The Performance of a Glass Bead Shaking Technique for the Disruption of Escherichia coli Cells

Ramakrishnan Nagasundara Ramanan,Tau Chuan Ling,Arbakariya B. Ariff 한국생물공학회 2008 Biotechnology and Bioprocess Engineering Vol.13 No.5

The efficacy of a simple laboratory method for cell disruption based on the shaking of glass beads on a rotary shaker was assessed in this study, via measurements of the release of total protein and interferon-2b from E. coli. The op-timum conditions for cell disruption were detected after 30 min of shaking in Tris-HCl buffer (pH 8) at 300 rpm with 1.5 g of glass beads (diameter: 0.5 mm) per mL of cell suspension volume. Three test runs were conducted under the above conditions and the maximum average protein release values were determined as 3.048, 3.564, and 3.015 mg/mL, respectively. The amount of protein release was comparable to the amount of protein release in ultrasonica-tion and glass bead vortexing procedures. The amount of interferon-2b release in the ultrasonication, glass bead vortexing, and glass bead shaking trials were 240, 172, and 201 ng/mL, respectively. This method was shown to process between 1 and 10 mL of sample volume in a 50 mL Falcon tube without a great deal of deviation, and was able to handle in excess of 60 samples simultaneously.

Dual Heteroatom-Doped Carbon Nanofoam-Wrapped Iron Monosulfide Nanoparticles: An Efficient Cathode Catalyst for Li-O₂Batteries

Ramakrishnan, Prakash,Shanmugam, Sangaraju,Kim, Jae Hyun WILEY-VCH 2017 CHEM SUS CHEM Vol.10 No.7

<P>Cost-effective dual heteroatom-doped 3D carbon nanofoam-wrapped FeS nanoparticles (NPs), FeS-C, act as efficient bifunctional catalysts for Li-O-2 batteries. This cathode exhibits a maximum deep discharge capacity of 14777.5mAhg(-1) with a 98.1% columbic efficiency at 0.1mAcm(-2). The controlled capacity (500mAhg(-1)) test of this cathode delivers a minimum polarization gap of 0.73V at 0.1mAcm(-2) and is sustained for 100cycles with an energy efficiency of approximately 64% (1stcycle) and 52% (100thcycle) at 0.3mAcm(-2), under the potential window of 2.0-4.5V. X-ray photoelectron spectroscopy reveals the substantial reversible formation and complete decomposition of Li2O2. The excellent recharging ability, high rate performance, and cycle stability of this catalyst is attributed to the synergistic effect of FeS catalytic behavior and textural properties of heteroatom-doped carbon nanostructures.</P>

Synthesis and Characterization of Pt decorated - Cobalt disulfide [CoS₂]/N-rGO as an electrocatalyst for Ethylene glycol oxidation reaction(EOR)

Ramakrishnan Shanmugam,유동진 한국에너지학회 2018 한국에너지공학회 학술발표회 Vol.2018 No.11

Three-dimensional hierarchical nitrogen-doped arch and hollow nanocarbons: morphological influences on supercapacitor applications

Ramakrishnan, Prakash,Park, Soo-Gil,Shanmugam, Sangaraju The Royal Society of Chemistry 2015 Journal of Materials Chemistry A Vol.3 No.31

<P>We report nitrogen (N) doped nanocarbons with two different morphologies, arch and hollow structure, for supercapacitor (SC) application. A simple co-axial electrospinning approach and subsequent leaching and carbonization processes are employed to fabricate N-doped carbon nanostructures. The fabricated N-doped arch and hollow nanocarbons exhibit high N-contents of 9.02 and 8.73 wt%, high surface areas of 619 and 557 m<SUP>2</SUP>g<SUP>−1</SUP>, and total pore volumes of 0.6589 and 0.5681 cm<SUP>3</SUP>g<SUP>−1</SUP>, respectively. The N-doped arch and hollow nanocarbons exhibit the maximum specific capacitances (<I>C</I>sp) of 417 and 371 F g<SUP>−1</SUP>at 2 mV s<SUP>−1</SUP>in a three-electrode system and<I>C</I>spvalues of 230 and 212 F g<SUP>−1</SUP>at 2 mV s<SUP>−1</SUP>for a two-electrode system, respectively, in 1 M H2SO4solution. The maximum energy densities of 8.4 and 7.5 W h kg<SUP>−1</SUP>are obtained for N-doped arch and hollow nanocarbons, respectively. Further, these novel carbon nanostructures also deliver good cycle stabilities of 98% for 5000 cycles at a current density of 1 A g<SUP>−1</SUP>. Such outstanding SC electro-sorption ability is due to the high micro-texture and high N-content characteristics of carbon nanostructures.</P>

Nitrogen and sulfur co-doped metal monochalcogen encapsulated honeycomb like carbon nanostructure as a high performance lithium-ion battery anode material

Ramakrishnan, Prakash,Baek, Seong-Ho,Park, Yiseul,Kim, Jae Hyun Elsevier 2017 Carbon Vol.115 No.-

<P>Iron sulfide based lithium primary batteries have shown commercial success in the battery market, since then it has been considered as the most promising candidate to substitute commercial carbon-based anodes for rechargeable lithium-ion batteries. Nevertheless, practical implementation of iron sulfide anode in lithium secondary battery is greatly suffered by huge volume expansion during repeated conversion process. To address these Issues, we have designed a rational three-dimensional hierarchical honey comb-like iron mono-sulfide (FeS) nanoparticles (nps) encapsulated by dual heteroatoms (nitrogen and sulfur) doped carbon nanostructures (HFSC), using metal organic complex. A series of HFSC composites: compact-and free-bound carbon framework, thickness of encapsulated nanolayer carbon (similar to 1.5-similar to 3.5 nm) over FeS.nps, average size distribution of FeS nps over the carbon surface-and edge-sites, amount of nitrogen (7.18-3.26 at.%) and sulfur (6.63-4.64 at.%) functionalities, have been easily controlled via synthesis temperature. The HFSC anode of desirable physiochemical properties delivers the maximum discharge capacities of 1106.9 and 616.9 mAhg(-1) at low and high current densities of 100 and 1100 mAg(-1), respectively. Further, these novel HFSC composites deliver appreciable cycle stability of 90% for 50 cycles at a moderate current density of 500 mAg(-1). (C) 2017 Elsevier Ltd. All rights reserved.</P>

Biomechanical disc culture system: feasibility study using rat intervertebral discs

Ramakrishnan, P S,Hong, J,Martin, J A,Kurriger, G L,Buckwalter, J A,Lim, T-H SAGE Publications 2011 Proceedings of the Institution of Mechanical Engin Vol.225 No.6

Molecular characterization of two alkylresorcylic acid synthases from <i>Sordariomycetes</i> fungi

Ramakrishnan, Dhivya,Tiwari, Manish K.,Manoharan, Gomathi,Sairam, Thiagarajan,Thangamani, Rajesh,Lee, Jung-Kul,Marimuthu, Jeya Elsevier 2018 Enzyme and microbial technology Vol.115 No.-

<P><B>Abstract</B></P> <P>Two putative type III polyketide synthase genes (PKS) were identified from Sordariomycetes fungi. These two type III PKS genes from <I>Sordaria macrospora</I> (SmPKS) and <I>Chaetomium thermophilum</I> (CtPKS), shared 59.8% sequence identity. Both, full-length and truncated versions of type III PKSs were successfully cloned and overexpressed in a bacterial host, <I>Escherichia Coli</I> BL21 (DE3) using a N-terminus hexa-histidine tag. The full-length and the truncated construct of PKSs showed similar activity profiles, suggesting that additional amino acid residues at the C-terminal of both SmPKS and CtPKS may not be involved in catalytic functions. We demonstrate that these two recombinant polyketide synthases could efficiently synthesize tri- and tetraketide pyrones, resorcinols and resorcylic acids using various acyl-CoAs (C<SUB>4</SUB>–C<SUB>20</SUB>) as starter units. The truncated <I>S. macrospora</I> polyketide synthases (TrSmPKS) showed a maximum of 7.0 × 10<SUP>4</SUP> s<SUP>−1</SUP> M<SUP>−1</SUP> catalytic efficiency towards stearoyl-CoA.Whereas, truncated <I>C. thermophilum</I> polyketide synthases (TrCtPKS) preferred the long-chain acyl-CoA starter arachidoyl-CoA, to produce pentaketide and hexaketide resorcinols with a high catalytic efficiency of 6.2 × 10<SUP>4</SUP> s<SUP>−1</SUP> M<SUP>−1</SUP>. Homology model and substrate docking analyses suggest a shorter distance between sulfur of catalytic Cys152 and thioester carbonyl group of arachidoyl-CoA as well as stronger imidazolium–thiolate ion pair distance in TrCtPKS between catalytic Cys152-His309 compared to TrSmPKS- arachidoyl CoA complex. Enhanced binding interactions of CtPKS residues forming intermolecular contacts at the active site could be attributed to its high specificity towards arachidoyl-CoA. This study reports the functional characterization of two fungal type III polyketide synthases, SmPKS and CtPKS with high catalytic efficiency from S. <I>macrospora</I> and C. <I>thermophilum</I> respectively. Furthermore, the results suggested that the both SmPKS and CtPKS could be attractive targets for protein engineering to discern the unique substrate specificity and catalytic efficiency.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The study reports the functional characterization of two fungal type III polyketide synthases, SmPKS and CtPKS with high catalytic efficiency. </LI> <LI> Both the recombinant PKSs efficiently synthesize pyrones, resorcylic acids and resorcinols using various acyl- CoA (C<SUB>4</SUB>–C<SUB>20</SUB>) as starter units. </LI> <LI> TrCtPKS produces pentaketide and hexaketide resorcinols from arachidoyl-CoA with a high catalytic efficiency of 6.2 × 10<SUP>4</SUP> s<SUP>−1</SUP> M<SUP>−1</SUP>. </LI> <LI> Enhanced binding interactions of CtPKS residues forming intermolecular contacts at the active site could be attributed to its high specificity. </LI> </UL> </P>

Loss of von Hippel-Lindau Protein (VHL) Increases Systemic Cholesterol Levels through Targeting Hypoxia-Inducible Factor 2α and Regulation of Bile Acid Homeostasis

Ramakrishnan, Sadeesh K.,Taylor, Matthew,Qu, Aijuan,Ahn, Sung-Hoon,Suresh, Madathilparambil V.,Raghavendran, Krishnan,Gonzalez, Frank J.,Shah, Yatrik M. American Society for Microbiology 2014 Molecular and cellular biology Vol.34 No.7

<P>Cholesterol synthesis is a highly oxygen-dependent process. Paradoxically, hypoxia is correlated with an increase in cellular and systemic cholesterol levels and risk of cardiovascular diseases. The mechanism for the increase in cholesterol during hypoxia is unclear. Hypoxia signaling is mediated through hypoxia-inducible factor 1α (HIF-1α) and HIF-2α. The present study demonstrates that activation of HIF signaling in the liver increases hepatic and systemic cholesterol levels due to a decrease in the expression of cholesterol hydroxylase CYP7A1 and other enzymes involved in bile acid synthesis. Specifically, activation of hepatic HIF-2α (but not HIF-1α) led to hypercholesterolemia. HIF-2α repressed the circadian expression of Rev-erbα, resulting in increased expression of E4BP4, a negative regulator of <I>Cyp7a1</I>. To understand if HIF-mediated decrease in bile acid synthesis is a physiologically relevant pathway by which hypoxia maintains or increases systemic cholesterol levels, two hypoxic mouse models were assessed, an acute lung injury model and mice exposed to 10% O<SUB>2</SUB> for 3 weeks. In both models, cholesterol levels increased with a concomitant decrease in expression of genes involved in bile acid synthesis. The present study demonstrates that hypoxic activation of hepatic HIF-2α leads to an adaptive increase in cholesterol levels through inhibition of bile acid synthesis.</P>

The Moderating Effect of Operations Efficiency on the Links between Environmental Performance and Financial Performance: The UK Evidence

Ramakrishnan Ramanathan 아시아기술혁신학회 2015 Asian Journal of Innovation and Policy Vol.4 No.1

Drawing upon the resource-based-view of a firm, we investigate the moderating role of operations efficiency on the link between environmental and financial performance. Extant literature has highlighted that operations efficiency is closely associated with the environmental/financial performance of firms, but no empirical study has investigated how operations efficiency affects the link between environmental and financial performance. We argue that operations efficiency could act as a moderator of this relationship. To test the hypothesized relationships, we have used available secondary quantitative UK data, namely data on the environmental/financial performance of Britain’s most admired companies. By employing moderated regression analysis, we have found strong evidence for the moderating impact of operations efficiency. Our results are useful to managers in that they show that improvements in operations efficiency in a company can also help improve environmental/financial performance and vice versa.

"Theoretical investigations on the effect of system parameters in series hydraulic hybrid system with hydrostatic regenerative braking"

R. Ramakrishnan,Somashekhar S. Hiremath,M. Singaperumal 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.5

"As gasoline prices rise and the green movement grows, more fluid power companies are working to develop hydraulic hybrid drive trains for large trucks to passenger cars and wind turbines. The hydraulic hybrid drive system is more effective and efficient than traditional hybrid systems because the quantum of recuperation energy generated is comparatively very high. Series hydraulic hybrid system specially designed for stop-and-go vehicles captures energy as the vehicle brakes and puts the vehicle in motion, when the vehicle is restarted. Then the engine kicks in, once the energy captured gets depleted. The kinetic energy lost as heat energy during mechanical friction braking is recovered and stored in the hydraulic accumulator as potential energy during hydrostatic regenerative braking. This paper gives an insight in to the dynamic simulation results obtained using LMS AMESim tool and effect of various system parameters like pre-charge pressure and hydraulic pump/motor maximum displacement on system output power. Varying the pre-charge pressure of the accumulator and controlling the hydraulic pump/motor maximum displacement show significant improvement in the system output power. Maximizing the system output power indirectly leads to less fuel consumption and pollution reduction in hybrid vehicles."