Synthesis and fluorescence quenching mechanism of novel naphthalimide derivative by nanographene oxide

Peptides with Charged Amino Acids Mitigate nZnO-Induced Growth Inhibition of Lactobacillus rhamnosus LRa05

Growing concern is about the potential side effects of nanomaterials from food packaging, notably zinc oxide nanoparticles (nZnO). Previous research revealed that walnut-derived peptides could mitigate this inhibitory effect, but the mechanism involved is unclear. Here, we found that not all peptides have such an effect. Based on the growth inhibition model of Lactobacillus rhamnosus LRa05 induced by nZnO, we assessed the protective effects of various peptides. Notably, four peptides containing charged amino acids (PPKNW, WPPKN, ADIYTE, and WEREEQE) were found to effectively alleviate the growth inhibition phenomenon. We hypothesize that the peptide-nZnO interaction modifies this effect, as confirmed through infrared, Raman, and fluorescence spectroscopy. Our results highlight amide bonds, amino groups, carboxyl groups, and benzene rings as key peptide binding sites on nZnO, with static quenching primarily due to hydrogen bonds and van der Waals forces. This study elucidates peptide characteristics in nZnO interactions, facilitating a deeper exploration of food matrix-nanocomposite interactions.

Synthesis, Solvatochromism and Fluorescence Quenching Studies of Naphthalene Diimide Dye by Nano graphene oxide

A naphthalene diimide dye with two side amine arm was prepared. Uv-Vis and fluorescence spectroscopic techniques are used for their photophysical and solvatochromic characteristics in different solvents. The Lippert-Mataga plot for naphthalene diimide demonstrated a negative linear dependence by increasing polarity. Results showed naphthalene diimide is more polar in the ground than in the excited state. A quenching study was conducted for interacting the naphthalene diimide as a fluorophore and graphene oxide as a quencher. Fluorescence quenching-based platforms in nanoscale have been used in sensing systems. Raman, FTIR, Uv-Vis and fluorescence spectroscopic techniques were used to study the quenching mechanism. The results indicated that graphene plays an effective quencher against the naphthalene diimide, with a quenching efficiency 91%. The Stern-Volmer analysis results show a mix of static and dynamic quenching mechanisms. The binding constant of the quencher-fluorophore and the number of binding sites have been reported. Thermodynamic parameters of their interaction were evaluated. The negative values of the Gibbs free energy confirm that the complexation process is spontaneous. Meanwhile, the positive entropy value confirms that the favorable pathway process.

A pipeline to evaluate the discrepant interactions between typical nitrogenous disinfection byproduct haloacetonitriles and human hemoglobin

To evaluate the interaction between haloacetonitriles (HANs) and human hemoglobin (Hb), a pipeline was established based on fluorescence spectra, mass spectra and molecular docking. Fluorescence spectra analysis showed the fluorescence of Hb was statically quenched by HANs in the sequence of TCAN > DBAN > DCAN > IAN > BAN > CAN. HANs could combine to multiple surface sites of Hb accounting for "hydrogen bonds" and "van der Waals forces". The high-resolution mass spectra analysis for Hb with and without HANs further confirmed the formation of multiple HAN-Hb complexes with different conversion rates. With the assistance of MOE molecule docking, the potential combination sites and related interactions parameters between HANs and Hb were filtrated. By analyzing the correlations between the candidate interactions parameters and fluorescence quenching constants/MS conversion rates, the combination sites of HANs were fixed at Asp₁₂₆ (α₁/α₂), Lys₁₂₇ (α₁/α₂) in the form of "hydrogen bonds" X → Asp₁₂₆ (α₁/α₂), N → Lys₁₂₇ (α₁/α₂). In this way, the potential interactions between HANs and Hb were effectively evaluated.

A graphene oxide-based covalent resorufin-conjugated fluorescence "off-on" probe for detection of hydrazine

The unique properties of graphene oxide (GO), such as good water solubility, non-toxicity, biocompatibility and cell permeability, make GO well suited for a number of biological applications. In this study, we explore the application of GO as an efficient fluorescent quencher for a highly fluorescent organic dye, resorufin (RF). The quenching effect of GO on resorufin is studied by noncovalent and covalent bonding of resorufin, respectively. The fluorescence is completely quenched when resorufin is covalently linked to GO; while resorufin's fluorescence could be still observed through noncovalent bonding to GO sheet. Interestingly, addition of hydrazine into RF-GO complex causes the fluorescence recovered, providing a potential ''OFF-ON'' fluorescence responsive probe for detecting hydrazine in vitro and in living cells.