In order to investigate the isomerization and conversion mechanism of the advantageous and widely used nonsteroidal anti-inflammatory medicine flurbiprofen, the hybrid density functional theory was applied. According to the results, the rearrangement reaction of (R)-flurbiprofen to its (S)-enantiomer happens in a [1,3]-hydrogen shifts with inversion of configuration at chiral center C14. From the calculated energies, it can be understood that the rate-limiting step in the flurbiprofen isomerization is the excitation of (R)-flurbiprofen methyl ester in its initial form to the first excited singlet state S1 at λ=243.91 nm. we studied this process by scanning the C14-H17 distance for the excited singlet to get more information about the process of isomerization occurring upon excitation. The results of calculations demonstrated that the isomerization process should pass through a ~71 kcal/mol barrier. The (S)-flurbiprofen methyl ester is more photostable than its related (R)-enantiomer. This issue can be attributed to the -1.50 kcal/mol of thermodynamic stability of the (S)-flurbiprofen methyl ester.

Density functional theory with the basis set of 6-31+G(d) was used to investigate on the carbon nano layers, C(sp2), potential as a drug delivery system for transferring of anti-cancer drug temozolomide to the target tissue. In order to elucidate the possibility of drug transmission by utilizing a carrier, the mechanisms of direct drug degradation, and loaded drug on the carrier are analyzed and examined completely. Two possible and different pathways for direct drug hydrolysis have been considered. According to obtained results activation barriers of these two pathways are 62.17 and 72.10 kcal mol^-1, and 64.30 and 70.10 kcal mol^-1 for two gas mode and also two aqueous solvent conditions respectively. By comparison of outcomes, it can be found out that these activation barriers for both degradation pathways are significantly greater than the activation barriers for drug separation from the surface of carbon carrier (18.59 and 51.92 kcal mol^-1 for gas mode and 11.79 and 44.67 kcal mol-1 for aqueous solvent). Therefore, by studying the achieved outcomes, it can be deduced that separation and releasing of the drug from the carrier occurs faster kinetically than direct degradation of temozolomide, so the drug can reach to the target before direct decomposition.