56 research outputs found
The importance of keto-enol tautomerism in alloxan. A semi-empirical quantum mechanical study
1148-115
Triazole-based C3-symmetric multivalent dendritic architecture as Cu(II) ion sensor
C3-symmetric triazole-based multivalent dendritic architecture having uniform aromatic core and branches has been employed to study its metal binding ability towards Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) ions. The dendritic architecture is found to exhibit a high affinity for Cu(II) ions and formed a solid complex with a blue shift in the dd-band of Cu(II) chloride. X-band EPR spectra at low temperature has supported a distorted tetrahedral geometry for the complex. The complex has displayed quasi-reversible redox waves in cyclic voltammetry (CV). DFT calculations have shown that Cu(II) has a high affinity for the dendritic structure, leading to high complexation energies of the order of -25 eV, showing that the complexation reactions are highly exothermic. The binding constant (K) for the Cu(II) complex has been determined using a fluorescence titration method
Atomic and molecular spectroscopy: basic concepts and applications
Spectroscopy is the study of electromagnetic radiation and its interaction with solid, liquid, gas and plasma. It is one of the widely used analytical techniques to study the structure of atoms and molecules. The technique is also employed to obtain information about atoms and molecules as a result of their distinctive spectra. The fast-spreading field of spectroscopic applications has made a noteworthy influence on many disciplines, including energy research, chemical processing, environmental protection and medicine. This book aims to introduce students to the topic of spectroscopy. The author has avoided the mathematical aspects of the subject as far as possible; they appear in the text only when inevitable. Including topics such as time-dependent perturbation theory, laser action and applications of Group Theory in interpretation of spectra, the book offers a detailed coverage of the basic concepts and applications of spectroscopy
Methyl nitrene: Thermochemistry and kinetics of its rearrangement to methyleneimine
308-312The thermal unimolecular isomerisation of methylnitrene to methyleneimine has been studied, and the macroscopic thermodynamic and kinetic properties have been calculated using the vibrational frequencies and rotational constants evaluated theoretically. The high pressure rate constants have been calculated and the fall-off behaviour has been studied using the calculated reactant and transition state properties. Kinetic isotope effects on the reaction have also been studied. The effects of fluorine substitution on the thermochemical and kinetic parameters have also been investigated
Structures of some Hoechst analogues in gas phase and in aqueous solution
1929-1936Four Hoechst analogues have been examined
in this work to determine their conformational preferences in three different
environments, viz. gas phase, within the DNA minor groove and aqueous phase. Rotations
about all the three single bonds, namely those connecting the phenol ring to a benzimidazole
ring, the two benzimidazole rings, and a benzimidazole
ring to the N-methylpiperazine ring
have been considered. It is found that the optimum conformation necessary for binding
to the DNA minor groove is easily attained, especially in aqueous solution
Resveratrol: A Polyphenol with Multiple Health Benefits
In today's stressful world, there is an urgent need for simple drugs to combat lifestyle diseases like heart diseases and diabetes, which are assuming epidemic proportions. Resveratrol is one such molecule. It is the molecule behind a phenomenon known as the “French paradox”, i.e. the observation of low incidence of heart disease in France in spite of a diet rich in fats. It is a major component of red wine, also part of the French diet. Resveratrol is a naturally occurring polyphenolic phytoalexin, derived from the skin of plants, which has gained interest exponentially in recent years. This molecule is found to have a number of health benefits, including prevention of cardiovascular and neurodegenerative diseases. It is known to have anti-inflammatory, antiviral, anti-platelet aggregation and many other health beneficial properties. It has found tremendous clinical application. Among its wide range of biological activities, the most striking activity is of cancer and tumor initiation prevention. This molecule has been shown to have a positive effect on metabolism and improvement in overall health of an individual and can probably be used as an anti ageing drug alone or in combination with some other medication. These remarkable properties have elicited a huge interest of researchers in this molecule. It has been reported to interfere with some major cellular signaling pathways which are involved in cell survival or cell death. Careful insights into these cellular pathways and their interaction with resveratrol could pave the way for future drug designing for treatment of diseases. Here we have tried to review the maximum possible biological properties of resveratrol cited so far in the literature
Semiempirical study of tautomerism in alloxan
103-111A comparative semiempirical study of
tautomerism in alloxan is performed with a view to understand the areas of applicability
and limitations of the three methods, MNDO, AM1 and PM3. The results are also
compared with an ab initio study. It is found that the MNDO method
overestimates the stability of lactim forms, while AM1 method seems to
underestimate their stabilities. All
methods indicate that the tetraketo form is the most stable, followed by the
monohydroxy forms. While the PM3 method seems to give the best results
regarding relative stabilities of tautomers, it fails in reproducing experimental
geometries and charge distributions and in explaining the chemical and
biological reactivity of alloxan. The
calculated MNDO and AM1 charge densities
agree with the results of an ab initio study and with experimental
estimates, and are thus able to explain the absence of hydrogen bonding in the
crystal structure of alloxan. Nucleophilic attack by water at 5-position leads to
a significant increase in the stabilities of the tetraketo and 2-hydroxy forms.
Thus, due to the
absence of hydrogen bonding interactions
in the crystal structure of alloxan, the MNDO geometries are in closest
agreement with experiment, and the charge densities are also consistent with
experimentally estimated ones
C<sub>3</sub>H<sub>4</sub>: Effect of fluorine substitution on structures
1492-1499The molecular structures and stabilities of
the lowest singlet states of the five most stable isomers of C3H3F,
derived from fluorine substitution at various positions in methylacetylene, allene
and cyclopropene, have been studied by the MNDO method. The structures and stabilities
of the lowest singlet and triplet states of various monofluoro-substituted carbenes
derived by fluorine substitution at various positions in propenylidene, cyclopropylidene
and vinylmethylene have also been investigated. Fluoroallene is found to be the
most stable structure. Fluorine substitution in the stable systems does not lead
to appreciable change in geometries, while for the carbenes, large variations
in geometry are observed. In general,
fluorine substitution results in the withdrawal
of a large amount of electron density from the a carbon
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