Electrospray ionization mass spectrometric study of purine base-cisplatin complexes

By mixing cisplatin (cis-diamminedichloroplatinum(II)) with purine base the following ions have been obtained under electrospray ionization conditions: [A+Pt(NH3)2 Cl]+, [A+PtNH3Cl]+, [G+Pt(NH3)2 Cl]+ and [G+PtNH3)Cl]+. Their collision-induced dissociation led to the loss of NH3 and HCl and formation of the protonated base. The last process is strongly favoured for adenine over guanine. It confirms that, analogously as for DNA, formation of the guanine-cisplatin complex is favoured over that of the adenine complex and, as a consequence, it suggests that the mass spectrometric study of nucleic base complexes with platinum may provide some information on the interactions of DNA with other platinum drugs. The loss of NH3 accompanied by that of CO from the guanine ring has experimentally confirmed the presence of a strong hydrogen bond between the NH3 molecule and the O=C6 moiety of guanine found by theoretical calculations.     

Manipulating 2D metal-organic networks via ligand control

High-resolution scanning tunneling microscopy has revealed how ligand control can be successfully employed to eliminate isomeric phases and defects in 2D coordination networks that are self-assembled at a surface support by replacing symmetric dicarboxylato linker ligands to dissymmetric carboxylpyridyl linker ligands.     

Three dimensional k-space trajectory design using genetic algorithms

Image quality and total scan time in MRI are determined in large part by the trajectory employed to sample the Fourier space. Each trajectory has different properties like coverage of k-space, scan time, sensitivity to off-resonance conditions, etc. These properties are often contradictory, therefore a universal optimal trajectory does not exist and ultimately, it will depend on the image characteristics sought. Most trajectories used today are designed based on intuition and k-space analysis more than with optimization methods. This work presents a 3D k-space trajectory design method based on Genetic Algorithm optimization. Genetic Algorithms have been chosen because they are particularly good for searching large solution spaces. They emulate the natural evolutionary process allowing better offsprings to survive. The objective function searches the maximum of the trajectory's k-space coverage subject to hardware constraints for a fixed scanning time using the trajectory's torsion as its optimization variable.The method proved to be effective for generating k-space trajectories. They are compared with well-established trajectories. The results of simulated experiments show that they can be appropriate for image acquisition under certain special conditions, like off-resonance and undersampling. This design method can be extended to include other objective functions for different behaviors.     

A novel bis(imino)amine ligand as a result of acetonitrile coupling with the diiodides of Dy(II) and Tm(II)

Complexes of Dy(III) and Tm(III) with novel 1,1'-bis(iminoethyl)ethylamine ligands, [{(HN=CMe)2MeCNH2}Ln(MeCN)6]I3, were obtained by the reactions of LnI2 (Ln = Dy(II), Tm(II)) with acetonitrile.     

High-throughput investigation and characterization of cobalt carboxy phosphonates

High-throughput methods have been employed to study the system Co(2+)/(H(2)O(3)PCH(2))(2)NCH(2)C(6)H(4)COOH/NaOH in detail. The use of the phosphonocarboxylic acid (H(2)O(3)PCH(2))(2)NCH(2)C(6)H(4)COOH has led to several new cobalt carboxyaryl phosphonates under hydrothermal conditions. In addition to the effect of the pH of the starting mixture, the influence of the counterions of the cobalt salts on the product formation was investigated. Thus, reaction trends as well as fields of formation could be identified. Four new compounds Co(2)[(O(3)PCH(2))(2)NCH(2)C(6)H(4)COOH].H(2)O (1), Co[(O(3)PCH(2))(OCH)NCH(2)C(6)H(4)COOH].H(2)O (2), Co[H(2)(O(3)PCH(2))(2)NCH(2)C(6)H(4)COOH] (3), and [Co(2)(O(3)PCH(2))(2)NCH(2)C(6)H(4)COOH].3.5H(2)O (4) were obtained, and compounds 1 and 2 could be isolated as single crystals suitable for single-crystal X-ray diffraction. The counterions of the cobalt salts have an influence on the structure of the resulting compounds. This is due to the effect on the initial pH as well as the possibility of the counterions to take part in redox reactions. Compounds 1 and 4 are formed under more basic conditions, and the phosphonic acid group is fully deprotonated. The structure of 1 is a rare example of the family of inorganic-organic hybrid materials with iminobis(methylphosphonic acid) units wherein the nitrogen coordinates to the metal center. Compound 2 is the result of an in situ oxidation of one of the P-C bonds; the organic building unit is stabilized by complexation of the cobalt ion. On the basis of spectroscopic, thermogravimetric, elemental chemical analysis, and EDX-analysis data, compound 3 has been characterized as Co[H(2)(O(3)PCH(2))(2)NCH(2)C(6)H(4)COOH] and compound 4 as [Co(2)(O(3)PCH(2))(2)NCH(2)C(6)H(4)COOH].3.5H(2)O. X-ray powder diffraction and IR-spectroscopic studies show that thermal treatment of 4 leads to the title compound 1. This transformation is accompanied by a change of color from pink to deep blue.     

A skew normal dilation on the numerical range of an operator

Simple facts about the Poincaré-Neumann double layer potential are used in the construction of a normal dilation, on the numerical range of an arbitrary Hilbert space operator. Recent and old ideas in the theory of the numerical range are unified by this framework. A couple of mapping results for the numerical range are derived.Revised version: 15 July 2002First author partially supported by the National Science Foundation Grant DMS 0100367, Second author supported by STINT, The Swedish Foundation for International Cooperation in Research and Higher Education.     

Frequency response study of the dynamics of the platinum catalyzed interconversion of methylcyclohexane, toluene, and hydrogen near equilibrium

The dynamics of the platinum catalyzed interconversion of methylcyclohexane, toluene, and hydrogen near equilibrium were investigated in a closed reactor system by a frequency response method at temperatures in the range of 433 to 473 K and at total pressures in the vicinity of 80 to 110 Torr. The gas phase in contact with the platinum catalyst was always hydrogen-rich, with hydrogen to hydrocarbon mole ratios maintained in the range of 3.2 to 4.6. The frequency response method utilized small perturbations (lower than 1%) of the volume of the system, with measurements of the total pressure being used to determine the response of the system. The range of perturbation frequencies investigated was approximately 0.002 to 3 Hz (0.013 to 19 rad s(-1)). The experiments revealed two characteristic relaxation frequencies that are associated with the dynamics of the interconversion. The dynamics of the system are interpreted in terms of a simple two-step interconversion sequence with the aid of a phenomenological frequency response theory formulated in terms of relaxation frequencies of the steps and equilibrium properties of the system. It is concluded that one of the steps, a toluene adsorption-desorption step, is much slower than the other, a step involving the interconversion of the gas-phase methylcyclohexane and chemisorbed toluene that releases or consumes hydrogen in the process.     

Template-directed olefin cross metathesis

[reaction: see text] A template containing two secondary dialkylammonium ion recognition sites for encirclement by olefin-bearing dibenzo[24]crown-8 derivatives has been used to promote olefin cross metatheses with ruthenium-alkylidene catalysts. For monoolefin monomers, the rates of metatheses and yields of the dimers are both amplified in the presence of the template. Likewise, for a diolefin monomer, the yield of the dimer is enhanced in the presence of the template under conditions where higher oligomers are not formed.     

Nuclear moments of neutron deficient iridium isotopes from laser spectroscopy

Laser spectroscopy measurements have been performed on neutron deficient iridium isotopes. The hyperfine structure and isotope shift of the optical Ir I transition 5d⁷6s^{2 4}F_9/2 → 5d⁷6s6p ⁶F_11/2 at 351.5 nm have been studied for the ^182–189Ir, and ^191,193Ir isotopes. The nuclear magnetic and quadrupole moments were obtained from the HFS measurements and the changes of the mean square charge radii from the IS measurements. A large mean square charge radius change between ¹⁸⁷Ir and ¹⁸⁶Ir and between and has been observed. This revised version was published online in August 2006 with corrections to the Cover Date.