1
|
Abstract
Endogenous photosensitizers play a critical role in both beneficial and harmful light-induced transformations in biological systems. Understanding their mode of action is essential for advancing fields such as photomedicine, photoredox catalysis, environmental science, and the development of sun care products. This review offers a comprehensive analysis of endogenous photosensitizers in human skin, investigating the connections between their electronic excitation and the subsequent activation or damage of organic biomolecules. We gather the physicochemical and photochemical properties of key endogenous photosensitizers and examine the relationships between their chemical reactivity, location within the skin, and the primary biochemical events following solar radiation exposure, along with their influence on skin physiology and pathology. An important take-home message of this review is that photosensitization allows visible light and UV-A radiation to have large effects on skin. The analysis presented here unveils potential causes for the continuous increase in global skin cancer cases and emphasizes the limitations of current sun protection approaches.
Collapse
Affiliation(s)
- Erick L Bastos
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
| | - Frank H Quina
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
- Department of Chemical Engineering, Polytechnic School, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
| | - Maurício S Baptista
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
| |
Collapse
|
2
|
Dántola ML, Neyra Recky JR, Lorente C, Thomas AH. Photosensitized Dimerization of Tyrosine: The Oxygen Paradox †. Photochem Photobiol 2021; 98:687-695. [PMID: 34738644 DOI: 10.1111/php.13557] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 11/01/2021] [Indexed: 01/22/2023]
Abstract
In electron-transfer initiated photosensitization processes, molecular oxygen (O2 ) is not involved in the first bimolecular event, but almost always participates in subsequent steps giving rise to oxygenated products. An exception to this general behavior is the photosensitized dimerization of tyrosine (Tyr), where O2 does not participate as a reactant in any step of the pathway yielding Tyr dimers (Tyr2 ). In the pterin (Ptr) photosensitized oxidation of Tyr, O2 does not directly participate in the formation of Tyr2 and quenches the triplet excited state of Ptr, the reactive species that initiates the process. However, O2 is necessary for the dimerization, phenomenon that we have named as the oxygen paradox. Here, we review the literature on the photosensitized formation of Tyr2 and present results of steady-state and time resolved experiments, in search of a mechanistic model to explain the contradictory role of O2 in this photochemical reaction system.
Collapse
Affiliation(s)
- M Laura Dántola
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CCT La Plata-CONICET, La Plata, Argentina
| | - Jael R Neyra Recky
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CCT La Plata-CONICET, La Plata, Argentina
| | - Carolina Lorente
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CCT La Plata-CONICET, La Plata, Argentina
| | - Andrés H Thomas
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CCT La Plata-CONICET, La Plata, Argentina
| |
Collapse
|
3
|
A model to understand type I oxidations of biomolecules photosensitized by pterins. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY 2021. [DOI: 10.1016/j.jpap.2021.100045] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
|
4
|
Baptista MS, Cadet J, Greer A, Thomas AH. Photosensitization Reactions of Biomolecules: Definition, Targets and Mechanisms. Photochem Photobiol 2021; 97:1456-1483. [PMID: 34133762 DOI: 10.1111/php.13470] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 06/13/2021] [Indexed: 02/07/2023]
Abstract
Photosensitization reactions have been demonstrated to be largely responsible for the deleterious biological effects of UV and visible radiation, as well as for the curative actions of photomedicine. A large number of endogenous and exogenous photosensitizers, biological targets and mechanisms have been reported in the past few decades. Evolving from the original definitions of the type I and type II photosensitized oxidations, we now provide physicochemical frameworks, classifications and key examples of these mechanisms in order to organize, interpret and understand the vast information available in the literature and the new reports, which are in vigorous growth. This review surveys in an extended manner all identified photosensitization mechanisms of the major biomolecule groups such as nucleic acids, proteins, lipids bridging the gap with the subsequent biological processes. Also described are the effects of photosensitization in cells in which UVA and UVB irradiation triggers enzyme activation with the subsequent delayed generation of superoxide anion radical and nitric oxide. Definitions of photosensitized reactions are identified in biomolecules with key insights into cells and tissues.
Collapse
Affiliation(s)
| | - Jean Cadet
- Département de Médecine Nucléaire et de Radiobiologie, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Alexander Greer
- Department of Chemistry, Brooklyn College, Brooklyn, NY, USA.,Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY, USA
| | - Andrés H Thomas
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP), CCT La Plata-CONICET, La Plata, Argentina
| |
Collapse
|
5
|
Adi AC, Christanto C, Rachmawati H, Adlia A. Vitamin E-based Folic Acid Nanoemulsion: Formulation and Physical Evaluation for Oral Administration. Pharm Nanotechnol 2019; 7:304-313. [PMID: 31595848 PMCID: PMC6967134 DOI: 10.2174/2211738507666190717154040] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 05/15/2019] [Accepted: 06/28/2019] [Indexed: 11/24/2022]
Abstract
Background: Folic acid is essential in many metabolic processes and DNA synthesis. Nevertheless, folic acid is not stable, pH-sensitive, and deteriorated upon light exposure. Objective: This work was aimed to improve folic acid stability within vitamin E-based nanoemulsion. Methods: The nanoemulsion was prepared with self-nanoemulsification method by mixing vitamin E oil, Tween 20, and PEG 400. A pseudoternary phase diagram was constructed with aqueous titration to determine the optimum ratio for the mixture. The globule size, pH and entrapment efficiency were included in the nanoemulsion characterizations. In addition, the influence of centrifugation, storage, and pH on physical and chemical stabilities of folic acid nanoemulsion was evaluated. Results: Optimum formula was obtained from vitamin E, Tween 20, and PEG 400 with the ratio of 1:11:1, and the folic acid amount was 8 mg. The size of folic acid-loaded oil globule was 15.10 ± 1.51 nm, and the nanoemulsion pH was 6.24 ± 0.01. The nanoemulsion system was able to load the folic acid completely. Folic acid in nanoemulsion was stable after 14 days at room temperature, and it was more stable compared to folic acid in solution. In addition, the physical and chemical characteristics of folic acid in nanoemulsion was not affected by the simulated gastric condition. Conclusion: Hence, nanoemulsion is a promising strategy to enhance folic acid stability.
Collapse
Affiliation(s)
- Annis Catur Adi
- Faculty of Public Health, University of Airlangga, Kampus C Mulyorejo, Surabaya 60115, Indonesia
| | - Christanto Christanto
- School of Pharmacy, Bandung Institute of Technology, Ganesha 10, Bandung 40132, Indonesia
| | - Heni Rachmawati
- School of Pharmacy, Bandung Institute of Technology, Ganesha 10, Bandung 40132, Indonesia
| | - Amirah Adlia
- School of Pharmacy, Bandung Institute of Technology, Ganesha 10, Bandung 40132, Indonesia
| |
Collapse
|
6
|
Vostrikova AM, Kokorina AA, Mitrophanova AN, Sindeeva OA, Sapelkin AV, Sukhorukov GB, Goryacheva IY. One step hydrothermal functionalization of gold nanoparticles with folic acid. Colloids Surf B Biointerfaces 2019; 181:533-538. [PMID: 31185445 DOI: 10.1016/j.colsurfb.2019.05.072] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2019] [Revised: 05/10/2019] [Accepted: 05/28/2019] [Indexed: 01/23/2023]
Abstract
A new fundamental concept for one-step in-situ functionalization of gold nanoparticles (GNPs) with folic acid using hydrothermal treatment is described. Hydrothermal treatment has been tuned to increase the light emission from the pterin moiety of folic acid molecule, while retain its structure and functionality, thus providing a simple route to multimodal tags for a variety of in vitro and in vivo biomedical applications. Successful functionalization of GNPs with the biological ligand is confirmed by specific binding with anti-folic acid antibody.
Collapse
Affiliation(s)
- Anna M Vostrikova
- Saratov State University, Astrakhanskaya, 83, Saratov, 410012, Russia
| | - Alina A Kokorina
- Saratov State University, Astrakhanskaya, 83, Saratov, 410012, Russia
| | | | - Olga A Sindeeva
- Saratov State University, Astrakhanskaya, 83, Saratov, 410012, Russia
| | - Andrei V Sapelkin
- Saratov State University, Astrakhanskaya, 83, Saratov, 410012, Russia; Queen Mary University of London End Road, London, E1 4NS, UK
| | - Gleb B Sukhorukov
- Saratov State University, Astrakhanskaya, 83, Saratov, 410012, Russia; Queen Mary University of London End Road, London, E1 4NS, UK
| | | |
Collapse
|
7
|
Theoretical study of photoreactions between oxidized pterins and molecular oxygen. J Photochem Photobiol A Chem 2019. [DOI: 10.1016/j.jphotochem.2018.12.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
8
|
Reibnegger G. A DFT Study on the One-Electron Reduction/Oxidation of Biologically Relevant Pteridine Derivatives. ChemistrySelect 2018. [DOI: 10.1002/slct.201802368] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Gilbert Reibnegger
- Physiological Chemistry; Otto-Loewi Research Center; Medical University of Graz; Neue Stiftingtalstr. 6 Graz A-8010 Austria
| |
Collapse
|
9
|
Stability of folic acid under several parameters. Eur J Pharm Sci 2016; 93:419-30. [DOI: 10.1016/j.ejps.2016.08.045] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 08/23/2016] [Accepted: 08/24/2016] [Indexed: 11/24/2022]
|
10
|
Serrano MP, Vignoni M, Lorente C, Vicendo P, Oliveros E, Thomas AH. Thymidine radical formation via one-electron transfer oxidation photoinduced by pterin: Mechanism and products characterization. Free Radic Biol Med 2016; 96:418-31. [PMID: 27154982 DOI: 10.1016/j.freeradbiomed.2016.04.196] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 04/26/2016] [Accepted: 04/29/2016] [Indexed: 12/13/2022]
Abstract
UV-A radiation (320-400nm), recognized as a class I carcinogen, induces damage to the DNA molecule and its components through different mechanisms. Pterin derivatives are involved in various biological functions, including enzymatic processes, and it has been demonstrated that oxidized pterins may act as photosensitizers. In particular, they accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder. We have investigated the ability of pterin (Ptr), the parent compound of oxidized pterins, to photosensitize the degradation of the pyrimidine nucleotide thymidine 5'-monophosphate (dTMP) in aqueous solutions under UV-A irradiation. Although thymine is less reactive than purine nucleobases, our results showed that Ptr is able to photoinduce the degradation of dTMP and that the process is initiated by an electron transfer from the nucleotide to the triplet excited state of Ptr. In the presence of molecular oxygen, the photochemical process leads to the oxidation of dTMP, whereas Ptr is not consumed. In the absence of oxygen, both compounds are consumed to yield a product in which the pterin moiety is covalently linked to the thymine. This compound retains some of the spectroscopic properties of Ptr, such as absorbance in the UV-A region and fluorescence properties.
Collapse
Affiliation(s)
- Mariana P Serrano
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP), CCT La Plata-CONICET, Diagonal 113 y 64, 1900 La Plata, Argentina
| | - Mariana Vignoni
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP), CCT La Plata-CONICET, Diagonal 113 y 64, 1900 La Plata, Argentina
| | - Carolina Lorente
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP), CCT La Plata-CONICET, Diagonal 113 y 64, 1900 La Plata, Argentina
| | - Patricia Vicendo
- Laboratoire des Interactions Moléculaires et Réactivité Chimique et Photochimique (IMRCP), UMR 5623-CNRS/UPS, Université Toulouse III (Paul Sabatier), 118, route de Narbonne, F-31062 Toulouse cédex 9, France
| | - Esther Oliveros
- Laboratoire des Interactions Moléculaires et Réactivité Chimique et Photochimique (IMRCP), UMR 5623-CNRS/UPS, Université Toulouse III (Paul Sabatier), 118, route de Narbonne, F-31062 Toulouse cédex 9, France
| | - Andrés H Thomas
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP), CCT La Plata-CONICET, Diagonal 113 y 64, 1900 La Plata, Argentina.
| |
Collapse
|
11
|
Hirakawa K, Morimoto S. Electron transfer mediated decomposition of folic acid by photoexcited dimethoxophosphorus(V)porphyrin. J Photochem Photobiol A Chem 2016. [DOI: 10.1016/j.jphotochem.2015.11.028] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
|
12
|
Tinel L, Rossignol S, Ciuraru R, Dumas S, George C. Photosensitized reactions initiated by 6-carboxypterin: singlet and triplet reactivity. Phys Chem Chem Phys 2016; 18:17105-15. [DOI: 10.1039/c6cp03119f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The photophysical and photochemical properties of 6-carboxypterin, a model compound for the pterin derivatives present at the sea surface microlayer, were studied and its singlet and triplet reactivity toward halides and selected organics demonstrated.
Collapse
Affiliation(s)
- L. Tinel
- Université Lyon 1
- CNRS
- UMR 5256
- IRCELYON
- Institut de recherches sur la catalyse et l'environnement de Lyon
| | - S. Rossignol
- Université Lyon 1
- CNRS
- UMR 5256
- IRCELYON
- Institut de recherches sur la catalyse et l'environnement de Lyon
| | - R. Ciuraru
- Université Lyon 1
- CNRS
- UMR 5256
- IRCELYON
- Institut de recherches sur la catalyse et l'environnement de Lyon
| | - S. Dumas
- Université Lyon 1
- CNRS
- UMR 5256
- IRCELYON
- Institut de recherches sur la catalyse et l'environnement de Lyon
| | - C. George
- Université Lyon 1
- CNRS
- UMR 5256
- IRCELYON
- Institut de recherches sur la catalyse et l'environnement de Lyon
| |
Collapse
|
13
|
Hirakawa K, Ito H. Rhodamine-6G can photosensitize folic acid decomposition through electron transfer. Chem Phys Lett 2015. [DOI: 10.1016/j.cplett.2015.03.030] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
14
|
Denofrio MP, Ogilby PR, Thomas AH, Lorente C. Selective quenching of triplet excited states of pteridines. Photochem Photobiol Sci 2014; 13:1058-65. [DOI: 10.1039/c4pp00079j] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
15
|
Serrano MP, Borsarelli CD, Thomas AH. Type I photosensitization of 2'-deoxyadenosine 5'-monophosphate (5'-dAMP) by biopterin and its photoproduct formylpterin. Photochem Photobiol 2013; 89:1456-62. [PMID: 23837607 DOI: 10.1111/php.12134] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2013] [Accepted: 07/03/2013] [Indexed: 11/30/2022]
Abstract
Biopterin (Bip) and its photoproducts 6-formylpterin (Fop) and 6-carboxypterin (Cap) accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder where the protection against UV radiation fails because of the lack of melanin. These compounds absorb in the UV-A inducing a potential photosensitizing action that can cause damage to DNA and other biomolecules. In this work, we have investigated the capability of these pterin derivatives (Pt) to act as photosensitizers under UV-A irradiation for the degradation of 2'-deoxyadenosine 5'-monophosphate (5'-dAMP) in aqueous solutions, as model DNA target. Steady-state and time-resolved experiments were performed and the effect of pH was evaluated. The results showed that photosensitized degradation of 5'-dAMP was only observed under acidic conditions, and a mechanistic analysis revealed the participation of the triplet excited state of the pterin derivatives ((3)Pt*) by electron transfer yielding the corresponding pair of radical ions (Pt(•-) and 5'-dAMP(•+)), with successive photosensitizer recovery by electron transfer from Pt(•-) to O2. Finally, 5'-dAMP(•+) participates in subsequent reactions to yield degradation products.
Collapse
Affiliation(s)
- Mariana P Serrano
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata (UNLP), CCT La Plata-CONICET, La Plata, Argentina
| | | | | |
Collapse
|
16
|
Li G, Magana D, Dyer RB. Photoinduced electron transfer in folic acid investigated by ultrafast infrared spectroscopy. J Phys Chem B 2012; 116:3467-75. [PMID: 22364409 PMCID: PMC3311227 DOI: 10.1021/jp300392a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Conformational control of excited-state intramolecular electron transfer (ET) in folic acid (FA) has been investigated using femtosecond time-resolved infrared (TRIR) spectroscopy. Ultrafast excited-state ET between the pterin and the 4-aminobenzoyl subunits of FA is observed for the anionic form (at pH 10.0). An ET lifetime of 2.5 ps is estimated from Marcus theory for FA in the "U" conformation, in close agreement with the observed lifetime of 2.0 ps. Return to the ground state through the reverse ET reaction happens almost as rapidly, within 5 ps, resulting in rapid quenching of the singlet excited state. In mixed water:dimethyl sulfoxide solvent, ET becomes more unfavorable as FA adopts a more open conformation, thereby increasing the effective donor-acceptor distance and reducing the coupling energy. In contrast, no ET is observed for the cationic form of FA at low pH (6.0). In this case, the initial singlet excited state is localized on the pterin moiety of FA, and the excited-state charge distribution evolves with time. The charge redistribution in the pterin that occurs with intersystem crossing to the triplet state is characterized by changes in the transient IR spectrum. The excited-state lifetime is much longer in the absence of an ET quenching pathway. These results provide new insight into the mechanism of photodegradation and toxicity of FA. Ultrafast intramolecular ET in closed conformations of FA rapidly quenches the excited state and prevents efficient triplet state formation. Thus, conformations of FA that allow ultrafast intra-ET and rapid quenching of the singlet excited state play a key role in inhibiting pathological pathways following photoexcitation of FA.
Collapse
Affiliation(s)
- Guifeng Li
- Department of Chemistry, Emory University, Atlanta, Georgia, 30322, United States
| | - Donny Magana
- Department of Chemistry, Emory University, Atlanta, Georgia, 30322, United States
| | - R. Brian Dyer
- Department of Chemistry, Emory University, Atlanta, Georgia, 30322, United States
| |
Collapse
|
17
|
Petroselli G, Dántola ML, Cabrerizo FM, Lorente C, Braun AM, Oliveros E, Thomas AH. Quenching of the fluorescence of aromatic pterins by deoxynucleotides. J Phys Chem A 2010; 113:1794-9. [PMID: 19199487 DOI: 10.1021/jp8101496] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Steady-state and time-resolved studies of the fluorescence of four aromatic unconjugated pterins (pterin (Ptr), 6-(hydroxymethyl)pterin (Hmp), 6-methylpterin (Mep), and 6,7-dimethylpterin (Dmp)) in aqueous solutions in the presence of different nucleotides (2'-deoxyguanosine 5'-monophosphate (dGMP), 2'-deoxyadenosine 5'-monophosphate (dAMP), and 2'-deoxycytosine 5'-monophosphate (dCMP)) have been performed using the single-photon counting technique. The singlet excited states of acid forms of pterins are deactivated by purine nucleotides (dGMP and dAMP) via a combination of dynamic and static processes. The efficiency of the dynamic quenching is high, independently of the nature of the purine base of the nucleotide and of the chemical structure of the substituents linked to the pterin moiety. Analysis of the static quenching indicates that ground-state association between pterins and purine nucleotides takes place, but the formation of the corresponding complexes is significant only at relatively high reactant concentrations. The quenching of the fluorescence of acid forms of pterin derivatives by dCMP, a pyrimidine nucleotide, is slightly less efficient than the quenching by purine nucleotides and is purely dynamic. In alkaline media, the fluorescence quenching is much less efficient than in acidic media, the deactivation by purine nucleotides being purely dynamic, whereas quenching by dCMP is negligible. Possible mechanisms for the quenching of fluorescence of pterin derivatives by the different nucleotides are discussed.
Collapse
Affiliation(s)
- Gabriela Petroselli
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CCT La Plata-CONICET, Boulevard 113 y 64, 1900 La Plata, Argentina
| | | | | | | | | | | | | |
Collapse
|
18
|
Dántola ML, Denofrio MP, Zurbano B, Gimenez CS, Ogilby PR, Lorente C, Thomas AH. Mechanism of photooxidation of folic acid sensitized by unconjugated pterins. Photochem Photobiol Sci 2010; 9:1604-12. [PMID: 20922252 DOI: 10.1039/c0pp00210k] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Folic acid, or pteroyl-l-glutamic acid (PteGlu), is a precursor of coenzymes involved in the metabolism of nucleotides and amino acids. PteGlu is composed of three moieties: a 6-methylpterin (Mep) residue, a p-aminobenzoic acid (PABA) residue, and a glutamic acid (Glu) residue. Accumulated evidence indicates that photolysis of PteGlu leads to increased risk of several pathologies. Thus, a study of PteGlu photodegradation can have significant ramifications. When an air-equilibrated aqueous solution of PteGlu is exposed to UV-A radiation, the rate of the degradation increases with irradiation time. The mechanism involved in this "auto-photo-catalytic" effect was investigated in aqueous solutions using a variety of tools. Whereas PteGlu is photostable under anaerobic conditions, it is converted into 6-formylpterin (Fop) and p-aminobenzoyl-l-glutamic acid (PABA-Glu) in the presence of oxygen. As the reaction proceeds and enough Fop accumulates in the solution, a photosensitized electron-transfer process starts, where Fop photoinduces the oxidation of PteGlu to Fop, and H(2)O(2) is formed. This process also takes place with other pterins as photosensitizers. The results are discussed with the context of previous mechanisms for processes photosensitized by pterins, and their biological implications are evaluated.
Collapse
Affiliation(s)
- M Laura Dántola
- INIFTA, Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CCT La Plata-CONICET. C.C. 16, Suc. 4, (1900), La Plata, Argentina
| | | | | | | | | | | | | |
Collapse
|
19
|
Petroselli G, Erra-Balsells R, Cabrerizo FM, Lorente C, Capparelli AL, Braun AM, Oliveros E, Thomas AH. Photosensitization of 2'-deoxyadenosine-5'-monophosphate by pterin. Org Biomol Chem 2007; 5:2792-9. [PMID: 17700847 DOI: 10.1039/b707312g] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
UV-A radiation (320-400 nm) induces damages to the DNA molecule and its components through photosensitized reactions. Pterins, heterocyclic compounds widespread in biological systems, participate in relevant biological processes and are able to act as photosensitizers. We have investigated the photosensitization of 2'-deoxyadenosine-5'-monophosphate (dAMP) by pterin (PT) in aqueous solution under UV-A radiation. The effect of pH was evaluated, the participation of oxygen was investigated and the products analyzed. Kinetic studies revealed that the reactivity of dAMP towards singlet oxygen (1O2) is very low and that this reactive oxygen species does not participate in the mechanism of photosensitization, although it is produced by PT upon UV-A excitation. In contrast, analysis of irradiated solutions by means of electrospray ionization mass spectrometry strongly suggested that 8-oxo-7,8-dihydro-2'-deoxyadenosine-5'-monophosphate (8-oxo-dAMP) was produced, indicating that the photosensitized oxidation takes place via a type I mechanism (electron transfer).
Collapse
Affiliation(s)
- Gabriela Petroselli
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CONICET, Casilla de Correo 16, Sucursal 4, (1900) La Plata, Argentina
| | | | | | | | | | | | | | | |
Collapse
|