Glucose and Mannose: A Link between Hydration and Sweetness.

Area of Science:

• Carbohydrate chemistry
• Structural biology
• Taste receptor mechanisms

Background:

• Sweetness perception of sugars like glucose and mannose differs, suggesting varied interactions with sweet taste receptors.
• The precise structure of the sweet taste receptor remains unknown, necessitating models to understand sugar binding.
• Investigating sugar hydration is crucial for validating existing geometrical models of taste receptor binding.

Purpose of the Study:

• To investigate the hydration structure of glucose and mannose using neutron diffraction.
• To correlate the hydration shell characteristics of these sugars with their known sweetness.
• To assess the accuracy of geometrical models for sweet taste receptor binding mechanisms.

Main Methods:

• Neutron diffraction was employed to study the hydration structure of glucose and mannose in solution.
• Analysis focused on the hydrogen bonding and steric arrangement within the first hydration shell of each sugar.
• Comparison of experimental hydration data with established geometrical models of sweet taste receptor binding.

Main Results:

• Both alpha- and beta-glucose exhibit strong hydrogen bonds with water, and their hydration shells align with receptor models.
• Alpha-mannose shows a defined hydration shell with weaker hydrogen bonds than glucose.
• Beta-mannose, perceived as bitter, displays a hydration shell that does not conform to the receptor geometrical model.

Conclusions:

• The study establishes a correlation between the hydration shell structure of sugars and their degree of sweetness.
• Findings support the utility of hydration shell analysis in understanding sugar-receptor interactions and validating binding models.
• The distinct hydration patterns of glucose and mannose isomers provide insights into the molecular basis of taste perception.