Polymerizations of Nitrophenylsulfonyl-Activated Aziridines

1-((<i>p</i>-Nitrophenyl)­sulfonyl)­aziridine (pNsAz) and 1-((<i>o</i>-nitrophenyl)­sulfonyl)­aziridine (oNsAz) were synthesized, and their polymerization chemistry was studied. Upon heating, pNsAz formed an insoluble white powder. In contrast, poly­(oNsAz) is soluble in DMF and DMSO. Attempts were made to convert poly­(oNsAz) to linear poly­(ethylenimine) (lPEI) through removal of the <i>o</i>-nosyl group using sodium thiomethoxide. Although some evidence for the formation of lPEI was found, formation of pure lPEI was not possible. oNsAz is susceptible to spontaneous polymerization when stored neat or in a polar solvent (e.g., DMSO and DMF). Poly­(oNsAz), formed from the spontaneous polymerization of oNsAz, was analyzed by MALDI-TOF mass spectrometry and composed of signals consistent with either OH or H₂O acting as initiators for an anionic polymerization. Experiments studying the kinetics of oNsAz showed that the rate of polymerization was first order with respect to monomer concentration. It was also possible to initiate the anionic polymerization of oNsAz using BnN­(Li)­Ms. At low oNsAz:BnN­(Li)­Ms ratios, some control over molecular weight was achieved; however, at higher ratios, control was no longer possible, likely due to the presence of protic impurities that contaminate the monomer. Chain extension and propargyl chloride termination experiments were also performed with BnN­(Li)­Ms initiated polymerization of oNsAz

MALDI MS In-Source Decay of Glycans Using a Glutathione-Capped Iron Oxide Nanoparticle Matrix

A new matrix-assisted laser desorption ionization (MALDI) mass spectrometry matrix is proposed for molecular mass and structural determination of glycans. This matrix contains an iron oxide nanoparticle (NP) core with gluthathione (GSH) molecules covalently bound to the surface. As demonstrated for the monosaccharide glucose and several larger glycans, the mass spectra exhibit good analyte ion intensities and signal-to-noise ratios, as well as an exceptionally clean background in the low mass-to-charge (<i>m</i>/<i>z</i>) region. In addition, abundant in-source decay (ISD) occurs when the laser power is increased above the ionization threshold; this indicates that the matrix provides strong energy transfer to the sample. For five model glycans, ISD produced extensive glycosidic and cross-ring cleavages in the positive ion mode from singly charged precursor ions with bound sodium ions. Linear, branched, and cyclic glycans were employed, and all were found to undergo abundant fragmentation by ISD. ¹⁸O labeling was used to clarify <i>m</i>/<i>z</i> assignment ambiguities and showed that the majority of the fragmentation originates from the nonreducing ends of the glycans. Studies with a peracetylated glycan indicated that abundant ISD fragmentation occurs even in the absence of hydroxyl groups. The ISD product ions generated using this new matrix should prove useful in the sequencing of glycans

SsnB inhibits ex vivo angiogenesis in the CAM assay.

<p>A. 100 µM SsnB decreased normalized total blood vessel length. B. 100 µM SsnB decreased normalized branching number. *p<0.05 vs. vehicle control, Newman-Keuls test. C. Representative micrographs demonstrating blood vessels in the CAM assay (left – vehicle control, right – 100 µM SsnB, circles show approximate position of methylcellulose discs).</p

Comparison of RT-PCR and Microarray Results.

<p>Fold expression change vs. vehicle control.</p

SsnB inhibits endothelial cell tube formation on Matrigel.

<p>A. Total tube length as a function of SsnB concentration in HUVECs. B. Total tube length as a function of SsnB concentration in HCAECs. *p<0.05 vs. vehicle control, Newman-Keuls test. C. Representative micrographs demonstrating tube formation in HUVECs (left – vehicle control, right – 100 µM SsnB).</p

SsnB inhibits endothelial cell migration.

<p>A. Migrated cells as a function of SsnB concentration (0.1 to 100 µM). B. Migrated cells as a function of SsnB concentration (0.0001 to 0.1 µM) shows a dose-dependent response. *p<0.05 vs. vehicle control, Newman-Keuls test. C. Representative micrographs demonstrating cell migration (left – vehicle control, center – negative control, right – 100 µM SsnB).</p

Sparstolonin B Inhibits Pro-Angiogenic Functions and Blocks Cell Cycle Progression in Endothelial Cells

<div><p>Sparstolonin B (SsnB) is a novel bioactive compound isolated from <i>Sparganium stoloniferum</i>, an herb historically used in Traditional Chinese Medicine as an anti-tumor agent. Angiogenesis, the process of new capillary formation from existing blood vessels, is dysregulated in many pathological disorders, including diabetic retinopathy, tumor growth, and atherosclerosis. In functional assays, SsnB inhibited endothelial cell tube formation (Matrigel method) and cell migration (Transwell method) in a dose-dependent manner. Microarray experiments with human umbilical vein endothelial cells (HUVECs) and human coronary artery endothelial cells (HCAECs) demonstrated differential expression of several hundred genes in response to SsnB exposure (916 and 356 genes, respectively, with fold change ≥2, p<0.05, unpaired t-test). Microarray data from both cell types showed significant overlap, including genes associated with cell proliferation and cell cycle. Flow cytometric cell cycle analysis of HUVECs treated with SsnB showed an increase of cells in the G1 phase and a decrease of cells in the S phase. Cyclin E2 (CCNE2) and Cell division cycle 6 (CDC6) are regulatory proteins that control cell cycle progression through the G1/S checkpoint. Both CCNE2 and CDC6 were downregulated in the microarray data. Real Time quantitative PCR confirmed that gene expression of CCNE2 and CDC6 in HUVECs was downregulated after SsnB exposure, to 64% and 35% of controls, respectively. The data suggest that SsnB may exert its anti-angiogenic properties in part by downregulating CCNE2 and CDC6, halting progression through the G1/S checkpoint. In the chick chorioallantoic membrane (CAM) assay, SsnB caused significant reduction in capillary length and branching number relative to the vehicle control group. Overall, SsnB caused a significant reduction in angiogenesis (ANOVA, p<0.05), demonstrating its <i>ex vivo</i> efficacy.</p></div

SsnB arrests endothelial cells in the G1 phase of the cell cycle.

<p>A. After 24, 30, and 36 hours of treatment, 100 µM SsnB decreased the percentage of cells in the S phase and increased the percentage of cells in the G1 phase. *p<0.005 vs. corresponding vehicle control, Newman-Keuls test. B. Representative cell cycle data demonstrating the increase in G1 cell percentage and decrease in S phase cell percentage after 24 hours of SsnB treatment (left – vehicle control, right – SsnB).</p

Quantitative MALDI-MS and Imaging of Fungicide Pyrimethanil in Strawberries with 2‑Nitrophloroglucinol as an Effective Matrix

This work explores the use of 2-nitrophloroglucinol (2-NPG) as a matrix for quantitative analysis of the fungicide Pyrimethanil (PYM) in strawberries using matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) and imaging. 2-NPG was selected for PYM analysis for optimum sensitivity and precision compared to common matrices α-cyano-4-hydroxylcinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB). PYM-sprayed strawberries were frozen 0, 1, 3, and 4 days after treatment and sectioned for MALDI imaging. The remaining part of each strawberry was processed using quick easy cheap effective rugged and safe (QuEChERS) extraction and analyzed by MALDI-MS and ultraperformance liquid chromatography multireaction-monitoring (UPLC-MRM). MALDI-MS showed comparable performance to UPLC-MRM in calibration, LOD/LOQ, matrix effect, and recovery, with the benefit of fast analysis. The MALDI imaging results demonstrated that PYM progressively penetrated the interior of the strawberry over time and the PYM concentration on tissue measured by MALDI imaging correlated linearly with MALDI-MS and UPLC-MRM measurements and accounts for 79% MALDI-MS and 85% UPLC-MRM values on average. Additionally, quartz crystal microbalance (QCM) was introduced as a new approach to determine strawberry tissue mass per area for MALDI imaging absolute quantitation with sensitive, direct, and localized measurements. This work demonstrates the first example of absolute quantitative MALDI imaging of pesticides in a heterogeneous plant tissue. The novel use of the 2-NPG matrix in quantitative MALDI-MS and imaging could be applied to other analytes, and the new QCM tissue mass per area method is potentially useful for quantitative MALDI imaging of heterogeneous tissues in general

Synthesis of 1,2-Dialkyl‑, 1,4(5)-Dialkyl‑, and 1,2,4(5)-Trialkylimidazoles via a One-Pot Method

Despite the utility of imidazoles for a wide variety of chemical and biological applications as well as the growing research in imidazolium-based ionic liquids (ILs), synthetic studies and characterization data for N-functionalized imidazole derivatives with substituents present at the C(2) and/or C(4) and/or C(5) positions are generally unreported. Here, we modify our prior method for synthesizing monofunctionalized imidazoles and apply it to the production of a library of 30 di- and trifunctionalized alkylimidazoles using only commodity chemicals and avoiding anhydrous solvents or air/water-sensitive reagents. For all products, purities of >98% could be readily achieved, although yields were lower than in our prior work with imidazole, which may be due to mass transfer limitations and/or increased nucleophilicity of substituted imidazole products. Interestingly, we also observe that, when 4-methylimidazole or 2-ethyl-4-methylimidazole is used as a starting material, two regioisomers are inevitably formed. We employed electronic structural calculations to aid in identifying the chemical shifts and quantifying the relative presence of the regioisomers. In both series of compounds where regioisomers could be formed, the 4-methyl regioisomer was favored. Although the formation of similar regioisomers has been previously noted in the literature, it has perhaps not been fully considered in works related to imidazolium-based ILs