Abstract:
Three lectins were extracted and purified from Cassia fistula seeds in biologically
active form by gel filtration of I 00 % ammonium sulfate saturated crude protein
extract on Sephadex G-50 followed by ion-exchange chromatography on DEAE
celluiose and then affinity chromatography on Sepharose 4B. The lectins were
found to be homogeneous justified by polyacrylamide disc gel electrophoresis.
The molecular weights of the lectins CSL-I, CSL-2 and CSL-3, determined by gel
filtration on Sephadex G-75 column were 37,000, 42,400 and 46,000, and by SDS
gel electrophoresis were 37500, 42000 and 46500, respectively. The lectins
agglutinated rat red blood cells and the agglutination was inhibited specifically by
galactose and galactose containing saccharide. The neutral sugar contents of the
lectins, CSL:-1 , CSL-2 and CSL-3 were estimated to be 3.5, 3.1 and 2.0 %
respectively. The sugar composition of the lectins was found to be galactose for
CSL-I, galactose and glucose for CSL-2, and galactose and mannose for CSL-3.
The lectins displayed strong cytotoxic effect in brine shrimp lethality bioassay and
among the lectins purified, CSL-2 was found to be highly toxic followed by CSLI
and then CSL-3. The purified lectins in aqueous solution gave absorption
maxima around 274-278 run and minima around 243-248 run.
Biological activities of the lectins CSL-I, CSL-2 and CSL-3, were investigated
after various physico-chemical treatments. Biological activities were highly
affected with the changes of pH and temperature, and the lectins exhibited
maximum hemagglutinating activities around pH 7.2 to 7.5 and at temperature 20°
to 35 °C. Biological activities of the lectins were abolished sequentially with the
increase in concentration of acetic acid and denaturant solutions such as urea and
guanidine-HCI.-----
Description:
This Thesis is Submitted to the Department of Biochemistry and Molecular Biology, University of Rajshahi, Rajshahi, Bangladesh for The Degree of Doctor of Philosophy (PhD)