Effects of 2, 4-Dichlorophenoxyacetic Acid on the in vitro growth of explants (Clerodendron spp.)

Callus cultures and suspension cultures began with pieces of tissues and cells fromthe leaf but culture conditions were manipulated to create an unorganized state. Theinitiation of callus was induced from dicotyledonous tissue explants (Clerodendron spp.) firstby preparing MS basal medium and then by adding varying concentrations of 2, 4-Dichlorophenoxyacetic Acid or 2, 4-D. Growth was observed after each week for a period of3 weeks and observations were documented. After all the observations were noted down;subsequent analysis and interpretation of the results followed. This led to a valid scientificconclusion for the whole study process. Though there was disturbance due to heavy bacterialcontamination in majority of the petriplates, but the effect of plant-status and environmentalfactors on callus initiation cannot be fully ignored. Growth response studied was morevigorous in low concentrations of 2, 4-D as compared to higher levels

Shear thinning in dilute and semidilute solutions of polystyrene and DNA

The viscosity of dilute and semidilute unentangled DNA solutions, in steady simple shear flow, has been measured across a range of temperatures and concentrations. For polystyrene solutions, measurements of viscosity have been carried out in the semidilute unentangled regime, while results of prior experimental measurements in the dilute regime have been used for the purpose of data analysis, and for comparison with the behaviour of DNA solutions. Interpretation of the shear rate dependence of viscosity in terms of suitably defined non-dimensional variables, is shown to lead to master plots, independent of temperature and concentration, in each of the two concentration regimes. In the case of semidilute unentangled solutions, defining the Weissenberg number in terms of a concentration dependent large scale relaxation time is found not to lead to data collapse across different concentrations. On the other hand, the use of an alternative relaxation time, with the concentration dependence of a single correlation blob, suggests the existence of universal shear thinning behaviour at large shear rates.Comment: 24 pages, 13 figures, supplementary material (see ancillary directory), to appear in Journal of Rheolog

The viscosity radius in dilute polymer solutions: Universal behaviour from DNA rheology and Brownian dynamics simulations

The swelling of the viscosity radius, $\alpha_\eta$, and the universal viscosity ratio, $U_{\eta R}$, have been determined experimentally for linear DNA molecules in dilute solutions with excess salt, and numerically by Brownian dynamics simulations, as a function of the solvent quality. In the latter instance, asymptotic parameter free predictions have been obtained by extrapolating simulation data for finite chains to the long chain limit. Experiments and simulations show a universal crossover for $\alpha_\eta$ and $U_{\eta R}$ from $\theta$ to good solvents in line with earlier observations on synthetic polymer-solvent systems. The significant difference between the swelling of the dynamic viscosity radius from the observed swelling of the static radius of gyration, is shown to arise from the presence of hydrodynamic interactions in the non-draining limit. Simulated values of $\alpha_\eta$ and $U_{\eta R}$ are in good agreement with experimental measurements in synthetic polymer solutions reported previously, and with the measurements in linear DNA solutions reported here.Comment: 19 pages, 14 figures, two column, Supporting Information added, to appear in Macromolecule

Universal solvent quality crossover of the zero shear rate viscosity of semidilute DNA solutions

The scaling behaviour of the zero shear rate viscosity of semidilute unentangled DNA solutions, in the double crossover regime driven by temperature and concentration, is mapped out by systematic experiments. The viscosity is shown to have a power law dependence on the scaled concentration $c/c^*$, with an effective exponent that depends on the solvent quality parameter $z$. The determination of the form of this universal crossover scaling function requires the estimation of the $\theta$ temperature of dilute DNA solutions in the presence of excess salt, and the determination of the solvent quality parameter at any given molecular weight and temperature. The $\theta$ temperature is determined to be $T_\theta \approx 15^\circ$ C using static light scattering, and the solvent quality parameter has been determined by dynamic light scattering.Comment: 39 pages, 26 figures, accepted in Journal of Rheology. Includes supplemental material

Double-stranded DNA as a model polymer: validation through rheological characterization

Solutions of double-stranded DNA (ds-DNA) have been investigated in the presence of excess salt to represent a model neutral polymer system. However, very recently, there have also been some contrary discussions regarding the suitability of using ds-DNA as a model polymer, based on scaling arguments and simulations. Here, we report systematic experimental investigations of dilute and semidilute unentangled ds-DNA solutions, to test the hypothesis that ds-DNA is a model polymer. In addition, we have meticulously characterized the behaviour of ds-DNA solutions far from equilibrium, in shear and extensional flows. In order to study the behaviour of ds-DNA to compare with well known results from neutral polymers, we first characterize its solutions close to equilibrium. We use the solvent quality parameter z and the dimensionless concentration c/c* (where c* is the overlap concentration), as the scaling variables. We have determined the Theta-temperature of DNA in Tris-EDTA buffer under excess salt conditions to be around 15 degree Celsius, and provide the formula to determine z for DNA of any molecular weight at any temperature above the theta temperature. We also show that the temperature crossover for dilute DNA solutions of various molecular weights (from 2.9 to 289 kilobasepairs) for the second virial coefficient, the hydrodynamic radius and the viscosity radius agree with the scaling behaviour of neutral synthetic polymers. The scaling behavior of the zero shear rate viscosity of semidilute DNA solutions, in the double crossover regime driven by temperature and concentration, is shown to have a power law dependence on the scaled concentration c/c*, with an effective exponent that depends on z, in agreement with reported Brownian dynamics simulations of flexible polymer chains. Away from equilibrium, in shear flow, the shear rate dependence of viscosity for semidilute and dilute DNA solutions, at various temperatures and concentrations, can be collapsed onto master curves when interpreted in terms of a different relaxation time based Weissenberg number. In extensional flow, the concentration dependence of the steady state uniaxial extensional viscosities of semidilute DNA solutions has been studied and compared with theoretical predictions. The material functions obtained in this work will also provide benchmark data that are useful for the characterization of industrially important semidilute systems. Equilibrium rheological characterization carried out on dilute and semidilute DNA solutions, investigated under excess salt conditions, show a remarkable agreement with other neutral synthetic polymers, asserting that DNA can be used as a model polymer for rheological studies.Thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy of the Indian Institute of Technology Bombay, India and Monash University, Australia

Double-stranded DNA as a model polymer: validation through rheological characterization

Solutions of double-stranded DNA (ds-DNA) have been investigated in the presence of excess salt to represent a model neutral polymer system. However, very recently, there have also been some contrary discussions regarding the suitability of using ds-DNA as a model polymer, based on scaling arguments and simulations. Here, we report systematic experimental investigations of dilute and semidilute unentangled ds-DNA solutions, to test the hypothesis that ds-DNA is a model polymer. In addition, we have meticulously characterized the behaviour of ds-DNA solutions far from equilibrium, in shear and extensional flows. In order to study the behaviour of ds-DNA to compare with well known results from neutral polymers, we first characterize its solutions close to equilibrium. We use the solvent quality parameter z and the dimensionless concentration c/c* (where c* is the overlap concentration), as the scaling variables. We have determined the Theta-temperature of DNA in Tris-EDTA buffer under excess salt conditions to be around 15 degree Celsius, and provide the formula to determine z for DNA of any molecular weight at any temperature above the theta temperature. We also show that the temperature crossover for dilute DNA solutions of various molecular weights (from 2.9 to 289 kilobasepairs) for the second virial coefficient, the hydrodynamic radius and the viscosity radius agree with the scaling behaviour of neutral synthetic polymers. The scaling behavior of the zero shear rate viscosity of semidilute DNA solutions, in the double crossover regime driven by temperature and concentration, is shown to have a power law dependence on the scaled concentration c/c*, with an effective exponent that depends on z, in agreement with reported Brownian dynamics simulations of flexible polymer chains. Away from equilibrium, in shear flow, the shear rate dependence of viscosity for semidilute and dilute DNA solutions, at various temperatures and concentrations, can be collapsed onto master curves when interpreted in terms of a different relaxation time based Weissenberg number. In extensional flow, the concentration dependence of the steady state uniaxial extensional viscosities of semidilute DNA solutions has been studied and compared with theoretical predictions. The material functions obtained in this work will also provide benchmark data that are useful for the characterization of industrially important semidilute systems. Equilibrium rheological characterization carried out on dilute and semidilute DNA solutions, investigated under excess salt conditions, show a remarkable agreement with other neutral synthetic polymers, asserting that DNA can be used as a model polymer for rheological studies. Thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy of the Indian Institute of Technology Bombay, India and Monash University, Australia

Bioprocessing of Functional Ingredients from Flaxseed

Flaxseeds (Linum usitatissimum L.) are oilseeds endowed with nutritional constituents such as lignans, lipids, proteins, fibre, carbohydrates, and micronutrients. Owing to their established high nutritional profile, flaxseeds have gained an established reputation as a dietary source of high value functional ingredients. Through the application of varied bioprocessing techniques, these essential constituents in flaxseeds can be made bioavailable for different applications such as nutraceuticals, cosmetics, and food industry. However, despite their food and health applications, flaxseeds contain high levels of phytotoxic compounds such as linatine, phytic acids, protease inhibitors, and cyanogenic glycosides. Epidemiological studies have shown that the consumption of these compounds can lead to poor bioavailability of essential nutrients and/or health complications. As such, these components must be removed or inactivated to physiologically undetectable limits to render flaxseeds safe for consumption. Herein, critical description of the types, characteristics, and bioprocessing of functional ingredients in flaxseed is presented