Some aspects of lateral chain order in cellulosics from X-ray scattering

This paper gives an overview of our recent research activities on the lateral supramolecular order of a variety of native and man-made cellulosics considering respective results from the literature. Wide-angle X-ray scattering (WAXS) was the main investigation technique used. Lateral root mean squared lattice strains between 2 and 3% were determined for the materials investigated. Crystallite sizes obtained without considering lattice distortions usually do not deviate by much more than –10% from the real, i.e. fully corrected values. This means that it is sufficient to use the simple Scherrer equation for determining lateral crystallite sizes for most routine investigations of cellulosic materials. The possible superposition of WAXS peaks of the triclinic I and monoclinic I lattice types, however, has to be considered in crystallite size determinations for Valonia cellulose. It could be shown that neglecting this fact can lead to crystallite sizes being about 20% below the true ones. Lateral crystallite dimaensions for native celluloses vary between 4nm (dissolving pulps) and 10-15 nm (Valonia). Except for bacterial cellulose, the WAXS crystallite sizes are distinctly smaller than the microfibril dimensions obtained from electron microscopy. The man-made fibres investigated showed lateral crystallite dimensions between 3 and 5nm. The importance of lateral crystallite dimensions for the properties of man-made fibres and for the alkalization process of native cellulose id demonstrated.     

The identification of element 108

In-beam studies with (α,4n) and (³He, 3n) reactions have located a second 10⁺ state closely above the 10⁺ isomers in¹⁴⁴Gd and¹⁴²Sm. The data characterize the¹⁴²Sm 10⁺ isomer as the νh ₁₁ ^2/?2 excitation in contrast to¹⁴⁴Gd where the 10⁺ isomer is of πh ₁₁ ^2/2 character.     

Strukturdynamische organometall-komplexe: III. Synthese,struktur und bindungsverhältnisse der komplexe (η5-C5H5)Pd(η1-C5H5)PR3

The complexes (η₅-C₅H₅)Pd(η¹-C₅H₅)PR₃ which are prepared from [Cl(PR₃)-Pd]₂(μ-OCOCH₃)₂ and TlC₅H₅ are fluxional in solution. According to the ¹H and ¹³C NMR spectra at various temperatures, two dynamic processes occur. The process with the higher activation energy is a π/σ (η⁵/η¹) exchange of the two different cyclopentadienyl ligands, whereas the second one with the lower activation energy presumably is a metallotropic rearrangement (1,2-shift). The coalescence temperature for the η⁵/η¹ exchange depends on the size of the phosphine. The X-ray structural analysis of (C₅H₅)₂PdPPrⁱ₃ proves that it exists as a “frozen” η⁵ + η¹ structure in the crystal with the palladium approximately in a square-planar coordination. The η⁵-bonded cyclopentadienyl ring shows some unusual bonding patterns which are obviously electronic in nature. EHT-MO calculations for (η⁵-C₅H₅)PdCH₃(PH₃) indicate that in this model system alternating CC distances in the ring and a stronger bond of the metal to one of the five carbon atoms of the C₅H₅ ligand are to be expected. The calculations suggest that in similar complexes possessing a six-electron donor ligand like C₅H₅^? and a metal fragment which is isolobal to PdCH₃(PH₃)⁺, analogous distortions should be observed. Some reactions of the compounds (η⁵-C₅H₅)Pd(η¹-C₅H₅)PR₃ are described.     

The closure of cones in the algebra of test functions

We prove that the topological closure of the cone K of positive elements in the algebra of test functions is the same for several topologies (K?τo° = K?τ∞). Further we show that all elements of the closure of K are of the form

$\text{∑}\text{I=1}\text{∞}\text{f}{}^{\mathrm{(i)1}}\text{f}{}^{\mathrm{(i)}}\text{with f}{}^{\mathrm{<mtext>(</mtext><mtext>i</mtext><mtext>)</mtext>}}\text{?}\text{L}{}_{\mathrm{?}}$

and the sum converges. Applying these results, we give a characterization of the elements of K?^τ_o too.     

Isolation,Structure, and Biological Activities of Long-Chain Catechols of Plectranthus sylvestris (Labiatae)

Antioxidant activity guided fractionation of extracts of the aerial parts of the title plant and HPLC separation yielded a series of oxygenated long-chain alkylcatechols. Their structures were inferred by spectroscopic methods and chemical transformations to be the novel 4-[(2S,4R,6S)-4-(acetyloxy)tetrahydro-6-pentyl-2H-pyran-2-yl]benzene-1,2diol ( 1a ), 4-[(2S,4R6S)-tetrahydro-4-hydroxy-6-pentyl-2H-pyran-2-yl]benzene-1,2-diol ( 1b ), 4-[(3S,5S)-5-(acetyloxy)-3-hydroxydecyl]benzene-1,2-diol (2a), 4-[(3S,5S)3-(acetyloxy)-5-hydroxydecyl]benzene-1,2-diol ( 2b ), (3S,13Z)-1-(3,4-dihydroxyphenyl)-3-hydroxydocos-13-en-5-one ( 3a ), (Z)-1-(3,4-dihydroxyphenyl)docos-13-en-5-one ( 4 ), besides the known l-(3,4-dihydroxyphenyl)icosan-5-one ( 5 ). The absolute configurations of the optically active compounds which are structurally related to the [n]-gingerols ( 6 ) and -diols ( 7 ) were established by the high-field ¹H-NMR application of Mosher's method. All compounds are in vitro potent antioxidants, inhibiting the Fe²⁺-catalysed autoxidation of linoleic acid in the same order of magnitude as the commercial antioxidant 2,6-di(tert-butyl)-4-methylphenol (BHT). The dose-dependent inhibitory effects on soybean-lipoxygenase are in the μmol range, that of the most effective compound ( 3a ) in the nmol range, hence being significantly more potent than the Known anti-inflammatory and analgesic drugs indomethacin and nordihydroguaiaretic acid.     

Synthese und Kristallstruktur der Ternären Selten-Erd-Chloride Na2MCl5 (M = Sm,Eu, Gd)

Synthesis and Crystal Structure of the Ternary Rare Earth Chlorides Na₂MCl₅ (M = Sm, Eu, Gd) Single crystals of Na₂EuCl₅ were obtained from the melt of NaCl and EuCl₃ in a 2:1.2 molar ratio by slow cooling. It crystallizes in the orthorhombic crystal system (space group Pnma) with the structure of K₂PrCl₅ with a = 1 204.0(3) pm, b = 833.9(3) pm, c = 768.2(3) pm, Z = 4. Pure powder samples of the compounds Na₂MCl₅ (M = Sm? Gd) are available by heating mixtures of the binary components below the melting point.     

Stable isotopes for heavy element production

The synthesis of heavy elements and the search for new superheavy elements is one of the exciting fields in modern nuclear physics and chemistry. Heavy elements are produced by heavy-ion fusion reactions. Necessary prerequisites are intense heavy-ion beams from pure isotopic material and thin isotopically enriched targets. At GSI the elements from 107 to 112 were produced using targets of Pb and Bi and beams of the most neutron rich isotopes of Cr, Fe, Ni, and Zn.¹ We present the experimental set-up consisting of target wheel, velocity filter SHIP (Separator for Heavy Ion Reaction Products), and detector system. We shortly describe the status of the ion source techniques for delivering intense and stable beams for this kind of experiment.² The manufacturing and properties of various source - target combinations used for the synthesis of the elements by now are discussed in detail as well as the possibilities for extending the experiments into the region of superheavy elements.³     

On the rational design of substrate mimetics: The function of docking approaches for the prediction of protease specificities

The behaviour of substrate mimetics in mediating the acceptance of nonspecific acyl moieties by proteases has been investigated as a direct function of their site-specific ester leaving groups. In this contribution we report on a computational approach to rationalise this interplay and to predict the power of a potential ester moiety to act as a suitable substrate mimetic for a given enzyme by means of an automated docking procedure. Investigations with seven distinct substrate mimetics and two proteases, subtilisin and chymotrypsin, show a clear correlation between the theoretically calculated binding energies DeltaE and the specificity constants k(cat)KM(-1) obtained from parallel hydrolysis kinetic studies. These results prove the general function of the docking approach as a rational model not only in predicting the general acceptance of a substrate mimetic in a qualitative manner, but also to provide reliable information on its individual specificity towards proteases.     

1,1'-bis(6-chloroanthraquinonyl)amine as a reagent for trace amounts of boron

A new reagent, 1,1'-bis(6-chloroanthraquinonyl)amine, has been synthesized and applied to the determination of trace amounts of boron. A blue complex is formed on heating with orthoboric acid in 96% sulfuric acid medium.Oxidizing agents and some cations interfere with the method; separation of the boron either by distillation of the methyl ester or by ion exchange removes such interferences The method is very sensitive i.e., 0.0005 μg B/cm², and can be used for the analyses of vegetation.