Banca: João Andrade de Carvalho Júnior / Banca: José Antônio Perrella Balestieri / Banca: Genésio José Menon / Banca: José Roberto Simões Moreira / Bancs: Arnaldo césar da Silva Walter / Resumo: No presente trabalho, foi desenvolvido um algoritmo para descrever a cinética da incrustação das proteínas presentes no soro do leite, tendo como subsídio as curvas de solubilidade das mesmas. Tais curvas foram determinadas experimentalmente a temperaturas na faixa de 40- 100C, incluindo a dependência do pH, entre 4,0 e 7,0. O algoritmo foi desenvolvido para aplicação no interior de tubos cilíndricos permitindo um modelo matemático unidimensional. O sistema de equações foi resolvido pelo método de diferenças finitas com a aplicação do algoritmo na linguagem Delphi 6.0. Os resultados obtidos foram comparados com os resultados dos ensaios experimentais realizados em um trocador de calor tubular construído na planta piloto do Departamento de Ciências Agrárias da Universidade de Taubaté. Os resultados mostraram que a solubilidade proteica depende da temperatura e do pH; já a cinética de incrustação, além da temperatura e do pH do fluido, depende também da vazão mássica do mesmo. O tempo necessário para o decréscimo de 30% do raio interno do tubo foi menor para maiores valores de vazão e temperatura e em pH próximo do ponto isoelétrico das proteínas do soro do leite (5,0), visto que a solubilidade proteica é mínima nestas condições. A deposição das proteínas foi mais acentuada na região de entrada do tubo. De acordo com os resultados obtidos no pasteurizador construído, observou-se convergência dos mesmos com os resultados obtidos pela simulação, validando os modelos cinéticos propostos pelo algoritmo / Abstract: In present work an algorithm was developed to describe fouling kinetics of whey proteins, based on these proteins solubility curves. Such curves were determined experimentally in the range of 40-100C, including dependence with pH, among 4.0 to 7.0. The algorithm was developed for cylindrical tubes thus leading to a less complex one-dimensional mathematical model. The system of equations was solved by the finite differences method with an algorithm developed in Delphi 6.0 and the results obtained were compared with the results of the experimental tests carried out on a tubular heat exchanger, constructed in the pilot plant of the Agronomy Department, in Taubate University. Experimental results showed that protein solubility depends on the solution temperature and pH and the fouling kinetics was dependent on the fluid temperature and pH, as well as the mass flow rate. The time needed for 30% decrease on the internal radius was smaller for higher values of both temperature and flow rate, as well as near the isoelectric point of whey proteins (pH around 5.0), since protein solubility is minimal under these conditions. Protein deposition was more intense in the tube entrance. According to the experimental results obtained by the constructed pasteurizer, it was observed convergence with those obtained from the simulation, verifying, therefore, the validation of kinetic models proposed by the algorithm

Purpose: The aim of this study was to investigate the usefulness of formulation approaches to minimise injection site reactions for poorly soluble drugs. The specific objectives were to modify the injection site reactions by identification of irritant components in the formulation and control of their release kinetics; and to gain understanding of formulation approaches to create a favourable microenvironment in the tissues allowing better tissue tolerance and drug absorption. Methods: Physicochemical properties of the model drug, ricobendazole (RBZ) were characterised using conventional methods. Three formulation approaches to minimise irritancy of the low pH RBZ solution were assessed. An in vitro method using 96-well microplates and a microtiter plate reader was used for detection of drug precipitation on dilution for formulation characterisation. Cellular damage by the formulations was investigated in L929 fibroblasts using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy phenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) and lactate dehydrogenase (LDH) assays. Tissue tolerance and pharmacokinetics were simultaneously investigated after subcutaneous injection in sheep. A low pH RBZ solution was used as a reference formulation. Results: Preformulation studies showed that RBZ was practically insoluble in water and oils, and was slightly soluble in commonly used co-solvents. Solubility was slightly improved by complexation with hydroxypropyl-β-cyclodextrin (HP-β-CD, K₁:₁ = 311 M⁻�) or a combination of low pH (> 2) with surfactants or co-solvents. A U-shaped pH-solubility profile in aqueous solutions indicated that RBZ is an ampholyte. pKa values measured by absorbance spectroscopy and pH solubility methods were 3.45 and 3.76 (basic) and 9.82 and 9.53 (acidic) respectively. The partition coefficient was 14.3 - 15.2 at pH 6 - 9 and less at higher or lower pH. In aqueous solutions, RBZ showed a V-shaped pH-degradation rate profile and was most stable at pH 4.8. Degradation pathways were identified as hydrolysis and oxidation. Three RBZ injectables (5%) were obtained by modification of the low pH RBZ solution; addition of 20% HP-β-CD, incorporation into a w/o emulsion, and a microemulsion (ME). On dilution with SPB, the onset time of drug precipitation was prolonged and the rate was reduced in the presence of HP-β-CD. The w/o emulsion had a low viscosity (< 60 mPa.s) and exhibited Newtonian flow. Drug release versus the square root of time was linear and the release rate could be adjusted by phase ratio and droplet size. Drug release was found to be by diffusion. A coarse emulsion layer appeared at the interface between the ME and buffer. Drug release from the ME was faster than from the emulsion and was linear with the square root of time. On titration into SPB, the three formulations showed controlling effects on the release of H₃O⁺ compared to the reference formulation. RBZ (0.1 mg/ml) was more toxic to L929 cells than the co-solvent propylene glycol (50 mg/ml). The formulations showed greater cytotoxicity than their vehicles in the order: ME > RBZ solution = emulsion > HP-β-CD. HP-β-CD and emulsion excipients showed little or no cytotoxicity. The MEs exhibited more toxicity in the LDH assay than in the MTS assay. A reversed phase HPLC assay for simultaneous determination of RBZ and its metabolite in sheep plasma using an isocratic system with UV detection was developed and used in the pharmacokinetic studies. Plasma samples were prepared by solid phase extraction. A suitable internal standard was selected by quantitative structure-retention relationships analysis. The composition of a ternary mobile phase was optimised with the assistance of multiple linear regression. The assays were linear over the concentration range 10 - 1000 ng/ml for both analytes (r > 0.999) with satisfactory inter-day and intra-day precision and accuracy (CV < 10%). The recoveries for all analytes were > 96%. A pilot study in sheep suggests that injection of the vehicles (the CD, emulsion and ME) caused virtually no pain on injection or site reactions. Both the reference formulation and its vehicle induced pain on injection and resulted in swollen tissues. Histology after two weeks showed granulation for the formulation, but not the vehicle. In contrast, animals showed virtually no injection site reactions with the ME and emulsion. The HP-β-CD formulation gave transient pain on injection but a two-fold increase in bioavailability compared with the reference. The emulsion produced sustained drug release and increased drug absorption. In the main study, the HP-β-CD vehicle showed good tissue compatibility. Irritation by the HP-β-CD formulation was attributed to the low pH. Cmax, tmax and AUC0-[infinity] for the reference formulation were 1.3 � 0.3 [mu]g/ml, 9.6 � 2.9 h and 36.7 � 9.2 [mu]g�h/ml respectively, while the corresponding data for the HP-β-CD formulation were 2.9 � 0.8 [mu]g/ml, 5.0 � 0.6 h and 54.5 � 15.3 [mu]g�h/ml respectively. The half-life following the injection of the HP-β-CD formulation (5.5 � 2.8 h) was shorter than that of the reference formulation (8.5 � 3.4 h). Conclusions: Injection site reactions may be minimised by identification of irritant components in a formulation and by controlling their release. Controlling the burst release of the poorly water soluble drug RBZ in a low pH solution could improve tissue tolerance and minimise post-injection precipitation, and hence increase drug bioavailability. In addition, HP-β-CD was a useful local injectable carrier which significantly enhanced the absorption of RBZ after subcutaneous injection in sheep.

Metals in industrial settings such as power plants are often subjected to high temperature and pressure aqueous environments, where failure to control corrosion compromises worker and environment safety. For instance, zircaloy (1.2-1.7 wt.% Sn) fuel rods are exposed to aqueous 250-310 oC coolant in CANDU reactors. The Pourbaix (EH-pH) diagram is a plot of electrochemical potential versus pH, which shows the domains of various metal species and by inference, corrosion susceptibility. Elevated temperature data for tin +II and tin +IV species were obtained using solid-aqueous phase equilibria with the respective oxides, in a batch vessel with in-situ pH measurement. Solubilities, determined via spectroscopic techniques, were used to calculate equilibrium constants and the Gibbs energies of Sn complexes for E-pH diagram construction. The SnOH3+ and Sn(OH) species were incorporated, for the first time, into the 298.15 K and 358.15 K diagrams, with novel G ͦ values determined at 358.15 K. / UOIT

Low phosphate fertilizer efficiency in high pH soils is primarily due to the retardation of P movement in the soil-P fertilizer reaction zone. The objective of this study was to obtain fundamental information on the influence of multi-ionic interactions on the solubility and diffusion of P in columns containing a model soil system and two soil types. The study also aimed to identify the salt combinations and factors that have the potential to enhance the solubility and movement of P in calcareous soil condition. The results showed that the interaction of NH4+ and SO42- was consistent at enhancing the water solubility and movement of P under a high soil pH condition. This effect was attributed to the combination of various mechanistic factors associated with (NH4)2SO4 compound including significant pH reduction, cation exchange reaction of NH4+ with the exchangeable Ca2+, and anionic competition of SO42- with P for precipitation with Ca2+. / October 2006

No description available.

A high speed stirring apparatus was constructed for following the kinetics of very rapid solvent extractions. Reactions with half-lives of 15 seconds can be followed with good precision. Experimental data obtained with the device are shown to be superior to kinetic data for the same reaction obtained with batch shakers and cruder stirring devices. The apparatus was used to determine the rate law for the extraction of copper by 2-hydroxyl-5-nonylbenzophenone oxime(I) and 5-dodecyl-2-hydroxylbenzophenone oxime(II). The rate law for the extraction of copper by I catalyzed by 5,8-diethyl-7-hydroxy-6-dodecanone oxime(III) was also determined. Equilibrium data are used to characterize the stoichiometry of the extracted complexes. Compound I, which is an aromatic β-hydroxyoxime, extracts copper as the 2:1 neutral chelate. Compound III, which is an aliphatic α-hydroxyoxime, has a much more complicated extraction chemistry. Experimental evidence indicates the existence of a conventional 2:1 neutral chelate, a neutral (possibly polymeric) complex, and a singly charged 1:1 complex which extracts as an ion pair with a monovalent anion. Distribution constants between chloroform and water were also determined for each ligand. The experimentally observed distribution constants for I and II are much lower than constants derived from theoretical calculations. Compound III has a partitioning constant which is in good agreement with its theoretically calculated value. The rate equations for the extraction of copper by I and II, and for the extraction of copper by I catalyzed by III, are all first order in metal ion, second order in ligand, and inverse first order in hydrogen ion. The catalytic rate law is first order in each ligand. In the case of the reactions which are second order in ligand, the rate determining step is proposed to be the aqueous phase reaction of a 1:1 intermediate complex with the second ligand molecule. Knowledge of the partitioning constants of the ligands, which in turn provides their aqueous phase concentrations, leads to the calculation of second order reaction rate constants of 1.2 x 10('7)M⁻¹s⁻¹ for I and 1.1 x 10('7)M⁻¹ for II. In the case of the catalytic mechanism, the rate law cannot be used to discern which ligand reacts in the rate determining step. If the reactive 1:1 intermediate is assumed to be with I, then a catalytic rate constant of 9.5 x 10('9)M⁻¹s⁻¹ is obtained. A catalytic pathway proceeding through a 1:1 intermediate with III is also possible, but this complex is too poorly defined for calculating a rate constant. A kinetic study of the back extraction of copper into water from an organic solution of its 2:1 complex with I indicates three pathways. The chelate partitions into water and releases its coordinated ligands in a solvolysis reaction. Both hydrogen ion and III catalyze the stripping reaction. In the case of catalysis by III, a mixed ligand complex is proposed to partition. In conclusion, the "homogeneous phase" mechanism is found to be the better mechanistic interpretation of these reaction systems. Unlike the interfacial model, this mechanism can account for all the observed phenomena, is supported by independent measurements, and conforms to the vast body of chemical data already acquired on extraction systems.

No description available.

No description available.

Three solution models: ideal, regular, and quasi- regular, were used to predict the melting point of eutectic mixtures containing Polyethylene Glycol (PEG) 400 and PEG 4000 with nine poorly water- soluble drugs: 1-naphthoic acid, estrone, griseofulvin, indomethacin, phenobarbital, paracetamol, salicylic acid, salicylamide and naproxen. PEG 400 was physically mixed with drug at different weight percentages to determine the melting points of the pure drugs and the melting point depression using Differential Scanning Calorimetry (DSC). The PEG 4000 eutectic mixtures were processed by the solvent evaporation method. In both the PEG 400 and PEG 4000 study, the quasi-regular solution model accounted for the most realistic conditions of entropy and enthalpy of the mixtures compared to ideal and regular solution models.

Struktūrinės genomikos tyrimams reikalingi gausiai mikroorganizmuose sintetinami rekombinantiniai baltymai dažnai būna netirpūs. Tradiciniai tirpių ir teisingos struktūros baltymų gavimo metodai – sintezė žemoje temperatūroje, skirtingo stiprumo promotoriai, tirpumą didinantys priedai, netirpaus baltymo suliejimas su tirpiu baltymu ar paraleli tikslinio baltymo ir įvairių šaperonų sintezė ne visada padeda. Šios priemonės nepakeičia baltymo vidinio gebėjimo susiklostyti į tirpią ir stabilią struktūrą, ir net pavykus tokį baltymą ištirpinti pradiniuose sintezės ar gryninimo bandymuose jis gali vėl agreguotis. Galingas tirpesnių baltymų variantų kūrimo metodas yra jų evoliucija in vitro, kurios metu iš mutantinių baltymų kolekcijos tirpesni baltymų variantai atrenkami pagal prie jų prijungto reporterinio baltymo funkciją. Baltymams būdinga didžiulė struktūros ir savybių įvairovė, todėl tokiems eksperimentams yra labai svarbu parinkti tinkamomis atrankai savybės pasižymintį reporterį. Kelių ar net keliolikos alternatyvių reporterių bei su jais susijusių atrankos sistemų lygiagretus panaudojimas baltymų evoliucijos eksperimentuose padidintų sėkmės tikimybę. Šiame darbe buvo kuriama tirpesnių baltymų atrankos sistema, kaip reporterinius baltymus naudojanti DNR metiltransferazes. Realizuojant šią užduotį eksperimentiniam patikrinimui buvo pasirinktos penkios skirtingoms klasėms priklausančios DNR metiltransferazės. Įvertinus jų tirpumą bei veiklumą atitinkami genai per lanksčią... [toliau žr. visą tekstą] / Overexpressed recombinant proteins required for structural genomics are often insoluble. Conventional approaches to obtain soluble, correctly folded protein include low-temperature expression, promoters with different strengths, fusion of the protein with a more soluble partner, coexpression of folding catalyst and chaperones. These approaches do not always work, because they fail to modify the intrinsic folding stability and solubility of the protein. Even when a fraction of the protein is obtained in a soluble form during initial expression or refolding experiments, the protein may still aggregate irreversibly during subsequent workup. In vitro evolution is powerful approach to obtain more soluble protein variants. After protein evolution in vitro more soluble proteins variants from library of mutants can be detected by fusion reporter tags. There is a vast diversity of protein structures and their properties, therefore it is very important to choose for such experiments reporter with good characteristic for genetic screen. Parallel use of few or more alternative reporters in protein evolution experiments may enhance possibility to select more soluble protein variants. In this study was created selection system of more soluble proteins, in which five DNA methyltransferases from different classes were used as fusion reporters. Solubility and activity of methyltransferases was assayed and then appropriate genes of five methyltransferases were fused via flexible linker with... [to full text]