Photo-electro-chemical properties of TiO2 mediated by the enzyme glucose oxidase

Electrochemical measurements show that the enzyme glucose oxidase (GO) is adsorbed on the surface of TiO₂ without apparently changing the flat band potential of the semiconductor, indicating that it does not cause a change of the energy of conduction band electrons. On the other hand, it is observed that GO markedly increases the efficiency of the two electron reduction of O₂ to H₂O₂ which is accumulated in the solution phase.

ESR spin trapping investigations indicate that GO favors the formation of OH radicals, due to either the inhibition of charge recombination processes or to H₂O₂ reduction by conduction band electrons. Accordingly, photo-oxidation of different alcohols to the corresponding radical species is also enhanced in the presence of GO.

The photo-oxidation of 1,2-propandiol on TiO₂/GO is regioselective in that (i) partial oxidation to hydroxyacetone is observed and (ii) no mineralization (full combustion to CO₂) of the substrate occurs. These facts are of particular interest in the field of studies concerning the design of new photocatalytic systems with enhanced activity and controllable oxidative power.     

Urease production by Streptococcus thermophilus

In order to identify potential alternative sources of urease for the removal of urea from alcoholic beverages, 205 strains of lactic acid bacteria belonging to 27 different species were screened for urease production. Only Streptococcus thermophilus produced urease. Cell permeabilization with toluene allowed to increase activity significantly. Optimal pH for urease activity in whole and permeabilized cells and of cell free extracts differed slightly, but was in the range 6.0-7.0. Significant activity was retained at pH 3.0 and 8.0, and, for cell free extracts, at pH 4.0 in the presence of ethanol. Urease production was evaluated in fermentations with pH control (5.25-6.5) and without pH control. Very little urease was produced in absence of urea, which at 5g/l slowed growth significantly in fermentations without pH control, but prevented a decrease in pH below 5.1 and resulted in higher final biomass. Optimal pH for growth was between 6.0 and 6.5 but specific urease activity was higher for fermentations at low pH at the beginning of the exponential phase. However, a higher total urease activity was obtained at pH 6.0 and 6.5 because of higher biomass. Potential technological applications of urease production by S. thermophilus are discussed.     

An approach to usability evaluation of e-learning applications

Despite recent advances of electronic technologies in e-learning, a consolidated evaluation methodology for e-learning applications is not available. The evaluation of educational software must consider its usability and more in general its accessibility, as well as its didactic effectiveness. This work is a first step towards the definition of a methodology for evaluating e-learning applications. Specific usability attributes capturing the peculiar features of these applications are identified. A preliminary user study involving a group of e-students, observed during their interaction with an e-learning application in a real situation, is reported. Then, the proposal is put forward to adapt to the e-learning domain a methodology for systematic usability evaluation, called SUE. Specifically, evaluation patterns are proposed that are able to drive the evaluators in the analysis of an e-learning application.     

Design,Synthesis, and Biological Evaluation of Tetrahydro‐β‐carboline Derivatives as Selective Sub‐Nanomolar Gelatinase Inhibitors

Targeting matrix metalloproteinases (MMPs) is a pursued strategy for treating several pathological conditions, such as multiple sclerosis and cancer. Herein, a series of novel tetrahydro‐β‐carboline derivatives with outstanding inhibitory activity toward MMPs are present. In particular, compounds 9 f , 9 g , 9 h and 9 i show sub‐nanomolar IC₅₀ values. Interestingly, compounds 9 g and 9 i also provide remarkable selectivity toward gelatinases; IC₅₀=0.15 nm for both toward MMP‐2 and IC₅₀=0.63 and 0.58 nm , respectively, toward MMP‐9. Molecular docking simulations, performed by employing quantum mechanics based partial charges, shed light on the rationale behind binding involving specific interactions with key residues of S1′ and S3′ domains. Taken together, these studies indicate that tetrahydro‐β‐carboline represents a promising scaffold for the design of novel inhibitors able to target MMPs and selectively bias gelatinases, over the desirable range of the pharmacokinetics spectrum.