Modular DNA-programmed assembly of linear and branched conjugated nanostructures

A new strategy for self-assembly and covalent coupling of encoded molecular modules into nanostructures with predetermined connectivity has been developed. The method uses DNA-functionalized oligo(phenylene ethynylene)-derived organic modules for controlling the assembly and covalent coupling of multiple modules. Rigid linear modules (LM) and tripoidal modules (TM) were functionalized with short oligonucleotides at each terminus. They can hybridize and thereby link up modules containing complementary sequences. Each terminus of the oligo(phenylene ethynylene) modules also consists of a salicylaldehyde moiety, which can form metal-salen complexes with other modules. The salicylaldehyde groups of two modules are brought in proximity when their adjoining DNA sequences are complementary, and they selectively form a manganese-salen complex in the presence of ethylenediamine and manganese acetate. The resulting structures consist of a matrix of linear and branched oligo(phenylene ethynylene)s which are linked by conjugated and rigid manganese-salen complexes. These nanostructures are potential conductors for applications in molecular electronics.     

Pretreatment of corn stover using wet oxidation to enhance enzymatic digestibility

Corn stover is an abundant, promising raw material for fuel ethanol production. Although it has a high cellulose content, without pretreatment it resists enzymatic hydrolysis, like most lignocellulosic materials. Wet oxidation (water, oxygen, mild alkali or acid, elevated temperature and pressure) was investigated to enhance the enzymatic digestibility of corn stover. Six different combinations of reaction temperature, time, and pH were applied. The best conditions (60g/L of corn stover, 195°C, 15 min, 12 bar O₂, 2 g/L of Na₂CO₃) increased the enzymatic conversion of corn stover four times, compared to untreated material. Under these conditions 60% of hemicellulose and 30% of lignin were solubilized, whereas 90% of cellulose remained in the solid fraction. After 24-h hydrolysis at 50°C using 25 filter paper units (FPU)/g of dry matter (DM) biomass, the achieved conversion of cellulose to glucose was about 85%. Decreasing the hydrolysis temperature to 40°C increased hydrolysis time from 24 to 72 h. Decreasing the enzyme loading to 5 FPU/g of DM biomass slightly decreased the enzymatic conversion from 83.4 to 71%. Thus, enzyme loading can be reduced without significantly affecting the efficiency of hydrolysis, an important economical aspect.     

Preconcentration and determination of Bismuth (III) at a chemically modified electrode containing 1-(2-pyridylazo)-2-naphthol

A chemically modified electrode (CME) containing 1-(2-pyridylazo-2-naphthol is evaluated for its ability to preconcentrate bismuth(III) prior to quantification by voltammetry. The CME approach is shown to be sufficiently sensitive for sub-nanomolar concentrations to be determinable after chemical deposition for 60 sec. Further, when the bismuth is deposited from iodide-containing sulphuric acid media, the discrimination against interference by copper(II) is significantly better than that obtained with conventional stripping analysis. The results obtained for Bi(III)( in an NBS reference solution agree well with the recommended value.     

Preparation of multilayer plasma protein films on silicon by EDC/NHS coupling chemistry

Crosslinked multilayer protein films were prepared from fibrinogen, albumin, IgG, a combination of fibrinogen and catalase, and blood plasma on silicon by ethyl-dimethyl-aminopropylcarbodiimide and N-hydroxy-succinimide coupling chemistry. The 4–70 nm thick films were placed in blood plasma and the additional protein deposition measured by null ellipsometry after 5 or 60 min of incubation. The activation of the complement system and intrinsic pathway of coagulation were indicated through the subsequent binding of anti-C3c, anti-C3d, anti-properdin and anti-HMWK on top of the surface bound blood plasma. The proportion of Annexin V, Propidium Iodide and 4,6-diamidino-2-phenylindole positive cells, and the secretion of tumor necrosis factor (TNF-) and interleukin-10 (IL-10) were analysed in a monocyte culture. The results show that well known protein coupling techniques can be used for the preparation of protein layers with well controlled thickness. The layers possess low contact activation of blood plasma and induce different release of TNF- and IL-10 in monocyte cultures.     

N-nitrosothialdine. Synthesis,X-ray crystallography,and N-N rotational barrier

Crystalline N-nitrosothialdine ($\text{2}$) has been prepared in 38% yield by treating thialdine ($\text{1}$) with $\text{n}$-butyl nitrite and acetic acid in hexane. X-Ray crystallography of $\text{2}$ revealed that its three methyl groups are a11 $\text{cis}$ and, rather surprisingly, all equatorial; this finding contrasts sharply with results for other nitrosamine heterocycles which have been investigated, whose bulky alpha substituents are forced into a primarily axial orientation by the large steric requirement of the N-N-0 system. The equatorial methyl group both displaces the nitroso group from the C-N-C plane and twists it somewhat about the N-N bond. N-Nitrosothialdine's unusually low barrier to rotation about the N-N bond (72 kJ/mole) is attributed to this steric crowding, combined with inductive electron withdrawal by the two sulfur atoms.     

Zum Nachweis und zur Bestimmung von Arsen

Ohne Zusammenfassung     

Fettbestimmung in fettarmer Milch

Ohne Zusammenfassung     

Extending the Campbell-Hausdorff multiplication

Let j be an ideal of the finite-dimensional Lie algebra g such that 2i is not an eigenvalue of adx:g g for everyxj. It is shown that there exists an open ballV around 0 and an analytic extension of the Campbell-Hausdorff multiplication °:(j+V)×(j+V) g. This generalizes an old result by Dixmier significantly, and gives a new and easier proof.Dedicated to Karl Heinrich Hofmann on the occasion of his 60th birthday