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We report a spectroscopic study of the network of reactions of a flavylium dye encapsulated in the one-dimensional channels of zeolite L. The positively charged 7,4'-dihydroxyflavylium ((+)) is easily incorporated and remains stable in zeolite L channels. Once encapsulated, the flavylium exhibits a red shift in the excitation spectrum comparative to aqueous solutions. Moreover, contrary to the observed behavior in water, no excited state proton transfer takes place in the loaded crystals, corroborating the encapsulation of (+). The trans-chalcone () form from the same flavylium network could also be encapsulated inside the zeolite L, using toluene with 20% triethylamine as solvent and K(+) as counter ion of the negative framework of the zeolite. The encapsulation of is confirmed by changes on the excitation spectrum and by a blue shift in the emission. The encapsulated was shown to generate (+) when the -loaded crystals were suspended in water, which proves that isomerization, tautomerization and dehydration reactions take place inside the zeolite L.

The purpose of this retrospective study was to determine the prevalence of hypodontia and associated dental anomalies in patients undergoing orthodontic treatment in Brasília, Brazil, over a 2 year period (1998-2000). The records of 1049 orthodontic patients between 10 and 15.7 years of age (507 males and 542 females) from 16 orthodontic clinics were analysed. Descriptive statistics were performed for the study variables. A chi-square test was used to determine the difference in the prevalence of hypodontia between genders. The prevalence of hypodontia was 6.3 per cent (39.4 per cent males and 60.6 per cent females) with no statistically significant difference between the genders. One case of oligodontia was observed. The maxillary lateral incisor was the most frequently missing tooth, followed by the mandibular second premolar. All cases of hypodontia, except one, were associated with at least one other dental anomaly. These associated dental anomalies were retained primary teeth (30.3 per cent), ectopic canine eruption (25.8 per cent), taurodontism (21.2 per cent), and peg-shaped maxillary lateral incisors (16.7 per cent).

The photochromism of the compound 4'-N,N-dimethylamino-7-hydroxyflavylium incorporated in Pluronic F127 micelles and gels was studied in great detail. The red flavylium ion (AH(+)) or the quinoidal base (A), depending on pH, are the irradiation products of the colorless trans-chalcone (Ct). Absorption and fluorescence (steady-state, time-resolved, and anisotropy), pH jumps, and flash photolysis were used to characterize the system. At moderately acidic to neutral pH values, the Ct species is distributed between the core and corona of the Pluronic micelle, as well as in the aqueous phase. At acidic pH values, AH(+) remains most probably in the water phase. The Ct maximum absorption wavelength constitutes a good sensor for the critical micelle concentration (CMC) or critical micelle temperature (CMT). The apparent acidity constant pK'(a) was found to be a relatively good sensor for CMC and also for detection of the sol-gel critical temperature. The Ct photochromic mechanism was analyzed by comparing the photophysics in pure solvents and the pluronic media. Solvatochromic effects show a lack of solvent polarity dependence of the Stokes shift, indicating a low dipolar moment change between the ground and the locally excited state. An internal charge transfer nonradiative process (ICT) competes with Ct photoisomerization and is the dominant process in highly polar solvents, preventing the appearance of photochromism, in contrast with lower polar environments, such as micelles and ethanol. In high viscous environments as those found in the core of the Pluronic F127 micelles or glycerol, both ICT and photoisomerization are reduced, enhancing the Ct fluorescence quantum yield. According to the data from fluorescence measurements and pH jumps, evidence for the Ct distribution among different sites within the pluronic aggregate was found, (i) a hydrophilic/fluid region where Ct has poor fluorescence and isomerization yields, bulk region; (ii) the corona of the micelle where photoisomerization is maximized; and (iii) the hydrophobic/viscous region where the fluorescence quantum yield is higher (and photoisomerization lower). This effect leads to a selective Ct photochemistry.

Flavylium salts contain the basic structure and show a pH-dependent sequence of reactions identical to natural anthocyanins, which are responsible for most of the red and blue colors of flowers and fruits. In this work we investigated the effect of the water-soluble molecular clips C1 and C2 substituted by hydrogen phosphate or sulfate groups on the stability and reactions of the flavylium salts 1-4 by the use of UV-vis absorption, fluorescence, and NMR spectroscopy as well as of the time-resolved pH jump and flash photolysis methods. Clip C1 forms highly stable host-guest complexes with the flavylium salts 1 and 2 and the quinoidal base 3A in methanol. The binding constants were determined by fluorometric titration to be log K = 4.1, 4.7, and 5.6, respectively. Large complexation-induced (1)H NMR shifts of guest signals, Delta delta(max), indicate that in the case of the flavylium salts 1 and 2 the pyrylium ring and in the case of the quinoidal base 3A the o-hydroxyquinone ring are preferentially bound inside the clip cavity. Due to the poor solubility of these host-guest complexes in water, the association constants could be only determined in highly diluted aqueous solution by UV-vis titration experiments for the complex formation of clip C1 with the flavylium salt 3AH(+) at pH = 2 and the quinoidal base 3A at pH = 5.3 to be log K = 4.9 for both complexes. Similar results were obtained for the formation of the complexes of the sulfate-substituted clip C2 with flavylium salt 4AH(+) and its quinoidal base 4A which are slightly better soluble in water (log K = 4.3 and 4.0, respectively). According to the kinetic analysis (performed by using the methods mentioned above) the thermally induced trans-cis chalcone isomerization (4Ct --> 4Cc) and the H(2)O addition to flavylium cation 4AH(+) followed by H(+) elimination leading to hemiketal 4B are both retarded in the presence of clip C2, whereas the photochemically induced trans-cis isomerization (4Ct --> 4Cc) is not affected by clip C2. The results presented here are explained with dominating hydrophobic interactions between the molecular clips and the flavylium guest molecules. The other potential interactions (ion-ion, cation-pi, pi-pi, and CH-pi), which certainly determine the structures of these host-guest complexes to a large extent, seem to be of minor importance for their stability.

The objectives of this study were to evaluate anti-retroviral (ARV) prescription pickups during twelve months following the first prescription and to identify factors associated with irregular pickups or permanent dropout in two public HIV/AIDS referral centers in Belo Horizonte, Minas Gerais State, Brazil. Participants (n = 323) were antiretroviral naïve and were recruited from May 2001 to May 2002. A total of 98 (30.3%) patients abandoned treatment, and 187 (57.9%) had at least one irregular pickup. Patients with irregular pickups and dropouts were compared to those with regular pickups. Multinomial multivariate analysis showed that living outside Belo Horizonte, CD4+ T-lymphocyte count greater than 200/mm(3), and antiretroviral regimen without protease inhibitors were associated with irregular pickups. In addition to these variables, not being on other medications, and any non-adherence recorded on patient charts were associated with treatment dropout. Pharmacy records are important potential indicators of non-adherence and should be incorporated as such in clinical practice. Strategies should be prioritized to reach out to dropouts or patients with irregular ARV pickups.

2-Styryl-1-benzopyrylium derivatives exhibit deeper hues and absorption spectra that are substantially red-shifted when compared with their 2-phenyl-1-benzopyrylium analogues. They follow the same pH and light-dependent network of chemical reactions previously described for 2-phenyl-1-benzopyrylium compounds. In this work, the photochromic properties of 7-hydroxy-2-(4-hydroxystyryl)-1-benzopyrylium chloride are reported. This compound was fully characterized by UV-vis absorption, fluorescence emission, pH jumps, and flash photolysis, and its properties were compared with the analogue 7,4'-dihydroxyflavylium (7-hydroxy-2-(4-hydroxyphenyl)-1-benzopyrylium). The trans-chalcones of both compounds lacking the hydroxyl in position 2 were synthesized and used as model compounds since they exhibit cis-trans isomerization but cannot be involved in the other processes resulting from the ring closure. The transient absorption of two triplets attributed to the chalcones Ct/Ct(-), and a tautomer was detected by nanosecond flash photolysis, independent of the existence of the 2-hydroxyl substituent. The experimental results are compatible with the main formation of cis-chalcone from the singlet state. In the case of the styryl derivatives, the fraction of triplet formed from excitation of Ct is much higher, and the fraction of isomerization is much smaller. For this reason, the photochemistry of 7-hydroxy-2-(4-hydroxystyryl)-1-benzopyrylium in water is much less efficient than that of its parent 7,4'-dihydroxyflavylium; however, in the presence of CTAB micelles, intense red colors can be obtained upon irradiation, confirming the usefulness of this family of compounds as photochromic systems.

A strategy to obtain photochromism from the network of chemical reactions originated by flavylium compounds in solution is described. This strategy is particularly useful for flavylium salts bearing amino groups which give rise to a variety of beautiful colors but lack photochemistry in water. The trans-chalcone of 7-(N,N-diethylamino)-4'-hydroxyflavylium interacts strongly with CTAB micelles defining a yellow dark state. Upon irradiation, the system switches to a pink-red state emerging from the flavylium cation that is formed inside the micelle and ejected to the bulk aqueous phase. The photochemical product reverts back to the trans-chalcone adduct with the micelle in the dark. The thermodynamics as well as the kinetics of the photochromic system were studied in detail. The best color contrast is obtained at pH = 4.25 with Phi = 0.001 and a recovery lifetime of approximately 3 h. This photochromic system works with no need of changing the pH, which constitutes an important improvement over previously described systems dependent on pH jumps.

Differently from water, efficient photochromism with a strong colour contrast has been observed for the multistate compound 7,4'-dihydroxyflavylium in the presence of cetyl trimethylammonium bromide (CTAB) micelles. Two states are responsible for the photochromism: trans-chalcone (inside the micelle) in the dark, and flavylium cation, AH(+), (in bulk water) upon irradiation. The kinetics of the system was characterized by flash photolysis and pH jumps. Evidence that the photochemical process leading to AH(+) occurs in the micelle was achieved. The best colour contrast is obtained at pH = 1.5, from a solution practically colourless in the dark, to an intense yellow upon irradiation (quantum yield 0.4). The system is completely reversible with a lifetime of 38 min at room temperature, and exhibits a reasonable stability. A kinetic model capable of fitting the data from thermal entrance of the compound into the micelle, its ejection to bulk water upon irradiation and quantum yields of the photochemical process is proposed.

The chemistry and photochemistry of the compound 4'-iodo-8-methoxyflavylium tetrafluoroborate was studied in solvent mixtures of water and ethanol. The trans-chalcone form (Ct) is always the most stable species at equilibrium. In particular, for the first time, Ct and not the flavylium cation is reported as the most stable species in mixtures containing water at pH 1.0. The rate of Ct formation as a function of the water content exhibits a bell-shaped dependence, showing a maximum at approximately 50 % water. These trends are explained by a slower cis-trans isomerization in ethanol relative to that in water due to the expected stabilization in polar solvents of the zwitterionic intermediate; on the other hand, the decrease in the concentration of cis-chalcone (Cc) in the pseudoequilibrium with increasing water content, gives rise to a decrease in the rate of Ct formation (k(obs)=k(real)[Cc]). The hydration reaction was found to be much more efficient when water is present in low concentrations. This result has important consequences for the interpretation of the coloring phenomena caused by anthocyanins in plants, as well as for applications of flavylium compounds in the field of optical memories.

Neuroprotective actions of scatter factor/hepatocyte growth factor (SF/HGF) have not been described. We examined the effects of SF/HGF in comparison to acidic fibroblast growth factor-1 (FGF-1) on N-methyl-D-aspartate (NMDA) and quinolinic acid (QUIN)-induced excitotoxicity in primary cerebellar granule neurons. Exposure to NMDA or QUIN for 24 h resulted in concentration-dependent cell death (p < 0.001) that was completely attenuated (p < 0.001) by pre-treatment of cells with SF/HGF (50 ng/mL) or FGF-1 (40 ng/mL). SF/ HGF and FGF-1 activated both Akt and MAP-kinase > threefold (p < 0.001). Neither SF/HGF nor FGF-1 activated cyclic AMP-response element binding protein (CREB), a downstream target of MAP-kinase, whereas brain-derived neurotrophic factor (BDNF) activated both MAP-kinase and CREB in granule neurons. Neuroprotection against NMDA or QUIN by SF/HGF and FGF-1 was negated by the addition of LY294002 (10 microM) or wortmannin (100 microM), two distinct inhibitors of phosphatidylinositol 3-kinase (P13-K), but not by the MAP-kinase kinase (MEK) inhibitor PD98059 (33 microm). Likewise, expression of a dominant-negative mutant of Akt (Akt-kd) completely prevented the neuroprotective actions of SF/HGF and FGF-1. Overexpression of a constitutively activated Akt (Akt-myr) or wild-type Akt (wtAkt) attenuated excitotoxic cell death. These data show that both SF/HGF and FGF-1 protect cerebellar granule neurons against excitotoxicity with similar potency in a P13-K/Akt-dependent and MAP-kinase/CREB-independent manner.

Normal gastric mucosa expresses MUC1 and MUC5AC in foveolar epithelium and MUC6 in mucous neck cells of the body and deep glands of the antrum. Several studies have reported aberrant expression of an under-glycosylated form of MUC1, decreased expression of "gastric" mucins and aberrant expression of "non-gastric" mucins in gastric carcinoma. In this study, we analysed the expression profile of mucins MUC1, MUC2, MUC5AC and MUC6 in 94 gastric carcinomas using immunohistochemistry. Our results showed that: (1) mucin expression is associated with tumour type (MUC5AC with diffuse and infiltrative carcinomas and MUC2 with mucinous carcinomas) but not with the clinico-biological behaviour of the tumours; and (2) mucin expression is associated with tumour location (MUC5AC with antrum carcinomas and MUC2 with cardia carcinomas), indirectly reflecting differences in tumour differentiation according to tumour location.