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P Bahadur

Publications and source records attributed to P Bahadur.

15 recordsLinked to original sources
PubMed2006

A phenol-induced structural transition in aqueous cetyltrimethylammonium bromide solution.

The effect of phenol on the structure of micellar solution of a cationic surfactant, cetyltrimethylammonium bromide (CTAB) was investigated using viscosity, dynamic light scattering (DLS), small angle neutron scattering (SANS) and nuclear magnetic resonance (NMR) techniques. The relative viscosity and apparent hydrodynamic diameters of the micelles in CTAB solution increase initially and then decrease with addition of phenol. SANS studies indicate a prolate ellipsoidal structure of the micelles. The axial ratio of the prolate ellipsoidal micelles increases and then decreases with addition of phenol, consistently with DLS and viscosity measurements. NMR studies confirm the solubilization of phenol to the palisade layer and growth of the micelles at high concentration of phenol as revealed from the broadening of peaks.

Journal Article↗
PubMed2005

Interaction of cationic surfactants with carboxymethylcellulose in aqueous media.

We have examined the polymer-surfactant interaction in mixed solutions of the cationic surfactants, i.e., dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, tetradecyltriphenylphosphonium bromide, and tetradecylpyridinium bromide and a semiflexible anionic polyelectrolyte carboxymethylcellulose in water and aqueous salt solutions by various techniques: tensiometry, viscosimetry or ion-selective electrode method, and dynamic light scattering. We have investigated the effect of varying surfactant chain length, head group size, counterion, and ionic strength on the critical aggregation concentration (CAC) of mixed polymer surfactant systems and the collapse of the polymer molecule under different solution conditions. The CAC decreases with increasing alkyl chain length. Above a certain surfactant concentration, mixed aggregates start growing until their macroscopic phase separation. The growth is more rapid with greater surfactant tail length and with increasing head group size. This is attributed in both cases to the increasing hydrophobic interaction between polymer and surfactant. Among surfactants with monovalent halide counterions, iodide induces the strongest binding, reflected by the onset of growth of the mixed aggregates at low surfactant concentration. This is perhaps related to the decreasing hydration of the counterion from chloride to iodide. The surfactant concentration at which the viscosity of the solution starts to decrease sharply is smaller than the CAC, and probably reflects polymer chain shrinkage due to noncooperative binding.

Journal Article↗
PubMed2005

Concentration, temperature, and salt-induced micellization of a triblock copolymer Pluronic L64 in aqueous media.

The effect of copolymer concentration, temperature, and sodium halides (NaI, NaBr, NaCl, and NaF) on micellization and micellar properties of a poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) amphiphilic copolymer (Pluronic L64: EO13PO30EO13), was examined by different methods such as dye spectral change, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), small angle neutron scattering (SANS), dynamic light scattering (DLS), viscosity, and cloud point (CP). Temperature/polymer concentration/salt dependent aggregation behavior of L64 was observed. The data on critical micelle concentration (CMC), critical micelle temperature (CMT), (CP), micelle size, and shape are reported. The Fourier transform infrared (FTIR) showed temperature dependent changes in C-O-C stretching variation band towards higher wave numbers and broadening of band width during the micellization process; this was attributed to increase in proportion of the anhydrous methyl groups, while the proportion of the hydrated methyl groups was decreased. Differential scanning calorimetry (DSC) provides CMTs and CPs from the same experiment. CMC values derived from dye spectral change, decrease significantly with the addition of salt. The increases in salt/copolymer concentration lower the onset temperature of micellization (CMT). Halide anions influence both CMT and CP in the order of F- > Cl- > Br- > I- when total salt and copolymer concentration kept constant. SANS results show the increase of inter-micellar interaction due to the increase in temperature/salt concentration; this is supported by viscosity data.

Calorimetry, Differential Scanning↗
PubMed1989

Stability and kinetic behaviour of some enzymes in surfactant environment.

The interaction of alpha-chymotrypsin, invertase, alcohol dehydrogenase and alkaline phosphatase with some ionic and non-ionic surfactants, viz. sodium dodecyl sulphate, dioctyl sodium sulphosuccinate, hexadecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide and Triton X-100, has been examined by studying the effect of varying surfactant concentrations on enzyme activities as well as by determining the time-dependent inactivation and the time-independent inhibition. The kinetic parameters, Km and Vmax, for alpha-chymotrypsin-catalysed reaction in presence of sodium dodecyl sulphate were evaluated. Anionic surfactants markedly decreased enzyme activity, whereas cationic surfactants were less effective. Nonionics showed no effect. This change in enzyme activity was also dependent on the nature of enzyme.

Alcohol Dehydrogenase↗
PubMed1988

Effect of short course chemotherapy on salivary paracetamol elimination.

1. Salivary elimination of paracetamol was studied in six male pulmonary tuberculosis patients on short course chemotherapy. 2. Peak paracetamol concentration showed a steady decrease at the end of first week and continued until the end of the study. 3. The elimination half-life of paracetamol decreased 5 weeks after the therapy with a corresponding increase in the clearance rate. 4. Adjustment of dosage of drugs that are metabolized by the microsomal enzymes may be required in patients on anti-tubercular drug regimen in which rifampicin is included.

Acetaminophen↗
PubMed1983

Serology of tuberculosis. II. Measurement of antibodies to Mycobacterium tuberculosis by a passive haemagglutination test in human tuberculosis.

A simple and sensitive passive haemagglutination (PHA) test has been evaluated in the serology of human tuberculosis. Double aldehyde stabilized red cells were sensitized with cell extracts and PPD antigens from M. tuberculosis (H37Rv) and used as reagents in the test. The study was conducted on sera from 71 bacteriologically confirmed cases of tuberculosis and their controls, inclusive of 59 healthy blood donors and 28 non-tuberculous chest disease patients. In addition, 318 random samples of sera and 107 finger prick blood samples collected on filter papers from apparently healthy people were examined. For comparative evaluation, tuberculous patients' sera were examined by enzyme linked immunosorbent assay (ELISA) and crossed immunoelectrophoresis (CIE). The distribution of IgG and IgM type antimycobacterial antibodies (AMA) in tuberculous patients' sera was evaluated by a modified PHA test. The results of the study indicated that the PHA test was a sensitive method for the quantitation of antibodies, which could be demonstrated in all groups of sera studied. The PHA test and ELISA with the antigens used were not found to be specific enough for the serodiagnosis of tuberculosis; the results indicated the need to investigate several immunological approaches for this purpose. Both tests did differentiate between the mean AMA levels of tuberculous patients and their controls and both showed treated and relapsed cases of tuberculosis to contain higher serum levels of antibodies than did new cases. Both tests were found to be more sensitive than CIE with the intermediate gel technique. The PHA test was found to be sensitive enough for the measurement of antibodies in finger-prick blood samples, indicating its potential for field studies.

Antibodies, Bacterial↗