Discovery of a natural cyan blue: A unique food-sourced anthocyanin could replace synthetic brilliant blue.

The color of food is critical to the food and beverage industries, as it influences many properties beyond eye-pleasing visuals including flavor, safety, and nutritional value. Blue is one of the rarest colors in nature's food palette-especially a cyan blue-giving scientists few sources for natural blue food colorants. Finding a natural cyan blue dye equivalent to FD&C Blue No. 1 remains an industry-wide challenge and the subject of several research programs worldwide. Computational simulations and large-array spectroscopic techniques were used to determine the 3D chemical structure, color expression, and stability of this previously uncharacterized cyan blue anthocyanin-based colorant. Synthetic biology and computational protein design tools were leveraged to develop an enzymatic transformation of red cabbage anthocyanins into the desired anthocyanin. More broadly, this research demonstrates the power of a multidisciplinary strategy to solve a long-standing challenge in the food industry.

Crystal structure of dicaesium strontium hexa-cyanidoferrate(II), Cs2Sr[Fe(CN)6], from laboratory X-ray powder data.

Ferrocyanides with general formula A I xB II y [Fe(CN)6], where A and B are cations, are thought to accept many substitutions on the A and B positions. In this communication, the synthesis and crystal structure of Cs2Sr[Fe(CN)6] are reported. The latter was obtained from K2Ba[Fe(CN)6] particles, put in contact with caesium and strontium ions. Hence, a simultaneous ion-exchange mechanism (Cs for K, Sr for Ba) occurs to yield Cs2Sr[Fe(CN)6]. The synthesis protocol shows that K2BaFe(CN)6 particles can be used for the simultaneous trapping of radioactive caesium and strontium nuclides in water streams. Cs2Sr[Fe(CN)6] adopts the cryolite structure type and is isotypic with the known compound Cs2Na[Mn(CN)6] [dicaesium sodium hexa-cyanidomanganate(III)]. The octa-hedrally coordinated Sr and Fe sites both are located on inversion centres, and the eightfold-coordinated Cs site on a general position.

The influence of acylation, metal binding and natural antioxidants on the thermal stability of red cabbage anthocyanins in neutral solution.

The main red cabbage anthocyanins (pigments) are cyanidin glycosides bearing one or two acyl groups derived from hydroxycinnamic acids (HCAs). Through π-stacking interactions with the cyanidin chromophore, the HCA residues have a deep influence on the color expressed and its stability. In this work, a series of non-, mono- and diacylated anthocyanins were investigated in neutral solution (pH 7 and 8), where the pigments exhibit purple to blue colors. Under such conditions, the gradual color loss observed is a combination of two distinct processes involving the cyanidin nucleus: reversible water addition and irreversible autoxidation. By acidification to pH < 2, the colorless forms stemming from water addition (hemiketal and chalcones) are converted to the red flavylium ion, thereby permitting the selective monitoring of the irreversible contribution. The kinetics of color loss and of true pigment degradation could thus be recorded for each pigment. The influence of iron - cyanidin binding and of antioxidants (caffeic acid, N-acetylcysteine) was also investigated. A complete kinetic analysis combining the anthocyanin colored and colorless forms and the degradation products is provided. Overall, it appears that acylation is critical to color stability. For instance, the nonacylated pigment is rapidly bleached as a result of fast water addition and its iron complex is too unstable to provide protection. By contrast, the diacylated pigments are efficiently protected against hydration but much more moderately against autoxidation, which on the other hand is inhibited by efficient iron binding and addition of N-acetylcysteine. Finally, the diacylated pigments are much more resistant to bleaching by hydrogen peroxide (possibly produced by cyanidin autoxidation) and bisulfite (a common food preservative).

Preparation of chiral quantum dots.

Chiral quantum dots (QDs) are expected to have a range of potential applications in photocatalysis, as specific antibacterial and cytotoxic drug-delivery agents, in assays, as sensors in asymmetric synthesis and enantioseparation, and as fluorescent chiral nanoprobes in biomedical and analytical technologies. In this protocol, we present procedures for the synthesis of chiral optically active QD nanostructures and their quality control using spectroscopic studies and transmission electron microscopy imaging. We closely examine various synthetic routes for the preparation of chiral CdS, CdSe, CdTe and doped ZnS QDs, as well as of chiral CdS nanotetrapods. Most of these nanomaterials can be produced by a very fast (70 s) microwave-induced heating of the corresponding precursors in the presence of D- or L-chiral stabilizing coating ligands (stabilizers), which are crucial to generating optically active chiral QDs. Alternatively, chiral QDs can also be produced via the conventional hot injection technique, followed by a phase transfer in the presence of an appropriate chiral stabilizer. We demonstrate that the properties, structure and behavior of chiral QD nanostructures, as determined by various spectroscopic techniques, strongly depend on chiral stabilizers and that the chiral effects induced by them can be controlled via synthetic procedures.

Magnetic nanoparticles to recover cellular organelles and study the time resolved nanoparticle-cell interactome throughout uptake.

Nanoparticles in contact with cells and living organisms generate quite novel interactions at the interface between the nanoparticle surface and the surrounding biological environment. However, a detailed time resolved molecular level description of the evolving interactions as nanoparticles are internalized and trafficked within the cellular environment is still missing and will certainly be required for the emerging arena of nanoparticle-cell interactions to mature. In this paper promising methodologies to map out the time resolved nanoparticle-cell interactome for nanoparticle uptake are discussed. Thus silica coated magnetite nanoparticles are presented to cells and their magnetic properties used to isolate, in a time resolved manner, the organelles containing the nanoparticles. Characterization of the recovered fractions shows that different cell compartments are isolated at different times, in agreement with imaging results on nanoparticle intracellular location. Subsequently the internalized nanoparticles can be further isolated from the recovered organelles, allowing the study of the most tightly nanoparticle-bound biomolecules, analogous to the 'hard corona' that so far has mostly been characterized in extracellular environments. Preliminary data on the recovered nanoparticles suggest that significant portion of the original corona (derived from the serum in which particles are presented to the cells) is preserved as nanoparticles are trafficked through the cells.

Biomimetic synthesis of hierarchically porous nanostructured metal oxide microparticles--potential scaffolds for drug delivery and catalysis.

Hierarchically porous hybrid microparticles, strikingly reminiscent in their structure of the silica skeletons of single-cell algae, diatoms, but composed of titanium dioxide, and the chemically bound amphiphilic amino acids or small proteins can be prepared by a simple one-step biomimetic procedure, using hydrolysis of titanium alkoxides modified by these ligands. The growth of the hierarchical structure results from the conditions mimicking the growth of skeletons in real diatoms--the self-assembly of hydrolysis-generated titanium dioxide nanoparticles, templated by the microemulsion, originating from mixing the hydrocarbon solvent and water on action of amino acids as surfactants. The obtained microsize nanoparticle aggregates possess remarkable chemical and thermal stability and are promising substrates for applications in drug delivery and catalysis. They can be provided with pronounced surface chirality through application of chiral modifying ligands. They display also high selectivity in sorption of phosphorylated biomolecules or medicines as demonstrated by (1)H and (31)P NMR studies and by in vitro modeling using (32)P-marked ATP as a substrate. The release of the adsorbed model compounds in an inert medium is a very slow process directed by desorption kinetics. It is enhanced, however, noticeably in contact with biological fluids modeling those of the tissues suffering inflammation, which makes the produced material highly attractive for application in medical implants. The developed synthetic approach has been applied successfully also for the preparation of analogous hybrid microparticles based on zirconium dioxide or aluminum sesquioxide.

Chiral shells and achiral cores in CdS quantum dots.

We report and explain circular dichroism in semiconductor quantum dots. CdS nanocrystals capped with penicillamine enantiomers were prepared and found to be both highly luminescent and optically active. No new features in circular dichroism were observed as the nanocrystal grew larger. Density functional calculations reveal that penicillamine strongly distorts surface Cd, transmitting an enantiomeric structure to the surface layers and associated electronic states. The quantum dot core is found to remain undistorted and achiral.

Chiral highly luminescent CdS quantum dots.

Strongly white-emitting (lambda(max) = 495 +/- 10 nm) D- and L- penicillamine capped CdS nanoparticles, which show strong circular dichroism in the range 200-390 nm, have been prepared.