ABSTRACT
This article describes the use of a cationized starch-based material as new ion-exchanger adsorbent for the removal of C.I. Acid Blue 25 (AB 25) from aqueous solutions. Batch adsorption studies concerning the effects of contact time, pH and temperature are presented and discussed. Adsorption experimental data showed that: (i) the process was uniform and rapid: adsorption of dye reached equilibrium in 50 min in the wide pH range of dye solutions; (ii) adsorption kinetics followed the pseudo-second order model; (iii) the Langmuir model yielded a much better fit than the Freundlich model for the dye concentration range under study; (iv) this adsorbent exhibited interesting adsorption capacities: on the basis of the Langmuir analysis, the maximum adsorption capacity was determined to be 322 mg of dye per gram of material at 25 degrees C; (v) the adsorption capacity decreased with increasing temperature; and (vi) the negative value of free energy change indicated the spontaneous nature of adsorption.
Subject(s)
Coloring Agents/chemistry , Water Pollutants, Chemical/isolation & purification , Water Purification/methods , Adsorption , Cations , Hydrogen-Ion Concentration , Ion Exchange , Kinetics , Models, Chemical , Solutions , Starch/chemistry , Starch/economics , Temperature , Thermodynamics , Time Factors , Water/chemistry , Water Pollutants, Chemical/chemistryABSTRACT
This article describes the adsorption of an anionic dye, namely C.I. Acid Blue 25 (AB 25), from aqueous solutions onto a cationized starch-based adsorbent. Temperature was varied to investigate its effect on the adsorption capacity. Equilibrium adsorption isotherms were measured for the single component system and the experimental data were analyzed by using Langmuir, Freundlich, Tempkin, Generalized, Redlich-Peterson, and Toth isotherm equations. Five error functions were used to determine the alternative single component parameters by non-linear regression due to the bias in using the correlation coefficient resulting from linearization. The error analysis showed that, compared with other models, the Langmuir model described best the dye adsorption data. Both linear regression method and non-linear error functions provided the best-fit to experimental data with the Langmuir model.
Subject(s)
Coloring Agents/analysis , Models, Chemical , Starch/chemistry , Water Pollutants, Chemical/analysis , Water Purification/methods , Adsorption , Kinetics , ThermodynamicsABSTRACT
Plasmid DNA (pUC19 and pBR322) was sequence-specifically, covalently labelled with Cy3 fluorophores using a newly synthesised N-adenosylaziridine cofactor and the DNA methyltransferase M.TaqI. The fluorescently labelled plasmids were used for transfection of mammalian cells and their intracellular distribution was visualised by epifluorescence and confocal fluorescence microscopy. Although these prokaryotic plasmids do not contain nuclear import sequences, translocation into the nuclei was observed.
Subject(s)
DNA Modification Methylases , Molecular Probe Techniques , Plasmids , Transfection , Active Transport, Cell Nucleus , Animals , Base Sequence , Carbocyanines , Cells, Cultured , Humans , Taq PolymeraseABSTRACT
PEA-15 is a small protein (15 kDa) that was first identified as an abundant phosphoprotein in brain astrocytes [Araujo et al., J Biol Chem 1993;268(8):5911-20], and subsequently shown to be widely expressed in different tissues and highly conserved among mammals [Estelles et al., J Biol Chem 1996;271(25):14800-6; Danziger et al., J Neurochem 1995;64(3):1016-25]. It is composed of a N-terminal death effector domain and a C-terminal tail of irregular structure. PEA-15 is regulated by multiple calcium-dependent phosphorylation pathways that account for its different forms: a non-phosphorylated form in equilibrium with a mono and a biphosphorylated variety. This already suggested that PEA-15 may play a major role in signal integration. Accordingly, it has been demonstrated to modulate signaling pathways that control apoptosis and cell proliferation. In particular, PEA-15 diverts astrocytes from TNFalpha-triggered apoptosis and regulates the actions of the ERK MAP kinase cascade by binding to ERK and altering its subcellular localization. The three-dimensional structure of PEA-15 has been modelized and recently determined using NMR spectroscopy, and may help to understand the various functions played by the protein through its molecular interactions.
