Clécio Klitzke - Academia.edu (original) (raw)

Papers by Clécio Klitzke

Catalysis Science & Technology, 2021

Herein, we report a comparative study of ethylene activation and 1-hexene isomerization carried o... more Herein, we report a comparative study of ethylene activation and 1-hexene isomerization carried out with isomeric neutral and cationic methallyl nickel complexes L1Ni(η3-C3H5) and [L1Ni(η3-C3H5)][B(ArF)4] in the presence of borane co-catalysts.

In oxygenic photosynthetic organisms, photosystem II (PSII) is a unique membrane protein complex ... more In oxygenic photosynthetic organisms, photosystem II (PSII) is a unique membrane protein complex that catalyzes light driven oxidation of water. PSII undergoes frequent damage due to its demanding photochemistry. However, many facets of its repair and reassembly following photodamage remain unknown. We have discovered a novel PSII subcomplex that lacks five key PSII core reaction center polypeptides: D1, D2, PsbE, PsbF, and PsbI. This pigment protein complex does contain the PSII core antenna proteins CP47 and CP43, as well as most of their associated low molecular mass subunits, and the assembly factor Psb27. Immunoblotting analysis, multiple mass spectrometry techniques, and ultrafast spectroscopic results supported the absence of a functional reaction center in this chlorophyll protein complex. We therefore refer to it as the No Reaction Center complex (NRC). Additionally, genetic deletion of PsbO on the PSII lumenal side resulted in an increased NRC population, indicative of a f...

ACS National Meeting Book of Abstracts

Background : A broader view of living systems complexity is bringing important contributions to b... more Background : A broader view of living systems complexity is bringing important contributions to biological sciences, since the genome expression is affected by other classes of molecules, which in their turn interact themselves in cellular metabolic pathways and biochemical networks. This level of information has been made possible by the emergence of the omic strategies, such as proteomics, metabolomics and lipidomics, that are mainly based on mass spectrometry (MS) platforms. MS has presented an incredible development over the last years, evolving to a powerful and universal analytical technique. Its ability to analyze proteins and small molecules such as lipids, sugars and metabolites at the structural level, with sensitivity and speed inconceivable a few years ago, is the major driving force in the omic fields. The development of electrospray and matrix-assisted laser desorption/ionization (MALDI) ionization techniques has decisively contributed to the many applications of this ...

TrAC Trends in Analytical Chemistry, 2011

Gas chromatography coupled to high-resolution time-of flight mass spectrometry (GC-HR-TOF-MS) is ... more Gas chromatography coupled to high-resolution time-of flight mass spectrometry (GC-HR-TOF-MS) is a powerful analytical technique with excellent capabilities due to its high sensitivity in full-spectrum-acquisition mode together with its resolving power and accurate-mass measurements. These features make this technique very attractive in qualitative analysis, especially for wide-scope screening of a large number of organic contaminants and residues at trace levels.Full-spectrum

Orientador: Marcos Nogueira EberlinTese (doutorado) - Universidade Estadual de Campinas, Institut... more Orientador: Marcos Nogueira EberlinTese (doutorado) - Universidade Estadual de Campinas, Instituto de QuímicaResumo: O petróleo é uma mistura complexa, constituída de milhares de compostos e sua caracterização é fundamental em diversos processos da indústria petrolífera. A abordagem moderna para a caracterização total dos compostos polares (N, O, S) do petróleo é através da petroleômica, utilizando a espectrometria de massas de altíssima resolução e exatidão obtida em espectrômetros de ressonância ciclotrônica de íons com análise por transformada de Fourier (FT-ICR MS). FT-ICR MS é o equipamento ideal para estas análises, no entanto a literatura carece de informações quanto a otimização do número de scans e do efeito da resolução na análise petroleômica. Determinamos como condições ideais para a análise destas amostras de altíssima complexidade a obtenção de espectros de MS com poder de resolução de 400.000 em m/z 400 e acúmulo de 100 mscans. Foram analisados também os compostos pol...

O petroleo e uma mistura complexa, constituida de milhares de compostos e sua caracterizacao e fu... more O petroleo e uma mistura complexa, constituida de milhares de compostos e sua caracterizacao e fundamental em diversos processos da industria petrolifera. A abordagem moderna para a caracterizacao total dos compostos polares (N, O, S) do petroleo e atraves da petroleomica, utilizando a espectrometria de massas de altissima resolucao e exatidao obtida em espectrometros de ressonância ciclotronica de ions com analise por transformada de Fourier (FT-ICR MS). FT-ICR MS e o equipamento ideal para estas analises, no entanto a literatura carece de informacoes quanto a otimizacao do numero de scans e do efeito da resolucao na analise petroleomica. Determinamos como condicoes ideais para a analise destas amostras de altissima complexidade a obtencao de espectros de MS com poder de resolucao de 400.000 em m/z 400 e acumulo de 100 mscans. Foram analisados tambem os compostos polares presentes em outras fontes de combustiveis fosseis, como carvao mineral e folhelho. Os resultados mostraram padroes distintos em relacao a origem do material e possivelmente ao grau de evolucao termica. Comparamos a analise por FT-ICR MS dos acidos carboxilicos de amostras de petroleo com os resultados das analise de fracoes acidas por FAB MS obtidas no CENPES . PETROBRAS, mostrando que as analises por FT-ICR MS apresentam resultados superiores na identificacao da distribuicao de DBE sendo que por FAB MS nao temos informacoes relativas a DBE superior a 7. A analise abrangente da composicao de acidos do petroleo e de extrema importância com conta da corrosao e formacao de depositos e emulsoes, dependentes da composicao destes acidos. Comparamos alguns resultados da analise por FT-ICR MS com TOF MS (UHRT) de altissima resolucao, 100.000. Os resultados obtidos com UHRT MS estao proximos as analises por FT-ICR MS com 200.000 de resolucao em m/z 400. Obtivemos a identificacao de boa parte das classes de heteroatomos uteis nas analises petroleomicas. Analisamos por Travelling Wave Ion Mobility Mass Spectrometry (TWIM MS) padroes de acidos, destilados e amostras de petroleo. Os resultados obtidos mostraram uma tendencia da reducao do drift time com o aumento da DBE dos analitos. As amostras de petroleo tambem revelaram perfis distintos para diferentes faixas de drift time, sendo possivel diferenciar classes de compostos polares (O2, N e NO). Os resultados obtidos mostraram o grande potencial da analise por FT-ICR MS e UHRT MS, complementados pela analise estrutural fornecida pela mobilidade ionica com o uso da TWIM MS. Abstract

Desde a formulacao da hipotese de coevolucao entre plantas e borboletas por Ehrlich e Raven em 19... more Desde a formulacao da hipotese de coevolucao entre plantas e borboletas por Ehrlich e Raven em 1964 poucos trabalhos tem demonstrado a sua existencia no sentido estrito. evidenciando-se geralmente o fenomeno de colonizacao. O objetivo deste trabalho e estudar as interacoes entre um qrupo restrito de borboletas (Troidini) e suas unicas plantas de alimento larval (Aristolochia) com respeito a mediacao quimica na utilizacao das plantas hospedeiras pelas larvas. Para isto foram criadas larvas de diferentes especies de Troidini em diferentes especies de (Aristolochia) encontradas na regiao sudeste brasileira. Com estes dados e informacoes da literatura foi possivel estabelecer a utilizacao e preferencia por cada especie vegetal por cada especie de Troidini. A analise quimica de 11 especies de Aristolochia mostrou a existencia de tres classes de compostos secundarios mais abundantes: acidos aristoloquicos (nitrofenantrenos), acidos labdanoicos (diterpenos) e alcaloides (nao identificados neste trabalho). A presenca e ausencia destes compostos permitiu a reuniao destas especies em tres grupos que sao utilizados diferentemente pelos Troidini. A analise quimica de 17 especies de Troidini mostrou a presenca de acidos aristoloquicos e alcaloides. Surpreendentemente larvas de B. polydamas criadas em A. Galeata, uma especie sem acidos aristoloquicos nas folhas, apresentaram estes compostos indicando a possibilidade de sua biossintese pelas larvas. Esta especie so empupou em A. Galeata com o acrescimo de acidos aristoloquicos. Isto indica a necessidade destes compostos para o total desenvolvimento das larvas nesta planta. Na natureza e possivel observar larvas comendo outras partes da planta que contem estes compostos tais como ramos, flores e frutos. Os acidos labdanoicos apresentaram efeito fagoinibidor nas especies testadas sendo que P. neophilus e B. polydamas sao menos sensiveis a estes compostos. Estas duas especies tambem apresentaram aumento de consumo na presenca de AAs. o que indica um efeito fagoestimulante desdes compostos. Algumas fracoes neutras polares tambem apresentaram atividade fagoinibidora. Estes resultados permitem a reformulacao da hipotese de coevolucao entre dois grupos por Brown et. al. (1991a) Abstract

Proceedings of the National Academy of Sciences, 2019

In oxygenic photosynthetic organisms, photosystem II (PSII) is a unique membrane protein complex ... more In oxygenic photosynthetic organisms, photosystem II (PSII) is a unique membrane protein complex that catalyzes light-driven oxidation of water. PSII undergoes frequent damage due to its demanding photochemistry. It must undergo a repair and reassembly process following photodamage, many facets of which remain unknown. We have discovered a PSII subcomplex that lacks 5 key PSII core reaction center polypeptides: D1, D2, PsbE, PsbF, and PsbI. This pigment–protein complex does contain the PSII core antenna proteins CP47 and CP43, as well as most of their associated low molecular mass subunits, and the assembly factor Psb27. Immunoblotting, mass spectrometry, and ultrafast spectroscopic results support the absence of a functional reaction center in this complex, which we call the “no reaction center” complex (NRC). Analytical ultracentrifugation and clear native PAGE analysis show that NRC is a stable pigment–protein complex and not a mixture of free CP47 and CP43 proteins. NRC appears ...

Fuel, 2018

Heavy oils are characterized by high proportions of asphaltenes, a class of polyaromatic hydrocar... more Heavy oils are characterized by high proportions of asphaltenes, a class of polyaromatic hydrocarbons whose structures remain unknown. Previous work based on asphaltene physical-chemical properties and extensive spectroscopic and computational methods has generated controversy about two possible general conformations: island and archipelago. To address this controversy, this study employed a systematic integrative approach involving ion mobility (IMS), theoretical calculations, ultra-high resolution mass spectrometry (UHR MS), and pyrolysis gas chromatography coupled to high-resolution mass spectrometry (Py-GC-HR MS) to evaluate the composition and structure of asphaltenes. Two Brazilian oils with different API grades (heavy and light) were analyzed and compared. The comparison of IMS data demonstrated that isobaric asphaltenes from light and heavy oils shared similar collisional cross sections (CCS) with different homologous series in the experiments. Two-dimensional (2D) difference mobility plots showed that minor compounds in these fractions possess different CCS. The combination of CCS data with UHR MS and Py-GC-HR MS still was not enough to indicate if there is a single asphaltene architecture in the studied samples. However, the obtained data were structurally slightly more consistent with the island architecture. Furthermore, the systematic combination of mass spectrometry techniques and calculations provided a reliable method for fingerprinting complex geological samples and providing structural information.

Journal of mass spectrometry : JMS, 2016

The Analyst, 2016

A comprehensive investigation of the formation of fullerenes from carbonaceous materials using la... more A comprehensive investigation of the formation of fullerenes from carbonaceous materials using laser-based mass spectrometry techniques.

Endocrine, 2005

Many physiologic changes related to light-dark cycles and antioxidant effects have been related t... more Many physiologic changes related to light-dark cycles and antioxidant effects have been related to melatonin (N-acetyl-5-methoxytryptamine) and its metabolites, N 1-acetyl-N 2-formyl-5-methoxykynuramine (AFMK) and N 1-acetyl-5-methoxykynuramine (AMK). In this review, we discuss some methodologies, in particular, those employing high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) assays to quantitatively determine melatonin, AFMK, and AMK. These approaches offer a highly specific and an accurate quantification of melatonin and its metabolites. These characteristics are essential to point out correctly the biological effects of these compounds in physiological and pathological conditions.

International Journal for Ion Mobility Spectrometry, 2013

Ion mobility spectrometry (IMS) separates ions while they travel through a buffer gas under the i... more Ion mobility spectrometry (IMS) separates ions while they travel through a buffer gas under the influence of an electrical field. The separation is affected by mass and charge but most particularly by shape (collision cross section). When coupled to MS, IMS-MS offers therefore a powerful tool for structural elucidation and isomer separation. Systematic studies aimed to compare and quantitate the effects of structural changes on drift time such as length and ramification of carbon chain, unsaturation, geometrical isomerism (cis/trans isomers for instance), cyclization and ring size are, however, scarce. Herein we used traveling wave ion mobility mass spectrometry (TWIM-MS) to systematically evaluate the relationship between structure and drift time. For that, a series of deprotonated carboxylic acids were used as model ions with a carboxylate "charge tag" for gas phase MS manipulation. Carboxylic acids showed a near linear correlation between the increase of carbon number and the increase of collision cross section (CCS). The number of double bonds changes slightly the CCS of unsaturated acids. No differences in drift time and no significant differences in CCS of cisand trans-double bond of oleic and elaidic acids were observed. Cyclization considerably reduces the CCS. In cyclic carboxylic acids, the increase of double bonds and aromatization significantly reduces the CCS and the drift times. The use of a more polarizable drift gas, CO 2, improved in some cases the separation, as for biomarker isomers of steranoic acids. The β-isomer (cis-decaline) has smaller CCS and therefore displayed lower drift time compared to the α-isomer (trans-decaline). Structural changes revealed by calculations were correlated with trends in drift times.

The Open Microbiology Journal, 2011

This study compared the proteomic profile of outer membrane proteins (OMPs) from one strain of at... more This study compared the proteomic profile of outer membrane proteins (OMPs) from one strain of atypical enteropathogenic Escherichia coli (aEPEC) and one of typical EPEC (tEPEC). The OMPs fractions were obtained using sarcosine extraction, and analyzed by one-and two-dimensional gel electrophoresis (1DE and 2DE, respectively). The 1DE OMPs analysis of typical and atypical EPEC evidenced similar patterns; however, the 2DE OMP profile from the aEPEC revealed more protein spots in the 40-to 70-kDa region. 2DE image analysis identified 159 protein spots in both strains whereas 53 protein spots were observed only in tEPEC and 128 were observed only in aEPEC. Remarkably, 41.5% of aEPEC spots showed higher levels of expression compared to tEPEC, some of which with two, others four or even five times more. Twenty-four selected spots were identified using MALDI-TOF mass spectrometry and they corresponded to proteins involved in cell structure and metabolism, as well as in gene regulation. Some of these proteins showed similarity with proteins identified in other E. coli pathotypes. Besides, the differential expression of some proteins in aEPEC may suggest that it could be related to their features that ascertain the adaptation to distinct environments and the worldwide spread distribution of these pathogens.

Tetrahedron Letters, 2001

A short synthesis of hydroxylated indolizidines is reported. The key steps were the allylation of... more A short synthesis of hydroxylated indolizidines is reported. The key steps were the allylation of chiral cyclic N-acyliminium ions derived from malic and tartaric acids, followed by ring-closing metathesis.

Catalysis Science & Technology, 2021

Herein, we report a comparative study of ethylene activation and 1-hexene isomerization carried o... more Herein, we report a comparative study of ethylene activation and 1-hexene isomerization carried out with isomeric neutral and cationic methallyl nickel complexes L1Ni(η3-C3H5) and [L1Ni(η3-C3H5)][B(ArF)4] in the presence of borane co-catalysts.

In oxygenic photosynthetic organisms, photosystem II (PSII) is a unique membrane protein complex ... more In oxygenic photosynthetic organisms, photosystem II (PSII) is a unique membrane protein complex that catalyzes light driven oxidation of water. PSII undergoes frequent damage due to its demanding photochemistry. However, many facets of its repair and reassembly following photodamage remain unknown. We have discovered a novel PSII subcomplex that lacks five key PSII core reaction center polypeptides: D1, D2, PsbE, PsbF, and PsbI. This pigment protein complex does contain the PSII core antenna proteins CP47 and CP43, as well as most of their associated low molecular mass subunits, and the assembly factor Psb27. Immunoblotting analysis, multiple mass spectrometry techniques, and ultrafast spectroscopic results supported the absence of a functional reaction center in this chlorophyll protein complex. We therefore refer to it as the No Reaction Center complex (NRC). Additionally, genetic deletion of PsbO on the PSII lumenal side resulted in an increased NRC population, indicative of a f...

ACS National Meeting Book of Abstracts

Background : A broader view of living systems complexity is bringing important contributions to b... more Background : A broader view of living systems complexity is bringing important contributions to biological sciences, since the genome expression is affected by other classes of molecules, which in their turn interact themselves in cellular metabolic pathways and biochemical networks. This level of information has been made possible by the emergence of the omic strategies, such as proteomics, metabolomics and lipidomics, that are mainly based on mass spectrometry (MS) platforms. MS has presented an incredible development over the last years, evolving to a powerful and universal analytical technique. Its ability to analyze proteins and small molecules such as lipids, sugars and metabolites at the structural level, with sensitivity and speed inconceivable a few years ago, is the major driving force in the omic fields. The development of electrospray and matrix-assisted laser desorption/ionization (MALDI) ionization techniques has decisively contributed to the many applications of this ...

TrAC Trends in Analytical Chemistry, 2011

Gas chromatography coupled to high-resolution time-of flight mass spectrometry (GC-HR-TOF-MS) is ... more Gas chromatography coupled to high-resolution time-of flight mass spectrometry (GC-HR-TOF-MS) is a powerful analytical technique with excellent capabilities due to its high sensitivity in full-spectrum-acquisition mode together with its resolving power and accurate-mass measurements. These features make this technique very attractive in qualitative analysis, especially for wide-scope screening of a large number of organic contaminants and residues at trace levels.Full-spectrum

Orientador: Marcos Nogueira EberlinTese (doutorado) - Universidade Estadual de Campinas, Institut... more Orientador: Marcos Nogueira EberlinTese (doutorado) - Universidade Estadual de Campinas, Instituto de QuímicaResumo: O petróleo é uma mistura complexa, constituída de milhares de compostos e sua caracterização é fundamental em diversos processos da indústria petrolífera. A abordagem moderna para a caracterização total dos compostos polares (N, O, S) do petróleo é através da petroleômica, utilizando a espectrometria de massas de altíssima resolução e exatidão obtida em espectrômetros de ressonância ciclotrônica de íons com análise por transformada de Fourier (FT-ICR MS). FT-ICR MS é o equipamento ideal para estas análises, no entanto a literatura carece de informações quanto a otimização do número de scans e do efeito da resolução na análise petroleômica. Determinamos como condições ideais para a análise destas amostras de altíssima complexidade a obtenção de espectros de MS com poder de resolução de 400.000 em m/z 400 e acúmulo de 100 mscans. Foram analisados também os compostos pol...

O petroleo e uma mistura complexa, constituida de milhares de compostos e sua caracterizacao e fu... more O petroleo e uma mistura complexa, constituida de milhares de compostos e sua caracterizacao e fundamental em diversos processos da industria petrolifera. A abordagem moderna para a caracterizacao total dos compostos polares (N, O, S) do petroleo e atraves da petroleomica, utilizando a espectrometria de massas de altissima resolucao e exatidao obtida em espectrometros de ressonância ciclotronica de ions com analise por transformada de Fourier (FT-ICR MS). FT-ICR MS e o equipamento ideal para estas analises, no entanto a literatura carece de informacoes quanto a otimizacao do numero de scans e do efeito da resolucao na analise petroleomica. Determinamos como condicoes ideais para a analise destas amostras de altissima complexidade a obtencao de espectros de MS com poder de resolucao de 400.000 em m/z 400 e acumulo de 100 mscans. Foram analisados tambem os compostos polares presentes em outras fontes de combustiveis fosseis, como carvao mineral e folhelho. Os resultados mostraram padroes distintos em relacao a origem do material e possivelmente ao grau de evolucao termica. Comparamos a analise por FT-ICR MS dos acidos carboxilicos de amostras de petroleo com os resultados das analise de fracoes acidas por FAB MS obtidas no CENPES . PETROBRAS, mostrando que as analises por FT-ICR MS apresentam resultados superiores na identificacao da distribuicao de DBE sendo que por FAB MS nao temos informacoes relativas a DBE superior a 7. A analise abrangente da composicao de acidos do petroleo e de extrema importância com conta da corrosao e formacao de depositos e emulsoes, dependentes da composicao destes acidos. Comparamos alguns resultados da analise por FT-ICR MS com TOF MS (UHRT) de altissima resolucao, 100.000. Os resultados obtidos com UHRT MS estao proximos as analises por FT-ICR MS com 200.000 de resolucao em m/z 400. Obtivemos a identificacao de boa parte das classes de heteroatomos uteis nas analises petroleomicas. Analisamos por Travelling Wave Ion Mobility Mass Spectrometry (TWIM MS) padroes de acidos, destilados e amostras de petroleo. Os resultados obtidos mostraram uma tendencia da reducao do drift time com o aumento da DBE dos analitos. As amostras de petroleo tambem revelaram perfis distintos para diferentes faixas de drift time, sendo possivel diferenciar classes de compostos polares (O2, N e NO). Os resultados obtidos mostraram o grande potencial da analise por FT-ICR MS e UHRT MS, complementados pela analise estrutural fornecida pela mobilidade ionica com o uso da TWIM MS. Abstract

Desde a formulacao da hipotese de coevolucao entre plantas e borboletas por Ehrlich e Raven em 19... more Desde a formulacao da hipotese de coevolucao entre plantas e borboletas por Ehrlich e Raven em 1964 poucos trabalhos tem demonstrado a sua existencia no sentido estrito. evidenciando-se geralmente o fenomeno de colonizacao. O objetivo deste trabalho e estudar as interacoes entre um qrupo restrito de borboletas (Troidini) e suas unicas plantas de alimento larval (Aristolochia) com respeito a mediacao quimica na utilizacao das plantas hospedeiras pelas larvas. Para isto foram criadas larvas de diferentes especies de Troidini em diferentes especies de (Aristolochia) encontradas na regiao sudeste brasileira. Com estes dados e informacoes da literatura foi possivel estabelecer a utilizacao e preferencia por cada especie vegetal por cada especie de Troidini. A analise quimica de 11 especies de Aristolochia mostrou a existencia de tres classes de compostos secundarios mais abundantes: acidos aristoloquicos (nitrofenantrenos), acidos labdanoicos (diterpenos) e alcaloides (nao identificados neste trabalho). A presenca e ausencia destes compostos permitiu a reuniao destas especies em tres grupos que sao utilizados diferentemente pelos Troidini. A analise quimica de 17 especies de Troidini mostrou a presenca de acidos aristoloquicos e alcaloides. Surpreendentemente larvas de B. polydamas criadas em A. Galeata, uma especie sem acidos aristoloquicos nas folhas, apresentaram estes compostos indicando a possibilidade de sua biossintese pelas larvas. Esta especie so empupou em A. Galeata com o acrescimo de acidos aristoloquicos. Isto indica a necessidade destes compostos para o total desenvolvimento das larvas nesta planta. Na natureza e possivel observar larvas comendo outras partes da planta que contem estes compostos tais como ramos, flores e frutos. Os acidos labdanoicos apresentaram efeito fagoinibidor nas especies testadas sendo que P. neophilus e B. polydamas sao menos sensiveis a estes compostos. Estas duas especies tambem apresentaram aumento de consumo na presenca de AAs. o que indica um efeito fagoestimulante desdes compostos. Algumas fracoes neutras polares tambem apresentaram atividade fagoinibidora. Estes resultados permitem a reformulacao da hipotese de coevolucao entre dois grupos por Brown et. al. (1991a) Abstract

Proceedings of the National Academy of Sciences, 2019

In oxygenic photosynthetic organisms, photosystem II (PSII) is a unique membrane protein complex ... more In oxygenic photosynthetic organisms, photosystem II (PSII) is a unique membrane protein complex that catalyzes light-driven oxidation of water. PSII undergoes frequent damage due to its demanding photochemistry. It must undergo a repair and reassembly process following photodamage, many facets of which remain unknown. We have discovered a PSII subcomplex that lacks 5 key PSII core reaction center polypeptides: D1, D2, PsbE, PsbF, and PsbI. This pigment–protein complex does contain the PSII core antenna proteins CP47 and CP43, as well as most of their associated low molecular mass subunits, and the assembly factor Psb27. Immunoblotting, mass spectrometry, and ultrafast spectroscopic results support the absence of a functional reaction center in this complex, which we call the “no reaction center” complex (NRC). Analytical ultracentrifugation and clear native PAGE analysis show that NRC is a stable pigment–protein complex and not a mixture of free CP47 and CP43 proteins. NRC appears ...

Fuel, 2018

Heavy oils are characterized by high proportions of asphaltenes, a class of polyaromatic hydrocar... more Heavy oils are characterized by high proportions of asphaltenes, a class of polyaromatic hydrocarbons whose structures remain unknown. Previous work based on asphaltene physical-chemical properties and extensive spectroscopic and computational methods has generated controversy about two possible general conformations: island and archipelago. To address this controversy, this study employed a systematic integrative approach involving ion mobility (IMS), theoretical calculations, ultra-high resolution mass spectrometry (UHR MS), and pyrolysis gas chromatography coupled to high-resolution mass spectrometry (Py-GC-HR MS) to evaluate the composition and structure of asphaltenes. Two Brazilian oils with different API grades (heavy and light) were analyzed and compared. The comparison of IMS data demonstrated that isobaric asphaltenes from light and heavy oils shared similar collisional cross sections (CCS) with different homologous series in the experiments. Two-dimensional (2D) difference mobility plots showed that minor compounds in these fractions possess different CCS. The combination of CCS data with UHR MS and Py-GC-HR MS still was not enough to indicate if there is a single asphaltene architecture in the studied samples. However, the obtained data were structurally slightly more consistent with the island architecture. Furthermore, the systematic combination of mass spectrometry techniques and calculations provided a reliable method for fingerprinting complex geological samples and providing structural information.

Journal of mass spectrometry : JMS, 2016

The Analyst, 2016

A comprehensive investigation of the formation of fullerenes from carbonaceous materials using la... more A comprehensive investigation of the formation of fullerenes from carbonaceous materials using laser-based mass spectrometry techniques.

Endocrine, 2005

Many physiologic changes related to light-dark cycles and antioxidant effects have been related t... more Many physiologic changes related to light-dark cycles and antioxidant effects have been related to melatonin (N-acetyl-5-methoxytryptamine) and its metabolites, N 1-acetyl-N 2-formyl-5-methoxykynuramine (AFMK) and N 1-acetyl-5-methoxykynuramine (AMK). In this review, we discuss some methodologies, in particular, those employing high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) assays to quantitatively determine melatonin, AFMK, and AMK. These approaches offer a highly specific and an accurate quantification of melatonin and its metabolites. These characteristics are essential to point out correctly the biological effects of these compounds in physiological and pathological conditions.

International Journal for Ion Mobility Spectrometry, 2013

Ion mobility spectrometry (IMS) separates ions while they travel through a buffer gas under the i... more Ion mobility spectrometry (IMS) separates ions while they travel through a buffer gas under the influence of an electrical field. The separation is affected by mass and charge but most particularly by shape (collision cross section). When coupled to MS, IMS-MS offers therefore a powerful tool for structural elucidation and isomer separation. Systematic studies aimed to compare and quantitate the effects of structural changes on drift time such as length and ramification of carbon chain, unsaturation, geometrical isomerism (cis/trans isomers for instance), cyclization and ring size are, however, scarce. Herein we used traveling wave ion mobility mass spectrometry (TWIM-MS) to systematically evaluate the relationship between structure and drift time. For that, a series of deprotonated carboxylic acids were used as model ions with a carboxylate "charge tag" for gas phase MS manipulation. Carboxylic acids showed a near linear correlation between the increase of carbon number and the increase of collision cross section (CCS). The number of double bonds changes slightly the CCS of unsaturated acids. No differences in drift time and no significant differences in CCS of cisand trans-double bond of oleic and elaidic acids were observed. Cyclization considerably reduces the CCS. In cyclic carboxylic acids, the increase of double bonds and aromatization significantly reduces the CCS and the drift times. The use of a more polarizable drift gas, CO 2, improved in some cases the separation, as for biomarker isomers of steranoic acids. The β-isomer (cis-decaline) has smaller CCS and therefore displayed lower drift time compared to the α-isomer (trans-decaline). Structural changes revealed by calculations were correlated with trends in drift times.

The Open Microbiology Journal, 2011

This study compared the proteomic profile of outer membrane proteins (OMPs) from one strain of at... more This study compared the proteomic profile of outer membrane proteins (OMPs) from one strain of atypical enteropathogenic Escherichia coli (aEPEC) and one of typical EPEC (tEPEC). The OMPs fractions were obtained using sarcosine extraction, and analyzed by one-and two-dimensional gel electrophoresis (1DE and 2DE, respectively). The 1DE OMPs analysis of typical and atypical EPEC evidenced similar patterns; however, the 2DE OMP profile from the aEPEC revealed more protein spots in the 40-to 70-kDa region. 2DE image analysis identified 159 protein spots in both strains whereas 53 protein spots were observed only in tEPEC and 128 were observed only in aEPEC. Remarkably, 41.5% of aEPEC spots showed higher levels of expression compared to tEPEC, some of which with two, others four or even five times more. Twenty-four selected spots were identified using MALDI-TOF mass spectrometry and they corresponded to proteins involved in cell structure and metabolism, as well as in gene regulation. Some of these proteins showed similarity with proteins identified in other E. coli pathotypes. Besides, the differential expression of some proteins in aEPEC may suggest that it could be related to their features that ascertain the adaptation to distinct environments and the worldwide spread distribution of these pathogens.

Tetrahedron Letters, 2001

A short synthesis of hydroxylated indolizidines is reported. The key steps were the allylation of... more A short synthesis of hydroxylated indolizidines is reported. The key steps were the allylation of chiral cyclic N-acyliminium ions derived from malic and tartaric acids, followed by ring-closing metathesis.