Lacto n tetraose

Human milk oligosaccharide standards were purchased from Carbosynth (Berkshire, UK): lacto-N-biose (LNB), N-acetyl lactosamine (LacNAc), lacto-N-tetraose (LNT), lacto-N-neotetraose (LNnT), para-Lacto-N-hexaose (pLNH), and para-Lacto-N-neohexaose (pLNnH). 3-amino 3-deoxy α-cyclodextrin (α-CD) and 3-amino 3-deoxy β-cyclodextrin (β-CD) were purchased from Tokyo Chemical Industry (Tokyo, Japan). Cucurbit[5]uril (CB5), cucurbit[7]uril (CB7), cyclosporin A, valinomycin, polymyxin B, and ammonium ionophore I were purchased from Sigma-Aldrich (Milwaukee, WI USA). 12-Crown-4, 15-Crown-5, and 18-Crown-6 were purchased from Alfa Aesar (Ward Hill, MA USA). LC-MS grade solvents were obtained from Fisher Scientific (Pittsburgh, PA USA). Stock solutions for all HMOs, cyclodextrins, cucurbiturils, crown ethers, and polymyxin B were dissolved in 100% H₂O, while stock solutions for cyclosporin A, valinomycin, and ammonium ionophore I were dissolved in 100% methanol. Each host-guest solution mixture was prepared to 5 μM in 49.75/49.75/0.5 (v/v) water/methanol/acetic acid for each reagent used (i.e., both the host and guest were at 5 μM). Each HMO pair was also run as a mixture (see the solid black traces in Figures S1–S3 of the Supporting Information).