Title:
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Synthesis and biological properties of cytotoxic lectin conjugates
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Proliferative vitreoretinopathy (PVR) is an anomalous cell proliferation condition
that occurs after surgery on the retina. 5-Fluorouracil (5-FU) has been shown to be
effective in reducing the incidence ofPVR in animal models and recently been used
as a clinic adjunctive treatment of PVR. However, the results of such treatment have
been disappointing, largely because these drugs are quickly metabolized within the
eye minimizing their long-term effectiveness; high doses ofthese drugs may also be
toxic to the retina.
Agaricus bisporus lectin (ABL) is obtained from t~e edible common mushroom and
has been shown to have reversible, dose-dependent and specific anti- proliferation
activity in vitro. The aim ofthis research project is to conjugate 5-FU and ABL
together by using chemical conjugation methods to give potentially potent and
specific anti-proliferative activity for the treatment ofPVR.
The first part of this project is to study the protein structure of the ABL, which is to
find the suitable residues as conjugation targets. ABL is found as a homotetramer
protein and each ofthe four subunits has a molecular mass of 16,053.8 Da. There are
one cysteine and five lysines for each of the lectin subunits. The free -SH of
cysteine, free -NH2 of lysine and the N-terminal amino groups are conjugation
targets.
The second part of the project is to modify the 5-FU with either amino or azido
functional groups preparing derivatives of 5-fluorouridine which can then be
conjugated to ABL.
The third part of the work describes the conjugation of the modified 5-FU with ABL
by using SMCC (succinirnidyI4-(N-maleimidomethyl) cyclohexane-l-carboxylate)
cross linker, aconitic acid anhydrate linker, 'click' chemistry as well as the
photochemistry method separately, followed by characterization by SDS-PAGE
(sodium dodecyl sulphate-polyacrylamide gel electrophoresis) and the biological test.
MALDI-MS (matrix-assisted laser desorption/ionization mass spectrometry) is also
attempted for further characterization.
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