Uncertainty calculation for calibrators of the IFCC HbA1c standardization network

Within the last decade, the IFCC HbA1c standardization network has established the metrologically highest reference measurement procedure for HbA1c testing. Based on this procedure, reference calibrators are produced which in turn provide the starting point for the standardization of the manufactures routine HbA1c assays. According to the IVD directive, the uncertainty of the reference calibrators must be calculated and reported together with their assigned values. Within this article, we elaborate the uncertainty calculation according to GUM (guide to the expression of uncertainty in measurement) in detail. Finally, the results are validated by a simulation study.     

Synthesis and ligand properties of thianthrenophane

Thianthrenophane 1 has a cavity which offers enough room to potentially enable endohedral coordination to small ions or molecules. For the complexation of silver(I) perchlorate the complex stability constants of 1 logK1=5.45 +/- 0.13 and of thianthrene logK2=9.16 +/- 0.10 were determined by UV/Vis titration. Single competition transport experiments with ten metal salts demonstrate a very high selectivity of 1 as a carrier for silver(I) and a distinctly higher transport rate compared to carriers such as thianthrene and 1,4,8,11-tetrathiacyclotetradecane (14-ane-S4). Although the X-ray crystal structure analysis of the polymeric [Ag(1)]ClO4.(dioxane)7 complex shows an exohedral coordination to silver(I) we suggest that the formation of an endohedral [Ag(1)]+ complex is the explanation for the unusual carrier selectivity of silver(I) by 1 in bulk liquid membrane.     

Site-specific solvation determined by intermolecular nuclear Overhauser effect--measurements and molecular dynamics

Site-specific solvation has been determined by intermolecular NOE measurements between solvent and solute. The experimental effect is shown on the four compounds 2-butanol, L-alanyl-L-tryptophan (Ala-Trp), adenosine and the disodium salt of adenosine 5'-monophosphate (5'-AMP) in the two solvents water and dimethyl sulfoxide (DMSO). The strength of NOE transfer correlates with the average distribution of solvent molecules around the corresponding solvation sites represented by the number of solvent molecules in a first solvation sphere, which can be obtained from molecular dynamics simulations in water. Saturation transfer between exchanging protons explains some deviations from this correlation. The NOE transfer measurements provide information on specific solute-solvent interactions and contribute to a better understanding of solvation phenomena. On the basis of a distinct relationship between steric solvation hindrance and the strength of NOE transfer, the application of such measurements for conformational analysis has been demonstrated for the first time.     

Wetting and self-cleaning properties of artificial superhydrophobic surfaces

The wetting and the self-cleaning properties (the latter is often called the "Lotus-Effect") of three types of superhydrophobic surfaces have been investigated: silicon wafer specimens with different regular arrays of spikes hydrophobized by chemical treatment, replicates of water-repellent leaves of plants, and commercially available metal foils which were additionally hydrophobized by means of a fluorinated agent. Water droplets rolled off easily from those silicon samples which had a microstructure consisting of rather slender spikes with narrow pitches. Such samples could be cleaned almost completely from artificial particulate contaminations by a fog consisting of water droplets (diameter range, 8-20 microm). Some metal foils and some replicates had two levels of roughening. Because of this, a complete removal of all particles was not possible using artificial fog. However, water drops with some amount of kinetic impact energy were able to clean these surfaces perfectly. A substrate where pronounced structures in the range below 5 microm were lacking could not be cleaned by means of fog because this treatment resulted in a continuous water film on the samples.     

Asymmetric synthesis of α-hydroxy-esters via ester enolates

3-Phenylpropionates of chiral alcohols derived from (+)-camphor are oxidized by Mo0₅· Py·HMPT (MoOPH) with high diastereoselectivity.     

Electronic ground states of the V2O4+/0/- species from multireference correlation and density functional studies

The molecular and electronic structures of the V2O4+/0/- species are examined by multireference averaged coupled-pair functional (MR-ACPF) and density functional B3LYP calculations. For all three species, new conformers have been found. Shallow potential energy curves imply high mobility of the oxygen atoms in the neutral and anionic species for which antiferromagnetic coupling of the weakly interacting 3dV electrons is found. Good agreement between the MR-ACPF and B3LYP results for the molecular structures and the relative energies of states with different spin multiplicity, as well as for the ionization energy and electron affinity, is observed. For the computation of the height of the transition barriers between different conformers elaborated MR-ACPF calculations are required.     

Selektive Reaktionen an Cytochalasin D

In connection with the total synthesis of cytochalasans the cleavage of the macrocyclic system of cytochalasin D ( 3 ) was studied in order to gain useful relay compounds. Selective scission of the double bond in 19-position was achieved by controlled ozonolysis leading to compound 7 (Scheme 1). Treatment of 3 with OsO₄ and subsequent acetylation gave the tetraacetoxy- and diacetoxy derivatives 8 and 9 , respectively. Sharpless epoxidation of 3 yielded the mono-, di- and the two epimeric triepoxides 10 , 11 , 12 , and 13 , respectively. Further studies concerned the isomerization of the 6(12)-double bond to 6(7)-double bond by an allylic rearrangement. Treatment of 3 with mesylchloride and triethylamine led to 12-hydroxy-, 12-mesyloxy- and 12-chlorozygosporin ( 14 , 16 , and 17 , resp.) (see Scheme 2). Epoxidation of 14 gave a mixture of the two epimeric 6,7-epoxides 21 and 23. Zn-reduction of 18 (the corresponding bromide of 17 ) led to zygosporin G ( 20 ). In order to convert a carbocyclic cytochalasan into a macrocyclic derivative, 3 was converted to 32 (Scheme 2). Treatment of 32 with H₂O₂ in acetic acid/chloroform or with phenylselenylperacid/H₂O₂ yielded the enollactone 33 . Finally, 17,18-secocytochalasin D derivatives were prepared for the synthesis of unnatural analogs of macrolidic cytochalasans. The diol 26 was converted into the ketoaldehydes 38 and 40 and to the corresponding keto-acids 43 and 44 (Scheme 3), which were reduced to the ω-hydroxycarboxylic acids 45 – 48. Treatment of 47 with 2,2^/-dipyridyldisulfide/triphenylphosphine/xylene gave probably the lactone 50 .     

Relation between different variants of the generalized Douglas-Kroll transformation through sixth order

Wolf et al. have recently investigated a generalized Douglas-Kroll transformation. From a general class of unitary transformations that can be used in the Douglas-Kroll transformation, they pick one which is supposed to give, at a given order, an optimal transformed Dirac Hamiltonian. Results were presented through the fifth order. However, no data were given to demonstrate to which extent the so-called "optimal" Douglas-Kroll transformation is superior to other choices. In this work, the Douglas-Kroll transformation is extended to the sixth order for the first time, using computer algebra algorithms to obtain the working equations. It is shown how, at a given order, different variants of the Douglas-Kroll Hamiltonians are related. Various choices of the generalized transformation are examined numerically for the ground states of the one-electron atomic ions with nuclear charges Z=20, 40, 60, 80, 100, and 120. It is shown that compared to the improvement obtained by including the next order, the differences between various choices for the generalized Douglas-Kroll transformation are almost negligible. Results closest to the Dirac eigenvalues are not obtained with the optimal Douglas-Kroll transformation given by Wolf et al., but with the parametrization originally suggested by Douglas and Kroll.