Extraction, Purification and Electrical Characterization of Gross Galactomannan and Purified Galactomannan Obtained from Adenanthera pavonina L. Seeds.

Aiming of self-sustainable production, the search for biodegradable and biocompatible materials has brought with it the need to know the physicochemical and dielectric characteristics of polysaccharide-based composite structures, which can be used as important and promising raw materials for biotechnology and electronic industries. Galactomannans are polysaccharides, extracted from seeds and microbiological sources, consisting of mannose and galactose. In this context, this work aimed to extract, purify and characterize by XRD, FTIR and impedance spectroscopy galactomannan obtained from seeds of Adenanthera pavonina L. The purification process was made with ethyl alcohol at concentrations of 70, 80 and 90 %. Polymeric films were prepared by solvent slow evaporation at low temperatures. XRD measurements revealed that Galactomannan from Adenanthera pavonina L., after purification, has a semi-crystalline structure due to the identification of two peaks the first between 5.849° and 6.118° and the second between 20.011° and 20.247°. FTIR spectra showed the functional groups associated with monosaccharides of the galactomannan from Adenanthera pavonina L. seeds, as well as the typical polysaccharide bands and peaks, confirmed by literature data. The impedance results give an increment on the state-of-the-art of this biomaterial by showing the existence of dielectric relaxations, independent of the degree of purification, using the dielectric modulus formalism. The permittivity analysis reveals the presence of water in the structure of the film, whose dipoles contribute to the relatively high value of the dielectric constant. From the results obtained, it can be concluded that purified galactomannan has the potential for possible applications in the electronics industry as a green and eco-friendly dielectric material.

Functional and evolutionary characterization of Ohr proteins in eukaryotes reveals many active homologs among pathogenic fungi.

Ohr and OsmC proteins comprise two subfamilies within a large group of proteins that display Cys-based, thiol dependent peroxidase activity. These proteins were previously thought to be restricted to prokaryotes, but we show here, using iterated sequence searches, that Ohr/OsmC homologs are also present in 217 species of eukaryotes with a massive presence in Fungi (186 species). Many of these eukaryotic Ohr proteins possess an N-terminal extension that is predicted to target them to mitochondria. We obtained recombinant proteins for four eukaryotic members of the Ohr/OsmC family and three of them displayed lipoyl peroxidase activity. Further functional and biochemical characterization of the Ohr homologs from the ascomycete fungus Mycosphaerella fijiensis Mf_1 (MfOhr), the causative agent of Black Sigatoka disease in banana plants, was pursued. Similarly to what has been observed for the bacterial proteins, we found that: (i) the peroxidase activity of MfOhr was supported by DTT or dihydrolipoamide (dithiols), but not by ß-mercaptoethanol or GSH (monothiols), even in large excess; (ii) MfOhr displayed preference for organic hydroperoxides (CuOOH and tBOOH) over hydrogen peroxide; (iii) MfOhr presented extraordinary reactivity towards linoleic acid hydroperoxides (k=3.18 (±2.13)×108M-1s-1). Both Cys87 and Cys154 were essential to the peroxidase activity, since single mutants for each Cys residue presented no activity and no formation of intramolecular disulfide bond upon treatment with hydroperoxides. The pKa value of the Cysp residue was determined as 5.7±0.1 by a monobromobimane alkylation method. Therefore, eukaryotic Ohr peroxidases share several biochemical features with prokaryotic orthologues and are preferentially located in mitochondria.