Flammenpyrolytische Silikatbeschichtung bei Normaldruck als Alternative zu Vakuumverfahren. Combustion CVD of silica as an alternative method to vakuum treatment

In advancement of Pyrosil®‐technology a new kind of precursor delivery was developed, build and tested on real substrates. A Lab‐demonstrator was build to demonstrate the resources of the technology.     

Kommunikationsoberfläche Membran‐ Vorbild für moderne Nanoanalytik

A central event in the life of a cellular system is the interaction between the exterior and the interior compartments. Biochemical signals arrive at the cellular surface, bind to their membrane bound receptor followed by a conformational change triggering the release of an internal chemical or electrical signal.This basic principle is followed by all our perceptive abilities like sense of smell or taste, but also by different signal transduction pathways involved in nerve conductivity, vision, sense of touch or hearing. To follow and mimic this principle of parallel registration is one of the aims of modern nanobiotechnology. If we are able to specifically biofunctionalize small arrays of a solid surface, which could be an electrode or a semiconductor, this approach will enable us to build up devices called “biochips” or “biosensors” that allow the determination of bioactive molecules with high specificity at lowest concentrations. Potential pharmacological active substrates might be screened as well as new receptors may be determined. Applications in genomics as well as proteomics are realistic. The major prerequisite for such a broad spectrum of applications is the fabrication of receptive surfaces. Biomolecules have to be surface‐adsorbed in a highly reproducible, oriented and well organised fashion, a task which in biology is taken by the cellular membranes as external or internal receptive surfaces. The physical principles like hydrogen bonds, electrostatic or hydrophobic interactions that lead to such an organized surface are well known. To synthesize molecular building blocks and to position them onto an otherwise unspecific surface is one of the challenges of nanobiotechnology combining biological knowledge and chemical skills with biophysical techniques that allow to handle or analyze even single molecules.     

Kinetic studies on strawberry anthocyanin hydrolysis by a thermostable anthocyanin-β-glycosidase from Aspergillus niger

Several kinetic characteristics of a thermostable anthocyanin-β-glycosidase from Aspergillus niger have been evaluated. With strawberry anthocyanins as substrate, at pH optimum (4·0) and t = 30°C, K_m was found to be $\text{123 ± 4 μ}\text{m}$ and V_max, 1·16 ± 0·06 μmol min^?1mg^?1 protein. Temperature optimum was observed at about 68°C. The apparent energy of activation was calculated to be 11 ± 1 kcal/mol. The inhibitory effect of different sugars and sugar derivatives was examined. Glucono-deltalactone ($\text{K}{}_{\mathrm{<mtext>i</mtext>}}\text{= 2·3 ± 0·1 μ}\text{m}$), gluconic acid ($\text{K}{}_{\mathrm{<mtext>i</mtext>}}\text{= 82 ± 2 μ}\text{m}$) and glucose ($\text{K}{}_{\mathrm{<mtext>i</mtext>}}\text{= 1·3 ± 0·1}\text{m}\text{m}$) appeared to be competitive inhibitors of this enzyme.     

Effects of growth with ethanol on fermentation and membrane fluidity of Saccharomyces cerevisiae

Saccharomyces cerevisiae HSc was grown with ethanol at concentrations up to 10% (v/v). The immediate effects of additions of externally added ethanol on CO₂ production and O₂ consumption of washed organisms were studied by stopped-flow membrane inlet quadrupole mass spectrometry. Fermentative activities of organisms grown with ethanol (0–5% v/v) showed similar sensitivities to inhibition by ethanol, whereas those grown with 10% (v/v) ethanol had become protected and were markedly less sensitive. The fluidity of subcellular membrane fractions was measured by determination of the temperature dependence of the rotational order parameter of the spin label 5-doxyl stearic acid (free radical) by electron spin resonance. Mitochondria prepared from yeasts grown with 0, 7 and 9% (v/v) ethanol showed similar overall fluidity, although differences in temperature-dependent behaviour indicate altered lipid composition or lateral phase separations. On the other hand the microsomal fraction from organisms grown with 9% ethanol showed a remarkable increase in fluidity. These data suggest that the protective effects of growth with ethanol near the limit of tolerance on fermentative activities may arise from altered plasma membrane fluidity properties.     

Stability, in-Vitro and in-Vivo Release Studies from Metronidazole Ointments

The influence of ointment formulation on the stability, the in-vitro release and the in-vivo absorption through the skin of rabbits was investigated. The choice of the selected ointments has no influence on the drug stability with the exception of an acidified emulsion base. A good correlation between in-vitro release and in-vivo absorption was found revealing that metronidazole was quickly released and effectively absorbed from a polyethylene glycol base.     

Well-defined polymer precursors synthesized by RAFT polymerization of N,N-dimethylacrylamide/N-acryloxysuccinimide: random and block copolymers

N,N-dimethylacrylamide (DMA) and N-acryloxysuccinimide (NAS) were copolymerized by the reversible addition–fragmentation chain transfer (RAFT) polymerization technique, to obtain random and block copolymer precursors onto which different side-groups may be statistically grafted via the reactive NAS units. These reactive copolymers have interesting applications in various fields such as coatings and paints, water purification and biology. Random poly(DMA-co-NAS) copolymer chains were synthesized with a 75/25 molar ratio, high conversion, an excellent molecular weight (MW) control from 5000 to 130 000 g mol⁻¹, and low polydispersity index (M_w/M_n<1.1). Poly(DMA-b-NAS) block copolymers were synthesized by a two step method, in which a poly(DMA) homopolymer was prepared first and then used as macro-chain transfer agent to polymerize NAS. For example, a poly(DMA-b-NAS) sample was obtained with an average molecular weight of 44 300/7400 g mol⁻¹ corresponding to 447 DMA and 44 NAS units. Such block copolymers had not yet been synthesized by any controlled polymerization technique. They can be used to prepare polymers with exactly the same backbone and an increasing number of different side groups (e.g. hydrophobic, ionic or fluorescent).     

Tight analysis of the (1+1)-EA for the single source shortest path problem

We conduct a rigorous analysis of the (1+1) evolutionary algorithm for the single source shortest path problem proposed by Scharnow, Tinnefeld, and Wegener (The analyses of evolutionary algorithms on sorting and shortest paths problems, 2004, Journal of Mathematical Modelling and Algorithms, 3(4):349-366). We prove that with high probability, the optimization time is O(n2 max{?, log(n)}), where ? is the smallest integer such that any vertex can be reached from the source via a shortest path having at most ? edges. This bound is tight. For all values of n and ? we provide a graph with edge weights such that, with high probability, the optimization time is of order Ω(n2 max{?, log(n)}). To obtain such sharp bounds, we develop a new technique that overcomes the coupon collector behavior of previously used arguments. Also, we exhibit a simple Chernoff type inequality for sums of independent geometrically distributed random variables, and one for sequences of random variables that are not independent, but show a desired behavior independent of the outcomes of the previous random variables. We are optimistic that these tools find further applications in the analysis of evolutionary algorithms.