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| 2. |
- Ai, Yue-Jie, 1982-, et al.
(författare)
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Repair of DNA Dewar Photoproduct to (6-4) photoproduct in (6-4) Photolyase
- 2011
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 115:37, s. 10976-10982
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Tidskriftsartikel (refereegranskat)abstract
- Dewar photoproduct (Dewar PP) is the valence isomer of (6-4) photoproduct ((6-4)PP) in photodamaged DNA. Compared to the extensive studied CPD photoproducts, the underlying repair mechanisms for the (6-4)PP, and especially for the Dewar PP, are not well-established to date. In this paper, the repair mechanism of DNA Dewar photoproduct T(dew)C in (6-4) photolyase was elucidated using hybrid density functional theory. Our results showed that, during the repair process, the T(dew)C has to isomerize to T(6-4)C photolesion first via direct C6'-N3' bond cleavage facilitated by electron injection. This isomerization mechanism is energetically much more efficient than other possible rearrangement pathways. The calculations provide a theoretical interpretation to recent experimental observations.
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| 3. |
- Ai, Yue-Jie, et al.
(författare)
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Theoretical Studies on Photoisomerizations of (6-4) and Dewar Photolesions in DNA
- 2010
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 114:44, s. 14096-14102
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Tidskriftsartikel (refereegranskat)abstract
- The (6-4) photoproduct ((6-4) PP) is one of the main lesions in UV-induced DNA damage. The (6-4) PP and its valence isomer Dewar photoproduct (Dewar PP) can have a great threat of mutation and cancer but gained much less attention to date. In this study, with density functional theory (DFT) and the complete active space self-consistent field (CASSCF) methods, the photoisomerization processes between the (6-4) PP and the Dewar PP in the gas phase, the aqueous solution, and the photolyase have been carefully examined. Noticeably, the solvent effect is treated with the CASPT2//CASSCF/Amber (QM/MM) method. Our calculations show that the conical intersection (Cl) points play a crucial role in the photoisomerization reaction between the (6-4) PP and the Dewar PP in the gas and the aqueous solution. The ultrafast internal conversion between the S-2 ((1)pi pi*) and the So states via a distorted intersection point is found to be responsible for the formation of the Dewar PP lesion at 313 nm, as observed experimentally. For the reversed isomeric process, two channels involving the "dark" excited states have been identified. In addition to the above passages, in the photolyase, a new electron-injection isomerization process as an efficient way for the photorepair of the Dewar PP is revealed.
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| 4. |
- Ai, Yue-Jie, et al.
(författare)
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Theoretical studies on the isomerization mechanism of the ortho-green fluorescent protein chromophore
- 2012
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 14:38, s. 13409-13414
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Tidskriftsartikel (refereegranskat)abstract
- We present a systematic theoretical investigation on the overall ground state and excited-state isomerization reaction mechanism of ortho-green fluorescent protein chromophore (o-HBDI) using the density functional theory and the multireference methods. The calculated results and subsequent analysis suggest the possible isomerization mechanism for o-HBDI. By comparison with experimental observation and detailed analysis, it is concluded that as initiated by the excited-state intramolecular proton transfer reaction, the conical intersection between the ground state and the excited state along the C4-C5 single-bond rotational coordinate is responsible for the rapid deactivation of o-HBDI.
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| 5. |
- Ai, Yue-Jie, et al.
(författare)
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Ultrafast deactivation processes in the 2-aminopyridine dimer and the adenine-thymine base pair : Similarities and differences
- 2010
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 133:6, s. 064302-
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Tidskriftsartikel (refereegranskat)abstract
- 2-aminopyridine dimer has frequently been used as a model system for studying photochemistry of DNA base pairs. We examine here the relevance of 2-aminopyridine dimer for a Watson-Crick adenine-thymine base pair by studying UV-light induced photodynamics along two main hydrogen bridges after the excitation to the localized (1)pi pi(*) excited-state. The respective two-dimensional potential-energy surfaces have been determined by time-dependent density functional theory with Coulomb-attenuated hybrid exchange-correlation functional (CAM-B3LYP). Different mechanistic aspects of the deactivation pathway have been analyzed and compared in detail for both systems, while the related reaction rates have also be obtained from Monte Carlo kinetic simulations. The limitations of the 2-aminopyridine dimer as a model system for the adenine-thymine base pair are discussed. (C) 2010 American Institute of Physics. [doi:10.1063/1.3464485]
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| 6. |
- Chang, Chiao-Nien, et al.
(författare)
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The Design, Structure–Activity, and Kinetic Studies of 3-Benzyl-5-oxa-1,2,3,4-Tetrahydro-2H-chromeno-(3,4-c)pyridin-8-yl Sulfamates as Steroid Sulfatase Inhibitors
- 2022
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Ingår i: Bioorganic chemistry. - : Elsevier BV. - 0045-2068.
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Tidskriftsartikel (refereegranskat)abstract
- Steroid sulfatase inhibitors block the local production of estrogenic steroids and are attractive agents for the treatment of estrogen-dependent cancers. Inspiration of coumarin-based inhibitors, we synthesized thirty-two 5-oxa-1,2,3,4-tetrahydro-2H-chromeno-(3,4-c)pyridin-8-yl sulfamates, focusing on the substitution derivatives on the adjacent phenyl ring and evaluated their abilities to block STS from human placenta and MCF-7 cells. SAR analysis revealed that the incorporation of chlorine at either meta and/or para position of the adjacent phenyl ring of the tricyclic skeleton enhanced STS inhibition. Di-substitutions at the adjacent phenyl ring were superior to mono and tri-substitutions. Further kinetic analysis of these compounds revealed that chloride-bearing compounds, such as 19m, 19v, and 19w, had KI of 0.02 to 0.11 nM and kinact/KI ratios of 8.8-17.5 nM-1min-1, a parameter indicated for the efficiency of irreversible inhibition. We also used the docking model to illustrate the difference in STS inhibitory potency of compounds. Finally, the safety and anti-cancer activity of selected compounds 19m, 19v, and 19w were also studied, showing the results of low cytotoxicity on NHDF cell line and being more potent than irosustat on ZR-75-1 cell, which was a hormone-dependent cancer cell line with high STS expression.
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| 7. |
- Dan, Lilin, et al.
(författare)
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Design of Offset Spatial Modulation OFDM
- 2021
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Ingår i: IEEE Transactions on Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 0090-6778 .- 1558-0857. ; 69:9, s. 6267-6280
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the idea of offset spatial modulation (OSM) is integrated with orthogonal frequency division multiplexing (OFDM), toward an efficient design to bridge their advantages. Compared to its conventional counterpart as spatial modulation (SM)-OFDM, the proposed OSM-OFDM scheme aims at providing a simplified implementation structure with less number of radio frequency (RF) chains, by introducing an offset between the RF chain and the index of the activated transmit antenna on each subcarrier. Specifically, three types of offset antenna selection (OAS) methods are developed to meet different scene requirements for different number of available RF chains. Furthermore, through theoretical analysis, we quantify the bit error rate upper bounds of OSM-OFDM with different types of OAS methods. Finally, extensive computer simulations demonstrate that OSM-OFDM provides a flexible tradeoff among implementation cost, computation complexity and error performance.
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| 8. |
- Fang, Shu, et al.
(författare)
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Offset Spatial Modulation and Offset Space Shift Keying : Efficient Designs for Single-RF MIMO Systems
- 2019
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Ingår i: IEEE Transactions on Communications. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0090-6778 .- 1558-0857. ; 67:8, s. 5434-5444
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Tidskriftsartikel (refereegranskat)abstract
- Spatial modulation (SM) and space shift keying (SSK) techniques have the unique advantages of their single-radio-frequency (RF) structures compared with conventional multiple-input-multiple-output (MIMO) techniques. However, the transmission rates of these techniques are decided by the maximal switching frequency or by the minimal switching time between the RF chain and transmit antennas, which has been a bottleneck for their applications in future broadband wireless communications. To alleviate this problem, we propose a class of novel offset SM (OSM) and offset SSK (OSSK) schemes, with the aid of channel state information (CSI) at the transmitter. Compared with conventional SM and SSK, the proposed OSM and OSSK schemes can reduce the switching frequency of the RF chain, by introducing an offset between the connected RF chain and the index of the spatial modulated antenna. In extreme conditions, the proposed OSM and OSSK can work without RF switching while maintaining the single-RF advantage of conventional SM and SSK schemes. Through theoretical analysis, we also develop the bit-error rate (BER) performance bounds for the proposed two schemes. Finally, our simulation results demonstrate that the proposed OSM and OSSK outperform their counterparts, including conventional SM, SSK, CSI-aided SM, and CSI-aided SSK, while having a simplified RF-switching structure.
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| 9. |
- Zhang, Feng, et al.
(författare)
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Nonadiabatic histidine dissociation of hexacoordinate heme in neuroglobin protein
- 2010
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Ingår i: Journal of Physical Chemistry A. - America : American Chemical Society. - 1089-5639 .- 1520-5215.
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, density functional theory and canonical nonadiabatic Monte Carlo transition state theory have been used to investigate histidine dissociation process from the hexacoordinate heme in Ngb protein. The potential energy surfaces (PES) of the lowest singlet, triplet, and quintet states are calculated by stepwise optimization along with the histidine dissociation pathway. Based on the calculated two-dimensional PES, the histidine dissociation rates for the spin-forbidden processes via singlet to triplet and singlet to quintet transitions have been calculated by the nonadiabatic Monte Carlo transition state theory in canonical ensemble. The present study provides a quantitative description on spin-forbidden histidine dissociation processes.
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| 10. |
- Zhang, Feng, 1981-, et al.
(författare)
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Nonradiative decay of the lowest excited singlet state of 2-aminopyridine is considerably faster than the radiative decay
- 2009
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Ingår i: Journal of Chemical Physics. - America : American -institute of Physics. - 0021-9606 .- 1089-7690. ; 130:14, s. 144315-
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Tidskriftsartikel (refereegranskat)abstract
- Ab initio calculations reveal that radiative lifetime of the lowest excited singlet state of 2-aminopyridine (2AP) molecule should be around 20 ns, consistent with the molecules of the same type, but is about one order of magnitude larger than the claimed experimental fluorescent lifetime in recent years. A S1/S0 conical intersection close to the S1 state has been located which could be the possible nonradiative channel that is responsible for the fast decay observed in the experiment.
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