Uncertainty in photometric analysis: a case study

A procedure for estimation of measurement uncertainty of photometric analysis based on the ISO GUM method is presented. Two variations of the procedure—for the calibration graph and the standard addition method, respectively—are discussed. The variations are based on mathematical models involving 64 and 80 input quantities, respectively. The uncertainty of the result strongly depends on changes in experimental details. These dependencies are explored for a practical example of determination of the iron content of aluminum. The importance of taking uncertainty from sample preparation into account in uncertainty estimation is stressed. The number of effective degrees of freedom is calculated and discussed. The examples are available as GUM Workbench files in the Electronic Supplementary Material.Electronic Supplementary Material  Supplementary material is available for this article at .

Syntheses and biological evaluation of vinblastine congeners

Sixty-two congeners of vinblastine (VLB), primarily with modifications of the piperidine ring in the carbomethoxycleavamine moiety of the binary alkaloid, were synthesized and evaluated for cytotoxicity against murine L1210 leukemia and RCC-2 rat colon cancer cells, and for their ability to inhibit polymerization of microtubular protein at < 10(-6) M, and for induction of spiralization of microtubular protein, and for microtubular disassembly at 10(-4) M concentrations. An ID50 range of >10(7) M concentrations was found for L1210 inhibition by these compounds, with the most active 1000x as potent as vinblastine.     

A charge transfer-type fluorescent molecular sensor that "lights up" in the visible upon hydrogen bond-assisted complexation of anions

A charge transfer-type fluorescent molecular sensor consisting of a bisamidopyridine receptor and two styryl base chromophores shows H(2)PO(4)(-) and acetate-enhanced fluorescence due to the conversion of weak intramolecular hydrogen bonds into strong ones in the host-guest ensemble.     

Methyl-perthiooxalate und deren Reaktion mit Ph3P

Methyl-perthiooxalates and their Reaction with Ph₃ O-Methyl-1,1-dithiooxalate reacts with d⁸ transition metal ions with the spontaneous formation of mononuclear perthio/dithiooxalate complexes [(i-dtoMe)M(ptoMe)] (M = Ni, Pd, Pt). The mass spectrometric fragmentation of this complexes is discussed. The spontaneous sulfur insertion can be reversed by reaction with Ph₃P. Following up reactions with different Ph₃P equivalents are investigated for the Ni^II compound. Beside the synthesis of the square planar mixed ligand complex [(Ph₃P)Ni(i-dtoMe)₂] a Ni^I complex was detected by EPR spectroscopy.     

Methylation of 5-Phenyl-1,4-benzodiazepin-2-one derivatives with N,N-dimethylformamide-dimethyl acetal

A novel method for N-methylation of the cyclic amide in the 1,4-benzodiazepine ring system is presented. Methods traditionally used involve treatment of the 1,4-benzodiazepinone anion with an alkyl halide. It has been demonstrated that these derivatives can be methylated on the amide nitrogen atom by use of dimethyl-formamide dimethyl acetal which acts as both reagent and solvent for the reaction.     

On the properties of some substituted α'-lithiated α(z), -butadienyl sulfides: cyclisations and rearrangements

The conditions for the preparation and cyclisation of the title compounds $\text{3}$ are described. The stability of the intermediate lithio-thiacyclohexenes $\text{4}$ is shown to depend on the reaction conditions and the substituents R¹-R⁴. The final products $\text{6}$, $\text{10}$ and $\text{7}$ arise from $\text{4}$ via a [1.4] sigmatropic rearrangement, a [1.3]prototropic shift followed by a [2.3] sigmatropic rearrangement, or the elimination of lithium methanethiolate respectively.     

The preparation of fluorescence-quenched probes for use in the characterization of human factor Xa substrate binding domains

The preparation and characterization by LCMS of a library of 55 fluorescence- quenched peptides is described. The peptides bear a terminal anthranilamide fluorophore and a penultimate 2,4-dinitrophenyl-L-lysine quencher, and will be used to probe the substrate binding domain of the human blood coagulation enzyme, factor Xa.     

Unusually high chemical compressibility of normally rigid type-I clathrate framework: synthesis and structural study of Sn(24)P(19.3)Br(x)I(8)(-)(x) solid solution, the prospective thermoelectric material

A novel tin phosphide bromide, Sn(24)P(19.3(2))Br(8), and Sn(24)P(19.3(2))Br(x)()I(8)(-)(x) (x = 0-8) solid solution have been prepared and structurally characterized. All compounds crystallize with the type-I clathrate structure in the cubic space group Pmn (No. 223). The clathrate framework of the title solid solution shows a remarkable chemical compressibility: the unit cell parameter drops from 10.954(1) to 10.820(1) A on going from x = 0 to x = 8, a feature that has never been observed for normally rigid clathrate frameworks. The chemical compressibility as well as non-Vegard dependence of the unit cell parameter upon the bromine content is attributed to the nonuniform distribution of the guest halogen atoms in the polyhedral cavities of the clathrate framework. The temperature-dependent structural study performed on Sn(24)P(19.3(2))Br(8) has shown that, in contrast to the chemical compressibility, the thermal compressibility (linear contraction) of the phase is similar to that observed for the Group 14 anionic clathrates. The tin phosphide bromide does not undergo phase transition down to 90 K, and the atomic displacement parameters for all atoms decrease linearly upon lowering the temperature. These linear dependencies have been used to assess such physical constants as Debye temperature, 220 K, and the lattice part of thermal conductivity, 0.7 W/(m K). Principal differences between the title compounds and the group 14 anionic clathrates are highlighted, and the prospects of creating new thermoelectric materials based on cationic clathrates are briefly discussed.     

Parallel direct SCF and gradient program for workstation clusters

A parallel direct SCF and gradient program for workstation clusters has been implemented on the basis of the ab initio program package TURBOMOLE. Applications on large molecular systems monitor an appreciable speedup in residence time. © John Wiley & Sons, Inc.     

The Ni-mediated cyclocarbonylation of allyl halides and alkynes made catalytic. Evidence supporting the involvement of pseudoradical Ni(i) species in the mechanism

We report here on a highly efficient catalytic method to synthesize intermolecularly the cyclopentane skeleton from starting products as simple as allyl halides, alkynes, and carbon monoxide under very mild reaction conditions by means of a substoichiometric amount of iron, acetone, and a catalytic amount of Ni(II) iodide.