Molecular Dynamics Simulation Of Process Of Sweet Recognition Based On An Artificial Sweet Tast Receptor Model

Sweetness is a basic taste in the field of food science while there are five basic tastes. Sweetness organoleptic property always lies on panelist sensory evaluation. However, it is difficult to express taste with true feelings and impersonality because of much difference in psychology and physiology of panelists. In addition, researchers still have no integrated comprehension for sweetness mechanism because it has no definite structure of the taste receptor protein. So it is veiy important to construct an artificial sweet taste receptor model.Recently, our team used C60(OH)18as an artificial sweet taste receptor model, and isothermal titration calorimetry (ITC), sensory evaluation, nuclear magnetic resonance (NMR) as tool to research the recognition of artificial sweet taste receptor model with artificial sweeteners, natural sweeteners, sweetness isomer, sweetness inhibitor and sweetness enhancer. The result showed that fullerenols can effectively recognize sweetness as an artificial sweet taste receptor model, and it is important for researchers to understand sweetness strengthening mechanism and sweetness inhibiting mechanism. This thesis further applies molecular dynamics (MD) simulation approach to research on interaction between artificial sweet taste receptor model with sweetness and sweet isomers, and optimizes the structure of artificial sweet taste receptor model in order to obtain more information about mechanism of sweetness. The main research work is as follows:(1) The formation for research on interaction between artificial sweet taste receptor with sweetness by MD simulationThe interaction of6sweeteners (Fructose, Glucose, Galactose, Sucrose, Trehalose and Maltose) with fullerenols was researched by molecular dynamics. The result implied that the binding energies of6sweeteners with fullerenols were relational with the sweetness of6sweeteners. In the same condition, beginning with the largest binding energy is:Fructose> Glucose> Galactose> Sucrose> Trehalose> Maltose. Recently, we found the same law in the previous titration experiments of ITC. These show that effectiveness of fullerenols recognize sweeteners, as well as the feasiability of molecular dynamics method.(2) Research on the interaction of artifical model fullerenols with sweetness isomersRecently, our team research on the interaction of artifical model fullerenols with sweetness isomers by ITC and NMR technology, and the result shows'that β-isomers and fullerenols has more stable coalition compare with a-isomers. Energy would be released when P-isomers bind with fullerenols, and the energy is necessary for a-isomers transfer into β-isomers. The molecular dynamics simulation experimental result also shows that β-isomers and fullerenols has more stable coalition compare with a-isomers, and the binding energies of β-isomers with fullerenols are greater than a-isomers. However, the binding energies of L-isomers with fullerenols are also greater than D-isomers.By comparing the way of fullerenols combined with3kinds of sweeteners, it is found that the hydrogen bond play an important role when fullerenols combined with sweeteners. They have different binding site, ring part of the fructose has more stable coalition with fullerenols, and chain end of glucose and galactose have more stable coalition with fullerenols. These results would provide some information about mechanism of sweetness.(3) Structural optimization of artificial sweetness receptor model fullerenolsOn one hand, with the increasing of the number of fullerenols hydroxyl groups, the binding site of fullerenols with sweetness would increase. So, they can make better identification with sweetness. On the other hand, excessive fullerenols hydroxyl groups will decrease hydrophobic interaction, and hydroxyl groups of fullerenols will attract each other to form intramolecular hydrogen bond. In case fullerenols molecular form intramolecular hydrogen bond, the corresponding hydrogen atoms can not form hydrogen bond with other molecular, and it is going against to recognization reaction of fullerenols with sweetness. So, Structural optimization of artificial sweetness receptor model fullerenols is necessary, and the result shows that C60(OH)20is more suitable to be used as artificial sweetness receptor model. The molecular dynamics simulation the result shows intramolecular hydrogen bond would increase when increase the number of fullerenols hydroxyl group, and it is further prove that fullerenols will not suitable to be used as artificial sweetness receptor model to recognize sweetness if the number of hydroxyl group more than20.In conclusion, this thesis applies molecular dynamics simulation method approach to further study the interaction between artificial sweet taste receptor model with sweetness and sweet isomers, and optimizes the structure of artificial sweet taste receptor model in order to obtain more information about mechanism of sweetness. The purpose of this thesis is to form method for research on artificial sweet taste receptor by molecular dynamics simulation, enrich biomimctic chemistry of sweetness mechanism study, and introduce molecular dynamics method to food science.