Al és Ti alapú tömbi amorf és nanoszerkezetű kompozitok előállítása és vizsgálata = Preparation and investigation of Al and Ti based amorphous and nanocrystalline bulk comopsites

A Ti-Al alapú ötvözetek magas hőmérsékleten is nagy szilárdágú és kis sűrűségű szerkezeti anyagok. Az eddig használatos technológiák helyett, mi két új technológiát alkalmaztunk: az olvadékból való gyorshűtést és a mechanikai ötvözést. Sajnálatos módon Al-Ti alapú fémüveget nem sikerült előállítani, mert hiányzik a mély eutektikum a fázisdiagramban. Ezért csak a mechanikai ötvözés maradt és ezzel a módszerrel állítottunk elő egy sor amorf ötvözetet: Al50Ti50, Al50Ti45Ni5, Al50Ti40Ni10, Al55Ti35Cr15 és Al45Ti40Cr15. Ezeket az amorf porokat kompaktáltuk és különböző vizsgálatoknak vetettük alá. Kísérletek vannak folyamatban, hogy az amorf porokat magas hőmérsékletű védőbevonatként alkalmazzuk. Külön – külön, mind Al, mind Ti alapon lehet fémüveg szalagokat előállítani gyorshűtéssel. Mi az Al alapú fémüvegekre koncentráltunk. Az irodalomból ismert volt az általában ternér összetételű (Al85-92RE2-12Ni0-12) fémüveg, ahol a ritkaföldfém az amorfizáló ötvöző elem. Kísérletileg bizonyítottuk, hogy vannak más amorfizáló elemek is melyek a RE elemektől balra (Ca és Sr), jobbra (Nb és Ta) valamint alatta (Urán) helyezkednek el. Egy fontos, elektronszámhoz kötődő szabályt állapítottunk meg, miszerint a maximális szilárdságot e/a = 6,5 értéknél érjük el az egyfázisú amorf ötvözetek esetében. Azt találtuk, hogy Al-Ti alapon csak akkor kapunk nagyentrópiás ötvözetet, ha a 3d elemekből közel 50 at. % -ot adunk hozzá. 3 diplomamunka és egy PhD dolgozat készült el. | The Ti-Al alloys offer higher temperature capability along with low density and high stiffness. Instead of the usual technology, we have proposed two different routes based on melt spinning and mechanical alloying. Amorphous phase can not be obtained by rapid quenching from the melt due to the lack of deep eutectic, which prevent the sufficient under-cooling by melt spinning technique. This is why mechanical alloying has been used to prepare a series of Al-Ti based amorphous compositions: Al50Ti50, Al50Ti45Ni5, Al50Ti40Ni10, Al55Ti35Cr15, Al45Ti40Cr15. This amorphous powder have been compacted and investigated. Experiments are continuing to use this powder as wear and high temperature resistant coating material. Separately, both Ti and Al based amorphous ribbons can be obtained by melt spinning supposing that appropriate amorphous forming element are added. We have focused on Al based amorphous alloys extending the compositional area known in the literature and based on RE amorphizing elements (Al85-92RE2-12Ni0-12). We have proved that elements situated in the periodic table at the left (Ca and Sr), at the right (Nb and Ta) and below (U) to the RE elements are also amorphizing elements. An important electronic rule was established: for the one-phase amorphous alloys the maximal strength is achieved around e/a = 6.5. Al-Ti based high entropy alloys could be prepared with addition of more then 50 at% 3d elements. 3 diploma work and 1 PhD dissertations have been prepared

Wide-line NMR and DSC studies on intrinsically disordered p53 transactivation domain and its helically pre-structured segment

Wide-line 1H NMR intensity and differential scanning calorimetry measurements were carried out on the intrinsically disordered 73-residue full transactivation domain (TAD) of p53 tumor suppressor protein and two peptides, one a wild type p53 TAD peptide with a helix pre-structuring property and a mutant peptide with a disabled helix-forming propensity in order to characterize their water and ion binding characteristics. By quantifying the number of hydrate water molecules, we provide microscopic description for the interactions of water with a wild-type p53 TAD and two p53 TAD peptides. The results provide direct evidence that intrinsically disordered proteins (IDPs) and a less structured peptide not only have a higher hydration capacity than globular proteins but also are able to bind a larger amount of charged solute ions

DSC approach for the investigation of mobile water fractions in aqueous solutions of NaCl and tris buffer

The fraction of mobile (unfrozen) water during phase transitions of NaCl-H2O solution and tris(hydroxymethyl)aminomethane (Tris) buffer solution has been determined by differential scanning calorimetry (DSC). Measurements were carried out in the temperature range between -50 and +30 degrees C with a heating rate of 2 K min(-1). The fraction of mobile water was estimated from the enthalpy of melting of the different frozen phases present in aqueous solution samples. Results are supplemented by proton NMR intensity measurements in the same temperature range. A small endothermic peak was detected in the DSC curves at the same temperature where the change in the NMR intensity occurs. We assume that activation/deactivation of rotational molecular motion of hydration water molecules occurs at the steps of the NMR intensity at higher and lower temperatures during heating and cooling, respectively. The rotational motion is probably the initial stage of the eutectic phase separation. Tris additive to NaCl solution causes thermal shifts of the small endothermic peak and in the related NMR intensity. These qualitative differences indicate interactions of Na+ and Cl- ions with the small organic molecule constituents. (c) 2007 Elsevier B.V. All rights reserved

Structural disorder and local order of hNopp140

Human nucleolar phosphoprotein p140 (hNopp 140) is a highly phosphorylated protein inhibitor of casein kinase 2 (CK2). As in the case of many kinase-inhibitor systems, the inhibitor has been described to belong to the family of intrinsically disordered proteins (IDPs), which often utilize transient structural elements to bind their cognate enzyme. Here we investigated the structural status of this protein both to provide distinct lines of evidence for its disorder and to point out its transient structure potentially involved in interactions and also its tendency to aggregate. Structural disorder of hNopp140 is apparent by its anomalous electrophoretic mobility, protease sensitivity, heat stability, hydrodynamic behavior on size-exclusion chromatography, 1HNMR spectrum and differential scanning calorimetry scan. hNopp140 has a significant tendency to aggregate and the change of its circular dichroism spectrum in the presence of 0–80% TFE suggests a tendency to formlocal helical structures.Wide-line NMRmeasurements suggest the overall disordered character of the protein. In all, our data suggest that this protein falls into the pre-molten globule state of IDPs, with a significant tendency to become ordered in the presence of its partner as demonstrated in the presence of transcription factor IIB (TFIIB)

Interfacial Water at Protein Surfaces: Wide-Line NMR and DSC Characterization of Hydration in Ubiquitin Solutions

Wide-line 1H-NMR and differential scanning calorimetry measurements were done in aqueous solutions and on lyophilized samples of human ubiquitin between −70°C and +45°C. The measured properties (size, thermal evolution, and wide-line NMR spectra) of the protein-water interfacial region are substantially different in the double-distilled and buffered-water solutions of ubiquitin. The characteristic transition in water mobility is identified as the melting of the nonfreezing/hydrate water. The amount of water in the low-temperature mobile fraction is 0.4 g/g protein for the pure water solution. The amount of mobile water is higher and its temperature dependence more pronounced for the buffered solution. The specific heat of the nonfreezing/hydrate water was evaluated using combined differential scanning calorimetry and NMR data. Considering the interfacial region as an independent phase, the values obtained are 5.0–5.8 J·g−1·K−1, and the magnitudes are higher than that of pure/bulk water (4.2 J·g−1·K−1). This unexpected discrepancy can only be resolved in principle by assuming that hydrate water is in tight H-bond coupling with the protein matrix. The specific heat for the system composed of the protein molecule and its hydration water is 2.3 J·g−1·K−1. It could be concluded that the protein ubiquitin and its hydrate layer behave as a highly interconnected single phase in a thermodynamic sense