Adenine interaction with and adsorption on Fe-ZSM-5 zeolites: A prebiotic chemistry study using different techniques

Most adsorption experiments are performed under conditions that did not exist on Earth before the life arose on it. Because adsorption is the first step for all other processes (protection against degradation and polymerization), it is important that it is performed under conditions that existed on prebiotic Earth. In this paper, we use an artificial seawater (seawater 4.0 Ga), which contains major cations and anions that could present on the oceans of the prebiotic Earth. In addition, zeolites, with substituted Fe in the framework, and adenine were probably common substances on the prebiotic Earth. Thus, study the interaction between them is an important issue in prebiotic chemistry. There are two main findings described in this paper. Firstly, zeolites with different Si/Fe ratios adsorbed adenine differently. Secondly, XAFS showed that, after treatments with seawater 4.0 Ga and adenine, an increase in the complexity of the system occurred. In general, salts of seawater 4.0 Ga did not affect the adsorption of adenine onto zeolites and adenine adsorbed less onto zeolites with iron isomorphically substituted. The C=C and NH2 groups of adenine interacted with the zeolites. Gypsum, formed from aqueous species dissolved in seawater 4.0 Ga, precipitated onto zeolites. EPR spectra of zeolites showed lines caused by Fe framework and Fe3+ species. TG curves of zeolites showed events caused by loss of water weakly bound to zeolite (in the 30-140 °C range), water bounded to iron species or cations from seawater 4.0 Ga or located in the cavities of zeolites (157-268 °C) and degradation of adenine adsorbed onto zeolites (360-600 °C). Mass loss follows almost the same order as the amount of adenine adsorbed onto zeolites. The XAFS spectrum showed that Fe3+ could be substituted into the framework of the Fe7-ZSM-5 zeolite

Spectrophotometric determination of total proteins in blood plasma: a comparative study among dye-binding methods

A comparative study between the biuret method (standard method for total proteins) and spectrophotometric methods using dyes (Bradford, 3',3",5',5"-tetrabromophenolphthalein ethyl ester-TBPEE, and erythrosin-B) was carried out for the determination of total proteins in blood plasma from rats. Bradford method showed the highest sensitivity for proteins and biuret method showed the lowest. For all the methods, the absorbance for different proteins (BSA, casein, and egg albumin) was measured and Bradford method showed the lowest variation of absorbance. The concentration of total protein obtained by using Bradford method was not statistically different (p>0.05) from concentration of total protein obtained by the biuret method. But in regard to erythrosin-B and TBPEE methods the concentrations of total protein were statistically different (p<0.05). Thus, Bradford method could be used instead of the biuret method for determination of total proteins in blood plasma

Estudo da reação entre tiocianato de amônio e Fe (II) ou Fe (III) utilizando a espectroscopia no infravermelho: um experimento de química prebiótica.

A química prebiótica estuda as reações que podem ter desempenhado um papel importante para a origem da vida na Terra. No entanto estas reações devem ser realizadas em laboratórios nas condições que existiram na Terra prebiótica. Os experimentos de laboratório do aquecimento de substâncias em estado sólido podem ser relacionados aos seguintes ambientes prebióticos: resfriamento de lava de vulcões sobre o solo e o impacto de meteoros ou cometas sobre a Terra. No presente trabalho a reação em estado sólido entre o tiocianato de amônio e Fe (II) ou Fe (III) foi estudada. As amostras foram aquecidas a 220 ºC em diversos tempos (6 horas, 24 horas, 7 dias). O principal resultado deste trabalho foi que uma reação de oxidação-redução esta ocorrendo entre o Fe (II) e o tiocianato de amônio, os espetros infravermelhos do produto de reação tiocianato de amônio/Fe (II) mostraram uma banda que é característica do ferricianeto. Os espectros infravermelhos também mostraram neste produto de reação bandas características do tiocianato de guanidina. Portanto, o aquecimento do tiocianato de amônio com Fe (II) em estado sólido esta formando tiocianato de guanidina e ao mesmo tempo oxidando o Fe (II) para Fe (III). O produto da reação entre Fe (III) e tiocianato de amônio é o tiocianato de guanidina. O Fe (II) e o Fe (III) reagem de forma diferente com o tiocianato de amônio

Adsorption of glyphosate on clays and soils from Paraná State: effect of pH and competitive adsorption of phosphate

This work showed that the adsorption of glyphosate (GPS) depends on surface area for clays and amount of clays and CEC for soils. Organic matter (OM) had a secondary role in the adsorption of GPS on soils. The adsorption of GPS on soils from Londrina and Floraí counties and clays (montmorillonite, kaolinite) decreased when pH increased, however, for bentonite clay and soil from Tibagi county was kept constant. For the soils, the competitive adsorption between GPS and phosphate showed that displace of GPS by phosphate was related to the amount of clays, CEC and pH. GPS was not easily displaced by phosphate on the clays. The FT-IR spectra of the soils and clays showed that soil from Londrina resembled kaolinite. Thus, this could explain the results of adsorption of GPS and the competitive adsorption between GPS and phosphate.No presente trabalho foi mostrado que a adsorção de glifosato (GPS) depende da área superficial (argilas) e da quantidade de argilas e da CTC (solos). A matéria orgânica (MO) tem um papel secundário na adsorção do GPS sobre solos. A adsorção de GPS sobre os solos de Londrina e Florai e argilas (montimorilonita, caulinita) diminui com o aumento do pH e manteve-se constante para a bentonita e o solo de Tibagi. Para os solos estudados, a adsorção competitiva entre GPS e fosfato mostrou que o deslocamento do GPS pelo fosfato depende da quantidade de argilas, CTC e pH. O GPS não foi facilmente desorvido das argilas pelo fosfato. Os espectros IV-FT dos solos e argilas mostraram que o solo de Londrina e a caulinita são muito semelhantes. Portanto, isto poderia explicar os resultados de adsorção do GPS e da adsorção competitiva entre o GPS e o fosfato apresentarem resultados semelhantes

Desenvolvimento de um método para determinação de ácidos graxos em meios biológicos utilizando a espectroscopia no infravermelho com transformada de Fourier

No presente trabalho foi desenvolvida uma metodologia para a determinação de ácidos graxos em meios biológicos utilizando a espectroscopia no infravermelho com transformada de Fourier. Este método não precisa de reagente cromóforo ou pré-preparo da amostra. O ácido palmítico foi escolhido como padrão, pois é o ácido graxo encontrado em diversos meios biológicos. O espectro infravermelho do ácido palmítico mostrou duas bandas de absorção na região de 2852 e 2920 cm-1 devido ao estiramento CH. Os resultados mostraram que estas bandas seguem a lei de Beer-Lambert numa ampla faixa de concentração de ácido palmítico (14 a 257 mmol L-1). Como padrão interno foi utilizado o ferricianeto de potássio (K3[Fe(CN)6]). Diversos interferentes foram testados e somente o colesterol, o cloreto férrico (maior concentração), a mistura de aminoácidos para a banda em 2919 cm-1 (maior concentração) e o triacilglicerol mostraram-se interferentes ao método quando em concentração elevada. A nova metodologia, portanto, é vantajosa por ser de baixo custo e de fácil realização

Adenine interaction with and adsorption on Fe-ZSM-5 zeolites: A prebiotic chemistry study using different techniques

Most adsorption experiments are performed under conditions that did not exist on Earth before the life arose on it. Because adsorption is the first step for all other processes (protection against degradation and polymerization), it is important that it is performed under conditions that existed on prebiotic Earth. In this paper, we use an artificial seawater (seawater 4.0 Ga), which contains major cations and anions that could present on the oceans of the prebiotic Earth. In addition, zeolites, with substituted Fe in the framework, and adenine were probably common substances on the prebiotic Earth. Thus, study the interaction between them is an important issue in prebiotic chemistry. There are two main findings described in this paper. Firstly, zeolites with different Si/Fe ratios adsorbed adenine differently. Secondly, XAFS showed that, after treatments with seawater 4.0 Ga and adenine, an increase in the complexity of the system occurred. In general, salts of seawater 4.0 Ga did not affect the adsorption of adenine onto zeolites and adenine adsorbed less onto zeolites with iron isomorphically substituted. The C=C and NH2 groups of adenine interacted with the zeolites. Gypsum, formed from aqueous species dissolved in seawater 4.0 Ga, precipitated onto zeolites. EPR spectra of zeolites showed lines caused by Fe framework and Fe3+ species. TG curves of zeolites showed events caused by loss of water weakly bound to zeolite (in the 30-140 °C range), water bounded to iron species or cations from seawater 4.0 Ga or located in the cavities of zeolites (157-268 °C) and degradation of adenine adsorbed onto zeolites (360-600 °C). Mass loss follows almost the same order as the amount of adenine adsorbed onto zeolites. The XAFS spectrum showed that Fe3+ could be substituted into the framework of the Fe7-ZSM-5 zeolite