A new quantitative thermospray LC-MS method for nicotine and its metabolites in biological fluids

A rapid thermospray liquid chromatography-mass spectrometry (TSP LC-MS) method is described for the simultaneous determination of nicotine and 17 of its metabolites. Chemical ionization of nicotine and its metabolites separated by reversed-phase HPLC is achieved by postcolumn addition of ammonium acetate buffer with the filament of the ion source turned off. Quantification is accomplished by selectively monitoring the unique protonated molecular ion of each metabolite. Trideuterated cotinine serves as an internal standard. Linear responses for cotinine, demethylcotinine, and trans-3'-hydroxycotinine were observed over a concentration range of 20-8000 ng/mL, and 80-8000 ng/ml for nicotine and nicotine-1'-N-oxide. Of the 17 metabolites examined, only nicotine, cotinine, demethylcotinine, and trans-3'-hydroxycotinine were detected in smokers' urine.     

Observation of a rectangular columnar phase in a DNA-calcium-zwitterionic lipid complex

In the presence of calcium, DNA and unilamellar liposomes of the zwitterionic lipid DPPC form a complex in which DNA strands are embedded between a lamellar phase of DPPC. In some complexes, in-plane alignment of the DNA strands occurs, where a DNA-DNA interaxial distance can be measured using small-angle X-ray scattering. Here we report a higher level of DNA organization, with a rectangular columnar phase of DNA identified within this complex structure. This observation is important in view of recent interests in creating new synthetic systems at the interface of biology.     

Substitution-Inert Metal Complex Mobile Phases in Non-Suppressed Cation Chromatography

Substitution-inert metal complexes, [Co(edda)(H₂O)₂]⁺, (Co(edda)(en)]⁺, [Co(edda)(dmen)]⁺, [Co(en)₂-(gly)]²⁺, [Co(en)₂(acac)]²⁺, and [Co(trien)(gly)]²⁺ in their nitrate salt solutions are used as eluents in nonsuppressed cation chromatography (where edda = ethylenediamine-N,N′-diacetic acid, en = ethylenediamine, dmen = N,N′-dime-thylethylenediamine, gly = glycine, acac = acetylacetone, and trien = triethylenetetraamine). It is found that all the mono- and di-valent charged complexes can be used to separate alkali and alkaline earth metal cations, respectively. The separations for monovalent cations are sometimes comparable to those using ultrapure HNO₃ solutions. However, the divalent Ca²⁺ and Sr²⁺ ions cannot be resolved using the metal complex eluents. On the other hand, a selected, direct non-suppressed IC separation of zinc(II) and cadmium(II) ions is demonstrated for the first time using a substitution-inert metal complex eluent and a conductivity detector. Comparisons of these eluents with those reported previously, i. e. HNO₃ and ethylenediammonium salt solution are made and explanations are proposed to account for the different selectivities observed where possible. The future development of this technique is also briefly discussed.     

EPR studies on the thiophenodithiazolyl radical, C4H2S3N

Selective chlorination of thiophene-2,3-dithiol with SO(2)Cl(2) generates the corresponding sulfenyl chloride, 2,3-C(4)H(2)S(SCl)(2). Subsequent condensation with Me(3)SiN(3) yields the thiophenodithiazolylium salt [C(4)H(2)S(3)N]Cl, [TDTA]Cl. The structure of the cation, TDTA+, was established by X-ray diffraction as both its AsF(6)(-) and HSO(4)(-) salts. Reduction of [TDTA]Cl with Ag powder yields the radical TDTA* which was characterised by X- and Q-band (9 and 34 GHz) EPR and ENDOR studies. The spin density distributions estimated from the EPR/ENDOR measurements were found to be in very good agreement with those determined by DFT (B3LYP/6-31G*) indicating that ca 10% of the spin density is delocalised onto the thiophene ring. Comparison of the spin density distributions in TDTA* and the isoelectronic trithiatriazapentalenyl radical C(2)S(3)N(3), TTTA*, indicates that replacement of N by C-H leads to a localisation of the spin density on the dithiazolyl ring.     

Integration of quantitative DCE-MRI and ADC mapping to monitor treatment response in human breast cancer: initial results

PURPOSE: The objective of this study was to assess changes in the water apparent diffusion coefficient (ADC) and in pharmacokinetic parameters obtained from the fast-exchange regime (FXR) modeling of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) during neoadjuvant chemotherapy in breast cancer. MATERIALS AND METHODS: Eleven patients with locally advanced breast cancer underwent MRI examination prior to and after chemotherapy but prior to surgery. A 1.5-T scanner was used to obtain T1, ADC and DCE-MRI data. DCE-MRI data were analyzed by the FXR model returning estimates of K(trans) (volume transfer constant), v(e) (extravascular extracellular volume fraction) and tau(i) (average intracellular water lifetime). Histogram and correlation analyses assessed parameter changes post-treatment. RESULTS: Significant (P < .05) changes or trends towards significance (P < .10) were seen in all parameters except tau(i), although there was qualitative reduction in tau(i) values post-treatment. In particular, there was reduction (P < .035) in voxels with K(trans) values in the range 0.2-0.5 min(-1) and a decrease (P < .05) in voxels with ADC values in the range 0.99 x 10(-3) to 1.35 x 10(-3) mm2/s. ADC and v(e) were negatively correlated (r = -.60, P < .02). Parameters sensitive to water distribution and geometry (T(1), v(e), tau(i) and ADC) correlated with a multivariable linear regression model. CONCLUSION: The analysis presented here is sensitive to longitudinal changes in breast tumor status; K(trans) and ADC are most sensitive to these changes. Relationships between parameters provide information on water distribution and geometry in the tumor environment.     

Self-injection length in La0.7Ca0.3MnO3-YBa2Cu3O7-δ ferromagnet-superconductor multilayer thin films

We have carried out extensive studies on the self-injection problem in barrierless heterojunctions between La_0.7Ca_0.3MnO₃ (LCMO) and YBa₂Cu₃O_7-δ (YBCO) thin films. The heterojunctions were formed in situ by sequentially growing LCMO and YBCO films on 〈100〉 LaAlO₃ (LAO) substrate using a pulsed laser deposition (PLD) system. YBCO micro-bridges with 64 μm width were patterned both on the LAO (control) and LCMO side of the substrate. Critical current, I _c, was measured at 77 K on both the control side as well as the LCMO side for different YBCO film thickness. It was observed that while the control side showed a J _c of ∼ 2 × 10⁶ A/cm², the LCMO side showed about half the value for the same thickness (1800 ?). The difference in J _c indicates that a certain thickness of YBCO has become ‘effectively’ normal due to self-injection. From the measurement of J _c at two different thicknesses (1800 ? and 1500 ?) of YBCO films both on the LAO as well as the LCMO side, the value of self-injection length (at 77 K) was estimated to be ∼ 900 ?. To the authors’ best knowledge, this is the first time that self-injection length has been quantified. A control experiment carried out with LaNiO₃ deposited by PLD on YBCO did not show any evidence of self-injection.