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Appukuttan, Deepti,Singh, Harinder,Park, Sun-Ha,Jung, Jong-Hyun,Jeong, Sunwook,Seo, Ho Seong,Choi, Yong Jun,Lim, Sangyong American Society for Microbiology 2016 Applied and environmental microbiology Vol.82 No.4
<P>Cellular robustness is an important trait for industrial microbes, because the microbial strains are exposed to a multitude of different stresses during industrial processes, such as fermentation. Thus, engineering robustness in an organism in order to push the strains toward maximizing yield has become a significant topic of research. We introduced the deinococcal response regulator DR1558 into Escherichia coli (strain Ec-1558), thereby conferring tolerance to hydrogen peroxide (H2O2). The reactive oxygen species (ROS) level in strain Ec-1558 was reduced due to the increased KatE catalase activity. Among four regulators of the oxidative-stress response, OxyR, RpoS, SoxS, and Fur, we found that the expression of rpoS increased in Ec-1558, and we confirmed this increase by Western blot analysis. Electrophoretic mobility shift assays showed that DR1558 bound to the rpoS promoter. Because the alternative sigma factor RpoS regulates various stress resistance-related genes, we performed stress survival analysis using an rpoS mutant strain. Ec-1558 was able to tolerate a low pH, a high temperature, and high NaCl concentrations in addition to H2O2, and the multistress tolerance phenotype disappeared in the absence of rpoS. Microarray analysis clearly showed that a variety of stress-responsive genes that are directly or indirectly controlled by RpoS were upregulated in strain Ec-1558. These findings, taken together, indicate that the multistress tolerance conferred by DR1558 is likely routed through RpoS. In the present study, we propose a novel strategy of employing an exogenous response regulator from polyextremophiles for strain improvement.</P>
Appukuttan Retnabhavan Pradeep,Arvind Awasthi,Raje Urs 한국분자세포생물학회 2008 Molecules and cells Vol.25 No.4
Simple sequence repeats (SSRs) and interSSR (ISSR) marker systems were used in this study to reveal genetic changes induced by artificial selection for short/long larval duration in the tropical strain Nistari of the silkworm Bombyx mori. Artificial selection separated longer larval duration (LLD) (29.428 ± 0.723 days) and shorter larval duration (SLD) (22.573 ± 0.839 days) lines from a base, inbred population of Nistari (larval span of 23.143 ± 0.35 days). SSR polymorphism was observed between the LLD and SLD lines at one microsatellite locus, Bmsat106 (CA7) and at two loci of 1074 bp and 823 bp generated with the ISSR primer UBC873. Each of these loci was present only in the LLD line. The loci segregated in the third generation of selection and were fixed in opposite directions. In the F2 generation of the LLD × SLD lines, the alleles of Bmsat106 and UBC8731074bp segregated in a 1:1 ratio and the loci were present only in the LLD individuals. UBC873823bp was homozygous. Single factor ANOVA showed a significant association between the segregating loci and longer larval duration. Together, the two alleles contributed to an 18% increase in larval duration. The nucleotide sequences of the UBC8731074bp and UBC873823bp loci had 67% A/T content and consisted of direct, reverse, complementary and palindromic repeats. The repeats appeared to be “nested” (59%) in larger repeats or as clustered elements adjacent to other repeats. Of 203 microsatellites identified, dinucleotides (67.8%) predominated and were rich in A/T and T/A motifs. The sequences of the UBC8731074bp and UBC873823bp loci showed similarity (E = 0.0) to contigs located in Scaffold 010774 and Scaffold 000139, respectively, of the B. mori genome. BLASTN analysis of the UBC8731074bp sequence showed significant homology of (nt.) 45–122 with upstream region of three exons from Bombyx. The complete sequence of this locus showed ~49% nucleotide conservation with transposon 412 of Drosophila melanogaster and the Ikirara insertions of Anopheles gambiae. The A + T richness and lack of coding potential of these small loci, and their absence in the SLD line, reflect the active process of genetic change associated with the switch to short larval duration as an adaptation to the tropics.
Appukuttan, Vinu Krishnan,Liu, Yinshan,Son, Bong Chul,Ha, Chang-Sik,Suh, Hongsuk,Kim, Il American Chemical Society 2011 Organometallics Vol.30 No.8
<P>A new series of Fe(II) and Co(II) complexes of sterically modulated 2,3,7,8-tetrahydroacridine-4,5(1<I>H</I>,6<I>H</I>)-diimine by substituted aryl rings are synthesized. The complex synthesis is achieved through a one-pot methodology by reacting one equivalent of 2,3,7,8-tetrahydroacridine-4,5(1<I>H</I>,6<I>H</I>)-dione with two equivalents of required aniline derivatives together with Fe or Co salt in boiling acetic acid. The single-crystal X-ray analyses of Fe and Co complexes bearing a 2,6-diisopropyl-substituted ligand, (<I>N</I>,<I>N</I>′<I>E</I>,<I>N</I>,<I>N</I>′<I>E</I>)-<I>N</I>,<I>N</I>′-(2,3,7,8-tetrahydroacridine-4,5(1<I>H</I>,6<I>H</I>)-diylidene)bis(2,6-diisopropylaniline), show a distorted trigonal-bipyramidal geometry for the metal center, a deviation from square-pyramidal geometry due to the opening up of the coordination sphere originating from structural rigidity of the carbonyl carbon atom achieved through cyclization. All the complexes show high activity toward ethylene activation when treated with methylaluminoxane as a cocatalyst. The <I>ortho</I> substituents of the aryl rings and the type of metal have a significant effect on ethylene activation and specifically on product distribution. The Fe complex with a 2,6-diisopropyl-substituted bis(imino)tetrahydroacridyl ligand produced polyethylene of moderate molecular weight (18 000). On changing the <I>ortho</I> substitution of the ligand from 2,6-diisopropyl to 2,6-dimethyl, the Co complexes produce polyethylene waxes and oligomers of predominantly α-olefins simultaneously, obeying Schulz−Flory distribution. The Co complexes bearing ligands with less sterically hindered substituents at the <I>ortho</I> position behave exclusively as dimerization catalysts.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/orgnd7/2011/orgnd7.2011.30.issue-8/om2000629/production/images/medium/om-2011-000629_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/om2000629'>ACS Electronic Supporting Info</A></P>
Nair, M.L. Harikumaran,Appukuttan, Anju.S. Korean Chemical Society 2012 대한화학회지 Vol.56 No.2
Syntheses of some novel oxomolybdenum(V) and dioxomolybdenum(VI) complexes with an azo dye methoxyphenolazoantipyrine (HL) derived from 4-aminoantipyrine and 2-methoxyphenol are reported. The complexes have been characterized by elemental analyses, molar conductance, magnetic susceptibility data, IR, UV-Vis, $^1H$ NMR, EPR and FAB mass spectral studies. The physicochemical studies and spectral data indicate that HL acts as a bidentate chelating ligand. The complexes have the general formulae [$MoO(HL)XCl_2$] and [$MoO_2(HL)XCl$],where X=Cl, NCS or $NO_3$. All the complexes are found to have distorted octahedral geometry. Structural and morphological characterization of the complexes [$MoO(HL)Cl_3$](1) and [$MoO_2(HL)Cl_2$](4) before and after gamma ray irradiation,was performed by X-ray diffraction and scanning electron microscopy( SEM).The ligand and the complexes were screened for their possible antimicrobial activities.
Il Kim,Vinukrishnan Appukuttan,Jin Hyuk Kim,Chang Sik Ha 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.3
Effects of structural variations of the diimine ligand on catalyst activities for vinyl polymerization of norbornene (NB) have been investigated by a series of Ni(II) α-diimine catalysts of the general formula: [{ArN=C(Ac)- C(Ac)=NAr}]NiBr2 (Ac=acenaphthyl) (Cat(H), Ar=C6H5; Cat(2,6-Me), Ar=2,6-C6H3Me2; Cat(2,6-Et), Ar=2,6-C6H3Et2; Cat(2,6-iPr), Ar=2,6-C6H3 i-Pr2; Cat(2,3-Me), Ar=2,3-C6H3Me2; Cat(2,4-Me), Ar=2,4-C6H3Me2; Cat(2,5-Me), Ar= 2,5-C6H3Me2; Cat(3,5-Me), Ar=3,5-C6H3Me2; Cat(2,4,6-Me), Ar=2,4,6-C6H2Me3). In situ reactions with methylaluminoxane generated the active catalysts, and they showed good activity towards NB polymerizations. As indicated by relatively higher activities of Cat(H) and Cat(3,5-Me), it can be generalized that catalysts having 2,6-substituents are less active due to steric interaction between monomer and substituents. In addition, electron donating methyl groups at 2-, 4- or 6-position on the N-aryl have a con effect and that at 3,5-position has a pro effect.
Suppression Subtractive Hybridization Identifies Novel Transcripts in Regenerating Hydra littoralis
Stout, Thomas,McFarland, Trevor,Appukuttan, Binoy Korean Society for Biochemistry and Molecular Biol 2007 Journal of biochemistry and molecular biology Vol.40 No.2
Despite considerable interest in the biologic processes of regeneration and stem cell activation, little is known about the genes involved in these transformative events. In a Hydra littoralis model of regeneration, we employed a rapid shotgun suppression subtractive hybridization strategy to identify genes that are uniquely expressed in regenerating tissue. With an adaptor-PCR based technique, 16 candidate transcripts were identified, 15 were confirmed unique to mRNA isolated from hydra undergoing regeneration. Of these, 6 were undescribed in GenBank and allied expressed sequence tag (EST) databases (GenBank + EMBL + DDBJ + PDB and the Hydra EST database). BLAST analysis of these sequences identified remarkably similar sequences in anonymous ESTs found in a wide variety of animal species.
( Harinder Singh ),( Deepti Appukuttan ),( Sang Yong Lim ) 한국미생물 · 생명공학회 2014 Journal of microbiology and biotechnology Vol.24 No.8
The present study shows that DR1114 (Hsp20), a small heat shock protein of the radiationresistant bacterium Deinococcus radiodurans, enhances tolerance to hydrogen peroxide (H2O2) stress when expressed in Escherichia coli. A protein profile comparison showed that E. coli cells overexpressing D. radiodurans Hsp20 (EC-pHsp20) activated the redox state proteins, thus maintaining redox homeostasis. The cells also showed increased expression of pseudouridine (psi) synthases, which are important to the stability and proper functioning of structural RNA molecules. We found that the D. radiodurans mutant strain, which lacks a psi synthase (DR0896), was more sensitive to H2O2 stress than wild type. These suggest that an increased expression of proteins involved in the control of redox state homeostasis along with more stable ribosomal function may explain the improved tolerance of EC-pHsp20 to H2O2 stress.
Bijal Kottukkal Bahuleyan,안인용,Vinukrishnan Appukuttan,이소현,하창식,김일,서홍석 한국고분자학회 2010 Macromolecular Research Vol.18 No.7
A series of tridentate cobalt complexes of the general formula [RN(CH2)2N]=An=[N(2,6-C6H3iPr)](R=Me, Et, iPr; An=acenaphthenequinone) have been synthesized. All complexes were active towards ethylene oligomerization,showing activities exceeding 104 g-oligomer/mol-Co·h·bar in the presence of a methylaluminoxane co-catalyst. 1-Butene and trans-2-hexene were the major oligomer fractions obtained.