Metóda založená na meraní odrazivosti röntgenového žiarenia pri dopade pod malými uhlami na povrch skúmanej vzorky sa stala dôležitým nástrojom v biofyzikálnom výskume. Uplatňuje sa pri skúmaní vlastností tenkých organických vrstiev lipidov, proteínov a iných biopolymérov, surfaktantov atď. V článku je podaný krátky výklad fyzikálnej podstaty tejto metódy a jej aplikácie pri štúdiu štruktúrnych parametrov dvojzložkových membránových modelových systémov líšiacich sa v zložení lipidov a vo fázovom stave., In recent decades, X-ray reflectometry, an experimental technique based on measuring the reflected X-ray intensity from surfaces upon illumination under small angles, became an important tool in biophysical research. It is often used for the investigation and study of properties of thin organic lipid layers, proteins and other biopolymers, surfactants, etc. In the presented article, we introduce the teoretical foundations of this physical method and its applications. In particular, we discuss our recent experimental study of structural parameters of double-compound membrane model systems, which differ in lipid composition and phase state., Eva Nováková., and Obsahuje bibliografii
Salinization and alkalization of soil are widespread environmental problem and the alkali stress is more destructive than the effects caused by salt stress. To compare the mechanism of salt and alkali stresses, a sunflower variety (Helianthus annuus L. cv. Baikuiza 6) was tested under saline or alkaline conditions by mixing two neutral salts (NaCl and Na2SO4) or two alkaline salts (NaHCO3 and Na2CO3). The results showed that saline conditions differed greatly from alkaline conditions in their threshold intensities where sunflower can germinate, survive and grow. Under saline conditions, the emergence time was delayed, and the emergence rate and seedling survival rate also decreased with increasing salinity. However, under alkaline conditions, the rate of seedling survival decreased sharply but the emergence time and emergence rate did not change. In addition, the damaging effects of alkali stress on growth and photosynthesis were more severe than those of saline. In shoots, the main inorganic osmolyte and cation was K+ rather than Na+; the primary organic osmolytes were organic acid and soluble sugar rather than proline. Organic acid, NO3 -, and Cl- (only under saline condition) were the main source of anion. In addition, the osmotic adjustment and ion balance differed among sunflower roots, stems, and leaves. In conclusion, saline and alkaline conditions are two different stress conditions and there are special responses to two stress conditions for sunflower. and J. Liu, W. Q. Guo, D. C. Shi.