ABSTRACT
High-frequency (~ 55 MHz) wireless quartz-crystal microbalance biosensor was used for studying heterogeneous deposition behavior of Aß(1-40) peptide on Aß(1-42) nuclei, which were grown under the stirring agitation and 200-kHz ultrasonication at pH 2.2, 4.6, and 7.4. The deposition reaction was monitored over 40 h, and the deposition rate was deduced. Among the agitation nuclei, the maximum deposition rate was observed on the nucleus grown at pH 4.6. However, ultrasonication nucleus grown at pH 7.4 produced much larger deposition rate, despite the same ß-sheet concentration. This result indicates that local structural modulation is caused in the nucleus by ultrasonication, which adsorbs the Aß peptide more actively than other nuclei. The resultant deposits clearly show oligomeric structure.
Subject(s)
Amyloid beta-Peptides/chemistry , Biosensing Techniques/instrumentation , Micro-Electrical-Mechanical Systems/instrumentation , Peptide Fragments/chemistry , Protein Interaction Mapping/instrumentation , Sonication/instrumentation , Adsorption , Amyloid beta-Peptides/radiation effects , Equipment Design , Equipment Failure Analysis , Peptide Fragments/radiation effects , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
Real-time monitoring of the deposition processes of Aß1-40 and Aß1-42 peptides on various seeds has been performed using a 55 MHz wireless quartz-crystal microbalance (QCM) over long-time periods (~40 h). Dissolved peptide solutions were stirred for nucleation and growth of seeds at pH = 7.4 and 4.6, which were immobilized on the sensor chips. The isolated Aß peptides were then flowed at the neutral pH, focusing on the interaction between the seeds and the monomers (or small multimers), excluding other interactions among seeds and other aggregates. The thioflavin-T fluorescence assay and atomic-force microscopy were used for evaluating structures of the seeds and deposited aggregates. The deposition rate, determined by the frequency decrease, is about 100 monomers/nm(2)/year in the case of fibril formation. The notable deposition behavior was observed in the deposition of Aß1-40 peptide on Aß1-42 seeds grown at the lower pH, which can be an important model for Alzheimer's disease.
