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   Lu, Hua (Ed.)

   SPLUNC1 (short palate lung and nasal epithelial clone 1) is a multifunctional host defense protein found in human respiratory tract with antimicrobial properties. In this work we compare the biological activities of four SPLUNC1 antimicrobial peptide (AMP) derivatives using paired clinical isolates of the Gram-negative (G(-)) bacteria Klebsiella pneumoniae, obtained from eleven patients with/without colistin resistance. Secondary structural studies were carried out to study interactions between the AMPs and lipid model membranes (LMMs) utilizing circular dichroism (CD). Two peptides were further characterized using x-ray diffuse scattering (XDS) and neutron reflectivity (NR). A4-153 displayed superior antibacterial activity in both G(-) planktonic cultures and biofilms. NR and XDS revealed that A4-153 (highest activity) is located primarily in membrane headgroups, while A4-198 (lowest activity) is located in hydrophobic region. CD revealed that A4-153 is helical while A4-198 has little helical character, demonstrating that helicity and efficacy are correlated in these SPLUNC1 AMPs. 

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2. Carbon–TiO2 Hybrid Quantum Dots for Photocatalytic Inactivation of Gram-Positive and Gram-Negative Bacteria

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   Carbon–semiconductor hybrid quantum dots are classical carbon dots with core carbon nanoparticles doped with a selected nanoscale semiconductor. Specifically, on those with the nanoscale TiO2 doping, denoted as CTiO2-Dots, their synthesis and thorough characterization were reported previously. In this work, the CTiO2-Dots were evaluated for their visible light-activated antibacterial function, with the results showing the effective killing of not only Gram-positive but also the generally more resistant Gram-negative bacteria. The hybrid dots are clearly more potent antibacterial agents than their neat carbon dot counterparts. Mechanistically, the higher antibacterial performance of the CTiO2-Dots is attributed to their superior photoexcited state properties, which are reflected by the observed much brighter fluorescence emissions. Also considered and discussed is the possibility of additional contributions to the antibacterial activities due to the photosensitization of the nanoscale TiO2 by its doped core carbon nanoparticles. 

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