This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

No abstract

Green synthesis of silver nanoparticles (AgNPs) is gaining momentum in the field of nano-research. Scoparia dulcis leaves were used as a reducing agent for the synthesis of silver nanoparticles from an aqueous solution of silver nitrate (AgNO 3 ). Synthesized AgNPs were characterized by UV-Vis spectroscopy, XRD, SEM with EDAX and TEM. UV-VIS surface plasmon resonance spectroscopy was observed at 430 nm. XRD data depicts that the NPs are crystalline in nature. The EDAX data indicate that 63.76% presence of Ag metal. The TEM & SEM results indicate that size of the AgNPs ranges from 15-25 nm. The results also support that spherical shape of the nanoparticles. In addition, the NPs are in polydispersed condition. The antimicrobial activities indicate significant inhibition of the growth of three pathogenic bacteria such as Pseudomonas ariginosa, Bacillua subtillis and Staphylococcus aureous. Cytotoxicity of this nanoparticle showed that this Ag-NP also has more cytotoxic effect on a lung cancer cell line, A549 cells compared to ovarian cancer cell line, PA1 indicating a possible therapeutic use of this AgNP.

Here we report on the excited-state behavior in terms of the excited-state proton-transfer (ESPT) reaction as well as the ground-state acid-base property of pyranine [8-hydroxypyrene-1,3,6-trisulfonate (HPTS)] in the presence of an enzymatic protein, human lysozyme (LYZ). HPTS forms a 1:1 ground-state complex with LYZ having the binding constant KBH = (1.4 ± 0.05) × 10(4) M(-1), and its acid-base equilibrium gets shifted toward the deprotonated conjugate base (RO(-)), resulting in a downward shift in pKa. This suggests that the conjugate base (RO(-)) is thermodynamically more favored over the protonated (ROH) species inside the lysozyme matrix, resulting in an increased population of the deprotonated form. However, for the release of the proton from the excited photoacid, interestingly, the rate of proton transfer gets slowed down due to the "slow" acceptor biological water molecules present in the immediate vicinity of the fluorophore binding region inside the protein. The observed ESPT time constants, ∼140 and ∼750 ps, of protein-bound pyranine are slower than in bulk aqueous media (∼100 ps, single exponential). The molecular docking study predicts that the most probable binding location of the fluorophore is in a region near to the active site of the protein. Here we also report on the effect of external electrolyte (NaCl) on the reverse modulation of ground-state prototropy as well as the ESPT process of the protein-bound pyranine. It is found that there is a dominant role of electrostatic forces in the HPTS-LYZ interaction process, because an increase in ionic strength by the addition of NaCl dislodges the fluorophore from the protein pocket to the bulk again. The study shows a considerably different perspective of the perturbation offered by the model macromolecular host used, unlike the available literature reports on the concerned photoacid.