Surface-designed AuNPs-based fluorescent probe for ultra-sensitive detection of oral poultry antibacterial drug furaltadone via intermolecular hydrogen bonding.

Furaltadone (FTD), a nitrofuran drug, was primarily utilized as a very effective oral veterinary antibiotic, especially in poultry production farms. As a result, FTD, a form of carcinogen, might easily enter people via the food chain, leading to fatal cancers. As a result, it is critical to develop a quick and efficient approach for detecting FTD at extremely low concentrations. Considering the aforementioned purpose, pamoic acid (PA) capped gold nanoparticles (PA@AuNPs) were synthesized in spherical morphology (size 10-15 nm) using the method of chemical reduction and used as a fluorescent probe to detect FTD. The interaction between PA@AuNPs and FTD was validated by UV-vis, XRD, and FTIR methods. Microscopic images (FESEM and HRTEM) show that PA@AuNPs have varying morphologies including rod, triangle, hexagonal, and pentagonal, and average sizes of 20-50 nm after sensing FTD. The average surface roughness of PA@AuNPs was determined to be 46.75 nm using the AFM technique. The addition of FTD (0 → 100 µM) quenched the fluorescence emission intensity of PA@AuNPs at 436 nm (λ ex 353 nm) by 4-fold. This static quenching was confirmed by the formation of a ground state complex, PA@AuNPs·FTD, between AuNPs and FTD using fluorescence lifetime analysis. The presence of an isosbestic point at 412 nm in the UV-visible titration, as well as FTIR data, further demonstrated the existence of this ground state complex. PA@AuNPs revealed high sensitivity (LoD = 9.78 nM; K a = 1.0615 × 102 M-1) to FTD in water, resulting in a decrease in predicted quantum yield (Φ F) from 3.36% to 0.35%. To establish PA@AuNPs as a first-generation fluorescence probe for real samples, FTD in blood serum was measured (LoD = 6.07 nM; K a = 1.0595 × 102 M-1). The non-toxic cytotoxicity and bioimaging in live zebrafish broadened the practical uses of PA@AuNPs. Furthermore, the surface interactions between PA@AuNPs and FTD were studied theoretically using time-dependent density functional theory (TD-DFT) at the B3LYP/6-31G(d,p) level of theory to support the findings from the experiment.

Excitation-independent and fluorescence-reversible N-GQD for picomolar detection of inhibitory neurotransmitter in milk samples ‒ an alleyway for possible neuromorphic computing application.

N‒GQDs with an average size of ca. 20-30 nm are utilized for the picomolar detection of inhibitory neurotransmitters, glycine (Gly), in pH ca. 7.0. The crystalline nature, morphology, elemental composition, and chemical state of N-GQDs are investigated by XRD, FE-SEM, HR-TEM, XPS, and FT-IR techniques. The addition of Gly (100 × 10-9 M; 0 â†’ 1.0 mL) steadily quenches the fluorescence intensity of N-GQD (1 × 10-6 M) at 432 nm (λex 333 nm) due to inner filter effect (IFE) through the formation of ground-state complex, N-GQD•Gly. The excitation-independent N‒GQDs showed an outstanding selectivity and sensitivity towards Gly with binding constant (Ka = 8.97 × 10-3 M-1) and LoD (21.04 pM; S/N = 3). Time-correlated single-photon counting experiment confirms the static quenching of N-GQD (8.77 â†’ 8.85 ns) in the presence of Gly. The interference of other amino acids on the strong binding of the N-GQD•Gly complex in H2O is examined. Combinatorial Ex-OR and NOT gate logic circuits that could be useful in neuromorphic computing are developed based on the reversible fluorescence intensity changes of N-GQD upon the addition of Gly (ФF 0.54 â†’ 0.39). The real-time application of N-GQD was investigated using commercially available relevant milk samples. Remarkably, not less than 99% cytotoxic reactivity of N-GQDs is attained against HeLa cells.

Macroparticles Reduction Using Filter Free Cathodic Vacuum Arc Deposition Method in ZnO Thin Films.

We report a new method to reduce macroparticles in ZnO thin films using filter free cathodic vacuum arc deposition without using any cooling arrangements operated at low arc current. The detailed mechanism has been proposed to reduce macroparticles during thin film deposition. The successful reduction of macroparticles was confirmed employing FESEM-EDX studies. FESEM images of ZnO thin films deposited with cathode spot to substrate distance from 10 to 20 cm revealed that the population of the macroparticles were reduced with the increase of cathode spot to substrate distances at low arc current. The prepared ZnO films were characterised and showed good structural and optical properties.

Enhanced super-hydrophobic and switching behavior of ZnO nanostructured surfaces prepared by simple solution--immersion successive ionic layer adsorption and reaction process.

A simple and cost-effective successive ionic layer adsorption and reaction (SILAR) method was adopted to fabricate hydrophobic ZnO nanostructured surfaces on transparent indium-tin oxide (ITO), glass and polyethylene terephthalate (PET) substrates. ZnO films deposited on different substrates show hierarchical structures like spindle, flower and spherical shape with diameters ranging from 30 to 300 nm. The photo-induced switching behaviors of ZnO film surfaces between hydrophobic and hydrophilic states were examined by water contact angle and X-ray photoelectron spectroscopy (XPS) analysis. ZnO nanostructured films had contact angles of ~140° and 160°±2 on glass and PET substrates, respectively, exhibiting hydrophobic behavior without any surface modification or treatment. Upon exposure to ultraviolet (UV) illumination, the films showed hydrophilic behavior (contact angle: 15°±2), which upon low thermal stimuli revert back to its original hydrophobic nature. Such reversible and repeatable switching behaviors were observed upon cyclical exposure to ultraviolet radiation. These biomimetic ZnO surfaces exhibit good anti-reflective properties with lower reflectance of 9% for PET substrates. Thus, the present work is significant in terms of its potential application in switching devices, solar coatings and self-cleaning smart windows.

Controlled Growth of WO(3) Nanostructures with Three Different Morphologies and Their Structural, Optical, and Photodecomposition Studies.

Tungsten trioxide (WO(3)) nanostructures were synthesized by hydrothermal method using sodium tungstate (Na(2)WO(4).2H(2)O) alone as starting material, and sodium tungstate in presence of ferrous ammonium sulfate [(NH(4))(2)Fe(SO(4))(2).6H(2)O] or cobalt chloride (CoCl(2).6H(2)O) as structure-directing agents. Orthorhombic WO(3) having a rectangular slab-like morphology was obtained when Na(2)WO(4).2H(2)O was used alone. When ferrous ammonium sulfate and cobalt chloride were added to sodium tungstate, hexagonal WO(3) nanowire clusters and hexagonal WO(3) nanorods were obtained, respectively. The crystal structure and orientation of the synthesized products were studied by X-ray diffraction (XRD), micro-Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM), and their chemical composition was analyzed by X-ray photoelectron spectroscopy (XPS). The optical properties of the synthesized products were verified by UV-Vis and photoluminescence studies. A photodegradation study on Procion Red MX 5B was also carried out, showing that the hexagonal WO(3) nanowire clusters had the highest photodegradation efficiency.

Energy minimization studies on alpha-turns.

Using a grid search technique, the entire conformational space of a system of four linked peptide units (tetrapeptide) was scanned to pick out geometrically possible 5-->1 type hydrogen-bonded conformations defined as an alpha-turn. The energy minimization of these conformations led to 23 distinct minimum energy conformations (MECs) falling in 13 different classes. The presence of beta and gamma turn type hydrogen bonds along with 5-->1 type hydrogen bond gave conformational variability in a given class. The occurrence of bifurcated hydrogen bonding network was a characteristic feature of most of the MECs. In many prototype MECs non-glycyl residues such as Ala and Pro could be accommodated. Comparison of MECs with the alpha-turn examples that are observed in proteins showed that the conformationally worked out MECs occurred in isolation in proteins, with the alpha-helical alpha-turn being distinctly the most predominant.

Motifs and conformational analysis of amino acid residues adjoining beta-turns in proteins.

Using a data set of 250 non-homologous high-resolution globular proteins, a systematic analysis of the conformations that precede and succeed (positions i and i + 3) the various classical beta-turn types has been carried out. The collective conformation of a specific beta-turn type, including the flanking positions, termed motif, has been studied. In all the four turn types, the majority of examples are preceded and succeeded by extended conformation. Some of the other observations are: (1) In a type I beta-turn, Gly at position i + 3 has a higher favorability to occur with positive phi and does not prefer the major motif beta-alpha R-alpha R-beta. (2) The left-handed alpha-helical conformation (alpha L) is not preferred at both the flanking positions for type I' and II' beta-turns. (3) The beta--beta motif is favourable for all the turn types and the motif beta--alpha L very highly favourable for type I.

Inhaled benzene increases the frequency and length of lacI deletion mutations in lung tissues of mice.

This study investigated the frequency and pattern of mutations that arose in lacI transgenes in lung tissues of mice exposed to 300 p.p.m. of benzene for 6 h/day x 5 days/week for 12 weeks. The nucleotide sequence changes in 86 lacI- transgenes from lung tissues of eight benzene-exposed mice (BEM) and 78 spontaneous lacI- transgenes from lung tissues of eight unexposed control mice (UCM) were identified and compared. A total of 31% (27/86) of the lacI mutations in BEM are deletions compared with 9% (7/78) deletions in UCM. In BEM, 44% (12/27) of the deletions were longer than 10 bp, whereas only 14% (1/7) of the deletions in UCM exceeded 10 bp in length. Statistical tests supported the hypothesis that benzene exposure resulted in significant increases in both the frequency and length of deletions. Based on the lacI mutant frequency and fraction of unique mutations, lung tissues of BEM were estimated to have a 1.8-fold increase in lacI mutation frequency compared with lung tissues of UCM. The results presented in this paper demonstrate that inhaled benzene is a gene mutagen in lung tissues of mice.