Luiz Alberto Beraldo Moraes - Profile on Academia.edu (original) (raw)

Papers by Luiz Alberto Beraldo Moraes

Ironporphyrin immobilized onto montmorillonite as a biomimetical model for azo dye oxidation

International Biodeterioration & Biodegradation, 2008

In this work, we studied the oxidation of the azo dye Disperse Orange 3 (DO3) by hydrogen peroxid... more In this work, we studied the oxidation of the azo dye Disperse Orange 3 (DO3) by hydrogen peroxide, catalyzed by 5,10,15,20-tetrakis(4-N-methylpyridyl)porphyrin iron(III) chloride immobilized onto montmorillonite K10, FeP-K10. Results showed that the FeP-K10/H2O2 system is efficient for discoloration of the DO3 dye, especially at pH 3.0. The catalyst was shown to be relatively stable and could be recycled many times,

Organometallics, Oct 13, 2001

The 3-(dimethylamino)-1,1-dimethyl-1H-azaphosphiren-1-ium ion (3), the first member of the hither... more The 3-(dimethylamino)-1,1-dimethyl-1H-azaphosphiren-1-ium ion (3), the first member of the hitherto unknown class of azaphosphirenium ions and the first N,P-analogue of the aromatic cyclopropenyl cation, is generated in the gas phase via 70 eV electron ionization and demetalation of a ferriphosphaalkene (1) and rapid cyclization of the incipient phosphavinyl cation (2). Spontaneous cyclization of 2 to 3 is predicted by Becke3LYP/6-311++G(d,p) calculations, and the structure and reactivity of 3 is probed via collision-induced dissociation and ion-molecule reactions performed via pentaquadrupole mass spectrometry. Gaseous 3 fails to coordinate efficiently with nitrogen and oxygen nucleophiles, but it forms stable adduct ions with phosphorus and sulfur nucleophiles. The adducts of 3 with P and S nucleophiles are likely favored by the incorporation of relatively strong and rare PdS and PdP bonds and through extensive charge delocalization involving dimethylamino substituents. With isoprene, an adduct ion is also readily formed presumably via [4 + 2 + ] cycloaddition (followed by spontaneous ring opening), a reaction which is well documented for phosphenium ions both in solution and in the gas phase.

Journal of the American Chemical Society, Oct 17, 1998

In the gas phase, m-and p-dehydrobenzoyl cations display strong duality of chemical behavior. The... more In the gas phase, m-and p-dehydrobenzoyl cations display strong duality of chemical behavior. The ions react selectively as either free radicals or acylium ions, depending on the choice of the neutral reaction partner. Transacetalization with 2-methyl-1,3-dioxolane, ketalization with 2-methoxyethanol, and epoxide ring expansion with epichlorohydrin demonstrate their acylium ion reactivity, whereas • SCH 3 abstraction with dimethyl disulfide demonstrates their free radical reactivity. In one-pot reactions with gaseous mixtures of epichlorohydrin and dimethyl disulfide, the m-and p-dehydrobenzoyl cations react selectively at either site to form the two monoderivatized ions in variable but controlled yields; further reaction at either the remaining radical or the acylium charge site forms a single biderivatized ion as the final product. The o-dehydrobenzoyl cation also displays the expected radical and acylium ion reactivities. But for the ortho isomer, binding of the nucleophilic neutral to the free or derivatized C + dO group facilitates reactions at the radical site. Hence, the ortho isomer displays a unique behavior; its acylium ion reactions either occur simultaneously with, or are followed by, H-abstraction radical reactions. As shown by ab initio calculations, the three isomers display σ-localized odd-spin and π-delocalized charge densities, which characterize distonic structures with molecular orbital-separated radical and charge sites. The dehydrobenzoyl cations are also, according to the calculations, the most stable among 19 of the most feasible C 7 H 4 O +• isomers.

Journal of Mass Spectrometry, 2002

This article discusses the application of gas-phase ion/molecule reactions for fine structural el... more This article discusses the application of gas-phase ion/molecule reactions for fine structural elucidation in mass spectrometry. This approach is illustrated via a representative collection of class-and functional group-selective reactions, a few of historical relevance as well as by more recent and instructive examples, and their applications. The focus is on reactions performed under well-controlled conditions of sequential mass spectrometry, discussing key mechanistic details and potential applications. Recent and innovative strategies that allow these reactions to be performed under ambient conditions, making this fast, selective and sensitive approach for structural investigation much more generally applicable, are also discussed.

Gas-phase chemistry of acylium ions. Seven-to-five ring contraction of 1,3-dioxepane and 1,3-dioxep-5-ene

Journal of Mass Spectrometry, Jun 1, 1999

ABSTRACT

Journal of the Chemical Society, 1997

Transacetalization occurs extensively in gas phase ion-molecule reactions of 1,3-dioxane with a v... more Transacetalization occurs extensively in gas phase ion-molecule reactions of 1,3-dioxane with a variety of acylium ions [R᎐C ϩ ᎐ ᎐ O; R = CH 3 , C 2 H 5 , Ph, CH 3 O, Cl, CH 2 ᎐ ᎐ CH, (CH 3 ) 2 N] and a sulfur analogue, the thioacetyl ion CH 3 ᎐C ϩ ᎐ ᎐ S. Six-membered 1,3-dioxanylium ions and analogues, i.e. cyclic 'ionic (thio)ketals', are formed, as evidenced by pentaquadrupole triple-stage collision-dissociation mass spectra and MP2/6-311G(d,p)//6-311G(d,p) ϩ ZPE ab initio calculations, as well as by 18 O labelling experiments. Transacetalization with 1,3-dioxane is not a general reaction for sulfinyl cations (R᎐S ϩ ᎐ ᎐ O). They react either moderately (CH 3 ᎐S ϩ ᎐ ᎐ O) or extensively (CH 2 ᎐ ᎐ CH᎐S ϩ ᎐ ᎐ O) by transacetalization, form abundant intact adducts (Ph᎐S ϩ ᎐ ᎐ O) or undergo mainly proton transfer and/or hydride abstraction reactions (Cl᎐S ϩ ᎐ ᎐ O, CH 3 O᎐S ϩ ᎐ ᎐ O and C 2 H 5 O᎐S ϩ ᎐ ᎐ O). Competitive MS 2 experiments are employed to compare the transacetalization reactivity of different acylium ions, and that of two cyclic neutral acetals, that is 1,3dioxane and 1,3-dioxolane. All the cyclic 'ionic ketals' dissociate exclusively under low-energy collision conditions to regenerate the original reactant ion species, a simple dissociation chemistry that is amply demonstrated to be a very general characteristic of the transacetalization products. The cyclic 'ionic thioketal' formed in transacetalization with CH 3 ᎐C ϩ ᎐ ᎐ S is found, however, to dissociate exclusively to the oxygen analogue ion CH 3 ᎐C ϩ ᎐ ᎐ O, a triple-stage mass spectrometric (MS 3 ) experiment that constitutes a novel gas-phase strategy for conversion of thioacylium ions into acylium ions.

Journal of the American Society for Mass Spectrometry, Aug 1, 2000

Three gaseous acyclic distonic acylium ions: • CH 2 -CH 2 -C ϩ ¢O, • CH 2 -CH 2 -CH 2 -C ϩ ¢O, an... more Three gaseous acyclic distonic acylium ions: • CH 2 -CH 2 -C ϩ ¢O, • CH 2 -CH 2 -CH 2 -C ϩ ¢O, and • CH 2 ¢C(CH 2 )-C ϩ ¢O, are found to display dual free radical and acylium ion reactivity; with appropriate neutrals, they react selectively either as free radicals with inert charge sites, or (and more pronouncedly) as acylium ions with inert radical sites. The free radical reactivity of the ions is demonstrated via the Kentta ¨maa reaction: CH 3 S • abstraction with the spin trap dimethyl disulfide; their ion reactivity by two reactions most characteristic of acylium ions: transacetalization with 2-methyl-1,3-dioxolane and the gas-phase Meerwein reaction, that is, expansion of the three-membered epoxide ring of epichlorohydrin to the five-membered 1,3-dioxolanylium ion ring. In "one-pot" reactions with gaseous mixtures of epichlorohydrin and dimethyl disulfide, the ions react selectively at either site, but more readily at the acylium charge site, to form the two mono-derivatized ions. Further reaction at either the remaining free radical or acylium charge site forms a single bi-derivatized ion as the final product. Becke3LYP/6-31G(d) calculations predict the reactions at the acylium charge sites of the three distonic ions to be highly exothermic, and both the "hot" transacetalization and epoxide ring expansion products of • CH 2 -CH 2 -CH 2 -C ϩ ¢O to dissociate rapidly by H 2 C¢CH 2 loss in overall exothermic processes. The calculations also predict highly spatially separate odd spin and charge sites for the novel cyclic distonic ketal ions formed by the reactions at the acylium charge sites. (J Am Soc Mass Spectrom 2000, 11, 697-704) © 2000 American Society for Mass Spectrometry U nique electronic structures impart to distonic ions [1, 2] a potentially rich reactivity-they may react either as free radicals or as charged species, or more fascinating, as both. But this dual chemical behavior is rare [3]; distonic ions display most frequently reactivity that is characteristic of either their radical or ion nature . Recently [4], dual ion and free radical reactivity was reported for the distonic ions 1b and 1c. These isomeric and aromatic distonic acylium ions display -localized odd spin and -delocalized charge densities placed in orbitals lying in different symmetry planes ; hence, they can be regarded as distonic ions with "orbitalseparated" [4] radical and charge sites. Owing to this unique electronic structure, and their free radical and acylium charge sites, both chemically unsaturated and reactive, 1b and 1c react readily and selectively with appropriate neutrals either as free radicals with inert charge sites, or as acylium ions with inert radical sites. The distonic ions 1b and 1c display, therefore, in a single molecule, either free radical or acylium ion reactivity, or both.

Journal of the American Chemical Society, Jul 28, 2000

The gaseous and ionized prototype carbonyl ylide, the distonic ion + CH 2-O-CH 2 • , is found to ... more The gaseous and ionized prototype carbonyl ylide, the distonic ion + CH 2-O-CH 2 • , is found to transfer ionized methylene to 1-adamantylphosphaacetylene (1-Ad-CtP), a kinetically stabilized phosphaalkyne, thus forming the 1-adamantylphosphaacetylenium P-methylide ion, 1-Ad-C + dP-CH 2 • , a novel phosphorus, and the first nonclassical distonic ion. The ion abstracts CH 3 S • from CH 3 SSCH 3 and both Br • and C 3 H 5 • from allyl bromide, and this characteristic reactivity demonstrates its distonic character. MO calculations at the Becke3LYP/6-311G(d,p) and MCSCF [CAS(3,3)] levels confirm that 1-Ad-C + dP-CH 2 • bears spatially separated charge and odd spin sites. They also reveal for the ion a phosphaallylic radical structure that stabilizes the radical site, and a σ-bridged structure with three-center two-electron bonds that stabilizes the charge site. This unique electronic structure characterizes 1-Ad-C + dP-CH 2 • as the first nonclassical distonic ion.

Journal of the American Society for Mass Spectrometry, Feb 1, 2001

Journal of Organic Chemistry, 1996

Journal of Organic Chemistry, Jul 1, 1997

Transacetalization takes place in high yields in gas phase ion/molecule reactions of acylium ions... more Transacetalization takes place in high yields in gas phase ion/molecule reactions of acylium ions (RC + dO) with a variety of cyclic acetals and ketals, that is, five-, six-, and seven-membered 1,3-O,O-heterocycles and their mono-sulfur and nitrogen analogues. A general, structurally diagnostic method for the gas phase characterization of cyclic acetals and ketals is therefore available. Transacetalization occurs via initial O(or S)-acylation, followed by a ring-opening/ring-re-forming process in which a neutral carbonyl compound is eliminated and cyclic "ionic ketals" (that is, cyclic 1,3-dioxonium ions and analogues) are formed. The nature of the substituents at the 2-position, which are eliminated in the course of the reaction, is found to affect considerably the extent of transacetalization. Substituents not at the 2-position remain in the ionic products; hence positional isomers produce different cyclic "ionic ketals" and are easily differentiated. The triple-stage (MS 3 ) mass spectra of the cyclic "ionic ketals" show in all cases major dissociation to re-form the reactant acylium ion, a unique dissociation chemistry that is equivalent to the hydrolysis of neutral acetals and ketals and which is then determined to be a very general characteristic of cyclic "ionic ketals". Additionally, the 18 O-labeled transacetalization product of 1,3-dioxolane shows dissociation to both CH 3 C + d 18 O and CH 3 C + dO to the same extent, which confirms its cyclic "ionic ketal" structure and the "oxygen-scrambling" mechanism of transacetalization. Ab initio MP2/6-31G(d,p)//6-31G-(d,p) + ZPE energy surface diagrams show that transacetalization is the most exothermic, thermodynamically favorable process in reactions of CH 3 C + dO with 1,3-dioxolane and 1,3oxathiolane, whereas 1,3-dithiolane is unreactive due to the endothermicity of the initial acylation step.

Analyst, 2000

A new method is described for the rapid, sensitive, virtually interference-free, and selective qu... more A new method is described for the rapid, sensitive, virtually interference-free, and selective quantitation of cyanogenic glycosides in aqueous extracts using membrane introduction mass spectrometry (MIMS). Selective monitoring, by either conventional MIMS or cryotrap-MIMS, not of HCN but of the co-released ketones (acetone and butan-2-one), when performed for both the crude cassava extracts and the linamarase-NaOH-hydrolyzed extracts, is found to offer an advantageous alternative to classic spectrophotometric methods based on HCN analysis for the selective quantitation of the two cyanogenic glycosides linamarin and lotaustralin expressed as both the free HCN content and the total cyanogenic potential (total HCN).

Electron ionization mass spectra of bis-1,2,4-oxadiazoles: tandem mass spectrometry and accurate mass measurements

Rapid Communications in Mass Spectrometry, 2001

Polyhedron, Aug 1, 2008

The novel asymmetric metallo-organic triads cis-and trans-[B(4-py)BPFPH 2 {Ru 3 O(Ac) 6 (py) 2 }{... more The novel asymmetric metallo-organic triads cis-and trans-[B(4-py)BPFPH 2 {Ru 3 O(Ac) 6 (py) 2 }{Ru-(bpy) 2 Cl}](PF 6) 2 (5a,b) for which cis-and trans-B(4-py)BPFPH 2 = 5,10-bis(pentafluorophenyl)-15,20bis(4-pyridyl)porphyrin and 5,15-bis(pentafluorophenyl)-10,20-bis(4-pyridyl)porphyrin, respectively; Ac = acetate; py = pyridine and bpy = 2,2 0-bipyridine, as well as their corresponding monosubstituted dyads cis-and trans-[B(4-py)BPFPH 2 {Ru 3 O(Ac) 6 (py) 2 }]PF 6 (4a,b) have been structurally characterized via electrospray ionization mass spectrometry (ESI-MS and ESI-MS/MS). The ESI-MS of dyads 4a,b display two characteristic Ru-multicomponent clusters of isotopologue ions corresponding to singly charged ions 4a,b + of m/z 1629 and doubly charged ions [4a,b+H] 2+ of m/z 815 and the triads 5a,b are detected by ESI-MS as the intact doubly charged cluster of isotopologue ions of m/z 1039 [5a,b] 2+. The ESI-MS/MS of 4a,b + , [4a,b+H] 2+ and [5a,b] 2+ reveal characteristic dissociation pathways, which confirm the structural assignments providing additional information on the intrinsic binding strengths of the gaseous ions. Although the gas-phase behavior of each pair of isomers was rather similar, the less symmetric dyads 4a,b are distinguished via the 1 H NMR spectral profile of the pyrrolic signals. Exploratory photophysical assays have shown that both modifying motifs alter the porphyrinic core emission profile, opening the possibility to use these asymmetric systems as photophysical devices.

Analyst, Jun 26, 2002

Direct sampling tandem mass spectrometry (MS/MS) was used for the quantitation of mixtures of the... more Direct sampling tandem mass spectrometry (MS/MS) was used for the quantitation of mixtures of the isomers 2-, 3-and 4-ethyl pyridine. The similarity between the analytes and the second-order nature of MS/MS data require the use of multivariate calibration techniques capable of handling multiway data. Multilinear PLS (N-PLS) was applied here, as well as the alternative technique of unfolding the data and using standard two-way PLS. Particular attention was paid to the optimal type of spectral preprocessing. Due to the presence of heteroscedastic noise the logarithmic transform of the spectra prior to calibration gives the best results. Predictions errors of the order of 10-15% were obtained, which compare well with other results found in the literature.

The Gas-Phase Meerwein Reaction

Chemistry: A European Journal, Mar 3, 2000

A systematic investigation of a novel epoxide and thioepoxide ring expansion reaction promoted by... more A systematic investigation of a novel epoxide and thioepoxide ring expansion reaction promoted by gaseous acylium and thioacylium ions is reported. As ab initio calculations predict, and 18O-labeling and MS3 pentaquadrupole experiments demonstrate, the reaction proceeds by initial O(S)-acylation of the (thio)epoxides followed by rapid intramolecular nucleophilic attack that results in three-to-five-membered ring expansion, and forms cyclic 1,3-dioxolanylium, 1,3-oxathiolanylium, or 1,3-dithiolanylium ions. This gas-phase reaction is analogous to a condensed-phase reaction long since described by H. Meerwein (Chem. Ber. 1955, 67, 374), and is termed as "the gas-phase Meerwein reaction"; it occurs often to great extents or even exclusively, but in some cases, particularly for the most basic (thio)epoxides and the most acidic (thio)acylium ions, proton transfer (eventually hydride abstraction) competes efficiently, or even dominates. When (thio)epoxides react with (thio)-acylium ions, the reaction promotes O(S)-scrambling; when epoxides react with thioacylium ions and the adducts are dissociated, it promotes S/O replacement. An analogous four-to-six-membered ring expansion also occurs predominantly in reactions of trimethylene oxide with acylium and thioacylium ions.

Microbiology, 2016

Production of pigments by filamentous fungi is gaining interest owing to their use as food colour... more Production of pigments by filamentous fungi is gaining interest owing to their use as food colourants, in cosmetics and textiles, and because of the important biological activities of these compounds. In this context, the objectives of this study were to select pigment-producing fungi, identify these fungi based on internal transcribed spacer sequences, evaluate the growth and pigment production of the selected strains on four different media, and characterize the major coloured metabolites in their extracts. Of the selected fungal strains, eight were identified as Aspergillus sydowii (CML2967), Aspergillus aureolatus (CML2964), Aspergillus keveii (CML2968), Penicillium flavigenum (CML2965), Penicillium chermesinum (CML2966), Epicoccum nigrum (CML2971), Lecanicillium aphanocladii (CML2970) and Fusarium sp. (CML2969). Fungal pigment production was influenced by medium composition. Complex media, such as potato dextrose and malt extract, favoured increased pigment production. The coloured compounds oosporein, orevactaene and dihydrotrichodimerol were identified in extracts of L. aphanocladii (CML2970), E. nigrum (CML2971), and P. flavigenum (CML2965), respectively. These results indicate that the selected fungal strains can serve as novel sources of pigments that have important industrial applications.

Applied microbiology and biotechnology, Jan 22, 2015

Xyloglucan-specific endo-β-1,4-glucanases (Xegs, EC 3.2.1.151) exhibit high catalytic specificity... more Xyloglucan-specific endo-β-1,4-glucanases (Xegs, EC 3.2.1.151) exhibit high catalytic specificity for β-1,4 linkages of xyloglucan, a branched hemicellulosic polysaccharide abundant in dicot primary cell walls and present in many monocot species. In nature, GH12 Xegs are not associated with carbohydrate-binding modules (CBMs), and here, we have investigated the effect of the fusion of the xyloglucan-specific CBM44 on the structure and function of a GH12 Xeg from Aspergillus niveus (XegA). This fusion presented enhanced catalytic properties and conferred superior thermal stability on the XegA. An increased k cat (chimera, 177.03 s(-1); XegA, 144.31 s(-1)) and reduced KM (chimera, 1.30 mg mL(-1); XegA, 1.50 mg mL(-1)) resulted in a 1.3-fold increase in catalytic efficiency of the chimera over the parental XegA. Although both parental and chimeric enzymes presented catalytic optima at pH 5.5 and 60 °C, the thermostabilitiy of the chimera at 60 °C was greater than the parental XegA. Mor...

RSC advances, 2024

Inflammation plays a crucial role in COVID-19, and when it becomes dysregulated, it can lead to s... more Inflammation plays a crucial role in COVID-19, and when it becomes dysregulated, it can lead to severe outcomes, including death. Naphthoquinones, a class of cyclic organic compounds widely distributed in nature, have attracted significant interest due to their potential biological benefits. One such naphthoquinone is 3,5,8-trihydroxy-6-methoxy-2-(5-oxohexa-1,3-dienyl)-naphthanthene-1,4-dione (3,5,8-TMON), a compound produced by fungi. Despite its structural similarity to shikonin, limited research has been conducted to investigate its biological properties. Therefore, the objective of this study was to evaluate the effects of 3,5,8-TMON and its synthetic derivatives in the context of inflammation induced by lipopolysaccharide (LPS) and SARS-CoV-2 infection in vitro using cell cultures. 3,5,8-TMON was obtained by acid treatment of crude extracts of fermentation medium from Cordyceps sp., and two derivatives were accessed by reaction with phenylhydrazine under different conditions. The results revealed that the crude extract of the fungi (C. Ex) inhibited the activity of transcription factor NF-kB, as well as the production of nitric oxide (NO) and interleukin-6 (IL-6) when LPS induced it in RAW 264.7 cells. This inhibitory effect was observed at effective concentrations of 12.5 and 3.12 mg mL −1. In parallel, 3,5,8-TMON and the new derivatives 3 and 4 demonstrated the ability to decrease IL-6 production while increasing TNF, with a specific effect depending on the concentration. These concentration-dependent agonist and antagonist effects were observed in THP-1 cells. Furthermore, 3,5,8-TMON inhibited IL-6 production at concentrations of 12.5 and 3.12 mg mL −1 in Calu-3 cells during SARS-CoV-2 viral infection. These findings present promising opportunities for further research into the therapeutic potential of this class of naphthoquinone in the management of inflammation and viral infections.