Surface Modification of a Stable CdSeZnS/ZnS Alloy Quantum Dot for Immunoassay
JOURNAL OF NANOMATERIALS
Authors: An, Jaehyun; Huynh, Kim-Hung; Ha, Yuna; Jung, Heung Su; Kim, Hyung-Mo; Kim, Dong-Min; Kim, Jaehi; Pham, Xuan-Hung; Kim, Dong-Eun; Ho, Jin-Nyoung; Lee, Sangchul; Lee, Ho-Young; Jeong, Dae Hong; Jun, Bong-Hyun
Quantum dots (QDs) are powerful materials in various bioapplications based on their excellent optical and electronic properties. For the application of various fields of QDs, surface modification of QDs is necessary. However, surface modification in QDs may result in a reduction in quantum yield (QY). This reduction of QY causes many weaknesses in the biological application of QDs. In this study, CdSeZnS/ZnS alloy QDs were used to prepare antibody-conjugated QDs for a sandwich immunoassay. The alloy QDs displayed a QY of 84.5% that was maintained at 83.0% (98.2% of QY was maintained) after surface modification with the anti-rabbit IgG as a model study. Surface-modified QDs successfully detected their corresponding target through antibody-antigen binding. The limit of detection was 1.1x10(2) ng mL(-1) for rabbit IgG.
Selectivity over coverage in de novo sequencing of IgGs
Authors: den Boer, Maurits A.; Greisch, Jean-Francois; Tamara, Sem; Bondt, Albert; Heck, Albert J. R.
Although incredibly diverse in specificity, millions of unique Immunoglobulin G (IgG) molecules in the human antibody repertoire share most of their amino acid sequence. These constant parts of IgG do not yield any useful information in attempts to sequence antibodies de novo. Therefore, methods focusing solely on the variable regions and providing unambiguous sequence reads are strongly advantageous. We report a mass spectrometry-based method that uses electron capture dissociation (ECD) to provide straightforward-to-read sequence ladders for the variable parts of both the light and heavy chains, with a preference for the functionally important CDR3. We optimized this method on the therapeutic antibody Trastuzumab and demonstrate its applicability on two monoclonal quartets of the four IgG subclasses, IgG1, IgG2, IgG3 and IgG4. The method is based on proteolytically separating the variable F(ab ')(2) part from the conserved Fc part, whereafter the F(ab ')(2) portions are mass-analyzed and fragmented by ECD. Pure ECD, without additional collisional activation, leads to straightforward-to-read sequence tags covering the CDR3 of both the light and heavy chains. Using molecular modelling and structural analysis, we discuss and explain this selective fragmentation behavior and describe how structural features of the different IgG subclasses lead to distinct fragmentation patterns. Overall, we foresee that pure ECD on F(ab ')(2) or Fab molecules can become a valuable tool for the de novo sequencing of serum antibodies.