Aggregates In Water Solutions Research Articles

The dependence of 90Y sorption on nanodiamonds on sizes of their aggregates in water solutions

The dependence of 90Y sorption on nanodiamonds on sizes of their aggregates in water solutions

Water-Soluble Lanthanide-Titanium-Oxo Cluster, a Precursor for Biocompatible Nanomaterial.

Titanium-oxo clusters (TOCs) are attractive as a rapidly growing class of molecular materials due to their use as molecular models and precursors of nano-titanium-oxide. However, most TOCs can only be dissolved in nonaqueous solvents, which largely limits their potential applications in biological or environmental situations. Very few water-soluble TOCs were reported, which can be used directly in aqueous biomedical systems. However, until now, no research studies of such TOCs involved in biomedical fields have been documented. We report here a series of lanthanide-titanium-oxo clusters (LnTOCs) formulated as {H2@[Ln2Ti8(μ3-O)8(μ2-O)4(Ac)16]}3·24CH3CN·23H2O (Ln = Eu(III) 1, Tb(III) 2, and Yb(III) 3). The compounds are easily soluble in water and form a stable solution of the cluster aggregates (LnTOC-a). Therefore, nano-biocompatible TiO materals can be prepared from these LnTOCs just by dissolving them in water. The nanoscale aggregates in water solutions were characterized by SEI-MS, 1H NMR, XPS, IR, and EDS mapping. Using the EuTOC-a solution, excellent fluorescence sensor properties for biomolecule ascorbic acid were found. Furthermore, biocompatibility and fluorescent labeling properties of the EuTOC-a for HeLa cells were evaluated. The results indicated that water-soluble LnTOCs can be used to prepare biocompatible fluorescent Ln-Ti-O nanomaterials.

Imidazolium p-tert-Butylthiacalix[4]arene Amphiphiles—Aggregation in Water Solutions and Binding with Adenosine 5′-Triphosphate Dipotassium Salt

Aggregation properties of water-soluble cationic amphiphilic p-tert-butylthiacalix[4]arene derivatives adopting 1,3-alternate stereoisomeric form with methylimidazolyl headgroups were studied. It was found that derivatives 1 and 2 form stable aggregates in water solutions. The size and shape of aggregates were defined using DLS and TEM techniques. Critical aggregation concentration (CAC) of methylimidazolyl derivatives was calculated using dye micellization method. It was found that correct CAC determination of cationic amphiphiles using anionic xanthene dyes should be considered carefully in respect with electrostatic interactions. Using indicator displacement procedure, DLS studies, and 31P NMR spectroscopy, it was found that macrocycles 1 and 2 bind with ATP with 1:1 stoichiometry. It was found that ATP causes eosin Y release from binary thiacalixarene-eosin Y system up from 3 to 12 μM of ATP in the case of macrocycles 1 and 2, respectively.

Critical aggregates concentration of fatty esters present in biodiesel determined by turbidity and fluorescence.

Biodiesel for combustible engine is available as mixture of fossil diesel and fatty esters obtained by transesterification of vegetable oils. The use of biodiesel reduces the amount of SOx, mainly. However, it was already observed that biodiesel has a different behavior in environment in cases of accidental spill and groundwater contamination. It was noticed that the biodegradation of hydrocarbons (cyclic and aliphatic) in the presence of biodiesel are speeded, although the mechanism is still unclear. Considering the chemical structure of fatty esters, it was investigated the formation of aggregates in water solution by fatty esters present in commercial biodiesel. In Brazil, biodiesel is composed by 95% of fossil diesel and 5% of fatty esters mixture. In this work, fatty esters were treated as neutral surfactant, i.e., it was treated as a molecule with polar and non-polar part. Turbidity and fluorescence were used to determine the critical aggregates concentration (CAC). Water solutions containing fatty esters were examined exploiting changes in turbidity and fluorescence intensity of pyrene. Abrupt changes were attributed to aggregates formation, following the same behavior of traditional amphiphilic compounds. It was determined the CAC for ethyl palmitate, ethyl stearate, ethyl oleate, and ethyl linoleate. The values of CAC for fatty esters varied from 1.91 to 4.27μmol/L, while CAC for the mixture of esters (biodiesel) was 2.01 for methyl esters and 1.19 for ethyl esters, both prepared using soybean oil. The aggregates formation was also determined by fluorescence measurements considering the changes in intensity of peaks I and III of pyrene. Pyrene senses the changes in environment polarity. The values found of CAC by fluorescence for individual ethyl esters varied from 1.85 to 3.21μmol/L, while mixtures of ethyl esters was 2.23 and 2.07μmol/L for mixture of methyl esters. The results clearly showed that fatty esters form aggregates and might be responsible for speed degradation of compounds by accommodation of them in inner part of aggregates.

Alkaline hydrolysis of vinclozolin: Effect of humic acids aggregates in water

The influence of natural organic substances as humate colloidal aggregates in water solutions upon the chemical stability of vinclozolin has been investigated in basic media. A large inhibition (9 times-fold) has been observed and it has been rationalized in terms of a micellar pseudophase model. The observed behaviour could increase significantly the half-life of this fungicide. Moreover, these experimental results have been compared with the corresponding ones of other substances in these natural colloidal aggregates.

Stability study of Iprodione in alkaline media in the presence of humic acids

The influence of humic aggregates in water solution upon the chemical stability of Iprodione has been investigated under basic conditions. Taking into account that an important part of soils are colloids, the possibility of its presence implies that soil composition and its structure will play an important role in the stability of this pesticide. A kinetic model was applied to this system and the kinetic coefficients were obtained. An inhibition upon the alkaline hydrolysis of Iprodione (2-fold) was observed and it was rationalized in terms of the micellar pseudophase model. These results have been compared with the corresponding ones in the same natural colloidal aggregates in the presence of other pesticides.

Degradation of carbofuran and carbofuran-derivatives in presence of humic substances under basic conditions

The influence of humic aggregates in water solution upon the chemical stability of carbofuran (CF) and the carbofuran-derivatives, 3-hydroxy-carbofuran (HCF) and 3-keto-carbofuran (KCF), has been investigated in basic media. An inhibition upon the basic hydrolysis of 3-hydroxy-carbofuran and 3-keto-carbofuran (∼1.7 and ∼1.5-fold, respectively) was observed and it was rationalized in terms of the micellar pseudophase model. Nevertheless, non-significant effect upon the carbofuran stability was found in the presence of humic substances. These behaviors have been compared with the corresponding ones in other synthetic colloidal aggregates.

Abstract 1762: Highly potent anti-cancer ‘salan’ Titanium(IV) complexes: Structure - function relationship

Abstract Cisplatin is a widely used platinum-based metallo-chemotherapeutic drug that is considered an efficient treatment mainly for testicular and ovarian cancers. However, its narrow activity range and severe side effects trigger studies of other potent transition metal complexes. Two titanium(IV) anti-cancer agents that have been previously studied extensively as cisplatin alternatives are titanocene dichloride and budotitane. Despite their high activity, these complexes failed clinical trials mainly due to their poor water stability and formation of unidentified aggregates in water solutions. Our research group focuses on development of new, better-suited families of anti-tumor Ti(IV) complexes lacking Cp or diketonato ligands, and their investigation as anti-tumor agents. We recently reported the synthesis, characterization, and cytotoxicity of “salan” type Ti(IV) complexes [1]. The well defined hydrolytic behaviour, high stability, and high cytotoxicity of these compounds are strongly correlated to their particular structure. This enables fine tuning of complex properties by structural modifications. Herein we elaborate on the investigation of these salan titanium(IV) compounds. The correlation between the complex properties: structure, hydrolytic stability and cytotoxicity will be discussed, revealing insights on the biological mechanism of their cytotoxicity, suggesting an apoptotic cell death pathway.Additionally, further biological evaluation is presented, evincing that these compounds are markedly more active than cisplatin towards human and murine cancer-derived cell lines, including colon, ovarian, lung, cervix, pancreas, leukaemia, skin and breast, with activity also against cisplatin-resistant and multi-drug-resistant cells, and with minor effect on primary murine cells. In vivo experiments are now under way to determine both safety, as well as the anti-cancer activity of these complexes. [1] D. Peri, S. Meker, C. M. Manna, E. Y. Tshuva, Inorg. Chem., 2011, 50, 1030. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1762. doi:1538-7445.AM2012-1762

Supramolecular assemblies of rifampicin and cationic bilayers: preparation, characterization and micobactericidal activity

BackgroundCationic bilayers based on the inexpensive synthetic lipid dioctadecyldimethylammonium bromide (DODAB) have been useful as carriers for drug delivery, immunoadjuvants for vaccines and active antimicrobial agents.MethodsRifampicin (RIF) or isoniazid (ISO) interacted with DODAB bilayer fragments (BF) or large vesicles (LV). Dispersions were evaluated by dynamic light-scattering for zeta-average diameter (Dz) and zeta-potential (ζ) analysis; dialysis for determination of drug entrapment efficiency; plating and CFU counting for determination of cell viability of Mycobacterium smegmatis or tuberculosis, minimal bactericidal concentration (MBC) and synergism index for DODAB/drug combinations.ResultsDODAB alone killed micobacteria over a range of micromolar concentrations. RIF aggregates in water solution were solubilised by DODAB BF. RIF was incorporated in DODAB bilayers at high percentiles in contrast to the leaky behavior of ISO. Combination DODAB/RIF yielded MBCs of 2/2 and 4/0.007 μg/mL against Mycobacterium smegmatis or Mycobacterium tuberculosis, respectively. Synergism indexes equal to 0.5 or 1.0, indicated synergism against the former and independent action, against the latter species.ConclusionsIn vitro, DODAB acted effectively both as micobactericidal agent and carrier for rifampicin. The novel assemblies at reduced doses may become valuable against tuberculosis.

Synthesis and solution rheology of poly[(stearyl methacrylate)-stat-([2-(methacryloyloxy)ethyl] trimethyl ammonium iodide)

Poly([stearyl methacrylate]-stat-[2-(dimethylamino) ethyl methacrylate]) was synthesised through radical polymerisation using 1,1-diphenyl ethylene (DPE) as a molecular weight controlling agent. The amino groups were further quaternised into a cationic form in order to increase water solubility. Solubility of the polymers in water and a mixed solvent was studied with rotational rheometry. The resulting poly[(stearyl methacrylate)-stat-([2-(methacryloyloxy)ethyl] trimethyl ammonium iodide)] was soluble in water when the amount of stearyl methacrylate (SMA) in the polymer was less than 17 mol%. At higher SMA content, solubility strongly decreased but could be improved by using an organic co-solvent. Viscosity of the SMA-based statistical co-polymers is strongly dependent on polymer composition but solvent quality also has an influence, and the fluidic character can be either Newtonian or shear-thinning, or a weak gel can be formed. Concentration dependence behaviour deviates from that of typical polyelectrolytes. SMA polymers retain low viscosity up to rather high concentrations, but above a certain limiting concentration, the viscosity rapidly increases. This phenomenon is stronger with a higher amount of hydrophobic side-chain. At high co-polymer concentrations no entanglement formation was observed, and rheological behaviour indicates that SMA segments form aggregates in water solution.

Exciton relaxation in nanotubular TPPS 4 aggregates in water solution and in polymeric matrix

Exciton properties in meso-Tetra(4-sulphonatophenyl)porphine (TPPS 4) aggregates in water solution and in PVA matrix were investigated at different temperatures by means of transient absorption and fluorescence spectroscopy. Analysis of the steady state and transient absorption spectra shows that excitons delocalized over about 10 TPPS molecules are formed under the aggregate excitation to the higher energy absorption band, however they localize on one or two molecules after relaxation to the lowest energy excited state. The transient absorption and time resolved fluorescence show different relaxation kinetics, which is interpreted in terms of competition between the exciton relaxation to the nonradiative state and quenching by the quenching centers reached during thermally activated exciton diffusion. Exciton–exciton annihilation starts at high excitation intensity when more than 1 exciton per 20 molecules is created indicating that excitations visit about 20 molecules during their lifetime. The exciton relaxation becomes faster in optically annealed samples, when optically destroyed molecules create additional quenching centers.

Brightness of Yellow Fluorescent Protein from Coral (zFP538) Depends on Aggregation

The yellow fluorescent protein from coral (zFP538) forms aggregates in water solutions. According to dynamic light scattering and gel filtration data, the aggregation number is approximately 1000-10000 at pH 8-9 and protein concentration 1 mg/mL. Gel filtration demonstrated that dissociation of the aggregates takes place upon dilution, and the molecular weight of the aggregates decreases with pH. Atomic force microscopy (AFM) and near-field scanning optical microscopy (NSOM) were used to obtain images of zFP538 in the solid state. It was shown that protein films are comprised of fluorescent ellipsoidal granules with a 50-300 nm major axis and a 30-130 nm minor axis. The dependence of zFP538 fluorescence on protein concentration between 1.2 x 10(-)(9) and 5.5 x 10(-)(7) M can be divided in two linear regions with different slopes indicating the existence of at least two different forms of zFP538. The fluorescence of zFP538 decreases with time upon acidification, and the decrease depends on pH and protein concentration. Between pH 3.5 and pH 5.5, relative residual fluorescence is higher for concentrated zFP538 solutions (about 10(-)(6) M) as compared with diluted ones (10(-)(7) M and below). Aggregation makes zFP538 more stable against fluorescence quenching upon acidification: the decrease in zFP538 fluorescence at protein concentration 1 mg/mL is completely reversible, unlike that observed for less concentrated solutions. This phenomenon may be due to the decrease in the freedom of chromophore mobility in zFP538 aggregates.

Effect of Arm Length on the Aggregation Structure of Fullerene-Based Star Ionomers

Using small angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS), we have studied aqueous solutions of a fullerene-based star ionomer−hexa(sulfobutoxypentylcarboxy)[60]fullerene (FC10S). With six sulfobutoxypentyl arms randomly bounded on the C60 cage, FC10S demonstrates a good solubility in water. The scattering results show that the water-soluble fullerene-based ionomers of a starlike molecular morphology form rodlike aggregates in water solutions. With the contrast provided by SAXS and SANS, we extract detailed structural information for the rodlike aggregates, including arm distribution, aggregation number ∼ 32, and the rod radius and length of 21 Å and 160 Å, respectively. We also extract an averaged ionization factor of ∼ 0.03 for the FC10S aggregates, using the structural factor derived from the mean spherical approximation model for the charge interacting aggregates. The aggregation structure changes little within the concentration range studied (0.5−4%). Compared to the aggregation characteristics of FC4S, a similar fullerene-based ionomer with six shorter sulfobutyl arms, FC10S, has a much higher aggregation tendency due to the longer sulfobutoxypentyl arms anchored on the C60 cage.

Structure of sodium 4-(1-pentylheptyl)benzenesulphonate aggregates in water solutions by small angle X-ray scattering

The formation of oblate micelles, vesicles, and very flexible bilayers in the region of the phase diagram between micellar and lamellar phase of the binary double-chain ionic surfactant Sodium 4-(1-pentylheptyl) benzenesulphonate/water system was observed. Small angle X-ray scattering (SAXS) with Kratky Compact Camera, and in addition, freeze-fracture transmission electron microscopy (FFTEM), for the determination of the shape and size of particles were used. The maximum dimensions of oblate micelles determined by SAXS were found to be 10–12 nm what corresponds to 12–16 nm from FFTEM images. The axial ratio of the oblate micelles is about 2:1.

Mixtures of Ascorbyl-stearate and Vitamin D3: A Monolayer Study at the Gas/Water Interface

Vitamin C and vitamin D3perform different and important activities in living systems. Vitamin D3forms stable monomolecular films at the gas/water interface and, at higher concentrations, produces large aggregates in water solutions. Because of their amphiphilic structure, vitamin C alkyl esters form monolayers, micelles, vesicles, or microemulsions in water, depending on composition, concentration, solvent, and temperature. In this work the monolayer of 6-O-ascorbyl-stearate and vitamin D3was studied to investigate the behavior of the two compounds and their mixtures at the gas/water interface at different temperatures, at different pH, and in the presence of Ca2+in the subphase. The results show that stable Langmuir films are formed in all molar ratios, with repulsive interactions between the two components, and that the presence of calcium ions modifies the properties of the monolayer.

Molecular association of cryptand 221D in NaCl-water solutions. A small-angle neutron scattering study

Molecules of 5-Decyl-4,7,13,16,21-pentaoxa-1,10-diaza-bicyclo-[8.8.5]tricosan (221D) and its sodium complex, with both a hydrophobic and a hydrophilic portion, are expected to form aggregates in water solutions. This was confirmed by surface tension measurements. The aggregation behaviour was studied by small-angle neutron scattering at two different [NaCl]/[221D] molar ratios, such as to obtain, in one case, aggregates entirely made up of ionic monomers, and in the other, mixed micelles constituted by both ionic and non-ionic units. The variation of the aggregation number and number of aggregates indicated that, in the former case, smaller micelles were formed, as a consequence of repulsion among the ionic head groups

Growth of fractal aggregates in water solutions of macromolecules by light scattering.

We present experimental results showing that such macromolecules as bovine serum albumin (BSA) and deoxyribonucleic acid (DNA) in water solutions build aggregates of fractal structure. We use light scattering techniques, including dynamic (light-beating spectroscopy) and static (intensity) measurements. The BSA results show a behavior similar to that of polystyrene solutions, while for DNA we have observed a restructuring process analogous to those occurring in colloidal silica and gold aggregates.

Fatty acids in M and N blood group substances.

THE M and N blood group substances, obtained from human erythrocytes by phenol–water extraction, have been shown to be glycoproteins1. They are polydisperse in the ultracentrifuge and have an average molecular weight of 5 × 105–106 (ref. 1). Morawiecki found that M and N mucoids were dissociated by detergents into uniform sub-units of molecular weight 30,000 (ref. 2), and suggested that the sub-units were kept in aggregates in water solution by hydrophobic bonds. The formation of hydrophobic bonds could be explained by an assymmetric distribution of the hydrophilic oligosaccharide side chains over the polypeptide “backbone”. Products of proteolytic degradation of M and N substances were known to be easily separated into two fractions, distinctly different in the content of sugar components3. Further proof of an assymmetric distribution of sugars in M and N mucoids was provided by the formation of the precipitate when treated with pronase4. The precipitate, containing many fewer sugar components than soluble glycopeptides, was probably formed from the more hydrophobic central part of the micelles.