Nanoconfinement of water layers in lamellar structures prepared in the presence and absence of organic solvent.

An attempt is made to draw a line of comparison between the extent of rigidity of the hydration layers bound to the interfacial region of lamellar structures of Aerosol OT (AOT, sodium bis(2-ethylhexyl) sulfosuccinate) in water, in the presence and absence of an organic solvent using POM, SAXS, cryo-TEM, and time-resolved fluorescence spectroscopy. These systems are ternary mixtures of AOT, water, and n-heptane containing lamellar structures in an aqueous layer at higher w(0) values (w(0) = 300 and 150) and a binary solution of 20 and 50% AOT in neat water (w/w). The solvation shells residing at the vicinity of these lamellar structures are monitored using two different coumarin probes (C153 and C500).

Helix--rod transition in a nanospring.

A model of helical spring is described whose effective pitch and length are decided by the balance of the attractive van der Waals and repulsive hydration and electrical double layer forces. Also the electric contribution to the curvature free energy is taken into account. The stability of the nanospring is investigated and it is shown that the spring becomes unstable and jumps to its extended state on increase of electrostatic repulsion beyond a limit implying a jump in viscosity of suspension of springs in the solution.

An analysis of FtsZ assembly using small angle X-ray scattering and electron microscopy.

Small angle X-ray scattering (SAXS) was used for the first time to study the self-assembly of the bacterial cell division protein, FtsZ, with three different additives: calcium chloride, monosodium glutamate and DEAE-dextran hydrochloride in solution. The SAXS data were analyzed assuming a model form factor and also by a model-independent analysis using the pair distance distribution function. Transmission electron microscopy (TEM) was used for direct observation of the FtsZ filaments.

Catanionic surfactants as nanospring suspensions: a model.

A model for a dilute suspension of nanosprings, whose equilibrium configuration and extension are controlled by electrical double layer forces, is presented along with a model for changing packing parameter. The dependence of viscosity on surface charge is calculated. The possibility of shear-thickening is demonstrated.

A small-angle X-ray scattering study of the structure of lysozyme-sodium dodecyl sulfate complexes.

The structure of lysozyme-sodium dodecyl sulfate (SDS) complexes in solution is studied using small-angle X-ray scattering (SAXS). The SAXS data cannot be explained by the necklace and bead model for unfolded polypeptide chain interspersed with surfactant micelles. For the protein and surfactant concentrations used in the study, there is only marginal growth of SDS micelles as they complex with the protein.

Architecture of fiber network: from understanding to engineering of molecular gels.

A new approach of engineering of molecular gels was established on the basis of a nucleation-initiated network formation mechanism. A variety of gel network structures can be obtained by regulating the starting temperature of the sol-gel transition. This enables us to tune the network from the spherulitic domains pattern to the extensively interconnected fibrillar network.

Design of superior spider silk: from nanostructure to mechanical properties.

Spider dragline silk is of practical interest because of its excellent mechanical properties. However, the structure of this material is still largely unknown. In this article, we report what we believe is a new model of the hierarchical structure of silk based on scanning electron microscope and atomic force microscope images.

Formation of ordered arrays of oriented polyaniline nanoparticle nanorods.

We report the preparation of ordered polyaniline (PANI) nanorod arrays in an aqueous medium. The oriented PANI nanorods (80-400 nm in diameter and 8-15 mum in length) were synthesized in the presence of hydrophilic Allura Red AC (ARAC) as the structure-directing agent and ammonium persulfate as an oxidant in HCl solution. The morphologies of the oriented PANI nanoparticle nanorods were confirmed by scanning electron microscopy (SEM) and transmission electron microscopy images, and the effect of reaction conditions on the morphology of PANI nanostructures was also studied.

Topology evolution and gelation mechanism of agarose gel.

Kinetics as well as the evolution of the agarose gel topology is discussed, and the agarose gelation mechanism is identified. Aqueous high melting (HM) agarose solution (0.5% w/v) is used as the model system.

Colloidal phase transition driven by alternating electric field.

The transverse two-dimensional assembly of colloidal particles near an electrode surface subjected to ac polarization is studied by varying the frequency and field strength in the absence and presence of an added electrolyte. The variation of the translational and bond-orientational correlation functions with frequency suggests the existence of a hexatic phase in which the particles retain the remnants of the crystalline long-range orientational order, but has a liquidlike translational order. The electrohydrodynamic (EHD) flow is analyzed in the light of the existing theoretical models.

Gelation of aqueous pectin solutions: a dynamic light scattering study.

We report the dynamic light scattering study of the gelation of aqueous solutions of the biopolymer, pectin, induced by the addition of calcium chloride. The time correlation function data are analyzed under the framework of the coupling model. As the solution enters the semidilute regime where gelation sets in, the relaxation process shows a stretched exponential behavior.

Investigation on the mechanism of crystallization of soluble protein in the presence of nonionic surfactant.

The mechanism of crystallization of soluble, globular protein (lysozyme) in the presence of nonionic surfactant C8E4 (tetraoxyethylene glycol monooctyl ether) was examined using both static and dynamic light scattering. The interprotein interaction was found to be attractive in solution conditions that yielded crystals and repulsive in the noncrystallizing solution conditions. The validity of the second virial coefficient as a criterion for predicting protein crystallization could be established even in the presence of nonionic surfactants.

Protein interactions in undersaturated and supersaturated solutions: a study using light and x-ray scattering.

Protein interactions in undersaturated and supersaturated solutions were investigated using static and dynamic light scattering and small angle x-ray scattering. A morphodrom of lysozyme crystals determined at 35 degrees C and pH = 4.6 was used as a guideline in selecting the protein and precipitant concentrations.