Limits...
Excited singlet molecular O₂(¹Δg) is generated enzymatically from excited carbonyls in the dark.

Mano CM, Prado FM, Massari J, Ronsein GE, Martinez GR, Miyamoto S, Cadet J, Sies H, Medeiros MH, Bechara EJ, Di Mascio P - Sci Rep (2014)

Bottom Line: This involves thermolysis of 3,3,4,4-tetramethyl-1,2-dioxetane, a chemical source, and horseradish peroxidase-catalyzed oxidation of 2-methylpropanal, as an enzymatic source.This corroborates formation of O2 ((1)Δg).Altogether, photoemission and chemical trapping studies clearly demonstrate that chemically and enzymatically nascent excited carbonyl generates (18)O2 ((1)Δg) by triplet-triplet energy transfer to ground state oxygen O2 ((3)Σg(-)), and supports the long formulated hypothesis of O2 ((1)Δg) involvement in physiological and pathophysiological events that might take place in tissues in the absence of light.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, CEP 05513-970, CP 26077, São Paulo, SP, Brazil.

ABSTRACT
In mammalian tissues, ultraweak chemiluminescence arising from biomolecule oxidation has been attributed to the radiative deactivation of singlet molecular oxygen [O2 ((1)Δg)] and electronically excited triplet carbonyl products involving dioxetane intermediates. Herein, we describe evidence of the generation of O2 ((1)Δg) in aqueous solution via energy transfer from excited triplet acetone. This involves thermolysis of 3,3,4,4-tetramethyl-1,2-dioxetane, a chemical source, and horseradish peroxidase-catalyzed oxidation of 2-methylpropanal, as an enzymatic source. Both sources of excited carbonyls showed characteristic light emission at 1,270 nm, directly indicative of the monomolecular decay of O2 ((1)Δg). Indirect analysis of O2 ((1)Δg) by electron paramagnetic resonance using the chemical trap 2,2,6,6-tetramethylpiperidine showed the formation of 2,2,6,6-tetramethylpiperidine-1-oxyl. Using [(18)O]-labeled triplet, ground state molecular oxygen [(18)O2 ((3)Σg(-))], chemical trapping of (18)O2 ((1)Δg) with disodium salt of anthracene-9,10-diyldiethane-2,1-diyl disulfate yielding the corresponding double-[(18)O]-labeled 9,10-endoperoxide, was detected through mass spectrometry. This corroborates formation of O2 ((1)Δg). Altogether, photoemission and chemical trapping studies clearly demonstrate that chemically and enzymatically nascent excited carbonyl generates (18)O2 ((1)Δg) by triplet-triplet energy transfer to ground state oxygen O2 ((3)Σg(-)), and supports the long formulated hypothesis of O2 ((1)Δg) involvement in physiological and pathophysiological events that might take place in tissues in the absence of light.

Show MeSH

Related in: MedlinePlus

Chemiluminescence studies of O2-mediated oxidation of IBAL catalyzed by HRP.(A) Total UV-visible light emission of triplet excited acetone in deuterated phosphate buffer (pD 7.4), and (B) NIR light emission of O2 (1Δg) at 1,270 nm after injection of 10 mM IBAL in a solution of 5 µM HRP in D2O, pD 7.4 at 37°C.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4120373&req=5

f3: Chemiluminescence studies of O2-mediated oxidation of IBAL catalyzed by HRP.(A) Total UV-visible light emission of triplet excited acetone in deuterated phosphate buffer (pD 7.4), and (B) NIR light emission of O2 (1Δg) at 1,270 nm after injection of 10 mM IBAL in a solution of 5 µM HRP in D2O, pD 7.4 at 37°C.

Mentions: Triplet acetone is also produced by O2-mediated oxidation of IBAL by molecular oxygen, catalyzed by HRP (Fig. 3). The total chemiluminescence was recorded in D2O at pD 7.4 in the presence of 5 µM HRP and 10 mM IBAL (Fig. 3A). Low-level O2 (1Δg) NIR light emission was also detected at 1,270 nm under similar experimental conditions (Fig. 3B).


Excited singlet molecular O₂(¹Δg) is generated enzymatically from excited carbonyls in the dark.

Mano CM, Prado FM, Massari J, Ronsein GE, Martinez GR, Miyamoto S, Cadet J, Sies H, Medeiros MH, Bechara EJ, Di Mascio P - Sci Rep (2014)

Chemiluminescence studies of O2-mediated oxidation of IBAL catalyzed by HRP.(A) Total UV-visible light emission of triplet excited acetone in deuterated phosphate buffer (pD 7.4), and (B) NIR light emission of O2 (1Δg) at 1,270 nm after injection of 10 mM IBAL in a solution of 5 µM HRP in D2O, pD 7.4 at 37°C.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4120373&req=5

f3: Chemiluminescence studies of O2-mediated oxidation of IBAL catalyzed by HRP.(A) Total UV-visible light emission of triplet excited acetone in deuterated phosphate buffer (pD 7.4), and (B) NIR light emission of O2 (1Δg) at 1,270 nm after injection of 10 mM IBAL in a solution of 5 µM HRP in D2O, pD 7.4 at 37°C.
Mentions: Triplet acetone is also produced by O2-mediated oxidation of IBAL by molecular oxygen, catalyzed by HRP (Fig. 3). The total chemiluminescence was recorded in D2O at pD 7.4 in the presence of 5 µM HRP and 10 mM IBAL (Fig. 3A). Low-level O2 (1Δg) NIR light emission was also detected at 1,270 nm under similar experimental conditions (Fig. 3B).

Bottom Line: This involves thermolysis of 3,3,4,4-tetramethyl-1,2-dioxetane, a chemical source, and horseradish peroxidase-catalyzed oxidation of 2-methylpropanal, as an enzymatic source.This corroborates formation of O2 ((1)Δg).Altogether, photoemission and chemical trapping studies clearly demonstrate that chemically and enzymatically nascent excited carbonyl generates (18)O2 ((1)Δg) by triplet-triplet energy transfer to ground state oxygen O2 ((3)Σg(-)), and supports the long formulated hypothesis of O2 ((1)Δg) involvement in physiological and pathophysiological events that might take place in tissues in the absence of light.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, CEP 05513-970, CP 26077, São Paulo, SP, Brazil.

ABSTRACT
In mammalian tissues, ultraweak chemiluminescence arising from biomolecule oxidation has been attributed to the radiative deactivation of singlet molecular oxygen [O2 ((1)Δg)] and electronically excited triplet carbonyl products involving dioxetane intermediates. Herein, we describe evidence of the generation of O2 ((1)Δg) in aqueous solution via energy transfer from excited triplet acetone. This involves thermolysis of 3,3,4,4-tetramethyl-1,2-dioxetane, a chemical source, and horseradish peroxidase-catalyzed oxidation of 2-methylpropanal, as an enzymatic source. Both sources of excited carbonyls showed characteristic light emission at 1,270 nm, directly indicative of the monomolecular decay of O2 ((1)Δg). Indirect analysis of O2 ((1)Δg) by electron paramagnetic resonance using the chemical trap 2,2,6,6-tetramethylpiperidine showed the formation of 2,2,6,6-tetramethylpiperidine-1-oxyl. Using [(18)O]-labeled triplet, ground state molecular oxygen [(18)O2 ((3)Σg(-))], chemical trapping of (18)O2 ((1)Δg) with disodium salt of anthracene-9,10-diyldiethane-2,1-diyl disulfate yielding the corresponding double-[(18)O]-labeled 9,10-endoperoxide, was detected through mass spectrometry. This corroborates formation of O2 ((1)Δg). Altogether, photoemission and chemical trapping studies clearly demonstrate that chemically and enzymatically nascent excited carbonyl generates (18)O2 ((1)Δg) by triplet-triplet energy transfer to ground state oxygen O2 ((3)Σg(-)), and supports the long formulated hypothesis of O2 ((1)Δg) involvement in physiological and pathophysiological events that might take place in tissues in the absence of light.

Show MeSH
Related in: MedlinePlus