Two-Photon Absorption in Fluorescent Protein Chromophores: TDDFT and CC2 Results

Two-photon spectroscopy of fluorescent proteins is a powerful bioimaging tool. Considerable effort has been made to measure absolute two-photon absorption (TPA) for the available fluorescent proteins. Being a technically involved procedure, there is significant variation in the published experimental measurements even for the same protein. In this work, we present a time-dependent density functional theory (TDDFT) study on isolated chromophores comparing the ability of four functionals (PBE0, B3LYP, CAM-B3LYP, and LC-BLYP) combined with the 6-31+G­(d,p) basis set to reproduce averaged experimental TPA energies and cross sections. The TDDFT energies and TPA cross sections are also compared to corresponding CC2/6-31+G­(d,p) results for excitation to S₁ for the five smallest chromophores. In general, the computed TPA energies are less functional dependent than the TPA cross sections. The variation between functionals is more pronounced when higher-energy transitions are studied. Changes to the conformation of a chromophore are shown to change the TPA cross-section considerably. This adds to the difficulty of comparing an isolated chromophore to the one embedded in the protein environment. All functionals considered give moderate agreement with the corresponding CC2 results; in general, the TPA cross sections determined by TDDFT are 1.5–10 times smaller than the corresponding CC2 values for excitation to S₁. LC-BLYP and CAM-B3LYP give erroneously large TPA cross sections in the higher-energy regions. On the other hand, B3LYP and PBE0 yield values that are of the same order of magnitude and in some cases very close to the averaged experimental data. Thus, based on the results reported here, B3LYP and PBE0 are the preferred functionals for screening chromphores for TPA. However, at best, TDDFT can be used to semiquantitatively scan chromophores for potential TPA probes and highlight spectroscopic peaks that could be present in the mature protein

The synergistic effect of biosynthesized silver nanoparticles from a combined extract of parsley, corn silk, and gum arabic: in vivo antioxidant, anti-inflammatory and antimicrobial activities

Microbial resistance, oxidative stress, and inflammatory conditions are among the leading causes of death worldwide. In the current work, silver nanoparticles (AgNPs) were biosynthesized using the aqueous extracts of parsley, corn silk (CS), gum Arabic (GA) or combination of the three extracts. The formed nanoparticles were characterized using three techniques including transmission electron microscopy (TEM), UV-visible spectrophotometer and Fourier-transform infrared spectroscopy (FTIR). The antioxidant, anti-inflammatory, and antimicrobial activities were tested for the formed nanoparticles, the aqueous extracts of each of the three plants and their combination. Oxidative stress was induced by alloxan which promoted the development of diabetes mellitus in rats. Inflammation was induced by injecting carrageenan in rats’ paws. Pathogenic microorganisms causing serious urinary tract infection (UTI) were selected for the antimicrobial assay. All aqueous extracts and the biosynthesized AgNPs showed variable degrees of antioxidant, anti-inflammatory and antimicrobial activities, however, the AgNPs biosynthesized by the combination of the three aqueous extracts was the most effective one. LC/MS was done to identify the compounds present in the crude extracts that may be responsible for the observed biological activities. LC/MS resulted in the identification of 13 compounds. Docking experiments on COX-1 (cyclooxygenase-1) and COX-2 (cyclooxygenase-2) were performed to determine the compounds responsible for the anti-inflammatory activity of the extracts. The results showed that silver nanoparticles synthesized by the combination of the three aqueous extracts are considered promising candidates for the development of antioxidant, anti-inflammatory and antimicrobial agents

Anti-Alzheimer potential, metabolomic profiling and molecular docking of green synthesized silver nanoparticles of Lampranthus coccineus and Malephora lutea aqueous extracts

The green synthesis of silver nanoparticles (SNPs) using plant extracts is an eco-friendly method. It is a single step and offers several advantages such as time reducing, cost-effective and environmental non-toxic. Silver nanoparticles are a type of Noble metal nanoparticles and it has tremendous applications in the field of diagnostics, therapeutics, antimicrobial activity, anticancer and neurodegenerative diseases. In the present work, the aqueous extracts of aerial parts of Lampranthus coccineus and Malephora lutea F. Aizoaceae were successfully used for the synthesis of silver nanoparticles. The formation of silver nanoparticles was early detected by a color change from pale yellow to reddish-brown color and was further confirmed by transmission electron microscope (TEM), UV–visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), X-ray diffraction (XRD), and energy-dispersive X-ray diffraction (EDX). The TEM analysis of showed spherical nanoparticles with a mean size between 12.86 nm and 28.19 nm and the UV- visible spectroscopy showed λ$_{max}$ of 417 nm, which confirms the presence of nanoparticles. The neuroprotective potential of SNPs was evaluated by assessing the antioxidant and cholinesterase inhibitory activity. Metabolomic profiling was performed on methanolic extracts of L. coccineus and M. lutea and resulted in the identification of 12 compounds, then docking was performed to investigate the possible interaction between the identified compounds and human acetylcholinesterase, butyrylcholinesterase, and glutathione transferase receptor, which are associated with the progress of Alzheimer’s disease. Overall our SNPs highlighted its promising potential in terms of anticholinesterase and antioxidant activity as plant-based anti-Alzheimer drug and against oxidative stress