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Ch. Raji Reddy N. Kiranmai G. Dattatreya Sarma S. Chandrasekhar 《Tetrahedron letters》2007,48(2):215-218
The first use of hydroxylamine derivatives as the aminoxy equivalent of nucleophiles in palladium catalyzed addition to Baylis-Hillman acetate adducts is described. The reaction proceeds smoothly to give the substituted allyloxy amines in good yield and selectivity. 相似文献
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Molly Megraw Praveen Sethupathy Kiranmai Gumireddy Shane T. Jensen Qihong Huang Artemis G. Hatzigeorgiou 《Theoretical chemistry accounts》2010,125(3-6):593-598
In this study, we investigate whether miRNAs located within “host” protein-coding genes may regulate the expression of their host genes. We find that 43 of 174 miRNAs encoded within RefSeq genes are predicted to target their host genes. Statistical analysis of this phenomenon suggests that gene auto-regulation via miRNAs may be under positive selective pressure. Our analysis also indicates that several of the 43 miRNAs have a much lower expectation of targeting their host genes by chance than others. Among these examples, we identify miR-128b:ARPP-21 (cyclic AMP-regulated phosphoprotein, 21 kD) as a case in which both the miRNA and the target site are also evolutionarily conserved. We provide experimental support for this miRNA:target interaction via reporter silencing assays, and present evidence that this isoform-specific gene auto-regulation has been preserved in vertebrate species in order to prevent detrimental consequences of ARPP-21 over-expression in brain. 相似文献
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Dr. Tibor Szilvási Nanqi Bao Dr. Karthik Nayani Huaizhe Yu Dr. Prabin Rai Prof. Dr. Robert J. Twieg Prof. Dr. Manos Mavrikakis Prof. Dr. Nicholas L. Abbott 《Angewandte Chemie (International ed. in English)》2018,57(31):9665-9669
Surface‐supported liquid crystals (LCs) that exhibit orientational and thus optical responses upon exposure to ppb concentrations of Cl2 gas are reported. Computations identified Mn cations as candidate surface binding sites that undergo redox‐triggered changes in the strength of binding to nitrogen‐based LCs upon exposure to Cl2 gas. Guided by these predictions, μm‐thick films of nitrile‐ or pyridine‐containing LCs were prepared on surfaces decorated with Mn2+ binding sites as perchlorate salts. Following exposure to Cl2, formation of Mn4+ (in the form of MnO2 microparticles) was confirmed and an accompanying change in the orientation and optical appearance of the supported LC films was measured. In unoptimized systems, the LC orientational transitions provided the sensitivity and response times needed for monitoring human exposure to Cl2 gas. The response was also selective to Cl2 over other oxidizing agents such as air or NO2 and other chemical targets such as organophosphonates. 相似文献
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Prashanthi Y Kiranmai K Subhashini NJ Shivaraj 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(1):30-35
The metal complexes of Cu(II), Ni(II) and Co(II) with Schiff bases of 3-(2-hydroxy-3-ethoxybenzylideneamino)-5-methyl isoxazole [HEBMI] and 3-(2-hydroxy-5-nitrobenzylidene amino)-5-methyl isoxazole [HNBMI] which were obtained by the condensation of 3-amino-5-methyl isoxazole with substituted salicylaldehydes have been synthesized. Schiff bases and their complexes have been characterized on the basis of elemental analysis, magnetic moments, molar conductivity, thermal analysis and spectral (IR, UV, NMR and Mass) studies. The spectral data show that these ligands act in a monovalent bidentate fashion, co-ordinating through phenolic oxygen and azomethine nitrogen atoms. Chelates of Co(II), Ni(II) appear to be octahedral and Cu(II) appears to be distorted octahedral. To investigate the relationship between formation constants of binary complexes and antimicrobial activity, the dissociation constants of Schiff bases and stability constants of their binary metal complexes have been determined potentiometrically in aqueous solution at 30+/-1 degrees C and at 0.1 M KNO3 ionic strength and discussed. Antimicrobial activities of the Schiff bases and their complexes were screened. The structure-activity correlation in Schiff bases and their metal(II) complexes are discussed, based on the effect of their stability constants. It is observed that the activity enhances upon complexation and the order of activity is in accordance with stability order of metal ions. 相似文献
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We report herein the synthesis of cytotoxic cyanobactin, Wewakazole B through an efficient solution-phase approach. The key steps of the synthesis are the macrocyclic lactamization of linear dodecapeptide and construction of two hexapeptides with three different substituted oxazole rings. 相似文献
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The stereoselective total synthesis of (+)-cardiobutanolide, a polyhydroxylated natural product, is achieved in high yield through Lu and Guo diene synthesis, Sharpless asymmetric dihydroxylation, and one-pot deprotection-lactonization. The utility of a recyclable reagent system in PEG for asymmetric dihydroxylation is demonstrated. 相似文献
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Varela C Rittmann D Singh A Krumbach K Bhatt K Eggeling L Besra GS Bhatt A 《Chemistry & biology》2012,19(4):498-506
Mycolic acids are vital components of the cell wall of the tubercle bacillus Mycobacterium tuberculosis and are required for viability and virulence. While mycolic acid biosynthesis is studied extensively, components involved in mycolate transport remain unidentified. We investigated the role of large membrane proteins encoded by mmpL genes in mycolic acid transport in mycobacteria and the related corynebacteria. MmpL3 was found to be essential in mycobacteria and conditional depletion of MmpL3 in Mycobacterium smegmatis resulted in loss of cell wall mycolylation, and of the cell wall-associated glycolipid, trehalose dimycolate. In parallel, an accumulation of trehalose monomycolate (TMM) was observed, suggesting that mycolic acids were transported as TMM. In contrast to mycobacteria, we found redundancy in the role of two mmpL genes, in Corynebacterium glutamicum; a complete loss of trehalose-associated and cell wall bound corynomycolates was observed in an NCgl0228-NCgl2769 double mutant, but not in individual single mutants. Our studies highlight the role of mmpL genes in mycolic acid metabolism and identify potential new targets for anti-TB drug development. 相似文献
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Raju B Ramesh M Srinivas R Chandrasekhar S Kiranmai N Sarma VU 《Journal of the American Society for Mass Spectrometry》2011,22(4):703-717
A new class of positional isomeric pairs of -Boc protected oligopeptides comprised of alternating nucleoside derived β-amino
acid (β-Nda-) and L-amino acid residues (alanine, valine, and phenylalanine) have been differentiated by both positive and
negative ion electrospray ionization ion-trap tandem mass spectrometry (ESI-MS
n
). The protonated dipeptide positional isomers with β-Nda- at the N-terminus lose CH3OH, NH3, and C2H4O2, whereas these processes are absent for the peptides with L-amino acids at the N-terminus. Instead, the presence of L-amino
acids at the N-terminus results in characteristic retro-Mannich reaction involving elimination of imine. A good correlation
has been observed between the conformational structure of the peptides and the abundance of yn+ and bn+ ions in MS
n
spectra. In the case of tetrapeptide isomers that are reported to form helical structures in solution phase, no yn+ and bn+ ions are observed when the corresponding amide -NH- participates in the helical structures. In contrast, significant yn+ and bn+ ions are formed when the amide -NH- is not involved in the H-bonding. In the case of tetra- and hexapeptides, it is observed
that abundant bn+ ions are formed, presumably with stable oxazolone structures when the C-terminus of the bn+ ions possessed L-amino acid and the β-Nda- at the C-terminus appears to prevent the cyclization process leading to the absence
of corresponding bn+ ions. 相似文献
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