Structural Dependence of 31P Chemical Shielding Tensors: DFT Study

PRECECHTELOVA, Jana, Marketa MUNZAROVA and Vladimir SKLENAR. Structural Dependence of 31P Chemical Shielding Tensors: DFT Study. Brno: Masarykova univerzita Brno. 1 pp. ISBN 80-210-3352-5. 2004.

Basic information

• Original name: Structural Dependence of 31P Chemical Shielding Tensors: DFT Study
• Name in Czech: Strukturni zavislost tenzoru 31P chemickeho stineni v B-DNA: DFT studium
• Authors: PRECECHTELOVA, Jana, Marketa MUNZAROVA and Vladimir SKLENAR.
• Edition: Brno, 1 pp. 2004.
• Publisher: Masarykova univerzita Brno

Other information

• Original language: English
• Type of outcome: Book on a specialized topic
• Field of Study: 10403 Physical chemistry
• Country of publisher: Czech Republic
• Confidentiality degree: is not subject to a state or trade secret
• Organization unit: Faculty of Science
• ISBN: 80-210-3352-5
• Keywords in English: DFT; NMR; 31P chemical shielding tensors; isotropic chemical shielding; chemical shielding anisotropy
• Tags: 31P chemical shielding tensors, chemical shielding anisotropy, DFT, isotropic chemical shielding, NMR

Abstract

Our study aims to assess the influences of the alpha, zeta and epsilon torsional angles, as well as the OPO bond angle on the 31P isotropic chemical shielding (CSI) and the chemical shielding anisotropy (CSA) in the suga-phosphate backbone of B-DNA. For this purpose, a model compound comprising two sugars connected by a phosphate group has been used. During the geometry optimizations of the model, only the torsional angle studied has been varied within its experimental range while all other backbone torsions have been constrained to average experimental values. Our results reveal that when either alpha or zeta goes up from 270 degs to 330 degs (the former) or from 240 to 300 degs (the latter), an increase in CSI as well as CSA is introduced. In the case of CSI the increase is as small as a few ppm for both torsional angles. By contrast, in the case of CSA it is as large as 30 ppm for alpha and 10 ppm for zeta. The larger ranges of CSI/CSA as a function of alpha (compared with zeta) suggest higher sensitivity of the 31P chemical shielding to the alpha torsional angle. The plots of CSI/CSA against alpha (zeta) obtained for various values of zeta=240-300 degs (alpha=270-330 degs) show that the trends of CSI/CSA are conserved and shifted to higher values when zeta (alpha) increases from 240 degs to 300 degs (from 270 to 330 degs). Interestingly, the extent into which the epsilon torsional angle influences CSI is of the same order as that we found for alpha and zeta. On the contrary, CSA remains almost unaffected by epsilon. Last but not least, the trend uncovered in the dependence of CSI on alpha correlates with changes in the OPO bond angle which in turn correlates with the alpha torsional angle.

Abstract (in Czech)

Cilem nasi prace bylo zhodnotit vliv torznich uhlu alfa, zeta, epsilon a vazebneho uhlu OPO na 31P isotropni chemicke stineni (CSI) a anizotropii 31P chemickeho stineni (CSA) v cukr-fosfatove pateri nukleovych kyselin B-DNA, a to pomoci teoretickych vypoctu na urovni metody funkcionalu hustoty (DFT). Pro tento ucel byl pouzit model slozeny ze dvou cukernych kruhu spojenych fosfatovou skupinou. Pri optimalizacich geometrii byl systematicky menen vzdy jen jeden studovany torzni uhel v ramci experimentalne pozorovaneho rozmezi. Ostatni uhly byl fixovany na sve prumerne experimentalni hodnote. Vysledky vypoctu ukazuji, ze pokud zeta (alfa) roste z 270 na 330 stupnu (z 240 na 330 stupnu), roste take CSI i CSA. V pripade CSI vsak narust obnasi jen nekolik malo ppm. Naproti tomu dosahuji rozdily v pripade CSA az 30 ppm pro uhel alfa a az 10 ppm pro uhel zeta. Vetsi rozpeti CSI/CSA hodnot v zavislosti na uhlu alfa ukazuje na vyssi sensitivitu 31P chemickeho stineni vuci tomuto torznimu uhlu nez vuci torznimu uhlu zeta. Z grafu zavislosti CSI/CSA na uhlu alfa (zeta) ziskanych pro ruzne hodnoty zet=240-300 stupnu (alfa=270-330 stupnu) lze videt, ze trendy CSI/CSA jsou zachovany, avsak posunuty smerem k vyssim hodnotam, jestlize zeta (alfa) roste z 240 na 300 stupnu (z 270 na 330 stupnu). Mira, do ktere ovlivnuje CSI uhel epsilon je srovnatelna s tou, kterou vykazuji uhly alfa a zeta. Naproti tomu zustava CSA uhlem zeta temer neovlivnena.

Links

• LN00A016, research and development project: Name: BIOMOLEKULÁRNÍ CENTRUM

Investor: Ministry of Education, Youth and Sports of the CR, Biomolecular Center