On the 1H NMR spectra of weak electrolytes under the influence of strong electrolytes at low concentrations

Physical chemistry has yet to provide a convincing explanation for the many distinct ways the cosolute's properties are perturbed when under the field of action of salt ions. For that reason, a systematic and gradual approach to the problem was sought, with the present work being a step in that direction. Thus, acetic acid and n-butylamine were selected as simple models for the charged carboxyl and amine groups in more complex solutes, like proteins. The influence of the gradual addition of inorganic salts on these compounds' proton nuclear magnetic resonance spectra was analyzed. The salt concentration varied from 0.01 to roughly 100 mmol.L−1. The reported results suggest that at a low salt concentration ( divalent > monovalent. Therefore, the experimental facts herein reported show that the effect of salt ions at low concentrations upon the properties of other solutes can be rationalized by conventional chemical concepts, in which chemical equilibrium plays an important role. Furthermore, the results strongly support the classical interpretation of salt ions, which are charged bodies that, in solution, exert chiefly electrostatic forces.publishe

Distinct roles of salt cations and anions upon the salting-out of electro-positive albumin

Precipitation experiments of electro-positive albumin by the action of a wide number of salts, and at differentconcentrations, were performed at a constant temperature (25 °C). The pH range studied covered extreme acidicconditions up to hydronium concentrations where the dissociation of the protein carboxyl groups becomes no-ticeable. The time required for the clouding phenomenon to occur and the quantity of salted-out protein werealso ascertained. The results here reported show that the salt anion is the main salting-out species for the posi-tively charged protein, where their efficacy in salting-out albumin from aqueous solution increases in theorder: F−bCl−bBr−bNO3−bI−bSCN−~ ClO4−bSO42−. Although at extreme pH conditions the salt cationhas no significant influence on the protein salting-out, experiments performed at higher pH values, where thecarboxyl groups starts to dissociate, revealed a non-monotonic effect of the salt upon protein precipitation. Weinterpret this observation as a result of the presence of different protein forms, with which the salt cation partic-ipates in chemical equilibrium. Overall, the proteins salting-out phenomenon induced by salt can be rationalizedby a general mechanism driven by electrostatic interactions and chemical equilibrium concepts.publishe

How does dilution affect the conductivity, the propensity to aggregate and the biological activity of enzymes?

The current theories do not provide a convincing explanation for many of the protein' manifestations in solution. Therefore, to shed some light on this critical question, the present work analyzed the effect of dilution on the ability of proteins to catalyze chemical reactions, the so-called biological activity. As models enzymes, laccase from Trametes versicolor and chicken egg white lysozyme were used. The results show that the enzymes' specific biological activity increases on dilution. Three explanations for the intriguing observation were advanced and submitted to experimental scrutiny. Amongst the three hypotheses, only one was corroborated by experiments. According to this explanation, when dissolved in water, proteins reveal two populations: one biologically active whose relative occurrence increases on dilution and another which is not active and whose molecular proportion varies in the opposite direction. Therefore, the reported experimental facts strongly support the chemical behaviour of the proteins in the solution. According to the herein-advocated concepts, they could undergo a dissociation process similar to that found in electrolyte chemistry.publishe

Linear relationships between partition coefficients of different organic compounds and proteins in aqueous two-phase systems of various polymer and ionic compositions

Analysis of the partition coefficients of small organic compounds and proteins in different aqueous two-phase systems under widely varied ionic compositions shows that logarithms of partition coefficients for any three compounds or proteins or two organic compounds and one protein are linearly interrelated, although for protein(s) there are ionic compositions when the linear fit does not hold. It is suggested that the established interrelationships are due to cooperativity of different types of solute–solvent interactions in aqueous media. This assumption is confirmed by analysis of distribution coefficients of various drugs in octanol-buffer systems with varied ionic compositions of the buffer. Analysis of the partition coefficients characterizing distribution of variety of drugs between blood and different tissues of rats in vivo reported in the literature showed that the above assumption is correct and enabled us to identify the tissues with the components of which the drug(s) may engage in presumably direct interactions. It shows that the suggested assumption is valid for even complex biological systems.info:eu-repo/semantics/publishedVersio

Prediction of protein partition in polymer/salt aqueous two-phase systems using the modified Wilson model

The extension of the modified Wilson model to multicomponent mixtures, presented in a previous publication, is applied to predict the partition of the following proteins: bovine serum albumin (BSA), lysozyme, glucosidase and catalase, in the Na2SO4/PEG6000 and K2HPO4/PEG6000 aqueous two-phase systems at 298.15 K. The results obtained with the model are, in general, in fair agreement with the experimental data. In the modelling methodology adopted here, special emphasis on the so-called charge effects to the protein partition was given. To our knowledge, no experimental information is available in the literature that allows to estimate the interaction parameters between these macromolecules and the components present in the aqueous two-phase systems (water, salts and polymer). Thus, the deviations observed between calculated and experimental protein partition are mainly due to some assumptions made in the predictive methodology.info:eu-repo/semantics/publishedVersio

CARACTERÍSTICAS GRANULOMÉTRICAS DO SOLO DA FUNDAÇÃO CAIO MARTINS, SÃO FRANCISCO, MG

Este estudo busca apresentar o perfil granulométrico do solo da Fundação Caio Martins (FUCAM), área estadual localizada à beira do rio São Francisco, no município também denominado São Francisco, no Norte de Minas Gerais. Para isso coletou-se amostras de solo no ano de 2016 e através do uso de peneiras próprias do laboratório de Laboratório de Mecânica dos Solos da UFOP, foi possível reconhecer o perfil granulométrico de cada uma das seis amostragens realizadas que representavam toda a área de estudo pesquisada. Como resultado foi possível afirmar que todas as amostras apresentaram textura siltosa, destacando-se o fato de que a medida que a ação antrópica por local de coleta era detectada, maiores frações de pedregulho eram detectadas, por consequência, o aumento do perfil síltico por região amostral se dá à medida que o solo se apresenta mais conservado da ação humana, sendo possível afirmar que o mais degradado, sobre a ótica granulométrica é exatamente o setor Leste, onde se localizam a maior parte das atividades impactantes do local e onde estão a maior parte das ações da Fundação. Obviamente mais estudos, em especial o geoquímico, são importantes de serem realizados para se afirmar quais as espécies mais adequadas ao cultivo, mas sob um ponto de vista granulométrico do solo, todos os vegetais arbóreos originários do Cerrado são indicados para o plantio na área da FUCAM

Os fósseis de Santa Maria (Açores) : a jazida da Prainha.

PREFÁCIO: O trabalho que agora se apresenta de Sérgio Ávila e colaboradores é mais um precioso contributo para a divulgação científica que emerge de trabalho de investigação académica da Universidade dos Açores. É um trabalho que procura conciliar um rigor e uma descrição exaustiva e profusamente ilustrada dos elementos factuais paleontológicos e geológicos associados à jazida da Prainha, com uma obra apelativa e agradável de desfolhar, ler e consultar. Este tipo de produtos académicos para a comunidade, de extensão universitária como agora se fala, é de extrema importância para a Região Autónoma dos Açores, em particular, e para Portugal, em geral, por três ordens de razões. Em primeiro lugar porque, contrariamente aos ditados e sabedoria popular, as rochas e outros elementos do património geológico, são frágeis e efémeros. Um dos aspectos de maior fragilidade são os fósseis, propriamente ditos, o que é mais fácil de entender. Mais difícil é reconhecer que as próprias jazidas fossilíferas, fósseis e seu enquadramento geológico, o qual pode incluir filões, falhas, minerais, seixos rolados, etc., são igualmente bastante frágeis quer a acções de erosão e alteração naturais quer a acções antrópicas. Quanto às primeiras a única e melhor atitude é proceder ao seu estudo e registo documental, nomeadamente fotográfica, como generosamente se apresenta nesta obra. Quanto às segundas, o modo mais eficaz de as preservar é dar a conhecer às populações, em geral, e às autarquias e entidades de gestão do território, em particular, no sentido de prevenir o licenciamento de obras ou infra-estruturas que poderão comprometer irremediavelmente esse Património Natural. Efectivamente, numa região balnear como a da Praia Formosa, uma eventual pressão urbanística pode levar à destruição destes seus elementos patrimoniais únicos. Únicos, não só no contexto da Ilha de Santa Maria, como no contexto da Região Autónoma dos Açores, ou mesmo do Continente. Em segundo lugar, estão em curso vários esforços no sentido de que o conjunto das nove ilhas açorianas venham a ser integradas na Rede Europeia de Geoparques e, como tal, sejam reconhecidas pela UNESCO como mais um elemento da Global Network of Geoparks. Tal galardão é consagrado pela excelência do seu Património geológico e paleontológico, o qual encontra neste livro um excelente aliado e um repositório de informação da qual se irão retirar elementos necessários à subsequente produção de textos de divulgação em língua estrangeira, fundamentalmente anglo-saxónica. Por outro lado, ficam bem expressos, os argumentos da necessidade desta jazida se converta em mais um dos magníficos e bem sucedidos exemplos de geoconservação e valorização ambiental que estão a registar-se por todo o arquipélago açoriano. Em terceiro lugar, obras como a que agora se edita ajudam à interiorização por parte da população de Santa Maria, e por todos quantos a visitam, da singularidade geológica desta ilha e do valor científico e patrimonial que as suas unidades fossilíferas representam. Elas ilustram de modo particularmente exuberante as alterações climáticas que o nosso Planeta tem vindo a sofrer, actualmente acompanhadas com maior acuidade pela sociedade e os media. Estes afloramentos particularmente ricos em conteúdo fóssil, intercalados ou embutidos em sequências de rochas vulcânicas e sedimentares, são os únicos testemunhos que restam das comunidades bióticas que povoaram as águas superficiais e as regiões costeiras insulares do Atlântico Norte, há milhares de anos (no caso da Prainha ou Lagoinhas) ou mesmos há milhões de anos, como as jazidas do Monumento Natural Regional da Pedreira do Campo, Pedreira da Cré, “Pedra que Pica” ou Ponta da Malbusca, para citar só algumas. Todas elas são singulares excepções que complementam os registos sedimentares das bacias oceânicas envolventes, os quais têm sido, e continuarão a ser, alvo de investigação paleoceanográfica do Global Change. No entanto, estas jazidas, são os únicos testemunhos das comunidades costeiras pretéritas, com as quais é possível estabelecer comparações e mapas de distribuição biogeográfica, um dos temas fortes presentes nesta obra. (Mário Cachão)Universidade dos Açores; Departamento de Biologia da UAÇ; CIBIO-Açores; IMAR; Câmara Municipal de Vila do Porto; Clube Naval de Santa Maria; GEOBIOTEC; Viagens de Turismo MELO; Hotel Praia de Lobos; Governo dos Açores; Secretaria Regional da Ciência, Tecnologia e Equipamentos

Hydrogen bond arrangement is shown to differ in coexisting phases of aqueous two-phase systems

Analysis by attenuated total reflection-Fourier transform infrared spectroscopy shows that each coexisting phase in aqueous two-phase systems has a different arrangement of hydrogen bonds. Specific arrangements vary for systems formed by different solutes. The hydrogen bond arrangement is shown to correlate with differences in hydrophobic and electrostatic properties of the different phases of five specific systems, four formed by two polymers and one by a single polymer and salt. The results presented here suggest that the arrangement of hydrogen bonds may be an important factor in phase separation.P.P.M. acknowledges University of Aveiro, CICECO-Aveiro Institute of Materials for funding in the framework of the project UIDB/5011/2020 and UIDP/50011/2020, financed by national funds through the FCT/MEC contract foreseen in the numbers 4, 5, and 6 of the article 23, of the Decree-Law 57/2016, of August 29, changed by Law 57/2017, of July 19.publishe

Pool boiling of nanofluids on biphilic surfaces: An experimental and numerical study

This study addresses the combination of customized surface modification with the use of nanofluids, to infer on its potential to enhance pool-boiling heat transfer. Hydrophilic surfaces patterned with superhydrophobic regions were developed and used as surface interfaces with different nanofluids (water with gold, silver, aluminum and alumina nanoparticles), in order to evaluate the effect of the nature and concentration of the nanoparticles in bubble dynamics and consequently in heat transfer processes. The main qualitative and quantitative analysis was based on extensive post-processing of synchronized high-speed and thermographic images. To study the nucleation of a single bubble in pool boiling condition, a numerical model was also implemented. The results show an evident benefit of using biphilic patterns with well-established distances between the superhydrophobic regions. This can be observed in the resulting plot of the dissipated heat flux for a biphilic pattern with seven superhydrophobic spots, δ = 1/d and an imposed heat flux of 2132 w/m2. In this case, the dissipated heat flux is almost constant (except in the instant t* ≈ 0.9 when it reaches a peak of 2400 W/m2), whilst when using only a single superhydrophobic spot, where the heat flux dissipation reaches the maximum shortly after the detachment of the bubble, dropping continuously until a new necking phase starts. The biphilic patterns also allow a controlled bubble coalescence, which promotes fluid convection at the hydrophilic spacing between the superhydrophobic regions, which clearly contributes to cool down the surface. This effect is noticeable in the case of employing the Ag 1 wt% nanofluid, with an imposed heat flux of 2132 W/m2, where the coalescence of the drops promotes a surface cooling, identified by a temperature drop of 0.7 °C in the hydrophilic areas. Those areas have an average temperature of 101.8 °C, whilst the average temperature of the superhydrophobic spots at coalescence time is of 102.9 °C. For low concentrations as the ones used in this work, the effect of the nanofluids was observed to play a minor role. This can be observed on the slight discrepancy of the heat dissipation decay that occurred in the necking stage of the bubbles for nanofluids with the same kind of nanoparticles and different concentration. For the Au 0.1 wt% nanofluid, a heat dissipation decay of 350 W/m2 was reported, whilst for the Au 0.5 wt% nanofluid, the same decay was only of 280 W/m2. The results of the numerical model concerning velocity fields indicated a sudden acceleration at the bubble detachment, as can be qualitatively analyzed in the thermographic images obtained in this work. Additionally, the temperature fields of the analyzed region present the same tendency as the experimental results.This work was funded by Portuguese national funds of FCT/MCTES (PIDDAC) through the base funding from the following research units: UIDB/00532/2020 (Transport Phenomena Research Center, CEFT), UIDB/04077/2020 (MEtRICs) and UIDP/04436/2020. The authors are also grateful for the funding of FCT through the projects LISBOA-01-0145-FEDER-030171/NORTE-01-0145-FEDER-030171 (PTDC/EME-SIS/30171/2017), funded by COMPETE2020, NORTE2020, PORTUGAL2020 and FEDER. The authors also acknowledge FCT for partially financing the research under the framework of the project UTAP-EXPL/CTE/0064/2017, financiado no ambito do Projeto 5665-Parcerias Internacionais de Ciencia e Tecnologia, UT Austin Programme. Mr Pedro Pontes also acknowledgesFCT for his fellowship ref. SFRH/BD/149286/2019

Phytochemical Characterization and Biological Evaluation of the Aqueous and Supercritical Fluid Extracts from Salvia sclareoides Brot

Plants belonging to the genus Salvia (Lamiaceae) are known to have a wide range of biological properties. In this work, extracts obtained from the aerial parts of Salvia sclareoides Brot. were evaluated to investigate their chemical composition, toxicity, bioactivity, and stability under in vitro gastrointestinal conditions. The composition of the supercritical fluid extract was determined by GC and GC-MS, while the identification of the infusion constituents was performed by HPLC-DAD and LC-MS. The in vitro cytotoxicity of both extracts (0-2 mg/mL) was evaluated in Caco-2 cell lines by the MTT assay. The anti-inflammatory and anticholinesterase activities were determined through the inhibition of cyclooxygenase-1 and acetylcholinesterase enzymes, while β-carotene/linoleic acid bleaching test and the DPPH assays were used to evaluate the antioxidant activity. The infusion inhibited cyclooxygenase-1 (IC50 = 271.0 μg/mL), and acetylcholinesterase (IC50 = 487.7 μg/ mL) enzymes, also demonstrated significant antioxidant properties, as evaluated by the DPPH (IC50 = 10.4 μg/mL) and β-carotene/linoleic acid (IC50 = 30.0 μg/mL) assays. No remarkable alterations in the composition or in the bioactivities of the infusion were observed after in vitro digestion, which supports the potential of S. sclareoides as a source of bioactive ingredients with neuroprotective, anti-inflammatory and antioxidant properties.This work was supported by Fundação para a Ciência e a Tecnologia (FCT), Project UID/MULTI/00612/2013 and UID/QUI/50006/2013. FCT is also acknowledged for PJAM post-doctoral fellowship (SFRH/BPD/86948/2012) and for CG FCT Investigator (IF/01332/2014). The European Commission is also acknowledged for approval of the INOVAFUNAGEING commitment and the support of the projects PERSSILAA-FP7-ICT-2013-10, Project Nr. 610359, and D3i4AD, FP7-PEOPLE-2013-IAPP, GA 612347. The authors also gratefully acknowledge the collaboration of Prof. Ana Cristina Figueiredo (DBV-FCUL), for GC and GC-MS analysis, and of Prof. Maria Helena Florêncio (DQB-FCUL) for LC-MS support.info:eu-repo/semantics/publishedVersio