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Sperm Transfer and Sperm Activation in Tasar Silkmoth, Antheraea Mylitta
Ravikumar, G.,Rajeswary, H.,Ojha, N. G.,Sinha, S. S. 한국잠사학회 1998 한국잠사곤충학회지 Vol.40 No.1
Two types of sperm, apyrene and eupyrene, are identified in A. mylitta. The sperm in the adult moth are motionless in seminal vesicles. At the time of ejaculation they received a secretion from male ejaculatory duct that renders them motile. The dissociation of eupyrene bundles, apyrene, eupyrene sperm motility and the sequence of events of sperm migration in both sexes are described in the present paper.
Ravikumar B.,D. Thukaram,H. P. Khincha 대한전기학회 2008 Journal of Electrical Engineering & Technology Vol.3 No.3
In this paper, knowledge-based approach using Support Vector Machines (SVMs) are used for estimating the coordinated zonal settings of a distance relay. The approach depends on the detailed simulation studies of apparent impedance loci as seen by distance relay during disturbance, considering various operating conditions including fault resistance. In a distance relay, the impedance loci given at the relay location is obtained from extensive transient stability studies. SYMs are used as a pattern classifier for obtaining distance relay co-ordination. The scheme utilizes the apparent impedance values observed during a fault as inputs. An improved performance with the use of SVMs, keeping the reach when faced with different fault conditions as well as system power flow changes, are illustrated with an equivalent 265 bus system of a practical Indian Western Grid.
Ravikumar, Sambandam,Yoo, Ik-keun,Lee, Sang Yup,Hong, Soon Ho Springer-Verlag 2011 Applied biochemistry and biotechnology Vol.165 No.7
<P>Synthetic biological systems are becoming more and more feasible for commercial and medical purposes through the genetic engineering of several components. The simple assembly of a genetic circuit was shown to stimulate the removal of copper by bacteria through the engineering of a two-component system. The CusSR two-component systems is a regulator of Escherichia coli copper homeostatic system. In this system, genetic circuits of CusSR were fused to a cell surface display system for metal adsorption; this system is suitable for the display of a copper binding peptide through outer membrane protein C (OmpC). E. coli ompC codes for an outer membrane pore protein (porin) are induced at high osmolarity and temperature, which can also be used as an anchoring motif to accept the passenger proteins. The bacteria that produce the chimeric OmpC containing the copper binding peptide adsorbed maximum concentrations of 92.2 μmol of Cu(2+)/gram dry weight of bacterial cells. This synthetic bacterial system senses the specific heavy metal and activates a cell surface display system that acts to remove the metal.</P>
Engineering an FMN-based iLOV protein for the detection of arsenic ions
Ravikumar, Y.,Nadarajan, S.p.,Lee, C.s.,Yun, H. Academic Press 2017 Analytical Biochemistry Vol.525 No.-
<P>Over the past few decades, genetically encoded fluorescent proteins have been widely used as efficient probes to explore and investigate the roles of metal ions in biological processes. The discovery of small FMN-based fluorescent proteins, such as iLOV and FbFP, has enabled researchers to exploit these fluorescent reporter proteins for metal-sensing applications. In this study, we report the inherent binding properties of iLOV towards arsenic ions. The fluorescence quenching of iLOV was linearly related to the concentration of arsenic ions, and engineered proteins showed better sensitivity than the wild-type protein. Engineering key residues around the chromophore converted the iLOV protein into a highly sensitive sensor for Asa(3+) ions. iLOV(N468S) exhibited an improved binding affinity with a dissociation constant of 1.5 mu M. Furthermore, the circular dichroism spectra indicated that the fluorescence quenching mechanism might be related to arsenic-protein complex formation. Thus, the reagentless sensing of arsenic can potentially be exploited to determine intracellular or environmental arsenic using a genetically encoded biosensing approach. (C) 2017 Elsevier Inc. All rights reserved.</P>
Ravikumar, Sambandam,David, Yokimiko,Park, Si Jae,Choi, Jong-il Humana Press 2018 Applied biochemistry and biotechnology Vol.186 No.2
<P>In this study, we constructed amino acid biosensors that can be used as a high-throughput system to screen microorganisms that produce glutamate. The biosensors are based on two-component regulatory systems (TCRSs) combined with green fluorescent protein (GFP) as a reporter. A chimeric DegS/EnvZ (DegSZ) TCRS was constructed by fusing the N-terminal domain of the sensor kinase DegS from Planococcus sp. PAMC21323 with the catalytic domain of the osmosensor EnvZ from Escherichia coli to control expression of gfp in response to glutamate. gfp was controlled by the ompC promoter through the activated response regulator OmpR-P. The chimeric TCRS-based biosensors showed a 4-fold increase in the fluorescent signal after adding glutamate. A linear correlation was observed between fluorescence intensity and exogenously added glutamate concentration. The chimeric TCRS-based biosensor was used to determine glutamate concentration at the single-cell level by fluorescence-activated cell sorting. Therefore, this biosensor can be used to isolate novel gene products and optimize pathways involved in amino acid production.</P>
A New-Generation Fluorescent-Based Metal Sensor-iLOV Protein
( Yuvaraj Ravikumar ),( Saravanan Prabhu Nadarajan ),( Chong Soon Lee ),( Jin Kyu Rhee ),( Hyung Don Yun ) 한국미생물 · 생명공학회 2015 Journal of microbiology and biotechnology Vol.25 No.4
The iLOV protein belongs to a family of blue-light photoreceptor proteins containing a lightoxygen- voltage sensing domain with a noncovalently bound flavin mononucleotide (FMN) as its chromophore. Owing to advantages such as its small size, oxygen-independent nature, and pH stability, iLOV is an ideal candidate over other reporter fluorescent proteins such as GFP and DsRed. Here, for the first time, we describe the feasibility of applying LOV domain-based fluorescent iLOV as a metal sensor by measuring the fluorescence quenching of a protein with respect to the concentration of metal ions. In the present study, we demonstrated the inherent copper sensing property of the iLOV protein and identified the possible amino acids responsible for metal binding. The fluorescence quenching upon exposure to Cu2+ was highly sensitive and exhibited reversibility upon the addition of the metal chelator EDTA. The copper binding constant was found to be 4.72 ± 0.84 μM. In addition, Cu2+-bound iLOV showed high fluorescence quenching at near physiological pH. Further computational analysis yielded a better insight into understanding the possible amino acids responsible for Cu2+ binding with the iLOV protein.