Structural studies by 1H/13C two-dimensional and three-dimensional HMQC-NOE at natural abundance on complex carbohydrates

0002-7863/90/ 15 12-3232%02.50/0 ion/alkane clustering data. Mobilities in helium are often determined largely by forces other than the charge-induced dipole, due to the small polarizability of h e l i ~ m . ' ~ ' ~ The existing Ti+ mobility data9 support the above hypothesis. The Ti+ ground state (3d24s1,4F) includes a 4s electrod and has a mobility of 25.5 f 0.5 cm2/(V s ) , ~ very similar to that of the excited-state cobalt. This may indicate that configuration (not electronic state) determines mobility. Further support for long-range repulsion between excited Co+ and He cOmm from the absence of deactivation in collisions with helium ( k < 1 X cm3/s). Deactivation might be expected in an intimate collision. We are examining other first-row transition metals to check the correlation between high mobility and occupied 4s orbital. Finally, we can compare the apparent effects of 3d and 4s orbital population on ion mobility. Potassium ions (3p6,'S) have a mobility of He of 21.6 cm2/(V s ) . 1 4 9 1 s If the metal ion/He interaction were purely electrostatic (Le., charge-induced-dipole attraction versus electron-electron repulsion), we would expect that adding 3d electrons to K+ should cause some increase in mobility due to increased electron density on the ion while adding a 4s electron should cause a greater increase.I6 In fact, the 3d electrons cause a large decrease in mobility (at least for ground-state Co+), indicating a decreased repulsion, which must be due to other factors. Studies of other first row transition metal ions are in progress.