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21.
Abscisic acid-regulated water channels and their role in plant acclimation and tolerance to water stress
Christina Paparokidou, 2014, master's thesis

Abstract: The yield of worldwide crop production has already been negatively affected by high salinity and water deficiency prevailing in many of the cultivated lands (Yan et al., 2013; Serraj et al., 2011; Golldack et al., 2011). Consequently, reduced crop production is a major problem in terms of food sustainability world-wide (Spiertz, 2013). Plants as sessile organisms have to dynamically and constantly cope with various types of stress in their environment. Although stress perception by plants remains elusive (Gan et al., 2010; Shachar-Hill et al., 2013; Wu et al., 2012), the stress-responsive mechanisms that follow are starting to be better understood (Wasilewska et al., 2008; Kohli et al., 2013; Osakabe et al., 2013). Abscisic acid (ABA) is a central plant hormone produced in response to abiotic stress and has been shown to play important roles in plant acclimation and tolerance towards stress (Nakashima and Yamaguchi-Shinozaki, 2013; Osakabe et al., 2014). ABA accumulation triggers the expression of a plethora of genes within the plant cell (Liu et al., 2013). The ABA-regulated genes are various in nature, including enzymes involved in osmolyte and cell wall biosynthesis, detoxifying enzymes, enzymes for fatty acid metabolism, proteinase inhibitors, macromolecule protective proteins, lipid transfer proteins, ion transporters and water channels, transcription factors (TFs), protein kinases, protein phosphatases and proteinases (Roychoudhury et al., 2013; Rock, 2000). In this literature review the role of water channel-encoding genes, namely aquaporins (AQPs), in plant water stress will be discussed. The aim of this study is to understand how ABA-regulated AQPs are able to contribute to the plant’s tolerance and acclimation during water stress. The knowledge gained from this study is important for the engineering of salt and drought resistant crops within the modern agricultural context, thus contributing to world’s crop sustainable production (Jacobs et al., 2011; Park et al., 2005; Kujur et al., 2013).
Keywords: Abscisic acid (ABA), ABA-regulated genes, aquaporins (AQPs), ABA-regulated AQPs, ABA-dependent water stress, root hydraulic conductance (Lpr), leaf hydraulic conductance (Kleaf), stomatal conductance (gs), AQP bioengineering
Published in RUNG: 03.05.2022; Views: 1589; Downloads: 0
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Implicit water model within the Zimm-Bragg approach to analyze experimental data for heat and cold denaturation of proteins
Artem Badasyan, Sh. A. Tonoyan, Matjaž Valant, Jože Grdadolnik, 2021, original scientific article

Abstract: Studies of biopolymer conformations essentially rely on theoretical models that are routinely used to process and analyze experimental data. While modern experiments allow study of single molecules in vivo, corresponding theories date back to the early 1950s and require an essential update to include the recent significant progress in the description of water. The Hamiltonian formulation of the Zimm-Bragg model we propose includes a simplified, yet explicit model of water-polypeptide interactions that transforms into the equivalent implicit description after performing the summation of solvent degrees of freedom in the partition function. Here we show that our model fits very well to the circular dichroism experimental data for both heat and cold denaturation and provides the energies of inter- and intra- molecular H-bonds, unavailable with other processing methods. The revealed delicate balance between these energies determines the conditions for the existence of cold dena- turation and thus clarifies its absence in some proteins.
Keywords: protein folding, cold denaturation, water, Zimm-Bragg model
Published in RUNG: 06.05.2021; Views: 2405; Downloads: 15
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25.
Porous polycalix[n]arenes as environmental pollutant removers
Salma Abubakar, Tina Škorjanc, Dinesh Shetty, Ali Trabolsi, 2021, review article

Abstract: A new and innovative class of calixarene-based polymers emerged as adsorbents for a variety of compounds and ions in solution and vapor media. These materials take advantage of the modifiable rims and hydrophobic cavities of the calixarene monomers, in addition to the porous nature of the polymeric matrix. With main-chain calixarenes’ function as supramolecular hosts and the polymers’ high surface areas, polycalixarenes can effectively encapsulate target analytes. This feature is particularly useful for environmental remediation as dangerous and toxic molecules reversibly bind to the macrocyclic cavity, which facilitates their removal and enables repeated use of the polymeric sorbent. This Spotlight touches on the unique characteristics of the calixarene monomers and discusses the synthetic methods of our reported calixarene-based porous polymers, including Sonogashira–Hagihara coupling, and diazo and imine bond formation. It then discusses the promising applications of these materials in adsorbing dyes, micropollutants, iodine, mercury, paraquat, and perfluorooctanoic acid (PFOA) from water. In most cases, these reports cover materials that outperform others in terms of recyclability, rates of adsorption, or uptake capacities of specific pollutants. Finally, this Spotlight addresses the current challenges and future aspects of utilizing porous polymers in pollution treatment.
Keywords: calixarene, polycalixarenes, porous polymers, pollutant removal, water purification
Published in RUNG: 09.04.2021; Views: 2598; Downloads: 0
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Atomic layer deposition for the photoelectrochemical applications
Nadiia Pastukhova, Andraž Mavrič, Yanbo Li, 2021, review article

Abstract: Substantial progress has been made in the photoelectrochemical (PEC) field to understand the photoelectrode behavior, semiconductor‐electrolyte interface, and photocorrosion, enabling new photoelectrode architectures with higher photocurrent, reduced photovoltage losses, and longer lifetime. Nevertheless, for practical PEC applications additional efforts are still needed to optimize all components of the photoelectrodes, including the light absorbing semiconductors, the layers for charge extraction, charge transfer, corrosion protection, and catalysis. In this regard, atomic layer deposition (ALD) offers new opportunities due to the monolayer‐by‐monolayer deposition approach, allowing preparation of conformal films with precisely controlled thickness and composition. As the ALD instruments are becoming widely accessible, this review aims to make an overview of the applications for photoelectrodes fabrication. The deposition of semiconductors onto flat and nano‐textured substrates, the deposition of ultrathin interlayers to ease charge transport by energy band alignment and surface states passivation, the deposition of corrosion protection layers, and finally, the possibilities for high catalyst dispersion is presented.
Keywords: atomic layer deposition, charge recombination, charge transfer, photocorrosion, photoelectrochemical water splitting
Published in RUNG: 25.02.2021; Views: 2562; Downloads: 139
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Growth of MoSe2 electrocatalyst from metallic molybdenum nanoparticles for efficient hydrogen evolution : Growth of MoSe2 electrocatalyst from metallic molybdenum nanoparticles for efficient hydrogen evolution
Takwa Chouki, Boriana Donkova, Burhancan Aktarla, Plamen Stefanov, Saim Emin, 2021, original scientific article

Abstract: Molybdenum diselenide (MoSe2) is an emerging alternative to platinum-group-metal electrocatalysts for the hydrogen evolution reaction (HER). Herein, the chemical vapor deposition (CVD) approach was demonstrated to be a successful route to grow MoSe2 thin films using colloidal molybdenum nanoparticles (Mo NPs). T
Keywords: Water splitting, electrocatalyst, MoSe2
Published in RUNG: 15.01.2021; Views: 2600; Downloads: 0
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Polysaccharide-based films and coatings for food packaging: A review.
Patricia Cazón, Gonzalo Velazquez, Jose A. Ramirez, Manuel Vazquez, 2017, review article

Abstract: The accumulation of synthetic plastics, mainly from food packaging, is causing a serious environmental problem. It is driving research efforts to the development of biodegradable films and coatings. The biopolymers used as raw material to prepare biodegradable films should be renewable, abundant and low-cost. In some cases, they can be obtained from wastes. This review summarizes the advances in polysaccharide-based films and coatings for food packaging. Among the materials studied to develop biodegradable packaging films and coatings are polysaccharides such as cellulose, chitosan, starch, pectin and alginate. These polysaccharides are able to form films and coatings with good barrier properties against the transport of gases such as oxygen and carbon dioxide. On the other hand, tensile strength and percentage of elongation are important mechanical properties. Desirable values of them are required to maintain the integrity of the packed food. The tensile strength values showed by polysaccharide-based films vary from each other, but some of them exhibit similar values to those observed in synthetic polymers values. For example, tensile strength values of films based on high amylose starch or chitosan are comparable to those values found in high-density polyethylene films. The values of percentage of elongation are the main concern, which are far from the desirable values found for synthetic polymers. Researchers are studying combinations of polysaccharides with other materials to improve the barrier and mechanical properties in order to obtain biopolymers that could replace synthetic polymers. Functional polymers with antimicrobial properties, as that the case of chitosan, are also being studied.
Keywords: Cellulose, Chitosan, Starch, Water vapour permeability, Tensile strength, Percentage of elongation at break
Published in RUNG: 14.12.2020; Views: 2665; Downloads: 0
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Novel composite films based on cellulose reinforced with chitosan and polyvinyl alcohol: Effect on mechanical properties and water vapour permeability
Patricia Cazón, Manuel Vazquez, Gonzalo Velazquez, 2018, original scientific article

Abstract: Novel composite films were prepared by dissolving microcrystalline cellulose (3–5% w/w) in NaOH/urea solution, followed by coagulation in acetic acid solution. The regenerated cellulose films were immersed in chitosan-polyvinyl alcohol solutions at concentrations of 0–1% w/w and 0–4% w/w, respectively. Tensile strength, percentage of elongation at break, Young's modulus and water vapour permeability were measured to assess the effect of each compound on the mechanical and barrier properties. Polynomial models were obtained to evaluate the effect of the formulation on the measured properties. The microstructure was analysed by scanning electron microscopy. Results showed tensile strength values in the range 27.75–78.48 MPa, similar to usual synthetic polymer films. Percentage of elongation at break ranged from 0.98 to 12.82%, increasing when polyvinyl alcohol and chitosan increased. Young's modulus ranged from 2727.04 to 4217.25 MPa, showing higher values than pure chitosan and polyvinyl alcohol films. The highest value was reached combining cellulose and polyvinyl alcohol without chitosan. The water vapour permeability (1.78·10−11-4.24·10−11 g/m s Pa) showed 2 orders of magnitude higher than that of synthetic polymers, but lower than pure chitosan and polyvinyl alcohol films. Results showed that it is feasible to obtain cellulose-chitosan-polyvinyl alcohol composite films with improved mechanical properties and water vapour permeability.
Keywords: Regenerated cellulose, Tensile strength, Elongation at break, Young's modulus, Water vapour permeability
Published in RUNG: 14.12.2020; Views: 2664; Downloads: 0
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