Carbohydrate and steroid analysis by desorption electrospray ionization mass spectrometry

Desorption electrospray ionization mass spectrometry (DESI-MS) is applied to the analysis of carbohydrates and steroids; the detection limits are significantly improved by the addition of low concentrations of salts to the spray solvent.     

Rapid in situ detection of alkaloids in plant tissue under ambient conditions using desorption electrospray ionization

Desorption electrospray ionization (DESI) mass spectrometry is applied to the in situ detection of alkaloids in the tissue of poison hemlock (Conium maculatum), jimsonweed (Datura stramonium) and deadly nightshade (Atropa belladonna). The experiment is carried out by electrospraying micro-droplets of solvent onto native or freshly-cut plant tissue surfaces. No sample preparation is required and the mass spectra are recorded under ambient conditions, in times of a few seconds. The impact of the sprayed droplets on the surface produces gaseous ions from organic compounds originally present in the plant tissue. The effects of operating parameters, including the electrospray high voltage, heated capillary temperature, the solvent infusion rate and the carrier gas pressure on analytical performance are evaluated and optimized. Different types of plant material are analyzed including seeds, stems, leaves, roots and flowers. All the previously reported alkaloids have been detected in C. maculatum, while fifteen out of nineteen known alkaloids for D. stramonium and the principal alkaloids of A. belladonna were also identified. All identifications were confirmed by tandem mass spectrometry. Results obtained show similar mass spectra, number of alkaloids, and signal intensities to those obtained when extraction and separation processes are performed prior to mass spectrometric analysis. Evidence is provided that DESI ionization occurs by both a gas-phase ionization process and by a droplet pick-up mechanism. Quantitative precision of DESI is compared with conventional electrospray ionization mass spectrometry (after sample workup) and the RSD values for the same set of 25 dicotyledonous C. maculatum seeds (one half of each seed analyzed by ESI and the other by DESI) are 9.8% and 5.2%, respectively.     

Dynamic changes of gangliosides expression during the differentiation of embryonic and mesenchymal stem cells into neural cells

Stem cells are used for the investigation of developmental processes at both cellular and organism levels and offer tremendous potentials for clinical applications as an unlimited source for transplantation. Gangliosides, sialic acid-conjugated glycosphingolipids, play important regulatory roles in cell proliferation and differentiation. However, their expression patterns in stem cells and during neuronal differentiation are not known. Here, we investigated expression of gangliosides during the growth of mouse embryonic stem cells (mESCs), mesenchymal stem cells (MSCs) and differentiated neuronal cells by using high-performance thin-layer chromatography (HPTLC). Monosialoganglioside 1 (GM1) was expressed in mESCs and MSCs, while GM3 and GD3 were expressed in embryonic bodies. In the 9-day old differentiated neuronal cells from mESCs cells and MSCs, GM1 and GT1b were expressed. Results from immunostaining were consistent with those observed by HPTLC assay. These suggest that gangliosides are specifically expressed according to differentiation of mESCs and MSCs into neuronal cells and expressional difference of gangliosides may be a useful marker to identify differentiation of mESCs and MSCs into neuronal cells.     

Combination treatment with 2-methoxyestradiol overcomes bortezomib resistance of multiple myeloma cells

Bortezomib is a proteasome inhibitor used for the treatment of relapsed/refractory multiple myeloma (MM). However, intrinsic and acquired resistance to bortezomib has already been observed in MM patients. In a previous report, we demonstrated that changes in the expression of mitochondrial genes lead to changes in mitochondrial activity and bortezomib susceptibility or resistance, and their combined effects contribute to the differential sensitivity or resistance of MM cells to bortezomib. Here we report that the combination treatment of bortezomib and 2-methoxyestradiol (2ME), a natural estrogen metabolite, induces mitochondria-mediated apoptotic cell death of bortezomib-resistant MM KMS20 cells via mitochondrial reactive oxygen species (ROS) overproduction. Bortezomib plus 2ME treatment induces a higher level of cell death compared with treatment with bortezomib alone and increases mitochondrial ROS and Ca²⁺ levels in KMS20 cells. Pretreatment with the antioxidant N-acetyl-L-cysteine scavenges mitochondrial ROS and decreases cell death after treatment with bortezomib plus 2ME in KMS20 cells. Moreover, we observed that treatment with bortezomib plus 2ME maintains the activation of c-Jun N-terminal kinase (JNK) and mitogen-activated protein kinase kinase kinase 4/7 (MKK4/7). Collectively, combination treatment with bortezomib and 2ME induces cell death via JNK-MKK4/7 activation by overproduction of mitochondrial ROS. Therefore, combination therapy with specific mitochondrial-targeting drugs may prove useful to the development of novel strategies for the treatment of bortezomib-resistant MM patients.     

Electrical,Optical, and Structural Properties of SnO2: F Films as a Function of Fluoride Precursor Concentration and Temperature

Atmospheric pressure chemical vapor deposition (APCVD) employing the precursor system of tin tetrachloride, ethyl formate, and 2,2,2‐trifluoroethyl trifluoroacetate vapors that were transported to hot glass substrates to deposit fluorine doped tin dioxide thin films. The system is optimized with respect to the substrate deposition temperature and to the amount of fluoride added to the precursor stream and the resultant structural, electrical and optical properties compared. Increasing the substrate temperature from 360 °C to 610 °C resulted in an approximately linear increase in thickness of the tin dioxide films. However, the resistivity decreased from 1.8 × 10^–2 Ω · cm at 360 °C to a minimum of 5.9 × 10^–4 Ω · cm at 560 °C and increased to 9.4 × 10^–4 Ω · cm at 610 °C. While maintaining a substrate temperature of 560 °C different amounts of fluorine precursor was introduced into the carrier stream, from 0 mL · h^–1 to 5 mL · h^–1, resulting in a decrease in resistivity (ρ) from 5.3 × 10^–2 Ω · cm at 0 mL · h^–1 to a minimum of 5.9 × 10^–4 Ω · cm at 2 mL · h^–1 and then increased to 1.0 × 10^–3 Ω · cm at 5 mL · h^–1. As the amount of fluoride is increased a concommittent increase in carrier concentration results until the point of overdoping the film produces an increase in scattering sites that increases resistivity. Best films were deposited at 560 °C and when the fluoride precursor flow rate was 2 mL · h^–1.     

Reaction of Aziridinones with Thiourea: A Novel Synthesis of Specifically Substituted Glycocyamidines and Hydantoins

The reaction of aziridinones with thiourea produces glycocyamidines bearing substituents at positions 1 and 5, which have been converted into hydantoins.