Publications by authors named "Satarupa Das"

A novel nickel-based metal organic framework (MOF) [Ni(FDC)(CHOH)(HO)](HO) (UOW-6) utilizing biomass-derived 2,5-furan dicarboxylate (FDC) as a ligand is reported as an electrocatalyst for anodic ethylene glycol (EG) oxidation with cathodic hydrogen evolution. The MOF structure was analyzed using single crystal X-ray-diffraction, thermogravimetric analysis (TGA) and thermodiffractometry, to establish its structure and verify phase purity. The material was dropcast on carbon fiber paper as a catalyst, and by using a three-electrode system, UOW-6 requires only 1.

View Article and Find Full Text PDF

In Saccharomyces cerevisiae, the CBC-Tif4631p-dependent exosomal targeting (CTEXT) complex consisting of Cbc1/2p, Tif4631p and Upf3p promotes the exosomal degradation of aberrantly long 3'-extended, export-defective transcripts and a small group of normal (termed 'special') mRNAs. We carried out a systematic analysis of all previously characterized functional domains of the major CTEXT component Tif4631p by deleting each of them and interrogating their involvement in the nuclear surveillance of abnormally long 3'-extended and export-defective messages. Our analyses show that the N-terminal RNA recognition motif 1 (RRM1) and poly(A)-binding protein (PAB) domains of Tif4631p, spanning amino acid residues, 1-82 and 188-299 in its primary structure, respectively, play a crucial role in degrading these aberrant messages.

View Article and Find Full Text PDF

CO epoxidation to cyclic carbonates under mild, solvent-free conditions is a promising pathway toward sustainable CO utilization. Metal-organic frameworks (MOFs) explored for such applications so far are commonly composed of nonrenewable ligands such as benzene dicarboxylate (BDC) or synthetically complex linkers and therefore are not suitable for commercial utilization. Here, we report new yttrium 2,5-furandicarboxylate (FDC)-based MOFs: "UOW-1" and "UOW-2" synthesized via solvothermal assembly, with the former having a unique structural topology.

View Article and Find Full Text PDF

Modern day electrochemical devices find applications in a wide range of industrial sectors, from consumer electronics, renewable energy management to pollution control by electric vehicles and reduction of greenhouse gas. There has been a surge of diverse electrochemical systems which are to be scaled up from the lab-scale to industry sectors. To achieve the targets, the electrocatalysts are continuously upgraded to meet the required device efficiency at a low cost, increased lifetime and performance.

View Article and Find Full Text PDF

cells transport adenylyl cyclase A (ACA)-containing vesicles to the back of polarized cells to relay exogenous cAMP signals during chemotaxis. Fluorescence hybridization (FISH) experiments showed that ACA mRNA is also asymmetrically distributed at the back of polarized cells. By using the MS2 bacteriophage system, we now visualize the distribution of ACA mRNA in live chemotaxing cells.

View Article and Find Full Text PDF

Background: In Dictyostelium discoideum, vesicular transport of the adenylyl cyclase A (ACA) to the posterior of polarized cells is essential to relay exogenous 3',5'-cyclic adenosine monophosphate (cAMP) signals during chemotaxis and for the collective migration of cells in head-to-tail arrangements called streams.

Results: Using fluorescence in situ hybridization (FISH), we discovered that the ACA mRNA is asymmetrically distributed at the posterior of polarized cells. Using both standard estimators and Monte Carlo simulation methods, we found that the ACA mRNA enrichment depends on the position of the cell within a stream, with the posterior localization of ACA mRNA being strongest for cells at the end of a stream.

View Article and Find Full Text PDF

The eukaryotic translation initiation factor, eIF4G, plays a key functional role in the initiation of cap-dependent translation by acting as an adapter to nucleate the assembly of eIF4F complex. Together with poly(A)-binding protein and eIF3, eIF4F subsequently triggers the recruitment of 43S ribosomal pre-initiation complex to the messenger RNA template. Since eukaryotes primarily regulate translation at the level of initiation, eIF4G is implicated in the control of eukaryotic gene expression.

View Article and Find Full Text PDF

Leishmania is an intracellular protozoan parasite that causes a broad spectrum of clinical manifestations, ranging from self-healing skin lesions to fatal visceralizing disease. As the host cells of choice for all species of Leishmania, macrophages are critical for the establishment of infections. How macrophages contribute to parasite homing to specific tissues and how parasites modulate macrophage function are still poorly understood.

View Article and Find Full Text PDF

Many biological and physiological processes depend upon directed migration of cells, which is typically mediated by chemical or physical gradients or by signal relay. Here we show that cells can be guided in a single preferred direction based solely on local asymmetries in nano/microtopography on subcellular scales. These asymmetries can be repeated, and thereby provide directional guidance, over arbitrarily large areas.

View Article and Find Full Text PDF

Messenger RNAs retained in the nucleus of Saccharomyces cerevisiae are subjected to a degradation system designated DRN (Degradation of mRNA in the Nucleus) that is dependent on the nuclear mRNA cap-binding protein, Cbc1p, as well as nuclear exosome component Rrp6p, a 3' to 5' exoribonuclease. DRN has been shown to act on RNAs preferentially retained in the nucleus, such as: (1) global mRNAs in export defective nup116-Δ mutant strains at the restrictive temperature; (2) a certain class of normal mRNAs called special mRNAs (e.g.

View Article and Find Full Text PDF

Administration of exogenous L-arginine (L-Arg) attenuates angiotensin-II (AngII)-mediated hypertension and kidney disease in rats. The present study assessed renal hemodynamics and pressure diuresis-natriuresis in anaesthetized rats infused with vehicle, AngII (20 ng/kg per min i.v.

View Article and Find Full Text PDF

Efficient production of translation-competent mRNAs involves processing and modification events both in the nucleus and cytoplasm which require a number of complex machineries at both co-transcriptional and posttranscriptional levels. Mutations in the genomic sequence sometimes result in the formation of mutant nonfunctional defective messages. In addition, the enormous amounts of complexities involved in the biogenesis of mRNPs in the nucleus very often leads to the formation of aberrant and faulty messages along with their functional counterpart.

View Article and Find Full Text PDF

Upon starvation, individual Dictyostelium discoideum cells enter a developmental program that leads to collective migration and the formation of a multicellular organism. The process is mediated by extracellular cAMP binding to the G protein-coupled cAMP receptor 1, which initiates a signaling cascade leading to the activation of adenylyl cyclase A (ACA), the synthesis and secretion of additional cAMP, and an autocrine and paracrine activation loop. The release of cAMP allows neighboring cells to polarize and migrate directionally and form characteristic chains of cells called streams.

View Article and Find Full Text PDF

Transcription of the genes for a fructan hydrolase (fruA) and a fructose/mannose sugar:phosphotransferase permease (levDEFG) in Streptococcus mutans is activated by a four-component regulatory system consisting of a histidine kinase (LevS), a response regulator (LevR) and two carbohydrate-binding proteins (LevQT). The expression of the fruA and levD operons was at baseline in a levQ mutant and substantially decreased in a levT null mutant, with lower expression with the cognate inducers fructose or mannose, but slightly higher expression in glucose or galactose. A strain expressing levQ with two point mutations (E170A/F292S) did not require inducers to activate gene expression and displayed altered levD expression when growing on various carbohydrates, including cellobiose.

View Article and Find Full Text PDF

We studied the role of the target of rapamycin complex 2 (mTORC2) during neutrophil chemotaxis, a process that is mediated through the polarization of actin and myosin filament networks. We show that inhibition of mTORC2 activity, achieved via knock down (KD) of Rictor, severely inhibits neutrophil polarization and directed migration induced by chemoattractants, independently of Akt. Rictor KD also abolishes the ability of chemoattractants to induce cAMP production, a process mediated through the activation of the adenylyl cyclase 9 (AC9).

View Article and Find Full Text PDF

In chemotactic cells, G protein-coupled receptors activate Ras proteins, but it is unclear how Ras-associated pathways link extracellular signaling to cell migration. We show that, in Dictyostelium discoideum, activated forms of RasC prolong the time course of TORC2 (target of rapamycin [Tor] complex 2)-mediated activation of a myristoylated protein kinase B (PKB; PKBR1) and the phosphorylation of PKB substrates, independently of phosphatidylinositol-(3,4,5)-trisphosphate. Paralleling these changes, the kinetics of chemoattractant-induced adenylyl cyclase activation and actin polymerization are extended, pseudopodial activity is increased and mislocalized, and chemotaxis is impaired.

View Article and Find Full Text PDF

Abundant in milk and other dairy products, lactose is considered to have an important role in oral microbial ecology and can contribute to caries development in both adults and young children. To better understand the metabolism of lactose and galactose by Streptococcus mutans, the major etiological agent of human tooth decay, a genetic analysis of the tagatose-6-phosphate (lac) and Leloir (gal) pathways was performed in strain UA159. Deletion of each gene in the lac operon caused various alterations in expression of a P(lacA)-cat promoter fusion and defects in growth on either lactose (lacA, lacB, lacF, lacE, and lacG), galactose (lacA, lacB, lacD, and lacG) or both sugars (lacA, lacB, and lacG).

View Article and Find Full Text PDF

This study examined mechanisms by which immune cells participate in the development of hypertension and renal disease in Dahl salt-sensitive (SS) rats. Increasing dietary salt from 0.4% to 4.

View Article and Find Full Text PDF

Cyclic AMP has a crucial role during the entire developmental program of the social amoebae Dictyostelium, acting both as an intracellular second messenger and, when secreted, as a directional cue that is relayed to neighboring cells during chemotaxis. Although significant knowledge about cAMP production in chemotaxing cells has been derived from studies performed on cell populations, cAMP dynamics at the single cell level have not been investigated. To examine this, we used a FRET-based cAMP sensor that possesses high cAMP sensitivity and great temporal resolution.

View Article and Find Full Text PDF

Experiments were performed to determine whether exogenous L-arginine could ameliorate angiotensin II-induced hypertension and renal damage. Rats were instrumented with chronic indwelling femoral venous and arterial catheters for infusions of drugs and measurement of conscious arterial pressure. Arterial blood pressure significantly increased from 124+/-1 to 199+/-4 mm Hg, after 9 days of continuous infusion of angiotensin II (20 ng/kg per minute; IV; n=6 to 9).

View Article and Find Full Text PDF

Atherosclerosis remains a major cause of death in the developed world despite the success of therapies that lower cholesterol and BP. The intermediate-conductance calcium-activated potassium channel KCa3.1 is expressed in multiple cell types implicated in atherogenesis, and pharmacological blockade of this channel inhibits VSMC and lymphocyte activation in rats and mice.

View Article and Find Full Text PDF

We previously demonstrated that mRNAs retained in the nucleus of Saccharomyces cerevisiae are subjected to a degradation system-designated DRN (degradation of mRNA in the nucleus), that is diminished in cbc1-Delta or cbc2-Delta mutants lacking components of the cap-binding complex and in rrp6-Delta mutants lacking Rrp6p, a 3' to 5' nuclear exonuclease. Two mutants, lys2-187 and lys2-121, were uncovered by screening numerous lys2 mutants for suppression by cbc1-Delta and rrp6-Delta. Both mutants were identical and contained the two base changes, one of which formed a TGA nonsense codon.

View Article and Find Full Text PDF

A PHP Error was encountered

Severity: Warning

Message: fopen(/var/lib/php/sessions/ci_sessionssbk23orhhbsgrnep8uct7fsrbknbk23): Failed to open stream: No space left on device

Filename: drivers/Session_files_driver.php

Line Number: 177

Backtrace:

File: /var/www/html/index.php
Line: 316
Function: require_once

A PHP Error was encountered

Severity: Warning

Message: session_start(): Failed to read session data: user (path: /var/lib/php/sessions)

Filename: Session/Session.php

Line Number: 137

Backtrace:

File: /var/www/html/index.php
Line: 316
Function: require_once