ATP-sensitive cation-channel in wheat (triticum durum Desf.): Identification and characterization of a plant mitochondrial channel by patch-clamp

Indirect evidence points to the presence of K + channels in plant mitochondria. In the present study, we report the results of the first patch clamp experiments on plant mitochondria. Single-channel recordings in 150 mM potassium gluconate have allowed the biophysical characterization of a channel with a conductance of 150 pS in the inner mitochondrial membrane of mitoplasts obtained from wheat (Triticum durum Desf.). The channel displayed sharp voltage sensitivity, permeability to potassium and cation selectivity. ATP in the mM concentration range completely abolished the activity. We discuss the possible molecular identity of the channel and its possible role in the defence mechanisms against oxidative stress in plants

VDAC3 as a sensor of oxidative state of the intermembrane space of mitochondria: the putative role of cysteine residue modifications

Voltage-Dependent Anion selective Channels (VDAC) are pore-forming mitochondrial outer membrane proteins. In mammals VDAC3, the least characterized isoform, presents a set of cysteines predicted to be exposed toward the intermembrane space. We find that cysteines in VDAC3 can stay in different oxidation states. This was preliminary observed when, in our experimental conditions, completely lacking any reducing agent, VDAC3 presented a pattern of slightly different electrophoretic mobilities. This observation holds true both for rat liver mitochondrial VDAC3 and for recombinant and refolded human VDAC3. Mass spectroscopy revealed that cysteines 2 and 8 can form a disulfide bridge in native VDAC3. Single or combined site-directed mutagenesis of cysteines 2, 8 and 122 showed that the protein mobility in SDS-PAGE is influenced by the presence of cysteine and by the redox status. In addition, cysteines 2, 8 and 122 are involved in the stability control of the pore as shown by electrophysiology, complementation assays and chemico-physical characterization. Furthermore, a positive correlation between the pore conductance of the mutants and their ability to complement the growth of porin-less yeast mutant cells was found. Our work provides evidence for a complex oxidation pattern of a mitochondrial protein not directly involved in electron transport. The most likely biological meaning of this behavior is to buffer the ROS load and keep track of the redox level in the intermembrane space, eventually signaling it through conformational change

Development and life cycle assessment of agricultural waste materials as thermal insulation for dwellings in Thailand

This thesis investigates the use of agricultural waste materials as alternative raw material for thermal insulation for dwellings in Thailand. A literature review carried out to study the potential of several agricultural waste materials suggested that coconut husks, bagasse and rice hulls offer high potential due to their availability in Thailand, low thermal conductivity, and ability to be made into low density boards. The Life Cycle Assessment (LCA) was carried out to compare the environmental and health impacts of thermal insulation boards made from agricultural waste materials currently available on the market with conventional insulation materials. This suggested that the currently available thermal insulation boards made from agricultural waste materials generally had more environmental and health impacts than conventional insulation materials. However, coconut husks and bagasse showed potential; the environmental and health impacts of the insulation boards made from these materials were low and could be lower provided that they were produced with lower thermal conductivity and lower density and without chemical binder. Low-density binderless thermal insulation boards were then developed from coconut husks and bagasse using a hot pressing method with varying hot pressing conditions. The results showed that board density, hot pressing temperature and pressing time were associated with the physical properties of both coconut husk and bagasse insulation boards, including modulus of rupture, modulus of elasticity and internal bond. It was also found that while both binderless coconut and bagasse insulation boards had thermal conductivity values in the same range as those of conventional insulation materials, the binderless bagasse insulation boards had better mechanical properties than coconut boards. Binderless bagasse insulation boards produced at a density of 350 kg/m3 treated at a hot pressing temperature of 200°C for 13 min could satisfy the requirements of JIS A 5905:2003 Insulation Fibreboards except for thickness swelling. LCA was carried out for two potential bagasse insulation boards (350 and 230 kg/m3 density) in comparison with conventional insulation materials. The results suggested that a board of 230 kg/m3 density offers lower environmental impacts than cellulose, fibreglass and rock wool insulations. The outcome of this study indicates that bagasse, an agricultural waste material, has significant potential as alternative raw material for thermal insulation production in the context of Thailand.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Poly(vinyl chloride) Coupling with UV Laser Radiation: Comparison between Polymer Absorbers and Nanoparticles to Increase Efficiency for Laser Ablation Propulsion

Among the wide variety of applications of polymers, their use as targets for laser ablation propulsion has recently gained interest. Poly(vinyl chloride) (PVC) showed promising propulsion properties that can be related to its well-defined thermal decomposition path. However, strategies are needed to increase the momentum generation efficiency with laser radiation. To increase the energetic efficiency in the laser generation of a mechanical impulse, optical and thermodynamic properties must be properly tuned so that the ablation threshold fluence (Fth) is reduced. In this work, we compare two strategies to increase the optical absorption of PVC in the UV region. One is based on embedding carbon nanoparticles (CNPs) in the PVC matrix, whereas the other relies on mixing PVC with poly(styrene sulfonate) acting as a chromophore. Uniform polymer films of 50 μm thickness are fabricated using a multilayer spin-coating technique. Samples are then tested by measuring the laser-generated impulse using a ballistic pendulum under the fluence range from 0.2 to 3 J/cm2 and values of Fth are extracted. These results are discussed from the point of view of optical and thermodynamic properties of the modified PVC, concluding that the localized optical absorption given by CNP is the most efficient strategy in the optical-to-mechanical energy conversion via laser-induced ablation of the polymer film