الفهرس 
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Abstract
In this thesis, different studies including spectral and capillary electrophoretic methods, have been conducted for characterization of a new class of boronic acid-based squarylium dyes for its utility as fluorescent probes for some biological and even biopharmaceutical targets and the thesis consists of six main chapters:
Chapter I:
It describes the theoretical background and literature review of CE technique, instrumentation, modes, detection methods coupled with this technique specially LIF beside a brief introduction about derivatization and labeling protocols for analytes of interest.
Chapter II:
In this chapter, four monofunctional boronic acid functionalized squarylium dyes of different structures were subjected to molecular design studies for better understanding their selectivity toward monosaccharides and sialic acid based on their different alkyl side chain lengths. This chapter includes a brief scheme of synthesis of the four squarylium dyes mainly through a condensation reaction of squaric acid with two aromatic and/or heterocyclic compounds, which produces the 1,3disubstituted structure. The structure of the dye has been modified by incorporating one terminal boronic acid group with different alkyl chain lengths to give us four different functional dyes SQ-BA1, 2, 3 and 4.
The SQ-BA dyes form aggregates based on hydrophobic interactions in aqueous solutions. When the boronic acid binds with saccharides, the fluorescence intensity increases as a result of the dye aggregate dissociation to the emissive monomeric boronate ester complex form. The dye behavior varied based on the length of the alkyl side chain where dyes with shorter alkyl chains in the presence of Neu5Ac showed emission enhancement with no such enhancement for dyes with longer alkyl chains. Also, various enhancement factors for other monosaccharides were observed depending on the alkyl chain lengths. In addition, thermodynamic and NMR studies of the SQ-BA complexes revealed that the dye aggregate with a shorter alkyl chains causes the slipped parallel structure and forms a stable 2:1 complex with Neu5Ac, unlike longer alkyl chains dyes, which form a 1:1 monomeric complex. This study successfully controlled various responses and specificities of the dyes to monosaccharides due to not only the boronic acid moiety but also the length of the alkyl chain residue.
Chapter III:
This chapter includes the spectral studies of two novel squarylium dyes, monofunctional boronic acid-based SQ-BA4 and bifunctional boronic acid-based SQ-DBA2 under a variety of solutions to explore the optimal conditions for non-covalent protein labeling. Both dyes exhibited very low fluorescence intensity in aqueous solutions presumably due to H-aggregate formation in absence of the protein but showed a significant enhancement in the fluorescence intensity with the addition of HSA in the optimal acidic citrate buffer. Stability constant studies were conducted and SQ-BA4 dye was shown to have much stronger binding affinity with HSA than SQ-DBA2. Also, the stoichiometries of non-covalent complexes were found to be (1:1) for SQ-BA4 and different (1:2) for SQ-DBA2 with HSA. However, these studies are not necessary to be the optimal for CE work, and so, additional studies to determine the optimal conditions for protein assays by CE-LIF which will be progressed in the next chapter.