PMC:2812710 / 14540-16316 JSONTXT

{"target":"https://pubannotation.org/docs/sourcedb/PMC/sourceid/2812710","sourcedb":"PMC","sourceid":"2812710","source_url":"https://www.ncbi.nlm.nih.gov/pmc/2812710","text":"Comparison with the M values calculated from the chemical structure of the CDs shows that, in all solvents, the experimental data are relatively close to the theoretical ones. The measurements in DMF yield by far the closest agreement, the deviations being below 10% for all samples. But even for the worst result, obtained with γ-CD in DMSO, the deviation is below 50%. These results are highly surprising, since the s values on which they are based are around 0.5 S or even, in the solvent DMSO, around 0.15 S. As far as we know, the possibility of correctly or nearly correctly determining such small velocity sedimentation coefficients on the basis of the numerical solution of the Lamm equation has not been demonstrated before. It should be noted that, in the experiments described, the evolution of the sedimentation boundary occurs without appreciable boundary displacement. Elementary estimation shows that when the sedimentation coefficient is only 0.1 S the shift of the sedimentation boundary during 12 h of experiment at 55,000 rpm amounts to only 1 mm. To fix this shift by usual methods against a background of significant diffusion spreading obviously is not possible. In order to further strengthen the conclusions described, we have checked the validity of the theoretical M values by MALDI-TOF. The experimental spectra are presented in Fig. 5. Taking into account the mass of sodium ion the good correlation is observed between calculated and experimental values of molar masses (Table 1).\nFig. 5 MALDI-TOF-MS spectrum for the cyclodextrins (1 α-CD, 2 β-CD, 3 γ-CD) obtained on dihydroxybenzoic acid as matrix and NaTFA as a source of sodium ions. The figures at the peaks are the molar masses of cyclodextrine isotopes including the mass of one sodium ion","divisions":[{"label":"label","span":{"begin":1510,"end":1516}}],"tracks":[]}