The study confirmed that the size in X is not critical for the sweetness potency,but the peptide bond and the hydrogen of amide in the peptide bond is essential for sweetness.

• 而肽键对于维持甜味是必需的,用酯键取代肽键导致甜味消失,氨基上的氢键对于维持甜味来说也是必需的,当它被甲基取代时甜味也消失了。