The bell-shaped rate-pH curve coupled to production of base in the urea-urease reaction was utilized to give feedback-driven behavior: an acid-to-base pH clock (a kinetic switch), bistability and hysteresis between an acid/base state when the initial pH was adjusted by a strong acid, and aperiodic pH oscillations when the initial pH was adjusted by a weak acid in an open reactor. A simple model of the reaction reproduced most of the experimental results and provided insight into the role of self-buffering in the dynamics. This reaction suggests new possibilities in the development of biocompatible feedback to couple to pH-sensitive processes for bioinspired applications in medicine, engineering, or materials science.

The urease-catalyzed hydrolysis of urea displays feedback that results in a switch from acid (pH ~3) to base (pH ~9) after a controllable period of time (from 10 to >5000 s). Here we show that the spatially distributed reaction can support pH wave fronts propagating with a speed of the order of 0.1-1 mm min(-1). The experimental results were reproduced qualitatively in reaction-diffusion simulations including a Michaelis-Menten expression for the urease reaction with a bell-shaped rate-pH dependence. However, this model fails to predict that at lower enzyme concentrations, the unstirred reaction does not always support fronts when the well-stirred reaction still rapidly switches to high pH.

Small-molecule amphiphiles such as aspirin have unique properties arising from a combination of an aromatic hydrophobic part and a hydrophilic part. We show that crystals of aspirin are capable of generating convective flows at the air-aqueous interface from both Marangoni effects (through weak surface activity) and capillarity (surface deformations). The flow-driven motion of millimeter-sized crystals was found to depend on the presence of other ions in solution as well as the distance and orientation of the crystals. The interactions lead to the formation of groups of two or more crystals that also underwent motion. The convective flows created by small amphiphile crystals might be exploited in the dynamic self-organization of particles at interfaces.

The aim of this study was to compare the efficiency of DNA extraction from water as well as from blood samples spiked with A. fumigatus spores, using selected commercial kits. Extraction of DNA according to manufacturer's protocols was preceded by blood cells lysis and disruption of fungal cells by enzymatic digestion or bead beating. The efficiency of DNA extraction was measured by PCR using Aspergillus-specific primers and SYBR Green I dye or TaqMan probes targeting 28S rRNA gene. All methods allowed the detection of Aspergillus at the lowest tested density of water suspensions of spores (10 1 cells/ml). The highest DNA yield was obtained using the ZR Fungal/Bacterial DNA kit, YeastStar Genomic DNA kit, and QIAamp DNA Mini kit with mechanical cell disruption. The ZR Fungal/Bacterial DNA and YeastStar kits showed the highest sensitivity in examination of blood samples spiked with Aspergillus (100 % for the detection of 10 2 spores and 75 % for 10 1 spores). Recently, the enzymatic method ceased to be recommended for examination of blood samples for Aspergillus, thus ZR Fungal/ Bacterial DNA kit and QIAamp DNA Mini kit with mechanical cell disruption could be used for extraction of Aspergillus DNA from clinical samples.