Force Measurement for Antigen-Antibody Interaction by Atomic Force Microscopy Using a Photograft-Polymer Spacer

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• 作者：Alimjan Idiris ; Satoru Kidoaki ; Kengo Usui ; Tei Maki ; Harukazu Suzuki ; Masayoshi Ito ; Makoto Aoki ; Yoshihide Hayashizaki ; and Takehisa Matsuda
• 刊名：Biomacromolecules
• 出版年：2005
• 出版时间：September 2005
• 年：2005
• 卷：6
• 期：5
• 页码：2776 - 2784
• 全文大小：827K
• 年卷期：v.6,no.5(September 2005)
• ISSN：1526-4602

文摘

To determine the intermolecular force on protein-protein interaction (PPI) by atomic force microscopy(AFM), a photograft-polymer spacer for protein molecules on both surfaces of the substrate and AFM probetip was developed, and its effectiveness was assessed in a PPI model of a pair of human serum albumin(HSA) and its monoclonal antibody (anti-HSA). A carboxylated photoiniferter, N-(dithiocarboxy)sarcosine,was derivatized on both surfaces of the glass substrate and AFM probe tip, and subsequently water-solublenonionic vinyl monomers, N,N-dimethylacrylamide (DMAAm), were graft-polymerized on them uponultraviolet light irradiation. DMAAm-photograft-polymerized spacers with carboxyl groups at the growingchain end but with different chain lengths on both surfaces were prepared. The proteins were covalentlybound to the carboxyl terminus of the photograft-polymer chain using a water-soluble condensation agent.The effects of the graft-spacer length on the profile of the force-distance curves and on the unbindingcharacteristics (unbinding force and unbinding distance) were examined in comparison with those in thecase of the commercially available poly(ethylene glycol) (PEG) spacer. The frequency of the nonspecificadhesion force profile was markedly decreased with the use of the photograft spacers. Among the forcecurves detected, a high frequency of single-peak curves indicating the unbinding process of a single pair ofproteins and a very low frequency of multiple-peak profiles were observed for the photograft spacers,regardless of the graft chain length, whereas a high frequency of no-force peaks was noted. These observationswere in marked contrast with those for the PEG spacer. The force peak values determined ranged from 88to 94 pN, irrespective of the type of spacer, while the standard deviation of force distribution observed forthe photograft spacer was lower than that for the PEG spacer, indicating that the photograft spacers providea higher accuracy of force determination.