Separation of 9,10-anthraquinone derivatives: evaluation of C18 stationary phases

Chromatographic study of natural products helps to determine their molecular composition and to identify their sources (biological, geographical, etc.). However, identifying anthraquinoids is still a challenge because this chemical family is composed of more than half a thousand molecules. In the present work, a series of C18 stationary phases were systematically studied to evaluate their separation potential for these compounds in high performance reversed phase liquid chromatography (RPLC). The stationary phases with various physicochemical properties were evaluated with respect to the separation of 30 standards. Selectivity of the studied stationary phases and symmetry of the obtained peaks were chosen as the evaluation criteria. Calculations of symmetry and separation capacity parameters have been proposed. These parameters are not dependent on the dimensions of the columns and were used for the classifications of phases. In conclusion, this study is intended to be a guide as to which stationary phases analysts can use for resolving separation of a complex mixture of anthraquinoids.     

Metabolomic study of plasma of patients with abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is an important health problem, both because of AAA rupture and death and because of increased cardiovascular mortality. Identification of new biomarkers of AAA may suggest novel pathological mechanisms and targets for new medical treatments to slow AAA progression. Metabolic changes in AAA patients were mainly related to carbohydrate and lipid metabolism and many of these changes can be associated with a situation of insulin resistance (which can be related to metabolic syndrome) together with altered amino acid metabolism. For the first time, metabolites that can be associated with differential metabolism by the gut microflora of AAA patients have also been found. Moreover, aminomalonic acid in plasma has been shown to be the metabolite with the biggest difference between patients suffering from large aneurysm (>5 cm) and controls.     

Asymmetric organocatalytic formation of protected and unprotected tetroses under potentially prebiotic conditions

Esters of proteinogenic amino acids efficiently catalyse the formation of erythrose and threose under potentially prebiotic conditions in the highest yields and enantioselectivities yet reported. Remarkably while esters of (L)-proline yield (L)-tetroses, esters of (L)-leucine, (L)-alanine and (L)-valine generate (D)-tetroses, offering the potential to account for the link between natural (L)-amino acids and natural (D)-sugars. The effect of pH and NaCl on the yields and enantioselectivities was also investigated and was shown to be significant, with the optimal enantioselectivities occurring at pH 7.     

A quantitative CE method to analyse tau protein isoforms using coated fused silica capillaries

We evaluated the potential of CE to analyse different isoforms of unphosphorylated recombinant tau protein and for separating one phosphorylated tau from the respective unphosphorylated protein. Different capillary coatings such as polyacrylamide, poly‐(ethylene oxide) and polybrene (PB) were evaluated to overcome the poor efficiencies obtained with fused‐silica capillary. Although peak asymmetry values were quite similar for the three investigated coatings, the peak efficiencies were 35‐fold and 5‐fold higher with PB coating than with polyacrylamide and poly(ethylene oxide) coatings, respectively. The recovery percentage (over 97%) was satisfactory and confirmed the efficacy of PB coating to limit the adsorption of tau protein to capillary walls. Moreover, PB coating produced higher repeatability for migration times (RSD values <1.2%) in comparison to the neutral coatings. The potential of PB‐modified capillary in producing high resolutive separations of one phosphorylated tau isoform from its unphosphorylated counterpart and of a mixture of phosphorylated and unphosphorylated tau peptides was demonstrated with 50 mM phosphate buffer pH 3.0. The separation of unphosphorylated tau isoform 352 (Tau‐352) from Tau‐352 phosphorylated in vitro by the mitogen‐activated protein kinase ERK2, was accomplished in less than 15 min.     

Using a multi-criteria decision aid methodology to implement sustainable development principles within an organization

The implementation of Sustainable Development (SD) within an Organization is a difficult task. This is due to the fact that it is difficult to deal with conflicting and incommensurable aspects such as environmental, economic and social dimensions. In this paper we have used a Multi-Criteria Decision Aid (MCDA) methodology to cope with these difficulties. MCDA methodology offers the opportunity to avoid monetary valuation of the different dimensions of the SD. These dimensions are not substitutable for one another and all have a role to play. There is an abundance of possible aggregation procedures in MCDA methodology. In this paper we have proposed an innovative method to choose a suitable aggregation procedure for SD problems. Real life case studies of the implementation of an outranking approach (i.e., ELECTRE) and of a mono-criterion synthesis approach (i.e., MAUT approaches based on the Choquet integral) were done to respectively rank 22 SD strategic actions within an expertise Institute and rank 20 practical operational actions to control energy consumption of the Institute’s buildings.     

Growth in the understanding of infinite numerical series: a glance through the Pirie and Kieren theory

In this paper, we describe the growth of mathematical understanding in university students engaged in mathematics classroom tasks regarding the concept of numerical series. Starting from the Image-Making Pirie and Kieren theory layer, students organize a mathematical concept linking different mathematical elements. In this process, there are important agents that are involved during the interactions to advance in this construction through the mechanism of folding back between different layers.     

Dithiocarbamates derived from aspartic and glutamic acids as chelating agents

Dithiocarbamates (dtc's) derived from aspartic (asp) and glutamic (glu) acids have been synthesized and characterized. Their Ba salts are of the general formula Ba₃(dtc–aa)₂, where aa = amino acid. The dithiocarbamates react with Ni^II salts to yield square-planar complexes, [Ni(dtc–aa)₂]. Complexes with Pb^II and Cd^II, with formula [M₃(dtc–aa)₂], are insoluble in water, and for Cd^II a second compound can be isolated in an acidic medium for the glutamic acid derivative, with formula [Cd(dtc–glu)]. Conductivity measurements indicate an appreciable affinity of the dithiocarbamates for these metal ions, with an almost quantitative scavenging ability.     

About a certain dynamical system in molecular configuration space

As an example of a dynamical system, glycine has been calculated through the molecular mechanics approach. Of the three planar conformations studied, only one equilibrium points region could be considered as a catchment region. On the other hand, an intriguing relation appears between the gradient norm and the spectral radius of the matrix representing the metric tensor.Part of a thesis for a master's degree in applied mathematics.     

Bond index: relation to second-order density matrix and charge fluctuations

It is shown that, in the same way as the atomic charge is an invariant built from the first-order density matrix, the closed-shell generalized bond index is an invariant associated with the second-order reduced density matrix. The active charge of an atom (sum of bond indices) is shown to be the sum of all density-density correlation functions between it and the other atoms in the molecule; similarly, the self-charge is the fluctuation of its total charge.On leave of absence from Depto. de Física e Química, UFES, 29000 Vitória, ES, Brasil     

Parallel supported synthesis of polyamine-imidazole conjugates

[reaction: see text] A small collection of nine polyamine-imidazole conjugates, potentially acting as RNases A mimics, has been synthesized on SynPhase lanterns using amino alcohols and diamines as building blocks. Couplings were performed via S(N)2 alkylation of methanesulfonates with amines. The final introduction of N-4-nitrobenzyloxycarbonyldiamines allowed easy purification of the cleaved compounds.