KMnO4 chemical kinetics in high diluted solvents

Background: A number of theoretical and experimental approaches have been signalizing towards a induction of some solvent structural order or dynamical behavior, whenever a High Dilution (HD) is prepared. These works have been performed using different spectroscopic techniques, calorimetric studies, electrical and optical measurements, among others, which results are interpreted under many different approaches. The understanding of the physicochemical nature of HDs is still far from to be clarified, despite the evidences on their biological activity. Assuming that physicochemical changes induced by shaking and dilution (potentization) are true, one could expect that the changed solvent could interfere in the chemical kinetics of a complex reaction. The reduction of Mn7+ to Mn2+ (color change) observed when KMnO4 in transferred into an acidic solvent is a self-catalyzed reaction dependent on pH, temperature and concentration with many reaction pathways, but converging usually to the colorless Mn2+ state (the Mn2+ produced in the Mn7+ reduction is the reaction catalyzer). Method: We have performed this reaction using oxalic and sulphuric acid as solvent, observing the time dependence of the absorbance at λ = 525 nm. Some solvent variants were proofed: G0: normal solvent; G1: potentized solvent at 12x; G2: Mn2+ potentized in normal solvent until 12x. If the potentization itself could change the solvent, we would expect differences in G1 compared to G0. If some Mn2+ information were imprinted into the solvent due the potentization we would expect differences in G2 to G1 and G0. It was recorded 10 spectra for each solvent variant and the experiment was performed twice (different weeks), with different fresh starting solutions (KMnO4, acid solvent and variants). Averaged values and standart deviations were compared. Results: The only difference observed were a randomic time delay (few seconds) to start the decrease in the absorbance at λ = 525 nm. This delay was associated to the natural diffusion of KMnO4 in the solvent and the time left to insert the cuvette into the spectrometer as well to turn the measurements on. After delay correction, all curves showed similar behavior (unsignificant differences), that its typical decrease. Conclusion: If potentization is able to induce changes in the solvent, these were not able to affect the chemical kinetics of the KMnO4 in acidic medium. One could hypothetize this model is not responsive to those putative changes either by the unspecificity of a chemical solution (no similitude is achieved) or by the lack of a biological sensor able to interpret such changes. Another conclusion would be that no changes are induced on the solvent due potentization.

Effect of Cold Rolling on the Evolution of Shear Bands and Nanoindentation Hardness in Zr41.2Ti13.8Cu12.5Ni10Be22.5 Bulk Metallic Glass

The effect of cold rolling on the evolution of hardness (H) and Young’s modulus (E) on the rolling-width (RW), normal-rolling (NR), and normal-width (NW) planes in Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vitreloy 1) bulk metallic glass (BMG) was investigated systematically using nanoindentation at peak loads in the range of 50 mN–500 mN. The hardness at specimen surface varied with cold rolling percentage (%) and the variation is similar on RW and NR planes at all the different peak loads, whereas the same is insignificant for the core region of the specimen on the NW plane. Three-dimensional (3D) optical surface profilometry studies on the NR plane suggest that the shear band spacing decreases and shear band offset height increases with the increase of cold rolling extent. Meanwhile, the number of the pop-in events during loading for all the planes reduces with the increase of cold rolling extent pointing to more homogeneous deformation upon rolling. Calorimetric studies were performed to correlate the net free volume content and hardness in the differently cold rolled specimens.

Modified Carboxymethylcellulose-Based Scaffolds as New Potential Ecofriendly Superplasticizers with a Retardant Effect for Mortar: From the Synthesis to the Application

This article is focused on the research and development of new cellulose ether derivatives as innovative superplasticizers for mortar systems. Several synthetic strategies have been pursued to obtain new compounds to study their properties on cementitious systems as new bio-based additives. The new water-soluble admixtures were synthesized using a complex carboxymethylcellulose-based backbone that was first hydrolyzed and then sulfo-ethylated in the presence of sodium vinyl sulphonate. Starting with a complex biopolymer that is widely known as a thickening agent was very challenging. Only by varying the hydrolysis times and temperatures of the reactions was achieved the aimed goal. The obtained derivatives showed different molecular weight (Mw) and anionic charges on their backbones. An improvement in shear stress and dynamic viscosity values of CEM II 42.5R cement was observed with the samples obtained with a longer time of higher temperature hydrolysis and sulfo-ethylation. Investigations into the chemical nature of the pore solution, calorimetric studies and adsorption experiments clearly showed the ability of carboxymethyl cellulose superplasticizer (CMC SP) to interact with cement grains and influence hydration processes within a 48-h time window, causing a delay in hydration reactions in the samples. The fluidity of the cementitious matrices was ascertained through slump test and preliminary studies of mechanical and flexural strength of the hardened mortar formulated with the new ecological additives yielded values in terms of mechanical properties. Finally, the computed tomography (CT) images completed the investigation of the pore network structure of hardened specimens, highlighting their promising structure porosity.

Structural and calorimetric studies reveal specific determinants for the binding of a high-affinity NLS to mammalian importin-alpha

The classical nuclear import pathway is mediated by importin (Impα and Impβ), which recognizes the cargo protein by its Nuclear Localization Sequence (NLS). NLSs have been extensively studied resulting in different proposed consensus; however, recent studies showed that exceptions may occur. This mechanism may be also dependent on specific characteristics of different Impα. Aiming to better understand the importance of specific residues from consensus and adjacent regions of NLSs, we studied different mutations of a high affinity NLS complexed to Impα by crystallography and calorimetry. We showed that although the consensus sequence allows Lys or Arg residues at the second residue of a monopartite sequence, the presence of Arg is very important to its binding in major and minor sites of Impα. Mutations in the N or C-terminus (position P1 or P6) of the NLS drastically reduces their affinity to the receptor, which is corroborated by the loss of hydrogen bonds and hydrophobic interactions. Surprisingly, a mutation in the far N-terminus of the NLS led to an increase in the affinity for both binding sites, corroborated by the structure with an additional hydrogen bond. The binding of NLSs to the human variant Impα1 revealed that these are similar to those found in structures presented here. For human variant Impα3 the bindings are only relevant for the major site. This study increases understanding of specific issues sparsely addressed in previous studies that are important to the task of predicting NLSs, which will be relevant in the eventual design of synthetic NLSs.

A novel dextrin produced by the enzymatic reaction of 6-α-glucosyltransferase Ⅱ: Practical advantages of the novel dextrin as a food modifier

ABSTRACT High-molecular-weight dextrin (WS-1000) was produced from waxy corn starch and enzymatically modified to link glucose by α-1,6 glycosidic bond at the terminal point of the glucose chain, forming MWS-1000. In this study, the physical properties of MWS-1000 were characterized, and the advantages of its use as a food modifier were described. From rheological and calorimetric studies, it was found that MWS-1000 does not undergo retrogradation, but it does not prevent the retrogradation of WS-1000, suggesting that they have no intermolecular interaction in solution. Investigation of the effect of MWS-1000 on the viscoelasticity of gelatinized wheat starch showed that in the linear viscoelastic region, storage modulus decreased and tan δ increased with increase in replaced MWS-1000 content. In addition, it was confirmed that gelatinized starch containing MWS-1000 showed viscoelastic behavior similar to that of commercially available custard cream.