Page 231 - PARVEEN, S
P. 231
Toluenesulphonic Acid. Bang. J. Sci. Ind. Res,. region might mediate cooperativity between the
2007, 42(4), 489-494. central active site of the enzyme through proper
formation of knot.
Isomeric xylenes have been cycloalkylated with
cyclohexene in the presence of p-toluenesulphonic 621 RAHMAN, M.A.; ASADULLAH, M.;
acid as catalyst. The effects of the variation of RAHMAN, M.S.; NABI, M.N. & AZAD,
temperature, molar ratio of xylene to cyclohexene, M.A.K. (Dept. of Applied Chemistry and
time of reaction and amount of p-toluenesulphonic Chemical Technology, Rajshahi University,
acid on the reactions have been studied and Rajshahi). Extraction of Gasohol Grade Ethanol
cyclohexyl xylenes have been obtained in high from Aqueous Solution using Gasoline as Solvent.
yield. Bang. J. Sci. Ind. Res., 2007, 42(3), 287-298.
661 : CHEMICAL TECHNOLOGY: Liquid-liquid phase equilibria of ethanol - water -
CHEMICALS gasoline ('iso-octane', 'octane' 'petrol', 'kerosene'
and 'diesel') were experimentally determined and
the ternary phase diagrams of the systems were
620 ALAM, M.T. (Dept. of Applied Chemistry studied with an end in view to develop methods of
and Chemical Technology, Rajshahi University, producing 'gasohol' by a once through operation.
Rajshahi). Importance of C-Terminal Knot
Binodal curves of the different systems were,
Structure in Carbonic Anhydrase Ii (Part I) : Role therefore, obtained to give quantitative ideas about
of C-Terminal Knot Forming Gln 253 on the extent of extraction of alcohol from aqueous
Enzymatic Property of Human Carbonic Ii. J. Bio- solution using gasoline. Phase equilibrium data,
Sci., 2006, 14, 1-9. distribution coefficient and separation factor were
obtained experimentally for ethanol-water-gasoline
In both, bovine and human carbonic anhydrase II, a systems. The order of the heterogeneous region of
conserved glutamine residue occupies the position the solvents is iso-octane .'octane' .'petrol' <
in the middle of the knot, which is formed by 'kerosene' < 'diesel'. The equilibriation and settling
intercrossing of C-terminal end with N-terminal time for ethanol - water - solvent systems are about
region. Previous studies have indicated that C- 10 and 20 min, respectively. The solubility of
terminus is not the part of an active site, but
ethanol in the solvents is in the order of iso-octane
truncation of 7 amino acid residue in this region .'octane' . 'petrol' > 'kerosene' > 'diesel'. The
can have marked effects on stability of the enzyme distribution coefficient increases with increasing
(data not published). To gain further insight into ethanol concentration in the feed; however, to the
the role of specific amino acid residue in C- contrary the separation factor decreases. The
terminal region, site directed mutagenesis was used distribution co-efficients are lower than 1 and the
to introduce point mutation. Substitution of
separation factors are greater than 10 for all of the
glutamine with cysteine was chosen because the solvents.
cysteine residue is less hydrophilic as compared
with glutamine and thus, may disrupt the 622 SALEH-E-IN, M.M. (Dept. of Chemistry,
hydrophilic environment in this region. Result Govt. Bangla College, Dhaka) & ROY, S.K.
indicates that Gln253 located within the C- (Chemical Research Division, BCSIR
terminus knot topology plays a significant role in Laboratories, Dhaka). Studies on Fatty Acid
normal function of the enzyme. Thus, C-terminal
224
