Using a combination of 1H NMR nuclear Overhauser effect measurements, molecular orbital calculations, and molecular dynamics simulations, we have determined the tertiary structure and dynamic properties of the oligomannose oligosaccharide Man.alpha.6(Man.alpha.3)Man.alpha.6(Man.alpha.3)Man.beta.4GlcNAc.beta.4GlcNAc. While the calculated potential surfaces for the majority of the glycosidic linkages could be described by a single deep potential well, similar calculations for the Man.alpha.1-6Man.alpha. and Man.alpha.1-6Man.beta. linkages described a diffuse, shallow well, suggesting that a larger degree of flexibility exists about the latter. These conclusions are supported by the results of molecular dynamics simulations, which suggest that the NMR data should be interpreted in terms of a degree of flexibility about the Man.alpha.1-6Man.beta. and Man.alpha.1-6Man.alpha. linkages. In contrast, a similar series of investigations suggests that the conformation of the Man.alpha.1-6Man.beta. linkage in Man.alpha.2Man6(Man.alpha.2Man.alpha.3)Man.alpha.6(Man.alpha.2Man.alpha.2Man.alpha.3)Man.beta.4GlcNAc.beta.4GlcNAc is more restricted, resulting in an overall structure that is "restrained".