Abstract Tryptophan (Trp) oxidation is a key biochemical process influencing plant development and numerous biomedical pathways. Here, we investigate how manganese doping modulates the catalytic behavior of titanium dioxide nanoparticles toward selective Trp oxidation. Mn-doped TiO2 nanoparticles containing 5%, 10%, and 20% Mn were systematically examined, while structurally related metal oxides (pristine TiO2, MnO2, MnFe2O4, maghemite (γ-Fe2O3), and industrial Fe3O4) were included as reference materials to establish catalytic benchmarks. Whereas the reference oxides predominantly promoted nonspecific reactive oxygen species (ROS) generation or exhibited lower catalytic efficiency, Mn-doped TiO2 displayed highly tunable reactivity. Specifically, 5% Mn doping favored broad-spectrum photocatalytic ROS production, whereas increasing the Mn content to 20% transformed the material from a conventional photocatalyst into a highly selective nanozyme. The 20% Mn-doped TiO2 exhibited superior biomimetic catalytic activity and was therefore subjected to detailed mechanistic studies. Nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) revealed highly selective, nanozyme-driven Trp oxidation pathways leading to the formation of auxin-mimicking metabolites. In vivo experiments using Arabidopsis thaliana demonstrated that the resulting metabolite cocktail significantly stimulated lateral root formation, indicating improved nutrient acquisition potential. Collectively, these findings establish Mn-doped TiO2 as a tunable catalytic platform capable of directing amino acid oxidation toward biologically relevant products and highlight its potential applications in agriculture and biomedicine.

One of the crucial metabolic processes for both plant and animal kingdoms is the oxidation of the amino acid tryptophan (TRP) that regulates plant growth and controls hunger and sleeping patterns in animals. Here, we report revolutionary insights into how this process can be crucially affected by interactions with metal oxide nanoparticles (NPs), creating a toolbox for a plethora of important biomedical and agricultural applications. Molecular mechanisms in TRP-NP interactions were revealed by NMR and optical spectroscopy for ceria and titania and by X-ray single-crystal study and a computational study of model TRP-polyoxometalate complexes, which permitted the visualization of the oxidation mechanism at an atomic level. Nanozyme activity, involving concerted proton and electron transfer to the NP surface for oxides with a high oxidative potential, like CeO2 or WO3, converted TRP in the first step into a tricyclic organic acid belonging to the family of natural plant hormones, auxins. TiO2, a much poorer oxidant, was strongly binding TRP without concurrent oxidation in the dark but oxidized it nonspecifically via the release of reactive oxygen species (ROS) in daylight.

Hyaluronan (HA), a member of the GAG family of glycans, has many diverse biological functions that vary a lot depending on the length of the HA chain and its concentration. A better understanding of the structure of different-sized HA at the atomic level is therefore crucial to decipher these biological functions. NMR is a method of choice for conformational studies of biomolecules, but there are limitations due to the low natural abundance of the NMR active nuclei 13C and 15N. We describe here the metabolic labeling of HA using the bacterium Streptococcus equi subsp. Zooepidemicus and the subsequent analysis by NMR and mass spectrometry. The level of 13C and 15N isotope enrichment at each position was determined quantitatively by NMR spectroscopy and was further confirmed by high-resolution mass spectrometry analysis. This study provides a valid methodological approach that can be applied to the quantitative assessment of isotopically labeled glycans and will help improve detection capabilities and facilitate future structure-function relationship analysis of complex glycans.

Hyaluronic acid (HA) cross-linked with 1,4-butanediol diglycidyl ether (BDDE) are hydrogels with many biomedical applications. Degree of substitution, cross-linking and substitution position of the cross-linker might influence the properties of the hydrogels. We showed earlier that the most common substitution position of the cross-linker on the hyaluronan chain was the 4-hydroxyl of N-acetylglucosamine. This result has led us to investigate unsulfated chondroitin (CN) which only differ from HA in the primary structure by the configuration at C4 of the aminoglycan. In the present study, we have investigated (i) the substitution positions of the cross-linker in CN using NMR and LC-MS and compared the results to the data obtained for HA (ii) the effect of alkali on the 13C and 1H chemical shifts in CN and HA (iii) the temperature coefficients and chemical shifts of hydroxyl protons in CN and HA. In CN, the 2-hydroxyl of glucuronic acid and 6-hydroxyl of N-acetylgalactosamine were found to be the major sites of substitution by BDDE. Moreover, while chondroitinase was not able to cleave HA tetrasaccharide substituted at the 4-hydroxyl GlcNAc reducing end by BDDE, it is able to degrade CN-BDDE down to disaccharide units.

Sequential carbohydrate synthesis is important for plant survival because it guarantees energy supplies for growth and development during plant ontogeny and reproduction. Starch and fructan are two important carbohydrates in many flowering plants and in human diets. Understanding this coordinated starch and fructan synthesis and unraveling how plants allocate photosynthates and prioritize different carbohydrate synthesis for survival could lead to improvements to cereals in agriculture for the purposes of greater food security and production quality. Here, we report a system from a single gene in barley employing two alternative promoters, one intronic/exonic, to generate two sequence-overlapping but functionally opposing transcription factors, in sensing sucrose, potentially via sucrose/glucose/fructose/trehalose 6-phosphate signaling. The system employs an autoregulatory mechanism in perceiving a sucrose-controlled trans activity on one promoter and orchestrating the coordinated starch and fructan synthesis by competitive transcription factor binding on the other promoter. As a case in point for the physiological roles of the system, we have demonstrated that this multitasking system can be exploited in breeding barley with tailored amounts of fructan to produce healthy food ingredients. The identification of an intron/exon-spanning promoter in a hosting gene, resulting in proteins with distinct functions, adds to the complexity of plant genomes.

Hyaluronic acid polymers cross-linked with BDDE are today among the most used hydrogels for biomedical applications. The physical properties of the hydrogels depend, among other parameters, on the degree of cross-linking of HA. Another parameter likely to affect the physical properties is the substitution position of the linker on the HA functional groups. A NMR-based method for the determination of these parameters in hyaluronic acid hydrogels is presented. The method is based on the degradation of HA cross linked hydrogels by chondroitinase ABC followed by one-dimensional 1H and 13C NMR analysis. The necessary structural information to obtain both the degree of cross-linking and the substitution positions can be obtained from the same NMR sample and no chromatographic separation step is required prior to NMR analysis.

In hydrogels of cross-linked polysaccharides, the total amount of cross-linker and the degree of cross-linking influence the properties of the hydrogel. The substitution position of the cross-linker on the polysaccharide is another parameter that can influence hydrogel properties; hence methods for detailed structural analysis of the substitution pattern are required. NMR and LC-MS methods were developed to determine the positions and amounts of substitution of 1,4-butanediol diglycidyl ether (BDDE) on hyaluronic acid (HA), and for the first time it is shown that BDDE can react with any of the four available hydroxyl groups of the HA disaccharide repeating unit. This was achieved by studying di-, tetra-, and hexasaccharides obtained from degradation of BDDE cross-linked HA hydrogel by chondroitinase. Furthermore, amount of linker substitution at each position was shown to be dependent on the size of the oligosaccharides. For the disaccharide, substitutions were predominantly at ΔGlcA-OH2 and GlcNAc-OH6 while in the tetra- and hexasaccharides, it was mainly at the reducing end GlcNAc-OH4. In the disaccharide there was no substitution at this position. Since chondroitinase is able to completely hydrolyse non-substituted HA into unsaturated disaccharides, these results indicate that the enzyme is prevented to cleave on the non-reducing side of an oligosaccharide substituted at the reducing end GlcNAc-OH4. The procedure can be adopted for the determination of substitution positions in other types of polymers.

Definitions and methods for the quantification of degree of modification and cross-linking in cross-linked hyaluronic acid (HA) hydrogels are outlined. A novel method is presented in which the HA hydrogel is degraded by the enzyme chondroitinase AC and the digest product analyzed by size exclusion chromatography combined with electrospray ionization mass spectrometry (SEC-ESI-MS). This method allows for the determination of effective cross-linker ratio (CrR) which together with the degree of modification (MoD), determined by, e.g. (1)H NMR spectroscopy, enables the calculation of the degree of substitution (DS) and degree of cross-linking (CrD). The method, could be applicable to the major cross-linked HA hydrogels currently on the market, and is exemplified here by application to two HA hydrogels. The definitions and methods presented are important contributions in attempts to find relationships between MoD, DS and CrD to mechanical properties as well as to biocompatibility of HA hydrogels.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Strontium titanate SrTiO3 thin films are highly perspective as gate dielectric material. Difference in volatility of the common homometallic precursors-strontium beta-diketonates and titanium alkoxides remains major hinder for preparation of high quality coatings based on this phase. An attractive alternative in its synthesis by MOCVD is provided by application of heterometallic mixed-ligand complexes, Sr2Ti2(beta-diket)4(OR)8(ROH)x. Mass-spectrometric study reveals, however, that none of these species can be considered a true single-source precursor. The relative stability of the molecules in solution and the congruence of in-situ release of homometallic species on evaporation are, on the other hand, crucial for the quality of the produced films and are strongly influenced by the nature of alkoxide ligands, OR. The historically first discovered representative of this heterometallic family, a sec-alkoxide derivative Sr2Ti2(thd)4(O(i)Pr)8, is in fact unexpectedly unstable, transforming in solution into Sr2Ti(thd)4(O(i)Pr)4((i)PrOH), which explains difficulties in keeping the correct stoichiometry using isopropoxide precursor. The primary alkoxide complexes, Sr2Ti2(thd)4(OR)8(ROH)2, R = Et, (n)Pr are also unstable yielding Sr4Ti2(thd)4(OR)8(ROH)2 on decomposition. The best solution stability and most uniform evaporation was observed for the iso-derivative, Sr2Ti2(thd)4(O(i)Bu)8, permitting to apply it in long term experiments under industrial process conditions. Present contribution provides detailed experimental comparison between and sec-and iso-alkoxide derivatives and sheds light on the influence of the ligand on molecular stability of a precursor and how it influences the quality of the derived oxide film, especially in relation to its electrophysical properties.

Nanoparticles of a Nd-doped LaAlO(3) perovskite can be obtained rapidly and with quantitative yield using the Bradley (ether elimination) treatment of a mixture of individual Ln(2)Al(2)(O(i)Pr)(12)((i)PrOH)(2), Ln = La, Nd, in acetophenone. The initially produced particles are poorly crystalline, but their crystallinity improves strongly on heating to 800 degrees C, which leads also to a controllable aggregation. The prepared nanoparticles are rather solution stable and can easily be surface-modified, which opens prospects for their use as phosphors in bioimaging applications. The precursors, bimetallic isopropoxides of rare earth elements and aluminum with a 1:1 composition, Ln(2)Al(2)(O(i)Pr)(12)((i)PrOH)(2), can be prepared with high yields via direct dissolution of metallic lanthanoids in a solution of aluminum isopropoxide in a toluene-isopropanol medium or through a short time reflux of "Ln(O(i)Pr)(3)" with 1 equiv of Al(O(i)Pr)(3) in toluene. In spite of good volatility and their proper composition, the Ln(2)Al(2)(O(i)Pr)(12)((i)PrOH)(2), Ln = La, Nd, do not act as single-source precursors in MOCVD, because of their quantitative transformation into LnAl(3)(O(i)Pr)(12) together with Ln(5)O(O(i)Pr)(13) on evaporation. These molecules are, however, present intact in solution according to variable temperature NMR studies, which permits application of them successfully as single source precursors in the synthesis of Ln:LaAlO(3) perovskite nanopowders with compositions thoroughly controlled through the conditions of the synthesis. Luminescent properties of the Nd:LaAlO(3) were examined and discussed in detail. The thermal population of the (4)F(5/2) and (2)H(9/2) states was found as a consequence of the grain size effect causing difficulties in heat dissipation. Moreover, luminescence behavior of the powder annealed at a lowest temperature shows well-defined short-range order.

Strontium titanate SrTiO3 thin films have attracted interest as a possible gate dielectric material. Preparation of its high quality coatings is hindered by difference in volatility of the homometallic precursors – strontium beta-diketonates and titanium alkoxides. The only earlier known single-source precursor, a sec-alkoxide derivative Sr2Ti2(thd)4(OiPr)8, has limited volatility. Bimetallic primary alkyl chain complexes, Sr4Ti2O(thd)4(OR)10(ROH)2, R=Et, nPr, are stable and volatile, but possess a wrong composition. Highly volatile precursor Sr2Ti2(thd)4(OiBu)8 has been prepared using an iso-alkoxide, combining proper ligand size with the sterical requirements, and characterized by multivariate evaporation analysis. Its evaporation is associated with complete decomposition into homometallic species, which, however, are evaporated in a single step. This permits to successfully use this novel precursor for SrTiO3 thin film deposition by DLI-MOCVD technique in a sufficiently broad established temperature range. Using optimized experimental conditions, 100nm thick strontium titanate films with high permittivity have been successfully obtained on (100) Si.

The tetragonal BaTiO(3) nanopowder is synthesized in a solvent-less, efficient process by the thermolysis of a single [Ba(2)Ti(2)(thd)(4)(OnPr)(8)(nPrOH)(2)] precursor in a closed reactor at 700 degrees C under autogenous pressure, followed by combustion. This paper compiles the synthesis of the [Ba(2)Ti(2)(thd)(4)(OnPr)(8)(nPrOH)(2)] precursor, its analysis by mass spectrometry, and implementation for the fabrication of dielectric tetragonal BaTiO(3) nanopowder by controlled efficient thermal decomposition. The as-prepared, intermediate, and final forms of the obtained nanomaterials are systematically analysed by XRD, Raman, and EDS measurements to gain structural and compositional information. Employing HR-SEM, TEM, and HR-TEM techniques, the morphological changes during the structural evolution of all the phases are pursued. The mechanistic elucidation for the fabrication of BaTiO(3) nanopowder is developed on the basis of TGA and DTA data obtained for the initial [Ba(2)Ti(2)(thd)(4)(OnPr)(8)(nPrOH)(2)] reactant as well as the as-prepared BaCO(3) with amorphous Ti phase.

Cation-doped perovskite materials based on barium titanate, such as (Ba,Sr)(Ti,Nb)O3, are of interest as transparent ceramic semiconductors with conductivity strongly dependent both on the cation and the oxygen stoichiometry. Development of precursor systems offering proper control over the cation stoichiometry and permitting to efficiently avoid residual carbon impurities is therefore an important problem. In the present communication we report the synthesis and structural characterization of a series of hetero-metallic precursors of these materials with the general formulae M2 IITi2(L)4(OR)8(ROH)2 and M2 IIM2 V(L)2(OR)12(ROH)2, where R = Et, nPr; MII = Ba, Sr; MV = Nb, Ta; L = thd or R’OAcAc (R’ = tBu, iPr). The compounds have been characterized by single crystal and power X-ray and by 1H and 13C NMR, vibration spectroscopy and mass-spectrometry. These species are very stable in solution and display even considerable gas phase stability. Solution microhydrolysis of the molecules in these series leads most often to oxo-aggregates with the cation stoichiometry rather close to 1:1, which additionally simplifies handling of solutions based on these precursors. The obtained precursors have been used for preparation of powders and films (on Si substrates), which were characterized by SEM-EDS and X-ray powder techniques.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Compounds Ga(OR)3 (R = Me, Et, Pri, Bun, C2H4OMe) were synthesized by exchange reactions between gallium chloride and alkali metal alkoxides, the reetherefication of Ga(OPri)3 and Ga(OC2H4OMe)3 by other ROH (R = Me, Et), and anodic dissolution of metallic gallium in the presence of a electroconductive additive (LiCl, Bu4NBr). When solid GaCl3 is introduced into an alcoholic solution of NaOEt, stable soluble gallium oxoalkoxyhalides are formed. The same reaction with a GaCl3 solution in toluene or electrochemical synthesis produces nonvolatile Ga(OEt)3 samples, which have the polymer zigzag configuration [Ga(OR)4/2(OR)]∞. Mass spectrometry shows that only Ga(OPri)3 and freshly prepared X-ray amorphous Ga(OEt)3 samples (produced by reetherefication) are transferred to the gas phase. The spectra of the latter contain ions generated by penta-and hexanuclear oxoalkoxide molecules, along with fragments of orthospecies [Ga(OEt)3]2−4. IR spectra are described for all compounds synthesized.

Antifungal compounds from cultures of five type strains of dairy propionibacteria, as well as from the cultivation medium, were studied. Cell-free supernatants and medium were fractionated by C(18) solid phase extraction. The aqueous 95% acetonitrile fractions were analyzed by GC-MS or subjected to reversed-phase HPLC, to identify, quantify or isolate antifungal substances. The resulting HPLC fractions were screened for antifungal activity against the mold Aspergillus fumigatus and the yeast Rhodotorula mucilaginosa. Active fractions were further separated by HPLC and the structures of the compounds were determined by spectroscopic and chromatographic methods. All five strains produced 3-phenyllactic acid, at concentrations ranging from 1.0 microg mL(-1) (Propionibacterium freudenreichii ssp. shermanii) to 15.1 microg mL(-1) (Propionibacterium thoenii), and at L/D -ratios ranging from 2 : 3 (Propionibacterium acidipropionici) to 9 : 1 (Propionibacterium freudenreichii). A number of active compounds found in cultures of propionibacteria were also present in noninoculated growth medium: two antifungal diketopiperazines, cyclo(L-Phe-L-Pro) and cyclo(L-Ile-L-Pro), and seven antifungal linear peptides. Three of the linear peptides corresponded to sequences found in the medium component casein, suggesting their origin from this component, whereas the diketopiperazines were suggested to be formed from medium peptides by heat treatment.

The thermal decomposition of a ZrTi2[(OC2H4)(2)NH](3)(OC3H7)(6) precursor by the RAPET (reaction under autogenic pressure at elevated temperature) method provided the formation of crystalline zirconium titanate nanoparticles. These as-prepared nanoparticles are embedded in a carbon shell, which can be removed completely by calcination at 500 degrees C under air for 3 h, resulting in pure white crystalline nanoparticles. At a reaction temperature of 700 degrees C, the nanoparticles are mainly ZrTi2O6 (srilankite), whereas at 800 degrees C, the product is predominately Zr5Ti7O24. The structural, morphological, compositional, magnetic, and AC electrical properties are measured for the as-prepared ZrTi2O6 embedded in carbon (ZTEC), as well as the crystalline ZrTi2O6 nanoparticles (ZTN) obtained after sintering. The reaction mechanism is based on the decomposition products containing pyrrol and pyrazine. The presence of these compounds provides an understanding of the decomposition of the diethanolamine ligands and the formation of the nanoparticles in general.

Heterometallic alkoxide complexes possessing a triangular M-3(mu-OR)(2)(mu-OR)(3) core are usually highly soluble in organic solvents and often display relatively high stability on transition into gas phase. Each metal atom is connected to four ligands within the core and needs two more donor atoms from the terminal ligands to complete octahedral coordination. This can be achieved for Ni(II), for example, by application of a bidentate chelating ligand such as the acetylacetonate one. Interaction of Ni(acac)2 with 1.5 eq. of [Zr((OPr)-Pr-i)(4)((PrOH)-Pr-i)](2) in toluene offers quantitatively [Zr((OPr)-Pr-i)(3)(acac)(2)] together with the bimetallic complex NiZr2(acac)((OPr)-Pr-i)(9) (1), possessing the desired structure and physical properties. (c) 2006 Elsevier B.V. All rights reserved.