Grafting of adipic anhydride to carbon nanotubes through a Diels-Alder cycloaddition/oxidation cascade reaction

Accepted Manuscript

In silico constraint-based strain optimization methods: the quest for optimal cell factories

Shifting from chemical to biotechnological processes is one of the cornerstones of 21st century industry. The production of a great range of chemicals via biotechnological means is a key challenge on the way toward a bio-based economy. However, this shift is occurring at a pace slower than initially expected. The development of efficient cell factories that allow for competitive production yields is of paramount importance for this leap to happen. Constraint-based models of metabolism, together with in silico strain design algorithms, promise to reveal insights into the best genetic design strategies, a step further toward achieving that goal. In this work, a thorough analysis of the main in silico constraint-based strain design strategies and algorithms is presented, their application in real-world case studies is analyzed, and a path for the future is discussed.

The mineralogy and chemistry of the German and Portuguese tiles used to face a historic building in the Amazon region and their natural susceptibility to tropical weathering

During the 19th century, the most prominent buildings of the city of Belém were faced entirely with tiles manufactured in Portugal and Germany, which now exhibit distinct degrees of degradation. The Pinho mansion is one of the most important of these buildings and was selected for the investigation of the action of the tropical Amazonian climate on the degradation of the tiles. To achieve this objective, the tiles were mapped for organic and inorganic degradation, and samples were collected for analysis. The minerals were determined by XRD, the chemical composition by classical wet methods and SEM/EDS, and the microorganisms under the microscope. The results show that the German and Portuguese tiles are quite different in their composition. While both ceramic bodies are composed of SiO2 and Al2O3, CaO was found only in the Portuguese tile. The low Na2O and K2O contents indicate the addition of materials to reduce the fusion temperature. SiO2 and PbO are the main constituents of the glaze, with CoO and FeO being added as pigment. The ceramic body of the German tiles is constituted of quartz, mullite, and cristobalite, in contrast with the Portuguese tiles, which are made of quartz, gehlenite, diopside, calcite, and feldspars. The glazes are XRD-amorphous. The chemical and mineralogical differences between the German and Portuguese tiles indicate that they were produced from different raw materials under distinct thermal processes. The most prominent weathering-related modifications are the thin layers (German tiles), oxidation stains, dark stains, the detachment of the tile (Portuguese tiles), loss of the glaze and powdering of the ceramic body (Portuguese tiles) through the establishment of Cyanophyta and Bacillariophyta.. The distinct degradation patterns of the tiles exposed to the tropical Amazon climate are a consequence of their distinct mineralogy and chemistry.

Chemical features of Ganoderma polysaccharides with antioxidant, antitumor and antimicrobial activities

Review aricle

Chemical functionalization in bionanoparticles

Dissertação de mestrado em Biofísica e Bionanossistemas

Comparison of the effect of two HMG CoA reductase inhibitors on LDL susceptibility to oxidation

OBJECTIVE: To study the differences between fluvastatin and pravastatin regarding LDL susceptibility to oxidation, plasma levels of total cholesterol (TC), HDL-C, LDL-C and triglycerides (TG) in hypercholesterolemic patients with established coronary heart disease (CHD). METHODS: A double-blind randomized parallel study was conducted that included 41 hypercholesterolemic outpatients with CHD treated at the Instituto de Cardiologia do Rio Grande do Sul. The inclusion criteria were LDL-C above 100 mg/dL and triglycerides below 400 mg/dL based on 2 measures. After 4 weeks on a low cholesterol diet, those patients that fullfilled the inclusion criteria were randomized into 2 groups: the fluvastatin group (fluvastatin 40 mg/day) and the pravastatin group (pravastatin 20 mg/day), for 24 weeks of treatment. LDL susceptibility to oxidation was analyzed with copper-induced production of conjugated dienes (Cu2+) and water-soluble free radical initiator azo-bis (2'-2'amidinopropanil) HCl (AAPH). Spectroscopy nuclear magnetic resonance was used for determination of lipids. RESULTS: After 24 weeks of drug therapy, fluvastatin and pravastatin significantly reduced LDL susceptibility to oxidation as demonstrated by the reduced rate of oxidation (azo and Cu) and by prolonged azo-induced lag time (azo lag). The TC, LDL-C, and TG reduced significantly and HDL-C increased significantly. No differences between the drugs were observed. CONCLUSION: In hypercholesterolemic patients with CHD, both fluvastatin and pravastatin reduced LDL susceptibility to oxidation.

Lipoprotein (a): Structure, Pathophysiology and Clinical Implications

The chemical structure of lipoprotein (a) is similar to that of LDL, from which it differs due to the presence of apolipoprotein (a) bound to apo B100 via one disulfide bridge. Lipoprotein (a) is synthesized in the liver and its plasma concentration, which can be determined by use of monoclonal antibody-based methods, ranges from < 1 mg to > 1,000 mg/dL. Lipoprotein (a) levels over 20-30 mg/dL are associated with a two-fold risk of developing coronary artery disease. Usually, black subjects have higher lipoprotein (a) levels that, differently from Caucasians and Orientals, are not related to coronary artery disease. However, the risk of black subjects must be considered. Sex and age have little influence on lipoprotein (a) levels. Lipoprotein (a) homology with plasminogen might lead to interference with the fibrinolytic cascade, accounting for an atherogenic mechanism of that lipoprotein. Nevertheless, direct deposition of lipoprotein (a) on arterial wall is also a possible mechanism, lipoprotein (a) being more prone to oxidation than LDL. Most prospective studies have confirmed lipoprotein (a) as a predisposing factor to atherosclerosis. Statin treatment does not lower lipoprotein (a) levels, differently from niacin and ezetimibe, which tend to reduce lipoprotein (a), although confirmation of ezetimibe effects is pending. The reduction in lipoprotein (a) concentrations has not been demonstrated to reduce the risk for coronary artery disease. Whenever higher lipoprotein (a) concentrations are found, and in the absence of more effective and well-tolerated drugs, a more strict and vigorous control of the other coronary artery disease risk factors should be sought.

Convex and toric geometry to analyze complex dynamics in chemical reaction systems

Convex cone, toric variety, graph theory, electrochemical catalysis, oxidation of formic acid, feedback-loopsbifurcations, enzymatic catalysis, Peroxidase reaction, Shil'nikov chaos

Verwendung von acetyliertem Distärkephosphat und Distärkeadipat als Stabilisator in einer Lachscreme auf Emulsionsbasis

The present Bachelor thesis gives an overview of the influence of some starch esters (acetylated distarch phosphate (E 1414) and adipate (E1422)) as stabilizing agents in a salmon-emulsion-cream. The aim of this work was the development of an optimal recipe. Different concentrations of starches were used in combination with xanthan gum. The methods were used to describe the rheological, microphotographical, microbiological, chemical and sensorial characteristics of the spread. The analysis of determination and development of droplet size showed a significant reduction in coalescence process. Rheological experiments indicated that high concentrations of E 1414 are necessary getting a slightly higher viscosity than in case of the E 1422 creams. The microbiological results showed minimal differences. All tested samples showed high stability against oxidation. For the use of a new recipe acetylated distarch adipate is the better choice in this case.

A mathematical model to describe fat oxidation kinetics during graded exercise.

PURPOSE: The purpose of this study was to develop a mathematical model (sine model, SIN) to describe fat oxidation kinetics as a function of the relative exercise intensity [% of maximal oxygen uptake (%VO2max)] during graded exercise and to determine the exercise intensity (Fatmax) that elicits maximal fat oxidation (MFO) and the intensity at which the fat oxidation becomes negligible (Fatmin). This model included three independent variables (dilatation, symmetry, and translation) that incorporated primary expected modulations of the curve because of training level or body composition. METHODS: Thirty-two healthy volunteers (17 women and 15 men) performed a graded exercise test on a cycle ergometer, with 3-min stages and 20-W increments. Substrate oxidation rates were determined using indirect calorimetry. SIN was compared with measured values (MV) and with other methods currently used [i.e., the RER method (MRER) and third polynomial curves (P3)]. RESULTS: There was no significant difference in the fitting accuracy between SIN and P3 (P = 0.157), whereas MRER was less precise than SIN (P < 0.001). Fatmax (44 +/- 10% VO2max) and MFO (0.37 +/- 0.16 g x min(-1)) determined using SIN were significantly correlated with MV, P3, and MRER (P < 0.001). The variable of dilatation was correlated with Fatmax, Fatmin, and MFO (r = 0.79, r = 0.67, and r = 0.60, respectively, P < 0.001). CONCLUSIONS: The SIN model presents the same precision as other methods currently used in the determination of Fatmax and MFO but in addition allows calculation of Fatmin. Moreover, the three independent variables are directly related to the main expected modulations of the fat oxidation curve. SIN, therefore, seems to be an appropriate tool in analyzing fat oxidation kinetics obtained during graded exercise.

Liquid chromatography-tandem mass spectrometry (LC/APCI-MS/MS) methods for the quantification of captan and folpet phthalimide metabolites in human plasma and urine.

Captan and folpet are fungicides largely used in agriculture. They have similar chemical structures, except that folpet has an aromatic ring unlike captan. Their half-lives in blood are very short, given that they are readily broken down to tetrahydrophthalimide (THPI) and phthalimide (PI), respectively. Few authors measured these biomarkers in plasma or urine, and analysis was conducted either by gas chromatography coupled to mass spectrometry or liquid chromatography with UV detection. The objective of this study was thus to develop simple, sensitive and specific liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry (LC/APCI-MS/MS) methods to quantify both THPI and PI in human plasma and urine. Briefly, deuterated THPI was added as an internal standard and purification was performed by solid-phase extraction followed by LC/APCI-MS/MS analysis in negative ion mode for both compounds. Validation of the methods was conducted using spiked blank plasma and urine samples at concentrations ranging from 1 to 250 μg/L and 1 to 50 μg/L, respectively, along with samples of volunteers and workers exposed to captan or folpet. The methods showed a good linearity (R (2) > 0.99), recovery (on average 90% for THPI and 75% for PI), intra- and inter-day precision (RSD, <15%) and accuracy (<20%), and stability. The limit of detection was 0.58 μg/L in urine and 1.47 μg/L in plasma for THPI and 1.14 and 2.17 μg/L, respectively, for PI. The described methods proved to be accurate and suitable to determine the toxicokinetics of both metabolites in human plasma and urine.

Angiotensin II favors progression to heart failure in diabetic hearts: role of myocardial fatty acid oxidation downregulation

Purpose: Diabetic myocardium is particularly vulnerable to develop heart failure in response to chronic stress conditions including hypertension or myocardial infarction. We have recently observed that angiotensin II (Ang II)-mediated downregulation of the fatty acid oxidation pathway favors occurrence of heart failure by myocardial accumulation of lipids (lipotoxicity). Because diabetic heart is exposed to high levels of circulating fatty acid, we determined whether insulin resistance favors development of heart failure in mice with Ang II-mediated myocardial remodeling.Methods: To study the combined effect of diabetes and Ang II-induced heart remodeling, we generated leptin-deficient/insulin resistant (Lepob/ob) mice with cardiac targeted overexpression of angiotensinogen (TGAOGN). Left ventricular (LV) failure was indicated by pulmonary congestion (lung weight/tibial length>+2SD of wild-type mice). Myocardial metabolism and function were assessed during in vitro isolated working heart perfusion.Results: Forty-eight percent of TGAOGN mice without insulin resistance exhibited pulmonary congestion at the age of 6 months associated with increased myocardial BNP expression (+375% compared with WT) and reduced LV power (developed pressure x cardiac output; -15%). The proportion of mice presenting heart failure was markedly increased to 71% in TGAOGN mice with insulin resistance (TGAOGN/Lepob/ob). TGAOGN/Lepob/ob mice with heart failure exhibited further increase of BNP compared with failing non-diabetic TGAOGN mice (+146%) and further reduction of cardiac power (-59%). Mice with insulin resistance alone (Lepob/ob) did not exhibit signs of heart failure or LV dysfunction. Myocardial fatty acid oxidation measured during in vitro perfusion was markedly increased in non-failing hearts from Lepob/ob mice (+380% compared with WT) and glucose oxidation decreased (-72%). In contrast, fatty acid and glucose oxidation did not differ from Lepob/ob mice in hearts from TGAOGN/Lepob/ob mice without heart failure. However, both fatty acid and glucose oxidation were markedly decreased (-47% and -48%, respectively, compared with WT/Lepob/+) in failing hearts from TGAOGN/Lepob/ob mice. Reduction of fatty acid oxidation was associated with marked reduction of protein expression of a number of regulatory enzymes implied in fatty acid oxidation.Conclusions: Insulin resistance favors the progression to heart failure during chronic exposure of the myocardium to Ang II. Our results are compatible with a role of Ang II-mediated downregulation of fatty acid oxidation, potentially promoting lipotoxicity.

A Preliminary Investigation on the Chemical Composition of the Cell Surface of Five Enteropathogenic Escherichia coli Serotypes

The cell surfaces of five enteropathogenic Escherichia coli serotypes (O111:H2; O111:H12; O125:H9; O119:H6; O26:H11) were assayed by chemical methods, lectin agglutination tests and spectroscopy associated to transmission electron microscopy. Results of lectin agglutination assays showed that all strains reacted with mannosebinding lectins. Strains belonging to serotype O125:H9 also agglutinated with lectins which recognize galactose and Nacetylgalactosamine residues. The bacterial cells were treated with 0.01M phosphate buffered saline (pH 7.0) at 100oC for 2 hr and the extracts were submitted to precipitation and fractionated by Cetavlon. Phosphate, total sugar and protein contents were determined. Gas liquid chomatography-mass spectrometry analysis of alditol acetates showed the presence of galactose, mannose, fucose, glucose and traces of ribose. Spectroscopic analysis of intact cells showed the presence of a capsule-like structure which was not totally preserved after extraction. Some cells were still surrounded by an amorphous capsular-like material after polysaccharide extraction.

Biological monitoring of exposure to solvents using the chemical itself in urine: application to toluene

Objective Biomonitoring of solvents using the unchanged substance in urine as exposure indicator is still relatively scarce due to some discrepancies between the results reported in the literature. Based on the assessment of toluene exposure, the aim of this work was to evaluate the effects of some steps likely to bias the results and to measure urinary toluene both in volunteers experimentally exposed and in workers of rotogravure factories. Methods Static headspace was used for toluene analysis. o-Cresol was also measured for comparison. Urine collection, storage and conservation conditions were studied to evaluate possible loss or contamination of toluene in controlled situations applied to six volunteers in an exposure chamber according to four scenarios with exposure at stable levels from 10 to 50 ppm. Kinetics of elimination of toluene were determined over 24 h. A field study was then carried out in a total of 29 workers from two rotogravure printing facilities. Results Potential contamination during urine collection in the field is confirmed to be a real problem but technical precautions for sampling, storage and analysis can be easily followed to control the situation. In the volunteers at rest, urinary toluene showed a rapid increase after 2 h with a steady level after about 3 h. At 47.1 ppm the mean cumulated excretion was about 0.005% of the amount of the toluene ventilated. Correlation between the toluene levels in air and in end of exposure urinary sample was excellent (r = 0.965). In the field study, the median personal exposure to toluene was 32 ppm (range 3.6-148). According to the correlations between environmental and biological monitoring data, the post-shift urinary toluene (r = 0.921) and o-cresol (r = 0.873) concentrations were, respectively, 75.6 mu g/l and 0.76 mg/g creatinine for 50 ppm toluene personal exposure. The corresponding urinary toluene concentration before the next shift was 11 mu g/l (r = 0.883). Conclusion Urinary toluene was shown once more time a very interesting surrogate to o-cresol and could be recommended as a biomarker of choice for solvent exposure. [Authors]

Analysis of genetic diversity of Trypanosoma cruzi: an application of riboprinting and gradient gel electrophoresis methods

Analysis of restriction fragment length polymorphism (RFLP) profiles derived from digestion of polymerase chain reaction (PCR) products of the ribosomal 18S from Trypanosoma cruzi yields a typical `riboprint' profile that can vary intraspecifically. A selection of 21 stocks of T. cruzi and three outgroup taxa: T. rangeli, T. conorhini and Leishmania braziliensis were analysed by riboprinting to assess divergence within and between taxa. T. rangeli, T. conorhini and L. braziliensis could be easily differentiated from each other and from T. cruzi. Phenetic analysis of PCR-RFLP profiles indicated that, with one or two exceptions, stocks of T. cruzi could be broadly partitioned into two groups that formally corresponded to T. cruzi I and T. cruzi II respectively. To test if ribosomal 18S sequences were homogeneous within each taxon, gradient gel electrophoresis methods were employed utilising either chemical or temperature gradients. Upon interpretation of the melting profiles of riboprints and a section of the 18S independently amplified by PCR, there would appear to be at least two divergent 18S types present within T. cruzi. Heterogeneity within copies of the ribosomal 18S within a single genome has therefore been demonstrated and interestingly, this dimorphic arrangement was also present in the outgroup taxa. Presumably the ancestral duplicative event that led to the divergent 18S types preceded that of speciation within this group. These divergent 18S paralogues may have, or had, different functional pressures or rates of molecular evolution. Whether or not these divergent types are equally transcriptionally active throughout the life cycle, remain to be assessed.