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Accurate Quantum Mechanical Calculations on Noncovalent Interactions: Rationalization of X-ray Crystal Geometries by Quantum Chemistry Tools
Hostaš, Jiří ; Hobza, Pavel (advisor) ; Burda, Jaroslav (referee) ; Jurečka, Petr (referee)
There is a need for reliable rules of thumb for various applications in the area of biochemistry, supramolecular chemistry and material sciences. Simultaneously, the amount of information, which we can gather from X-ray crystal geometries about the nature of recognition processes, is limited. Deeper insight into the noncovalent interactions playing the most important role is needed in order to revise these universal rules governing any recognition process. In this thesis, systematic development and study of the accuracy of the computational chemistry methods followed by their applications in protein DNA and host guest systems, are presented. The non-empirical quantum mechanical tools (DFT-D, MP2.5, CCSD(T) etc. methods) were utilized in several projects. We found and confirmed unique low lying interaction energies distinct from the rest of the distributions in several amino acid−base pairs opening a way toward universal rules governing the selective binding of any DNA sequence. Further, the predictions and examination of changes of Gibbs energies (ΔG) and its subcomponents have been made in several cases and carefully compared with experiments. We determined that the choline (Ch+) guest is bound 2.8 kcal/mol stronger (calculated ΔG) than acetylcholine (ACh+) to self-assembled triple helicate rigid...
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Computational Studies of Interactions of Small Molecules with their Biological Targets
Nekardová, Michaela ; Hobza, Pavel (advisor) ; Berka, Karel (referee) ; Kabeláč, Martin (referee)
The thesis specializes in the computational description of pharmaceutically important compounds. A substantial number of pharmaceutical drugs are small molecules that are bound to an active site of an enzyme by the "lock (binding site) and key (drug)" model through non-covalent interactions. The association of enzymes with drugs cause an increase or decrease in the activity of enzymes. The main topic is focused on the computational elucidation of the structural basis for the interactions of the purine-like compounds with the enzyme cyclin- dependent kinase 2 that belongs to the protein-kinase enzyme family. These enzymes play an important role in the cell cycle regulation; their increased activity significantly contributes to the loss of control over cell proliferation, which is one of the primary causes of cancer cell formation. The study describes the binding motifs of roscovitine, which shows an inhibitory effect on the function of cyclin-dependent kinases, and its analogues containing bioisosteric central heterocycles in the complex with cyclin-dependent kinase 2. The binding affinity between the cyclin-dependent kinase 2 enzyme and the inhibitors was quantified as calculated binding scores and evaluated in relation to the conformation of the optimized structures. The hybrid model combining the...
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Noncovalent Interactions in the Gas Phase and Aqueous Solution: Theoretical Study
Zendlová, Lucie ; Hobza, Pavel (advisor) ; Burda, Jaroslav (referee) ; Vondrášek, Jiří (referee) ; Jurečka, Petr (referee)
EAPUr rr|lclltal \ alLlť5' 5 Conclusions :, , . In the ia) part of present work we c intera cti on b etween u d"',il ". . . thy;';; il:'::: :íJTj.:lÍ' lI jl.#.ffiJ,lil itt8:"é'siia small number or*u.",7nJ organió solvent ňr"."i", (CH3.H, solvents yů[T"i^f.completely different interactions between the bases and the b"''" p.'"{ ;' "idilnn il#} il-t ÍT:!fl,-. i: : " o:] Y" .'h:.-S,t.* tu,", ot tt," moleóule Iuórc 'u'r' u property, and the'. .'l,'..,ťff,.'*lt'Lť':.lill:ilF.S'T!,l;situated above or belolthe !Á; ;;i. ;';;lě'"o ri," olašó ň"l"-.\,," ,, unique y"J::fiffii:x::. ."n'o*ison with otr,!. .otu"nt,, uň.'r,"í'ř;;.". are the In the ib) part_of present work based on the MD, SCC_DDFTB_D and ;"",'.Y|Tť'.#1.:."ffi i"T."lrJ'".r""u.'".XincorporateJ."-oŇTduplexwe i) Replacing nucleic acid base by modified nucleobase X leads.*:'] ,o Structural changes of the centrď -uuš"-pui. Gtu.tarrangement of central modified base pairs). ónli with ttresma'lest modified nucleobase p 'r'" Á.iJ.;;*;;.í' (A-P, P-T) stay planar. In the case 'of.B-T, Á-il.;';6 in specificorientation, one of the modified nuú"JÁ""x"*íto.""a outfrom DNA duplex. ii) Incre, .,""olr'iT"i1iTi1fi" or modified nucleobase X increases rhe iii) The highest s.ďectivity among- all base ana|ogue studied wasfound for modified nu"l"obus" O In the secono pu* of...
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Interaction of proteins with inhibitors: quantum chemical study
Dobeš, Petr ; Hobza, Pavel (advisor) ; Vondrášek, Jiří (referee) ; Jurečka, Petr (referee)
This dissertation focuses on theoretical studies of the interaction between protein kinases and their inhibitors. Studied protein kinases, cyclin-dependent kinase 2 (CDK2) and CK2 kinase (casein kinase 2) play an important role in regulating cellular processes in eukaryotic organisms. Their abnormal function in human cells can lead to serious diseases. This process can be stopped by blocking the aberrant protein kinases using specific low molecular weight inhibitors. Inhibitors of protein kinases typically bind to the active site of the enzyme by noncovalent interactions. Theoretical description of these interactions using quantum-chemical and molecular mechanical methods can help in understanding the biophysical principles governing the binding. These, in turn, can be subsequently used for a rational drug design of more effective and more specific inhibitors. The stabilization energy of the complex of CDK2 with inhibitor roscovitine is predominantly formed by the dispersion energy. DFT methods, which do not describe the dispersion energy was thus completely inappropriate for the treatment of such a system. When an empirical term is included to correct for the description of dispersion, such methods, as e.g. the SCC-DFTB-D, can be recommended for computation of this or similar complexes. The dominant part...
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