Electron transfer interaction of dihydroxyquinones with amine quenchers: dependence of the quenching kinetics on the aliphatic and aromatic nature of the amine donors

Studies on the electron transfer (ET) interaction of 1,4-dihydroxy-9,10-anthraquinone and 6,11-dihydroxy-5,12-naphthacenequinone with aliphatic and aromatic amine (AlA and ArA, respectively) donors have been investigated in acetonitrile solutions. Steady-state (SS) measurements show quenching of the quinone fluorescence by amines, without indicating any change in the shape of the fluorescence spectra. No significant change in the absorption spectra of the quinones is also observed in the presence of the amines. For all the quinone-amine pairs, the bimolecular quenching constants (kq) estimated from SS and time-resolved measurements are found to be similar. Variation in the kq values with the oxidation potentials of the amines indicates the involvement of the ET mechanism for the quenching process. A reasonably good correlation between the kq values and the free energy changes (deltaG0) for the ET reactions following Marcus' outer-sphere ET theory also supports this mechanism. It is seen that for both the quinone-ArA and quinone-AlA systems, the kq values initially increase and then get saturated at some diffusion-controlled limiting values (kqDC) as deltaG0 values gradually become more negative. Interestingly, however, it is seen that the kqDC value for the quinone-AlA systems is substantially lower than that for quinone-ArA systems. Such a large difference in the kqDC values between quinone-AlA and quinone-ArA systems is quite unusual. Present results have been rationalized based on the assumption that an orientational restriction is imposed for the encounter complexes in quinone-AlA systems to undergo ET reactions, which arises because of the localized (at amino nitrogen) shapes of the highest-occupied molecular orbitals (HOMO) of AlA in comparison to the pi-like HOMO of the ArA.

Excited singlet (S1)-state interactions of Nile red with aromatic amines

Both steady-state (SS) and time-resolved (TR) studies show that the fluorescence of the dye Nile red (NR) is quenched by various aromatic amines (ArA). Bimolecular quenching constants (kq) from both SS and TR measurements are observed to match well, indicating that the interaction is dynamic in nature. The quenching interaction in the present systems has been attributed to electron transfer (ET) from ArA to excited NR, based on the variations in the kq values with the oxidation potentials of the amines. The kq values calculated within the framework of Marcus' outer-sphere ET theory at different free-energy changes (deltaG0) of the ET reactions match well with the experimental ones, supporting the ET mechanism in the systems studied. The reorganization energy (lambda) estimated from the correlation of the experimental and the calculated kq values is quite similar to the solvent reorganization energy (lambda(s)), calculated on the basis of the solvent dielectric continuum model along with the assumption that the reactants are the effective spheres. Although a modest error is involved in this lambda(s) calculation, the similarity in lambda and lambda(s) values suggests that the solvent reorganization plays a dominant role in governing the ET dynamics in the present systems.

Discriminative value of lipids and apolipoproteins in alcoholics

1. It is important to detect alcohol use in its early stages so that interventions can be planned effectively. In a bid to screen for alcohol use disorders various biochemical assessments have been advocated. 2. It has been seen that moderate to heavy alcohol consumption appears to elevate ApoA1 though the effect of alcohol consumption on ApoB is not well defined. 3. Present study was planned to evaluate the contribution of lipid profile and lipoprotein measures for the diagnosis of alcohol use disorder in 75 alcohol dependent and 45 normal healthy controls. 4. Based on the TC, TG, HDL/LDL-c, HDL-c/TC, ApoA1, ApoB, and ApoA1/ApoB a discriminant equation was developed for classification of alcohol dependent users (alcoholics) and non-users (non-alcoholics) 5. The discriminant equation resulted in 84.7% of subjects being correctly classified. (94.7% in non-users and 81.1% in alcohol dependent users as alcoholics).

Studies on the radiolytically produced transients of neutral red: triplet and reduced radicals

The spectral and kinetic properties of reduced radicals and the triplet state of neutral red (NR), a phenazine-based dye, have been investigated using pulse radiolysis technique. A mixed water-isopropanol-acetone solvent has been used to study the reduced radicals of NR for a wide pH range of about 1-13, due to limitation of solubility of the dye in aqueous solutions particularly above pH 8. From pH-dependent absorption studies it has been established that the reduced radicals of NR can exist in four different prototropic forms in solution. Three pKa values for the corresponding prototropic equilibria have been estimated. The formation and decay rate constants of reduced radicals have also been measured. The triplet state characteristics of the dye have been investigated in neat benzene solutions, both in the presence and in the absence of triplet sensitizers. The T1-->Tn absorption spectrum and decay kinetics of the triplet state have been measured. The triplet state energy (ET) of NR in benzene have been estimated to be within 36-42 kcal mol-1, using an energy transfer method.

Drug use in a rural community in bihar : some psychosocial correlates

Drug use has been an integral part of any culture. The use depends on many factors including the availability. In the present study the drug use in a rural community of Chotanagpur Plateau in the Ranchi district of Bihar is focussed. The sample consisted of 157 inhabitants above the age of 15 yrs of the village Boreya in Kanke block. A sample of drug users was compared with nondrug users of the same community on the measures of stressful life events and locus of control. The results indicate that besides tobacco alcohol in the form of locally brewed 'handia' (rice beer) and 'mahua' (made from mahua flowers) was used by 334 (28.87%) individuals. Cannabis was frequently used (25.15%) Harder drugs were not used at all. There was an increase in stressful life events in the year prior to the use of drugs. The increase in life events was especially seen in the elderly age group (35-50yrs). There was no difference in the locus of control scores between the users and the nonusers. The results indicate the role of significant life events in the current use of drugs.

A follow up study of schizoaffective psyohosis: an appraisal of socio-clinical and diagnostic aspects

Sociodemographic, clinical and outcome characteristics of 29 cases who had the diagnosis of schizoaffective psychosis were studied. On the basis of longitudinal course of the illness, 2 distinct subgroup of patients could be delineated. Patients with episodic illness were more akin to affective disorders while those with continuous course of illness were conceptually closer to schizophrenia. Concordance of the ICD-9 diagnosis of these patients with other well known diagnostic systems tike Research Diagnostic Criteria, DSM-III-R and proposed ICD-10 was studied. Advantages and limitations of these diagnostic systems with regard to the diagnosis of schizoaffective psychosis are discussed.