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.      

Development and application of a simple capillary-microreactor for oxidation of glucose with a porous gold catalyst

An efficient oxidation of glucose to gluconic acid was performed using a porous gold(0) catalyst in a low-cost microreactor designed from Pyrex glass capillary tubing; compared with the conventional synthesis procedure this novel approach of using a capillary-microreactor offers a convenient and highly efficient means to optimise reaction conditions and catalytic activities.     

Unusual luminescence characteristics of aminobiphenyls

Analysis of fluorescence solvatochromic shifts of ortho, meta and para aminobiphenyls reveals that the change in dipolemoment of m-aminobiphenyl on excitation is more when compared to other isomers. This change is due to the resonance interaction of unsubstituted phenyl ring with -NH2 group at meta position in the excited singlet state. The fluorimetric titration curves of three aminobiphenyls are found to be different from each other. The stretched sigmoidal curves obtained for m-aminobiphenyl indicates that the rates of proton transfer in S1 state are comparable to the rates of fluorescence.     

Characterization of InxGa1−xAs crystals by 14 MeV neutron activation analysis

Indium doped GaAs crystals are analyzed quantitatively for indium by non-destructive 14 MeV neutron activation analysis. Experimental conditions are optimized to provide a precision of ±5% and a practical sensitivity of 50 ppm, by weight. The accuracy of the neutron activation method is established by comparison with the results obtained by atomic absorption and Rutherford back-scattering techniques. The method has been applied for determining the homogeneity of indium distribution of wafers by sectional analysis and is demonstrated as a reference method for calibrating the low temperature photoluminescence technique.     

Base catalysed rearrangement of a spiro oxy-cope system and related studies: A new entry into perhydrophenalene and perhydroacenaphthylene systems

The spirovinyl carbinol 5 when treated with methanolic potassium hydroxide was found to rearrange to perhydrophenalene- 1,4-dione 6 via an anionic oxy-Cope rearrangement followed by an intramolecular Michael addition. The epimeric mixture of ketol acetates 15a and 15b was also found to rearrange to 2-hydroxy-2-methyl perhydroacenaphthylene-1,3-dione 16 on treatment with base.     

Effect of non-crystallinity on neutron transport in polyethylene

The computed values of time dependent decay of a neutron pulse in crystalline polyethylene turns out to be nearly the same as the experimental results for non-crystalline polyethylene. The effect of non-crystallinity on the transport of neutrons in polyethylene is therefore insignificant.