Electron and proton transferring properties of vitamin K-1 across a self-assembled phospholipid monolayer
JOURNAL OF ELECTROANALYTICAL CHEMISTRY
Authors: Herrero, R; Buoninsegni, FT; Becucci, L; Moncelli, MR
The electrochemical behaviour of vitamin K-1 (VK1) incorporated in a self-assembled monolayer of dioleoylphosphatidylcholine (DOPC) deposited on a hanging mercury drop electrode was investigated by a computerized chronocoulometric technique. The kinetics of VK1 electroreduction to the corresponding quinol, VK1H(2), and that of VK1H(2) reoxidation to VK1 were examined for reactant concentrations ranging from 0.5 to 2 mol% by varying the pH from 5.5 to 9 with phosphate and berate buffers. On the basis of a general kinetic approach it was concluded that the reduction of VK1 to VK1H(2) in a DOPC monolayer takes place via the reversible uptake of one electron, yielding the semiquinone radical anion VK1(.-), followed by the rate determining protonation of the latter. On the other hand, the oxidation of VK1H(2) to VK1 takes place via the reversible release of one electron, yielding the semiquinone radical cation VK1H(2)(+.), followed by the rate determining deprotonation of the latter. The only effective proton donors in VK1 reduction are the protons, whereas the main proton accepters in VK1H(2) oxidation are the water molecules. (C) 1998 Elsevier Science S.A. All rights reserved.
Guided selection of human antibody light chains against TAG-72 using a phage display chain shuffling approach
JOURNAL OF MICROBIOLOGY
Authors: Kim, Sang Jick; Hong, Hyo Jeong
To enhance therapeutic potential of murine monoclonal antibody, humanization by CDR grafting is usually used to reduce immunogenic mouse residues. Most humanized antibodies still have mouse residues critical for antigen binding, hut the mouse residues may evoke immune responses in humans. Previously, we constructed a new humanized version (AKA) of mouse CC49 antibody specific for tumor-associated glycoprotein, TAG-72. In this study, to select a completely human antibody light chain against TAG-72, guided selection strategy using phage display was used. The heavy chain variable region (VH) of AKA was used to guide the selection of a human TAG-72-specific light chain variable region (VL) from a human VL repertoire constructed from human PBL. Most of the selected VLs were identified to be originated from the members of the human germline VK1 family, whereas the VL of AKA is more homologous to the VK4 family. Competition binding assay of the selected Fabs with mouse CC49 suggested that the epitopes of the Fabs overlap with that of CC49. In addition, they showed better antigen-binding affinity compared to parental AKA. The selected human VLs may be used to guide the selection of human VHs to get completely human anti-TAG72 antibody.