Carlos Eduardo Carvalho

Fluorescent symmetric phenazines from naphthoquinones: 3. Steady-state spectroscopy and solvent effect of seven phenazine derivatives: structure–photophysics correlations

Abstract The fluorescence spectra of seven phenazines (two belonging to the C2h point group, two to the C2v point group, two to the Cs point group and one to the C1 point group) in organic solvents of varying polarity show a bathochromic shift in all cases. Fluorescence quantum yields increase as the polarity of the solvent increases for the C2h and the Cs compounds, however, no appreciable changes are noted in the C2v compounds. The unexpectedly strong solvent interactions with the two centrosymmetric phenazines are explained on the basis of a localized excited state. This explanation was supported by excited state dipole moment measurements, which indicated similar moments for the C2h and C2v compounds. Two of the compounds undergo lasing when placed in a laser cavity and pumped with the third harmonic of an Nd-YAG laser.

Excited state acidity of bifunctional compounds. 6. A novel, high fluorescence quantum yield, excited state intramolecular proton transfer compound: 2-hydroxyphenyl-lapazole in non-protic solvents

The synthesis of 2-hydroxyphenyl-lapazole (HPL) is reported for the first time. HPL in the first excited singlet state undergoes excited state intramolecular proton transfer (ESIPT) in cyclohexane, with an overall fluorescence quantum yield of 0.15. This is an order of magnitude greater than that observed for 2-hydroxyphenyl-benzoxazole (HBO), which has been extensively studied and has a similar structure. At room temperature in non-protic solvents, ESIPT in HPL attains equilibrium, whose constant (between normal and tautomer species) is approximately 1.4. These observations suggest that HPL (and its derivatives) is well worth investigating because it is easier to study (and may work more efficiently as a laser dye) than HBO.

Singlet oxygen production by pyrano and furano 1,4-naphthoquinones in non-aqueous medium.

The influence of ring size on the photobehaviour of condensed 1,4-naphthoquinone systems, such as pyrano- and furano-derivatives (1 and 2, respectively) has been investigated. The absorption spectra for both families of naphthoquinones reveal clear differences; in the case of 2 they extend to longer wavelengths. A solvatochromic red shift in polar solvents is consistent with the π,π* character of the S(0)→ S(1) electronic transition in all cases. Theoretical (B3LYP) analysis of the HOMO and LUMO Kohn-Sham molecular orbitals of the S(0) state indicates that they are π and π* in nature, consistent with the experimental observation. A systematic study on the efficiency of singlet oxygen generation by these 1,4-naphthoquinones is presented, and values larger than 0.7 were found in every case. In accordance with these results, laser flash photolysis of deoxygenated acetonitrile solutions led to the formation of detectable triplet transient species with absorptions at 390 and 450 nm (1) and at 370 nm (2), with φ(ISC) close to 1. Additionally, the calculated energies for the T(1) states relative to the S(0) states at UB3LYP/6-311++G** are ca. 47 kcal mol(-1) for 1 and 43 kcal mol(-1) for 2. A comparison of the geometrical parameters for the S(0) and T(1) states reveals a marked difference with respect to the arrangement of the exocyclic phenyl ring whilst a comparison of electronic parameters revealed the change from a quinone structure to a di-dehydroquinone diradical structure.

Excited state acidity of bifunctional compounds

2-Hydroxyphenyl-lapazole (HPL) is shown to undergo excited state intramolecular proton transfer (ESIPT) in the protic solvents methanol, propan-2-ol and octan-1-ol at room temperature. Investigation of the kinetics of this process, using time-resolved single photon counting and transient absorption spectroscopy, indicates the presence of three different excited-state species. These results are very different from that already reported for HPL in non-protic solvents, where it was found that the ESIPT process attains equilibrium during the lifetime of the excited state. Factor analysis of the steady state spectra supports the conclusions drawn from the kinetic results. The difference in behavior as a function of solvent is attributed to two factors that depend on the stronger solute–solvent interactions in the case of the protic solvents. (1) The slight slowing down of the process of proton transfer, which prevents equilibrium from being established during the lifetime of the excited singlet state. (2) The weakening of the intramolecular hydrogen bond, which allows rotation of the hydroxyphenyl moiety.

Excited-state acidity of bifunctional compounds

Fluorescence emission and excitation spectra and experimental dipole moments are presented for 5-(2-hydroxyphenyl)-3-phenyl-1,2,4-oxadiazole and 3-(2-hydroxyphenyl)-5-phenyl-1,2,4-oxadiazole. These data indicate that the long-wavelength emission of the former, in non-hydrogen bonding solvents, is due to a tautomeric PT structure. The latter exhibits only the ‘normal’ band. The striking difference in behavior between these two compounds of very similar structure is explained on the basis of coplanarity between the aryl ring in position 5 and the heterocycle ring, the aryl ring in the 3 position not being in the same plane.

2-(4-Methyl­phen­yl)-1H-anthraceno[1,2-d]imidazole-6,11-dione: a fluorescent chemosensor

In the title compound, C22H14N2O2, the five rings of the molecule are not coplanar. There is a significant twist between the four fused rings, which have a slightly arched conformation, and the pendant aromatic ring, as seen in the dihedral angle of 13.16 (8)° between the anthraquinonic ring system and the pendant aromatic ring plane.

Fluorescent Symmetric Phenazines from the Reactions of β-Lapachone and Nor-β-lapachone with Ammoniating Agents

The reactions of β-lapachone 1 and nor-β-lapachone 4 with several ammoniating agents give rise to symmetric phenazines which exhibit high, solvent dependent, fluorescence quantum yields.

Considerations about gastric cancer proteomics.

The frequency of molecular studies aimed to analyze promoter methylation of tumor suppressor genes and global proteomics in gastric carcinogenesis is increasing. Nonetheless, only a few considered the different types of stomach cells, the tumor location and the influence of Helicobacter pylori and Epstein Barr virus infection (EBV). Molecular differences relating to anatomical and histological tumor areas were also recently described. The authors propose a molecular classification of gastric cancer, dividing it into four subtypes: tumors positive for EBV; microsatellite unstable tumors; genomically stable tumors and tumors with chromosomal instability. RESUMO A frequência de estudos moleculares visando a analisar os promotores de metilação de genes supressores de tumor e proteômica globais na carcinogênese gástrica está aumentando. No entanto, apenas alguns consideraram os diferentes tipos de células do estômago, a localização do tumor e a influência da infecção por Helicobacter pylori e pelo vírus Epstein-Barr (EBV). Diferenças moleculares relacionadas com áreas tumorais anatômicas e histológicas também foram recentemente descritas. Os autores propõem uma classificação molecular de câncer gástrico, dividindo-o em quatro subtipos: tumores positivos para o EBV; tumores microssatélite instáveis; tumores genomicamente estáveis ​​e tumores com instabilidade cromossômica.

JC and BK virus DNA detection in archival slides of urine cytospin from renal transplant patients

Although identifying cytological viral inclusions (decoy cells) in the urine is relatively easy, distinguishing between Polyomaviruses BKV and JCV is not possible. Few studies have been published regarding JCV detection in kidney transplant recipients.

Comparing intestinal versus diffuse gastric cancer using a PEFF-oriented proteomic pipeline

Gastric cancer is the fifth most common malignant neoplasia and the third leading cause of cancer death worldwide. Mac-Cormick et al. recently showed the importance of considering the anatomical region of the tumor in proteomic gastric cancer studies; more differences were found between distinct anatomical regions than when comparing healthy versus diseased tissue. Thus, failing to consider the anatomical region could lead to differential proteins that are not disease specific. With this as motivation, we compared the proteomic profiles of intestinal and diffuse adenocarcinoma from the same anatomical region, the corpus. To achieve this, we used isobaric labeling (iTRAQ) of peptides, a 10-step HILIC fractionation, and reversed-phase nano-chromatography coupled online with a Q-Exactive Plus mass spectrometer. We updated PatternLab to take advantage of the new Comet-PEFF search engine that enables identifying post-translational modifications and mutations included in neXtProts PSI Extended FASTA Format (PEFF) metadata. Our pipeline then uses a text-mining tool that automatically extracts PubMed IDs from the proteomic result metadata and drills down keywords from manuscripts related with the biological processes at hand. Our results disclose important proteins such as apolipoprotein B-100, S100 and 14-3-3 proteins, among many others, highlighting the different pathways enriched by each cancer type. SIGNIFICANCE Gastric cancer is a heterogeneous and multifactorial disease responsible for a significant number of deaths every year. Despite the constant improvement of surgical techniques and multimodal treatments, survival rates are low, mostly due to limited diagnostic techniques and late symptoms. Intestinal and diffuse types of gastric cancer have distinct clinical and pathological characteristics; yet little is known about the molecular mechanisms regulating these two types of gastric tumors. Here we compared the proteomic profile of diffuse and intestinal types of gastric cancer from the same anatomical location, the corpus, from four male patients. This methodological design aimed to eliminate proteomic variations resulting from comparison of tumors from distinct anatomical regions. Our PEFF-tailored proteomic pipeline significantly increased the identifications as when compared to previous versions of PatternLab.