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331.
Ahmed Kamal S. Prabhakar N. Shankaraiah Ch. Ratna Reddy P. Venkat Reddy 《Tetrahedron letters》2008,49(22):3620-3624
A series of 1,2,3-triazole-containing pyrrolo[2,1-c][1,4]benzodiazepine dimers have been prepared efficiently by employing a ‘click’ chemistry protocol. This method involves 1,3-dipolar cycloaddition of terminal alkynes with organic azides using a Cu(I)-catalyst. Further, these molecules exhibited interesting DNA-binding affinity profiles. 相似文献
332.
Bhaskar G Prabhakar S Ramanjaneyulu GS Vairamani M Srinivasu VN Srinivas K 《Journal of mass spectrometry : JMS》2007,42(9):1194-1206
A series of meso-dialkyl, alkyl aryl and cycloalkyl calix(4)pyrroles (1-15) are studied under positive and negative ion electrospray ionization (ESI) conditions. The positive ion spectra show abundant [M + H](+) and [M + Na](+) ions and the negative ion spectra show the [M + Cl](-) (the Cl(-) ions from the solvent) and [M - H](-) ions. The collision induced dissociation (CID) spectra of [M + H](+), [M + Na](+), [M + Cl](-) and [M - H](-) ions are studied to understand their dissociation pathway and compared to that reported for M(+) under electron ionization (EI) conditions. The beta-cleavage process that was diagnostic to M(+) is absent in all the CID spectra of the ions studied under ESI. Dissociation of all the studied ions resulted in the fragment ions formed by sequential elimination of pyrrole (A) and/or dialkyl/alkyl aryl/cycloalkyl (B) groups involving hydrogen migration to pyrrole ring at each cleavage of A--B bond, which clearly reveals the arrangement of A and B groups in the calix(4)pyrroles. The source of hydrogen that migrates to pyrrole ring during A--B bond cleavage is investigated by the experiments on deuterated compounds and [M + D](+) ions; and confirmed that the hydrogen attached to pyrrole nitrogen, hydrogen on alpha-carbon of alkyl group and the H(+)/Na(+) ion that added during ESI process to generate [M + H](+)/[M + Na](+) ions involve in the migration. The yields of [M + Na](+) ions are found to be different for the isomeric meso-cycloalkyl compounds (cycloheptyl, and 2-, 3- and 4-methyl cyclohexyl) and for normal and N-confused calix(4)pyrroles. The isomeric methyl and 3-hydroxy/4-hydroxy phenyl calix(4)pyrroles show specific fragmentation pattern during the dissociation of their [M - H](-) ions. 相似文献
333.
Shinde Shivkanya Bhushan Prabhakar Ghosh Swatilekha 《Journal of Solid State Electrochemistry》2022,26(12):2817-2828
Journal of Solid State Electrochemistry - Nickel–Tin (Ni–Sn) film was fabricated by aluminum (Al) induced electroless process on copper foils as a current collector. This film was... 相似文献
334.
Nirmal Prabhakar Pratima R. Solanki Ajeet Kaushik M. K. Pandey B. D. Malhotra 《Electroanalysis》2010,22(22):2672-2682
We have prepared nanocomposite films comprising of 3‐glycidoxypropyltrimethoxysilane (GOPS) and iron‐oxide (Fe3O4) onto indium‐tin‐oxide (ITO) glass plate for covalent immobilization of 21‐mer peptide nucleic acid (PNA). These films have been characterized using contact angle, atomic force microscopy (AFM), electrochemical techniques. The electrochemical response of the GOPS/ITO and Fe3O4‐GOPS/ITO electrodes has been investigated by hybridization with complementary, non‐complementary and one‐base mismatch using methylene blue as electrochemical indicator. The PNA/Fe3O4‐GOPS/ITO bioelectrode exhibits improved specificity and detection limit (0.1 fM) as compared to that of the PNA‐GOPS/ITO bioelectrode (0.1 pM). This PNA/Fe3O4‐GOPS/ITO electrode can be utilized for detection of hybridization with the complementary sequence in sonicated M. tuberculosis genomic DNA within 90 s of hybridization time. 相似文献
335.
Ramanjaneyulu GS Prabhakar S Bhaskar G Venkatesham A Nagaiah K Rao RN Soujanya Y Sastry GN 《Rapid communications in mass spectrometry : RCM》2007,21(21):3511-3519
A series of diastereomeric 4S,5S,6R/S-tetrahydropyrano- and 3S,4S,5R/S-tetrahydrofuranochromenylamine derivatives (a/b isomers; 1-26) has been studied under electron ionization (EI) and chemical ionization (CI) conditions. The EI mass spectra of all diastereomeric compounds show two characteristic fragment ions, of which one is formed by retro-Diels-Alder (RDA) reaction from the molecular ion, retaining the charge on the diene fragment, and the other [M-(HNAr)]+ ion by a simple radical loss. The RDA process is more favorable in all b isomers, whereas the radical loss is dominant in all a isomers; based on these two ions it is easy to differentiate the two diastereomers. The collision-induced dissociation (CID) spectra of all the molecular ions also show the same trend, which reflects the stereoselectivity in the formation of the two characteristic fragment ions. The results of theoretical calculations performed are in accordance with the experimental observations. The CI experiments (methane and isobutane) on all the diastereomeric compounds also enabled the differentiation of the isomers. 相似文献
336.
Lakshmi VV Prabhakar S Murty MR Vairamani M 《Rapid communications in mass spectrometry : RCM》2007,21(23):3937-3945
Oxidative reactions of VX type compounds and N,N-dialkylaminoethane-2-thiols that are precursors for VX compounds produce N,N-dialkylaminoethane-2-sulphonic acids, N(R(1))(R(2))-CH(2)-CH(2)SO(3)H (where R(1) and R(2) = methyl, ethyl, n-propyl and isopropyl, 1-10), as the degradation products, and these degradation products are considered as markers for the detection of chemicals listed in the schedules of Chemical Weapons Convention (CWC) chemicals. Off-site detection of such degradation products in aqueous samples is an important task in the verification of CWC-related chemicals. Here we report a simple method involving the direct analysis of aqueous samples using positive and/or negative ion electrospray ionization (ESI) for the screening, detection and identification of N,N-dialkylaminoethane-2-sulphonic acids, avoiding sample preparation and chromatographic steps. The positive ion ESI mass spectra of all the compounds result in abundant [M+Na](+) ions, and the negative ion spectra show abundant [M-H](-) ions to confirm their molecular weight. The collision-induced dissociation spectra of [M+Na](+) and [M-H](-) give characteristic product ions by which it is easy to detect and identify all the studied N,N-dialkylaminoethane-2-sulphonic acids including those of isomeric compounds. The method is successfully applied to detect the spiked chemical, N,N-diisopropylaminoethane-2-sulphonic acid, present in a water sample received in a proficiency test. 相似文献
337.
Prabhakar Tirumani S. Venu G. Sridhar M. Praveen kumar A. V. Rajashekhar 《Natural product research》2018,32(11):1295-1298
Hemidesmus indicus (L.) R. Br. was extensively used as hypoglycaemic agent and significance of this plant on secondary complications of diabetes remained unknown. The present study was to investigate the anti-cataractous activity of H. indicus against streptozotocin (STZ)-induced diabetic cataract in rodent model. Root extracts have been prepared and tested for inhibition of rat lens aldose reductase (AR) activity. In addition, its pharmacological potential has been investigated in STZ-induced diabetic cataract. Methanol extract of H. indicus-inhibited AR activity in vitro decreased the blood glucose levels, inhibited the AR activity and delayed the onset and progression of cataract in a dose-dependent manner in in vivo and the antioxidant markers have been normalised. Our results demonstrate that H. indicus has decrease the osmotic stress by inhibiting the AR activity and prevented the loss of antioxidants and delayed the progression of diabetic cataract in STZ-induced diabetic rats. 相似文献
338.
Bhaskar G Chary MA Kumar MK Syamasundar K Vairamani M Prabhakar S 《Rapid communications in mass spectrometry : RCM》2005,19(11):1536-1544
The complexes of transition-metal ions (M2+, where M = Fe, Co, Ni, Cu, Zn, Cd, and Hg) with 2-acetylbenzimidazolethiosemicarbazone (L) are studied under electrospray ionization (ESI) conditions. The ESI mass spectra of Fe and Co complexes showed the complex ions corresponding to [M+2L-2H]+, and those of Ni and Zn complexes showed [M+2L-H]+ ions, wherein the metal/ligand ratio is 1:2 and the oxidation state of the central metal ion is +3 in the case of Fe and Co and +2 in the case of Ni and Zn. The Cd and Cu complexes showed preferentially 1:1 complex ions, i.e., [M+L-H]+ or [M+L+Cl]+, whereas Hg formed both 1:1 and 1:2 complex ions. During formation of the above complex ions one or two ligands are deprotonated after keto-enol tautomerism, depending on the nature and oxidation state of central metal ion. The structures and coordination numbers of the metal ions in the complex ions were studied by their collision-induced dissociation spectra and ion-molecule reactions with acetonitrile or propylamine in the collision cell. Based on these results it is concluded that Fe, Co, Ni and Zn form stable octahedral complexes, whereas tetrahedral or square planar complexes are formed preferentially for other metals. In addition, the Cu complex showed a [2L+2Cu-3H]+ ion with a Cu-Cu bond. 相似文献
339.
Kumar MK Rao JS Prabhakar S Vairamani M Sastry GN 《Chemical communications (Cambridge, England)》2005,(11):1420-1422
Electrospray ionisation mass spectrometry studies and quantum chemical calculations indicate that bidentate ligation of Li+ ion to the diamines leads to symmetric bridging and exhibits contrasting relative affinity orderings compared to that of proton for alpha,omega-diamines. 相似文献
340.
In this DFT study, a mechanism of the oxidation of methionine (Met) amino acid residue catalyzed by the metal (Cu2+, Zn2+, and Fe3+) bound amyloid beta (Aβ) peptide has been proposed. Based on experimental information, two different mechanisms: (1) stepwise and (2) concerted mechanisms for this important process have been investigated. The B3LYP calculations suggest that in the stepwise mechanism, the two separate pathways leading to the same sulfoxide product [Met(O)] go through prohibitively high barriers of 27.3 and 35.1 kcal/mol, therefore it is ruled out. In the concerted mechanism, the Cu2+‐Aβ complex has been found to be the most efficient catalyst with the computed barrier of 14.3 kcal/mol. The substitutions of Cu2+ by Zn2+ and Fe3+ increase barriers to 19.6 and 16.9 kcal/mol, respectively and make the reaction thermodynamically less favorable. It was also found that, in comparison with the cysteine (Cys) residue, Met is more susceptible toward oxidation. Its substitution with Cys slightly increased the barrier to 15.8 kcal/mol for the Cu2+‐Aβ complex. © 2008 Wiley Periodicals, Inc. J Comput Chem 2009 相似文献