Microscopic aspects of autoschizic cell death in human ovarian carcinoma (2774) cells following vitamin C, vitamin K3 or vitamin C:K3 treatment.

Human ovarian carcinoma cells (MDAH 2774) were treated with sodium ascorbate (VC), menadione (VK3), or with a VC:VK3 combination for 1 h and then studied using light microscopy (LM) and scanning (SEM) and transmission electron (TEM) microscopy. Plasma membrane damage (blisters and blebs, hairy aspect) results from vitamin C (VC) treatment, while cytoskeletal damage and self-morsellation are caused by vitamin K3 (VK3) treatment. VC:VK3-treated cells exhibit exacerbated injuries characteristic of both VC and VK3 treatment as well as a significant decrease in cell diameters from 20-35 microm for control cells to 7-12 microm for VC:VK3 treatment. Moreover, after a 1-h exposure to the vitamin combination, autoschizis (43%), apoptosis (3%), and oncosis (1.9%) are observed at the percentages indicated. All cellular changes associated with autoschizis observed with SEM were confirmed by LM and TEM observations and are consistent with cell death by autoschizis: decrease in cell size, cytoplasmic self-excisions, degradation of the nucleus and nucleolus without formation of apoptotic bodies and, ultimately, karyorrhexis and karyolysis. These results also suggest that the vitamin combination may find clinical use in the treatment of ovarian cancer.     

Non-localized ligand-to-metal charge transfer excited states in (Cp)2Ti(IV)(NCS)2

The bent d(0) titanium metallocene (Cp)(2)Ti(NCS)(2) exhibits an intense phosphorescence from a ligand-to-metal charge transfer triplet excited state at 77 K in an organic glass substrate and a poly(methyl methacrylate) plastic substrate. Quantum chemical calculations and spectroscopic studies show that the orbital parentage of this triplet state arises from the promotion of an electron from an essentially nonbonding symmetry adapted pi molecular orbital located on the NCS(-) ligands to a d(z)2-(y)2 orbital located on the Ti metal. Standard infrared spectroscopy of (Cp)(2)Ti(NCS)(2) in its ground electronic state at 77 K reveals a pair of closely spaced absorptions at (2072 cm(-1), 2038 cm(-1))(glass) and (2055 cm(-1), 2015 cm(-1))(plastic) that are assigned, respectively, to the symmetric and antisymmetric CN stretching modes of the two coordinated NCS(-) ligands. Low-temperature (77 K) time-resolved infrared spectroscopy that accesses the phosphorescing triplet excited state on the ns time scale shows an IR bleach that is coincident with the two ground state CN stretching bands and an associated grow-in of a pair of new IR bands at slightly lower energies (2059 cm(-1), 2013 cm(-1))(glass) and (2049 cm(-1), 1996 cm(-1))(plastic) that are assigned, respectively, to the symmetric and antisymmetric CN stretches in the emitting triplet state. These transient IR bands decay with virtually identical lifetimes to those observed for the phosphorescence decays when measured under identical experimental conditions. Singular value decomposition analysis of the time-resolved infrared data shows that the observed transient IR features arise from the same electronic manifold as measured through luminescence studies. The close similarity between the ground state and excited-state CN stretching bands in (Cp)(2)Ti(NCS)(2) indicates that symmetry breaking does not occur in forming the charge-transfer triplet excited-state manifold; i.e., electron density is withdrawn from a delocalized pi MO spread across both NCS(-) ligands. Calculations at several levels of theory reveal a delocalized ligand-to-metal charge transfer excited triplet manifold. These calculations closely reproduce the relative intensity ratios and frequencies of the symmetric and antisymmetric transient infrared vibrations in the CN region. This study is the first time-resolved infrared investigation of a ligand-to-metal charge-transfer excited state and the first to be performed at cryogenic temperatures in thin-film organic glass and plastic substrates.     

Displacement of Mn2+ from RNA by K+, Mg2+, neomycin B,and an arginine-rich peptide: indirect detection of nucleic acid/ligand interactions using phosphorus relaxation enhancement

We have developed a novel method to study the interactions of nucleic acids with cationic species. The method, called phosphorus relaxation enhancement (PhoRE), uses (1)H-detected (31)P NMR of exogenous probe ions to monitor changes in the equilibrium between free Mn(2+) and Mn(2+) bound to the RNA. To demonstrate the technique, we describe the interactions of four RNA molecules with metal ions (K(+) and Mg(2+)), a small molecule drug (neomycin b), and a cationic peptide (RSG1.2). In each case, cationic ligand binding caused Mn(2+) to be displaced from the RNA. Free Mn(2+) was determined from its effect on the T(2) NMR relaxation rate of either phosphite (HPO(3)(2-)) or methyl phosphite (MeOPH, CH(3)OP(H)O(2-)). Using this method, the effects of [RNA] as low as 1 microM could be measured in 20 min of accumulation using a low field (200 MHz) instrument without pulsed field gradients. Cation association behavior was sequence and [RNA] dependent. At low [K(+)], Mn(2+) association with each of the RNAs decreased with increasing [K(+)] until approximately 40 mM, where saturation was reached. While saturating K(+) displaced all the bound Mn(2+) from a 31-nucleotide poly-uridine (U(31)), Mn(2+) remained bound to each of three hairpin-forming sequences (A-site, RRE1, and RRE2), even at 150 mM K(+). Bound Mn(2+) was displaced from each of the hairpins by Mg(2+), allowing determination of Mg(2+) dissociation constants (K(d,Mg)) ranging from 50 to 500 microM, depending on the RNA sequence and [K(+)]. Both neomycin b and RSG1.2 displaced Mn(2+) upon binding the hairpins. At [RNA] approximately 3 microM, RRE1 bound a single equivalent of RSG1.2, whereas neither RRE2 nor A-site bound the peptide. These behaviors were confirmed by fluorescence polarization using TAMRA-labeled peptide. At 2.7 microM RNA, the A-site hairpin bound a single neomycin b molecule. The selectivity of RSG1.2 binding was greatly diminished at higher [RNA]. Similarly, each hairpin bound multiple equivalents of neomycin at the higher [RNA]. These results demonstrate the utility of the PhoRE method for characterizing metal binding behaviors of nucleic acids and for studying RNA/ligand interactions.     

Mass spectral fragmentation pattern of 4-carboxy-and 4-methoxycarbonyl-5-methyl(or phenyl)-2-aryl-2H-1,2,3-triazoles

4-Carboxy-5-methyl-2-aryl-2H-1,2,3-triazoles undergo considerable fragmentation on electron impact including loss of OH and H₂O from the molecular ions and rupture of the triazole ring. 4-Carboxy-5-phenyl-2-aryl-2H-1,2,3-triazoles, on the other hand, show no loss of H₂O from the molecular ions.     

A conformational analysis of the six isomers of thiobispyridine

The conformational behaviour of the six isomers of thiobispyridine has been investigated using ab initio STO-3G*//rigid-roto, STO-3G*//STO-3G* and 6–31G**//STO-3G* molecular orbital models. The analysis reveals both the importance of optimising critical structure parameters and the basis set dependence of calculated rotational barrier heights. The most reliable model (6–31G**//STO-3G*) clearly indicates that the minimum energy conformers are not planar and that energy barriers between 30–100 kJ mol^?1 restrict inter-conversion to planar structures, thereby preventing conjugation between the p-electrons of the sulfur atom and the π system of both pyridine rings. From the calculated barrier heights, two mechanisms can be employed to explain conformer interconversion about the C? S bond: a disrotatory one-ring flip or a conrotatory two-ring flip mechanism. Where comparisons can be made (eg. 2,2′-thiobispyridine), dipole moment calculations are shown to be in good agreement with experiment. Finally, of the six isomers, appropriately substituted 2,2′, 2,3′- and 2,4′-thiobispyridines are most prone to a Smiles rearrangment.     

Fluorescent and phosphorescent pyrimidine labels : α-Diketone derivatives of uracil and thymine

The syntheses of 1-(3,4-dioxopentyl)uracil (V), 1-(2,3-dioxobutyl)uracil (XIIa), 1-(2,3-dioxobutyl)-3-methyluracil (XIIb) and 1-(2,3-dioxobutyl)thymine (XIIc) are described. These are the first compounds to be prepared which have α-diketone functions attached to biologically important pyrimidines. Preparation of the dioxopentyluracil was by oximation of 1-(4-oxopentyl)uracil, and of the dioxobutyl compounds was by alkylation of the appropriate pyrimidine with the dimethoxy ketal of bromobiacetyl, followed by hydrolysis under special conditions. The characteristics of the absorption and emission spectra in various solvents are presented and discussed. Dioxopentyl uracil exhibits both phosphorescence and fluorescence at room temperature; the dioxobutyl pyrimidines are fluorescent but non-phosphorescent under the same conditions. The fluorescence quantum yields of all four compounds are about 0.2%, similar to those of biacetyl or 2,3-pentanedione.     

Mass spectral fragmentation pattern of 2,2′-Bipyridyls. Part IX. 6-Alkoxy-2,2′-bipyridyls

The mass spectral fragmentation patterns of 6-methoxy-, 6-ethoxy- and 6-propoxy-2,2 ′-bipyridyls are reported. The base peaks in the spectra of both the 6-methoxy and 6-ethoxy compounds are due to the M-lion of 6-methoxy-2,2′-bipyridyl, while the base peak with 6-propoxy-2,2- bipyridyl is due to a species formed by loss of C₃H₆ from the molecular ion.     

An Algebraic Characterization of Vacuum States in Minkowski Space. II. Continuity Aspects

An algebraic characterization of vacuum states in Minkowski space is given which relies on recently proposed conditions of geometric modular action and modular stability for algebras of observables associated with wedge-shaped regions. In contrast to previous work, continuity properties of these algebras are not assumed but derived from their inclusion structure. Moreover, a unique continuous unitary representation of spacetime translations is constructed from these data. Thus, the dynamics of relativistic quantum systems in Minkowski space is encoded in the observables and state and requires no prior assumption about any action of the spacetime symmetry group upon these quantities.     

Luminescence properties of Mn doped Zn2SiO4 phosphor films synthesized by combustion CVD

Zn₂SiO₄:Mn²⁺ phosphor films were successfully prepared by a novel combustion chemical vapor deposition (CCVD) method. In the CCVD process, a flammable solution, containing precursor materials, is atomized and sprayed through a specially designed nozzle and ignited to form a combustion flame. This enables crystallized films to be directly deposited onto a substrate in open-atmosphere with no post deposition heat treatment. SEM images indicated that the film deposited at 1200 °C consisted of densely packed particles with a fine grain size of several 100 nm. Strong Photoluminescence (PL) and cathodoluminescence (CL) intensities were observed with Zn₂SiO₄:Mn²⁺ samples deposited at a substrate temperature of 1200 °C exhibiting the best crystallinity and highest luminescence. The optimum doping level for films deposited using CCVD was found to be ∼4 mol% Mn²⁺ of starting concentration, with a maximum CL luminescence equivalent to 53% of the luminescence measured from a commercial powder phosphor. A relatively fast CL decay with life time about 0.6-0.7 ms was also observed from these films.