New Evidence for Conformational Flexibility in Cyclodextrins from Vibrational Raman Optical Activity

Influence of Single Skimmer Versus Dual Funnel Transfer on the Appearance of ESI-Generated LiCl Cluster/ß-Cyclodextrin Inclusion Complexes

“…An attachment to the hydroxyl groups lining the rim around the cavity seems most likely, as a simple rearrangement would then yield HCl and R-O However, when measured with the QTOF instrument, CID of the LiCl adducts of the same mass-to-charge ratio results in entirely different product ions. Figure 2b shows the CID mass spectrum of the same precursor ion as discussed above for the QIT, (βCD)(LiCl) 2 Li + and its doubly charged dimer (βCD) 2 (LiCl) 4 Li 2 2+ at a low collision energy of 10 eV. Here, no HCl loss is observed; the product ions (βCD)Li + (m/z 1141) and (βCD) 2 (LiCl) 2 Li 2 2+ (m/z 1184) correspond to the loss of a neutral (LiCl) 2 -dimer from the singly and doubly charged precursor, respectively.…”

“…At the same time, the salt clusters, especially the smallest sizes, should not be able to fill the cavity of the cyclodextrin completely, as the cavity diameter of β-cyclodextrin is 600-650 pm and the height of its toroid is 790 pm [2], whereas the ionic radii of Li + and Cl − are 76 pm and 181 pm, respectively [32]. Although the cyclic oligosaccharides are no longer regarded as rigid structures [3][4][5][6], they may not be flexible enough to allow optimal interaction between the cluster and all the available oxygen sites. Stabilization of the cluster by only a few of the glycosidic oxygens is therefore likely, resulting in an overall weaker bonding to the cyclodextrin than in the case of individual attachment of the LiCl units.…”

“…(a) Mass spectrum of βCD with added LiCl using the QTOF with the ISCID energy set to 100 eV and (b) CID mass spectrum of (βCD)(LiCl) 2 Li + under the same transfer conditions at a collision energy of 50 eV. Dissociation of the doubly charged adduct (βCD) 2 (LiCl) 4 Li 2 2+ and subsequent HCl-losses result in the grey-labeled product ions at m/z 1159 and 1195. (c) Mass spectrum of the same solution acquired with the QIT at a dry gas temperature of 150°C oligosaccharides are probably bridged by one or both chargecarrying Li + cations bound to the hydroxyl groups of both cyclodextrins.…”

“…(βCD)(LiCl) 4 Na + (m/z 1327) was inadvertently included in the isolation; its fragment ions are labeled in grey. (c) CID mass spectrum of (βCD) 2 (LiCl) 5 Li 2 2+ , measured with the QIT at a dry gas temperature of 150°C already dissociated in the transfer region of the mass spectrometer, evidenced by the observation that the (LiCl) 2 dimer is only released once and successive losses of two or more (LiCl) 2 units (see Supplementary Material, Figure S2, for instance) are absent.…”

“…The hydroxyl groups are aligned at the rims of the cone, resulting in a hydrophilic lining around the edges. The size of the central cavity is controlled by the number of glucose units and even for a given size it is flexible enough to accommodate various molecules [3][4][5][6].…”