C∞ functions in infinite dimension and linear partial differential difference equations with constant coefficients

This work is closed to [2] where a dense linear subspace \(\mathbb{E}\) (E) of the space ?(E) of the Silva C ^∞ functions on E is defined; the dual of \(\mathbb{E}\) (E) is described via the Fourier transform by a Paley-Wiener-Schwartz theorem which is formulated exactly in the same way as in the finite dimensional case. Here we prove existence and approximation result for solutions of linear partial differential difference equations in \(\mathbb{E}\) (E) with constant coefficients. We also obtain a Hahn-Banach type extension theorem for some C^∞ functions defined on a closed subspace of a DFN space, which is analogous to a Boland’s result in the holomorphic case [1].     

The short N [bond] F bond in N(2)F(+) and how Pauli repulsion influences bond lengths. Theoretical study of N(2)X(+), NF(3)X(+), and NH(3)X(+) (X [double bond] F, H)

Exceptionally short N [bond] F bond distances of only 1.217 A (crystal) and 1.246 A (gas phase) have been reported for N(2)F(+), making it the shortest N [bond] F bond ever observed. To trace the origin of this structural phenomenon, we have analyzed the model systems N(2)X(+), NF(3)X(+), and NH(3)X(+) (X [double bond] F, H) using generalized gradient approximation density functional theory at BP86/TZ2P. In good agreement with experiment, the computations yield an extremely short N [bond] F bond for N(2)F(+): we find N [bond] F bond distances in N(2)F(+), NF(4)(+), and NH(3)F(+) of 1.245, 1.339, and 1.375 A, respectively. The N [bond] X bonding mechanisms are quantitatively analyzed in the framework of Kohn-Sham MO theory. At variance with the current hypothesis, reduced steric and other Pauli repulsion (of substituents or lone pairs at N with F) rather than the extent of s [bond] p hybridization of N (i.e., sp versus sp(3)) are responsible for the much shorter N [bond] F distance in N(2)F(+) compared to NF(4)(+). The results for our nitrogen compounds are furthermore discussed in the more general context of how bond lengths are determined by both bonding and repulsive orbital interactions.     

Stopped-flow Fourier transform infrared spectroscopy of nitromethane oxidation by the diiron(IV) intermediate of methane monooxygenase

The hydroxylase component (MMOH) of soluble methane monooxygenase from Methylococcus capsulatus (Bath) was reduced to the diiron(II) form and then allowed to react with dioxygen to generate the diiron(IV) intermediate Q in the first phase of a double-mixing stopped-flow experiment. CD3NO2 was then introduced in the second phase of the experiment, which was carried out in D2O at 25 degrees C. The kinetics of the reaction of the substrate with Q were monitored by stopped-flow Fourier transform infrared spectroscopy, observing the disappearance of the asymmetric NO2 bending vibration at 1548 cm-1. The data were fit to a single-exponential function, which yielded a kobs of 0.45 +/- 0.07 s-1. This result is in quantitative agreement with a kobs of 0.39 +/- 0.01 s-1 obtained by observing the disappearance of Q by double-mixing stopped-flow optical spectroscopy at its absorption maximum of 420 nm. These results provide for the first time direct monitoring of the hydroxylation of a methane-derived substrate in the MMOH reaction pathway and demonstrate that Q decay occurs concomitantly with substrate consumption.     

Tricarbonyl Complexes of Rhenium(I) with Acetylpyridine Benzoylhydrazone and Related Ligands

Novel rhenium(I) tricarbonyl complexes have been prepared by reactions of (Et₄N)₂[Re(CO)₃Br₃] with acetylpyridine benzoylhydrazone, Hapbhyd, di(2‐pyridyl)ketone benzoylhydrazone, Hpy₂bhyd, bis(2‐pyridine)ketone, py₂CO, and pyridinealdehyde terephtalaldehydebishydrazone, pytehyd. The ligands remain protonated when no supporting base is added and the following complexes have been isolated: [Re(CO)₃Br(Hapbhyd)], [Re(CO)₃Br(Hpy₂bhyd‐py, hyd)], [Re(CO)₃Br(Hpy₂bhyd‐py¹, py²)], [Re(CO)₃Br(py₂CO‐N, N)] and [Re(CO)₃Br(pytehyd)]. Addition of triethyl amine results in deprotonation of Hapbhyd and the formation of [Re(CO)₃(OH₂)(apbhyd)], whereas Hpy₂bhyd is hydrolysed and a rhenium complex with the monoanionic bis(2‐pyridyl)hydroxymethanolato ligand, {py₂C(OH)O}^‐, is formed. The same compound, [Re(CO)₃{py₂C(OH)O}], is obtained when triethyl amine and water are added to a mixture of (Et₄N)₂[Re(CO)₃Br₃] and py₂CO. The air‐stable products have been studied by spectroscopic methods and X‐ray crystallography.     

Force field for platinum binding to adenine

The antitumor drug cis-diamminedichloroplatinum(II) (cisplatin) binds preferentially to GpG and ApG sequences of DNA, forming N7,N7 intrastrand chelates. Molecular modeling of the intrastrand adducts have been handicapped, so far, by the lack of force-field data describing the Pt–guanine and Pt–adenine binding. We used ab initio calculations with relativistic pseudopotentials to evaluate three important parameters for the platinum–adenine model complex [Pt(NH₃)₃(Ade)]²⁺: (1) the force constant for the Pt? N7 bond bending out of the adenine plane; (2) the energy profile for the torsion about Pt? N7; (3) a set of fractional atomic charges that reproduce the ab initio potential for a number of space points placed around the adduct. A population analysis and comparative study on the tetrammine complex [Pt(NH₃)₄]²⁺ have shown that for platinum adenine is a better σ-donor than NH₃, but its capacity as a π-acceptor is weak. © 1993 John Wiley & Sons, Inc.     

Application of edta to direct graphite-furnace atomic absorption analysis for cadmium in sea water

A method is described for the direct determination of cadmium in undiluted sea water by graphite-furnace atomic absorption spectrometry. The addition of EDTA ( 1 mg ml^-1) reduces the temperature of atomization of cadmium to far below that of volatilization of other matrix components. The need for very careful temperature control and accurate background compensation is thus minimized. Sea water was analyzed by the method of standard additions. A detection limit of 0.01 μg l^-1, a sensitivity of 0.034 μg l^-1 and a precision of ±10% at the 0.05 μg l^-1 level were obtained for 20-μl injections.     

Oxidation of coordinated olefins: the reactions of Cl2 with trichloro(ehtylene)platinate(II)

The oxidation of [PtCl₃(C₂H₄)]- by Cl₂ in aqueous solution, to yield CH₂ClCH₂OH and [PtCl₄]^2-, has been shown to proceed through the following sequence of steps: [PtCl₃(C₂H₄)] Cl₂Cl [PtCl₅(CH₂CH₂Cl)]^2-$\text{H}{}_2\text{O}\text{(HCl)}$ [PtCl₅(CH₂CH₂OH)]^2- → [PtCl₄^2- + CH₂ClCH₂OHEach of the steps and intermediates in this mechanistic sequence has been identified and characterized.     

Synthesis and characterization of new polyamides derived from di(4-cyanophenyl)isosorbide

New optically active polyamides were synthesized according to two ways: using a microwave-assisted polycondensation of an optically active isosorbide-derived diacylchloride with different aromatic diamines in NMP and using interfacial polymerization from an isosorbide-derived diamine with different diacylchlorides. The polymers are obtained with inherent viscosities in the range from 0.11 to 1.05 dL/g. The DSC and TGA measurements clearly demonstrate the high thermal stability of these polymers when considering the range of the melting points from 200 °C to 300 °C and the absence of decomposition till 350 °C.     

Determination of deoxynivalenol in cereals and cereal products by immunoaffinity column cleanup with liquid chromatography: interlaboratory study

An interlaboratory study was performed on behalf of the UK Food Standards Agency to evaluate the effectiveness of an immunoaffinity column cleanup liquid chromatographic (LC) method for the determination of deoxynivalenol in a variety of cereals and cereal products at proposed European regulatory limits. The test portion was extracted with water. The sample extract was filtered a applied to an immunoaffinity column. After being washed with water, the deoxynivalenol was eluted with acetonitrile or methanol. Deoxynivalenol was quantitated by reversed-phase LC with UV determination. Samples of artificially contaminated wheat-flour, rice flour, oat flour, polenta, and wheat based breakfast cereal, naturally contaminated wheat flour, and blank (very low level) samples of each matrix were sent to 13 collaborators in 7 European countries. Participants were asked to spike test portions of all samples at a range of deoxynivalenol concentrations equivalent to 200-2000 ng/g deoxynivalenol. Average recoveries ranged from 78 to 87%. Based on results for 6 artificially contaminated samples (blind duplicates), the relative standard deviation for repeatability (RSDr) ranged from 3.1 to 14.1%, and the relative standard deviation for reproducibility (RSDR) ranged from 11.5 to 26.3%. The method showed acceptable within-laboratory and between-laboratory precision for all 5 matrixes, as evidenced by HorRat values < 1.3.     

Synthesis of 2′-Deoxy-5-(isothiazol-5-yl)uridine and Its Interaction with the HSV-1 Thymidine Kinase

2′-Deoxy-5-(isothiazol-5-yl)uridine ( 12 ) was synthesized starting from 2′-deoxy-5-iodouridine using a Pd-catalysed cross-coupling reaction with propiolaldehyde diethyl acetal followed by deprotection and ring closure using thiosulfate. 2′-Deoxyuridine 12 has a particular place among the 5-heteroaryl-substituted 2′-deoxyuridines in that it has a high affinity for herpes simplex virus type 1 (HSV-1)-encoded thymidine kinase (TK) without antiviral activity. Biochemical studies revealed that 12 is a substrate for viral TK. We further investigated the interaction of 12 with the HSV-1 thymidine kinase. The conformation of 12 in solution was established by NMR spectroscopy. The most stable conformer 12A has the S-atom of the isothiazole ring placed in the neighbourhood of the C(4)?O group of the pyrimidine moiety. The compound was docked in its most stable conformation in the active site of HSV-1 TK and subjected to energy minimization. This demonstrated that the isothiazole moiety binds in a cavity lined by the side chains of Tyr-132, Arg-163, Ala-167, and Ala-168 and that the C(3) atom of the isothiazole moiety is located in close proximity of the phenolic O-atom of Tyr-132 and the aliphatic part of the Arg-163 side chain.