Volume 1, Issue 1, 2009

Structural Changes Associated with Interactions Between Starch and Particles of TiO2 or ZnSe
Paul Bernazzani, Hari Krishna Reddy Pandi, Vamshi Krishna Peyyavula

Abstract
The effects of modifying the structure of the starch chain on the kinetics of enzymatic cleavage are presented. The structural modifications involved interactions between the biopolymer chains and two types of transition metal particles: ZnSe, and TiO2. The structural changes were followed using Raman spectroscopy and differential scanning calorimetry (DSC) while the enzymatic activity was determined using the starch-iodine complexation method. Results show that interactions with ZnSe increase the rate of digestion while interactions with TiO2 significantly slow down the reaction. Structural analysis suggests that strain variations in the backbone are the driving forces behind the experimental observations. Full Article

Predictive Simulation for Separation of Toxic Metal Ions by Ion-Exchange Resins in Complex Media   Madjid Hadioui, Mohamed Oimar Mecherri, Zahia Harrache

Abstract
A calculation program based upon predictions was developed to foresee the separation conditions by ion exchange for two divalent metal ions often encountered together. The simulations were compared to experimental results obtained in similar conditions in complex media. Whilst the separation by batch method was found unlikely for these metals on Dowex-50-X8 resin in these conditions, our program shows that quantitative separation of these species in column is achieved by sequential elutions with chelating agent solution and the correlation with experimental verification applicable. The simulations described could be a didactic illustration for selective separation using these types of resins. Full Article


 

Reflections on the Secondary Structure of DNA and Other Biopolymers
Clive Delmonte

Abstract
In DNA fibers, humidity change alone is sufficient to effect various inter-conversions among the A, B, C, D and Z forms which must be closely similar in structure. Crystals of A-DNA and of B-DNA are claimed as right-handed and crystals of Z form oligodeoxyribonucleotides are
claimed as left-handed, and, by extension, Z-DNA fibers too. The B-Z transition is far faster when poly (d(G.5MeC)n)2 is wound around a core of nucleosomal proteins than when the polymer is free in solution, which remains unexplained. Z-A-Z and Z-B-Z transitions imply left-right-left changes in a double helix, with monotonic rises in salt concentration, all unexplained.
DNA transformations from double into triple stranded, plectonemically wound, helices inside solid fibers remain unexplained. This review explains the formation of triple stranded DNA inside fibers and the accelerated transformation of B- to Z-form polydeoxyribonucleotides wrapped around a core of nucleosomal proteins. Full Article

 

Development of lipoic acid activated agarose
C. Manta, F. Batista-Viera, J.Carlsson

Abstract
A new strategy for the preparation of activated supports containing oxidized lipoic acid (LA) is presented. An amino-agarose gel with low pKa (monoaminoethyl-N-aminoethyl-agarose) was highly substituted with a disulfide ligand (254 μmoles LA/g dried gel) which was subsequently oxidized to disulfide oxides. Oxidation carried out with H2O2 gave a support with a large binding

capacity for low molecular weight thiols, as demonstrated with glutathione (GSH), achieving 105 μmoles bound GSH per g dried gel. GSH binding was completely reversible under reducing condition. Protein immobilization was assayed with K. lactis b-galactosidase. However, although this protein bound readily to the LA-modified support, there was no release of the protein after reduction. We assume that different chemistry was involved in the case of the protein ligand, and this is briefly discussed. Full Article