Direct spectrophotometric assay of laccase using diazo derivatives of guaiacol

Laccase (EC 1.10.3.2) is a widespread cuproenzyme able to oxidize various types of phenols and similar aromatic compounds through a one-electron transfer mechanism. The enzyme has already found its way into the market as a biocatalyst. Because of its ability to be paired by electron mediators, the expectation for employing laccases in versatile processes is very high. There are a few spectrophotometric methods for assaying the laccase activity; however, all of them are based on the formation of product(s) resulting from the enzymatic and inevitable succeeding chemical reactions. Use of diazo derivatives of guaiacol (DdG) was developed as a new spectrophotometric method based on substrate depletion allowing direct assessment of enzyme activity has been introduced. This method allows accurate comprehensive kinetic studies of laccases and provides reliable information about the quality of docking of different substrates or one substrate to the active sites of different laccases. Using this method, the kinetic parameters of various DdG carrying different electron donating and withdrawing substituents were used to assay laccase from Neurospora crassa. 2-Methoxy-4-[(4-phenyl)azo]-phenol (K(m) = 93.5 μM and V = 1.98 μM/min) was identified as an appropriate substrate for the accurate and routine spectrophotometric based assay of laccases.     

New experimental methods for investigating variable amplitude loading effects in HCF and VHCF regimes

For the investigation of variable amplitude loading effects, it is necessary to increase the test frequency of conventional testing facilities because, for the evaluation of many components, test results with more than 10⁷ cycles are also needed. However, due to the restriction of conventional testing facilities and the associated costs and required time, variable amplitude testing is almost limited to 10⁷ cycles. Service loading with more than 10⁷ cycles to failure is characterized by low amplitudes with a high number of cycles. The challenge in investigation of material fatigue in the regimes of high cycle and very high cycle fatigue is to apply this large number of cycles to failure in an acceptable time frame. For this reason, it is essential to use a machine, which is able to operate at high frequencies. In this paper, two testing machine concepts with piezo actuators are presented. In the first concept, a high performance piezo stack actuator is presented, in which the specimen and the load cell are mechanically assembled in series. This set‐up applies forces up to 10 kN and testing frequencies up to 1000 Hz. The second testing facility is a hybrid testing system, which consists of an inertial mass actuator and a servo hydraulic actuator connected in parallel. Both systems are capable of testing normal specimen dimensions and provide the possibility to work with variable amplitude loading as well as constant amplitude loading.     

Silber‐Nano‐Cluster in einer plasmapolymeren Releaseschicht. Silver nano cluster in a plasma polymer release layer

The problem of insufficient adhesion and bad chemical stability of silver clusters on many substrates can be solved by embedding of the particles in a plasma polymer film. Due to the high permeability of the matrix an exchange of silver ions with the surface is possible and therefore the composite films show a very good antimicrobial effect. For a clinical application study wound care products were coated with these films. In comparison to uncoated wound cares products the coated care products yield an excellent result.     

Fungicidal and Insecticidal Activity of O-Acyl Chitosan Derivatives

Summary A series of O-(acyl) chitosan (OAC) derivatives with a degree of substitution (DS) between 0.02 and 0.28 were synthesized by reaction of alkanoic acid derivatives with chitosan in the presence of H₂SO₄ as a catalyst. The reaction was performed at 80 °C for 4 h with different mol ratios of alkanoic acids to chitosan. The synthesized compounds were analyzed by ¹H- and ¹³C-NMR spectroscopy. A high DS was obtained with O-(butyroyl) chitosan (DS 0.28) at a mol ratio of (1:5) chitosan to butyric acid. Their fungicidal activity against the grey mould Botrytis cinerea (Leotiales: Sclerotiniaceae) and the rice leaf blast pathogen Pyricularia grisea (Teleomorph: Magnaportha grisea) has been evaluated. O-(decanoyl) chitosan at mol ratio of 1:2 (chitosan to decanoic acid) was the most active compound against B. cinerea (EC₅₀=1.02 g.l^-1) and O-(hexanoyl) chitosan displayed the highest activity against P. grisea (EC₅₀=1.11 g.l^-1). It has been mentioned that some derivatives also repressed spore formation at rather high concentrations (1.0, 2.0 and 5.0 g.l^-1). The insecticidal activity has been screened at 5 g.kg^-1 artificial diet against the larvae of the cotton leafworm Spodoptera littoralis (Lepidoptera: Noctuidae). The results revealed that all of the synthesized derivatives showed high inhibition of growth of the larvae of S. littoralis compared to chitosan (7% growth inhibition) and the most active one was O-(decanoyl) chitosan (64% growth inhibition) after 5 days of feeding on treated artificial diet.     

Predictors and outcome of early- versus late-onset major bacterial infections in liver transplant recipients receiving tacrolimus (FK506) as primary immunosuppression

Major bacterial infections and the predictors of early (within 100 days of transplantation) versus late onset (after 100 days post-transplant) bacterial infections were prospectively assessed in 130 consecutive liver transplant recipients receiving tacrolimus (FK506) as primary immunosuppression. The median follow-up period was 38 months. Overall, 35% (45/130) of the patients developed 67 episodes of major bacterial infections (0.52 episodes/patient). Sixty-three percent of the major bacterial infections occurred early, and 37% occurred in the late post-transplant period. Eighty-four percent of the abdominal infections occurred early, whereas 38% of the cases of pneumonia, 60% of the cases of primary bacteremia, and 50% of the biliary infections occurred late. By logistic regression analysis, portal vein thrombosis was the most significant independent risk factor for early-onset major bacterial infection (odds ratio 4.1; 95% CI 1.4-12.2), and recurrent hepatitis C was the most significant independent predictor of late-onset major bacterial infections (odds ratio 6.21; 95% CI 1.9-20.2). Thus, sources and risk factors differ for early versus late-onset bacterial infections after liver transplantation. Knowledge of the differences in the potential sources, the pathogens, and the predictors of early versus late-onset bacterial infections can be valuable in the evaluation and empiric treatment of liver transplant recipients with bacterial infections.     

A Mueller matrix formalism for modeling polarization effects inerbium-doped fiber

The effects of erbium anisotropy in erbium-doped fiber lasers, sources, and amplifiers are examined. Starting from basic ion properties, inversion and gain equations are derived analytically to describe polarization dependencies. A novel matrix form of the Er³⁺ rate equations is presented to propagate powers and polarization states. These equations are then numerically integrated and compared to experimentally observed polarization hole burning and polarization dependent gain. The theoretical predictions agree strongly with experiment in all cases     

Optimization of large-scale fiber sensor arrays incorporatingmultiple optical amplifiers. I. Signal-to-noise ratio

We report on optimizing the signal-to-noise ratio (SNR) of large-scale fiber sensor arrays employing erbium-doped fiber amplifier (EDFA) telemetry with respect to the number of sensors per rung, the number of amplifiers per array, and the coupling ratio between the fiber buses and the rungs. Broad optimum regions are found, providing design flexibility to minimize pump power requirements. Simulations predict that 300 sensors can be multiplexed on a fiber pair while maintaining a high sensitivity (1 μrad/√(Hz)) for all sensors with a moderate input pump power (<1 W)     

Primary structure of matrilin-3, a new member of a family of extracellular matrix proteins related to cartilage matrix protein (matrilin-1) and von Willebrand factor

A mouse cDNA encoding for matrilin-3, the third member of the novel matrilin family of extracellular matrix proteins, was cloned. The protein precursor of 481 amino acids consists of a putative signal peptide, a short positively charged sequence, a single vWFA-like domain followed by four epidermal growth factor-like modules and a potential coiled-coil alpha-helical oligomerization domain at the C-terminus. It is the smallest member of the matrilin family with a predicted Mr of the mature protein of 48 902. The primary structure of a C-terminal portion of 310 amino acids of the human matrilin-3 was determined and showed a sequence identity to the mouse matrilin-3 of 84.8%. Northern blot hybridization of mouse matrilin-3 mRNA showed a 2.9 kb mRNA expressed in sternum, femur and trachea and indicates a cartilage-specific expression.     

A note on Gevrey regular KAM theory and the inverse approximation lemma

A theorem of the type Kolmogorov-Arnold-Moser holds for small real analytic perturbations of a family of parallel flows on a torus, yielding conjugacies to Diophantine parallel flows that depend Whitney-Gevrey regularly on parameters. This follows from an adaptation of the inverse approximation lemma. The method of proof is general and extends to a wide range of problems of KAM type.