Structural Basis of Polydopamine Film Formation: Probing 5,6-Dihydroxyindole-Based Eumelanin Type Units and the Porphyrin Issue

Alfieri, Maria Laura; Micillo, Raffaella; Panzella, Lucia; Crescenzi, Orlando; Oscurato, Stefano Luigi; Maddalena, Pasqualino; Napolitano, Alessandra; Ball, Vincent; d’Ischia, Marco

doi:10.1021/acsami.7b09662

Cited by 112 publications

(141 citation statements)

References 51 publications

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“…This latter hypothesis accounts for two directly bonded pairs (G, H) and three remotely bonded pairs (i, j, k). Although neither oxindole intermediates nor pyrrolidone products have been reported previously in eumelanins, the ring cleavage required to produce such structures has been proposed in polydopamines (44). Finally, peak l is attributable to indole carbons 2-3 bonds from 15 N in the DHI or DHICA units displayed in Fig.…”

Section: Cell-free and Fungal Melanin Developmentmentioning

confidence: 74%

The melanization road more traveled by: Precursor substrate effects on melanin synthesis in cell-free and fungal cell systems

Chatterjee

Prados-Rosales

Tan

et al. 2018

Journal of Biological Chemistry

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Natural brown-black eumelanin pigments confer structural coloration in animals and potently block ionizing radiation and antifungal drugs. These functions also make them attractive for bioinspired materials design, including coating materials for drugdelivery vehicles, strengthening agents for adhesive hydrogel materials, and free-radical scavengers for soil remediation. Nonetheless, the molecular determinants of the melanin "developmental road traveled" and the resulting architectural features have remained uncertain because of the insoluble, heterogeneous, and amorphous characteristics of these complex polymeric assemblies. Here, we used 2D solid-state NMR, EPR, and dynamic nuclear polarization spectroscopic techniques, assisted in some instances by the use of isotopically enriched precursors, to address several open questions regarding the molecular structures and associated functions of eumelanin. Our findings uncovered: 1) that the identity of the available catecholamine precursor alters the structure of melanin pigments produced either in Cryptococcus neoformans fungal cells or under cell-free conditions; 2) that the identity of the available precursor alters the scaffold organization and membrane lipid content of melanized fungal cells; 3) that the fungal cells are melanized preferentially by an L-DOPA precursor; and 4) that the macromolecular carbon-and nitrogen-based architecture of cell-free and fungal eumelanins includes indole, pyrrole, indolequinone, and open-chain building blocks that develop depending on reaction time. In conclusion, the availability of catecholamine precursors plays an important role in eumelanin development by affecting the efficacy of pigment formation, the melanin molecular structure, and its underlying scaffold in fungal systems. 13 C, 15 N]tyrosine precursor. The 1.5-day melanins were examined in a 10-h experiment (dark blue contours) run on a Bruker AV3 DNP spectrometer operating at a 1 H frequency of 600 MHz, temperature of 100 K, magic-angle spinning frequency of 12.5000 Ϯ 0.0005 kHz, and TEDOR evolution period of 1.6 ms corresponding to one-bond pairwise 13 C-15 N correlations. The 3.0-day melanins were examined with a 46-h experiment (red contours) run on a Varian (Agilent) DD2 spectrometer operating at a 1 H frequency of 600 MHz, temperature of 234 K, magic-angle spinning frequency of 20.00 Ϯ 0.02 kHz, and TEDOR evolution period of 1.4 ms. Spinning sidebands that are incidental to the structural analysis are denoted by asterisk symbols. The 13 C-15 N cross-peaks designated by uppercase letters are identified provisionally with directly bound C-N pairs within the illustrated chemical structures, drawing on the corresponding ACD-predicted chemical shifts and previously proposed melanin structural constituents (11,13,16,41). The predicted chemical shift values, typically quoted with average error limits of 3-10 ppm, are shown for 13 C (red) and 15 N (blue). Cell-free and fungal melanin development

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Section: Cell-free and Fungal Melanin Developmentmentioning

confidence: 74%

The melanization road more traveled by: Precursor substrate effects on melanin synthesis in cell-free and fungal cell systems

Chatterjee

Prados-Rosales

Tan

et al. 2018

Journal of Biological Chemistry

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“…Proposed structures of PDA without satisfactory experimental confirmation or experimental and computational disproval , . Cyclic indole tetramers were found in eumelanins formed by oxidative polymerization of DHI …”

Section: Resultsmentioning

confidence: 96%

“…Thus 5,6‐dihydroxyindoles were oxidized either by air or with hydrogen peroxide in the presence of horse radish peroxidase. Because of missing dopamine units, the resulting PDA has different structure and properties as the products obtained from DA (Scheme ) . Such products are normally not called PDA but DHI eumelanins.…”

Section: Resultsmentioning

confidence: 99%

Chemistry of Polydopamine – Scope, Variation, and Limitation

2019

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Polydopamine (PDA) is a polymer easily obtained by oxidation of dopamine. It is composed of indole and dopamine units in various oxidation states and to a lesser extent of pyrroles. It adheres to all type of surfaces even under water due to its abundant catechol moieties assisted by amino groups. This property together with a widespread reactivity to nucleophiles and electrophiles allowing linkage of a variety of entities renders PDA extremely interesting for various applications in biology, biomedicine, membranes, catalysis, materials and water purification. The field of PDA is violently developing. The present review gives an overview about the chemistry and properties of PDA and its analogues with the focus on recent publications. Their widespread applications are occasionally touched. Analogues are obtained by two strategies: post‐modification of PDA and oxidative polymerization of dopamine analogues. Scope and limitations of these strategies are worked out giving impulses for future research in the field.

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“…Furthermore, deposition of pDA coatings on substrates is accompanied by formation of particles in suspension, and most attempts to determine pDA structure have been performed on pDA isolated from solution. However, recent evidence suggests that the structural characteristics and properties of pDA films are different from those of aggregates and solution species …”

Section: Figurementioning

confidence: 99%

Direct Evidence for the Polymeric Nature of Polydopamine

et al. 2018

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Inspired by the adhesive proteins of mussels, polydopamine (pDA) has emerged as one of the most widely employed materials for surface functionalization. Despite numerous attempts at characterization, little consensus has emerged regarding whether pDA is a covalent polymer or a noncovalent aggregate of low molecular weight species. Here, we employed single‐molecule force spectroscopy (SMFS) to characterize pDA films. Retraction of a pDA‐coated cantilever from an oxide surface shows the characteristic features of a polymer with contour lengths of up to 200 nm. pDA polymers are generally weakly bound to the surface through much of their contour length, with occasional “sticky” points. Our findings represent the first direct evidence for the polymeric nature of pDA and provide a foundation upon which to better understand and tailor its physicochemical properties.

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Structural Basis of Polydopamine Film Formation: Probing 5,6-Dihydroxyindole-Based Eumelanin Type Units and the Porphyrin Issue

Cited by 112 publications

References 51 publications

The melanization road more traveled by: Precursor substrate effects on melanin synthesis in cell-free and fungal cell systems

The melanization road more traveled by: Precursor substrate effects on melanin synthesis in cell-free and fungal cell systems

Chemistry of Polydopamine – Scope, Variation, and Limitation

Direct Evidence for the Polymeric Nature of Polydopamine

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