Quenching of carbonyl metabolites in triplet state by alkylated sorbates, esterified or peptide derivatives

• Grant number: 22/03864-5
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: October 01, 2022
• End date: March 31, 2026
• Field of knowledge: Biological Sciences - Biochemistry
• Principal Investigator: Etelvino José Henriques Bechara
• Grantee: Thiago da Mata Viola Gomes
• Host Institution: Instituto de Química (IQ). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

In vivo, metabolites generated at the triplet state are endowed with the property to initiate typical photochemical reactions in the absence of light leading to loss or gain of cellular functions. This is the case of DNA Cyclobutane Pyrimidine Dimers (CPDs) recently reported to occur in melanocytes hours after UV irradiation. Electronic excitation of the DNA bases was accomplished by energy transfer from triplet melanin products generated by reaction with endogenous peroxynitrite. Presently, we intend to continue the investigation of triplet acetone as a model for biological systems, with a focus on the mechanism of excited carbonyl quenching by sorbates (trans, trans-2,4-hexadienoates). Tetramethyldioxetane and the ultraweak chemiluminescent oxidation of isobutanal (IBAL) in aerated buffer catalyzed by horseradish peroxidase (HRP) will be employed as "clean" sources of triplet acetone and conjugated dienes, namely sorbates as quenchers of excited acetone, monitored by direct or sensitized chemiluminescence by added sodium 9,10-dibromoanthracene-2-sulfonate. Additionally, 2-phenylpropanal and 2,2-diphenylethanal will be explored as sources of, respectively, triplet acetophenone and benzophenone during HRP-catalyzed oxidation. Holding 10-100 times longer lifetimes than triplet acetone, these excited species can be more effective as singlet oxygen sources and pro-oxidants in cells. Decay of the triplet species/trans,trans-diene exciplex to the cis, trans-, trans, cis-, and cis, cis-diene photoproducts as well as ground state trans,trans-isomer is expected to occur, which would allow to choose the prevalent photoisomer as a triplet marker of triplet carbonyls hypothetically formed in model studies with peroxidase-catalyzed reactions and cell cultures. Preliminary lab studies confirmed formation of the cis,trans isomers during sorbate UV irradiation followed by HPLC separation. Sorbic acid will be esterified with long chain alcohols and with Cell Penetrating Peptides (CPP) as an attempt to improve the search for triplet intermediates in redox stressed isolated rat liver mitochondria, synaptosomes and cell cultures such as melanocytes, pancreatic ²-cell and neuronal cells. We envisage to contribute for clarifying possible roles of triplet carbonyls in the molecular mechanisms of weakly chemiluminescent pathophysiological processes, particularly those quenched by sorbates, through the detection and identification of "dark" photoproducts such as cis, trans isomers. (AU)

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

RAMOS, LUIZ D.; GOMES, THIAGO M. V.; V. STEVANI, CASSIUS; BECHARA, ETELVINO J. H.. Mining reactive triplet carbonyls in biological systems. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY, v. 243, p. 16-pg., 2023-06-01. (17/22501-2, 22/03864-5, 19/24515-6)