TD-DFT Insight into Photodissociation of Co-C Bond in Coenzyme B12
Coenzyme B12 (AdoCbl) is one of the most biologically active forms of vitamin B12, and continues to be a topic of active research interest. The mechanism of Co-C bond cleavage in AdoCbl, and the corresponding enzymatic reactions are however, not well understood at the molecular level. In this work,...
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Frontiers Media S.A.
2014-02-01
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| Series: | Frontiers in Chemistry |
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| Online Access: | http://journal.frontiersin.org/Journal/10.3389/fchem.2013.00041/full |
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| author | Pawel Michal Kozlowski Hui eLiu Karina eKornobis Piotr eLodowski Maria eJaworska |
| author_facet | Pawel Michal Kozlowski Hui eLiu Karina eKornobis Piotr eLodowski Maria eJaworska |
| author_sort | Pawel Michal Kozlowski |
| collection | DOAJ |
| description | Coenzyme B12 (AdoCbl) is one of the most biologically active forms of vitamin B12, and continues to be a topic of active research interest. The mechanism of Co-C bond cleavage in AdoCbl, and the corresponding enzymatic reactions are however, not well understood at the molecular level. In this work, time-dependent density functional theory (TD-DFT) has been applied to investigate the photodissociation of coenzyme B12. To reduce computational cost, while retaining the major spectroscopic features of AdoCbl, a truncated model based on ribosylcobalamin (RibCbl) was used to simulate Co-C photodissociation. Equilibrium geometries of RibCbl were obtained by optimization at the DFT/BP86/TZVP level of theory, and low-lying excited states were calculated by TD-DFT using the same functional and basis set. The calculated singlet states, and absorption spectra were simulated in both the gas phase, and water, using the polarizable continuum model (PCM). Both spectra were in reasonable agreement with experimental data, and potential energy curves based on vertical excitations were plotted to explore the nature of Co-C bond dissociation. It was found that a repulsive 3(σCo-C → σ*Co-C) triplet state became dissociative at large Co-C bond distance, similar to a previous observation for methylcobalamin (MeCbl). Furthermore, potential energy surfaces (PESs) obtained as a function of both Co-CRib and Co-NIm distances, identify the S1 state as a key intermediate generated during photoexcitation of RibCbl, attributed to a mixture of a MLCT (metal-to-ligand charge transfer) and a σ bonding-ligand charge transfer (SBLCT) states. |
| first_indexed | 2024-04-12T07:52:43Z |
| format | Article |
| id | doaj.art-db71f196c7f84b63ae0b40405f8a82ed |
| institution | Directory Open Access Journal |
| issn | 2296-2646 |
| language | English |
| last_indexed | 2024-04-12T07:52:43Z |
| publishDate | 2014-02-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Chemistry |
| spelling | doaj.art-db71f196c7f84b63ae0b40405f8a82ed2022-12-22T03:41:34ZengFrontiers Media S.A.Frontiers in Chemistry2296-26462014-02-01110.3389/fchem.2013.0004166080TD-DFT Insight into Photodissociation of Co-C Bond in Coenzyme B12Pawel Michal Kozlowski0Hui eLiu1Karina eKornobis2Piotr eLodowski3Maria eJaworska4University of LouisvilleUniversity of LouisvilleUniversity of LouisvilleInstitute of Chemistry University of SilesiaInstitute of Chemistry University of SilesiaCoenzyme B12 (AdoCbl) is one of the most biologically active forms of vitamin B12, and continues to be a topic of active research interest. The mechanism of Co-C bond cleavage in AdoCbl, and the corresponding enzymatic reactions are however, not well understood at the molecular level. In this work, time-dependent density functional theory (TD-DFT) has been applied to investigate the photodissociation of coenzyme B12. To reduce computational cost, while retaining the major spectroscopic features of AdoCbl, a truncated model based on ribosylcobalamin (RibCbl) was used to simulate Co-C photodissociation. Equilibrium geometries of RibCbl were obtained by optimization at the DFT/BP86/TZVP level of theory, and low-lying excited states were calculated by TD-DFT using the same functional and basis set. The calculated singlet states, and absorption spectra were simulated in both the gas phase, and water, using the polarizable continuum model (PCM). Both spectra were in reasonable agreement with experimental data, and potential energy curves based on vertical excitations were plotted to explore the nature of Co-C bond dissociation. It was found that a repulsive 3(σCo-C → σ*Co-C) triplet state became dissociative at large Co-C bond distance, similar to a previous observation for methylcobalamin (MeCbl). Furthermore, potential energy surfaces (PESs) obtained as a function of both Co-CRib and Co-NIm distances, identify the S1 state as a key intermediate generated during photoexcitation of RibCbl, attributed to a mixture of a MLCT (metal-to-ligand charge transfer) and a σ bonding-ligand charge transfer (SBLCT) states.http://journal.frontiersin.org/Journal/10.3389/fchem.2013.00041/fullphotodissociationCoenzyme B12Co-C bondribosylcobalamintime-dependent density functional theory |
| spellingShingle | Pawel Michal Kozlowski Hui eLiu Karina eKornobis Piotr eLodowski Maria eJaworska TD-DFT Insight into Photodissociation of Co-C Bond in Coenzyme B12 Frontiers in Chemistry photodissociation Coenzyme B12 Co-C bond ribosylcobalamin time-dependent density functional theory |
| title | TD-DFT Insight into Photodissociation of Co-C Bond in Coenzyme B12 |
| title_full | TD-DFT Insight into Photodissociation of Co-C Bond in Coenzyme B12 |
| title_fullStr | TD-DFT Insight into Photodissociation of Co-C Bond in Coenzyme B12 |
| title_full_unstemmed | TD-DFT Insight into Photodissociation of Co-C Bond in Coenzyme B12 |
| title_short | TD-DFT Insight into Photodissociation of Co-C Bond in Coenzyme B12 |
| title_sort | td dft insight into photodissociation of co c bond in coenzyme b12 |
| topic | photodissociation Coenzyme B12 Co-C bond ribosylcobalamin time-dependent density functional theory |
| url | http://journal.frontiersin.org/Journal/10.3389/fchem.2013.00041/full |
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