thermal stability Dotaz Zobrazit nápovědu
Individualizace parametrů dialyzační procedury zahrnuje v současné době i teplotu dialyzačního roztoku. Již dříve bylo ukázáno, že při relativně nižší teplotě dialyzačního roztoku (35 °C) je nižší výskyt hypotenze při dialýze (tj. je vyšší hemodynamická stabilita) než při běžně používané teplotě 37 °C . Přistroj BTM („blood temperature monitor”, Fresenius, Bad Homburg, SRN) umožňuje individualizovat tepelnou bilanci během dialýzy: podle požadavků na teplotní (režim T) či energetickou bilanci (režim E) kontinuálně upravuje teplotu dialyzačního roztoku na principu zpětné vazby po změření teploty krve v arteriálním a venózním setu. Tím vzniká předpoklad pro individualizaci tepelné bilance během mimotělní eliminační metody. Termobilanční studie potvrdily vyšší hemodynamickou stabilitu procedury s negativní energetickou bilancí. Hlavním zodpovědným mechanismem je zvýšení periferní vaskulární rezistence (ve složce arteriální i venózní). K dalším oblastem, ve kterých může řízená termobilance mít vliv na průběh dialýzy, teoreticky patří změna účinnosti, změna biologické odpovědi organismu, změna intravaskulárního objemu, připadně jiné. Úvahy jsou dosud teoretické a tyto oblasti jsou předmětem výzkumu. Je pravděpodobné, že teplotní bilance je hlavním faktorem zodpovědným za hemodynamickou stabilitu i při metodách s konvektivním způsobem přestupu látek při mimotělní eliminaci (izolovaná ultrafiltrace, hemofiltrace a hemodiafiltrace).
Individualization of the parameters of the dialysis procedure currently includes dialysis solution temperature. As has been shown previously, a relatively lower dialysis solution temperature (35 °C) is associated with a lower incidence of dialysis-related hypotension (i.e., higher hemodynamic stability) compared with the commonly used temperature of 37 °C. A system called the BTM (“blood temperature monitor”, Fresenius, Bad Homburg, Germany) allows to individualize the in-dialysis thermal balance: depending on whether it is set to monitor temperature (T mode) or energy balance (E mode), the BTM continuously adjusts the dialysis solution temperature on the principle of feedback upon measuring the temperature of blood in the arterial and venous sets. This helps individualize the thermal balance during extracorporeal elimination method. Thermal balance studies have confirmed a higher hemodynamic stability of the procedure with a negative energy balance. The main responsible mechanism is an increase in peripheral vascular resistance (in both arterial and venous components). In theory, another aspects whereby controlled thermal balance may have an impact on the course of dialysis is a change in efficacy, a change in the biological response by the body, a change in intravascular volume, or other changes. It should be noted these are just theoretical considerations subject to research. Thermal balance is likely to be the main factor responsible for the hemodynamic stability even when using methods based on convective transport of substances during extracorporeal purification (isolated ultrafiltration, hemofiltration and hemodiafiltration).
- MeSH
- dialýza ledvin přístrojové vybavení MeSH
- dialyzační roztoky MeSH
- energetický metabolismus MeSH
- hemodynamika MeSH
- lidé MeSH
- teplota MeSH
- ultrafiltrace MeSH
- změny tělesné teploty MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- přehledy MeSH
- srovnávací studie MeSH
The release of soil arsenic (As) in an unsaturated zone under oxidative conditions and at two temperatures simulating the seasonal effect (15 °C and 23 °C) was studied in four cultivated soils from the Elbe River catchment (Czech Republic, Central Europe). The soils with a low geogenic As background contained from 10 to 50 µg.g-1 of As, mostly originating from atmospheric deposition in the past. The temperature effect on the stability of As in soils was studied in connection with the stability of hydrated iron (Fe) oxides and dissolved organic carbon (DOC), as essential binding partners of As in soils. The temperature impact on As release was related to the actual As binding in soil determined by the sequential leaching. With predominant As binding to amorphous and poorly crystalline Fe phases the higher temperature (23 °C) increased As release up to twice compare to 15 °C. In the soils with a low total Fe and the preferential As binding to well-crystallised Fe phases the temperature effect on As release was negligible. Unlike Fe, the release of DOC is strongly temperature dependent, therefore As mobilisation was controlled by the DOC concentration. A higher experimental temperature (23 °C) supported the formation of DOC and the consequent release of As and Fe into the soil solution.
- MeSH
- arsen * analýza MeSH
- látky znečišťující půdu * analýza MeSH
- půda MeSH
- železo MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Česká republika MeSH
Rubredoxin from the hyperthermophile Pyrococcus furiosus (Pf Rd) is an extremely thermostable protein, which makes it an attractive subject of protein folding and stability studies. A fundamental question arises as to what the reason for such extreme stability is and how it can be elucidated from a complex set of interatomic interactions. We addressed this issue first theoretically through a computational analysis of the hydrophobic core of the protein and its mutants, including the interactions taking place inside the core. Here we show that a single mutation of one of phenylalanine's residues inside the protein's hydrophobic core results in a dramatic decrease in its thermal stability. The calculated unfolding Gibbs energy as well as the stabilization energy differences between a few core residues follows the same trend as the melting temperature of protein variants determined experimentally by microcalorimetry measurements. NMR spectroscopy experiments have shown that the only part of the protein affected by mutation is the reasonably rearranged hydrophobic core. It is hence concluded that stabilization energies, which are dominated by London dispersion, represent the main source of stability of this protein.
Recently, we have found that thermal stability of photosystem II (PSII) photochemistry in spruce needles is higher than in other plants (barley, beech) cultivated under the same temperatures. In this work, temperature dependences of various characteristics of PSII organization were studied in order to obtain complex information on the thermal stability of PSII function and organization in spruce. Temperature dependency of circular dichroism spectra revealed by about 6 °C higher thermal stability of macrodomain organization in spruce thylakoid membranes in comparison with Arabidopsis and barley ones; however, thermal disintegration of light-harvesting complex of PSII did not significantly differ among the species studied. These results thus indicate that thermal stability of PSII macro-organization in spruce thylakoid membranes is enhanced to a similar extent as thermal stability of PSII photochemistry. Clear-native polyacrylamide gel electrophoresis of preheated thylakoids demonstrated that among the separated pigment-protein complexes, only PSII supercomplexes (SCs) revealed considerably higher thermal stability in spruce thylakoids as compared to Arabidopsis and barley ones. Hence we suggest that higher thermal stability of PSII macro-organization of spruce is influenced by the maintenance of PSII SCs in the thylakoid membrane. In addition, we discuss possible effects of different PSII organizations and lipid compositions on the thermal stability of spruce thylakoid membranes.
- MeSH
- Arabidopsis cytologie fyziologie MeSH
- chlorofyl fyziologie MeSH
- cirkulární dichroismus MeSH
- elektroforéza v polyakrylamidovém gelu MeSH
- fluorescence MeSH
- fotosystém II (proteinový komplex) fyziologie MeSH
- ječmen (rod) cytologie fyziologie MeSH
- smrk cytologie fyziologie MeSH
- tylakoidy fyziologie MeSH
- vysoká teplota MeSH
- Publikační typ
- časopisecké články MeSH
- srovnávací studie MeSH
Thermal analysis is a valuable method in pharmaceutical research. A wide range of thermal methods are used in drug development like thermogravimetry (TG), diffe¬rential thermal analysis (DTA), differential scanning calori¬metry (DSC) and other sensitive and specific methods. The present review deals with application of these me¬thods in characterization of drugs and excipients, such as their polymorph stability, glass transition temperature, purity analysis and compatibility of drugs.
- Klíčová slova
- termické metody, farmaceutický vývoj, DSC, skelný přechod, polymorfismus, kompatibilita,
- MeSH
- chemické techniky analytické MeSH
- diferenciální skenovací kalorimetrie metody MeSH
- farmaceutická technologie MeSH
- fyzikální chemie MeSH
- léčivé přípravky MeSH
- příprava léků MeSH
- termografie metody MeSH
- termogravimetrie metody MeSH
- výzkum MeSH
- Publikační typ
- práce podpořená grantem MeSH
