Molecular inorganic clusters, which are stable under ambient conditions, can be used as convenient single-source precursors for controlled preparation of 2-9-nm CdSe and CdSe/ ZnS nanocrystals and 2-5-nm nanocrystals of ZnSe. The use of a cluster-based single-source precursor allows nanomaterial growth to be initiated at low temperature without the pyrolytic step for nucleus formation traditionally required for lyothermal growth processes. The elimination of the pyrolytic step allows greater synthetic control, slow thermodynamic growth at lower temperatures, high crystallinity, and reaction scalability (>50 g/L) while maintaining size dispersity at ∼5%.
Prenylation of natural compounds adds structural diversity, alters biological activity, and enhances therapeutic potential. Because prenylated compounds often have a low natural abundance, alternative production methods are needed. Metabolic engineering enables natural product biosynthesis from inexpensive biomass, but is limited by the complexity of secondary metabolite pathways, intermediate and product toxicities, and substrate accessibility. Alternatively, enzyme catalyzed prenyl transfer provides excellent regio- and stereo-specificity, but requires expensive isoprenyl pyrophosphate substrates. Here we develop a flexible cell-free enzymatic prenylating system that generates isoprenyl pyrophosphate substrates from glucose to prenylate an array of natural products. The system provides an efficient route to cannabinoid precursors cannabigerolic acid (CBGA) and cannabigerovarinic acid (CBGVA) at >1 g/L, and a single enzymatic step converts the precursors into cannabidiolic acid (CBDA) and cannabidivarinic acid (CBDVA). Cell-free methods may provide a powerful alternative to metabolic engineering for chemicals that are hard to produce in living organisms.
The dimeric, pentacopper(II)-substituted tungstosilicate [Cu(5)(OH)(4)(H(2)O)(2)(A-alpha-SiW(9)O(33))(2)](10)(-) (1) has been characterized by single-crystal X-ray diffraction, elemental analysis, IR, electrochemistry, magnetic measurements, electron paramagnetic resonance (EPR), and mass spectrometry (MS). Magnetization and high-field EPR measurements reveal that the pentameric copper core {Cu(5)(OH)(4)(H(2)O)(2)}(6+) of 1 exhibits strong antiferromagnetic interactions (J(a) = -51 +/- 6 cm(-)(1), J(b) = -104 +/- 1 cm(-)(1), and J(c) = -55 +/- 3 cm(-)(1)) resulting in a spin S(T) = (1)/(2) ground state. EPR data show that the unpaired electron spin density is localized on the spin-frustrated apical Cu(2+) ion with g(zz) = 2.4073 +/- 0.0005, g(yy) = 2.0672 +/- 0.0005, g(xx) = 2.0240 +/- 0.0005, and A(zz) = -340 +/- 20 MHz (-0.0113 cm(-)(1)). 1 can therefore be considered as a model system for a five-spin, electronically coupled, spin-frustrated system. Polyanion 1, which is stable over a wide pH domain (pH 1-7), was characterized by cyclic voltammetry (CV) in a pH 5 medium. Its CV was constituted by an initial two-step reduction of the Cu(2+) centers to Cu(0) through Cu(+), followed at more negative potential by the redox processes of the W centers. Controlled potential coulometry of 1 allows for the reduction of the five Cu(2+) centers, as seen by consumption of 10.05 +/- 0.05 electrons per molecule. Polyanion 1 triggers efficiently the electrocatalytic reduction of nitrate and nitrite, and it also catalyzes the reduction of N(2)O. To our knowledge, this is the first example of N(2)O catalytic reduction by a polyoxoanion. Fourier transform ion cyclotron resonance MS was used to unambiguously assign the molecular weight of the solution-phase species 1 and the oxidation states of the Cu atoms in the central {Cu(5)(OH)(4)(H(2)O)(2)}(6+) core. Infrared (IR) multiphoton dissociation MS/MS of 1 showed evidence of a condensation process similar to bronze formation at low irradiation intensity. Higher IR intensity resulted in the formation of stable fragments consistent with those previously observed in the solution chemistry of polyoxoanions.
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