Erratum to: Identification of a new source of interference leached from polypropylene tubes in mass-selective analysis

An interference leached from polypropylene tubes was identified to be a sulfoxide oxidative product of didodecyl 3,3′-thiodipropionate (DDTDP) that is used to prevent oxidative degradation of synthetic polymers. A sulfone oxidative product of DDTDP leached from the polypropylene tubes was also observed. The interfering compounds were isolated by LC and characterized using time-of-flight mass spectrometry and NMR. Authentic sulfoxide and sulfone products of DDTDP were also prepared by reacting DDTDP with hydrogen peroxide reaching an unequivocal structural assignment. In conclusion, when analytes of interest are solubilized in predominantly organic solvents and kept in polypropylene containers, the possibility of contamination from leached chemicals should be taken into account.     

Identification of a new source of interference leached from polypropylene tubes in mass-selective analysis

An interference leached from polypropylene tubes was identified to be a sulfoxide oxidative product of didodecyl 3,3'-thiodipropionate (DDTDP) that is used to prevent oxidative degradation of synthetic polymers. A sulfone oxidative product of DDTDP leached from the polypropylene tubes was also observed. The interfering compounds were isolated by LC and characterized using time-of-flight mass spectrometry and NMR. Authentic sulfoxide and sulfone products of DDTDP were also prepared by reacting DDTDP with hydrogen peroxide reaching an unequivocal structural assignment. In conclusion, when analytes of interest are solubilized in predominantly organic solvents and kept in polypropylene containers, the possibility of contamination from leached chemicals should be taken into account.     

(3 + 1) Assembly of three human telomeric repeats into an asymmetric dimeric G-quadruplex

We present an NMR study on the structure of a DNA fragment of the human telomere containing three guanine-tracts, d(GGGTTAGGGTTAGGGT). This sequence forms in Na(+) solution a unique asymmetric dimeric quadruplex, in which the G-tetrad core involves all three G-tracts of one strand and only the last 3'-end G-tract of the other strand. We show that a three-repeat human telomeric sequence can also associate with a single-repeat human telomeric sequence into a structure with the same topology that we name (3 + 1) quadruplex assembly. In this G-quadruplex assembly, there are one syn.syn.syn.anti and two anti.anti.anti.syn G-tetrads, two edgewise loops, three G-tracts oriented in one direction and the fourth oriented in the opposite direction. We discuss the possible implications of the new folding topology for understanding the structure of telomeric DNA, including t-loop formation, and for targeting G-quadruplexes in the telomeres.     

E.S.R., magnetic, electronic and superoxide dismutase studies of imidazolate-bridged Cu(II)-Cu(II) complexes with ethylenediamine as capping ligand

X-band E.S.R., magnetic and electronic spectra of some imidazolate-bridged homometallic complexes [(en)2Cu-R-Im-Cu(en)2](ClO4)3 where en, ethylenediamine; R-ImH, R = H imidazole (ImH); if R = CH3, 2-methylimidazole (M-ImH) and if R = C2H5, 2-ethylimidazole (E-ImH), and mononuclear complexes [(en)Cu-dien](ClO4)2 and [(en)Cu-PMDT](ClO4)2 where dien, diethylenetriamine; PMDT, pentamethyldiethylenetriamine have been described. Superoxide dismutase (SOD) activity has also been measured and compared with earlier reported complexes. In frozen solution at 77 K, the spectra show axial symmetry with a d(x2-y2) ground state. Difference in lambda(max) between mononuclear and binuclear complexes was found to be approximately 65-75 nm. Magnetic susceptibility and E.S.R. spectral measurements for all these binuclear complexes revealed that the copper(II) ions are involved in antiferromagnetic exchange interactions propagated by the imidazolate bridge.     

Polychalcone derived from 8-acetoxyquinoline-5-aldehyde

Fries rearrangement of 8-acetoxyquinoline-5-aldehyde (aqa) in nitrobenzene using AlCl₃ as catalyst affords the polychalcone poly(8-hydroxy-5,7-quinolinylenecarbonylvinylene) (phqcv). Thephqcv samples were characterized by elemental analysis,ir spectroscopy, molecular weight, intrinsic viscosity andtga. Polymeric metal chelates of Cu²⁺, Fe³⁺, Co²⁺, Ni²⁺, Mn²⁺, Zn²⁺ and UO ₂ ²⁺ withphqcv polychalcone were prepared and characterized.     

Studies of copper(II) chelates ofo-hydroxyacetophenone and its substituted derivatives in dioxane-water mixtures

Summary The interactions of Cu^II witho-hydroxyacetophenone (OHA) and its halogeno- and nitro-substituted derivatives were investigated potentiometrically in dioxane-water mixtures by the Calvin-Bjerrum titration technique at 25° C and ionic strength =0.1 M (NaClO₄). All the ligands form 11 and 12 chelates with Cu^II.The variations of pK with mole fraction of dioxane and 1/D were almost linear. Linearity was observed in the plots of log K₁/logK₂ versus pK, and the magnitudes of slopes led to the conclusion that -donation is: (i) strong in aqueous medium and decreases with the increase in dioxane content in 11 chelates, and (ii) weak and does not change with dioxane, in 12 chelates.     

Visible and near-infrared electronic transitions in NCl and NBr

The reactions of mixtures of halogen atoms (F + (Cl or Br)) with molecular azides produce banded emissions in the visible and near-infrared regions of the spectrum. The observed features correspond to b¹Σ⁺ → X³Σ^? and a¹Δ → X³Σ^? transitions, respectively, in NCl and NBr. The data obtained represent the first spectroscopic observation of the a¹Δ states of these molecules. The molecular constants of the a¹Δ states were determined to have the following values:

     

949.

Thermal emission of pions in antiproton-proton annihilation at 12 GeV/c     

G. W. van Apeldoorn  S. Barshay  D. Harting  D. J. Holthuizen  P. G. Kuijer  B. J. Pijlgroms  V. Karimäki  R. Kimumem  M. Korkea-aho  P. Johnson  P. Michaelides  Ch. Michaelidou  D. G. Patel 《Zeitschrift fur Physik C Particles and Fields》1981,7(3):235-239

Using data of \(\bar pp\) annihilation at 12 GeV/c we have found that centrally-emitted pions follow a thermal energy spectrum with an inclusive temperature of 111±2 MeV, the same as has been found for pions produced in πp collisions at 16 GeV/c. An analysis of individual high-multiplicity events to search for fluctuations in the temperature parameter on an event-byevent basis has been made, using two different methods. We obtained the value 0.18±0.02 for the relative dispersion of the temperature fluctuations.     

950.

Mononuclear and long-range single-bridged binuclear complexes of oxovanadium(IV) involving conjugated heterocyclic nitrogen base and heterocyclic β-diketones     

Bharat T. Thaker  Jayshree Lekhadia  Ashwin Patel  Purnima Thaker 《Transition Metal Chemistry》1994,19(6):623-631

Summary Binuclear complexes of OV^IV have been prepared by reacting aromatic diamines with mixed-ligand (mononuclear) complexes of the type [(diamine), VO(PmAcp or PmbzP)], where (diamine) = 2,2-bipyridine or 1,10-phenanthroline, and PmAcp or PmbzP heterocyclic -diketone ligands = 1-phenyl-3-methyl-4-acetyl or 4-benzoyl-2-pyrazolin-5-one. 2,6-Diaminopyridine orm-phenylenediamine condenses with the MeCO or PhCO groups of PmAcp and PmbzP on two complex molecules, thus bridging the two VO^II centres. The complexes have been characterized by electronic, i.r. and e.s.r. spectra, magnetic measurements, thermogravimetry, conductometry and microanalysis. The magnetic moments and the order of antiferromagnetism are explained on the basis of delocalized -orbitals, orientation of the metal orbitals and the bridging Schiff base. The metal-ligand bond is covalent.     

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	NCl	NBr
$\text{ν}{}_{\mathrm{e}}$	9260 ± 10 cm?1	9226 ± 10 cm?1
$\text{ω}{}_{\mathrm{e}}$	904 ± 6 cm?1	763 ± 4 cm?1
$\text{ω}{}_{\mathrm{e}}\text{x}{}_{\mathrm{e}}$	4.7 ± 1.2 cm?1	2.4 ± 1.6 cm?1

Thermal emission of pions in antiproton-proton annihilation at 12 GeV/c

Using data of \(\bar pp\) annihilation at 12 GeV/c we have found that centrally-emitted pions follow a thermal energy spectrum with an inclusive temperature of 111±2 MeV, the same as has been found for pions produced in πp collisions at 16 GeV/c. An analysis of individual high-multiplicity events to search for fluctuations in the temperature parameter on an event-byevent basis has been made, using two different methods. We obtained the value 0.18±0.02 for the relative dispersion of the temperature fluctuations.     

Mononuclear and long-range single-bridged binuclear complexes of oxovanadium(IV) involving conjugated heterocyclic nitrogen base and heterocyclic β-diketones

Summary Binuclear complexes of OV^IV have been prepared by reacting aromatic diamines with mixed-ligand (mononuclear) complexes of the type [(diamine), VO(PmAcp or PmbzP)], where (diamine) = 2,2-bipyridine or 1,10-phenanthroline, and PmAcp or PmbzP heterocyclic -diketone ligands = 1-phenyl-3-methyl-4-acetyl or 4-benzoyl-2-pyrazolin-5-one. 2,6-Diaminopyridine orm-phenylenediamine condenses with the MeCO or PhCO groups of PmAcp and PmbzP on two complex molecules, thus bridging the two VO^II centres. The complexes have been characterized by electronic, i.r. and e.s.r. spectra, magnetic measurements, thermogravimetry, conductometry and microanalysis. The magnetic moments and the order of antiferromagnetism are explained on the basis of delocalized -orbitals, orientation of the metal orbitals and the bridging Schiff base. The metal-ligand bond is covalent.