Riboflavin-induced Type 1 photo-oxidation of tryptophan using a high intensity 365 nm light emitting diode

Eduardo Silva; Pablo Barrias; Eduardo Fuentes-Lemus; Cristian Tirapegui; Alexis Aspee; Luke Carroll; Michael J. Davies; Camilo Lopez-Alarcon

doi:10.1016/j.freeradbiomed.2018.11.026

Riboflavin-induced Type 1 photo-oxidation of tryptophan using a high intensity 365 nm light emitting diode

Eduardo Silva, Pablo Barrias, Eduardo Fuentes-Lemus, Cristian Tirapegui, Alexis Aspee, Luke Carroll, Michael J. Davies, Camilo Lopez-Alarcon

Inflammation, Metabolism and Oxidation

20 Citations (Scopus)

Abstract

The mechanism of photo-oxidation of tryptophan (Trp) sensitized by riboflavin (RF) was examined employinghigh concentrations of Trp and RF, with a high intensity 365 nm light emitting diode (LED) source under N2,20% and 100% O2atmospheres. Dimerization of Trp was a major pathway under the N2atmosphere, though thisoccurred with a low yield (DφTrp= 5.9 × 10−3), probably as a result of extensive back electron transfer re-actions between RF•-and Trp(H)•+. The presence of O2decreased the extent of this back electron transfer re-action, and the extent of Trp dimerization. This difference is attributed to the formation of O2•-(generated viaelectron transfer from RF•-to O2) which reacts rapidly with Trp•leading to extensive consumption of the parentamino acid and formation of peroxides and multiple other oxygenated products (N-formylkynurenine, alcohols,diols) of Trp, as detected by LC-MS. Thus, it appears that thefirst step of the Type 1 mechanism of Trp photo-oxidation, induced by this high intensity 365 nm light source, is an electron transfer reaction between the aminoacid and3RF, with the presence of O2modulating the subsequent reactions and the products formed, as a resultof O2•-formation. These data have potential biological significance as LED systems and RF-based treatments havebeen proposed for the treatment of pathological myopia and keratitis.

Original language	English
Journal	Free Radical Biology and Medicine
Volume	131
Pages (from-to)	133-143
ISSN	0891-5849
DOIs	https://doi.org/10.1016/j.freeradbiomed.2018.11.026
Publication status	Published - 1 Feb 2019

Keywords

LED
Riboflavin
Photobleaching
Type 1/type 2 mechanisms
Triplet excited state
Tryptophan
Photo-oxidation
Dimers
Trimers
N-formylkynurenine
Electron transfer

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10.1016/j.freeradbiomed.2018.11.026

Cite this

@article{bfbc44145df444ff9ca6ec7d9f1e924f,

title = "Riboflavin-induced Type 1 photo-oxidation of tryptophan using a high intensity 365 nm light emitting diode",

abstract = "The mechanism of photo-oxidation of tryptophan (Trp) sensitized by riboflavin (RF) was examined employinghigh concentrations of Trp and RF, with a high intensity 365 nm light emitting diode (LED) source under N2,20% and 100% O2atmospheres. Dimerization of Trp was a major pathway under the N2atmosphere, though thisoccurred with a low yield (DφTrp= 5.9 × 10−3), probably as a result of extensive back electron transfer re-actions between RF•-and Trp(H)•+. The presence of O2decreased the extent of this back electron transfer re-action, and the extent of Trp dimerization. This difference is attributed to the formation of O2•-(generated viaelectron transfer from RF•-to O2) which reacts rapidly with Trp•leading to extensive consumption of the parentamino acid and formation of peroxides and multiple other oxygenated products (N-formylkynurenine, alcohols,diols) of Trp, as detected by LC-MS. Thus, it appears that thefirst step of the Type 1 mechanism of Trp photo-oxidation, induced by this high intensity 365 nm light source, is an electron transfer reaction between the aminoacid and3RF, with the presence of O2modulating the subsequent reactions and the products formed, as a resultof O2•-formation. These data have potential biological significance as LED systems and RF-based treatments havebeen proposed for the treatment of pathological myopia and keratitis.",

keywords = "LED, Riboflavin, Photobleaching, Type 1/type 2 mechanisms, Triplet excited state, Tryptophan, Photo-oxidation, Dimers, Trimers, N-formylkynurenine, Electron transfer",

author = "Eduardo Silva and Pablo Barrias and Eduardo Fuentes-Lemus and Cristian Tirapegui and Alexis Aspee and Luke Carroll and Davies, {Michael J.} and Camilo Lopez-Alarcon",

year = "2019",

month = feb,

day = "1",

doi = "10.1016/j.freeradbiomed.2018.11.026",

language = "English",

volume = "131",

pages = "133--143",

journal = "Free Radical Biology and Medicine",

issn = "0891-5849",

publisher = "Elsevier",

}

TY - JOUR

T1 - Riboflavin-induced Type 1 photo-oxidation of tryptophan using a high intensity 365 nm light emitting diode

AU - Silva, Eduardo

AU - Barrias, Pablo

AU - Fuentes-Lemus, Eduardo

AU - Tirapegui, Cristian

AU - Aspee, Alexis

AU - Carroll, Luke

AU - Davies, Michael J.

AU - Lopez-Alarcon, Camilo

PY - 2019/2/1

Y1 - 2019/2/1

N2 - The mechanism of photo-oxidation of tryptophan (Trp) sensitized by riboflavin (RF) was examined employinghigh concentrations of Trp and RF, with a high intensity 365 nm light emitting diode (LED) source under N2,20% and 100% O2atmospheres. Dimerization of Trp was a major pathway under the N2atmosphere, though thisoccurred with a low yield (DφTrp= 5.9 × 10−3), probably as a result of extensive back electron transfer re-actions between RF•-and Trp(H)•+. The presence of O2decreased the extent of this back electron transfer re-action, and the extent of Trp dimerization. This difference is attributed to the formation of O2•-(generated viaelectron transfer from RF•-to O2) which reacts rapidly with Trp•leading to extensive consumption of the parentamino acid and formation of peroxides and multiple other oxygenated products (N-formylkynurenine, alcohols,diols) of Trp, as detected by LC-MS. Thus, it appears that thefirst step of the Type 1 mechanism of Trp photo-oxidation, induced by this high intensity 365 nm light source, is an electron transfer reaction between the aminoacid and3RF, with the presence of O2modulating the subsequent reactions and the products formed, as a resultof O2•-formation. These data have potential biological significance as LED systems and RF-based treatments havebeen proposed for the treatment of pathological myopia and keratitis.

AB - The mechanism of photo-oxidation of tryptophan (Trp) sensitized by riboflavin (RF) was examined employinghigh concentrations of Trp and RF, with a high intensity 365 nm light emitting diode (LED) source under N2,20% and 100% O2atmospheres. Dimerization of Trp was a major pathway under the N2atmosphere, though thisoccurred with a low yield (DφTrp= 5.9 × 10−3), probably as a result of extensive back electron transfer re-actions between RF•-and Trp(H)•+. The presence of O2decreased the extent of this back electron transfer re-action, and the extent of Trp dimerization. This difference is attributed to the formation of O2•-(generated viaelectron transfer from RF•-to O2) which reacts rapidly with Trp•leading to extensive consumption of the parentamino acid and formation of peroxides and multiple other oxygenated products (N-formylkynurenine, alcohols,diols) of Trp, as detected by LC-MS. Thus, it appears that thefirst step of the Type 1 mechanism of Trp photo-oxidation, induced by this high intensity 365 nm light source, is an electron transfer reaction between the aminoacid and3RF, with the presence of O2modulating the subsequent reactions and the products formed, as a resultof O2•-formation. These data have potential biological significance as LED systems and RF-based treatments havebeen proposed for the treatment of pathological myopia and keratitis.

KW - LED

KW - Riboflavin

KW - Photobleaching

KW - Type 1/type 2 mechanisms

KW - Triplet excited state

KW - Tryptophan

KW - Photo-oxidation

KW - Dimers

KW - Trimers

KW - N-formylkynurenine

KW - Electron transfer

U2 - 10.1016/j.freeradbiomed.2018.11.026

DO - 10.1016/j.freeradbiomed.2018.11.026

M3 - Journal article

C2 - 30502456

SN - 0891-5849

VL - 131

SP - 133

EP - 143

JO - Free Radical Biology and Medicine

JF - Free Radical Biology and Medicine

ER -