Potentiometric studies on mixed-ligand complexes of cobalt(II) and nickel(II) with amino acids as primary ligands and imidazole as secondary ligand

Summary The formation constants of mixed-ligand complexes of cobalt(II) and nickel(II) with glycine, DL--alanine and DL-valine as primary ligands and imidazole as secondary ligand have been determined potentiometrically under physiological-like conditions (T=37°C and I=0.15 M KNO₃). The proton association constants of the free ligands and the stability constants for binary systems involving the amino acids and imidazole were also determined under identical conditions, and the experimental pH-titration data were analysed using the computer SUPERQUAD program. The relative stability of the ternary complex as compared to that of the corresponding binary complexes has been quantitatively expressed in terms of log K and log X values.     

Potentiometric studies on mixed-ligand complexes of copper(II) and zinc(II) with some amino acids (glycine,DL-α-alanine and DL-valine) as primary ligands and imidazole as a secondary ligand

Summary Mixed-ligand complexes of Cu^II and Zn^II with glycine(GL), DL--alanine (AL) and DL-valine (VL) as primary ligands and imidazole (IM) as secondary ligand have been studied potentiometrically under physiological conditions (t=37° C and I=0.15 M KNO₃). The experimental pH-titration data were analysed with aid of the SUPERQUAD computer program in order to evaluate formation constants of binary and ternary systems involying amino acids (AA) and IM. The relative stability of each of the ternary complexes was compared with that of corresponding binary complexes in terms of log K and log X values.     

MHD squeezing flow of second‐grade fluid between two parallel disks

This paper examines the unsteady two‐dimensional flow of a second‐grade fluid between parallel disks in the presence of an applied magnetic field. The continuity and momentum equations governing the unsteady two‐dimensional flow of a second‐grade fluid are reduced to a single differential equation through similarity transformations. The resulting differential system is computed by a homotopy analysis method. Graphical results are discussed for both suction and blowing cases. In addition, the derived results are compared with the homotopy perturbation solution in a viscous fluid (Math. Probl. Eng., DOI: 10.1155/2009/603916 ). Copyright © 2011 John Wiley & Sons, Ltd.     

Ring-opening reactions of oxetanes: A review of methodology development and synthetic applications

Ring-opening reactions of oxetanes yield important functionalized products depending upon the nature of nucleophiles as well as substitution pattern on the oxetane ring. Ring opening of oxetanes can be carried out under a variety of reaction conditions. In this review article, an up-to-date overview of major synthetic methodologies involved in the ring opening of oxetanes as well as their synthetic applications has been presented.     

Synthetic chemoselective rewiring of cell surfaces: generation of three-dimensional tissue structures

Proper cell-cell communication through physical contact is crucial for a range of fundamental biological processes including, cell proliferation, migration, differentiation, and apoptosis and for the correct function of organs and other multicellular tissues. The spatial and temporal arrangements of these cellular interactions in vivo are dynamic and lead to higher-order function that is extremely difficult to recapitulate in vitro. The development of three-dimensional (3D), in vitro model systems to investigate these complex, in vivo interconnectivities would generate novel methods to study the biochemical signaling of these processes, as well as provide platforms for tissue engineering technologies. Herein, we develop and employ a strategy to induce specific and stable cell-cell contacts in 3D through chemoselective cell-surface engineering based on liposome delivery and fusion to display bio-orthogonal functional groups from cell membranes. This strategy uses liposome fusion for the delivery of ketone or oxyamine groups to different populations of cells for subsequent cell assembly via oxime ligation. We demonstrate how this method can be used for several applications including, the delivery of reagents to cells for fluorescent labeling and cell-surface engineering, the formation of small, 3D spheroid cell assemblies, and the generation of large and dense, 3D multilayered tissue-like structures for tissue engineering applications.     

Mathematical analysis on MHD Prandtl‐Eyring nanofluid new mass flux conditions

A speculative investigation has been presented to explore the salient features of magnetohydrodynamic (MHD) Prandtl‐Eyring nanofluid over stretching surface. Effects of Navier slip and convective boundary conditions are included in flow configuration. The effects of higher order chemical reactions along with Nield conditions are assumed in the concentration of nanoparticles. The mathematical modelling of the said flow problem accomplished the nonlinear partial differential equations along with appropriate boundary conditions. The nondimensional form of governing problem is yielded with the aid of similarity variables. The pivotal physical quantities, ie, velocity, temperature, and concentration (in nondimensional form), within boundary layer region are computed with shooting technique. The physical significance of flow controlling parameters on velocity, temperature, and concentration is illustrated through graphs. Additionally, thermophysical aspects of fluid near stretching surface (wall friction factor, wall heat flux, and wall mass flux) are instantiated graphically. A comparison of the current solution with reported data is established to validate the accuracy of adapted procedure. It is observed that the current findings agree with existing data. This led to confidence on adapted numerical procedure.     

Synergistic microfluidic and electrochemical strategy to activate and pattern surfaces selectively with ligands and cells

We show a straightforward, flexible synergistic approach that combines microfluidics, electrochemistry, and a general immobilization strategy to activate regions of a substrate selectively for the precise immobilization of ligands and cells in patterns for a variety of cell-based assays and cell migration and cell adhesion studies. We develop microfluidic microchips to control the delivery of electrolyte solution to select regions of an electroactive hydroquinone SAM. Once an electrical potential is applied to the substrate, only the hydroquinone exposed to electrolyte solution within the microfluidic channels oxidizes to the corresponding quinone. The quinone form can then react chemoselectively with oxyamine-tethered ligands to pattern the surface. Therefore, this microfluidic/electrochemistry strategy selectively activates the surface for ligand patterning that exactly matches the channel design of the microfluidic channel. We demonstrate the ease of this system by first quantitatively characterizing the electrochemical activation and immobilization of ligands on the surface. Second, we immobilize a fluorescent dye to show the fidelity of the methodology, and third, we show the immobilization of biospecific cell adhesive peptide ligands to pattern cells. This is the first report that combines microfluidics/electrochemistry and a general electroactive immobilization strategy to pattern ligands and cells. We believe that this strategy will be of broad utility for applications ranging from fundamental studies of cell behavior to patterning molecules on a variety of materials for molecular electronic devices.