Theoretical Study of the Thermolysis Reaction and Chemiexcitation of Coelenterazine Dioxetanes

Coelenterazine and other imidazopyrazinones are important bioluminescent substrates widespread in marine species and can be found in eight phyla of luminescent organisms. Light emission from these systems is caused by the formation and subsequent thermolysis of a dioxetanone intermediate, whose decomposition allows for efficient chemiexcitation to singlet excited states. Interestingly, some studies have also reported the involvement of unexpected dioxetane intermediates in the chemiand bioluminescent reactions of Coelenterazine, albeit with little information on the underlying mechanisms of these new species. Herein, we have employed a theoretical approach based on density functional theory to study for the first time the thermolysis reaction and chemiexcitation profile of two Coelenterazine dioxetanes. We have found that the thermolysis reactions of these species are feasible but with relevant energetic differences. More importantly, we found that the singlet chemiexcitation profiles of these dioxetanes are significantly less efficient than the corresponding dioxetanones. Furthermore, we identified triplet chemiexcitation pathways for the Coelenterazine dioxetanes. Given this, the chemiexcitation of these dioxetanes should lead only to minimal luminescence. Thus, our theoretical investigation of these systems indicates that the thermolysis of these dioxetanes should only provide dark pathways for the formation of nonluminescent degradation products of the chemi- and bioluminescent reactions of Coelenterazine and other imidazopyrazinones

Some results involving the AαA_\alpha-eigenvalues for graphs and line graphs

Let $G$ be a simple graph with adjacency matrix $A(G)$, signless Laplacian matrix $Q(G)$, degree diagonal matrix $D(G)$ and let $l(G)$ be the line graph of $G$. In 2017, Nikiforov defined the $A_\alpha$-matrix of $G$, $A_\alpha(G)$, as a linear convex combination of $A(G)$ and $D(G)$, the following way, $A_\alpha(G):=\alpha A(G)+(1-\alpha)D(G),$ where $\alpha\in[0,1]$. In this paper, we present some bounds for the eigenvalues of $A_\alpha(G)$ and for the largest and smallest eigenvalues of $A_\alpha(l(G))$. Extremal graphs attaining some of these bounds are characterized.Comment: 18 pages, 5 figures, 3 table

Neurospora crassa mat A-2 and mat A-3 proteins weakly interact in the yeast two-hybrid system and affect yeast growth

Mating-type genes control the entry into the sexual cycle, mating identity and sexual development in fungi. The mat A-2 and mat A-3 genes, present in the mat A idiomorph of the filamentous fungus Neurospora crassa, are required for post-fertilization functions but are not essential for mating identity. Their putative roles as transcription factors are based on the similarity of mat A-2 with the Podospora anserina SMR1 gene and an HMG motif present in the mat A-3 gene. In this work the yeast two-hybrid system was used to identify transcriptional activity and protein-protein interaction of N. crassamat A-2 and mat A-3 genes. We observed that the mat A-3 protein alone is capable of weakly activating transcription of yeast reporter genes; it also binds with low specificity to the GAL1 promoter sequence, possibly due to its HMG domain. Our results also indicate that mat A-3 is capable to form homodimers, and interact with mat A-2. Interference on yeast growth was observed on some transformants suggesting a toxic action of the mat A-2 protein. Our data on pattern of interactions of mat proteins contributes towards understanding the control of vegetative and sexual cycles in filamentous fungi

Taxas de mortalidade entre os idosos de Belo Horizonte, 1996 e 2006: uma breve análise por sexo e principais causas de morte

In Brazil and all over the world, in parallel with the demographic transition, due to advances in medicine and health care, there has been an increase in the life expectancy and longevity of the elderly. This combination of factors causes changes in the pattern of morbidity and mortality which can be assessed by simple measures of both morbidity and mortality. In this study we used indicators of mortality (General mortality rates for the elderly and rates by age groups) for the elderly popula tion 65 years and more Belo Horizonte in 1996 and 2006. The main results are that (1) there is a trend of decrease of mortality rates of the elderly among the younger men and women for the most represented causes of death, (2) most often causes of death changed during the period, (3) differences could be observed for males and for females. Finally, it is important to emphasize that it is worrysome that ill defined causes of death were among the most common causes for men and women.Brazil, mortality

CHEMICAL CHARACTERIZATION AND ANTIMICROBIAL ACTIVITY OF HYDROETHANOLIC CRUDE EXTRACT OF EUGENIA FLORIDA DC (MYRTACEAE) LEAVES

Objective: The present study aimed to characterize and quantify the total phenolics, flavonoids and tannins in a hydroethanolic crude extract (70% (v/v) (EB)) of the leaves of E. florida DC, as well as to evaluate the antimicrobial activity of the extract against different species of micro-organisms.Methods: EB was characterized using a mass spectrometer equipped with a direct insertion device for in-stream injection (FIA). Quantitative analyses of major compounds were carried out by spectrophotometry. In addition, we evaluated the sensitivity profiles of different strains of yeast and bacteria against different concentrations of EB.Results: The classes found were in agreement with those described in the literature: flavonoids, tannins, phenolic acids and saponins. EB showed levels of phenolic compounds, flavonoids and tannins equal to 25.82 mg gallic acid equivalents per gram of extract (EAG/g), 8.42 mg quercetin equivalents per gram of extract (EQ/g) and 7.30 mg tannic acid equivalents per gram of extract (AT/g), respectively. In the analysis of antimicrobial activity, EB was more active against yeasts but was not effective against the bacteria used in the test.Conclusion: We can conclude that E. florida DC has antimicrobial potential, due to the presence of bioactive secondary metabolites.Keywords: Phenolics, Micro-organisms, Mass spectrometer, Yeasts, Bacteria, PotentialÂ

Functionalization of gauzes with liposomes entrapping an anti-inflammatory drug: a strategy to improve wound healing

From ancientness, suitable materials have been developed to cover the wounds in order to prevent infections and promote proper wound healing. In this study, the successful development of functionalized nonwoven gauzes with liposomes entrapping anti-inflammatory piroxicam is reported. Piroxicam is a non-steroidal anti-inflammatory drug (NSAID) that can suppress a persistent inflammatory response, leading to improved wound healing. The results demonstrated that the highest NSAID concentration released is achieved when gauzes were previously cationized with poly(diallyldimethylammonium chloride) (PDDA) and high concentration of phospholipid (≈3000 μM) and multilamellar liposomes (MLVs) were used. MLVs were also the best vehicle considering their biocompatibility with skin human fibroblasts, where no toxicity was observed for neither of the tested conditions. The developed functionalized gauzes can be, therefore, a good strategy to treat chronic wounds.Helena Ferreira, Teresa Matama and Carla Silva thank POPH/FSE for co-financing and FCT for fellowships SFRH/BPD/38939/2007, SFRH/BPD/47555/2008, SFRH/BPD/46515/2008, respectively. This work was supported by FEDER through POFC - COMPETE and by national funds from FCT through the project PEst-C/BIA/UI4050/2011

Carob pulp syrup : a potential Mediterranean carbon source for carotenoids production by Rhodosporidium toruloides NCYC 921

ABSTRACT: Carob pulp syrup (CPS) was used as carbon source to produce carotenoids from Rhodosporidium toruloides. To increase the carbon concentration in the growth medium aiming at the carotenoid production improvement, the CPS was concentrated and two different total sugar (TS) concentrations (195.6 g/L and 548.7 g/L) were studied. CPS 195.6 g/L TS contained 4.1 g/L and 0.7 g/L of hydroxymethyl furfural (HMF) and furfural, respectively. CPS 548.7 g/L TS contained 17.7 g/L of HMF and 1.2 g/L of furfural, respectively. >42% of metabolically active cells (with intact membrane and enzymatic activity) were detected throughout the course of the yeast cultivation on CPS 195.6 g/L TS. On the contrary, the proportion of metabolically active cells was always below 28% during the yeast cultivation on CPS 548.7 g/L TS. Nevertheless, the maximum carotenoid content and productivity (0.42 mg/g and 0.43 mg/Lh, respectively) were obtained when using CPS 548.7 g/L TS.info:eu-repo/semantics/publishedVersio

Tuning the Intramolecular Chemiexcitation of Neutral Dioxetanones by Interaction with Ionic Species

The intramolecular chemiexcitation of high-energy peroxide intermediates, such as dioxetanones, is an essential step in different chemi- and bioluminescent reactions. Here, we employed the Time-Dependent Density Functional Theory (TD-DFT) methodology to evaluate if and how external stimuli tune the intramolecular chemiexcitation of model dioxetanones. More specifically, we evaluated whether the strategic placement of ionic species near a neutral dioxetanone model could tune its thermolysis and chemiexcitation profile. We found that these ionic species allow for the “dark” catalysis of the thermolysis reaction by reducing the activation barrier to values low enough to be compatible with efficient chemi- and bioluminescent reactions. Furthermore, while the inclusion of these species negatively affected the chemiexcitation profile compared with neutral dioxetanones, these profiles appear to be at least as efficient as anionic dioxetanones. Thus, our results demonstrated that the intramolecular chemiexcitation of neutral dioxetanones can be tuned by external stimuli in such a way that their activation barriers are decreased. Thus, these results could help to reconcile findings that neutral dioxetanones could be responsible for efficient chemi-/bioluminescence, while being typically associated with high activation parameters

Carob pulp syrup : a potential Mediterranean carbon source for carotenoids production by Rhodosporidium toruloides NCYC 921

ABSTRACT: Carob pulp syrup (CPS) was used as carbon source to produce carotenoids from Rhodosporidium toruloides. To increase the carbon concentration in the growth medium aiming at the carotenoid production improvement, the CPS was concentrated and two different total sugar (TS) concentrations (195.6 g/L and 548.7 g/L) were studied. CPS 195.6 g/L TS contained 4.1 g/L and 0.7 g/L of hydroxymethyl furfural (HMF) and furfural, respectively. CPS 548.7 g/L TS contained 17.7 g/L of HMF and 1.2 g/L of furfural, respectively. >42% of metabolically active cells (with intact membrane and enzymatic activity) were detected throughout the course of the yeast cultivation on CPS 195.6 g/L TS. On the contrary, the proportion of metabolically active cells was always below 28% during the yeast cultivation on CPS 548.7 g/L TS. Nevertheless, the maximum carotenoid content and productivity (0.42 mg/g and 0.43 mg/Lh, respectively) were obtained when using CPS 548.7 g/L TS.info:eu-repo/semantics/publishedVersio

Biofuels and high value added products from the yeast Rhodosporidium toruloides NCYC 921: Strategies towards a true cost-effective and environmentally sustainable integrated multiproduct driven biorefinery [Poster]

Single-cell oils (SCO) have been considered a promising source of 3rd generation biofuels mainly in the final form of biodiesel. However, its high production costs have been a barrier towards the commercialization of this commodity. The fast growing yeast Rhodosporidium toruloides NCYC 921 has been widely reported as a potential SCO producing yeast. In addition to its well-known high lipid content (that can be converted into biodiesel), is rich in high value added products such as carotenoids with commercial interest. The process design and integration may contribute to reduce the overall cost of biofuels and carotenoid production and is a mandatory step towards their commercialization. The present work addresses the biomass disruption, extraction, fractionation and recovery of products with special emphasis on high added valued carotenoids (beta-carotene, torulene, torularhodin) and fatty acids directed to biodiesel. The chemical structure of torularhodin with a terminal carboxylic group imposes an additional extra challenge in what concern its separation from fatty acids. The proposed feedstock is fresh biomass pellet obtained directly by centrifugation from a 5L fed-batch fermentation culture broth. The use of a wet instead of lyophilised biomass feedstock is a way to decrease processing energy costs and reduce downstream processing time. These results will contribute for a detailed process design. Gathered data will be of crucial importance for a further study on Life-Cycle Assessment (LCA)