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Photoinactivation of the <b><i>Staphylococcus aureus</i></b> Lactose-Specific EIICB Phosphotransferase Component with <b><i>p</i></b>-azidophenyl-β-D-Galactoside and Phosphorylation of the Covalently Bound Substrate
摘要： Background: The phosphoenolpyruvate (PEP):lactose phosphotransferase system of Staphylococcus aureus transports and phosphorylates lactose and various phenylgalactosides. Their phosphorylation is catalyzed by the Cys476-phosphorylated EIIB domain of the lactose-specific permease enzyme IICB (EIICBLac). Phosphorylation causes the release of galactosides bound to the EIIC domain into the cytoplasm by a mechanism not yet understood. Results: Irradiation of a reaction mixture containing the photoactivatable p-azidophenyl-β-D-galactopyranoside and EIICBLac with UV light caused a loss of EIICBLac activity. Nevertheless, photoinactivated EIICBLac could still be phosphorylated with [32P] PEP. Proteolysis of photoinactivated [32P]P-EIICBLac with subtilisin provided an 11-kDa radioactive peptide. Only the sequence of its first three amino acids (-H-G-P-, position 245–247) could be determined. They are part of the substrate binding pocket in EIICs of the lactose/cellobiose PTS family. Surprisingly, while acid treatment caused hydrolysis of the phosphoryl group in active [32P]P EIICBLac, photoinactivated [32P]P-EIICBLac remained strongly phosphorylated. Conclusion: Phosphorylation of the –OH group at C6 of p-nitrenephenyl-β-D-galactopyranoside covalently bound to EIICLac by the histidyl-phosphorylated [32P]P EIIBLac domain is a likely explanation for the observed acid resistance. Placing p-nitrenephenyl-β-D-galactopyranoside into the active site of modelled EIICLac suggested that the nitrene binds to the -NH- group of Ser248, which would explain why no sequence data beyond Pro247could be obtained.
关键词： Staphylococcus aureus,Lactose transport,Photoinactivation,Phosphoenolpyruvate:carbohydrate phosphotransferase system,Azidophenyl-β-D-galactopyranoside
更新于2025-09-04 15:30:14
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Cu-Doped TiO2: Visible Light Assisted Photocatalytic Antimicrobial Activity
摘要： Surface contamination by microbes is a major public health concern. A damp environment is one of potential sources for microbe proliferation. Smart photocatalytic coatings on building surfaces using semiconductors like titania (TiO2) can effectively curb this growing threat. Metal-doped titania in anatase phase has been proven as a promising candidate for energy and environmental applications. In this present work, the antimicrobial efficacy of copper (Cu)-doped TiO2 (Cu-TiO2) was evaluated against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) under visible light irradiation. Doping of a minute fraction of Cu (0.5 mol %) in TiO2 was carried out via sol-gel technique. Cu-TiO2 further calcined at various temperatures (in the range of 500–700 ?C) to evaluate the thermal stability of TiO2 anatase phase. The physico-chemical properties of the samples were characterized through X-ray diffraction (XRD), Raman spectroscopy, X-ray photo-electron spectroscopy (XPS) and UV–visible spectroscopy techniques. XRD results revealed that the anatase phase of TiO2 was maintained well, up to 650 ?C, by the Cu dopant. UV–vis results suggested that the visible light absorption property of Cu-TiO2 was enhanced and the band gap is reduced to 2.8 eV. Density functional theory (DFT) studies emphasize the introduction of Cu+ and Cu2+ ions by replacing Ti4+ ions in the TiO2 lattice, creating oxygen vacancies. These further promoted the photocatalytic efficiency. A significantly high bacterial inactivation (99.9999%) was attained in 30 min of visible light irradiation by Cu-TiO2.
关键词： Staphylococcus aureus,phase transition,antibacterial coatings,photocatalysis,doping,Cu-doped TiO2,Escherichia coli
更新于2025-09-04 15:30:14
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Acute subretinal abscess in <i>Staphylococcus aureus</i> septicaemia with endophthalmitis showcased by multimodal retinal imaging and with 2-year follow-up
摘要： A middle-aged man presented to emergency services with central vision loss in the setting of flu-like illness with fever. A striking subfoveal abscess was observed in the right fundus. Focal acute chorioretinal inflammation was noted in the asymptomatic fellow eye. Staphylococcus aureus septicaemia was subsequently diagnosed. He presented with undiagnosed HIV infection and latent syphilis. Serial high-definition multimodal retinal imaging showcased resolution of the dome-shaped subretinal abscess following treatment with intravenous flucloxacillin. A chorioretinal scar swiftly replaced the subfoveal abscess. Peripheral right vision and full left vision was retained. Vision loss due to endogenous endophthalmitis in systemic sepsis is an emergency requiring prompt multidisciplinary care. Sight and life are at risk—thus this is not a diagnosis to miss! Early recognition is paramount to health and in retaining vision. We briefly review relevant literature and portray how multimodal imaging guided response to treatment of acute subretinal abscess.
关键词： endophthalmitis,Staphylococcus aureus septicaemia,multimodal retinal imaging,HIV infection,acute subretinal abscess,latent syphilis
更新于2025-09-04 15:30:14