Estudo eletroquímico e eletroanalítico dos biomarcadores de doenças humanas 7-metil-guanosina, orto tirosina e 3-nitro-tirosina
Autor(a) principal: | |
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Data de Publicação: | 2019 |
Tipo de documento: | Tese |
Idioma: | por |
Título da fonte: | Biblioteca Digital de Teses e Dissertações da UFRPE |
Texto Completo: | http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/8570 |
Resumo: | Oxidative damage in biological molecules, such as double-stranded DNA (dsDNA) and proteins are associated with numerous pathologies in the human body, such as cancer. Thus, it is of great relevance to investigate the redox mechanisms that occur in vivo for different biological processes. The present study aims to investigate the redox behavior of the biomarkers of human diseases, 7-methyl-guanosine (7-mGuo), ortho-tyrosina (o-Tyr) and 3-nitro-tyrosine (3-NO2-Tyr) on glassy carbon electrode (GCE) using voltammetric techniques, such as cyclic voltammetry (CV), square wave voltammetry (SWV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The electrochemical results of o-Tyr and 3-NO2-Tyr were also compared with the para-tyrosine (p-Tyr). Electroanalytical methodologies for the detection and quantification of these species were also investigated and developed in the absence and presence of possible interferences. Oxidation of the 7-mGuo on GCE occurs in single step pH-dependent irreversible pathway with the transfer of one electron and one proton with formation of polymer products absorbing on the electrode surface. An oxidation mechanism of 7-mGuo has been proposed. An electroanalytical method for quantification of 7-mGuo at physiological pH, using GCE and DPV was proposed, with a detection limit of 3.26 μmol L-1 and limit of quantification of 10,88 μmol L-1. Electrochemical detection of 7-mGuo was also investigated in the presence of potential interference of guanine, guanosine and 7-methylguanine (7-mGua). The study showed that the anodic peak of 7-mGuo suffered no interference of these species, since oxidation occurs in a very different potential. In general, the p- and o-Tyr undergo oxidation in a single irreversible step pH-dependent, with the transfer of one electron and one proton, from the phenolic group to formation of Tyr phenoxy radical (Tyr●). However, while the p-Tyr● radical preferably polymerizes, forming a resistive film on the GCE surface, the o-Tyr● reacts preferentially with water with formation of o- and p-quinone derivatives, that are adsorbed and reversibly reduced on the GCE surface. In relation the 3-NO2-Tyr its oxidation occurs, in general, in two irreversible steps. The first step is pH-dependent, while the second is pH-independent, indicating the absence of protons in the process. The first process correspond to the oxidation of the phenolic group to form 3-NO2-Tyr●, which reacts in different ways, polymerizing, forming a resistive film on the GCE surface and/or being directly electro-oxidized to a cationic product (second step). The voltammetric data also showed that the 3-NO2-Tyr phenol group is more difficult to oxidize when compared to p- and o-Tyr molecules. Moreover, unlike p-Tyr and o-Tyr that present no cathodic peak, 3-NO2-Tyr suffers in acid medium electro-reduction in a single irreversible step with formation of two electroactive products. Such processes were assigned to the reduction of the nitro group to form hydroxylamine and amine. Thus, is clearly demonstrated that the nitro group attached, as well as the phenolic group position at the Tyr molecule, strongly influence its redox properties. The redox mechanism of o-Tyr and 3-NO2-Tyr are presented and discussed. A voltammetric method for detection and quantification of 3-NO2-Tyr in physiological medium using DPV was also proposed and a concentration range of 20 to 200 μmol L-1, presented a correlation coefficient of 0.998 and a detection limit of 6, 21 μmol L-1. The knowledge of redox mechanisms of the biomarkers of human diseases, 7-mGuo, o-Tyr and 3-NO2-Tyr, as well as the proposed electroanalytical methods for their quantification correlates and are important in the literature, as basic knowledge to future interpretation and applications in molecular biochemistry. |
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OLIVEIRA, Severino Carlos Bezerra deNAVARRO, MarceloRIBEIRO, Williame FariasCAMARA, Claudio Augusto Gomes daMORAES, Alex Souzahttp://lattes.cnpq.br/5598955460493259NASCIMENTO, Raphael Fonseca do2022-04-08T13:46:55Z2019-12-20NASCIMENTO, Raphael Fonseca do. Estudo eletroquímico e eletroanalítico dos biomarcadores de doenças humanas 7-metil-guanosina, orto tirosina e 3-nitro-tirosina. 2019. 120 f. Tese (Programa de Pós-Graduação em Química) - Universidade Federal Rural de Pernambuco, Recife.http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/8570Oxidative damage in biological molecules, such as double-stranded DNA (dsDNA) and proteins are associated with numerous pathologies in the human body, such as cancer. Thus, it is of great relevance to investigate the redox mechanisms that occur in vivo for different biological processes. The present study aims to investigate the redox behavior of the biomarkers of human diseases, 7-methyl-guanosine (7-mGuo), ortho-tyrosina (o-Tyr) and 3-nitro-tyrosine (3-NO2-Tyr) on glassy carbon electrode (GCE) using voltammetric techniques, such as cyclic voltammetry (CV), square wave voltammetry (SWV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The electrochemical results of o-Tyr and 3-NO2-Tyr were also compared with the para-tyrosine (p-Tyr). Electroanalytical methodologies for the detection and quantification of these species were also investigated and developed in the absence and presence of possible interferences. Oxidation of the 7-mGuo on GCE occurs in single step pH-dependent irreversible pathway with the transfer of one electron and one proton with formation of polymer products absorbing on the electrode surface. An oxidation mechanism of 7-mGuo has been proposed. An electroanalytical method for quantification of 7-mGuo at physiological pH, using GCE and DPV was proposed, with a detection limit of 3.26 μmol L-1 and limit of quantification of 10,88 μmol L-1. Electrochemical detection of 7-mGuo was also investigated in the presence of potential interference of guanine, guanosine and 7-methylguanine (7-mGua). The study showed that the anodic peak of 7-mGuo suffered no interference of these species, since oxidation occurs in a very different potential. In general, the p- and o-Tyr undergo oxidation in a single irreversible step pH-dependent, with the transfer of one electron and one proton, from the phenolic group to formation of Tyr phenoxy radical (Tyr●). However, while the p-Tyr● radical preferably polymerizes, forming a resistive film on the GCE surface, the o-Tyr● reacts preferentially with water with formation of o- and p-quinone derivatives, that are adsorbed and reversibly reduced on the GCE surface. In relation the 3-NO2-Tyr its oxidation occurs, in general, in two irreversible steps. The first step is pH-dependent, while the second is pH-independent, indicating the absence of protons in the process. The first process correspond to the oxidation of the phenolic group to form 3-NO2-Tyr●, which reacts in different ways, polymerizing, forming a resistive film on the GCE surface and/or being directly electro-oxidized to a cationic product (second step). The voltammetric data also showed that the 3-NO2-Tyr phenol group is more difficult to oxidize when compared to p- and o-Tyr molecules. Moreover, unlike p-Tyr and o-Tyr that present no cathodic peak, 3-NO2-Tyr suffers in acid medium electro-reduction in a single irreversible step with formation of two electroactive products. Such processes were assigned to the reduction of the nitro group to form hydroxylamine and amine. Thus, is clearly demonstrated that the nitro group attached, as well as the phenolic group position at the Tyr molecule, strongly influence its redox properties. The redox mechanism of o-Tyr and 3-NO2-Tyr are presented and discussed. A voltammetric method for detection and quantification of 3-NO2-Tyr in physiological medium using DPV was also proposed and a concentration range of 20 to 200 μmol L-1, presented a correlation coefficient of 0.998 and a detection limit of 6, 21 μmol L-1. The knowledge of redox mechanisms of the biomarkers of human diseases, 7-mGuo, o-Tyr and 3-NO2-Tyr, as well as the proposed electroanalytical methods for their quantification correlates and are important in the literature, as basic knowledge to future interpretation and applications in molecular biochemistry.Danos oxidativos em moléculas biológicas, como no DNA de dupla hélice (dsDNA) e proteínas, estão associados com inúmeras patologias no organismo, tais como câncer. Assim é de grande relevância investigar os mecanismos redox que ocorrem in-vivo para diferentes processos biológicos. O presente trabalho tem como objetivo principal investigar o comportamento redox dos biomarcadores de doenças humanas, a 7-metil-guanosina (7-mGuo), orto-tirosina (o-Tyr) e 3-nitro-tirosina (3-NO2-Tyr) em eletrodo de carbono vítreo (GCE), utilizando técnicas voltamétricas, como voltametria cíclica (CV), voltametria de onda quadrada (SWV) e voltametria de pulso diferencial (DPV), bem como espectroscopia de impedância eletroquímica (EIS). Os resultados eletroquímicos da o-Tyr e da 3-NO2-Tyr também foram comparados aos da para-tirosina (p-Tyr). Metodologias eletroanalíticas para detecção e quantificação dessas espécies também foram investigadas e desenvolvidas na ausência e na presença de possíveis interferentes. A oxidação da 7-mGuo no GCE ocorre em uma única etapa irreversível dependente do pH, com a transferência de um elétron e um próton com a formação de produtos poliméricos que adsorvem fortemente na superfície do eletrodo. Um mecanismo da oxidação da 7-mGuo foi proposto a partir da análise dos resultados. Um método eletroanalítico para quantificação da 7-mGuo em pH fisiológico, utilizando GCE e DPV foi proposto, com um limite de detecção de 3,26 μmol L-1 e limite de quantificação de 10,88 μmol L-1. A detecção eletroquímica da 7-mGuo também foi investigada na presença dos potenciais interferentes, guanina, guanosina e 7-metilguanina (7-mGua). O estudo demonstrou que o pico anódico da 7-mGuo não sofreu nenhuma interferência dessas espécies, uma vez que sua oxidação ocorre em um potencial bastante distinto. Em geral, a p- e o-Tyr sofrem oxidação em uma única etapa irreversível, dependente do pH, com a transferência de um elétron e um próton, do grupo fenólico para a formação do radical fenóxi (Tyr●). No entanto, enquanto o radical da p-Tyr● polimeriza preferencialmente, formando um filme resistivo na superfície do GCE, o da o-Tyr● reage preferencialmente com água com a formação de derivados de o- e p-quinonas. Em relação a 3-NO2-Tyr, sua oxidação ocorre em duas etapas consecutivas irreversíveis. A primeira etapa é dependente do pH, enquanto a segunda é independente, indicando a ausência de prótons no processo. O primeiro processo corresponde à oxidação do grupo fenólico para formação do radical intermediário 3-NO2-Tyr●, o qual pode reagir em meio aquoso de diferentes maneiras, polimerizando, formando um filme resistivo na superfície do GCE e / ou sendo diretamente eletro-oxidado a um produto catiônico (segunda etapa). Os dados voltamétricos também mostraram que o grupo fenol da 3-NO2-Tyr é mais difícil de oxidar quando comparado às moléculas da p- e da o-Tyr. Além disso, diferentemente da p-Tyr e o-Tyr que não apresentam picos catódicos, a 3-NO2-Tyr sofre eletroredução em meio ácido em uma única etapa irreversível com a formação de dois produtos eletroativos. Tais processos foram atribuídos à redução do grupo nitro para formação da hidroxilamina e amina. Assim, é claramente demonstrado que a posição do grupo fenólico na molécula da Tyr, bem como a presença do grupo nitro, influenciam fortemente suas propriedades redox. O mecanismo redox da o-Tyr e da 3-NO2-Tyr são apresentados e discutidos. Um método voltamétrico para detecção e quantificação da 3-NO2-Tyr em meio neutro utilizando DPV foi também proposto e na faixa de concentração de 20 a 200 mol L-1, apresentou um coeficiente de correlação de 0,998 e um limite de detecção de 6,21 mol L-1. O conhecimento dos mecanismos redox dessas espécies investigadas, 7-mGuo, o-Tyr e 3-NO2-Tyr, assim como os métodos eletroanalíticos propostos para suas quantificações se correlacionam e são importantes para literatura, como conhecimentos básicos para futuras interpretações e aplicações na bioquímica molecular.Submitted by Mario BC (mario@bc.ufrpe.br) on 2022-04-08T13:46:55Z No. of bitstreams: 1 Raphael Fonseca do Nascimento.pdf: 4120740 bytes, checksum: af2041f02a913235571c97ca67be8af1 (MD5)Made available in DSpace on 2022-04-08T13:46:55Z (GMT). No. of bitstreams: 1 Raphael Fonseca do Nascimento.pdf: 4120740 bytes, checksum: af2041f02a913235571c97ca67be8af1 (MD5) Previous issue date: 2019-12-20Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPqapplication/pdfporUniversidade Federal Rural de PernambucoPrograma de Pós-Graduação em QuímicaUFRPEBrasilDepartamento de QuímicaBiomarcadorDoença humanaMecanismos redoxEstudo eletroquímicoEstudo eletroanalíticoCIENCIAS EXATAS E DA TERRA::QUIMICAEstudo eletroquímico e eletroanalítico dos biomarcadores de doenças humanas 7-metil-guanosina, orto tirosina e 3-nitro-tirosinainfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/doctoralThesis143564836222510089860060060060038064160554570910301571700325303117195-2555911436985713659info:eu-repo/semantics/openAccessreponame:Biblioteca Digital de Teses e Dissertações da UFRPEinstname:Universidade Federal Rural de Pernambuco (UFRPE)instacron:UFRPEORIGINALRaphael Fonseca do Nascimento.pdfRaphael Fonseca do Nascimento.pdfapplication/pdf4120740http://www.tede2.ufrpe.br:8080/tede2/bitstream/tede2/8570/2/Raphael+Fonseca+do+Nascimento.pdfaf2041f02a913235571c97ca67be8af1MD52LICENSElicense.txtlicense.txttext/plain; charset=utf-82165http://www.tede2.ufrpe.br:8080/tede2/bitstream/tede2/8570/1/license.txtbd3efa91386c1718a7f26a329fdcb468MD51tede2/85702022-04-08 10:46:55.433oai:tede2: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Biblioteca Digital de Teses e Dissertaçõeshttp://www.tede2.ufrpe.br:8080/tede/PUBhttp://www.tede2.ufrpe.br:8080/oai/requestbdtd@ufrpe.br ||bdtd@ufrpe.bropendoar:2024-05-28T12:37:09.668882Biblioteca Digital de Teses e Dissertações da UFRPE - Universidade Federal Rural de Pernambuco (UFRPE)false |
dc.title.por.fl_str_mv |
Estudo eletroquímico e eletroanalítico dos biomarcadores de doenças humanas 7-metil-guanosina, orto tirosina e 3-nitro-tirosina |
title |
Estudo eletroquímico e eletroanalítico dos biomarcadores de doenças humanas 7-metil-guanosina, orto tirosina e 3-nitro-tirosina |
spellingShingle |
Estudo eletroquímico e eletroanalítico dos biomarcadores de doenças humanas 7-metil-guanosina, orto tirosina e 3-nitro-tirosina NASCIMENTO, Raphael Fonseca do Biomarcador Doença humana Mecanismos redox Estudo eletroquímico Estudo eletroanalítico CIENCIAS EXATAS E DA TERRA::QUIMICA |
title_short |
Estudo eletroquímico e eletroanalítico dos biomarcadores de doenças humanas 7-metil-guanosina, orto tirosina e 3-nitro-tirosina |
title_full |
Estudo eletroquímico e eletroanalítico dos biomarcadores de doenças humanas 7-metil-guanosina, orto tirosina e 3-nitro-tirosina |
title_fullStr |
Estudo eletroquímico e eletroanalítico dos biomarcadores de doenças humanas 7-metil-guanosina, orto tirosina e 3-nitro-tirosina |
title_full_unstemmed |
Estudo eletroquímico e eletroanalítico dos biomarcadores de doenças humanas 7-metil-guanosina, orto tirosina e 3-nitro-tirosina |
title_sort |
Estudo eletroquímico e eletroanalítico dos biomarcadores de doenças humanas 7-metil-guanosina, orto tirosina e 3-nitro-tirosina |
author |
NASCIMENTO, Raphael Fonseca do |
author_facet |
NASCIMENTO, Raphael Fonseca do |
author_role |
author |
dc.contributor.advisor1.fl_str_mv |
OLIVEIRA, Severino Carlos Bezerra de |
dc.contributor.referee1.fl_str_mv |
NAVARRO, Marcelo |
dc.contributor.referee2.fl_str_mv |
RIBEIRO, Williame Farias |
dc.contributor.referee3.fl_str_mv |
CAMARA, Claudio Augusto Gomes da |
dc.contributor.referee4.fl_str_mv |
MORAES, Alex Souza |
dc.contributor.authorLattes.fl_str_mv |
http://lattes.cnpq.br/5598955460493259 |
dc.contributor.author.fl_str_mv |
NASCIMENTO, Raphael Fonseca do |
contributor_str_mv |
OLIVEIRA, Severino Carlos Bezerra de NAVARRO, Marcelo RIBEIRO, Williame Farias CAMARA, Claudio Augusto Gomes da MORAES, Alex Souza |
dc.subject.por.fl_str_mv |
Biomarcador Doença humana Mecanismos redox Estudo eletroquímico Estudo eletroanalítico |
topic |
Biomarcador Doença humana Mecanismos redox Estudo eletroquímico Estudo eletroanalítico CIENCIAS EXATAS E DA TERRA::QUIMICA |
dc.subject.cnpq.fl_str_mv |
CIENCIAS EXATAS E DA TERRA::QUIMICA |
description |
Oxidative damage in biological molecules, such as double-stranded DNA (dsDNA) and proteins are associated with numerous pathologies in the human body, such as cancer. Thus, it is of great relevance to investigate the redox mechanisms that occur in vivo for different biological processes. The present study aims to investigate the redox behavior of the biomarkers of human diseases, 7-methyl-guanosine (7-mGuo), ortho-tyrosina (o-Tyr) and 3-nitro-tyrosine (3-NO2-Tyr) on glassy carbon electrode (GCE) using voltammetric techniques, such as cyclic voltammetry (CV), square wave voltammetry (SWV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The electrochemical results of o-Tyr and 3-NO2-Tyr were also compared with the para-tyrosine (p-Tyr). Electroanalytical methodologies for the detection and quantification of these species were also investigated and developed in the absence and presence of possible interferences. Oxidation of the 7-mGuo on GCE occurs in single step pH-dependent irreversible pathway with the transfer of one electron and one proton with formation of polymer products absorbing on the electrode surface. An oxidation mechanism of 7-mGuo has been proposed. An electroanalytical method for quantification of 7-mGuo at physiological pH, using GCE and DPV was proposed, with a detection limit of 3.26 μmol L-1 and limit of quantification of 10,88 μmol L-1. Electrochemical detection of 7-mGuo was also investigated in the presence of potential interference of guanine, guanosine and 7-methylguanine (7-mGua). The study showed that the anodic peak of 7-mGuo suffered no interference of these species, since oxidation occurs in a very different potential. In general, the p- and o-Tyr undergo oxidation in a single irreversible step pH-dependent, with the transfer of one electron and one proton, from the phenolic group to formation of Tyr phenoxy radical (Tyr●). However, while the p-Tyr● radical preferably polymerizes, forming a resistive film on the GCE surface, the o-Tyr● reacts preferentially with water with formation of o- and p-quinone derivatives, that are adsorbed and reversibly reduced on the GCE surface. In relation the 3-NO2-Tyr its oxidation occurs, in general, in two irreversible steps. The first step is pH-dependent, while the second is pH-independent, indicating the absence of protons in the process. The first process correspond to the oxidation of the phenolic group to form 3-NO2-Tyr●, which reacts in different ways, polymerizing, forming a resistive film on the GCE surface and/or being directly electro-oxidized to a cationic product (second step). The voltammetric data also showed that the 3-NO2-Tyr phenol group is more difficult to oxidize when compared to p- and o-Tyr molecules. Moreover, unlike p-Tyr and o-Tyr that present no cathodic peak, 3-NO2-Tyr suffers in acid medium electro-reduction in a single irreversible step with formation of two electroactive products. Such processes were assigned to the reduction of the nitro group to form hydroxylamine and amine. Thus, is clearly demonstrated that the nitro group attached, as well as the phenolic group position at the Tyr molecule, strongly influence its redox properties. The redox mechanism of o-Tyr and 3-NO2-Tyr are presented and discussed. A voltammetric method for detection and quantification of 3-NO2-Tyr in physiological medium using DPV was also proposed and a concentration range of 20 to 200 μmol L-1, presented a correlation coefficient of 0.998 and a detection limit of 6, 21 μmol L-1. The knowledge of redox mechanisms of the biomarkers of human diseases, 7-mGuo, o-Tyr and 3-NO2-Tyr, as well as the proposed electroanalytical methods for their quantification correlates and are important in the literature, as basic knowledge to future interpretation and applications in molecular biochemistry. |
publishDate |
2019 |
dc.date.issued.fl_str_mv |
2019-12-20 |
dc.date.accessioned.fl_str_mv |
2022-04-08T13:46:55Z |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/doctoralThesis |
format |
doctoralThesis |
status_str |
publishedVersion |
dc.identifier.citation.fl_str_mv |
NASCIMENTO, Raphael Fonseca do. Estudo eletroquímico e eletroanalítico dos biomarcadores de doenças humanas 7-metil-guanosina, orto tirosina e 3-nitro-tirosina. 2019. 120 f. Tese (Programa de Pós-Graduação em Química) - Universidade Federal Rural de Pernambuco, Recife. |
dc.identifier.uri.fl_str_mv |
http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/8570 |
identifier_str_mv |
NASCIMENTO, Raphael Fonseca do. Estudo eletroquímico e eletroanalítico dos biomarcadores de doenças humanas 7-metil-guanosina, orto tirosina e 3-nitro-tirosina. 2019. 120 f. Tese (Programa de Pós-Graduação em Química) - Universidade Federal Rural de Pernambuco, Recife. |
url |
http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/8570 |
dc.language.iso.fl_str_mv |
por |
language |
por |
dc.relation.program.fl_str_mv |
1435648362225100898 |
dc.relation.confidence.fl_str_mv |
600 600 600 600 |
dc.relation.department.fl_str_mv |
3806416055457091030 |
dc.relation.cnpq.fl_str_mv |
1571700325303117195 |
dc.relation.sponsorship.fl_str_mv |
-2555911436985713659 |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.format.none.fl_str_mv |
application/pdf |
dc.publisher.none.fl_str_mv |
Universidade Federal Rural de Pernambuco |
dc.publisher.program.fl_str_mv |
Programa de Pós-Graduação em Química |
dc.publisher.initials.fl_str_mv |
UFRPE |
dc.publisher.country.fl_str_mv |
Brasil |
dc.publisher.department.fl_str_mv |
Departamento de Química |
publisher.none.fl_str_mv |
Universidade Federal Rural de Pernambuco |
dc.source.none.fl_str_mv |
reponame:Biblioteca Digital de Teses e Dissertações da UFRPE instname:Universidade Federal Rural de Pernambuco (UFRPE) instacron:UFRPE |
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Universidade Federal Rural de Pernambuco (UFRPE) |
instacron_str |
UFRPE |
institution |
UFRPE |
reponame_str |
Biblioteca Digital de Teses e Dissertações da UFRPE |
collection |
Biblioteca Digital de Teses e Dissertações da UFRPE |
bitstream.url.fl_str_mv |
http://www.tede2.ufrpe.br:8080/tede2/bitstream/tede2/8570/2/Raphael+Fonseca+do+Nascimento.pdf http://www.tede2.ufrpe.br:8080/tede2/bitstream/tede2/8570/1/license.txt |
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MD5 MD5 |
repository.name.fl_str_mv |
Biblioteca Digital de Teses e Dissertações da UFRPE - Universidade Federal Rural de Pernambuco (UFRPE) |
repository.mail.fl_str_mv |
bdtd@ufrpe.br ||bdtd@ufrpe.br |
_version_ |
1810102264767971328 |