Abstract Trypsin is a serine protease with widespread applications, including protein sequencing ... more Abstract Trypsin is a serine protease with widespread applications, including protein sequencing and trypsin mass fingerprinting. In the present study, the storage of trypsin in acidic conditions significantly affected the recovery of activity (40%) after 7 freeze–thaw cycles. Further, trypsin lost parts of its native secondary structure elements, which resulted in a 10% increase in β-sheet content (band maximum detected at a frequency of 1634 cm−1 in the Fourier transform infrared (FT-IR) spectrum) indicative of freezing-induced denaturation of the protein. The cold storage of trypsin in ammonium bicarbonate (pH 8.2) with the addition of cryoprotectants, such as glycerol or lysine, led to protein stabilization (complete secondary structure content preservation was detected by FT-IR), higher activity recovery (>90%) and modest autolysis ( 90%) was also detected with the addition of propylene glycol and polyethylene glycol, saccharides and arginine. Nevertheless, trypsin stored at pH 8.2 with the addition of glycerol or lysine was as efficient as untreated trypsin in the trypsin mass fingerprinting analysis of BSA, suggesting that the cold storage of trypsin in slightly alkaline conditions with the addition of cryoprotectants could prolong its shelf life.
Thermal decomposition of Co(II) complex with N-benzyloxycarbonylglycinato ligand, [Co(N-Boc-gly)2... more Thermal decomposition of Co(II) complex with N-benzyloxycarbonylglycinato ligand, [Co(N-Boc-gly)2(H2O)4]?2H2O, in non-isothermal conditions occurs in three complex steps. In order to investigate detail kinetics of first two steps, dehydration and ligand degradation, DTG curves were deconvoluted using product of Gaussian and Lorentzian function. It was shown that process of complex dehydration consists of three, while process of ligand fragmentation consist of five elementary steps. For elementary steps the kinetic triplet (Ea, Z and f(?)) was determinated. Kinetic parameters were obtained by application of IKP method. On the basis of M?lek?s criteria and Sest?k-Berggren's method, Sest?k-Berggren's model, f(?)=?M(1-?)N was suggested for all elementary steps, while Master plot method and Perez- Maqueda criteria confirmed suggested reaction models. The thermodynamic activation parameters were calculated for process of complex dehydration, and lifetime for first elementary step ...
Abstract Thermal stability of amorphous Fe73.5Cu1Nb3Si15.5B7 alloy and its crystallization kineti... more Abstract Thermal stability of amorphous Fe73.5Cu1Nb3Si15.5B7 alloy and its crystallization kinetics and mechanism have been investigated. The alloy is stable up to 748 K, after which it undergoes multi-step crystallization with formation of α-Fe(Si)/Fe3Si, Fe2B, Fe16Nb6Si7, and Fe2Si crystalline phases. The crystallization occurs in two distinct and well separated complex processes, each corresponding to formation of two phases. Activation energy for the formation of the latter two phases is significantly higher, due to their formation out of the previously formed iron–silicon crystalline phase. By comparison of Avrami exponents of experimental system and a hypothetical system where no impingement occurs, the influence of impingement on reaction mechanism was successfully isolated. While the reaction mechanism was suggested as volume diffusion controlled growth of α-Fe(Si) and Fe2B phases, and interface-controlled growth of Fe16Nb6Si7 and Fe2Si phases, impingement plays an increasingly significant role as the crystallization progresses. The determined value of kinetic triplet was used to calculate the alloy lifetime, showing its resistance against crystallization.
The origin of dielectric properties of strontium titanate ceramics is investigated using DFT calc... more The origin of dielectric properties of strontium titanate ceramics is investigated using DFT calculations in periodic system. It was determined that the main factors contributing to the increase in dielectric permittivity are: tetragonal distortion of the normally cubic lattice, and charge imbalance induced displacement of titanium center from its central position. Oxygen vacancies were determined to create significantly larger effects than other types of vacancies, like Ti and SrO. The extent of tetragonal distortion was found to be determined by oxygen vacancy distribution, rather than total concentration: relatively symmetrical distribution of oxygen vacancies resulted in smaller tetragonal distortion of the lattice, and, consequently, smaller increase in dielectric permittivity. Charge imbalance naturally destabilizes the cubic lattice, forcing the Ti-atom out of its central position, resulting in tetragonal lattice with increased dielectric permittivity. The process stabilizes ...
The influence of mechanical activation on the formation, sintering kinetics and morphology was in... more The influence of mechanical activation on the formation, sintering kinetics and morphology was investigated in sintered barium strontium titanate (BST) ceramics with different Ba-to-Sr ratios. Initial powders were mechanically activated for 20 and 120 min, leading to mechano-chemical reaction and formation of BaxSr1-xTiO3 phases. Agglomeration was found to represent an important factor in the process of formation of BaxSr1-xTiO3 phases around 800?C and during sintering. It reduces the effectiveness of mechanical activation on formation of BaxSr1-xTiO3 phases beyond the short period (20 min), while in the process of sintering, prolonged mechanical activation (120 min) leads to a significant reduction in sintering temperature and the corresponding value of activation energy. In addition, all three systems show a phase transformation around 1100?C, attributed to the hexagonal-to-cubic phase transition. Morphology of the final sintered ceramics can be correlated primarily with the state...
A new Ni(ii) complex, [Ni(L)(H2O)] (1), with diethyl 3,3′-(2,2′-(1,1′-(pyridine-2,6-diyl)bis(etha... more A new Ni(ii) complex, [Ni(L)(H2O)] (1), with diethyl 3,3′-(2,2′-(1,1′-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene))bis(hydrazin-1-yl-2-ylidene))bis(3-oxopropanoate) ligand (H2L) was synthesized as a potential chemotherapeutic agent.
Hydrothermal synthesis of amorphous cobalt powder followed by characterization and surface doping... more Hydrothermal synthesis of amorphous cobalt powder followed by characterization and surface doping with palladium and platinum. Thermal stability, microstructure and hydrogen adsorption of doped powders were investigated.
Abstract Trypsin is a serine protease with widespread applications, including protein sequencing ... more Abstract Trypsin is a serine protease with widespread applications, including protein sequencing and trypsin mass fingerprinting. In the present study, the storage of trypsin in acidic conditions significantly affected the recovery of activity (40%) after 7 freeze–thaw cycles. Further, trypsin lost parts of its native secondary structure elements, which resulted in a 10% increase in β-sheet content (band maximum detected at a frequency of 1634 cm−1 in the Fourier transform infrared (FT-IR) spectrum) indicative of freezing-induced denaturation of the protein. The cold storage of trypsin in ammonium bicarbonate (pH 8.2) with the addition of cryoprotectants, such as glycerol or lysine, led to protein stabilization (complete secondary structure content preservation was detected by FT-IR), higher activity recovery (>90%) and modest autolysis ( 90%) was also detected with the addition of propylene glycol and polyethylene glycol, saccharides and arginine. Nevertheless, trypsin stored at pH 8.2 with the addition of glycerol or lysine was as efficient as untreated trypsin in the trypsin mass fingerprinting analysis of BSA, suggesting that the cold storage of trypsin in slightly alkaline conditions with the addition of cryoprotectants could prolong its shelf life.
Thermal decomposition of Co(II) complex with N-benzyloxycarbonylglycinato ligand, [Co(N-Boc-gly)2... more Thermal decomposition of Co(II) complex with N-benzyloxycarbonylglycinato ligand, [Co(N-Boc-gly)2(H2O)4]?2H2O, in non-isothermal conditions occurs in three complex steps. In order to investigate detail kinetics of first two steps, dehydration and ligand degradation, DTG curves were deconvoluted using product of Gaussian and Lorentzian function. It was shown that process of complex dehydration consists of three, while process of ligand fragmentation consist of five elementary steps. For elementary steps the kinetic triplet (Ea, Z and f(?)) was determinated. Kinetic parameters were obtained by application of IKP method. On the basis of M?lek?s criteria and Sest?k-Berggren's method, Sest?k-Berggren's model, f(?)=?M(1-?)N was suggested for all elementary steps, while Master plot method and Perez- Maqueda criteria confirmed suggested reaction models. The thermodynamic activation parameters were calculated for process of complex dehydration, and lifetime for first elementary step ...
Abstract Thermal stability of amorphous Fe73.5Cu1Nb3Si15.5B7 alloy and its crystallization kineti... more Abstract Thermal stability of amorphous Fe73.5Cu1Nb3Si15.5B7 alloy and its crystallization kinetics and mechanism have been investigated. The alloy is stable up to 748 K, after which it undergoes multi-step crystallization with formation of α-Fe(Si)/Fe3Si, Fe2B, Fe16Nb6Si7, and Fe2Si crystalline phases. The crystallization occurs in two distinct and well separated complex processes, each corresponding to formation of two phases. Activation energy for the formation of the latter two phases is significantly higher, due to their formation out of the previously formed iron–silicon crystalline phase. By comparison of Avrami exponents of experimental system and a hypothetical system where no impingement occurs, the influence of impingement on reaction mechanism was successfully isolated. While the reaction mechanism was suggested as volume diffusion controlled growth of α-Fe(Si) and Fe2B phases, and interface-controlled growth of Fe16Nb6Si7 and Fe2Si phases, impingement plays an increasingly significant role as the crystallization progresses. The determined value of kinetic triplet was used to calculate the alloy lifetime, showing its resistance against crystallization.
The origin of dielectric properties of strontium titanate ceramics is investigated using DFT calc... more The origin of dielectric properties of strontium titanate ceramics is investigated using DFT calculations in periodic system. It was determined that the main factors contributing to the increase in dielectric permittivity are: tetragonal distortion of the normally cubic lattice, and charge imbalance induced displacement of titanium center from its central position. Oxygen vacancies were determined to create significantly larger effects than other types of vacancies, like Ti and SrO. The extent of tetragonal distortion was found to be determined by oxygen vacancy distribution, rather than total concentration: relatively symmetrical distribution of oxygen vacancies resulted in smaller tetragonal distortion of the lattice, and, consequently, smaller increase in dielectric permittivity. Charge imbalance naturally destabilizes the cubic lattice, forcing the Ti-atom out of its central position, resulting in tetragonal lattice with increased dielectric permittivity. The process stabilizes ...
The influence of mechanical activation on the formation, sintering kinetics and morphology was in... more The influence of mechanical activation on the formation, sintering kinetics and morphology was investigated in sintered barium strontium titanate (BST) ceramics with different Ba-to-Sr ratios. Initial powders were mechanically activated for 20 and 120 min, leading to mechano-chemical reaction and formation of BaxSr1-xTiO3 phases. Agglomeration was found to represent an important factor in the process of formation of BaxSr1-xTiO3 phases around 800?C and during sintering. It reduces the effectiveness of mechanical activation on formation of BaxSr1-xTiO3 phases beyond the short period (20 min), while in the process of sintering, prolonged mechanical activation (120 min) leads to a significant reduction in sintering temperature and the corresponding value of activation energy. In addition, all three systems show a phase transformation around 1100?C, attributed to the hexagonal-to-cubic phase transition. Morphology of the final sintered ceramics can be correlated primarily with the state...
A new Ni(ii) complex, [Ni(L)(H2O)] (1), with diethyl 3,3′-(2,2′-(1,1′-(pyridine-2,6-diyl)bis(etha... more A new Ni(ii) complex, [Ni(L)(H2O)] (1), with diethyl 3,3′-(2,2′-(1,1′-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene))bis(hydrazin-1-yl-2-ylidene))bis(3-oxopropanoate) ligand (H2L) was synthesized as a potential chemotherapeutic agent.
Hydrothermal synthesis of amorphous cobalt powder followed by characterization and surface doping... more Hydrothermal synthesis of amorphous cobalt powder followed by characterization and surface doping with palladium and platinum. Thermal stability, microstructure and hydrogen adsorption of doped powders were investigated.
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