Effect of macromolecular crowding on the rate of diffusion-limited enzymatic reaction

The cytoplasm of a living cell is crowded with several macromolecules of different shapes and sizes. Molecular diffusion in such a medium becomes anomalous due to the presence of macromolecules and diffusivity is expected to decrease with increase in macromolecular crowding. Moreover, many cellular processes are dependent on molecular diffusion in the cell cytosol. The enzymatic reaction rate has been shown to be affected by the presence of such macromolecules. A simple numerical model is proposed here based on percolation and diffusion in disordered systems to study the effect of macromolecular crowding on the enzymatic reaction rates. The model qualitatively explains some of the experimental observations.      

Heteropogon contortus BL‐1 (Pilli Grass) and Elevated UV‐B Radiation: The Role of Growth,Physiological, and Biochemical Traits in Determining Forage Productivity and Quality

Exposure to elevated UV‐B (eUV‐B) is well known for its phytotoxicity, although studies made with UV‐B exposure and its impact on grasses are limited especially from tropical countries including India. In this study, responses of a valuable grass species, Heteropogon contortus BL‐1, were assessed under eUV‐B (over ambient UV‐B) at different growth stages. Damage caused by eUV‐B was observed in the form of membrane damage and loss of pigments at early stages of growth, whereas tannin, phenol, and protein contents showed their increments at all the growth stages, to overcome the imposed stress. Reducing sugar showed its decline at all the growth stages, whereas starch and sucrose contents were higher mostly at later ages of plant growth. eUV‐B caused a marked variations in anatomical structures with increase of mesophyll and spongy parenchymatous cells in leaves to reduce severity of irradiation, to maintain the growth and productivity. The study also highlights the significant negative influence of eUV‐B on the growth of H. contortus BL‐1 and its adaptive strategy to minimize the negative impacts. With the progression of age, plants although adopted to UV‐B stress with maintenance of productivity, but palatability of forage was affected due to increment of tannin content.     

Novel semiconducting iron–quinizarin metal–organic framework for application in supercapacitors*

We present conductivity data for a newly synthesised metal–organic framework FeQ, Fe(C₁₄H₆O₄).H₂O demonstrating significant electronic transport. The electrical conductivity of the material is expected to be through the π–π interaction of the ligand-quinizarin and is measured to be 1.73?×?10^?2?Scm^?1_. Its potential role as supercapacitor electrodes is discussed.     

New insight into the DNA binding studies,In-Vitro anti-cancer activity and molecular modelling of dioxo complexes of Molybdenum(VI) and Tungsten(VI) hydroxamic acids

The present study embodies the detail of interaction of Complex 1, Bis(N-phenyl-o-methoxybenzohydroxamato)Molybdenum(VI): [N-PMBHA-Mo(VI)] and Complex 2, Bis(N-phenylbenzohydroxamato)Tungsten(VI): [N-PBHA-W(VI)] with ct-DNA (Calf thymus-DNA) and its consequences by UV–Visible absorption spectroscopy, fluorescence spectroscopy, three-dimensional fluorescence spectroscopy, viscosity measurements and molecular docking. The intrinsic binding constant, K_b of complexes were determined which follows the order as complex 1 > complex 2 along with variation in shift and intensity for the complexes. Fluorescence spectroscopy applied for the determination of Stern–Volmer quenching constant, binding constant and the number of binding sites which reveals groove mode of binding. Non-radiative energy transfer between donor and acceptor molecule exposed by Förster energy transference theory (FRET) studies. The increase in the relative viscosity of ct-DNA with increasing the concentration of the complex 1 and complex 2 is also revealed. FTIR analysis also revealed that both the complexes interacted positively with bases and phosphates of ct-DNA. The docking studies complemented the experimental results revealing minor groove mode of binding for both the complexes. Finally, the in-vitro cytotoxicity studies indicate that the complexes have excellent anticancer activity against the breast cancer cell line, MCF-7, which could be a constructive guideline to produce new generations of anticancer agents.     

Computational study of buoyancy effects in a laminar starting jet

Vortical structures formed in evolving jets are important in applications such as fuel injection in diesel engines and fuel leaks. When the jet fluid is different from the ambient fluid, the buoyancy can play an important role in determining the jet flow structure, and hence, the entrainment and fluid mixing processes. In the present study, a jet of helium injected in air is investigated, with emphasis placed on delineating the buoyancy effects on vector–scalar fields during the starting phase. We utilize a computational model, previously validated to predict the flow field of low-density gas jets. The model incorporates finite volume approach to solve the transport equation of helium mass fraction coupled with conservation equations of mixture mass and momentum. Computations were performed for a laminar jet to characterize the advancing jet front, and to capture the formation and propagation of vortex rings and the related pinch-off process. Results show significant effects of buoyancy on jet advancement, as well as on vorticity and helium concentration in the core of the vortex rings.     

Studies of polarization/self-depolarization and electret-type effect in AgI

A novel d.c. polarization/self-depolarization study and electret-type effect in AgI are reported. AgI pellets of varying thicknesses, placed between two blocking (graphite) electrodes, were subjected to an external d.c. potential. A state of complete polarization was attained within ∼10 min, irrespective of the sample thickness. At this state, the potential difference, developed across the sample pellet as a result of polarization/accumulation of mobile Ag⁺ ions at the bulk/negative electrode interface, was measured experimentally. The potential difference, obtained immediately after the removal of the external d.c. source, has been referred to as ‘instant peak potential (V_p)’. As soon as the external voltage source is switched off, a process of self-depolarization is initiated due to the chemical/self diffusion of polarized mobile Ag⁺ ions throughout the bulk. ‘V_p’ gives a direct information regarding the extent of mobile ion concentration (n). ‘V_p’ measurements were carried out as a function of temperature and ‘Log V_p vs 1/T’ variation was compared with the ‘Log n vs 1/T’ Arrhenius plot, reported earlier in an entirely independent study. The two variations are almost analogous. This, in turn, supported as an earlier assertion that the abrupt conductivity increase in α-AgI, after β→α-phase transition at ∼147 °C, is predominantly due to the excessive increase in ‘n’. Furthermore, it has also been revealed that the Ag⁺ ions play another unique role which led to the existence of ‘persistent polarization’ states in AgI. These states are identical to the ‘electret-type effects’, observed in a number of dielectric materials. The polarization state persisted for very long time in ‘thermally stimulated polarized’ sample. A detailed investigation of the persistence/retention of polarization in the thermally-stimulated-polarized sample is reported.     

Analysis of the repulsive softness parameter in alkali halides

An analysis of the repulsive softness parameter for alkali halides has been presented on the basis of the additivity rule. The softness parameters for individual ions have been obtained using data from three different sources viz. overlap data, molecular data and crystal data. The softness parameters so derived are used to evaluate the bulk modulus and its pressure dependence for 20 alkali halides with NaCl and CsCl structures adopting Smith's distortion model for repulsive interactions. Some attractive features of the present approach have been discussed in order to demonstrate its superiority over the previous work.     

Studies with inorganic ion-exchange membranes

The pyridinium molybdoarsenate membrane shows a response to pyridinium ions and can be used to determine the concentration of these ions in the range 10(-3)-1M. The potentials generated across the membrane are reproducible and the response time is less than 1 min. There is no interference from certain inorganic and organic ions. The electrode can be used in the pH range 3-6 as well as in non-aqueous medium. Small additions of cetyltrimethylammonium bromide cause large shifts in the membrane potentials. A membrane, after being treated with this surfactant, shows a wider range of response to pyridinium ions. Precipitation titration of pyridinium nitrate has been monitored by using this membrane electrode.