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Dr. Manivannan Ethirajan Dr. Ping Chen Dr. Tymish Y. Ohulchanskyy Dr. Lalit N. Goswami Dr. Anurag Gupta Dr. Avinash Srivatsan Dr. Mahabeer P. Dobhal Joseph R. Missert Prof. Paras N. Prasad Prof. Karl M. Kadish Prof. Ravindra K. Pandey 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(21):6670-6684
We report herein a simple and efficient approach to the synthesis of a variety of meso‐substituted purpurinimides. The reaction of meso ‐ substituted purpurinimide with N‐bromosuccinimide regioselectively introduced a bromo functionality at the 20‐position, which on further reaction with a variety of boronic acids under Suzuki reaction conditions yielded the corresponding meso‐substituted analogues. Interestingly, the free base and the metalated analogues showed remarkable differences in photosensitizing efficacy (PDT) and tumor‐imaging ability. For example, the free‐base conjugate showed significant in vitro PDT efficacy, but limited tumor avidity in mice bearing tumors, whereas the corresponding NiII derivative did not produce any cell kill, but showed excellent tumor‐imaging ability at a dose of 0.3 μmol kg?1 at 24, 48, and 72 h post‐injection. The limited PDT efficacy of the NiII analogue could be due to its inability to produce singlet oxygen, a key cytotoxic agent required for cell kill in PDT. Based on electrochemical and spectroelectrochemical data in DMSO, the first one‐electron oxidation (0.52 V vs. SCE) and the first one‐electron reduction (?0.57–0.67 V vs. SCE) of both the free base and the corresponding NiII conjugates are centered on the cyanine dye, whereas the second one‐electron reduction (?0.81 V vs. SCE) of the two conjugates is assigned to the purpurinimide part of the molecule. Reduction of the cyanine dye unit is facile and occurs prior to reduction of the purpurinimide group, which suggests that the cyanine dye unit as an oxidant could be the driving force for quenching of the excited triplet state of the molecules. An interaction between the cyanine dye and the purpurinimide group is clearly observed in the free‐base conjugate, which compares with a negligible interaction between the two functional groups in the NiII conjugate. As a result, the larger HOMO–LUMO gap of the free‐base conjugate and the corresponding smaller quenching constant is a reason to decrease the intramolecular quenching process and increase the production of singlet oxygen to some degree. 相似文献
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Li G Dobhal MP Graham A Shibata M Zheng G Kozyrev A Pandey RK 《The Journal of organic chemistry》2003,68(10):3762-3772
The thermolysis products obtained by refluxing a series of vic-dihydroxychlorins in o-dichlorobenzene are characterized. Depending on the nature of substrates, this methodology provides an access for novel carbon-carbon linked chlorin-chlorin dimers and chlorin-porphyrin dimers with fixed and flexible orientations. The configuration of the linkers in the symmetrical and unsymmetrical dimers was confirmed by extensive NMR (COSY, ROESY) and molecular modeling studies. The molecular modeling studies of the energy-optimized dimers with flexible orientation confirmed that one of the chlorin units of the dimeric structure is tilted toward the opposite ring as evident by the shielding effect in the resonances of some of the protons in the (1)H NMR spectroscopy. Among the dimers with fixed orientation, compared to the free-base analogues, the related mono- and di-Zn(II) complexes produced a decreased fluorescence intensity, suggesting a possibility of the faster energy transfer via intersystem crossing (ISC) in the metalated derivatives than the corresponding free-base analogues to produce the corresponding excited triplet states. The photosensitizing efficacy of the monomers and the related dimers was also compared in radiation-induced fibrosarcoma (RIF) tumor cells at variable drug/light doses. In preliminary screening, compared to monomers, the corresponding carbon-carbon linked dimers produced enhanced photosensitizing efficacy. 相似文献
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Conservative methods for the Toda lattice equations 总被引:1,自引:0,他引:1
We are concerned with the numerical integration of the Todalattice equations by using different conservative methods. Numericalexperiments suggest that the global error for isospectral schemesdecreases exponentially with time but it is almost constantfor either symplectic or more general integrators. We providea theoretical explanation for these experimental findings. 相似文献
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Oxidative stress, produced under diabetic conditions, is a possible cause of various forms of tissue damage. The concentrations of antioxidant enzymes in cases of diabetes are significantly decreased, with a concomitant increase in lipid peroxidation. In this study, lupeol, a phytoconstituent from Solanum xanthocarpum, is shown to suppress the progression of diabetes after 21 days. Lupeol treatment caused decreases in glycated haemoglobin, serum glucose and nitric oxide, with a concomitant increase in serum insulin level. Furthermore, treatment with lupeol also increased antioxidant levels, with a decrease in the level of thiobarbituric acid-reactive oxygen species. 相似文献
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