Luminescence behavior of inorganic and metalorganic europium(III) dopants incorporated into silica and epoxy-diol ORMOSIL sol-gel hosts

The narrow, intense emission bands of europium (III) make its compounds of interest for various optical source applications. Previous studies have indicated that complexes like tris(4,4,4-trifluoro-1-(2-thieny1)-1,3-butanedionato-O,O)europium(III), Eu(ttfa)₃, have superior fluorescence properties in select media with respect to comparable inorganic salts like EuCl₃. It has been shown that such complexes are readily incorporated into solid-state matrices via the sol-gel process. The present research examines the luminescence behavior of Eu(ttfa)₃ and EuCl₃ doped into a sol-gel-derived epoxy-diol ORMOSIL host, and extends our earlier work involving doped silica and acrylate ORMOSIL gel materials. The present study focuses on the effects of dopant-matrix interactions and seeks to compare the emission behavior of Eu(ttfa)₃ and EuCl₃ in silica and epoxy-diol ORMOSIL gel host materials.     

Probing Selectivity and Creating Structural Diversity Through Hybrid Polyketide Synthases

Engineering polyketide synthases (PKS) to produce new metabolites requires an understanding of catalytic points of failure during substrate processing. Growing evidence indicates the thioesterase (TE) domain as a significant bottleneck within engineered PKS systems. We created a series of hybrid PKS modules bearing exchanged TE domains from heterologous pathways and challenged them with both native and non‐native polyketide substrates. Reactions pairing wildtype PKS modules with non‐native substrates primarily resulted in poor conversions to anticipated macrolactones. Likewise, product formation with native substrates and hybrid PKS modules bearing non‐cognate TE domains was severely reduced. In contrast, non‐native substrates were converted by most hybrid modules containing a substrate compatible TE, directly implicating this domain as the major catalytic gatekeeper and highlighting its value as a target for protein engineering to improve analog production in PKS pathways.     

Insensitivity of sub-Kelvin electron-phonon coupling to substrate properties

We have examined the role of the substrate on electron-phonon coupling in normal-metal films of Mn-doped Al at temperatures below 1 K. Normal metal-insulator-superconductor junctions were used to measure the electron temperature in the films as a function of Joule heating power and phonon temperature. Theory suggests that the distribution of phonons available for interaction with electrons in metal films may depend on the acoustic properties of the substrate, namely, that the electron-phonon coupling constant Σ would be larger on the substrate with smaller sound speed. In contrast, our results indicate that within experimental error (typically ±10%), Σ is unchanged among the two acoustically distinct substrates used in our investigation.     

LDL-based nanoparticles for contrast enhanced MRI of atheroplaques in mouse models

A LDL particle functionalized with a GdDO3A-monoamide chelate with a long alkenyl anchor (GdDO3A-OA) was prepared for in vivo detection of atheroplaques. The GdDO3A-OA, when successfully intercalated into the lipid layer of LDL particles, led to a significant enhancement of magnetic resonance imaging signal intensity of atheroplaques in atherosclerosis mouse models.     

Alternative spiroketalization methods toward purpuromycin: a diketone approach to prevent benzofuran formation

The central portion of purpuromycin has been assembled via a classical spiroketalization reaction. Key to promoting this reaction mode versus benzofuran formation was the oxidation state of the spiroketal core. With a higher oxidation state, even the electron-deficient isocoumarin found in purpuromycin could be employed directly in the spiroketalization. The two halves of the spiroketalization precursor were joined via a nitrile oxide/styrene 1,3-dipolar cycloaddition. A very mild selenium dioxide oxidation was used to introduce the required oxidation state of the spiroketal core.