On commutativity of prime and semiprime rings with generalized derivations

Let $R$ be a prime ring, extended centroid $C$ and $m, n, k \geq1$ are fixed integers. If $R$ admits a generalized derivation $F$ associated with a derivation $d$ such that $(F(x)\circ y)^{m}+(x\circ d(y))^{n}=0$ or $(F(x)\circ_{m} y)^{k} + x\circ_{n} d(y)$=0 for all $x, y \in I$, where $I$ is a nonzero ideal of $R$, then either $R$ is commutative or there exist $b\in U$, Utumi ring of quotient of $R$ such that $F(x)=bx$ for all $x \in R$. Moreover, we also examine the case $R$ is a semiprime ring

Generalized (; )-derivations and Left Ideals in Prime and Semiprime Rings

Let R be an associative ring, ; be the automorphisms of R, be a nonzero left ideal of R, F : R ! R be a generalized (; )-derivation and d : R ! Rbe an (; )-derivation. In the present paper we discuss the following situations: (i) F(xoy) = a(xy yx), (ii) F([x; y]) = a(xy yx), (iii) d(x)od(y) = a(xy yx) forall x; y 2 and a 2 f0; 1;ô€€€1g. Also some related results have been obtained

ISSR Marker Based Population Genetic Study of Melocanna baccifera (Roxb.) Kurz: A Commercially Important Bamboo of Manipur, North-East India

Melocanna baccifera (Roxb.) Kurz is an economically important bamboo of North-East India experiencing population depletion in its natural habitats. Genetic variation studies were conducted in 7 populations sampled from 5 districts of Manipur using ISSR molecular markers. The investigation was carried out as a primary step towards developing effective conservation strategies for the protection of bamboo germplasm. ISSR marker analysis showed significant level of genetic variation within the populations as revealed by moderately high average values of Nei’s genetic diversity (H 0.1639), Shannon’s diversity index (I 0.2563), percentage of polymorphic bands (PPB 59.18), total genetic variation (Ht 0.1961), and genetic diversity within population (Hs 0.1639). The study also divulged a high genetic variation at species level with Shannon’s diversity index (I), Nei’s genetic diversity (H), and percentage of polymorphic band (PPB%) recorded at 0.3218, 0.1939, and 88.37, respectively. Genetic differentiation among the populations (Gst) was merely 19.42% leaving 80.58% of genetic variation exhibited within the populations. The low genetic diversity between populations was consistent with AMOVA. The low genetic differentiation among populations coupled with existence of significantly high genetic diversity at species level indicated the urgent necessity of preserving and protecting all the existing natural bamboo populations in the region

Hyperoxidation of Peroxiredoxin 6 Induces Alteration from Dimeric to Oligomeric State

Peroxiredoxins(Prdx), the family of non-selenium glutathione peroxidases, are important antioxidant enzymes that defend our system from the toxic reactive oxygen species (ROS). They are thiol-based peroxidases that utilize self-oxidation of their peroxidatic cysteine (Cp) group to reduce peroxides and peroxidized biomolecules. However, because of its high affinity for hydrogen peroxide this peroxidatic cysteine moiety is extremely susceptible to hyperoxidation, forming peroxidase inactive sulfinic acid (Cys-SO2H) and sulfonic acid (Cys-SO3H) derivatives. With the exception of peroxiredoxin 6 (Prdx6), hyperoxidized sulfinic forms of Prdx can be reversed to restore peroxidase activity by the ATP-dependent enzyme sulfiredoxin. Interestingly, hyperoxidized Prdx6 protein seems to have physiological significance as hyperoxidation has been reported to dramatically upregulate its calcium independent phospholipase A2 activity. Using biochemical studies and molecular dynamic (MD) simulation, we investigated the roles of thermodynamic, structural and internal flexibility of Prdx6 to comprehend the structural alteration of the protein in the oxidized state. We observed the loosening of the hydrophobic core of the enzyme in its secondary and tertiary structures. These changes do not affect the internal dynamics of the protein (as indicated by root-mean-square deviation, RMSD and root mean square fluctuation, RMSF plots). Native-PAGE and dynamic light scattering experiments revealed the formation of higher oligomers of Prdx6 under hyperoxidation. Our study demonstrates that post translational modification (like hyperoxidation) in Prdx6 can result in major alterations of its multimeric status

Equilibrium denaturation curves of cyt-<i>c</i> in the presence of LiCl (Ο) and LiClO₄ (Δ) at pH 6.0 and 25°C.

<p>Denaturation was monitored by Δ<i>ε</i>₄₀₀ (A), Δ[<i>θ</i>]₄₀₉ (B) and [<i>θ</i>]₂₂₂ (C). Inset in panel (B) shows the plot for the dependence of the optical property of the X state (<i>y</i>_X) on [denaturant] on the expanded scale. Panel (D) shows plots of Δ<i>G</i>_I and Δ<i>G</i>_II versus [denaturant]. In this panel filled symbols are obtained from the studies of thermal denaturation in the presence of weak salt denaturants.</p

Heterogeneity of Equilibrium Molten Globule State of Cytochrome <i>c</i> Induced by Weak Salt Denaturants under Physiological Condition

<div><p>While many proteins are recognized to undergo folding via intermediate(s), the heterogeneity of equilibrium folding intermediate(s) along the folding pathway is less understood. In our present study, FTIR spectroscopy, far- and near-UV circular dichroism (CD), ANS and tryptophan fluorescence, near IR absorbance spectroscopy and dynamic light scattering (DLS) were used to study the structural and thermodynamic characteristics of the native (N), denatured (D) and intermediate state (X) of goat cytochorme <i>c</i> (cyt-<i>c</i>) induced by weak salt denaturants (LiBr, LiCl and LiClO₄) at pH 6.0 and 25°C. The LiBr-induced denaturation of cyt-<i>c</i> measured by Soret absorption (Δ<i>ε</i>₄₀₀) and CD ([<i>θ</i>]₄₀₉), is a three-step process, N ↔ X ↔ D. It is observed that the X state obtained along the denaturation pathway of cyt-<i>c</i> possesses common structural and thermodynamic characteristics of the molten globule (MG) state. The MG state of cyt-<i>c</i> induced by LiBr is compared for its structural and thermodynamic parameters with those found in other solvent conditions such as LiCl, LiClO₄ and acidic pH. Our observations suggest: (1) that the LiBr-induced MG state of cyt-<i>c</i> retains the native Met80-Fe(III) axial bond and Trp59-propionate interactions; (2) that LiBr-induced MG state of cyt-<i>c</i> is more compact retaining the hydrophobic interactions in comparison to the MG states induced by LiCl, LiClO₄ and 0.5 M NaCl at pH 2.0; and (3) that there exists heterogeneity of equilibrium intermediates along the unfolding pathway of cyt-<i>c</i> as highly ordered (X1), classical (X2) and disordered (X3), i.e., D ↔ X3 ↔ X2 ↔ X1 ↔ N.</p></div

Increased Phospholipase A₂ Activity with Phosphorylation of Peroxiredoxin 6 Requires a Conformational Change in the Protein

We have shown previously and confirmed in this study that the phospholipase A₂ (PLA₂) activity of peroxiredoxin 6 (Prdx6) is markedly increased by phosphorylation. This report evaluates the conformation and thermodynamic stability of Prdx6 protein after phosphorylation to understand the physical basis for increased activity. Phosphorylation resulted in decreased negative far-UV CD, strengthened ANS binding, and a lack of rigid tertiary structure, compatible with a change in conformation to that of a molten globule. The Δ<i>G</i>°_D was 3.3 ± 0.3 kcal mol^–1 for Prdx6 and 1.7 ± 0.7 kcal mol^–1 for pPrdx6, suggesting that phosphorylation destabilizes the protein. Phosphorylation of Prdx6 changed the conformation of the N-terminal domain exposing Trp 33, as determined by tryptophan fluorescence and NaI fluorescence quenching. The kinetics of interaction of proteins with unilamellar liposomes (50:25:15:10 DPPC:egg PC:cholesterol:PG molar ratio) were evaluated with tryptophan fluorescence. pPrdx6 bound to liposomes with a higher affinity (<i>K</i>_d = 5.6 ± 1.2 μM) than Prdx6 (<i>K</i>_d = 24.9 ± 4.5 μM). By isothermal titration calorimetry, pPrdx6 bound to liposomes with a large exothermic heat loss (Δ<i>H</i> = −31.49 ± 0.22 kcal mol^–1). Correlating our conformational studies with the published crystal structure of oxidized Prdx6 suggests that phosphorylation results in exposure of hydrophobic residues, thereby providing accessibility to the sites for liposome binding. Because binding of the enzyme to the phospholipid substrate interface is a requirement for PLA₂ activity, these results indicate that a change in the conformation of Prdx6 upon its phosphorylation is the basis for enhancement of PLA₂ enzymatic activity

Structural characterization of various states of cyt-<i>c</i>.

<p>In this figure curve numbers have the same meaning in all panels: 1, native state; 2, LiCl-induced MG state in the presence of 6.2 M concentration; 3, LiClO₄-induced MG state in the presence of 1.9 M concentration; 4, LiBr-induced MG state in the presence of 4.2 M concentration; 5, 0.5 M NaCl-induced at pH 2.0; and 6, GdmCl-induced denatured state. Panels A and C show the far-UV and near-UV CD spectra. Panel B shows FTIR spectra. Panels D and E show ANS and Trp-fluorescence spectra. Panel F shows near-IR spectra.</p

LiBr-induced denaturation of cyt-<i>c</i> at pH 6.0 and 25°C.

<p>Equilibrium unfolding transition curves are monitored by Δ<i>ε</i>₄₀₀ (A) and Δ[<i>θ</i>]₄₀₉ (B). Panels (C) and (D) show the normalized transition curves and plots of Δ<i>G</i>_I and Δ<i>G</i>_II as function of [LiBr], respectively. The inset in panel (B) shows the plot for the dependence of the optical property of X state (<i>y</i>_X) on [LiBr] on the expanded scale. Filled symbol in panel (D) represents Δ<i>G</i>_I (or Δ<i>G</i>_II) determined from heat-induced denaturation in the presence of a given [LiBr].</p