Purification of a fully metal-depleted Cu, Zn superoxide dismutase from copper-deficient rat liver

A copper-deprived form of the enzyme Cu, Zn superoxide dismutase was identifiedin the liver of rats made copper-deficient by dietary restriction. In homogenates ofsuch livers Cu, Zn superoxide dismutase presents a dis-homogeneous electrophoreticprofile with respect to the native enzyme. When rat liver extracts were treated withexogenous copper an electrophoretic pattern resembling the native one was observed.Enzyme purified by chromatography on DE-52 resin shows two major components, onecorresponding to genuine, native enzyme and another one, eluting at higher ionicstrength. The latter protein (Fraction II) consists of several isoforms which showthe same characteristics of the native superoxide dismutase as far as immunoreactivityand molecular weight are concerned, but with decreased contents of copper and zinc. Itscatalytic constant, referring to copper content, was 15 times lower than that obtainedfor the native enzyme. Moreover, the catalytic power of purified Fraction II was notregained upon incubation with copper. The occurrence of a superoxide dismutase voidof metals confirms the hypothesis that this protein plays a dual physiological role:in metal metabolism and in superoxide anion dismutation.     

Isoenzymes related to flight activity inTetragonisca angustula (Hymenoptera:Apidae:Meliponinae): Evidence of postranslational modification of the hexokinase and detection of new glycerol-3-phosphate dehydrogenase variants

To detect genetic markers, electrophoretic analyses were carried out onTetragonisca angustula, a stingless bee well adapted to its wide area of occurrence, which is becoming economically important because of the quality of its honey. Polymorphism of the enzyme hexokinase was detected and it was demonstrated that, although it presents two bands in meliponines, this enzyme is under the control of a single locus whose product probably undergoes postranslational modification. The more common allele occurs in the twoTetragonisca subspecies studied here, but the other seems to be characteristic of only one subspecies. Four variants involving the two glycerol-3-phosphate dehydrogenase loci are also described. These two enzymes share the property of presenting two electrophoretic bands, one of which is characteristic of actively flying adult thoraces.     

Sodium Perchlorate Effects on the Helical Stability of a Mainly Alanine Peptide

Sodium perchlorate salt (NaClO₄) is commonly used as an internal intensity standard in ultraviolet resonance Raman (UVRR) spectroscopy experiments. It is well known that NaClO₄ can have profound effects on peptide stability. The impact of NaClO₄ on protein stability in UVRR experiments has not yet been fully investigated. It is well known from experiment that protein stability is strongly affected by the solution composition (water, salts, osmolytes, etc.). Therefore, it is of the utmost importance to understand the physical basis on which the presence of salts and osmolytes in the solution impact protein structure and stability. The aim of this study is to investigate the effects of NaClO₄, on the helical stability of an alanine peptide in water. Based upon replica-exchange molecular dynamics data, it was found that NaClO₄ solution strongly stabilizes the helical state and that the number of pure helical conformations found at room temperature is greater than in pure water. A thorough investigation of the anion effects on the first and second solvation shells of the peptide, along with the Kirkwood-Buff theory for solutions, allows us to explain the physical mechanisms involved in the observed specific ion effects. A direct mechanism was found in which ClO₄⁻ ions are strongly attracted to the folded backbone.     

Characterization of rat liver cells transformed in culture bydl-ethionine

Summary A rat liver-derived epithelial cell line transformed withdl-ethionine and the corresponding control cell line were characterized according to morphological and cytochemical criteria to establish their origin from liver epithelium and to identify cellular changes due to transformation bydl-ethionine. The presence of intermediate junctions confirms the epithelial nature; glycogen accumulation and glucose-6-phosphatase activity confirm the hepatic origin of the cells. Persistent alterations resulting from ethionine transformation were variations in cell shape and size, focal multilayered growth, an increase in the nucleolar: nuclear ratio, and a reduction in the number of cells displaying a primary cilium. Hyperplasia of the inner nuclear membrane, elongation and branching of mitochondria, and a reduction in the length and frequency of cell junctions were also characteristic of the transformed cells.     

Modelling and simulation of the adsorption of the lipase from Geotrichum sp. on hydrophobic interaction columns

The Langmuir model fitted well the adsorption isotherms of lipase on the hydrophobic resin. The model parameters, Q _m and k _d, were affected by NaCl concentration: Q _m increased from 31 to 80 U g^–1 resin, and k _d changed from 9.4 to 3 U ml^–1. Column modelling and the simulation data were compared with the experimental data with good agreement. The highest achieved column efficiency was 71%.     

Molecular Phylogeny of Grey Mullets Based on Mitochondrial DNA Sequence Analysis: Evidence of a Differential Rate of Evolution at the Intrafamily Level

The phylogeny of the grey mullets is considered problematic both at the intra- and interfamily level. Such a difficulty arises from the highly homogeneous morphology displayed by this group of fish and, consequently, from the paucity of the key morphological characters suitable to address their phylogeny and evolution. In the present work, we have approached the phylogenetic and evolutionary relationships of seven species of Mugilidae, six of which from the Mediterranean Sea, on the basis of the DNA sequences of two mitochondrial genes (cytochromeband 12S rRNA). Despite the morphological homogeneity exhibited by the taxa considered, the two species of the genusMugil(M. cephalusandM. curema) showed a remarkable genetic divergence compared to all the other members of the family. The relative rate test revealed a significantly higher rate of evolution along theMugillineage.