Porphyrin-melanin interaction: Effect on fluorescence and non-radiative relaxations

Losi, Aba; Bedotti, Roberta; Brancaleon, Lorenzo; Viappiani, Cristiano

doi:10.1016/1011-1344(93)80166-7

Cited by 23 publications

(10 citation statements)

References 9 publications

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“…Energy is therefore efficiently transferred from the excited electronic states to the vibrational and rotational internal degrees of freedom of the melanin macromolecule, and these states then relax nonradiatively within picoseconds (2,3). This model is supported by several experimental studies (3)(4)(5). Specifically, photoacoustic calorimetry (PAC) studies (4) report that all the energy deposited into melanin upon excitation at 488 nm and 514.5 nm is rapidly released in the form of heat.…”

Section: Introductionmentioning

confidence: 88%

“…Photoacoustic calorimetry measurements are sensitive to dynamic events ranging from instantaneous to 5 ms (5,(19)(20)(21)(22) (for a 1 MHz detection transducer). The nature of the response depends on the lifetime of the dynamic process.…”

Section: Methodsmentioning

confidence: 99%

“…Specifically, photoacoustic calorimetry (PAC) studies (4) report that all the energy deposited into melanin upon excitation at 488 nm and 514.5 nm is rapidly released in the form of heat. Photoacoustic calorimetry experiments involving melanin and porphyrins ( 5 ) assert that the release of excitation energy (Acx = 343 nm and 475 nm) as heat by melanin is essentially quantitative. In contrast to a simple nonradiative decay model, there is evidence to support the conclusion that the photoprotective mechanism of melanin involves electron-transfer processes that, after the absorption of light, produce free radicals.…”

Section: Introductionmentioning

confidence: 99%

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Wavelength‐dependent Photoacoustic Calorimetry Study of Melanin

Forest

Simon

1998

Photochem & Photobiology

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Photoacoustic calorimetry is used to examine the energy dissipation in melanin under physiological conditions (pH 7.2) following irradiation by UV and visible (VIS) light. Four different excitation wavelengths were examined: 264 nm, representative of UVC radiation, 351 nm and 400 nm (UVA-I radiation) and 527 nm, representative of VIS radiation. Following absorption at 527 nm, essentially all of the photon energy is released nonradiatively on a sub-nanosecond of excitation. Similar results are observed at 400 nm. At 351 nm, most of the energy was released as heat; a small amount of energy was retained (5 +/- 5%). When melanin is excited at 264 nm, 29 +/- 7% of the photon energy is retained by the molecule for a time period longer than a few hundred nanoseconds. These results show that a long-lived excited state or reactive intermediate is generated upon UV irradiation, whereas all of the excitation energy is dissipated nonradiatively in the visible portion of the spectrum. These results establish that the photochemistry of melanin is wavelength dependent.

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Section: Introductionmentioning

confidence: 88%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Wavelength‐dependent Photoacoustic Calorimetry Study of Melanin

Forest

Simon

1998

Photochem & Photobiology

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“…Fluorescence spectra were corrected for the instrumental response (file provided by manufacturer). Fluorescence intensities were calculated as the integral of the emission band and normalized for the absorbed energy by dividing the value of the integrated emission peak for the value of the optical density at the excitation wavelength [29, 31]. …”

Section: Experimental Methodsmentioning

confidence: 99%

Interaction of Human Serum Albumin with Novel 3,9-Disubstituted Perylenes

et al. 2013

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Human serum albumin (HSA) has been used as a model for the binding of a number of different ligands, including polyaromatic hydrocarbons, to proteins. In this case we have investigated the interaction of HSA with a novel set of perylene derivatives. Di-substituted perylene analogues have been synthesized as potentially useful organic photovoltaic materials. Their photophysical properties may make them viable for fuel cell applications too. However, these molecules are poorly soluble especially in aqueous solvents. Binding to water-soluble proteins may provide a way to solubilize them. At the same time one can study whether the photophysical processes initiated by the irradiation of a perylene ligand can cause conformational changes to the host protein. With the present study we demonstrated that of the three perylene derivatives investigated only one, the dimethoxy analogue, has a significant affinity for HSA at a binding site near the bottom of the central cleft (in proximity of the Trp214 residue). The small affinity prevents any significant photoinduced changes to occur in the protein.

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“…The photoacoustic instrument has been previously described [5]. Essentially, it consists of an excimer pumped dye laser (Lambda Physik, model EMGSO XeCl excimer laser, FL3100 dye laser, 5ns…”

Section: Photoacoustic Measurements 221 Znstrumenfafionmentioning

confidence: 99%