Tromethamine and dodecanol appear to be the major secondary metabolites of Streptomyces decoyicus M.

An isolate of Streptomyces decoyicus M* (code of the isolate) was identified by the sequencing of 16S rRNA gene. It was grown on solid media and secondary metabolites were extracted with n-butanol. The extract was dried and run in a sodium dodecyl sulphate-polyacrylamide gel (SDS-PAGE, 10%). Two main bands obtained were sliced and the metabolites were regained in n-butanol. These two samples were then identified by gas-chromatography-mass spectrometry (GC-MS), and Fourier-transform infrared spectroscopy (FT-IR). The results demonstrated that tromethamine- and 1-dodecanol were the main constituents (band 1: 61% and 17.7%; band 2: 41% and 54%, respectively). This finding maintained that the isolate of Streptomyces decoyicus produced high amounts tromethamine- and 1-dodecanol under the conditions investigated.

Interaction of curcumin in a drug delivery system including a composite with poly(lactic-co-glycolic acid) and montmorillonite: a density functional theory and molecular dynamics study.

Phytochemicals such as curcumin have great potential in cancer prevention and treatment. However, instability and low aqueous solubility of free curcumin weaken its anticancer potential. These undesirable problems can be avoided upon loading curcumin into nanoparticles containing biocompatible and biodegradable polymers such as poly lactic-co-glycolic acid (PLGA), liposomes or micelles. The interaction of drugs and release control can be further enhanced upon inclusion of clay minerals into the PLGA containing nanoparticles. Such nanoparticles offer a new way for cancer drug delivery systems. However, the role of the clay mineral in the resulting composite is not fully understood. Therefore, in this study, we carried out systematic adsorption studies of curcumin anticancer drug on montmorillonite (MMT) nanoparticles in the presence of amphiphilic polymer (PLGA) and in an aqueous environment to understand the contribution of the layered clay structure using cluster (B97-D), periodic DFT and molecular dynamics (MD) simulations in acidic and natural pH media. It has been found that MMT has high affinity towards either polymer or drug molecules especially due to vdW interactions. Furthermore, it has been observed that MMT facilitates the release of curcumin. Current findings suggest that a composite consisting of MMT and PLGA might be used to deliver the anticancer agent curcumin.

Understanding the role of ion interactions in soluble salt flotation with alkylammonium and alkylsulfate collectors.

There is anecdotal evidence for the significant effects of salt ions on the flotation separation of minerals using process water of high salt content. Examples include flotation of soluble salt minerals such as potash, trona and borax in brine solutions using alkylammonium and alkylsulfate collectors such as dodecylamine hydrochloride and sodium dodecylsulfate. Although some of the effects are expected, some do not seem to be encompassed by classical theories of colloid science. Several experimental and modeling techniques for determining solution viscosity, surface tension, bubble-particle attachment time, contact angle, and molecular dynamics simulation have been used to provide further information on air-solution and solid-solution interfacial phenomena, especially with respect to the interfacial water structure due to the presence of dissolved ions. In addition atomic force microscopy, and sum frequency generation vibrational spectroscopy have been used to provide further information on surface states. These studies indicate that the ion specificity effect is the most significant factor influencing flotation in brine solutions.

Water structure and its influence on the flotation of carbonate and bicarbonate salts.

Interfacial water structure is a most important parameter that influences the collector adsorption by salt minerals such as borax, potash and trona. According to previous studies, salts can be classified as water structure makers and water structure breakers. Water structure making and breaking properties of salt minerals in their saturated brine solutions are essential to explain their flotation behavior. In this work, water structure making-breaking studies in solutions of carbonate and bicarbonate salts (Na(2)CO(3), K(2)CO(3), NaHCO(3) and NH(4)HCO(3)) in 4 wt% D(2)O in H(2)O mixtures have been performed by FTIR analysis of the OD stretching band. This method reveals a microscopic picture of the water structure making/breaking character of the salts in terms of the hydrogen bonding between the water molecules in solution. The results from the vibrational spectroscopic studies demonstrate that carbonate salts (Na(2)CO(3) and K(2)CO(3)) act as strong structure makers, whereas bicarbonate salts (NaHCO(3) and NH(4)HCO(3)) act as weak structure makers. In addition, the changes in the OD band parameters of carbonate and bicarbonate salt solutions are in agreement with the viscosity characteristics of their solutions.

Effect of electrolyte on surface free energy components of feldspar minerals using thin-layer wicking method.

Application of the thin-layer wicking (TLW) technique on powdered minerals is useful for characterizing their surfaces. Albite (Na-feldspar) and orthoclase (K-feldspar) are feldspar minerals which are frequently found in the same matrix. Despite similarities in their physicochemical properties, separation of these minerals from each other by flotation is generally possible in the presence of monovalent salts such as NaCl. Both albite and orthoclase exhibit the same microflotation properties and rather close electrokinetic profiles in the absence of salt. In this study, contact angles of albite and orthoclase determined by the TLW technique yielded close values in the absence and presence of amine collector. While the calculated surface energies and their components determined using contact angle data reveal that the energy terms remain farther apart in the absence of the collector, the differences narrow down at collector concentrations where full flotation recoveries are obtained. However, the effect of addition of NaCl on contact angles and surface free energy components at constant amine concentration indicates that albite is significantly affected by salt addition, whereas orthoclase remains marginally affected. This interesting finding is explained on the basis of ion-exchange properties, the stability of the interface, flotation data, and zeta potential data in the presence of NaCl.

Modification of organo-zeolite surface for the removal of reactive azo dyes in fixed-bed reactors.

Modification of zeolite (clinoptilolite) surface with a quaternary amine, hexadecyl trimethyl ammonium bromide (HTAB), to improve the removal efficiency of reactive azo dyes in a zeolite fixed bed was investigated. A series of adsorption tests were conducted to find out the uptake of three types of reactive dyes, i.e. CI Reactive Black 5, Red 239 and Yellow 176. Each run consisted of modifying zeolite with HTAB in the column followed by removal of color from the modified zeolite bed. The breakthrough curves for modification process were constructed under different conditions by plotting the normalized effluent concentration (C/C(0)) versus time or bed volumes (BV). Optimization studies show that 3g/l of HTAB dosage at a flowrate of 0.025l/min showed the best performance. Examination of the dye removal under the optimum modification conditions reveals that the black dye gives the highest breakthrough point among the three dyes tested. This is ascribed to the hydrophobic/hydrophilic match of the zeolite surface with the dye molecule, which depends upon the way zeolite is modified with HTAB. Calculations of the HTAB coverage on zeolite surface indicate that a bilayer formation is the most viable packing that enables maximum removal of the dye.

Mesoporous mineral columns for color removal from aqueous solutions.

The removal efficiency of natural minerals (e.g., zeolite and sepiolite) from aqueous solutions of azo dyes was investigated. The adsorption of three types of reactive dyes, Black, Red, and Yellow dissolved in distilled and/or deionized water on zeolite and sepiolite have been performed using column adsorption experiments. Distilled water containing 50 mg/L dyestuff was used to identify the ability of natural mesoporous minerals and their modified forms. The adsorption results indicate that both natural sepiolite and zeolite have limited adsorption capacities of the reactive dyes but are substantially improved upon modifying their surfaces with quaternary amines (HTAB). The removal of Yellow dye showed an excellent performance in sepiolite column compared to that in zeolite column.

Uptake of aniline and nitrobenzene from aqueous solution by organo-zeolite.

Adsorption mechanisms of toxic non-ionic organic contaminants (NOCs), aniline and nitrobenzene, with natural-zeolite and organo-zeolite (OZ) were investigated in both batch and continuous systems. In batch tests, the adsorption capacity of aniline and nitrobenzene onto natural zeolite surface is very low or almost nil but becomes significant upon modifying the zeolite surface by hexadecyltrimethylammonium (HDTMA). A partitioning mechanism is proposed to be responsible for the adsorption of NOCs onto OZ. The effectiveness of the partitioning mechanism is directly connected with hydrophobic properties of the NOCs. The column tests were carried out as an indicator for continuous system. The breakthrough curves were constructed for OZ/NOC system and the adsorption capacity of NOCs onto OZ under the present conditions were determined as 2.36 and 3.25 mg per gram of OZ, for aniline and nitrobenzene, respectively. A schematic model is proposed to account for the adsorption of NOCs onto OZ.

Adsorption of cobalt from aqueous solutions onto sepiolite.

Adsorption of Co(II) ions from aqueous sepiolite suspensions has been systematically investigated as a function of several variables including activation conditions, solid to liquid ratio, pH and temperature. The results are analyzed to identify the mechanism of cobalt uptake by sepiolite. Both abstraction and real adsorption isotherms were constructed to isolate the precipitation of cobalt from the real adsorption. Also, for the first time a plausible correlation between the released Mg(II) ions from sepiolite matrix and those adsorbed Co(II) ions is made. A one to one ion exchange mechanism is found to describe the results. The data obtained from adsorption isotherms at different temperatures were fitted to various adsorption models to calculate thermodynamic quantities such as the free energy of adsorption, heat of adsorption and entropy of adsorption. The thermodynamic data indicate that Co(II) adsorption onto sepiolite is entropically driven and characterized by physical adsorption.

Adsorption mechanism of cationic surfactants onto acid- and heat-activated sepiolites.

Systematic adsorption tests were carried out to determine the uptake of typical quaternary amines, dodecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide and a primary amine, dodecylamine hydrochloride by sepiolite. Bottle adsorption tests conducted with untreated, acid- and heat-activated sepiolites exhibit two distinct regions. The first stage is characterized by low rate and governed through an ion exchange process between ammonium ions and magnesium ions in the octahedral sheet. The second stage is ascribed to a combination of chain-chain interactions through Van der Waals forces and ion exchange process. Despite several-fold increases in surface areas upon activation, surprisingly no improvement in adsorption is observed. The observed differences are explained on the basis of partial collapse of the sepiolite crystal structure, the removal of zeolitic and bound waters and modification of the pore size distribution of sepiolite upon treatments.

Interaction of pyridine derivatives with sepiolite.

In this study, the adsorption behavior of pyridine derivatives, i.e., 2-aminopyridine and 2,2'-bipyridyl, onto sepiolite, a natural clay mineral, has been investigated by bottle adsorption and IR spectroscopic techniques. The results indicate that 2-aminopyridine and 2,2'-bipyridyl molecules adsorb onto sepiolite through hydrogen bonding of the amino groups to the water molecules in the octahedral sheet and to the surface hydroxyls (Si-OH) in the tetrahedral sheet. These findings reveal that pyridine molecules not only adsorb onto the external surface of sepiolite but are also incorporated in its channels and tunnels with adsorption taking place at corners and/or edges, depending on the position of water molecules. A structural model is proposed to account for the orientation of pyridine derivatives in the sepiolite matrix.

The Significance of Interfacial Water Structure in Soluble Salt Flotation Systems.

Flotation of soluble salts with dodecyl amine hydrochloride (DAH) and sodium dodecyl sulfate (SDS) collectors has demonstrated that the interfacial water structure and hydration states of soluble salt surfaces together with the precipitation tendency of the corresponding collector salts are of considerable importance in explaining their flotation behavior. In particular, the high concentration of ions in these soluble salt brines and their hydration appear to modify the bulk and interfacial structure of water as revealed by contact angle measurements and this effect is shown to be an important feature in the flotation chemistry of soluble salt minerals including alkali halide and alkali oxyanion salts. Depending on characteristic chemical features (salt type), the salt can serve either as a structure maker, in which intermolecular hydrogen bonding between water molecules is facilitated, or as a structure breaker, in which intermolecular hydrogen bonding between water molecules is disrupted. For structure making salts the brine completely wets the salt surface and no contact angle can be measured. For structure breaking salts the brine does not completely wet the salt surface and a finite contact angle is measured. In this regard it has been found that soluble salt flotation either with the cationic DAH or anionic SDS collector is possible only if the salt is a structure breaker. Copyright 2001 Academic Press.

Whole-body microwave exposure emitted by cellular phones and testicular function of rats.

This study investigated whether there are adverse effects due to microwave exposure emitted by cellular phones in male rats. Eighteen Wistar Albino rats were separated into three groups, a sham group and two experimental groups. The rats were confined in Plexiglas cages and cellular phones were placed 0.5 cm under the cages. In the first experimental group, cellular phones were in standby position for 2 h. In the second experimental group, phones were turned to the speech position three times each for 1 min duration over 2 h. Rats in the first and second experimental groups were exposed to microwaves emitted by phones for 2 h/day for a duration of 1 month. After the last exposure the rats were killed. Brain, eyes, ears, liver, heart, lungs, stomach, kidneys, testes, small and large intestines and skin of the rats were observed histologically. The decrease of epididymal sperm counts in the speech groups were not found to be significant (P > 0.05). Differences in terms of normal and abnormal sperm forms were not observed (P > 0.05). Histological changes were especially observed in the testes of rats of the speech groups. Seminiferous tubular diameter of rat testes in the standby and speech groups was found to be lower than the sham group (P < 0.05). Rectal temperatures of rats in the speech group were found to be higher than the sham and standby groups (P < 0.05). The rectal temperatures of rats before and after exposure were also found to be significantly higher in the speech group (P < 0.05). Specific absorption rate (SAR) was determined as 0.141 W/kg.