Study Of Boronic Acid For Recognition And Determination Of Monosaccharides By Spectrometry

Saccharides closely relate to organisms. The carbons in saccharides bind with each other by single bond, and the carbon backbones are mainly bound by hydroxyl and carbonyl groups.As a result, the saccharides are lack of UV-Vis and fluorescent properties, and can't be studied by spectrometry directly. Boronic group can react with diols to form stable esters. Various boronic acid derivatives containing chromophores and fluorophores show absorbance and fluorescent intensity and wavelength changes upon binding with diols or saccharides to different degrees. Accordingly, boronic acid derivatives are available for sensing monosaccharides by spectrometry. This paper was divided into four chapters to present.In chapter 1,the boronic acid derivatives possessing UV-Vis absorption and fluorescence properties were categorized by structures of chromophores and fluorophores.The latest development of colormetric and fluorescent receptors containing boronic acid group used in the research of monosaccharide recognition since 2002 was summarized.In chapter 2, four catechol azobenzene derivatives were synthesized and characterized by melting point determination and 1H NMR. The reactions between the four derivatives and PBA were investigated by UV-Vis spectra. Stable complexes were formed between catechol azobenzene derivatives and PBA in pH 7.4 KH2PO4-NaOH buffer solution, which caused significant changes of derivatives' spectra, with apparent movements of maximum absorption wavelengths. The binding contants between azobenzene derivatives and PBA were calculated. The catechol azobenzene derivatives were used as indicators (I), along with phenylboronic acid (PBA), an I-PBA system was built up to sense monosaccharides by indicator-deplacement assay (IDA).The reactions between I-PBA and mono-saccharides were studied by UV-Vis spectra. The spectral properties recovered partly to derivatives'upon additions of monosaccharides in pH 7.4 KH2PO4-NaOH buffer solution. I-PBA highly selected sorbitol and D-fructose.The binding contants between sorbitol and D-fructose and PBA were calculated.In chapter 3,the reaction between Alizarin Red S (ARS) and boric acid (BA) was studied by UV-Vis and fluorescent spectra. The absorption peak of ARS at 515 nm blue shifted upon addition of BA in pH 7.4 KH2PO4-NaOH buffer solution. The solution changed its color from red to yellow. Two clear isosbestic points were observed at 381 and 474nm, respectively, which revealed that ARS bound with BA to form a tight complex. The binding constant between them were calculated. On the other hand, BA increased the fluorescent intensity of ARS dramatically. ARS-BA system was set up to sense monosaccharides by means of IDA. The investigation by UV-Vis and fluorescent spectra showed that partical recoveries of spectral properties occurred upon addition of monosaccharides. The binding constant between various monosaccharides and BA were calculated. In which,sorbitol and D-fructose had much larger association constants with BA than the other five monosaccharides observed. By structure analysis of them, the reason was investigated that the former two monosaccharides contained relative free adjacent dihydroxy.In chapter 4, three hydrazone boronic acid derivatives,2'-,3'-and 4'-borono benzaldehyde-4-(dimethylamino)benzoyl hydrazone (2'-,3'-and 4'-BBDBH) were designed and synthesized. The proposed structures were characterized by melting point determination and 1H NMR spectra. The reactions between 2'-,3'-and 4'-BBDBH and monosaccharides were studied by UV-Vis and fluorescent spectra. Most monosaccharides investigated could decrease the absorption of 2'-BBDBH, and increase the absorptions of 3'-and 4'-BBDBH in pH 7.4 KH2PO4-NaOH buffer solution (containing 10% v/v ethanol).The association constants of ground-state receptors with various monosaccharides were calculated. The fluorescent intensities of three compounds increased to varying degrees upon binding with monosaccharides. The fluorescent intensities vs.sugar concerntrations plots showed linear nicely. All the receptors represented good fluorescent responses and selectivity to L-arabinose. The fluorescent intensities of 2'-,3'-and 4'-BBDBH increased to 5.2,12.4 and 13.4 folds upon addition of 90.9 mmol·L-1 L-Ara.,but didn't reach saturations yet. It is worth notice that all the receptors can discriminate L-arabinose from D-arabinose moderately, which might contribute to further studies of fluorescent chiral sensing monosaccharides.