Modulation of non-bilayer lipid phases and the structure and functions of thylakoid membranes: effects on the water-soluble enzyme violaxanthin de-epoxidase

The role of non-bilayer lipids and non-lamellar lipid phases in biological membranes is an enigmatic problem of membrane biology. Non-bilayer lipids are present in large amounts in all membranes; in energy-converting membranes they constitute about half of their total lipid content-yet their functional state is a bilayer. In vitro experiments revealed that the functioning of the water-soluble violaxanthin de-epoxidase (VDE) enzyme of plant thylakoids requires the presence of a non-bilayer lipid phase. P-31-NMR spectroscopy has provided evidence on lipid polymorphism in functional thylakoid membranes. Here we reveal reversible pH- and temperature-dependent changes of the lipid-phase behaviour, particularly the flexibility of isotropic non-lamellar phases, of isolated spinach thylakoids. These reorganizations are accompanied by changes in the permeability and thermodynamic parameters of the membranes and appear to control the activity of VDE and the photoprotective mechanism of non-photochemical quenching of chlorophyll-a fluorescence. The data demonstrate, for the first time in native membranes, the modulation of the activity of a water-soluble enzyme by a non-bilayer lipid phase

Lipid Polymorphism of the Subchloroplast-Granum and Stroma Thylakoid Membrane-Particles. I. P-31-NMR Spectroscopy

Build-up of the energized state of thylakoid membranes and the synthesis of ATP are warranted by organizing their bulk lipids into a bilayer. However, the major lipid species of these membranes, monogalactosyldiacylglycerol, is a non-bilayer lipid. It has also been documented that fully functional thylakoid membranes, in addition to the bilayer, contain an inverted hexagonal (H-II) phase and two isotropic phases. To shed light on the origin of these non-lamellar phases, we performed P-31-NMR spectroscopy experiments on sub-chloroplast particles of spinach: stacked, granum and unstacked, stroma thylakoid membranes. These membranes exhibited similar lipid polymorphism as the whole thylakoids. Saturation transfer experiments, applying saturating pulses at characteristic frequencies at 5 degrees C, provided evidence for distinct lipid phases-with component spectra very similar to those derived from mathematical deconvolution of the P-31-NMR spectra. Wheat-germ lipase treatment of samples selectively eliminated the phases exhibiting sharp isotropic peaks, suggesting easier accessibility of these lipids compared to the bilayer and the H-II phases. Gradually increasing lipid exchanges were observed between the bilayer and the two isotropic phases upon gradually elevating the temperature from 5 to 35 degrees C, suggesting close connections between these lipid phases. Data concerning the identity and structural and functional roles of different lipid phases will be presented in the accompanying paper

Lipid polymorphism in chloroplast thylakoid membranes - as revealed by 31P-NMR and time-resolved merocyanine fluorescence spectroscopy

Chloroplast thylakoid membranes contain virtually all components of the energy-converting photosynthetic machinery. Their energized state, driving ATP synthesis, is enabled by the bilayer organization of the membrane. However, their most abundant lipid species is a non-bilayer-forming lipid, monogalactosyl-diacylglycerol; the role of lipid polymorphism in these membranes is poorly understood. Earlier 31P-NMR experiments revealed the coexistence of a bilayer and a non-bilayer, isotropic lipid phase in spinach thylakoids. Packing of lipid molecules, tested by fluorescence spectroscopy of the lipophilic dye, merocyanine-540 (MC540), also displayed heterogeneity. Now, our 31P-NMR experiments on spinach thylakoids uncover the presence of a bilayer and three nonbilayer lipid phases; time-resolved fluorescence spectroscopy of MC540 also reveals the presence of multiple lipidic environments. It is also shown by 31P-NMR that: (i) some lipid phases are sensitive to the osmolarity and ionic strength of the medium, (ii) a lipid phase can be modulated by catalytic hydrogenation of fatty acids and (iii) a marked increase of one of the non-bilayer phases upon lowering the pH of the medium is observed. These data provide additional experimental evidence for the polymorphism of lipid phases in thylakoids and suggest that non-bilayer phases play an active role in the structural dynamics of thylakoid membranes

Biomass gasification in an updraft fixed bed gasifier

Uporaba biomase za proizvodnjo elektrike in energije ter sintezno novih kemikalij postaja čedalje bolj pomembna zaradi mnogoterih izzivov povezanih s fosilnimi viri. Za uspešno pretvorbo biomase se pojavlja vrsta naprednih tehnologij, ki lahko učinkovito in ekonomično pretvorijo odpadne tokove v bio-osnovane surovine. Eden izmed vmesnih produktov je sintezni plin, s katerim lahko pridobimo uporabne kemikalije ali proizvedemo električno energijo in toploto, pridobivati pa ga je mogoče s postopkom uplinjanja. V sklopu diplomske naloge smo izdelali laboratorijsko napravo za uplinjanje, ki nam je omogočala izvedbo meritev uplinjanja biomase. Naprava za uplinjanje je protitočne izvedbe in ima sposobnost uplinjanja raznolikih goriv. Osredotočili smo se na različne intervale doziranja goriva in obratovanje pri različnih razmernikih zraka. Glavni cilj meritev je bil pridobiti podatke o temperaturnem profilu, ki se vzpostavi v postelji goriva in o sestavi produktnega plina. Ti podatki pripomorejo pri opisu razmer, ki se vzpostavijo v napravi. Z analizo podatkov smo potrdili ustreznost zasnove naprave za uplinjanje in razvili metodo, s katero je možno spremljati višino postelje goriva na podlagi temperaturnega profila v napravi.The use of biomass for generating electricity, energy and new synthetic chemicals is becoming increasingly important, due to the challenges associated with fossil fuels. For successful conversion of biomass, a range of advanced technologies are emerging that can efficiently and economically convert waste streams into bio-based feedstocks. One of the conversion intermediate products, that is produced with gasification, is synthesis gas, which can be used to produce useful chemicals or generate electricity and heat. As part of the thesis, we built a laboratory gasification device that allowed us to execute measurements of biomass gasification. The gasification device is of updraft design and is capable of gasifying a wide variety of fuels. We focused on different fuel dosing intervals and operation at different equivalence ratios. The main goals of the measurements were to obtain information about established temperature profile in the fuel bed and composition of the product gas. This information helps us to describe the conditions in the device. By analysing the data, we have confirmed the adequacy of the gasification device design and developed a method to monitor the fuel bed height based on the temperature profile in the device

Sustainable alkali-activated slag binders based on alternative activators sourced from mineral wool and glass waste

In the present study, four different locally available waste glass materials (bottle glass-BG, glass wool-GW, stone wool-SW and cathode-ray tube glass-CRTG) were treated with hot concentrated potassium hydroxide (KOH) in order to obtain alternative alkali activators (AAAs). We evaluated the suitability of the solutions obtained for use as AAAs in the production of AAMs. AAMs were prepared using electric arc furnace slag and selected AAAs with a higher content of dissolved Si. We evaluated the performance of the AAMs in comparison to that of slags activated with KOH or potassium-silicate (K-silicate). The compressive strength of the AAMs prepared with KOH-based AAAs were high when Si and Al were simultaneously abundant in the AAA (9.47 MPa when using the activator sourced from the CRTG), and low with the addition of KOH alone (1.97 MPa). The AAM produced using commercial K-silicate yielded the highest compressive strength (27.7 MPa). The porosity of the KOH-based AAM was lowest when an alternative BG-based activator was used (24.1%), when it was similar to that of the AAM prepared with a K-silicate. The BG-based activator had the highest silicon content (33.1 g/L), and NMR revealed that Si was present in the form of Q0, Q1 and Q2. The concentrations of toxic trace elements in the AAAs used for alkali activation of the slag were also determined, and leaching experiments were performed on the AAMs to evaluate the immobilisation potential of alkali-activated slag. In the SW AAAs the results show acceptable concentrations of trace and minor elements with respect to the regulations on waste disposal sites, while in the activators prepared from BG, CRTG and GW some elements exceeded the allowable limits (Pb, Ba, Sb, and As)

Pedagogy 1:1 in higher education

The use of ICT in education has changed substantially over the last two decades. The development of new technologies has enabled us, the users, to mature and gain experience. The introduction of ICT in the educational process at the same time means a change of the teachers\u27 role. The teacher appears in the role of a mentor who directs the activities of the learner. There has been a change in the teacher preparation to teach. He should provide both the content as well as technical support and to create a suitable learning environment. The way of teaching in the natural science and engineering education is specific due to the need of transfer knowledge into the practice. The nature of work in this kind of education requires more experimental work, based on individual learning process. There are many different implementation options of laboratory exercises that advantageously incorporate ICT into the nature of their work. The most popular in engineering education are two different types of laboratories: Simulation (virtual) and Remote controlled (online) labs, defined by Balamuralithara and Woods (2009). A remote controlled laboratory for conducting remote experiments at the University of Maribor, Faculty of Mechanical Engineering was developed. Development of the remote lab was carried out as an exploratory work of the group of students and professors. The lab was developed in the following three phases: development of the construction with corresponding technical documentation, development of the control system and development of the system for remote control of a lift. The successful student project is evident through the applicability of the developed laboratory that serves as a great tool for studying and offers all the benefits of ICT