Social and Scientific Programme

s: Aluminum complexes are essential for understanding the toxicity, bioavailability and transport mechanisms for elements in environmental and biological systems. Many methods have been developed during the last two decades. Since validation of what is really structure in these weak coordinated systems is very difficult, the analytical techniques for Al complexes structures in aqueous solutions are elucidated in the following three aspects: (1) Constitutional studies: The interactions of aluminum with -ketoglutarate were studied with pH-potentiometry (BEST&SPE program), UV-Vis, NMR, Raman spectra and MM calculation in acidic aqueous solution to measure the stoichiometries and its keto-enol tautomerism. Moreover, the indivial isomers of Al-glutathione (GSH) complexes in aqueous solutions were confirmed by Gaussian calculation and ESI-MS technique. (2) Configurational studies: Glutamic acid (Glu) is an important acidic neurotransmitter in the central nervous system. Nature prefers L-amino acids rather than D-forms for the construction of proteins. However, many studies have shown mild accumulation of D-glutamate as an aging phenomenon and significantly higher levels in Alzheimer’s disease affected brain regions and cerebrospinal fluid. Former studies have strongly suggested that, besides the negatively charged carboxylate donors (-COO-, -COO-), the amino group of Glu can participate in the tridentate binding (-COO-, -NH2, -COO-) of Al in the AlL+ and AlLH-1 species in case of its deprotonation. Now, we proved that the complex abilities of AlL+ and AlLH-1 in D-Glu-Al species were stronger than those of L-Glu-Al species, which were confirmed by pH-potentiometry and hyperchem calculations. These results can help to explain above biological and clinical phenomenon, which is also very important in the food chemistry.(3) Conformational studies: At biologically relevant pH and concentrations of Al and NADH, Al could increase the amount of folded forms of NADH, which will result in reducing the coenzyme NADH activity in hollow-dehydrogenases reaction systems. However, the conformations of NAD+ and Al-NAD+ depended upon the solvents and different species in the complexes, which Al bioavailability in biogeochemical cycles Toxicological effect of Al in biological systems Structures of Al species in aqueous solutions Constitutional aspect Configurational aspect Conformational aspect were confirmed with 1H, 1H-NOESY-NMR spectroscopy. Since many analytical methodologies could provide more structural information, it could allow the identification of the bioligand and its complexes, not only in molecular binding sites, species, abilities and its effects, but also in molecular constitution, configuration and conformation. These structural aspects will yield in better understanding of the roles of aluminum (III) in biological and environmental systems. Also, in this case, we may need a new word “STRUCTATION” to represent the structural aspects after fractionation and speciation aspects.