Fluorescence resonance energy transfer from tryptophan in human serum albumin to a bioactive indoloquinolizine system

Das, Paramita; Mallick, Arabinda; Haldar, Basudeb; Chakrabarty, Alok; Chattopadhyay, Nitin

doi:10.1007/s12039-007-0013-9

Cited by 25 publications

(16 citation statements)

References 36 publications

(31 reference statements)

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“…1Bi-iii ). It is well known that HSA contains a single tryptophan (Trp-214) situated in sub-domain IIA that fluoresces upon excitation at 295 nm [ 39 , 40 ]. The conformational state of HSA can influence the exposure of this tryptophan residue, and thereby affect tryptophan fluorescence [ 39 ].…”

Section: Resultsmentioning

confidence: 99%

Potentiating the cellular targeting and anti-tumor activity of Dp44mTviabinding to human serum albumin: two saturable mechanisms of Dp44mT uptake by cells

et al. 2015

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Di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT) demonstrates potent anti-cancer activity. We previously demonstrated that 14C-Dp44mT enters and targets cells through a carrier/receptor-mediated uptake process. Despite structural similarity, 2-benzoylpyridine 4-ethyl-3-thiosemicarbazone (Bp4eT) and pyridoxal isonicotinoyl hydrazone (PIH) enter cells via passive diffusion. Considering albumin alters the uptake of many drugs, we examined the effect of human serum albumin (HSA) on the cellular uptake of Dp44mT, Bp4eT and PIH. Chelator-HSA binding studies demonstrated the following order of relative affinity: Bp4eT≈PIH>Dp44mT. Interestingly, HSA decreased Bp4eT and PIH uptake, potentially due to its high affinity for the ligands. In contrast, HSA markedly stimulated Dp44mT uptake by cells, with two saturable uptake mechanisms identified. The first mechanism saturated at 5-10 μM (Bmax:1.20±0.04 × 107 molecules/cell; Kd:33±3 μM) and was consistent with a previously identified Dp44mT receptor/carrier. The second mechanism was of lower affinity, but higher capacity (Bmax:2.90±0.12 × 107 molecules/cell; Kd:65±6 μM), becoming saturated at 100 μM and was only evident in the presence of HSA. This second saturable Dp44mT uptake process was inhibited by excess HSA and had characteristics suggesting it was mediated by a specific binding site. Significantly, the HSA-mediated increase in the targeting of Dp44mT to cancer cells potentiated apoptosis and could be important for enhancing efficacy.

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Section: Resultsmentioning

confidence: 99%

Potentiating the cellular targeting and anti-tumor activity of Dp44mTviabinding to human serum albumin: two saturable mechanisms of Dp44mT uptake by cells

et al. 2015

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“…As discussed above, the conditions of our experiments are not conducive to collisional quenching, thus, how can one reconcile the static quenching with the decrease in emission lifetime? One possibility is the presence of fluorescence resonance energy transfer (FRET) from Trp to PPIX . The FRET efficiency is defined in Equation (3) as:

true E = 1 - \frac{⟨ τ_{normalD normalA} ⟩}{⟨ τ_{D} ⟩}

…”

Section: Resultsmentioning

confidence: 99%

Effects of Visible‐Light Irradiation of Protoporphyrin IX on the Self‐Assembly of Tubulin Heterodimers

et al. 2016

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The formation and the effects of the laser irradiation of the complex formed by protoporphyrin IX (PPIX) and tubulin was investigated. We have used tubulin as a model protein to investigate whether docked photoactive ligands can affect the structure and function of polypeptides upon exposure to visible light. We observed that laser irradiation in the Soret band prompts bleaching of the PPIX which is accompanied by a sharp decrease in the intensity and average fluorescence lifetime of the protein (dominated by the four tryptophan residues of the tubulin monomer). The kinetics indicate non-trivial effects and suggest that the photosensitization of the PPIX bound to tubulin prompts structural alterations of the protein. These modifications were also observed through changes in the energy transfer between Trp residues and PPIX. The result suggest that laser irradiation produces localized partial unfolding of tubulin and that the changes prompt modification of the formation of microtubules in vitro. Measurements of singlet oxygen formation were inconclusive in determining whether the changes are prompted by reactive oxygen species or other excited state mechanisms.

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“…As the plot shows linear feature, the formation of binding complex with 1:1 (donor:acceptor) stoichiometry is demonstrated [17][18][19]. It is to be pointed out here that if 2:1 complex had been formed, the plot will be of non-linear type and the Eq.…”

Section: Binding Constant Of the Ground-state Complex Formedmentioning

confidence: 98%

Mode of anchoring of ZnO nanoparticles to molecules having both –COOH and –NH functionalities

Mandal

Bhattacharya

Chowdhury³

et al. 2010

Journal of Molecular Structure

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Fluorescence resonance energy transfer from tryptophan in human serum albumin to a bioactive indoloquinolizine system

Cited by 25 publications

References 36 publications

Potentiating the cellular targeting and anti-tumor activity of Dp44mTviabinding to human serum albumin: two saturable mechanisms of Dp44mT uptake by cells

Potentiating the cellular targeting and anti-tumor activity of Dp44mTviabinding to human serum albumin: two saturable mechanisms of Dp44mT uptake by cells

Effects of Visible‐Light Irradiation of Protoporphyrin IX on the Self‐Assembly of Tubulin Heterodimers

Mode of anchoring of ZnO nanoparticles to molecules having both –COOH and –NH functionalities

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