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.
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%.
In the original version of this Article, the genotype of the M30 mutant presented in Fig. 3b was given incorrectly as Y288V/A232S, and the M31 mutant was given incorrectly as M1/A232S. The correct ...genotype of the M30 mutant is Y288A/A232S and for M31 it is Y288V/A232S. In addition, to keep consistency in genotype formatting, the genotype of the M27 mutant should be Y288V/G286S. The errors have been corrected in both the PDF and HTML versions of the Article.
The demonstration and control of biofunction between inorganic nanomaterials and biological scaffolding is crucial to the development of the field of biomaterials. Although unique hierarchical ...structures can be generated, the impact of nanosized materials on the biological activity of DNA−protein interactions is relatively unknow. Using highly selective proteins that induce sequence-specific conformational perturbations within DNA, we demonstrate the absolute maintenance of biofunction for biomaterials composed of duplex DNA appended with 1.4-nm Au particles. Enzyme activity and DNA binding affinities (K d) are unaltered by the nanoparticle−DNA conjugates. Our results provide a foundation for interfacing more complex and diverse protein−DNA-systems.
We present a methodology for mass and size dispersity analysis by MALDI-TOF mass spectrometry of lyothermally grown 2.5−3.7 nm ZnS nanocrystals having a Zn blende crystal structure. These results ...correlate with information obtained by TEM and absorption spectroscopy. The use of MS methods to probe size and size dispersity provides a convenient method to rapidly analyze II−VI materials at the nanoscale. We believe these results represent the first mass spectrometric analysis of size and size dispersities on II−VI nanocrystals.
The dimeric, pentacopper(II)-substituted tungstosilicate Cu5(OH)4(H2O)2(A-α-SiW9O33)210- (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 {Cu5(OH)4(H2O)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 Cu2+ 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 Cu2+ centers to Cu0 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 Cu2+ 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 N2O. To our knowledge, this is the first example of N2O 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 {Cu5(OH)4(H2O)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.
The trimeric, cyclic dimethyltin-containing tungstophophate {(Sn(CH3)2)(Sn(CH3)2O)(A-PW9O34)}3 (1) has been synthesized in aqueous acidic medium and characterized by IR, elemental analysis, ...electrochemistry, and FT-ICR MS. Single-crystal X-ray analysis was carried out on Cs12Na9{(Sn(CH3)2)(Sn(CH3)2O)(A-PW9O34)}3*20H2O (1a), which crystallizes in the trigonal system, space group R3, with a = b = 29.7445(7) A, c = 15.5915(7) A and Z = 3. Polyanion 1 is composed of three trilacunary (A-PW9O34) Keggin fragments that are linked on one side via three isolated dimethyltin groups and on the other side by a (Sn3(CH3)6O3) unit and three cesium ions, resulting in a cyclic assembly with C 3v symmetry. The discrete molecular, hybrid organic-inorganic 1 was synthesized by reaction of (CH3)2SnCl2 with Na9A-PW9O34 in 0.5 M sodium acetate buffer (pH 4.8). Comparison of several characteristics of the cyclic voltammograms of 1 and (A-PW9O34), including the potential location of their reduction peaks, the difference in their current intensities and their qualitative relative electron transfer speeds, supports the conclusion that the solid-state structure of 1 is retained in solution. The presence of (PW9O34)-based species in solutions of 1 was also confirmed by FT-ICR mass spectrometry.
A titanium oxide molecular cluster prepared by hydrolysis of titanium tetraethoxide in the presence of methacrylic acid, can be characterized by electrospray time of flight mass spectrometry ...(ESMS-TOF). The chemistry of such systems is not well known and ESMS is a powerful technique for studying the reactions of clusters in solution. The fingerprint of the cluster fragmentation suggests formation of Ti^sub x^O^sub y^ core fragments that represent commonly observed structural constructs in bulk titanium oxide metallates. The fragmentation steps provide insight into the hydrolytic conversion of this molecular sol gel intermediate into bulk TiO^sub 2^. While MS has been applied to the study of metal alkoxide hydrolysis mechanisms, mass spectra of isolated individual titanium oxide clusters have not previously been reported.
The trimeric, cyclic dimethyltin-containing tungstophophate {(Sn(CH3)2)(Sn(CH3)2O)(A-PW9O34)}321− (1) has been synthesized in aqueous acidic medium and characterized by IR, elemental analysis, ...electrochemistry, and FT-ICR MS. Single-crystal X-ray analysis was carried out on Cs12Na9{(Sn(CH3)2)(Sn(CH3)2O)(A-PW9O34)}3·20H2O (1a), which crystallizes in the trigonal system, space group R3, with a = b = 29.7445(7) Å, c = 15.5915(7) Å and Z = 3. Polyanion 1 is composed of three trilacunary (A-PW9O34) Keggin fragments that are linked on one side via three isolated dimethyltin groups and on the other side by a (Sn3(CH3)6O3) unit and three cesium ions, resulting in a cyclic assembly with C3vsymmetry. The discrete molecular, hybrid organic–inorganic 1 was synthesized by reaction of (CH3)2SnCl2 with Na9A-PW9O34 in 0.5 M sodium acetate buffer (pH 4.8). Comparison of several characteristics of the cyclic voltammograms of 1 and (A-PW9O34)9−, including the potential location of their reduction peaks, the difference in their current intensities and their qualitative relative electron transfer speeds, supports the conclusion that the solid-state structure of 1 is retained in solution. The presence of (PW9O34)-based species in solutions of 1 was also confirmed by FT-ICR mass spectrometry.
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