Mass spectrometric studies shed light on unusual oxidative transformations of 1,2‐dehydro‐<i>N</i>‐acetyldopa

Abebe, Adal; Kuang, Qun F.; Evans, John F.; Sugumaran, Manickam

doi:10.1002/rcm.6630

Cited by 11 publications

(18 citation statements)

References 26 publications

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“…From the fragmentation pattern, it is difficult to discern any structural information of the products other than the fact that they are oligomeric products of DHI. In the case of deNADA and related compounds, we were able to establish the benzodioxan-type structure of the dimeric products [ 36 , 37 , 38 , 39 , 40 ]. In these cases, oxidative dimerization and other oligomerizations occur via quinone, quinone methide, and free radical intermediates.…”

Section: Discussionmentioning

confidence: 99%

Nonenzymatic Spontaneous Oxidative Transformation of 5,6-Dihydroxyindole

Sugumaran

Evans

Ito

et al. 2020

IJMS

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Melanin is an important phenolic skin pigment found throughout the animal kingdom. Tyrosine and its hydroxylated product dopa provide the starting material for melanin biosynthesis in all animals. Through a set of well-established reactions, they are converted to 5,6-dihydroxyindole (DHI) and DHI-2-carboxylic acid (DHICA). Oxidative polymerization of these two indoles produces the brown to black eumelanin pigment. The steps associated with these transformations are complicated by the extreme instability of the starting materials and the transient and highly reactive nature of the intermediates. We have used mass spectral studies to explore the nonenzymatic mechanism of oxidative transformation of DHI in water. Our results indicate the facile production of not only dimeric and trimeric products but also higher oligomeric forms of DHI upon exposure to air in solution, even under nonenzymatic conditions. Such instantaneous polymerization of DHI avoids toxicity to self-matter and ensures the much-needed deposition of melanin at (a) the wound site and (b) the infection site in arthropods. The rapid deposition of DHI melanin is advantageous for arthropods given their open circulatory system; the process limits blood loss during wounding and prevents the spread of parasites by encapsulating them in melanin, limiting the damage.

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Section: Discussionmentioning

confidence: 99%

Nonenzymatic Spontaneous Oxidative Transformation of 5,6-Dihydroxyindole

Sugumaran

Evans

Ito

et al. 2020

IJMS

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“…The reason for these significant differences between cuticles using NBAD and NADA as sclerotizing precursors remains unknown. In the recent past, we have successfully employed mass spectrometry (MS) to analyze and characterize a number of unusual molecular transformations of catecholamine derivatives that were difficult to delineate by conventional biochemical techniques . In order to tease out the biochemical differences between cuticle using NBAD and cuticle using NADA, we used MS again and report in this paper the novel production of previously uncharacterized colored NBAD quinone adducts.…”

Section: Introductionmentioning

confidence: 99%

Unraveling complex molecular transformations of N‐β‐alanyldopamine that account for brown coloration of insect cuticle

Barek

Evans

Sugumaran

2017

Rapid Comm Mass Spectrometry

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LC/MS analysis of the reaction mixture of NBAD-cuticular enzyme reactions reveals the novel production of colored quinone adducts that are not possible for NADA. Therefore, our results suggest that the brown coloration of cuticle formed through NBAD crosslinking is likely due to the formation and accumulation of NBAD quinone and its adducts, while NADA quinone adducts tend not to form during NADA crosslinking, producing a nearly colorless cuticle.

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“…18,19 N -Acetyl-Dopamine 17,20–22 is a better model for studying peptidyl-Dopa oxidation, as is N -acetyl-Dopa ethyl ester. 23,24 Both have been studied using UV–vis spectrophotometry with the limitation that many quinone-mediated oxidation products have similar spectra.…”

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confidence: 99%

α,β-Dehydro-Dopa: A Hidden Participant in Mussel Adhesion

et al. 2016

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Dopa (L-3,4-dihydroxyphenylalanine) is a key chemical signature of mussel adhesive proteins, but its susceptibility to oxidation has limited mechanistic investigations as well as practical translation to wet adhesion technology. To investigate peptidyl-Dopa oxidation, the highly diverse chemical environment of Dopa in mussel adhesive proteins was simplified to a peptidyl-Dopa analogue, N-acetyl-Dopa ethyl ester. On the basis of cyclic voltammetry and UV–vis spectroscopy, the Dopa oxidation product at neutral to alkaline pH was shown to be α,β-dehydro-Dopa (ΔD), a vinylcatecholic tautomer of Dopa-quinone. ΔD exhibited an adsorption capacity on TiO2 20-fold higher than that of the Dopa homologue in the quartz crystal microbalance. Cyclic voltammetry confirmed the spontaneity of ΔD formation in mussel foot protein 3F at neutral pH that is coupled to a change in protein secondary structure from random coil to β-sheet. A more complete characterization of ΔD reactivity adds a significant new perspective to mussel adhesive chemistry and the design of synthetic bioinspired adhesives.

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Mass spectrometric studies shed light on unusual oxidative transformations of 1,2‐dehydro‐N‐acetyldopa

Abstract: LC/MS analysis of the N-acetyl-1,2-dehydrodopa oxidation reaction reveals not only a possible novel oxidative cyclization route for the biosynthesis of coumarin-type dehydrodopa compounds in marine organisms, but also unusual oxidative transformations of dehydro dopa derivatives.

Cited by 11 publications

References 26 publications

Nonenzymatic Spontaneous Oxidative Transformation of 5,6-Dihydroxyindole

Nonenzymatic Spontaneous Oxidative Transformation of 5,6-Dihydroxyindole

Unraveling complex molecular transformations of N‐β‐alanyldopamine that account for brown coloration of insect cuticle

α,β-Dehydro-Dopa: A Hidden Participant in Mussel Adhesion

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