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91.
Israel V. Muthu Vijayan Enoch Meenakshisundaram Swaminathan 《Journal of inclusion phenomena and macrocyclic chemistry》2005,53(3):149-154
The absorption and fluorescence spectral characteristics of 2-aminodiphenylsulphone (2ADPS) have been investigated in the presence of β-cyclodextrin (β-CDx) in water. Dual emission is observed upon the complexation of 2ADPS in β-CDx. The stoichiometry of the host:guest inclusion complex is found to be 2:1. Steady state and time-resolved fluorescence spectral analysis support the formation of 2:1 complex between β-CDx and 2ADPS. The large enhancement in fluorescence intensity of twisted intramolecular charge transfer (TICT) band in aqueous β-CDx solution is due to the decrease in non-radiative processes. The ground and the excited state pKa values for the monocation-neutral equilibrium of 2ADPS in β-CDx are found to be different from the pKa values in aqueous solution. In the presence of β-CDx, 2ADPS is found to be less basic in the ground and the excited states. 相似文献
92.
Vijayan K Discher DE Lal J Janmey P Goulian M 《The journal of physical chemistry. B》2005,109(30):14356-14364
Alamethicin is a well-studied channel-forming peptide that has a prototypical amphipathic helix structure. It permeabilizes both microbial and mammalian cell membranes, causing loss of membrane polarization and leakage of endogenous contents. Antimicrobial peptide-lipid systems have been studied quite extensively and have led to significant advancements in membrane biophysics. These studies have been performed on lipid bilayers that are generally charged or zwitterionic and restricted to a thickness range of 3-5 nm. Bilayers of amphiphilic diblock copolymers are a relatively new class of membranes that can have significantly different physicochemical properties compared with those of lipid membranes. In particular, they can be made uncharged, nonzwitterionic, and much thicker than their lipid counterparts. In an effort to extend studies of membrane-protein interactions to these synthetic membranes, we have characterized the interactions of alamethicin and several other membrane-active peptides with diblock copolymer bilayers. We find that although alamethicin is too small to span the bilayer, the peptide interacts with, and ruptures, thick polymer membranes. 相似文献
93.
M. Gopalakrishnan P. Sureshkumar V. Kanagarajan J. Thanusu 《Research on Chemical Intermediates》2007,33(6):541-548
Condensation of structurally diverse aldehydes including heterocyclic aldehydes, like furfural, with various amines in the
presence of calcium oxide affording the corresponding imines in solvent-free conditions in good to excellent yields under
microwave irradiation is described. A comparative study has been done under thermal conditions. The synergy between dry media
and microwave irradiation in this reaction is evaluated by condensing less electrophilic aldehydes with poorly nucleophilic
amines. The main advantages of this environmentally friendly protocol are the use of the non-toxic and inexpensive reagent
calcium oxide and the considerable rate enhancement in comparison with a thermal reaction. 相似文献
94.
Karthikeyan Gopalakrishnan Mohanraj Kuttappan Elango Kuppanagounder P. Girishkumar Krishnapillai 《Transition Metal Chemistry》2004,29(1):86-90
A series of LnIII–tetracycline complexes of the type [Ln(TC)Cl3]·2H2O [Ln = lanthanum, praseodymium, neodymium, samarium, gadolinium, terbium, dysprosium and yttrium; TC = tetracycline] have been synthesized and characterized by analytical, i.r., electronic, 1H-n.m.r. spectral studies, X-ray diffraction and thermogravimetric analysis. A pentagonal bipyramidal structure has been tentatively proposed for the new complexes. The ligand and the new complexes were tested in vitro to evaluate their activity against the bacteria Escherichia coli and Staphylococcus aureus. 相似文献
95.
Gopalakrishnan Vaidyanathan M. Todd Coolbaugh James F. Garvey 《Journal of Cluster Science》1991,2(3):183-201
The study of van der Waals clusters is an area of growing interest and is being widely studied for a number of reasons. The measurement of the ionization efficiency (IE) curves have yielded a wealth of information by enabling ionization and appearance energies of ions to be determined which are essential for the calculation of thermochemical data. In the case of van der Waals clusters, the measurement ofIE curves enables one to determine the qualitative trends in the ionization potentials as a function of cluster size. In additionIE curves have also offered valuable insight into ionization related processes occurring in clusters. This paper will cover some of the more recent studies of Penning ionization, exciton induced decay and Coulomb explosion in van der Waals clusters through the use of electron impactIE curves. 相似文献
96.
Nagarajan NS Rao RP Manoj CN Sethuraman MG 《Magnetic resonance in chemistry : MRC》2005,43(3):264-265
An alcoholic extract of Dalbergia sympathetica, on column chromatography, yielded a compound which analyzed for C(6)H(11)NO(3) (M(+) 145). The IR spectrum of the compound showed the presence of carbonyl and hydroxyl groups. PMR, (13)C and DEPT NMR spectral studies of the compound showed the presence of one N-methyl, two methine and two methylene groups. A quaternary carbon signal at delta 172.88 ppm was assigned to C-2 carbonyl of the compound. From all the above observations and also from the HMQC 2D NMR spectrum, the compound was identified as 3, 6-dihydroxy-N-methyl-2-piperidone. This is the first report of the natural occurrence of this compound from plant sources. 相似文献
97.
B. Viswanathan R. Gopalakrishnan R. Vetrivel 《Reaction Kinetics and Catalysis Letters》1982,18(1-2):209-212
Three different binding states of CO on cobalt surfaces have been identified by TPD studies. The energetics of these adsorption states and their relevance in Fischer-Tropsch synthesis are considered.
CO - . -.相似文献
98.
Estimation of <Superscript>90</Superscript>Sr activity in reprocessed uranium from the PUREX process
S. Ravi A. K. Deepa B. Surekha S. Susheela P. V. Achuthan S. Anil Kumar K. Vijayan U. Jambunathan S. K. Munshi P. K. Dey 《Journal of Radioanalytical and Nuclear Chemistry》2007,272(1):123-126
90Sr estimation in reprocessed uranium was carried out by a series of solvent extraction and carrier precipitation techniques
using strontium and lanthanum carriers. Fuming with HClO4 was used to remove 106Ru as RuO4. Three step solvent extraction with 50% tri-n-butyl phosphate in xylene in presence of small amounts of dibutyl phosphate
and thenoyl trifluoro acetone was carried out to eliminate uranium, plutonium, thorium and protactinium impurities. Lanthanum
oxalate precipitation in acid medium was employed to scavenge the remaining multivalent ions. Strontium was precipitated as
strontium oxalate in alkaline pH and 137 Cs was removed by washing the precipitate with water. A strontium recovery well above 70% was obtained. Final estimation
was carried out by radiometry using end window GM counter after drying the precipitate under an infra red lamp. The same procedure
was extended to the estimation of 90Sr in a diluted sample of the actual spent fuel solution. An additional lanthanum oxalate precipitation step was required
to remove the entire 144Ce impurity from this sample. This modified procedure was employed in the determination of 90Sr in a number of reprocessed uranium samples and the over all precision of the method was found to be well within ±10%. An
additional barium chromate precipitation step was necessary for the analysis of reprocessed uranium samples from high bumup
fuels to eliminate trace amounts of short lived 224Ra produced during the decay of 232U and its daughters as they interfere in the estimation of 90Sr. 相似文献
99.
We describe an investigation of Ba3MIIMIVWO9 oxides for MII = Ca, Zn, and other divalent metals and MIV = Ti, Zr. In general, a 1:2-ordered 6H (hexagonal, P63/mmc) perovskite structure is stabilized at high temperatures (1300 degrees C) for all of the Ba3MIITiWO9 oxides investigated. An intermediate phase possessing a partially ordered 1:1 double perovskite (3C) structure with the cation distribution, Ba2(Zn2/3Ti1/3)(W2/3Ti1/3)O6, is obtained at 1200 degrees C for Ba3ZnTiWO9. Sr substitution for Ba in the latter stabilizes the cubic 3C structure instead of the 6H structure. A metastable Ba3CaZrWO9 that adopts the 3C (cubic, Fmm) structure has also been synthesized by a low-temperature metathesis route. Besides yielding several new perovskite oxides that may be useful as dielectric ceramics, the present investigation provides new insights into the complex interplay of crystal chemistry (tolerance factor) and chemical bonding (anion polarization and d0-induced distortion of metal-oxygen octahedra) in the stabilization of 6H versus 3C perovskite structures for the Ba3MIIMIVWO9 series. 相似文献
100.
Narayanan MC Rao PR Shanmugam NN Gopalakrishnan SM Devi K 《Natural product research》2007,21(10):903-909
The roots of Dalbergia horrida yielded two new isoflavanones, Dalhorridin (I) - 5,5'-dihydroxy-3',4'-methylenedioxy-5'-prenyl-6',6'-dimethyl-dihydropyrano(2',3' : 7,8)-isoflavanone and Dalhorridinin (II) - 5,7,5'-trihydroxy-3',4'-methylenedioxy-8-[5-methyl-2-(2-hydroxyisopropyl)-1,4-hexadienyl]isoflavanone along with two known isoflavones, Dalspinin and Dalspinosin. Preliminary biological screening of the enriched extract revealed that it showed analgesic, anti-inflammatory, CNS depressant and mild anti-bacterial properties. 相似文献