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Hydrophilic Regions (hydrophilic + regions)

Distribution by Scientific Domains

Polymers and Materials Science	33%
Chemistry	33%
Life Sciences	22%

Selected Abstracts

Self-Assembly and Micropatterning of Spherical-Particle Assemblies,

ADVANCED MATERIALS, Issue 7 2005
Y. Masuda
Spherical-particle assemblies (see Figure) are fabricated by micropatterning of methanol droplets containing SiO2. Hydrophilic regions of a patterned self-assembled monolayer (SAM) are covered with methanol solution containing SiO2 particles and immersed in decahydronaphthalene. The particles assemble to form micropatterns of spherical-particle assemblies on the hydrophilic regions of the SAM. [source]

Hexaquacobalt(II) bis(5-hydroxy-7-methoxy-4-oxo-2-phenyl-4H -chromene-6-sulfonate) tetrahydrate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2008
Wu-Wu Li
The title compound, [Co(H2O)6](C16H11O7S)2·4H2O, with cobalt(II) at the centre of symmetry, exhibits alternating hydrophilic and hydrophobic regions. Hydrophilic regions are generated by O,H...O hydrogen bonds among sulfonate groups, involving solvent water molecules and coordinated water molecules; ,,, stacking interactions assemble the flavone skeletons into columns which form the hydrophobic regions. A three-dimensional network is built up from an extensive array of hydrogen bonds, ,,, stacking interactions and electrostatic interactions between the cation and anion. As a salt of the sulfonated derivative of naturally occurring tectochrysin (5-hydroxy-7-methoxyflavone), this compound offers enhanced solubility and potential biological activity over the natural product. [source]

Binding of ciprofloxacin by humic substances: A molecular dynamics study

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2010
Ludmilla Aristilde
Abstract A comprehensive assessment of the potential impacts of antimicrobials released into the environment requires an understanding of their sequestration by natural particles. Of particular interest are the strong interactions of antimicrobials with natural organic matter (NOM), which are believed to reduce their bioavailability, retard their abiotic and biotic degradation, and facilitate their persistence in soils and aquatic sediments. Molecular dynamics (MD) relaxation studies of a widely used fluoroquinolone antibiotic, ciprofloxacin (Cipro), interacting with a model humic substance (HS) in a hydrated environment, were performed to elucidate the mechanisms of these interactions. Specifically, a zwitterionic Cipro molecule, the predominant species at circumneutral pH, was reacted either with protonated HS or deprotonated HS bearing Ca, Mg, or Fe(II) cations. The HS underwent conformational changes through rearrangements of its hydrophobic and hydrophilic regions and disruption of its intramolecular H-bonds to facilitate favorable intermolecular H-bonding interactions with Cipro. Complexation of the metal cations with HS carboxylates appeared to impede binding of the positively charged amino group of Cipro with these negatively charged HS complexation sites. On the other hand, an outer-sphere complex between Cipro and the HS-bound cation led to ternary Cipro,metal,HS complexes in the case of Mg,HS and Fe(II),HS, but no such bridging interaction occurred with Ca,HS. The results suggested that the ionic potential (valence/ionic radius) of the divalent cation may be a determining factor in the formation of the ternary complex, with high ionic potential favoring the bridging interaction. Environ. Toxicol. Chem. 2010;29:90,98. © 2009 SETAC [source]

Lanthanide-Based Conjugates as Polyvalent Probes for Biological Labeling

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2008
Stéphanie Claudel-Gillet
Abstract A series of lanthanide complexes of [LnL(H2O)] composition, suitable for biological labeling has been studied, in which L is a strongly chelating ligand containing chromophoric bipyridylcarboxylate units and Ln = Sm, Eu, Gd, Tb, and Dy. For the Gd complex, a combined 17O NMR and 1H NMRD study has been performed. The water exchange rate obtained, kex298 = (5.2,±,0.6),×,106 s,1, is slightly higher than those for [Gd(dota)(H2O)], or [Gd(dtpa)(H2O)]2,. Transformation of the uncoordinated carboxylate function of the ligand into an activated ester ensures covalent linking of the complex to bovine serum albumine (BSA). The relaxivity properties of the Gd complex labeled on BSA revealed a limited increase of both longitudinal and transversal relaxivities. This can be related to the partial replacement of the inner-sphere water molecules by coordinating functions of the protein. Additionally, the Sm and Dy complexes are described and chemically characterized. Their photophysical properties were investigated by means of absorption, steady-state and time-resolved spectroscopy, evidencing efficient photosensitization of the lanthanide emission by ligand excitation (antenna effect). Luminescence lifetime measurements confirmed the presence of a water molecule in the first coordination sphere that partly explained the relatively poor luminescence properties of the Dy and Sm complexes in aqueous solutions. The spectroscopic properties of the series of complexes are questioned in terms of time-resolved acquisition techniques. Finally, their availability for use in time-resolved luminescence microscopy is demonstrated by staining experiments of rat brain slices, where the complex showed enhanced localization in some hydrophilic regions of the blood,brain barrier (BBB).(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Self-Assembly and Micropatterning of Spherical-Particle Assemblies,

Detection of the Sm31 antigen in sera of Schistosoma mansoni, infected patients from a low endemic area

PARASITE IMMUNOLOGY, Issue 1 2010
G. S. SULBARÁN
Summary Schistosoma mansoni cathepsin B (Sm31) is a major antigen from adult worms that circulates in the blood of infected patients (Li et al., Parasitol Res 1996; 82: 14,18). An analysis of the Sm31 sequence (Klinkert et al., Mol Biochem Parasitol 1989; 33: 113,122) allowed the prediction of seven hydrophilic regions that were confirmed to be exposed on the surface of a 3D model of Sm31; the species specificity of these regions was checked using BLAST analysis. The corresponding peptides were chemically synthesized in polymerazible forms using the t-Boc technique. Rabbits developed a high humoral response against these peptides as tested by a multiple antigen blot assay; it recognized native Sm31 in crude S. mansoni extracts and as circulating antigen in sera of S. mansoni-infected patients by western blot. Relevant antigenic determinants were located at the N- and C-terminus sequences. Antibodies against these regions recognized the native enzyme in an ELISA-like assay called cysteine protease immuno assay in which the immunocaptured enzyme was revealed by the intrinsic cathepsin B hydrolytic activity of Sm31. The method successfully and specifically detected Sm31 in sera of infected individuals, most of them (83·3%) with light infections, offering a rationale for the development of parasite enzyme capture assays using anti-synthetic peptide antibodies for possible use in the diagnosis of schistoso,iasis. [source]

Surface topography and surface chemistry of radiation-patterned P(tBuMA),analysis by atomic force microscopy

POLYMER INTERNATIONAL, Issue 9 2003
Gregory S Watson
Abstract Poly-(tert -butyl methacrylate) (P(tBuMA)) thin-film surfaces were patterned by UV radiation at doses in the range 10,100 mJ cm,2, in order to induce laterally differentiated surface chemistry with µm resolution. The most likely pathway for the radiation chemistry predicts a transition from hydrophobicity to hydrophilicity. Outcomes of analysis by atomic force microscopy under air ambient conditions were consistent with that prediction. Topographic and lateral force imaging, in combination with friction loop analysis, revealed shrinkage and increased friction arising from exposure. Force versus distance analysis revealed greater adhesion in hydrophilic regions, due to greater meniscus force acting on the tip. The thickness of adsorbed moisture, increased by a factor of 2.5 from ca 0.8 nm for the unirradiated surface, as a result of greater hydrophilicity induced by radiation. The latter observation shows that the increased friction was due principally to the greater normal force on the tip from an additional meniscus force. Copyright © 2003 Society of Chemical Industry [source]

Surface-directed assembly of cell-laden microgels,,

BIOTECHNOLOGY & BIOENGINEERING, Issue 3 2010
Yanan Du
Abstract Cell-laden microscale hydrogels (microgels) can be used as tissue building blocks and assembled to create 3D tissue constructs with well-defined microarchitecture. In this article, we present a bottom-up approach to achieve microgel assembly on a patterned surface. Driven by surface tension, the hydrophilic microgels can be assembled into well-defined shapes on a glass surface patterned with hydrophobic and hydrophilic regions. We found that the cuboidic microgels (,100,200,µm in width) could self-assemble into defined shapes with high fidelity to the surface patterns. The microgel assembly process was improved by increasing the hydrophilicity of the microgels and reducing the surface tension of the surrounding solution. The assembled microgels were stabilized by a secondary crosslinking step. Assembled microgels containing cells stained with different dyes were fabricated to demonstrate the application of this approach for engineering microscale tissue constructs containing multiple cell types. This bottom-up approach enables rapid fabrication of cell-laden microgel assemblies with pre-defined geometrical and biological features, which is easily scalable and can be potentially used in microscale tissue engineering applications. Biotechnol. Bioeng. 2010; 105: 655,662. © 2009 Wiley Periodicals, Inc. [source]

Synthesis, Surface Modifications, and Size-Sorting of Mixed Nickel,Zinc Ferrite Colloidal Magnetic Nanoparticles

CHEMISTRY - A EUROPEAN JOURNAL, Issue 26 2008
P. Majewski
Abstract We report on the spontaneous covalent growth of monomolecular adlayers on mixed nickel,zinc nanoferrite colloidal suspensions (ferrofluids). Synthesized nanoparticles were subjected to surface modification by means of acid chloride chemistry, leading to the formation of covalent bonds between the hydroxy groups at the nanoparticle surface and the acid chloride molecules. This procedure can be easily tailored to allow for the formation of adlayers containing both hydrophobic and hydrophilic regions stacked at predetermined distances from the magnetic core, and also providing the nanoferrites with functional carboxy groups capable of further modifications with, for example, drug molecules. Here, fluorophore aminopyrene molecules were bound to such modified nanoferrites through amide bonds. We also used the same chemistry to modify the surface with covalently bound long-chain palmitoyl moieties, and for comparison we also modified the nanoferrite surface by simple adsorption of oleic acid. Both procedures made the surface highly hydrophobic. These hydrophobic colloids were subsequently spread on an aqueous surface to form Langmuir monolayers with different characteristics. Moreover, since uniformity of size is crucial in a number of applications, we propose an efficient way of sorting the magnetic nanoparticles by size in their colloidal suspension. The suspension is centrifuged at increasing rotational speed and the fractions are collected after each run. The mean size of nanoferrite in each fraction was measured by the powder X-ray diffraction (PXRD) technique. [source]