National Repository of Grey Literature 26 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Separation of rotamers of 5-nitrosopyrimidines by capillary electrophoresis
Štěpánová, Sille ; Procházková, Eliška ; Čechová, Lucie ; Žurek, Jiří ; Janeba, Zlatko ; Dračínský, Martin ; Kašička, Václav
A new capillary electrophoresis (CE) method was developed for the separation of a new type of stereoisomers - rotamers of polysubstituted 5-nitrosopyrimidine derivatives. Partial separation of some rotamers was obtained in sodium borate, pH 9.3, or in Tris-phosphate, pH 2.2, background electrolytes (BGEs) free of cyclodextrins (CDs). However, the best, baseline separations of the rotamers of 5-nitrosopyrimidines were achieved in sodium borate BGE, pH 9.3, containing 20 mg/mL beta-CD as stereoselector, or in Tris-phosphate BGE, pH 2.2, with carboxymethyl-beta-CD as stereoselector.
Dynamics of paramagnetic complexes observed by Nuclear Magnetic Resonance
Blahut, Jan ; Hermann, Petr (advisor) ; Botta, Mauro (referee) ; Dračínský, Martin (referee)
In this Thesis, structure and dynamics of paramagnetic complexes for medical application are studied by Nuclear Magnetic Resonance (NMR). It focuses mainly on development of contrast agents (CA) for Magnetic Resonance Imaging (MRI) which is one of the most effective radiodiagnostic method nowadays. Most of the MRI CAs contains paramagnetic complexes of d- and f-metal ions. The presence of unpaired electron in proximity of NMR active nuclei has two main effects: paramagnetically induced shift and paramagnetically induced relaxa- tion. Both processes can dramatically change the NMR spectrum and often make it unobservable at all. Nevertheless, in many cases, acquisition of such spectra is possible and sometimes even less time-consuming than observation of diamag- netic molecules. Enhanced T1 relaxation allows faster pulse sequence repetition and increased chemical shift dispersion may lead to resolution of originally over- lapped signals. Moreover, the analysis of paramagnetic effects can provide useful information about the structure and dynamics of the studied system. Theoretical background of these effects is described in the Introduction of the Thesis. In the first part of Discussion in the Thesis, a new class of contrast agents for 19F-MRI based on nickel(II) and cobalt(II/III) ions is introduced...
Synthesis of ellipticine derivatives and study of their interactions with DNA
Dračínský, Martin ; Sejbal, Jan (advisor) ; Klinot, Jiří (referee) ; Lyčka, Antonín (referee) ; Rosenberg, Ivan (referee)
CONCLUSIONS t New strategy for ellipticine synthesis was proposed' The yields of the synthesis are very hígh and pure product is obtained. The strategy was verified with the synthesis of other ellipticine derivatives' rBenzylicoxidationsoťellipticineandl,4-dimethylcarbazolewerestudiedand13. hydroxyellipticine was slnthesised' ' Three empirical potentials were compared with reference ab initio data of ellipticine derivative - DNA base patr' . The ernpirical potentials calculate interaction energies of the complexes quite well (espeglallytheA-ffE6andtheLHpotentials)buttheyfailinthesearchofglobal energy minima geometri es' .Interactionsofellipticineandg.hydroxyellipticinewithtwooligonucleotideswerc studiedintwobuffers(weaklyacidicandneutral,ellipticineisprotonatedintlro acidic buffer). Using two-dimensional NMR techniques assignment of all hydrogen signals of oligonucleotides CGCTAGCG and ATAGCTAT was done. The most important interaction of the ellipticine derivatives with the oligonucleotides is intercalation, but in the acidic buffer ellipticine can form also non-intercalative (bond to the minor or to the major groove) complexes with the oligonucleotides. Both ellipticine derivatives destabilised the duplex structuÍe of the oligonucleotide ATAGCTAT in acidic environment. ln the neutral buffer the life-time...
Struktura a vlastnosti modifikovaných složek nukleových kyselin
Procházková, Eliška ; Dračínský, Martin (advisor) ; Lyčka, Antonín (referee) ; Hrabal, Richard (referee)
Modified nucleic acid components (nucleotides, nucleosides, nucleobases) display a wide range of biological activities such as antiviral, cytostatic, antimicrobial or antioxidative. Many of them are successfully used in clinical practice, for instance as anti-HIV drugs or in hepatitis B treatment. The first precondition for understanding biological effects is to evaluate the chemical structure as well as the conformation of the studied compounds correctly. For this purpose, solution-state nuclear magnetic resonance (NMR) spectroscopy in combination with mass spectrometry is the most frequently used method. Not only the structure, but also physico- chemical properties can be investigated using NMR spectroscopy, for instance, conformational changes, tautomeric forms, protonation sites, acido-basic properties, non-covalent interactions, isotopic exchanges or interactions with biomolecules. Similarly to solutions, NMR spectroscopy can be employed in studies of nucleic acid components (NACs) in solid state. This technique found assertion after computational-chemistry methods development during the last decades. Different solid-state structures (polymorphic forms) or dynamics of these compounds can be established by solid-state NMR spectroscopy in combination with quantum-chemical calculations. In this...
Solid-state NMR study of structure and segmental dynamics of pharmaceutical materials based on the solid dispersions of drugs in polymer matrices.
Policianová, Olívia ; Brus, Jiří (advisor) ; Smrček, Stanislav (referee) ; Dračínský, Martin (referee)
Highly-exact structural characterization is the crucial step in the development and manufacturing process of pharmaceutical materials. Their structural composition is, however, often very complex and hardly identifiable. The eligible way for obtaining definite structural interpretation of these systems appears the high-resolution solid-state nuclear magnetic resonance (ssNMR) spectroscopy. For this purpose the reliable tool - the ssNMR toolbox for comprehensive characterization of various pharmaceutical solids is described. The rigorous optimization of ssNMR techniques is carried out on enormous number of measured samples containing active pharmaceutical ingredients (APIs) with systems ranging from APIs formulated in solid dispersions to pure forms revealing extensive molecular disorder. In this study the influence of polymeric matrix on the creation of solid dispersion type susceptible for finely tuned controlled drug release is likewise discussed. The distinction between variable structural alignments of API molecules in 3D dimension of complicated pharmaceutical solids is allowed via simple strategy - factor analysis applied to hardly describable ssNMR spectra (13 C CP/MAS NMR and 19 F MAS NMR). The results of this ssNMR investigation contribute to better understanding of solid dispersion...
Molecular Dynamics in Selected Polycyclic Aromatic Compounds Monitored by Measurement of Selected Structural Parameters
Sýkora, Jan ; Strašák, Tomáš ; Blechta, Vratislav ; Dračínský, Martin ; Císařová, I.
The polycyclic aromatic compounds attract scientific attention namely due to their conjugated π-π aromatic systems which promise many interesting and unusual optical and electronic properties. Some of these compounds were shown to be effective in the development of materials useful e.g. in molecular-based electronics.
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Novel conformationally locked nucleosides and nucleotides based on bicyclo[3.2.1]octane scaffold as a pseudosugar moiety
Šála, Michal ; Dejmek, Milan ; Procházková, Eliška ; Hřebabecký, Hubert ; Rybáček, Jiří ; Dračínský, Martin ; Novák, Pavel ; Rosenbergová, Šárka ; Fukal, J. ; Sychrovský, Vladimír ; Rosenberg, Ivan ; Nencka, Radim
A route to a series of novel carbocyclic nucleosides locked in North conformation with bicyclo[3.2.1]octane scaffold was developed. Prepared nucleosides served as a starting material for the synthesis of modified oligomers [d(GCATATCAC), r(GCAUAUCAC), and A9]. Biological effects of the prepared nucleosides as well as the hybridization properties of the appropriate duplexes were evaluated.
Enzymatic decomposition of a locked nucleoside phosphoramidate monitored by 31P NMR spectroscopy
Procházková, Eliška ; Hřebabecký, Hubert ; Nencka, Radim ; Dračínský, Martin
Phosphoramidate derivatives are often used as prodrugs of modified nucleosides. The crucial step for the biologically active compound release in cells is then enzymatic hydrolysis of the phosphoramidate derivative. The enzymatic decomposition of a nucleoside prodrug 1 was monitored using 31P NMR spectroscopy and the structure of the reaction products was determined by 1D and 2D (COSY, HSQC, HMBC) NMR experiments and compared with the products obtained with non-enzymatic hydrolysis of the prodrug.
Synthesis and biological properties of polysubstituted 5-nitrosopyrimidines
Janeba, Zlatko ; Čechová, Lucie ; Žurek, Jiří ; Procházková, Eliška ; Dračínský, Martin
2,4,6-Triamino-5-nitrosopyrimidines have been reported to contain a strong intramolecular hydrogen bond between the 5-nitroso and 4- or 6-amino groups, thus forming an additional pseudoring. Such analogues were speculated to be good mimics of fused bicyclic derivatives, e.g. purines. A series of novel polysubstituted 2-amino-5-nitrosopyrimidines, as potential structural mimics of modifi ed purine nucleos(t)ides well-known for their important biological properties, has been designed and synthesized. The physicochemical and biological properties of the prepared polysubstituted 2-amino-5-nitrosopyrimidines are being evaluated.
Switchable intramolecular hydrogen bond in polysubstituted 5-nitrosopyrimidines
Procházková, Eliška ; Čechová, Lucie ; Žurek, Jiří ; Janeba, Zlatko ; Dračínský, Martin
The formation of strong intramolecular hydrogen bonds was observed in a series of 2-amino-5-nitrosopyrimidines with alkylamino and arylamino substituents in the positions 4 and 6. Mixtures of two rotamers differing in the orientation of the nitroso group were observed in the NMR spectra of the compounds where two distinct intramolecular hydrogen bonds could be formed. In several cases, we were able to isolate and characterize the two hydrogen bond isomers (two conformers) by column chromatography. The ratio of the two rotamers in equilibrium depends strongly on the character of the substituents in the positions 4 and 6 and can be finely tuned in a broad range of conformation ratios. The experimental results were supported by DFT calculations.

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