[Analysis of image quality and dose calculation accuracy in cone beam CT acquisitions with limited projection data (half scan, half fan) with regard to usability for adaptive radiation therapy treatment planning].

Unlabelled: Subject of this study is the question of whether cone beam CT (CBCT) images with reduced projection data are suitable for use in adaptive radiation therapy (ART) treatment planning. For this purpose image quality and dose calculation accuracy depending on imaging modality were analysed. In this context, two CBCT-methods will be indicated having reduced projection data sets: Scans acquired with 200° rotation angle in order to accelerate the CBCT process (half scan), or scans with an asymmetric cone beam and detector offset, used to enlarge the field-of-view (half fan).

Synthesis and biological evaluation of novel biotin-iminoalditol conjugates.

Biotin-iminosugar conjugates of different configuration such as D-gluco, D-galacto, L-ido as well as a furanoid representative in the D-manno configuration have been synthesised and exhibit powerful inhibition of beta-glucosidase from Agrobacterium sp. with K(i) values in the range of the respective parent compounds. Such molecular probes have potential for activity-based protein profiling taking advantage of the biotin-(strept)avidin interaction.

The quest for silylhydroboranes: (Me(3)Si)(3)SiBH(2).

Reaction of BH(3)·NEt(3) with tris(trimethylsilyl)silylpotassium yielded the respective silylboranate. Abstraction of a hydride with B(C(6)F(5))(3) led to the neutral silylborane, which could be derivatised as an Et(3)N adduct. Treatment of the boranate with Cp(2)Ti(btmsa) resulted in exchange of THF coordinating to potassium by Cp(2)Ti(btmsa).

Polynuclear copper(II) complexes of di-2-pyridyl ketone derivatives and tert-butylphosphonic acid: crystal structures and magnetic behaviour.

The syntheses, structural characterization, and magnetic behavior of four new copper(II) complexes derived from tert-butylphosphonic acid and di-2-pyridyl ketone with formulae [Cu{(py)(2)C(OH)(2)}](C(4)H(9)PO(3)H)(2).(H(2)O)(2) (1), [Cu(2)(mu(2)-C(4)H(9)PO(3)H){(py)(2)C(OCH(2)CH(3))O}(mu(2)-NO(3))(NO(3))(H(2)O)](n).(H(2)O)(n) (2), [Cu(4)(mu(2)-C(4)H(9)PO(3)H)(2)(mu(4)-C(4)H(9)PO(3))(2){(py)(2)C(OCH(3))O}(2)].

Synthesis and structural diversity of oligosilanylzinc compounds.

Reactions of potassium oligosilanyls with ZnCl(2) lead to the formation of oligosilanylzinc compounds with zinc's coordination sphere expanded by ligation of TMEDA, an additional oligosilanyl group, or a chloride ion.

Group 4 metallocene complexes of disilenes, digermenes, and a silagermene.

Reactions of 1,2-dipotassiotetrakis(trimethylsilyl)disilane with group 4 metallocene dichlorides lead to the formation of the respective metallocene 1,1,2,2-tetrakis(trimethylsilyl)disilene complexes. While the disilene titanocene complex could be structurally characterized, the zirconocene and hafnocene compounds, which are believed to possess some degree of bis-[bis(trimethylsilyl)silylene] character, can only be isolated in substance as the respective trimethylphosphane adducts. Analogous metallocene 1,1,2,2-tetrakis(trimethylsilyl)digermene complexes and a tetrakis(trimethylsilyl)silagermene complex were prepared.

Oligosilylated group 4 titanocenes in the oxidation state +3.

Reactions of oligosilylanions with Cp2TiCl2 led to the formation of ate-complexes of silylated titanocenes, which form upon silylation of the intermediate K[Cp2TiCl2].18-crown-6.

New roles of flavoproteins in molecular cell biology: an unexpected role for quinone reductases as regulators of proteasomal degradation.

Quinone reductases are ubiquitous soluble enzymes found in bacteria, fungi, plants and animals. These enzymes utilize a reduced nicotinamide such as NADH or NADPH to reduce the flavin cofactor (either FMN or FAD), which then affords two-electron reduction of cellular quinones. Although the chemical nature of the quinone substrate is still a matter of debate, the reaction appears to play a pivotal role in quinone detoxification by preventing the generation of potentially harmful semiquinones.

X-ray crystal structure of Saccharomyces cerevisiae Pdx1 provides insights into the oligomeric nature of PLP synthases.

The universal enzymatic cofactor vitamin B6 can be synthesized as pyridoxal 5-phosphate (PLP) by the glutamine amidotransferase Pdx1. We show that Saccharomyces cerevisiae Pdx1 is hexameric by analytical ultracentrifugation and by crystallographic 3D structure determination. Bacterial homologues were previously reported to exist in hexamer:dodecamer equilibrium.

2-Acetamino-1,2-dideoxynojirimycin-lysine hybrids as hexosaminidase inhibitors.

Cyclisation by double reductive amination of 2-acetamino-2-deoxy-D-xylo-hexos-5-ulose with N-2 protected L-lysine derivatives provided 2-acetamino-1,2-dideoxynojirimycin derivatives without any observable epimer formation at C-5. Modifications on the lysine moiety gave access to lipophilic derivatives that exhibited improved hexosaminidase inhibitory activities.

Thermophysical properties of rhodium obtained by fast pulse-heating.

The so-called platinum metals are Ru, Rh, Pd, Os, Ir and Pt. Our workgroup has already published data on Pd, Ir and Pt. The present work will focus on measurements of the thermophysical properties of rhodium, which have been carried out recently.

Shuttling germanium atoms into branched polysilanes.

Lewis acid-catalyzed rearrangement reactions of trimethylgermylated small permethylated oligosilanes were found to show a strong tendency of the germanium atoms to move to the more highly silylated positions of the molecule. This makes possible the construction of molecules with high germanium content in the core parts of the molecules by the following repeated sequence: introduction of trimethylgermyl group followed by rearrangement. Quantum-mechanical computations at the B3LYP/6-311+G(d,p) level suggest that the exergonic rearrangement proceeds in a reaction cascade via germylium and silylium ions, which transform by 1,2-silyl and -methyl shifts.

Dissection of contributions from invariant amino acids to complex formation and catalysis in the heteromeric pyridoxal 5-phosphate synthase complex from Bacillus subtilis.

Pyridoxal 5-phosphate (PLP), an active form of vitamin B(6), is one of the most versatile cofactors and is involved in numerous biochemical reactions. The main pathway for de novo PLP biosynthesis leads to direct formation of PLP from a pentose and triose. This reaction is catalyzed by the heteromeric PLP synthase, consisting of the synthase subunit Pdx1 and the glutaminase subunit Pdx2.

Enantioseparation of nonproteinogenic amino acids.

The enantioseparation of structurally related N-protected beta-/gamma-amino acids, beta-/gamma-amino amides, and beta-/gamma-amino nitriles by using six different commercially available chiral stationary phases (CSPs) is reported. The synthetic key step to introduce stereochemical asymmetry into all compounds is an enzymatic kinetic resolution of the racemic nitriles to the respective amino amides and/or amino acids, depending on the class of enzyme (nitrile hydratase or nitrilase) applied. The separation efficiencies of all CSPs with regard to functional groups as well as structural variations of the amino acid derivatives depicted in Fig.

Formation of formal disilene fluoride adducts.

Reactions of trisilylated silylfluorides with potassium tert-butoxide were found to give disilylated fluorosilylenoids. The latter undergo a self-condensation reaction, leading to the formation of beta-fluorodisilanyl anions, which may also be considered as fluoride adducts of disilenes. The stereochemical outcome of this self-condensation depends on the bulkiness of the silyl substituents.

1-Deoxygalactonojirimycin-lysine hybrids as potent D-galactosidase inhibitors.

Cyclization by double reductive amination of L-arabino-hexos-5-ulose with suitably protected D- as well as L-lysine derivatives provided 1-deoxygalactonojirimycin lysine hybrids without any observable epimer formation at C-5. Modifications on the lysine moiety by acylation gave access to lipophilic derivatives which exhibited excellent D-galactosidase inhibitory activities.

Lifetime accumulation of (137)Cs and (40)K in the ribs and sternum of an Austrian "mountain pasture" cow.

The accumulation of natural and artificial radionuclides in humans and domestic animals is of interest in estimating effective doses of exposed humans and to decide whether animal products can be used for nutrition of the population. In this paper we present an investigation of the (137)Cs- and (40)K-activity levels of the ribs and sternum of a "mountain pasture" cow, born in a highly contaminated region of Styria, Austria, at the time of the radioactive fallout following the Chernobyl accident. This is the first systematic investigation of the variation in activity levels of a contaminated animal.

Induction of apoptosis in yeast by L-amino acid oxidase from the Malayan pit viper Calloselasma rhodostoma.

Here we report for the first time that L-amino acid oxidase (LAAO), a major component of snake venom, induces apoptosis in yeast. The causative agent for induction of apoptosis has been shown to be hydrogen peroxide, produced by the enzymatic activity of LAAO. However, the addition of catalase, a specific hydrogen peroxide scavenger, does not prevent cell demise completely.

The Amadori rearrangement as key reaction for the synthesis of neoglycoconjugates.

The Amadori rearrangement was introduced as a key step for the conjugation of carbohydrate moieties with suitable amines such as aliphatic amines and amino acid derivatives. The rearrangement products were further transformed into the corresponding 1-N,2-O cyclic carbamates employing triphosgene to obtain anomerically stable glycoconjugates. The reaction conditions were probed on a model substrate, 3,5-di-O-benzyl-alpha,beta-d-glucofuranose and further applied to d-glycero-d-gulo-heptose, which gave 'd-gluco-conjugates' in the alpha-anomeric form exclusively in high isolated yields.

Molecular structures of the digermanes Me2XGeGeXMe2 (X = Me, Cl, and H): an ab initio study combined with experimental investigation by Raman spectroscopy and gas electron diffraction.

Ab initio calculations were carried out to investigate the potential-energy surface for internal rotation of the methylated digermanes hexamethyldigermane Me(3)GeGeMe(3) ( 1), dichlorotetramethyldigermane Me(2)ClGeGeClMe(2) ( 2), and tetramethyldigermane Me(2)HGeGeHMe(2) ( 3). Different basis sets [6-31+G(d), SDD, aug-cc-pVTZ] were employed at the DFT and MP2 levels of theory to optimize structures and to calculate energies and vibrational frequencies. For 1, one minimum representing a staggered structure was located on the potential-energy surface.

Glycosidase profiling with immobilised glycosidase-inhibiting iminoalditols--a proof-of-concept study.

Three typical glycosidase-inhibiting iminoalditols were attached to a polyamine surface displayed on a silicon chip. Exposure to a representative beta-glucosidase revealed selective binding events reflecting the different structural features of the inhibitors probed in this study. This provides a proof-of-concept for the successful exploitation of microarrays of typical reversible glycosidase inhibitors of the iminosugar family.

Impact of bidirectional charge transfer and molecular distortions on the electronic structure of a metal-organic interface.

Interface energetics are of fundamental importance in organic and molecular electronics. By combining complementary experimental techniques and first-principles calculations, we resolve the complex interplay among several interfacial phenomena that collectively determine the electronic structure of the strong electron acceptor tetrafluoro-tetracyanoquinodimethane chemisorbed on copper. The combination of adsorption-induced geometric distortion of the molecules, metal-to-molecule charge transfer, and molecule-to-metal back transfer leads to a net increase of the metal work function.