The Raman optical activity of β-D-xylose: where experiment and theory meet

Besides its applications in bioenergy and biosynthesis, β-D-xylose is a very simple monosaccharide that exhibits relatively high rigidity. As such, it provides the best basis to study the impact of different solvation shell radii on the computation of its Raman optical activity (ROA) spectrum. Indeed, this chiroptical spectroscopic technique provides exquisite sensitivity to stereochemistry, and benefits much from theoretical support for interpretation. Our simulation approach combines density functional theory (DFT) and molecular dynamics (MD) in order to efficiently account for the crucial hydration effects in the simulation of carbohydrates and their spectroscopic response predictions. Excellent agreement between the simulated spectrum and the experiment was obtained with a solvation radius of 10 Å. Vibrational bands have been resolved from the computed ROA data, and compared with previous results on different monosaccharides in order to identify specific structure–spectrum relationships and to investigate the effect of the solvation environment on the conformational dynamics of small sugars. From the comparison with ROA analytical results, a shortcoming of the classical force field used for the MD simulations has been identified and overcome, again highlighting the complementary role of experiment and theory in the structural characterisation of complex biomolecules. Indeed, due to unphysical puckering, a spurious ring conformation initially led to erroneous conformer ratios, which are used as weights for the averaging of the spectral average, and only by removing this contribution was near perfect comparison between theory and experiment achieved

Running Machinery Safety Assessment

Import 01/09/2009Autor se v diplomové práci zabývá problematikou bezpečnosti provozovaných strojních zařízení, popisuje základní pojmy, požadavky legislativy a technických norem na jejich provoz. Zaměřuje se zejména na ověření splnění zákonných požadavků a provedení analýzy rizika podle příslušné harmonizované normy. Výsledkem diplomové práce je zpracování návodu na posouzení bezpečnosti strojního zařízení a přijetí opatření k dosažení vyšší úrovně bezpečnosti provozovaného strojního zařízení.The author of the thesis deals with the safety of operating machinery, describes the basic concepts, requirements of legislation and technical standards for their operation. His aim is mainly on the verification of compliance with legal requirements and implementation of risk analysis in accordance with the relevant harmonized standard. Thesis result is processing instructions to assess the safety of machinery and the implementation of measures to achieve a higher level of safety of operating machinery.Prezenční040 - Katedra bezpečnostního managementuvýborn

Provozní rizika při provozu lyžařských vleků

Import 17/08/2007Prezenční040 - Katedra bezpečnostního management

Water soluble chromone Schiff base derivatives as fluorescence receptor for aluminium(III)

<p>A novel water-soluble chromone Schiff base derivatives bearing polyhydroxylated moiety were prepared and applied for specific recognition of metal ions in aqueous medium. Their selective fluorescence response to Al(III) over a variety of other biologically important metal ions were demonstrated. Electronic parameters of the sensors were also studied by quantum chemical computations.</p

Symmetry breaking in chiral ionic liquids evidenced by vibrational optical activity

Ionic liquids (ILs) are receiving increasing interest for their use in synthetic laboratories and industry. Being composed of charged entities, they show a complex and widely unexplored dynamic behavior. Chiral ionic liquids (CILs) have a high potential as solvents for use in asymmetric synthesis. Chiroptical methods, owing to their sensitivity towards molecular conformation, offer unique possibilities to study the structure of these chiral ionic liquids. Raman optical activity proved particularly useful to study ionic liquids composed of amino acids and the achiral 1-ethyl-3-methylimidazolium counterion. We could substantiate, supported by selected theoretical methods, that the achiral counterion adopts an overall chiral conformation in the presence of chiral amino acid ions. These findings suggest that in the design of chiral ionic liquids for asymmetric synthesis, the structure of the achiral counter ion also has to be carefully considered