Acidic residue modifications restore chaperone activity of ß-casein interacting with lysozyme.

An important factor in medicine and related industries is the use of chaperones to reduce protein aggregation. Here we show that chaperone ability is induced in ß-casein by modification of its acidic residues using Woodward's Reagent K (WRK). Lysozyme at pH 7.2 was used as a target protein to study ß-casein chaperone activities. The mechanism for chaperone activity of the modified ß-casein was determined using UV-vis absorbencies, fluorescence spectroscopy, differential scanning calorimetry and theoretical calculations. Our results indicated that the ß-casein destabilizes the lysozyme and increases its aggregation rate. However, WRK-ring sulfonate anion modifications enhanced the hydrophobicity of ß-casein resulting in its altered net negative charge upon interactions with lysozyme. The reversible stability of lysozyme increased in the presence of WRK-modified ß-casein, and hence its aggregation rate decreased. These results demonstrate the enhanced chaperone activity of modified ß-casein and its protective effects on lysozyme refolding.

In situ biomimetic synthesis and characterization of nano hydroxyapatite in gelatin matrix.

In this work, nano hydroxyapatite (nHAp) composites were synthesized via an in situ biomimetic process at room temperature by using gelatin as a template agent. Formation of hydroxyapatite nanoparticles and the effect of biopolymer concentration on the shape and morphology of the nHAp nanoparticles were confirmed and investigated by using X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FT-IR), Scanning and Transmission Electron Microscopy (SEM and TEM). The results indicated that, the gelatin biopolymer as a template agent in the preparation batch has influences the size and morphology of the HAp nanocrystals precipitated in an aqueous solution of gelatin.

Biocompatibility evaluation of nano hydroxyapatite-starch biocomposites.

In this work, we report the synthesis and characterization of nano hydroxyapatite (nHAp) in the presence of starch matrix via a biomimetic process for in vitro biocompatibility evaluation. Characterization of the samples was carried out using X-ray diffraction (XRD) and Fourier Transform infrared spectroscopy (FT-IR). The Size and morphology of the nHAp samples were determined using scanning and transmission electron microscopy (SEM and TEM). The results show that, the shape and morphology of nHAp is influenced by the presence of starch as a template agent. It leads to formation of rod-like nHAp. Cell culture and MTT assays were performed for in vitro biocompatibility. They show that n-HAp can affect the proliferation of cells and the n-HAp/starch biocomposites have no negative effect on the cell morphology, viability and proliferation.

Preparation of core-shell ZnO-SiO2 nanowires-nanotubes for immobilization of the alkaline protease enzyme.

The main goal of enzyme immobilization is industrial re-use of enzymes for many reaction cycles. In this purpose, simplicity and improvement of the enzyme properties have to be strongly associated with the design of protocols of enzyme immobilization. In the last decade, nanosized materials have been widely used as a support for enzyme immobilization, for instance, silica nanotubes, phospholipid bilayers, self-assembled monolayers Langmuir_Blodgett films, polymer matrices, galleries of alpha-zirconium, phosphate, mesoporous silicates such as MCM-41, silica nanoparticles. In this work, we report synthesis of core shell ZnO/SiO2 nanowires and used them as a support for immobilization of the alkaline protease. Characterization of this assembled systems was carried out by, Energy-dispersive X-ray spectroscopy (EDAX), Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM). Biocatalytic activity of the alkaline protease in this bioconjugate system was examined and the results showed an increase of biocatalytic activity, in comparison with the free enzyme in solution.

The study of adsorption characteristics Cu2+ and Pb2+ ions onto PHEMA and P(MMA-HEMA) surfaces from aqueous single solution.

The adsorption characteristics of Cu2+ and Pb2+ ions onto poly2-hydroxyethyl methacrylate (PHEMA) and copolymer 2-hydroxyethyl methacrylate with monomer methyl methacrylate P(MMA-HEMA) adsorbent surfaces from aqueous single solution were investigated with respect to the changes in the pH of solution, adsorbent composition (changes in the weight percentage of MMA copolymerized with HEMA monomer), contact time and the temperature in the individual aqueous solutions. The linear correlation coefficients of Langmuir and Freundlich isotherms were obtained. The results revealed that the Langmuir isotherm fitted the experimental results better than the Freundlich isotherm. Using the Langmuir model equation, the monolayer adsorption capacity of PHEMA surface was found to be 0.840 and 3.037 mg/g for Cu2+ and Pb2+ ions and adsorption capacity of (PMMA-HEMA) was found to be 31.153 and 31.447 mg/g for Cu2+ and Pb2+ ions, respectively. Changes in the standard Gibbs free energy (DeltaG(0)), standard enthalpy (DeltaH(0)) and standard entropy (DeltaS(0)) show that the adsorption of mentioned ions onto PHEMA and P(MMA-HEMA) are spontaneous and exothermic at 293-323 K.

Biocatalytic activity of fungal protease on silver nanoparticle-loaded zeolite X microspheres.

Silver nanoparticles are excellent biocompatible surfaces for the immobilization of enzymes. However, separation of the silver nanoparticle-enzyme bioconjugate material from the reaction medium is often difficult. In this study, we investigate the assembly of the silver nanoparticles on the surface of the amine-functionalized zeolite microspheres or formation of zeolite-silver nanoparticle "core-shell" structure and thereafter, using obtained structure in immobilization of fungal protease. The assembly of silver nanoparticles on zeolite surface occurs through the amine groups present in 3-aminopropyltrimethoxysilane (3-APTS). The fungal proteases bound to the massive "core-shell" structures can be easily separated from the reaction medium by mild centrifugation and exhibited excellent reuse characteristics. The biocatalytic activity of fungal protease in the bioconjugate was marginally enhanced relative to the free enzyme in solution.

Study of the hydrogen bond in different orientations of adenine-thymine base pairs: an ab initio study.

In order to gain deeper insight into structure, charge distribution, and energies of A-T base pairs, we have performed quantum chemical ab initio and density functional calculations at the HF (Hartree-Fock) and B3LYP levels with 3-21G*, 6-31G*, 6-31G**, and 6-31++G** basis sets. The calculated donor-acceptor atom distances in the Watson-Crick A-T base pair are in good agreement with the experimental mean values obtained from an analysis of 21 high resolution DNA structures. In addition, for further correction of interaction energies between adenine and thymine, the basis set superposition error (BSSE) associated with the hydrogen bond energy has been computed via the counterpoise method using the individual bases as fragments. In the Watson-Crick A-T base pair there is a good agreement between theory and experimental results. The distances for (N2...H23-N19), (N8-H13...O24), and (C1...O18) are 2.84, 2.94, and 3.63 A, respectively, at B3LYP/6-31G** level, which is in good agreement with experimental results (2.82, 2.98, and 3.52 A). Interaction energy of the Watson-Crick A-T base pair is -13.90 and -10.24 kcal/mol at B3LYP/6-31G** and HF/6-31G** levels, respectively. The interaction energy of model (9) A-T base pair is larger than others, -18.28 and -17.26 kcal/mol, and for model (2) is the smallest value, -13.53 and -13.03 kcal/mol, at B3LYP/6-31G** and B3LYP/6-31++G** levels, respectively. The computed B3LYP/6-31G** bond enthalpies for Watson-Crick A-T pairs of -14.4 kcal/mol agree well with the experimental results of -12.1 kcal/mol deviating by as little as -2.3 kcal/mol. The BSSE of some cases is large (9.85 kcal/mol) and some is quite small (0.6 kcal/mol).

Reversible maps in two-degrees of freedom Hamiltonian systems.

It has been shown that a sub-class of two-degrees of freedom Hamiltonian systems possesses a reversing symmetry discovered by Birkhoff in the restricted problem of three bodies. This mixed space-time reversing symmetry, which is different from the classical time reversal symmetry, can be shared by time-reversible as well as time-irreversible systems. Examples of time-irreversible systems which possess this reversing symmetry are the restricted problem of three bodies as shown by Birkhoff in 1915, and a special case of the motion of a rigid body with a fixed point discussed in this paper. If a Hamiltonian system possesses this Birkhoff reversing symmetry, then there exists a surface of section for which the corresponding Poincare map is Birkhoff-reversible. The Birkhoff-reversibility of this map may be used to study its global dynamics such as the locations and the distribution of the stable and unstable periodic points, the distribution of stable and chaotic regions, and the identification of the scattering regions. (c) 2002 American Institute of Physics.

Order and chaos in the planar isosceles three-body problem.

The planar isosceles three-body problem has been reduced to a two-dimensional area preserving Poincare map f. Using certain symmetry properties of the underlying differential equations and numerical integration, we offer a global description of f in the case of three equal masses. This description, which is based on the mapping of areas, immediately leads to the existence of various types of motion such as capture-escape, permanent capture, ejection-collision, etc., and their corresponding measures in the map domain. Moreover, this technique readily allows one to distinguish between so-called "fast" and "chaotic" scattering. Although capture-escape is the subset with the highest measure, there exist two important distinct invariant subsets under f where the solutions neither are captured nor lead to escape. The first set is a Cantor set which has zero measure and it is the outcome of the fact that f acts similar to the Smale horseshoe map in part of the domain. On this subset the action of f is chaotic. The second subset is an invariant region with positive measure surrounding an elliptic fixed point. In this region f acts essentially as a perturbed twist mapping where the iterates of f for the points in a large subset move on invariant curves in an orderly manner. In an appendix we cast our results in the framework of the widely studied isosceles triple collision manifold. (c) 1998 American Institute of Physics.