Hole-Burning Spectroscopy of Proteins in External Fields:  Human Serum Albumin Complexed with the Hypericinate Ion

Köhler, M.; Gafert, and J.; Friedrich, J.; Falk, Heinz; Meyer, Joachim-Ernst

doi:10.1021/jp9531016

Cited by 27 publications

(26 citation statements)

References 38 publications

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“…This seemed to be reasonable, especially given the breadth of the visible absorption spectrum: there are no ''gaps'' of zero absorbance anywhere between the UV region and ;600 nm. It is certainly consistent with the results of low-temperature hole burning spectroscopy (9)(10)(11)(12)(13). Evidence is, nevertheless, emerging that for hypericin the ground state is much less heterogeneous than we had hypothesized.…”

Section: Introductionsupporting

confidence: 89%

Does Solvent Influence the Ground-state Tautomeric Population of Hypericin?¶

Wen¹,

Chowdhury²,

Fulton³

et al. 2003

Photochem Photobiol

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Section: Introductionsupporting

confidence: 89%

Does Solvent Influence the Ground-state Tautomeric Population of Hypericin?¶

Wen¹,

Chowdhury²,

Fulton³

et al. 2003

Photochem Photobiol

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“…HSA has two major binding sites denoted IIA and IIIA according to the subdomains where they occur. The interaction of hypericin with HSA has been studied by various groups (57)(58)(59)(60). Hypericin in aqueous physiological solution is aggregated (6 I), and binding with albumin helps to solubilize it in monomeric form, which is believed to be important for virucidal action (62).…”

Section: Introductionmentioning

confidence: 99%

Photophysics of Hypericin and Hypocrellin A in Complex with Subcellular Components: Interactions with Human Serum Albumin

Das¹,

Smirnov²,

Wen³

et al. 1999

Photchem. Photbio.

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Time-resolved fluorescence and absorption measurements are performed on hypericin complexed with human serum albumin, HSA (1:4, 1:1 and approximately 5:1 hypericin: HSA complexes). Detailed comparisons with hypocrellin A/HSA complexes (1:4 and 1:1) are made. Our results are consistent with the conclusions of previous studies indicating that hypericin binds to HSA by means of a specific hydrogen-bonded interaction between its carbonyl oxygen and the N1-H of the tryptophan residue in the IIA subdomain of HSA. (They also indicate that some hypericin binds nonspecifically to the surface of the protein.) A single-exponential rotational diffusion time of 31 ns is measured for hypericin bound to HSA, indicating that it is very rigidly held. Energy transfer from the tryptophan residue of HSA to hypericin is very efficient and is characterized by a critical distance of 94 A, from which we estimate a time constant for energy transfer of approximately 3 x 10(-15) s. Although it is tightly bound to HSA, hypericin is still capable of executing excited-state intramolecular proton (or hydrogen atom) transfer in the approximately 5:1 complex, albeit to a lesser extent than when it is free in solution. It appears that the proton transfer process is completely impeded in the 1:1 complex. The implications of these results for hypericin (and hypocrellin A) are discussed in terms of the mechanism of intramolecular excited-state proton transfer, the mode of binding to HSA and the light-induced antiviral and antitumor activity.

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“…The analyses of the crystal structure have revealed that the specialized drug-binding cavities of serum albumins are located in subdomains IIA and IIIA (15). Because of the clinical and pharmaceutical importance interaction of serum albumins with a variety of ligands has been studied extensively (16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26). The binding of Hyp to human serum albumin (HSA) helps to overcome difficulties in solubilization and dispersion of Hyp in aqueous physiological solution.…”

Section: Introductionmentioning

confidence: 99%

“…†Abbreviations: BSA, bovine serum albumin; DMSO, dimethylsulfoxide; HSA, human serum albumin; Hyp, hypericin; RRS, resonance Raman spectroscopy; RSA, rat serum albumin; SERS, surface-enhanced Raman spectroscopy. The studies of Falk et al (24,25) have suggested that the binding site of Hyp is in the IIIA subdomain of the HSA, where the Hyp is not completely shielded from the outer environment. However, in our previous study, by means of surface-enhanced Raman (SERS) and resonance Raman spectroscopy (RRS) techniques, we have identified the Hypbinding site as being in the IIA subdomain of HSA (26).…”

Section: Introductionmentioning

confidence: 99%

Interaction of Hypericin with Serum Albumins: Surface-enhanced Raman Spectroscopy, Resonance Raman Spectroscopy and Molecular Modeling Study¶

Miškovský¹,

Hritz²,

Sánchez-Cortés³

et al. 2007

Photochemistry and Photobiology

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Surface-enhanced Raman spectroscopy, resonance Raman spectroscopy and molecular modeling were employed to study the interaction of hypericin (Hyp) with human (HSA), rat (RSA) and bovine (BSA) serum albumins. The identification of the binding site of Hyp in serum albumins as well as the structural model for Hyp/ HSA complex are presented. The interactions mainly reflect: (1) a change of the strength of H bonding at the N1-H site of Trp; (2) a change of the Trp side-chain conformation; (3) a change of the hydrophobicity of the Trp environment; and (4) a formation of an H-bond between the carbonyl group of Hyp and a proton donor in HSA and RSA which leads to a protonated-like carbonyl in Hyp.Our results indicate that Hyp is rigidly bound in IIA subdomain of HSA close to Trp214 (distance 5.12 Å between the centers of masses). In the model presented the carbonyl group of Hyp is hydrogen bonded to Asn458. Two other candidates for hydrogen bonds have been identified between the bay-region hydroxyl group of Hyp and the carbonyl group of the Trp214 peptidic link and between the peri-region hydroxyl group of Hyp and the Asn458 carbonyl group. It is shown that the structures of the Hyp/HSA and Hyp/RSA complexes are similar to, and in some aspects different from, those found for the Hyp/BSA complex. The role of aminoacid sequence in the IIA subdomains of HSA, RSA and BSA is discussed to explain the observed differences. ¶Posted on the website on

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Hole-Burning Spectroscopy of Proteins in External Fields: Human Serum Albumin Complexed with the Hypericinate Ion

Cited by 27 publications

References 38 publications

Does Solvent Influence the Ground-state Tautomeric Population of Hypericin?¶

Does Solvent Influence the Ground-state Tautomeric Population of Hypericin?¶

Photophysics of Hypericin and Hypocrellin A in Complex with Subcellular Components: Interactions with Human Serum Albumin

Interaction of Hypericin with Serum Albumins: Surface-enhanced Raman Spectroscopy, Resonance Raman Spectroscopy and Molecular Modeling Study¶

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