Molecular mechanics study on conformation of perylene-quinonoid photosensitizers
- 30 Downloads
Using molecular mechanics method, values of the heat of formation (HF) of different conformations of perylenequinonoid photosensitizer, hypocrellin A (HA) and hypocrellin B (HB) were calculated and the variances of HF after phenolic protons’ dissociation were calculated as well. The following was found: (i) The HF values of four conformational isomers of HA and HB are similar to each other, so the four isomers can transform to each other at room temperature. (ii) There exists the difference between the ability of dissociation of phenolic protons of HA and that of HB, the former is higher than the latter. (iii) There exist two intramolecular hydrogen bonds in HA and HB. The bond energy is approximately 8 kJ/mol and the energy of conformation I is lower than that of conformation II The bond energy of HA is lower than that of HB. (iv) There exists a low energy spot when phenolic hydroxyl bond twists 180 from the psition where hydrogen bond is formed, which suggests that this kind of conformation probably exists. (v) The phenolic hydrogen of HBMC forms hydrogen bond with the neighbouring nitrogen, which is its structure basis of possessing photosensitizing activity.
Keywordsmolecular mechanics perylenequinonoid photosensitizer conformational isomer heat of formation proton dissociation intramolecular hydrogen bond
Unable to display preview. Download preview PDF.
- 1.Miller, G. G., Brown, K., Moore, R. B.etal., Uptake kinetics and intracellular localition of hypocrellin photosensitizers for photodynamic therapy: a confocal microscopy study,Photochem. Photobiol., 1995, 61: 632.Google Scholar
- 4.Jiang, L. J., Structure, character, photochemical reaction and reaction mechanisms of hypocrellin (I) —Structure and character of hypocrellin,Chinese Science Bulletin (in Chinese), 1990, 35: 1608.Google Scholar
- 5.Chen, S., Zhang, M. H., Jiang, L. J., Study on the mechanism of auto-sensitized photooxidation of hypocrellin,Photographic Sci. & Photochem. (in Chinese), 1993, 11: 1.Google Scholar
- 6.Hu, Y. Z., Jiang, L. J., Photophysical property and external heavy atom effect on hypocrellin,Chinese Science Bulletin (in Chinese), 1996, 41 229.Google Scholar
- 8.Sun, J. S., Pang, S. Z., Zhang, L.etal., Hypocrellin B-sensitized photodarnage on Na*-K+ ATPase and sodium permeability of human erythrocytes,Acta. Biol. Exp. Sin. (in Chinese), 1991, 24: 223.Google Scholar
- 9.Liang, L., Zhu, N. J., Zhang, M. H., Crystal and molecular structure of hypocrellin B,Chinese Science Bulletin (in Chinese). 1987. 32: 56.Google Scholar
- 10.Gajewski, J. J., Gillbert, K. E., McKelvey, J., MMX: an enhanced version of MM2,Adv. Mol. Model, 1990, 2: 65.Google Scholar
- 12.Diwu, Z. J., Jiang, L. J., Zhang, M. H.et al., Stereochemistry of hypocrellin,Chinese Science Bulletin (in Chinese), 1989, 34: 1073.Google Scholar
- 14.An, J. Y., Jiang, L. J., He, J. J., Photochemistry of hypocrellin A (VI)—Influence of pH on autesensitized photooxidation of HA,Chinese Science Bulletin (in Chinese), 1990, 35: 1119.Google Scholar
- 16.Ma, L., Zhang, M. H., Jiang, L. J., Reaction of hypocrellin B and mercapto-compound (E) —Reaction with 1/2Cys or cysteamine,Chinese Science Bulktin (in Chinese). 1991, 36: 1551.Google Scholar