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Title:RAČUNALNIŠKE SIMULACIJE VPLIVA METILACIJE CITOZINA NA VEZAVO AFLATOKSINA B1 V DVOVERIŽNO DNK
Authors:ID Kores, Katarina (Author)
ID Bren, Urban (Mentor) More about this mentor... New window
Files:.pdf UN_Kores_Katarina_2016.pdf (2,49 MB)
MD5: F479FFA3B58E5D8329C41558C2F312DE
 
Language:Slovenian
Work type:Bachelor thesis/paper
Typology:2.11 - Undergraduate Thesis
Organization:FKKT - Faculty of Chemistry and Chemical Engineering
Abstract:Aflatoksini so metaboliti gliv iz družine Aspergillus, ki jih pogosto najdemo v nepravilno skladiščenih žitaricah, koruzi in oreščkih. Aflatoksin B1 je eden najbolj kancerogenih mikotoksinov, zato je raziskovanje njegovih vplivov in posledic zelo pomembno, saj bi lahko na tak način zmanjšali ali celo preprečili zastrupitve. Študij aflatoksina B1 je v znanstveni literaturi že veliko, saj se zelo rad kemijsko veže v dvojno vijačnico DNK, kjer povzroča nadaljnje mutacije. V diplomski nalogi smo se osredotočili na enega od dejavnikov, ki bi potencialno lahko vplival na afiniteto vezave aflatoksina B1, to je metilacija citozina v CpG območju samega vezavnega mesta. Tu imamo dva citozina na komplementarnih verigah DNK, zato smo imeli štiri možne kombinacije metiliranih citozinov, torej štiri obravnavane sisteme. Raziskovanja smo se lotili s pomočjo računalniških simulacij. Za določitev delnih nabojev 5-metil citozina smo uporabili ab initio metodi Hartree-Fock in RESP. Za simulacije molekulske dinamike (MD) smo ustrezne empirične parametre prevzeli iz AMBER-jevih topoloških in parametrskih knjižnic. Topologijo molekule aflatoksina B1 smo pridobili od kolega Tiborja Kune. Simulacije MD (5,4 ns) smo izvedli s programskih paketom Q, iz dobljenih trajektorij pa smo po metodi LIE izračunali vezavne Gibbsove proste energije. Prav tako smo spremljali število dogodkov, kjer je razdalja med vezavnima atomoma C8 (aflatoksin B1) in N7 (gvanin) znotraj odrezne razdalje, iz česar smo nato sklepali, ali bi kovalentna vez lahko nastala. Rezultati kažejo, da imamo pri vseh sistemih potencialne možnosti za nastanek kovalentne vezi med vezavnima atomoma. Izračuni po metodi LIE pa kažejo, da med posameznimi sistemi ni signifikantnih razlik v interkalacijskih prostih energijah molekule aflatoksina B1.
Keywords:DNK, aflatoksin B1, metilacija citozina, molekulska dinamika, prosta energija, interkalacija
Place of publishing:Maribor
Publisher:[K. Kores]
Year of publishing:2016
PID:20.500.12556/DKUM-62093 New window
UDC:582.28:575(043.2)
COBISS.SI-ID:20339222 New window
NUK URN:URN:SI:UM:DK:Y3L68LJI
Publication date in DKUM:16.09.2016
Views:2156
Downloads:174
Metadata:XML DC-XML DC-RDF
Categories:KTFMB - FKKT
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Secondary language

Language:English
Title:COMPUTER SIMULATIONS OF THE IMPACT OF CYTOSINE METHYLATION ON THE AFLATOXIN B1 INTERCALATION INTO DNA DOUBLE HELIX
Abstract:Aflatoxins are fungal metabolits typical for the Aspergillus family, which are frequently found in incorrectly stored cereals, corn and nutts. Aflatoxin B1 is one of the most carcinogenic mycotoxins – making the research of its impacts and consequences very importaint, since in this way we could reduce of even prevent infections. In the scientific literature one can find many studies of aflatoxin B1, due to its high affinity for intercalation into DNA double helix, where it causes further mutations. In this thesis we focused on one of the events, which could potentionaly effect on intercalation of aflatixin B1, that is cytosine methylation in CpG regions belonging to the binding site. Here one finds two cytosines on complementry DNA chains, so we had four possible combinations of methylated cytosines, that gave us four investigated systems. Research was tackled through computer simulations. For determination of partial charges on 5-methylcytosine we used ab initio Hartree-Fock and RESP methods. For molecular dynamics (MD) simulations we collected empirical parameters from AMBER's topology and parametre libraries. Topology of molecule aflatoxin B1 was obtained from a colleague Tibor Kuna. MD simulations were preformed using program package Q and subsequently binding Gibbs free energies were calculated with LIE method. We also determined the number of events, where the distance between binding atoms C8 (aflatoxin B1) and N7 (guanine) fell within the cutoff distance, from which we concluded, if a covalent bond could be formed. Results show that we have potential for bond formation between the binding atoms in all studied systems. Calculations using the LIE method also indicate that there are no significant differences in intercalation free energies of Aflatoxin B1 between the four studied systems.
Keywords:DNA, Aflatoxin B1, cytosine methylation, molecul dynamics, free energy, intercalation


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