713, respectively. The NBI_R index was also related to total anthocyanins (R2 = 0.8032), while the SFR_R index was linked to the titratable acidity (R2 = 0.6186), the sugar content (R2 = 0.7954), and to the color index of red grapes (CIRG) (R2 = 0.7835). Results demonstrated that Multiplex® 3 can be applied on intact clusters as an effective non-destructive tool for a rapid estimation of table grapes’ anthocyanin content.

Advanced glycation end products (AGEs) are non-enzymatic modifications of proteins and lipids, which are spontaneously produced in the body in relation with several human diseases. Their relevance on protein functions alteration, either structural or enzymatic is under study, but their value as biomarkers or predictors of disease progression and clinical outcomes is unquestionable. The heterogeneity and amplitude of these modifications make their analysis difficult, although, different methods have been developed for specific AGEs based on colorimetric reactions, immunoassays or chromatography. However, for a massive application on human population, methods based on the autofluorescence of some AGEs stand out. Several qualities of these methods such as label-free measurement, rapidity, cost-effectiveness, and minimal invasiveness make them very useful for periodic measurements in critically ill patients and for the analysis of large populations. Here we explain the rationale of these methods, and we present a step-by-step protocol and the equipment requirements to carry out the estimation of AGE content in skin and plasma. AGE plasma content and skin accumulation are temporally related, so AGE plasmatic levels are a possible predictor of skin AGE content. On the other hand, AGE skin accumulation is a surrogate or an indicator of past AGE levels in plasma and in the rest of the body. AGE levels or their variations have shown to be related with prognosis of several diseases, so they can be used as predictor biomarkers for clinicians., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background: The VELscope fluorescence method has been applied to the identification and detection of oral potentially malignant disorders, but autofluorescence visualization lacks objectivity and its diagnostic value varies greatly. The effectiveness of VELscope in detection of the cancer risk in oral potentially malignant disorders at different lesion sites remains unclear, given that only a few studies have investigated the value of VELscope for detecting high- and low-risk lesions in oral potentially malignant disorders. This study used the objective VELscope fluorescence method based on quantitative analysis to investigate its value in oral potentially malignant disorders for: (I) detecting oral cancer; (II) distinguishing high-risk lesions from low-risk lesions; and (III) measuring differences in oral cancer diagnostic accuracy between different sites., Methods: Conventional oral examination and subjective and objective VELscope examinations were performed on 59 oral potentially malignant disorders; autofluorescence results were compared with histopathological diagnosis., Results: The sensitivity of subjective and objective VELscope fluorescence methods for detecting oral cancer in oral potentially malignant disorders was 76.9% and 65.4%, respectively; specificity for distinguishing high-risk from low-risk lesions in oral potentially malignant disorders was 50.0% and 82.1%, respectively; and sensitivity for detecting oral cancer in oral potentially malignant disorders of lining mucosa was 81.0%, higher than that of the masticatory mucosa., Conclusions: The identification ability for low-risk lesions can be improved by combining it with objective autofluorescence. Autofluorescence has different screening abilities in different parts of the oral mucosa., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tcr.amegroups.com/article/view/10.21037/tcr-21-2804/coif). The authors have no conflicts of interest to declare., (2022 Translational Cancer Research. All rights reserved.)

This systematic review and meta-analysis aimed to investigate the efficacy of fluorescence-based methods, visual inspections, and photographic visual examinations in initial caries detection. A literature search was undertaken in the PubMed and Cochrane databases. Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines were followed, and eligible articles published from 1 January 2009 to 30 October 2019 were included if they met the following criteria: they (1) assessed the accuracy of methods of detecting initial tooth caries lesions on occlusal, proximal, or smooth surfaces in both primary and permanent teeth (in clinical); (2) used a reference standard; (3) reported data regarding the sample size, prevalence of initial tooth caries, and accuracy of the methods. Data collection and extraction, quality assessment, and data analysis were conducted according to Cochrane standards Quality Assessment of Diagnostic Accuracy Studies-2. Statistical analyses were performed using Review Manager 5.3 and STATA 14.0. A total of 12 eligible articles were included in the meta-analysis. The results showed that the sensitivity and specificity of fluorescence-based methods were 80% and 80%, respectively; visual inspection was measured at 80% and 75%, respectively; photographic visual examination was measured at 67% and 79%, respectively. We found that the visual method and the fluorescence method were reliable for laboratory use to detect early-stage caries with equivalent accuracy.