Electrospray Mass Spectrometry Analysis Research Articles

Selective Synthesis of Deuterated cis- and trans-Isohumulones and trans-Isohumulinones

AbstractDeuterated isohumulones can be prepared directly from humulones by an acyloin ring contraction under either magnesium-catalyzed basic conditions or by photochemical-induced reactions in deuterated solvents. Reactions of humulones with biphasic methylene chloride/aqueous NaOD and MgSO4 in D2O leads to stereoselective formation of cis-d 3-isohumulones (cis/trans ratio of 82:18) as the magnesium salts in yields of 71–83%. Greater than 95% incorporation of three deuterons is observed at the C5 position of the pentenone ring and the methylene position of the C4 acyl group. Photochemical isomerization with a 400 nm blue LED source enables stereospecific formation of deuterated trans-isohumulones in 36–82% yield with greater than 95% incorporation of deuterium at the C5 ring position. Oxidation of humulones with cumene hydroperoxide in basic D2O gives isohumulinones with partial 55–73% incorporation of deuterium due to keto–enol isomerization of the methylene substituent of the C4 acyl group. The structural identities of the deuterated products are determined by a combination of negative-mode electrospray mass spectrometry (MS-ESI–) and 2D heteronuclear proton–carbon HMQC NMR analysis.

A novel bidentate diamide ligand DODQ for the separation of uranium and rare earth ions in nitric acid medium

High efficiency extractants play a necessary role in the selective removal of uranium from rare earth minerals. In this paper, a novel cyclic bidentate diamine extractant, 1, 4-dioctyl-1, 4-dihydroquinoxaline-2, 3-dione (DODQ), was synthesized, and the complexation and extraction of UO22+ in nitric acid medium were systematically studied. The results indicate that DODQ exhibits a unique combination of properties in removing UO22+, with an extraction capacity 132 times higher than that of DODPhOA (acyclic structure). Extraction isotherm experiments and slope analyses illustrate the formation of a 1:1 DODQ/UO22+ regime during the extraction process. Electrospray mass spectrometry, fluorescence spectroscopy, and X-ray crystal diffraction analyses further corroborated its stoichiometric properties. In addition, DODQ can remove UO22+ from rare earth solutions containing UO22+ with high selectivity. This study provides an alternative method to separate uranium from the leaching solution of rare earth ore and has a new understanding of the coordination and complexing behavior of UO22+ with bidentate oxygen-containing ligands.

Comparative Estimation of the Cytotoxic Activity of Different Parts of Cynara scolymus L.: Crude Extracts versus Green Synthesized Silver Nanoparticles with Apoptotic Investigation.

Different parts of Cynara scolymus L. and their green synthesized eco-friendly silver nanoparticles (AgNPs) were screened for their cytotoxicity and apoptotic activity. Results showed that flower extract AgNPs exhibited more potent cytotoxicity compared to the normal form against PC-3 and A549 cell lines with IC50 values of 2.47 μg/mL and 1.35 μg/mL, respectively. The results were compared to doxorubicin (IC50 = 5.13 and 6.19 μg/mL, respectively). For apoptosis-induction, AgNPs prepared from the flower extract induced cell death by apoptosis by 41.34-fold change and induced necrotic cell death by 10.2-fold. Additionally, they induced total prostate apoptotic cell death by a 16.18-fold change, and it slightly induced necrotic cell death by 2.7-fold. Hence, green synthesized flower extract AgNPs exhibited cytotoxicity in A549 and PC-3 through apoptosis-induction in both cells. Consequently, synthesized AgNPs were further tested for apoptosis and increased gene and protein expression of pro-apoptotic markers while decreasing expression of anti-apoptotic genes. As a result, this formula may serve as a promising source for anti-cancer candidates. Finally, liquid chromatography combined with electrospray mass spectrometry (LC-ESI-MS) analysis was assessed to identify the common bioactive metabolites in crude extracts of stem, flower, and bract.

Sulfated modification of hyaluronan tetrasaccharide enhances its antitumor activity on human lung adenocarcinoma A549 cells in vitro and in vivo

Hyaluronan (HA) is a glycosaminoglycan polymer involved in cell phenotype change, inflammation modulation, and tumor metastasis progression. HA oligosaccharides have a higher solubility and drug-forming ability than polysaccharides. HA tetrasaccharide was reported as the smallest fragment required for inhibiting triple-negative breast cancer, but the anti-tumor activity of HA tetrasaccharide (HA4) and its sulfated derivatives in lung cancer is still unknown. In this study, HA4 was prepared via HA degradation by chondroitinase ABC (CSABC), while its sulfated derivatives were prepared by sulfur pyridine trioxide complex in N, N-dimethylformamide (DMF). Then, the anti-tumor activity was detected via MTT assay and xenograft tumor experiments, while the expression level change of apoptosis genes was analyzed by qRT-PCR. Electrospray mass spectrometry (ESI-MS) analysis showed several HA4 sulfated derivatives, GlcA2GlcNAc2 (SO3H)n contains 0–6 sulfation groups, which mainly contain 3–6, 2–3, and 0–1 sulfation groups were classified as HA4S1, HA4S2, and HA4S3, respectively. After the addition of 1.82 mg/mL HA4, HA4S1, HA4S2, and HA4S3, the cell viability of A549 cells was reduced to 81.2 %, 62.1 %, 50.3 %, and 65.9 %, respectively. Thus, HA4S2 was chosen for further measurement, the qRT-PCR results showed it significantly up-regulated the expression of genes in the apoptosis pathway. Moreover, HA4S2 exhibited stronger antitumor activity than HA4 in vivo and the tumor inhibition rate reached 36.90 %. In summary, this study indicated that the CSABC enzyme could effectively degrade HA into oligosaccharides, and sulfation modification was an effective method to enhance the antitumor activity of HA tetrasaccharides.

Isolation of N-Ethyl-2-pyrrolidinone-Substituted Flavanols from White Tea Using Centrifugal Countercurrent Chromatography Off-Line ESI-MS Profiling and Semi-Preparative Liquid Chromatography

N-Ethyl-2-pyrrolidinone-substituted flavanols (EPSF) are marker compounds for long-term stored white teas. However, due to their low contents and diasteromeric configuration, EPSF compounds are challenging to isolate. In this study, two representative epimeric EPSF compounds, 5′′′R- and 5′′′S-epigallocatechin gallate-8-C N-ethyl-2-pyrrolidinone (R-EGCG-cThea and S-EGCG-cThea), were isolated from white tea using centrifugal partition chromatography (CPC). Two different biphasic solvent systems composed of 1. N-hexane-ethyl acetate-methanol-water (1:5:1:5, v/v/v/v) and 2. N-hexane-ethyl acetate-acetonitrile-water (0.7:3.0:1.3:5.0, v/v/v/v) were used for independent pre-fractionation experiments; 500 mg in each separation of white tea ethyl acetate partition were fractionated. The suitability of the two solvent systems was pre-evaluated by electrospray mass-spectrometry (ESI-MS/MS) analysis for metabolite distribution and compared to the results of the CPC experimental data using specific metabolite partition ratio KD values, selectivity factors α, and resolution factors RS. After size-exclusion and semi-preparative reversed-phase liquid chromatography, 6.4 mg of R-EGCG-cThea and 2.9 mg of S-EGCG-cThea were recovered with purities over 95%. Further bioactivity evaluation showed that R- and S-EGCG-cThea possessed in vitro inhibition effects on α-glucosidase with IC50 of 70.3 and 161.7 μM, respectively.

Coelomic fluid of Echinometra mathaei: The new prospects for medicinal antioxidants

Echinoid pigments have various biological properties such as antioxidant, cytotoxic, and antibacterial activities. We aimed to evaluate the extraction of cell-free coelomic fluid (CFCF) and coelomocyte lysate (CL) as well as qualitatively and quantitatively identify the coelomic fluid of Echinometra mathaei as a new source of polyhydroxylatednaphthoquinone (PHNQ) antioxidant pigments. Based on the High Performance liquid chromatography–electrospray mass spectrometry (HPLC-MS) analysis in negative mode, the main quinonoid (PHNQ) pigments were identified and quantified. This study also illustrated the total ion current chromatograms and related mass spectra of Spinochrome A, Spinochrome B, Spinochrome C, and Echinochrome A in CL and SpinochromeC in CFCF samples. The ions at 221, 279, 265 and 263 m/z correspond to the pseudo-molecular [M − H] ions of Spinochrome B, Spinochrome C, Echinochrome A, and Spinochrome A, respectively. These components have previously been noted from the shells and spines of sea urchins but identification of PHNQs pigments in CL and CFCF of E. mathaei using LC-MS was introduced for the first time. The results also showed that, the highest DPPH radical scavenging activity of CFCF (88.12 DPPH% scavenging at 70 μg/mL, IC50 = <10 μg/mL). The findings clearly suggest that the coelomic fluid of E. mathaei could be served as the promising as well as potential natural antioxidants in the medical and pharmaceutical industries and could replace the increasing prices of the commercial antioxidants products.

English

Hemileia vastatrix is a fungus associated with coffee leaf rust, the most destructive disease of Coffea arabica. The objective of this work was to evaluate the antifungal activity of alcoholic extracts from roots of Baccharis salicina and to determine the metabolites present in these fractions. Antifungal activity was evaluated under in vitro conditions by monitoring the germination ability of H. vastatrix, the coffee leaf rust pathogen. In order to determine the presence of metabolites, chemical characterization of fractions obtained from methanolic root extracts was performed with help of an untargeted metabolomic approach and by using high-resolution mass spectrometry (MS) and MS2 based on direct-injection electrospray mass spectrometry (DIESI-MS) and hierarchical cluster analysis (HCA). Germination percentage was evaluated by leaves fixation technique. The MEBs significantly decreased the percentage of germination of H. vastatrix to levels below 5% as the dose increased. The multivariable analysis confirmed that the distribution of three fractions of methanolic extracts belonged to polyketides, organoheterocyclic compounds, fatty acyls, prenol-lipids, organo-oxygen and farnesene classes. This report comprises the first study of the metabolomic profile and biological activity study of roots from B. salicina against coffee leaf rust pathogen H. vastatrix. © 2021 Friends Science Publishers

Electrospray mass spectrometry analysis of blastocoel fluid as a potential tool for bovine embryo selection.

The aim of this study was to analyze the metabolic profiles of blastocoel fluid (BF) obtained from bovine embryos produced in vivo and in vitro. Expanded blastocysts (20/group) that were in vitro and in vivo derived at day 7 were used. BF was collected and analyzed under direct infusion conditions using a microTOF-Q® mass spectrometer with electrospray ionization and a mass range of 50-650 m/z. The spectrometry showed an evident difference in the metabolic profiles of BF from in vivo and in vitro produced embryos. These differences were very consistent between the samples of each group suggesting that embryo fluids can be used to identify the origin of the embryo. Ions 453.15 m/z, 437.18 m/z, and 398.06 m/z were identified as biomarkers for the embryo's origin with 100% sensitivity and specificity. Although it was not possible to unveil the molecular identity of the differential ions, the resulting spectrometric profiles provide a phenotype capable of differentiating embryos and hence constitute a potential parameter for embryo selection. To the best of our knowledge, our results showed, for the first time, an evident difference between the spectrometric profiles of the BF from bovine embryos produced in vivo and in vitro.

Abstract P102: Generation Of A Novel Peptoid-peptide Analog Of Alpha-calcitonin Gene Related Peptide (α-CGRP) For The Treatment And Prevention Of Cardiovascular Diseases

Alpha-calcitonin gene related peptide (α-CGRP) is a 37-amino acid cardioprotective neuropeptide. Studies carried out in our laboratory and others establish α-CGRP as a potential therapeutic agent against a variety of cardiovascular diseases. However, the short half-life of α-CGRP limits its use in any long-term treatment regime. The goal of the present study is to develop an α-CGRP agonist analog with extended bioavailability using peptoid chemistry. A peptoid is a N -substituted glycine peptidomimetic molecule and is identical to α-amino acid except that the side chain in a peptoid is attached on the nitrogen rather than the α-carbon atom. Inclusion of a peptoid makes the native peptide protease-resistant and thus biostable in vivo . Using a solid-phase submonomer method, we synthesized a novel human α-CGRP analog containing two monomers of N -methoxyethylglycine (NMEG) peptoid at the N-terminus. Electrospray mass spectrometry (MALDI-TOF) analysis showed that the molecular mass of synthesized peptoid-peptide hybrid, NMEG-α-CGRP, was 4044 that is ~6.7% more than native peptide. An in vitro trypan blue cell exclusion assay demonstrated that incubation of NMEG-α-CGRP (5 μM) for 7 days did not affect the viability of rat H9C2 and mouse HL-1 cardiac cells. To evaluate the biological activity of NMEG-α-CGRP, a subcutaneous injection of human α-CGRP (10 μg/mice) and NMEG-α-CGRP (1, 3, 10, and 30 μg/mice) were given in 9-week-old C57BL6 mice (n=2 mice/dose), and blood pressure (BP) was measured using a tail-cuff method. A dose response curve showed that NMEG-α-CGRP decreased BP in mice in a time-dependent manner. Beginning with and injection of 3 μg of NMEG-α-CGRP, a dip in BP (85 ± 1 mmHg; in ±SD) was observed at 10 min after injection, and BP returned to baseline (125 mmHg) by 6 h, 18 h, and 24 h when injected with 3, 10, and 30 μg doses, respectively. Moreover, 10 μg of human-α-CGRP and NMEG-α-CGRP lowered BP from baseline for 2 h and 18 h, respectively, suggesting that NMEG addition increased stability, and thus bioavailability, of α-CGRP in vivo . In summary, our results show that a NMEG based α-CGRP modification is an effective approach to increase stability and, thus, bioavailability of α-CGRP in vivo making α-CGRP a viable therapeutic drug to treat cardiovascular diseases.

Salivary proteomic profile of patients with renal cell carcinoma.

622 Background: We aimed to explore the salivary proteomic profile (SPP) of patients undergoing surgery for suspected renal cell carcinoma (RCC), then evaluate any significant findings in a validation cohort. Methods: Prospective IRB approved trial of consecutive patients with suspected RCC undergoing curative surgery. Saliva was collected pre- and postoperatively, and from healthy volunteers. Saliva was mixed with sodium orthovanadate and protease inhibitor, aliquoted, and frozen at -80oC. SPP performed using biomarker concentrated saliva via core-shell hydrogel nanoparticles functionalized with molecular baits coupled to high resolution MS/MS electrospray mass spectrometry analysis; output represented as spectral counts. Wilcoxon Rank Sum test was used for comparisons; p-values were adjusted using false discovery rate (FDR) for multiple testing. Results: Exploratory phase: saliva was collected from 27 volunteers and 34 RCC patients (24 clear cell (cc)RCC, 6 chromophobe (ch)RCC, 4 other). Evaluation of cc vs chRCC revealed differential counts for 56 proteins; none were significant after adjustment by FDR. Comparison of matched pre/post-operative SPP in 14 ccRCC patients identified differential counts of 3 proteins: basic salivary proline-rich protein 3 precursor; prolactin-inducible protein precursor; and submaxillary gland androgen-regulated protein 3B precursor. These were not affected by patient age, partial/radical nephrectomy, or tumor size/stage/grade. Validation phase: power analyses indicated a sample size of 38/53 patients = 90% power = effect size of 0.6/0.5, respectively, 2-sided Type 1 error of 0.025. 49 ccRCC patients were enrolled with pre/postop saliva. 611 proteins were identified; none had differential counts after FDR. Conclusions: Using a unique biomarker technology coupled to high resolution MS, interesting SPP’s were seen between RCC subtypes and before/after ccRCC curative resection. We were unable to show significant differences in pre/post-op levels. More research is needed to further study the SPP in RCC patients and the factors impacting their differential expression. In order to aid such efforts, the raw data will be made available for future researchers.

Synthesis and Structural Characterization of a Ubiquitous Transformation Product (BTS 40348) of Fungicide Prochloraz.

Prochloraz is a widely used imidazole fungicide that has to be analyzed together with its metabolites or transformation products for food safety monitoring purposes in the European Union. Although the focus in food of plant origin has been set on metabolites BTS 44595 and BTS 44596, we consider relevant the study of BTS 40348 metabolite, too, because it has been detected in both raw and processed foods based on citrus fruits in the EU. Metabolite BTS 40348 should be monitored in surface water due to its ecotoxicological effects. In this work, the synthesis and structural characterization of BTS 40348 metabolite of fungicide prochloraz is presented, because the structure is closely related to the chemistry and biological activity of the substance. Characterization using 13C and 1H NMR, infrared (IR), and Raman spectroscopy is detailed, together with confirmation by electrospray mass spectrometry analysis.

Interaction of metal ions with tau protein. The case for a metal-mediated tau aggregation

Tau protein aggregation and its hyperphosphorylation play an important role in the pathogenesis of Alzheimer's disease. There is also considerable evidence for the accumulation of Fe2/3+, Cu2+, and Zn2+ in the brain of Alzheimer's patients, although their involvement in the etiology of the disease remains unknown. Here, interactions of the 3d metal ions Fe2/3+, Cu2+, and Zn2+ with the longest isoform of the human tau protein (htau40) are studied in detail. Electrospray mass spectrometry and ion mobility mass spectrometry analyses confirm the interactions of metal species with tau and that these interactions cause structural changes. Phosphorylation of the full-length htau40 with glycogen synthase kinase 3β (GSK3β), a protein kinase, causes a reduction in metal interactions. Transmission electron microscopy studies of the tau aggregates formed in the presence of metal ions suggest that the presence of metal ions influences the aggregation process. Fluorescence studies of full-length htau40 in the presence of Cu2+ indicate the formation of reactive oxygen species, which may contribute further to oxidative stress and neuronal death.

Photocatalytic and Photoelectrochemical Degradation of Organic Compounds with All-Inorganic Metal Halide Perovskite Quantum Dots.

Inspired by the outstanding optoelectronic properties reported for all-inorganic halide perovskite quantum dots (QDs), we have evaluated the potential of these materials toward the photocatalytic and photoelectrochemical degradation of organic compounds, taking the oxidation of 2-mercaptobenzothiazole (MBT) as a proof-of-concept. First, we determined electrochemically the energy levels of dispersions of perovskite QDs with different band gaps induced by the different ratios between halides (Br and I) and metallic cations (Pb and Sn). Then, we selected CsPbBr3 QDs to demonstrate the photocatalytic and photoelectrochemical oxidation of MBT, confirming that hole injection takes place from CsPbBr3 QDs to MBT, resulting in the total degradation of MBT as evidenced by electrospray mass spectrometry analyses. Although the stability and toxicity of these QDs are major issues to address in the near future, the results obtained in the present study open promising perspectives for the implementation of solar-driven catalytic strategies based on these fascinating materials.

Synthesis, single crystal X-ray structures of ONNO, ONN and ONS-Pd(II) complexes and their anticancer activities

Abstract Pd(salicylaldimine)2 (ONNO-Pd)(C1 and C2), Pd(salicylaldimine)Cl (ONN-Pd) (C3) and methionine derived ONS donor ligand based (ONS-Pd) Pd(salicylaldimine methionine ethyl ester)Cl (C4) complexes were prepared and structurally characterized by 1H, 13C NMR spectroscopy, high-resolution electrospray mass spectrometry and single crystal X-ray analyses (C1, C2 and C4). In C1 and C2 two ON-donor salicylaldimine ligands completed four coordinates of Pd(II) while in C4 these coordinate were completed by ONS-donor atoms of salicylaldimine and one Cl ancillary ligand. In vitro cytotoxicity assays were performed for these complexes in non-small cell lung (A549) and hepatocellular (HepG2) cancer cells. MTT assay showed that these Pd complexes suppress cancer cells viability and inhibited cell growth in dose and time-dependent manner. Cell cycle analysis was performed in A549 cells. To check the interaction of these complexes with DNA gel electrophoresis study was performed that revealed stronger binding affinity of these complexes with DNA.

More than Expected: Overall Initiation Efficiencies of Mono-, Bis-, and Tetraacylgermane Radical Initiators

We introduce a quantitative comparison of the overall initiation efficiency for a library of eight mono-, bis-, and tetraacylgermane visible light photoinitiators with p-methoxy and fluorine substitution patterns. Specifically, cocktail experiments were carried out, fusing pulsed laser polymerization (PLP) of methyl methacrylate (MMA) with subsequent high-resolution electrospray mass spectrometry (ESI-MS) analysis. The overall initiation efficiency reflects all critical events leading to macromolecular growth, i.e., from light absorption and cleavage of the initiator to radical initiation. Importantly, we show that the obtained overall initiation efficiencies are self-consistent when going from lower to higher substituted systems, evidencing the validity of the derived overall initiation efficiencies within the error margins of the experiment. Remarkably, the comparison of mono-, bis-, and tetraacylgermanes reveals a nonstoichiometric increase of 40–90% in the overall initiation efficiency with increasing...

Antifungal Activity of Lipopeptides From Bacillus XT1 CECT 8661 Against Botrytis cinerea.

This work aims to explore the capacity of a Bacillus methylotrophicus (later heterotypic synonym of Bacillus velezensis) strain named XT1 CECT 8661 against the necrotrophic plant pathogen Botrytis cinerea and to identify the compounds responsible for its activity. Q_TOF electrospray mass spectrometry analysis allows us to detect several lipopeptides – surfactin, bacillomycin, and fengycin – in XT1 cultures. In vitro antibiosis studies demonstrated the efficiency of the lipopeptide fraction for the inhibition of fungal growth. In fact, microscopy studies (SEM/TEM) revealed, an alteration of the morphology of the phytopathogen in interaction with lipopeptides, with resistance structures appearing in the early stages of growth of the fungus. Our studies, carried out with tomatoes, grapes, and strawberries have demonstrated the efficiency of Bacillus XT1 CECT 8661 lipopeptides against B. cinerea infection and it capability to trigger the antioxidant activity in fruit. Overall, the results of this study highlight the potential of lipopeptides of this strain as an effective biological control agent against the colonisation of B. cinerea.

Tannins from Acacia mearnsii De Wild. Bark: Tannin Determination and Biological Activities.

The bark of Acacia mearnsii De Wild. (black wattle) contains significant amounts of water-soluble components acalled “wattle tannin”. Following the discovery of its strong antioxidant activity, a wattle tannin dietary supplement has been developed and as part of developing new dietary supplements, a literature search was conducted using the SciFinder data base for “Acacia species and their biological activities”. An analysis of the references found indicated that the name of Acacia nilotica had been changed to Vachellia nilotica, even though the name of the genus Acacia originated from its original name. This review briefly describes why and how the name of A. nilotica changed. Tannin has been analyzed using the Stiasny method when the tannin is used to make adhesives and the hide-powder method is used when the tannin is to be used for leather tanning. A simple UV method is also able to be used to estimate the values for both adhesives and leather tanning applications. The tannin content in bark can also be estimated using NIR and NMR. Tannin content estimations using pyrolysis/GC, electrospray mass spectrometry and quantitative 31P-NMR analyses have also been described. Tannins consists mostly of polyflavanoids and all the compounds isolated have been updated. Antioxidant activities of the tannin relating to anti-tumor properties, the viability of human neuroblastoma SH-SY5Y cells and also anti-hypertensive effects have been studied. The antioxidant activity of proanthocyanidins was found to be higher than that of flavan-3-ol monomers. A total of fourteen papers and two patents reported the antimicrobial activities of wattle tannin. Bacteria were more susceptible to the tannins than the fungal strains tested. Several bacteria were inhibited by the extract from A. mearnsii bark. The growth inhibition mechanisms of E. coli were investigated. An interaction between extracts from A. mearnsii bark and antibiotics has also been studied. The extracts from A. mearnsii bark inhibit the growth of cyanobacteria. Wattle tannin has the ability to inactivate α-amylase, lipase and glucosidase. In vivo experiments on anti-obesity and anti-diabetes were also reported. Several patents relating to these enzymes for anti-diabetes and anti-obesity are in the literature. In addition, studies on Acacia bark extract regarding its antitermite activities, inhibition of itching in atopic dermatitis and anti-inflammatory effects have also been reported. The growth of bacteria was inhibited by the extract from A. mearnsii bark, and typical intestinal bacteria such as E. coli, K. pneumoniae, P. vulgaris and S. marcescenes was also inhibited in vitro by extracts. Based on these results, the Acacia bark extract may inhibit not only the growth of these typical intestinal bacteria but also the growth of other types of intestinal bacteria such as Clostridium and Bacteroides, a so-called “bad bacteria”. If the tannin extract from A. mearnsii bark inhibits growth of these “bad bacteria” in vivo evaluation, the extracts might be usable as a new dietary supplement, which could control the human intestinal microbiome to keep the body healthy.

Bioconversion of Tetracycline Antibiotics to Novel Glucoside Derivatives by Single-Vessel Multienzymatic Glycosylation.

The single-vessel multienzyme UDP-α-D-glucose recycling system was coupled with a forward glucosylation reaction to produce novel glucose moiety-conjugated derivatives of different tetracycline antibiotic analogs. Among five tetracycline analogs used for the reaction, four molecules (chlorotetracycline, doxytetracycline, meclotetracycline, and minotetracycline) were accepted by a glycosyltransferase enzyme, YjiC, from Bacillus licheniformis to produce glucoside derivatives. However, the enzyme was unable to conjugate sugar units to rolitetracycline. All glucosides of tetracycline derivatives were characterized by ultraviolet absorbance maxima, ultra-pressure liquid chromatography coupled with photodiode array, and high-resolution quadruple time-of-flight electrospray mass spectrometry analyses. These synthesized glucosides are novel tetracycline derivatives.

Anion-templated nanosized silver clusters protected by mixed thiolate and diphosphine.

S2-, MoO42-, and Mo6O228- were successfully employed as templates in the formation of six high-symmetry polynuclear silver clusters as exemplified in the single-crystal X-ray structures of [S@Ag18(tBuC6H4S)16(dppp)4]·DMF·5CH3CN·3CH3OH (1), [MoO4@Ag24(MeC6H4S)12(dppm)6(MoO4)4]·2BF4·C2H5NO (2), [MoO4@Ag24(MeC6H4S)12(dppm)6(MoO4)4]·2CF3SO3 (3), [MoO4@Ag24(MeC6H4S)12(dppf)6(MoO4)4]·2CF3SO3 (4), [MoO4@Ag24(MeC6H4S)12(dppb)6(MoO4)4]·2CF3SO3 (5) and [Mo6O22@Ag46(tBuC6H4S)32(dppm)4(CH3CN)8]·6CF3SO3 (6) (dppp = 1,3-bis(diphenylphosphino)propane, dppm = bis(diphenylphosphino)methane, dppf = 1,1'-bis(diphenylphosphino)ferrocene and dppb = 1,4-bis(diphenylphosphino)butane). Cluster 1 is a S2--centered octadecanuclear banana-shaped molecule. Clusters 2-5 have similar structures consisting of a tetrahedron of a MoO42- core and four MoO42- where three silver atoms cap each face and a pair sits on each edge, giving tetraicosanuclear ball-shaped molecules. Although different diphosphine ligands and silver salts were used in the syntheses, 2-5 contain a common building cluster unit with similar geometry and nuclearity. With (Bu4N)2Mo6O19 as a template, a giant 46-silver-atom cluster encapsulates an in situ modified Mo6O228- unit. The nuclearity and geometry depend on the size and shape of the templates. High-resolution electrospray mass spectrometry (HR-ESI-MS) analyses of 4 indicate its exceptionally high stability in acetonitrile. The solid-state luminescence of 1 as a function of the temperature exhibits thermochromism from red to yellow due to the different intensities of the two bands. This work established a new strategy for the construction of polynuclear silver clusters using an anionic template and mixed S- and P-donor ligands where a promising approach for building novel dual emissive materials is unraveled.

Analytical study of rhenium complexes with pyrogallol and catechol

Selected rhenium complexes with pyrogallol (1,2,3-trihydroxybenzene) and catechol (1,2-dihydroxybenzene) as strongly bound ligands were prepared by a reaction of rhenium precursor tetrabutylammonium-tetrachlorooxorhenate with twofold molar excess of ligand in presence of various amounts of triethylamine. The structures of formed complexes and their consequent reaction products were estimated by means of mass spectrometry with electrospray ionization. The kinetics of reactions in course of complex formation and consequent decomposition were primarily followed by UV–Vis absorption spectra measurement, complemented by single or continuous electrospray mass spectrometry analyses.