Study On Sweetness Recognition With Fullerenolos As An Artificial Chemoreceptor Model: An Isothermal Titration Calorimetry Study

Sweetness is the most common taste for food. Sensory sweetness intensity always lied on panelist sensory evaluation in the past. It exists a big conditionality for expressing tastes with impersonality and true feelings because of much difference in physiology and psychology such as panel individual, gender, experience and so on. In the aspect of molecular cytobiology, up to the present, it still has no exact structure of taste receptor protein so as to restrict integrated comprehension for sweetness mechanism. So it is very important for constructing an artificial sweet taste chemoreceptor and a method of physical chemistry representation for sensory sweetness.In this paper, fullerenols was used as an artificial sweet taste chemoreceptor model, and isothermal titration calorimetry (ITC) was a tool to examine the thermodynamic action of interactions between fullerenols and sweeteners for a pilot study on the molecular recognition of sweet taste. Fullerenols was suitable for a sweet taste chemoreceptor model, because it was one of compounds containing the greatest number of hydroxy groups for a molecule in the three-dimensional space at present. It had the most essential character of binding with sweeteners through specific recognition. The main research work is as follows:(1) The formation for titration mode of ITC. At first, it was to study binding and interaction between sucrose and fullerenols with a traditional positive titration mode of ITC, but the binding heats were always covered by dilution heats of sucrose and fullerenols so that this two kinds of heat signal were hard to differentiate. Then, negative titration mode was selected to have a research and made the signal get efficient division between binding heats and dilution heats in the end.(2) Titration experiments of ITC and study of correlation between sweet taste and thermodynamic parameters. In the prophase experiments, it had been proven that a relativity existed between sensory sweet taste and thermodynamic parameters. Therefore, in the late experiments, it got the optimal concentrations of fifteen sweeteners through binding with fullerenols, and a fitting for the optimal thermodynamic parameters and the logarithm value of sweetness intensity by multivariate linear regression.The fitting formula was: LgS=-274.541ΔH₁+1.133563ΔH₂+81798.77ΔS₁-157.43ΔS₂+274.2528ΔG₁-0.24337ΔG₂+1.34968, the correlation coefficient R was 0.99208.(3) Besides, isothermal titration calorimetry for study on fullerenols with different gustatory substances or in different environmental conditions so as to validate speciality of interactions between artificial sweet taste chemoreceptor and sweeteners. Both the thermodynamic action and parameters could reflect the relation of sweetness intensity for interactions with six D/L-sugars. According to thermodynamic action, there was a big difference between non-sweet substances and sucrose but a similar action for the same gustatory substances. Thermodynamic action could also be an expression of increasing sweetness intensity for compound sweeteners including three artificial synthetic sweeteners with high sweetness intensity. Fullerenols interacted with three common sugars at 20℃,25℃,30℃,37℃,42℃.ΔH₁ was a minimum at 30℃and temperature had a little effect onΔG for these sugars.In this paper, it affirmed the feasibility of fullerenols as an artificial sweet taste chemoreceptor through isothermal titration calorimetry and constructed an experimental model of thermodynamics for an artificial sweet taste chemoreceptor. So it built up experimental and academic foundation for studying sweetness mechanism to be more thorough and systemic.