The effect of hydration on the UV absorption coefficient of intact melanosomes

Lin, Erica; Peles, Dana N.; Simon, John D.

doi:10.1039/c2pp05233d

Cited by 3 publications

(1 citation statement)

References 27 publications

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“…Specific aims of the study were to address the role of polymerization kinetics and film thickness on the visible absorption properties of the final synthetic eumelanin against similar thickness-matched films produced by the previous AISSP protocol. Although both substrate and reaction conditions reported in this paper are mainly of technological relevance, they nonetheless provide the simplest model possible to elucidate the origin of the band broadening process in support of more biologically oriented studies on melanosome absorption properties 12–16 . Direct investigation of the optical properties of natural eumelanins in melanosomes is a difficult task due to the insolubility and heterogeneous character of the pigment.…”

Section: Introductionmentioning

confidence: 93%

Anomalous evolution of broadband optical absorption reveals dynamic solid state reorganization during eumelanin build-up in thin films

Bonavolontà

Lisio

d’Ischia

et al. 2017

Sci Rep

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The origin of eumelanin optical properties remains a formidable conundrum preventing a detailed understanding of the complex photo-protective role of these widespread natural pigments and the rational design of innovative bioinspired materials for optoelectronic applications. Here we report the unusual kinetic and thickness-dependent evolution of the optical properties of black eumelanin polymers generated by spontaneous aerial polymerization of 5,6-dihydroxyindole (DHI) thin films (0.1–1 μm), consistent with peculiar solid state reorganization mechanisms governing broadband absorption. The complete reversal of eumelanin UV-visible transmittance spectrum curvature on passing from 0.2 to 0.5 μm thick films, the marked increase in visible extinction coefficients with increasing film thickness and the higher UV extinction coefficients in slowly vs. rapidly generated polymers concur to support distinct dynamic regimes of solid-state molecular reorganization at the nanoscale level and to do affect the development of broadband visible absorption. Solid state control of molecular reorganization disclosed herein may delineate new rational strategies for tuning optical properties in eumelanin thin films for optoelectronic applications.

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Section: Introductionmentioning

confidence: 93%

Anomalous evolution of broadband optical absorption reveals dynamic solid state reorganization during eumelanin build-up in thin films

Bonavolontà

Lisio

d’Ischia

et al. 2017

Sci Rep

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Hydration effects on the electronic properties of eumelanin building blocks

Oliveira

Fonseca

Cabral

et al. 2016

The Journal of Chemical Physics

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Theoretical results for the electronic properties of eumelanin building blocks in the gas phase and water are presented. The building blocks presently investigated include the monomeric species DHI (5,6-dihydroxyindole) or hydroquinone (HQ), DHICA (5,6-dihydroxyindole-2-carboxylic acid), indolequinone (IQ), quinone methide (MQ), two covalently bonded dimers [HM ≡ HQ + MQ and IM ≡ IQ + MQ], and two tetramers [HMIM ≡ HQ + IM, IMIM ≡ IM + IM]. The electronic properties in water were determined by carrying out sequential Monte Carlo/time dependent density functional theory calculations. The results illustrate the role played by hydrogen bonding and electrostatic interactions in the electronic properties of eumelanin building blocks in a polar environment. In water, the dipole moments of monomeric species are significantly increased ([54-79]%) relative to their gas phase values. Recently, it has been proposed that the observed enhancement of the higher-energy absorption intensity in eumelanin can be explained by excitonic coupling among eumelanin protomolecules [C.-T. Chen et al., Nat. Commun. 5, 3859 (2014)]. Here, we are providing evidence that for DHICA, IQ, and HMIM, the electronic absorption toward the higher-energy end of the spectrum ([180-220] nm) is enhanced by long-range Coulombic interactions with the water environment. It was verified that by superposing the absorption spectra of different eumelanin building blocks corresponding to the monomers, dimers, and tetramers in liquid water, the behaviour of the experimental spectrum, which is characterised by a nearly monotonic decay from the ultraviolet to the infrared, is qualitatively reproduced. This result is in keeping with a "chemical disorder model," where the broadband absorption of eumelanin pigments is determined by the superposition of the spectra associated with the monomeric and oligomeric building blocks.

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Seorang Wanita Mengalami Aspirasi Barium Dengan Komplikasi Pneumonia

Marhana

Ajipurnomo

2019

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Background; Barium aspiration is one of rare major complication of esophagography. 40% cases of aspiration pneumonia occur without clinical symptoms and the other 30% results in deaths. Case. A 62-years-old female choked some barium liquid when performing esophagography procedure. We found ronchi on lower left haemithorax and granuler hiperdensity pattern on left paracardial from chest x-ray photo. Eight days later, patient suffered the clinical symptoms of infection and from chest x-ray photo we found infiltrate and rest of barium. We found Burcholderia Gladioli and Pseudomonas containing 1,22 mg/L of barium from microbiology examination of bronchus lavage. Discussion. Barium aspiration was one of major complication in esophagography procedure in extreme age. Chest x-ray and Computed Tomography can help to diagnose and evaluate in this case. Quantity and density of barium liquid could affect the prognosis of this case. Oropharingeal which containing a number of pathogen can cause pneumonia as disease complication. There was still no guideline for barium aspiration management, but bronchoscopy was recommended by many studies. Conclusion. Pneumonia was one of barium aspiration complication. Bronchoscopy was recommended procedure as diagnose dan therapy tool for barium aspiration case. Anaerob activity antibiotic should be given when pneumonia was suspected.

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The effect of hydration on the UV absorption coefficient of intact melanosomes

Cited by 3 publications

References 27 publications

Anomalous evolution of broadband optical absorption reveals dynamic solid state reorganization during eumelanin build-up in thin films

Anomalous evolution of broadband optical absorption reveals dynamic solid state reorganization during eumelanin build-up in thin films

Hydration effects on the electronic properties of eumelanin building blocks

Seorang Wanita Mengalami Aspirasi Barium Dengan Komplikasi Pneumonia

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