In general, the C-H…O distance is in the range of 2.2-2.6 Å, which is longer than that of O-H…O with the range of 1.5-2.1 A˚ [25, 26]. It should be noted that the C-H…O bonds are weaker than the O-H…O bonds [57]. As seen in Table 3, the O-H…O and C-H…O distances for the conjugate bases of methyl-pentose sugars are in the range of 1.78-2.08 Å and 2.54-2.74 Å, respectively. These values are in good agreement with the geometrical results of inter-molecular CH…O/N H-bonds in DNA and RNA and Guanosine [30, 43]. As seen in Table 4, the O-H…O distances in the aldo-pentose sugars and their conjugate bases are within 1.53-2.16 Å. These values are in good agreement with our previous investigations [31, 44].