Our work reports in detail the results of systematic large-scale theoretical investigations of the glycosaminoglycan building units 1-OMe Delta IdoA-2SNa(2) (1; H-2(1) and H-1(2) forms), 1-OMe GlcN-S6SNa(2) (2), 1,4-DiOMe GlcNa (3), 1,4-DiOMe GlcN-S3S6SNa(3) (4), 1,4-DiOMe IdoA-2SNa(2) (5; C-4(1), C-1(4), and S-2(o) conformations), and 1,4-DiOMe GlcN-S6SNa(2) (6) at the BP86/TZ2P level of the density functional theory. The optimized geometries indicate that the most stable structure of these monomeric units in the neutral state is stabilized via "multifurcated" sodium bonds. The equilibrium structure of the biologically active anionic forms of the glycosaminoglycans studied changed considerably in a water solution. The computed interaction energies, Delta E, of sodium coordinated systems 1-6 are negative and span a rather broad energy interval (from -130 to -590 kcal mol(-1)). Computations that include the effect of solvation indicated that in water the relative stability of Na+...ligand ionic bonds is considerably diminished. The computed interaction energy in water is small (from -20 to -53 kcal mol(-1)) and negative, that is, stabilizing.