Fluorescence Studies Research Articles

RuIII-Morpholine-Derived Thiosemicarbazone-Based Metallodrugs: Lysosome-Targeted Anticancer Agents.

The idea of coordinating biologically active ligand systems to metal centers to exploit their synergistic effects has gained momentum. Therefore, in this report, three RuIII complexes 1-3 of morpholine-derived thiosemicarbazone ligands have been prepared and characterized by spectroscopy and HRMS along with the structure of 2 through a single-crystal X-ray diffraction study. The solution stability of 1-3 was tested using conventional techniques such as UV-vis and HRMS. Further, the anticancer activity of 1-3 was tested in HT-29 and HeLa cancer cell lines. To gain insight into their mechanism of action, the cytotoxicity, hydrophobicity, and the interaction of 1-3 with DNA and HSA were evaluated by different conventional methods such as absorption, fluorescence, and circular dichroism studies. Along with favorable biomolecule interaction, 1-3 revealed potent selectivity toward cancer cells, which is a prerequisite for the generation of an anticancer drug. According to cell viability results, 1 has the highest cytotoxicity among all in the group, against both cells, respectively. Additionally, the fluorescence-active ruthenium complexes selectively target lysosomes, which is evaluated by live-cell imaging. 1-3 disrupt the lysosome membrane potential by generating an excessive amount of reactive oxygen species, which results in an apoptotic mode of cell death.

Synthesis, structural characterization, and optical properties of two Co(II)-based coordination compounds

Two new Co(II)-based coordination compounds, [Co(Hmctrz)2(H2O)2] (1) and [Co(Hdctrz)(H2O)2]n (2), were synthesized via routine or hydrothermal reactions using cobalt salts, triazole derivatives, and auxiliary reagents. Characterizations, including single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, TGA, and PXRD, confirmed their formation. UV-Vis and fluorescence studies revealed distinct optical properties, with 1 and 2 exhibiting UV absorption peaks at 353 and 370 nm, respectively, and concentration-dependent fluorescence emission, indicating potential for optoelectronic and biological imaging applications. Additionally, adsorption studies showed excellent dye removal capabilities, with 1 achieving 98% removal of methylene blue (MB) and 93% of methyl orange (MO), outperforming 2, which removed 95% of MB and 87% of MO. These results highlight the compounds’ potential in both environmental remediation and advanced material applications.

Assessing the role of Berberine as an inhibitor of advanced glycation end products (AGEs) formation using in vitro and molecular interaction studies.

Glycation and aggregation of proteins have garnered more interest in recent years. Glycation leads to the formation of protein aggregates and advanced glycation ends (AGEs) that play crucial roles within several pathological conditions. The objective of our study is to gain a deeper understanding of the formation of AGEs and aggregates of human serum albumin (HSA) in the presence of methylglyoxal and the protective effects of the phytochemical berberine. HSA was incubated with methylglyoxal and different concentrations of berberine for 7-14 days at 35-37 °C. Methylglyoxal resulted in the formation of AGEs, fibrillar aggregates, and hydrophobic protein patches in HSA, as was evident from AGE fluorescence, ThT and ANS fluorescence studies. It also disrupted the secondary structure of HSA shown by CD spectroscopy. All these parameters were restored towards native HSA in the glycated HSA + berberine samples. Molecular docking was employed to identify the critical HSA residues implicated in the HSA-berberine interaction and also to determine the spontaneous binding of berberine on the HSA sub-domain favoring the thermodynamic binding. The binding energy between HSA-berberine was found to be -9.1 kcal/mol. Various types of forces like hydrophobic interactions, polar forces, hydrogen bonds, etc are were at play between the HSA and berberine interaction. Since MGO level is increased in pathological conditions such as type II diabetes, there is a chance that increased MGO concentration could cause glycation of HSA, leading to decreased levels of HSA, as observed in pathological circumstances. The binding of berberine to lysine and arginine residues might be linked to its antiglycation potential as these amino acids play an important role in the glycation of proteins. Nevertheless, additional inquiries are needed to substantiate this claim. Thus, our study characterizes AGEs and aggregates of clinically important protein HSA.

A Carbazole Acrylonitrile Substituted Turn-On Fluorescence Chemosensors for Cyanide Ion and its Application to Real Sample Analysis.

An efficient probe (E)-2-(benzo[d]thiazol-2-yl)-3-(9-ethyl-9H-carbazol-3-yl)acrylonitrile (CZ-BTZ) for selective fluorescence "turn-on" response with cyanide (CN-) ion sensor was developed by simple Knoevenagel condensation of 9-ethyl-9H carbazole-3-carbaldehyde with 2-(benzo[d]thiazol-2-yl) acetonitrile. The sensing ability of probe CZ-BTZ was tested with different inorganic anions through spectrophotometric and spectrofluorimetric methods. The UV-vis and fluorescence spectral studies show the formation of a new adduct between CZ-BTZ and CN- by appearing with a new absorbance band at 350nm and "turn-on" fluorescence at 535nm in CH3CN: H2O (8:2, v/v, pH 7.2). The absorbance and fluorescence study reveals the formation of 1:1 (CZ-BTZ: CN-) stoichiometry adducts with an estimated association constant of 2.04 × 105 M-1. The probe CZ-BTZ could detect CN- down to 4.19 nM without much interference, much lower than the WHO limit (1.9 µM) in drinking water. The sensing mechanism of CZ-BTZ with CN- ions was studied using FTIR, ESI mass analysis, and DFT calculation. Further, the probe was applied to analyse CN- ions' real-time food sample analysis.

Ligand binding characteristics of an NAD+ riboswitch revealed by FRET and biolayer interferometry.

The Class II NAD+ riboswitch is a bacterial RNA that binds ligands containing nicotinamide. Herein, we report a fluorescence and biolayer interferometry study of riboswitch interactions with β-NMN. The results reveal a shift in the prevalence of a pseudoknot structure in the presence of ligand and Mg2+.

Time-resolved fluorescence studies reveal differences in dynamic motion between main proteases of SARS-CoV-2 and SARS-CoV

The main protease (Mpro) is an attractive drug target for inhibiting the coronavirus. Lots of research has focused on the static viewpoint of the Mpro, such as the X-ray crystal structure, inhibitors design, and the transition between monomer and dimer. However, the attention to the dynamical features of Mpro is limited, which is essential for a deeper determination of the properties of the target protein. In our research, we constructed three single-tryptophan mutants (W31IN, W207IN, and W218IN) of Mpro from SARS-CoV-2 and SARS-CoV to monitor the motion of Mpro at the nano-second timescale using the time-resolved fluorescence assay. We found that the temperature-dependent Stokes shift results show various behaviors among the three single-tryptophan mutants: the microenvironment around the Trp207 residue is more temperature-sensitive compared to that in residues Trp31 and Trp218. The molecular dynamic simulation results further support that MproSARS is more flexible than that of MproSARS2. This difference is directly related to the distinct perturbations of residues Phe185 to Gln192, a loop that connects domain II and domain III. For the first time, we were able to reveal the different motions between MproSARS2 and MproSARS, although the static structures of these two are not distinguished. The differences in dynamics would be an essential step towards understanding the evolving trend of coronavirus, providing a comprehensive view of the properties of Mpro, and offering perspectives for designing inhibitors for further research.

Green synthesis of γ-Fe2O3@SiO2 magnetic nanoparticles functionalized with penciclovir drug: antiproliferative effect, and nucleic acids (DNA and RNA) interaction

This study focuses on generating single-phase maghemite (γ-Fe2O3) using Echinophora platyloba DC. (E. platyloba) extract, followed by a silica coating. Subsequently, the γ-Fe2O3@SiO2 magnetic nanoparticles (γ-Fe2O3@SiO2 MNPs) are functionalized with the antiviral drug penciclovir (PNV). The objective of this research is to produce a dual-function therapeutic agent that exhibits both antiviral and anticancer properties. Nanoparticles were characterized using FT-IR, VSM, XRD, TEM, SEM-EDX, DLS, zeta potential measurements, and ultraviolet–visible analysis. The γ-Fe2O3@SiO2-PNV MNPs exhibited lower toxicity towards normal fibroblast cells compared to cancerous MCF-7 cells. Furthermore, loading PNV onto γ-Fe2O3@SiO2 MNPs resulted in a significant increase in the anticancer and biological effects of PNV. To assess the therapeutic potential of γ-Fe2O3@SiO2-PNV MNPs, their interactions with nucleic acids (DNA and RNA) were investigated through absorption and fluorescence studies. The experimental findings showed that γ-Fe2O3@SiO2-PNV MNPs had a strong propensity for binding to nucleic acids both through the groove and intercalate (partial intercalation), indicating their promising candidacy as a targeted and specific chemotherapeutic agent.

Solvent‐Assisted Prototopic Switching of Norharmane Along Hydrogen‐Bonded Network: Assessing the Precise Length of Network

ABSTRACTIn this article, the proton transfer dynamics along a stable norharmane•(H2O)n (n = 2–4) hydrogen‐bonded cluster on conversion from the neutral to cationic form of norharmane (NHM) in water medium was demonstrated experimentally and theoretically. The distinct absorption and emission bands of different prototropic forms of NHM are well‐known in the literature. Initially, the conversion from neutral to cationic form of NHM on moving from a polar aprotic (acetonitrile) to a polar protic (water) solvent was ensured by steady‐state absorption and fluorescence studies. The analysis of IR spectra and steady‐state anisotropy data of NHM confirmed the possibility of the formation of a hydrogen‐bonded network in the presence of water. The length of the network was explored and assumed by extensive Density Functional Theory (DFT) calculations. Then, by time‐dependent density functional theory (TD‐DFT), the excited state proton transfer (ESPT) pathway was established interrogating the NHM‐water cluster with different numbers of water molecules. The theoretical analysis assured that the NHM•(H2O)2 cluster was incapable of maintaining the stable hydrogen bonding wire in the course of the ESPT mechanism. Rather, NHM•(H2O)3 and NHM•(H2O)4 clusters were simultaneously involved in operating the ESPT mechanism. The NHM•(H2O)4 cluster was more feasible to carry out the proton transfer than the NHM•(H2O)3 cluster. To the best of our knowledge, this was possibly the first theoretical evidence behind the conversion from neutral to cationic form of NHM via the formation of a hydrogen‐bonded network.

New lanthanum (III) complexes containing azaphosphor β-diketon and diimine ligands: Synthesis, crystallography, morphology properties, DNA binding, DNA cleavage, and DFT calculation.

Two octa-coordinated lanthanum (III) complexes of deprotonated azaphosphor β-diketon and diimine ligands, [LnL3Q] (L=[Cl2CHC(O)NP(O)(NC6H12)2], Q=Phen (C1) and Bipy (C2)), were synthesized and characterized by elemental analysis, IR, and NMR spectra. X-ray crystallography revealed a distorted tetragonal antiprism LaO6N2 coordination geometry around the lanthanum atom in both compounds. Nano-sized complexes (Ć1 and Ć2) were synthesized via a sonochemical process and analyzed using SEM and XRPD. TGA-DTA analysis were performed on complexes in both bulk and nano scales. Redox behavior was also examined by cyclic voltammetry. The interaction between the complexes and calf thymus DNA (ct-DNA) was investigated using UV-Vis spectroscopy, fluorescence titration, viscosity measurements, and gel electrophoresis. C2 and Ć2 likely intercalate between DNA base pairs through van der Waals forces and hydrogen bonding, whereas C1 and Ć1 interact with DNA via groove binding. Further, result indicated the apparent association constant (Kapp) in the range of 4.53×104M-1-26.86×104M-1 with the highest value for nanocomplex Ć2. Fluorescence studies revealed dynamic and static quenching for C1, while the other compounds followed a static quenching process. Hirshfeld surface analysis and the NCI method were employed to demonstrate how non-covalent interactions influence the crystal packing through intermolecular interactions.

Ultra-Sensitive Abscisic Acid Detection Using Gold and 4-Mercaptopyridine Perovskite-Engineered Robust Nanofibers (GLAMPER-NFs) under Surface-Enhanced Raman Spectroscopy.

This study explores the development and application of gold and 4-mercaptopyridine (MPY) perovskite-engineered robust nanofibers (GLAMPER-NFs) for the ultrasensitive detection of Abscisic acid (ABA) under Raman spectroscopy, a crucial plant hormone. The GLAMPER-NFs composite material, consisting of MAPbCl3 nanofibers integrated with MPY-coated gold nanostructures, demonstrates exceptional performance in surface-enhanced Raman scattering (SERS)-based sensing. The study elucidates the material structure and properties through comprehensive characterization using scanning electron microscopy (SEM), UV-vis spectroscopy, fluorescence spectroscopy, Fourier transform infrared, and Raman spectroscopy. The SEM analysis reveals uniform nanofibers with diameter of 107.8 ± 3.06 nm, while spectroscopic studies confirm the successful synthesis and integration of the composite components. The SERS-based detection of ABA showcases remarkable sensitivity, with a linear detection range (R2 = 0.9957) spanning 7 orders of magnitude (10-14-10-7 M) and presented a limit of detection of 10-11 and enhancement factor of 1.08 × 107. This surpasses the performance of existing sensing platforms, demonstrating clear spectral responses even at femtomolar concentrations. The synergistic effects of the perovskite structure, plasmonic gold nanoparticles, and MPY linking molecules contributed exceptional sensing capabilities to the GLAMPER-NFs material. Fluorescence studies further corroborate the sensitivity and provide insights into the photophysical interactions between ABA and the composite material. This research advances the understanding of perovskite-based hybrid materials and presents a promising GLAMPER-NFs as SERS substrate for ultrasensitive plant hormone detection, with potential applications in agricultural monitoring and plant science research.

Photophysical and Docking Studies of Schiff Base Coupled Silane: A Probe for Sn2+ Detection and PI3Kα Inhibitor for Cancer Treatment

ABSTRACTCancer, a leading cause of death globally, necessitates clinical research to develop effective solutions to reduce mortality rates. Currently, scientists are focusing on two prominent topics in cancer treatment: the presence of Sn2+ in cells and the inhibition of the phosphoinositide 3‐kinase enzyme (PI3Kα). In this study, Schiff base‐coupled silane 7a {C26H35N5O6Si (M + H+ = 540.53)} has been synthesized that could detect Sn2+, which in trace amounts can help prevent cancer, and it also inhibits PI3Kα enzyme, thereby preventing the rapid proliferation of cancer cells. The detection limit and binding constant calculated via Fluorescence studies were found to be 3.46 × 10−8 M and 9.4 × 104 M−1, respectively. The value of inhibition constant of silane for PI3Kα enzyme was also found to be 2.52 nM via molecular docking.

Ex Vivo Human Tissue Functions as a Testing Platform for the Evaluation of a Nerve-Specific Fluorophore.

Selecting a nerve-specific lead fluorescent agent for translation in fluorescence-guided surgery is time-consuming and expensive. Preclinical fluorescent agent studies rely primarily on animal models, which are a critical component of preclinical testing, but these models may not predict fluorophore performance in human tissues. The primary aim of this study was to evaluate and compare two preclinical models to test tissue-specific fluorophores based on discarded human tissues. The secondary aim was to use these models to determine the ability of a molecularly targeted fluorophore, LGW16-03, to label ex vivo human nerve tissues. Patients undergoing standard-of-care transtibial or transfemoral amputation were consented and randomized to topical or systemic administration of LGW16-03 following amputation. After probe administration, nerves and background tissues were surgically resected and imaged to determine nerve fluorescence signal-to-background tissue ratio (SBR) and signal-to-noise ratio (SNR) metrics. Analysis of variance (ANOVA) determined statistical differences in metric means between administration cohorts and background tissue groups. Receiver operating characteristic (ROC) curve-derived statistics quantified the discriminatory performance of LGW16-03 fluorescence for labeling nerve tissues. Tissue samples from 18 patients were analyzed. Mean nerve-to-adipose SBR was greater than nerve-to-muscle SBR (p = 0.001), but mean nerve-to-adipose SNR was not statistically different from mean nerve-to-muscle SNR (p = 0.069). Neither SBR nor SNR means were statistically different between fluorophore administration cohorts (p ≥ 0.448). When administration cohorts were combined, nerve-to-adipose SBR was greater than nerve-to-muscle SBR (mean ± standard deviation; 4.2 ± 2.9 vs. 1.8 ± 1.9; p < 0.001), but SNRs for nerve-to-adipose and nerve-to-muscle were not significantly different (5.1 ± 4.0 vs. 3.1 ± 3.4; p = 0.055). ROC curve-derived statistics to quantify LGW16-03 nerve labeling performance varied widely between patients, with sensitivities and specificities ranging from 0.2-99.9% and 0.4-100.0%. Systemic and topical administration of LGW16-03 yielded similar fluorescence labeling of nerve tissues. Both administration approaches provided nerve-specific contrast similar to that observed in preclinical animal models. Fluorescence contrast was generally higher for nerve-to-adipose versus nerve-to-muscle. Ex vivo human tissue models provide safe evaluation of fluorophores in the preclinical phase and can aid in the selection of lead agents prior to first-in-human trials.

Green synthesis of ZnO nanoparticles: in-silico and in-vitro assessment of anticancer and antibacterial activity and biomolecule (DNA) binding analysis

The zinc oxide nanoparticles (ZnO NPs) were synthesized by a green chemistry approach utilizing Stachys schtschegleevii Sosn.) S. schtchegleevii (extract, aims to innovate by employing environmentally friendly techniques. The production of ZnO NPs was confirmed by FT-IR, zeta potential, TEM, SEM-EDX, DLS and ultraviolet-visible techniques. The antibacterial potency of the ZnO NPs was evaluated toward pathogenic strains of E. coli and S. aureus. The antibacterial efficacy of this NPs against the selected bacteria followed the sequence: S. aureus > E. coli. The results of the MTT assay indicate that ZnO NPs have significant anticancer potential against the MCF-7 cell line. Furthermore, the synthesized ZnO NPs demonstrate a stronger inhibitory effect compared to the extract on the cancer cell line. To find out the potential of ZnO NPs as therapeutics, interaction process with calf-thymus DNA (ct-DNA) was performed by using absorption, and fluorescence studies. The evaluation of the fluorescence spectra and UV–visible absorption showed a satisfactory association of the ZnO NPs with ct-DNA. Besides, to clarify the binding interactions of ZnO NPs with the enzymes and ct-DNA, molecular docking simulation was performed. The molecular docking’ results show a well compromise with our experimental results. In total, the present investigation employs ZnO NPs synthesized through green methods as an efficient strategy for the purpose of the potentiation of anticancer and antibacterial activities in a biocompatible manner.

Multispectroscopic and computational insights into amyloid fibril formation of alpha lactalbumin induced by sodium hexametaphosphate

The impact of sodium hexametaphosphate (SHMP) on the aggregation behavior of α-lactalbumin (α-LA) was studied at pH 7.4 and 2.0. Turbidity measurements showed a concentration-dependent aggregation of α-LA at pH 2.0 in the presence of SHMP, while no aggregation was observed at pH 7.4. Light scattering (LS) and Thioflavin-T (ThT) data revealed that the aggregation was rapid, following nucleation-independent pathways. In other kinetics experiments such as turbidity and ThT confirmed that SHMP-induced α-LA aggregation was dependent on SHMP concentration rather than incubation time. Once formed, the aggregates remained unchanged for up to five days. Intrinsic fluorescence studies indicated conformational changes in α-LA upon SHMP addition, and dye-binding assays with ThT and Congo Red demonstrated the formation of amyloid-like aggregates. Far-UV circular dichroism (CD) data suggested a structural transition from α-helical to β-structures in α-LA in the presence of SHMP at pH 2.0. Molecular docking studies confirmed stronger interactions between α-LA and SHMP at pH 2.0 (ΔG = −6.2 kcal/mol) compared to pH 7.4 (ΔG = −5.3 kcal/mol), driven by electrostatic forces and hydrogen bonding. These results suggest that SHMP induces amyloid-like aggregation of α-LA, particularly at acidic pH.

Designing of amiloride loaded citrate functionalized amorphous silica nanoparticles to investigate its genotoxic and cytotoxic potential

In the present work, silica-based nanocarrier for the anticancer drug, amiloride have been synthesized and characterized using various physicochemical techniques. The aim of this work emphasis on investigating the physicochemical properties and cytotoxic effects of citrate-functionalized amiloride loaded silica nanoparticles. Silica nanoparticles synthesis was carried out via condensation reaction, then coated by tris sodium citrate, followed by their functionalization using amiloride through EDC-NHS reaction. SEM and HR-XRD analysis indicated the formation of amorphous spherical silica nanoparticles. The existence of citrate coating was evident from FT-IR and TGA results, which were supported by DLS and zeta potential studies. The formation of amiloride conjugated citrate coated silica nanoparticles (SiNPs-Cit@Ami) was confirmed by the DLS, Zeta potential and UV-Visible spectroscopy. Size of SiNPs-Cit@Ami nanoparticles was found to be around 80nm using TEM. Additionally, these nanoparticles showed high loading efficiency and time-dependent release of amiloride. DNA binding studies were examined using UV–Visible, Fluorescence spectroscopic and Competitive fluorescence studies. The results indicate that SiNPs-Cit@Ami bind to Ct-DNA via minor groove binding mode. Furthermore, the cytotoxic effect of SiNPs-Cit@Ami on HepG2 cell lines was found to be higher than amiloride alone. Our findings suggest that SiNPs-Cit@Ami can be employed as a promising candidate for cancer mitigation.

Comparison of Human and Porcine Natural Tooth Fluorescence-A Scoping Study to Inform Research on Dental Materials and Forensic Dentistry.

Understanding human tooth structure fluorescence aids clinical and forensic dentistry, enabling tissue/material differentiation and the creation of esthetic restorative materials. Material manufacturers seek to replicate natural tooth fluorescence, necessitating the development of novel techniques to detect them. Procuring human teeth for research is challenging due to ethical and infection control standards, prompting a search for alternative models. This study compares visible light-induced fluorescence of porcine and human teeth to assess the value of porcine teeth as human analogs. Using a pulsed laser, an optimal fluorescence-inducing wavelength was determined, followed by comparing fluorescence spectra between species. Luminescence sensitivity and lifetimes were comparable between species, but spectral geometry differed. Porcine teeth, commonly used for dental material investigations, may not be suitable for dental fluorescence studies due to spectral differences. Accurately mimicking human tooth fluorescence remains complex. Further research is needed to develop reliable alternatives for dental fluorescence investigations that will advance clinical and forensic dentistry.

On the long-term storage of tissue for fluorescence and electron microscopy: lessons learned from rat liver samples

Occasionally, tissue samples cannot be processed completely and are stored under varying conditions for extended periods. This is particularly beneficial in interinstitutional studies where a given research setting may lack the expertise or infrastructure for sample processing, imaging and data analysis. Currently, there is limited literature available on the controlled storage of biological tissues in primary fixatives for fluorescence and electron microscopy. In this contribution, we mimicked various tissue storage scenarios by taking different fixation conditions, storage temperatures and storage durations into account. Rat liver tissue was used for its well-known diversity of cellular ultrastructure and microscopy analysis. Fluorescent labelling of actin, DNA and lipids were employed in conjunction with high-resolution electron microscopy imaging. Herein, we tested three different fixative solutions (1.5% glutaraldehyde, 0.4% glutaraldehyde and 4% formaldehyde and 4% formaldehyde) and stored samples for 1–28 days at room temperature and refrigerator temperature. We found that liver tissue can be stored for up to 2 weeks in a 0.4% glutaraldehyde + 4% formaldehyde fixative solution, while still enabling reliable fluorescent labelling and ultrastructural studies. Ultrastructural integrity was eminent up to 1 month using either glutaraldehyde or formaldehyde fixation protocols. When liver tissue is fixed with a mixture of 0.4% glutaraldehyde and 4% formaldehyde and stored at 4 °C, it retains its capacity for electron microscopy analysis for several years, but loses its capacity for reliable fluorescent labelling studies. In conclusion, we demonstrated that liver tissue can be stored for extended periods enabling profound structure–function analysis across length scales.

Synthesis and Properties of Covalently Linked Fluorescent Tetrads Containing Two BODIPYs and Two 3‐Pyrrolyl BODIPYs

AbstractTwo covalently linked fluorescent tetrads containing two BODIPY units and two 3‐pyrrolyl BODIPY units have been synthesized over a sequence of steps starting with bis(3‐pyrrolyl BODIPY) as the key precursor. Both covalently linked tetrads 6 and 7 were confirmed by HR‐MS and characterized and studied by 1D and 2D NMR, absorption, cyclic voltammetry, steady state and time‐resolved fluorescence techniques, and also by DFT and TD‐DFT methods. The tetrad 6 exhibited one strong absorption band at 680 nm whereas the tetrad 7 showed strong absorption bands at 510 nm and 648 nm corresponding to BODIPY and 3‐pyrrolyl BODIPY units respectively and the absorption band of tetrad 6 was bathochromically shifted due to effective π‐conjugation in tetrad 6 compared to tetrad 7. The electrochemical studies revealed that tetrads exhibit only two reductions indicating their electron deficient nature. The steady state and time‐resolved fluorescence studies invoked a possibility of singlet‐singlet energy transfer from BODIPY units to 3‐pyrrolyl BODIPY units in one of the tetrads upon selective excitation of BODIPY unit. In this tetrad, the BODIPY unit acts as an energy donor whereas the 3‐pyrrolyl BODIPY unit acts as an energy acceptor. The theoretical studies were corroborated with experimental results. Group webpage: https://ravikanthlab.wixsite.com/mysite/.

Strained Ion Pair Interactions-Driven Anion-Assisted Concerted Addition of Ketoximes/Aldoximes and Hydroxamic Acids to Glycals.

Oximes and hydroxylamides are notable for their role as coupling partners in organic synthesis. However, their direct application as acceptors in O-glycosylation with glycal donors remains largely unexplored. Herein, we introduce a novel 2-deoxy glycosylation method for synthesizing N-O linked glycosides facilitated by sterically strained 2,4,6-tri-tert-butylpyridinium salts. This approach offers a broad substrate range, high tolerance for functional groups, and easy scalability, resulting in glycosyl oximes and glycosyloxyamines with exclusive α-selectivity and excellent yields. The effectiveness of this method is showcased through functionalization of glycosylated products, late-stage modification of bioactive drug molecules, and disaccharide synthesis. This innovative strategy offers an alternative route and holds promise for wide-ranging applications in the construction of bioactive N-O-linked glycosides in the future. The unique catalytic mechanism by the sterically hindered pyridinium salt has been studied via 1H NMR, IR, UV-vis, and fluorescence studies.

Synthesis and structural characterization BODIPY-based compounds for fluorescence sensing of β-amyloid aggregates

Alzheimer's disease (AD) is a neurodegenerative disorder associated with aging. According to the amyloid cascade hypothesis, the aggregation and accumulation of β-amyloid (Aβ) peptides in the brain as Aβ plaques is a critical process in the pathogenesis of AD. Among the existing diagnosis methods, fluorescence detection of β-amyloid (Aβ) has emerged as an alternative method due to its advantages such as real-time detection, low cost, not exposed to radiation, and high resolution for early diagnosis of Alzheimer's disease (AD). In this study, we designed and synthesized BODIPY-based compounds (BODIPY-3, BODIPY-4 and BODIPY-5) for the fluorescence detection of Aβ aggregates. In the fluorescence studies for detecting Aβ, BODIPY-5 with the squaric acid ester unit at the meso position of the BODIPY core showed a promising effect with an 11.7 μM Kd value.