[en] We report the first characterization of the in vivo porphyrin scavenging abilities of two components of a newly discovered heme scavenging system involving iron-regulated surface determinant (Isd) proteins. These proteins are present within the cell envelope of the Gram-positive human pathogen Staphylococcus aureus. IsdC and IsdE, when expressed heterologously in Escherichia coli, efficiently scavenged intracellular heme and resulted in de novo heme synthesis in excess of 100-fold above background. Magnetic circular dichroism analyses showed that the heme-binding properties of the two proteins differ significantly from one another. IsdC bound almost exclusively free-base protoporphyrin IX, whereas the IsdE protein was associated with low spin Fe(III) and Fe(II) heme. These properties provide important insight into the possible mechanisms of iron scavenging from bound heme by Isd proteins

[en] The synthesis of 4-bis(4-aminophenoxy)phenoxy derivatized phthalocyanine containing In (complex 2), and Ga (complex 3), and the previously reported complex 4 (containing Zn) and their covalent attachment to glutathione (GSH) functionalized cadmium telluride quantum dots (CdTe QDs) are reported in this work. Additionally, their photophysical, energy transfer and nonlinear optical properties were investigated. The covalently linked derivatives showed lower fluorescence quantum yields with corresponding higher triplet quantum yields. Quenching of the photoluminescence intensity of the CdTe QDs was observed to be due to energy transfer from the QDs to phthalocyanine (Pcs) molecules. The reverse saturable absorption nonlinear optical response was found to be predominantly dependent on the excited state absorption. The observed limiting threshold ranges from 0.04 to 0.62 J/cm⁻².

[en] Three different phthalocyanine complexes substituted with carbazoles were conjugated to graphene quantum dots (GQDs) through π–π stacking. The morphologies, sizes, and crystallinities of the nanoconjugates were determined using Raman spectroscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray diffraction. The nonlinear optical (NLO) properties of the metallophthalocyanines alone and when conjugated to the GQD nanomaterial in different solvents, as well as after having been embedded in thin films, were studied. The effects of the different substituents and solvents on the NLO properties of the metallophthalocyanines were evaluated. Enhancements in the photophysical properties of the complexes upon conjugation with the nanomaterial were observed. Fluorescence quantum yields, fluorescence lifetimes, triplet quantum yields, and triplet lifetimes were measured for the complexes, and for their conjugates in DMSO.