Staphylococcus aureus is a widely acknowledged Gram-positive pathogen for forming biofilm and virulence gene expressions by quorum sensing (QS), a cell to cell communication process. The quorum regulator SarA of S. aureus up regulates the expression of many virulence factors including biofilm formation to mediate pathogenesis and evasion of the host immune system in the late phases of growth. Thus, inhibiting the production or blocking SarA protein might influence the down regulation of biofilm and virulence factors. In this context, here we have synthesized 2-[(Methylamino)methyl]phenol, which was specifically targeted towards the quorum regulator SarA through in silico approach in our previous study. The molecule has been evaluated in vitro to validate its antibiofilm activity against clinical S. aureus strains. In addition, antivirulent properties of the inhibitor were confirmed with the observation of a significant reduction in the expression of representative virulence genes like fnbA, hla and hld that are governed under S. aureus quorum sensing. Interestingly, the SarA targeted inhibitor showed negligible antimicrobial activity and markedly reduced the minimum inhibitory concentration of conventional antibiotics when used in combination making it a more attractive lead for further clinical tests.

Lipid vesicles are used as the organizational structure of self-assembled light-harvesting systems. Following analysis of 17 chromophores, six were selected for inclusion in vesicle-based antennas. The complementary absorption features of the chromophores span the near-ultraviolet, visible, and near-infrared region. Although the overall concentration of the pigments is low (∼1 μM for quantitative spectroscopic studies) in a cuvette, the lipid-vesicle system affords high concentration (≥10 mM) in the bilayer for efficient energy flow from donor to acceptor. Energy transfer was characterized in 13 representative binary mixtures using static techniques (fluorescence–excitation versus absorptance spectra, quenching of donor fluorescence, modeling emission spectra of a mixture versus components) and time-resolved spectroscopy (fluorescence, ultrafast absorption). Binary donor–acceptor systems that employ a boron-dipyrrin donor (S₀ ↔ S₁ absorption/emission in the blue-green) and a chlorin or bacteriochlorin acceptor (S₀ ↔ S₁ absorption/emission in the red or near-infrared) have an average excitation-energy-transfer efficiency (Φ_EET) of ∼50%. Binary systems with a chlorin donor and a chlorin or bacteriochlorin acceptor have Φ_EET ∼ 85%. The differences in Φ_EET generally track the donor-fluorescence/acceptor-absorption spectral overlap within a dipole–dipole coupling (Förster) mechanism. Substantial deviation from single-exponential decay of the excited donor (due to the dispersion of donor–acceptor distances) is expected and observed. The time profiles and resulting Φ_EET are modeled on the basis of (Förster) energy transfer between chromophores relatively densely packed in a two-dimensional compartment. Initial studies of two ternary and one quaternary combination of chromophores show the enhanced spectral coverage and energy-transfer efficacy expected on the basis of the binary systems. Collectively, this approach may provide one of the simplest designs for self-assembled light-harvesting systems that afford broad solar collection and efficient energy transfer.