Surface Stress Changes Induced by the Conformational Change of Proteins

Abstract

A potential binding assay based on conformational-change-induced micromechanical motion is described. Calmodulin was used to modify a microcantilever (MCL) by a self-assembled layer-by-layer approach. The results showed that the modified MCL bent when the proteins changed their conformation upon binding with Ca2+. The cantilever deflection amplitudes were different under different ionic strengths, indicating different degrees of conformational change of the proteins in these conditions. On the contrary, cantilevers modified by proteins, such as hemoglobin and myoglobin, that do not change conformations upon binding with analytes do not cause the cantilever deflection. These results suggest that the conformational changes of proteins may be used to develop cantilever biosensors, and the MCL system has potential for use in label-free, protein-analyte screening applications.

Investigation of Ph-Assisted Human Serum Albumin (HSA)-Cobalt (Co)Binding Using Nanomechanical Deflection and Circular Dichroism

“…Recently, pH-assisted conformation change of HSA was examined using microcantilever sensors, which showed the possibility of detecting conformational change of HSA by variation of pH using nanomechanical bending [33]. This study and many previous reports show that microcantilever sensors have the potential to be sensitive micromechanical pH sensors [33][34][35][36].…”

“…However, the complex ion is progressively washed away from the surface due to liquid flow as observed in all these experiments. The significant bending of the microcantilever shows conformational changes in the protein due to binding of Co(II) complex on the negatively charged globular protein in N (normal) conformation [31,33,34]. After binding with Co(II) complex, change in N conformation to an elongated protein structure is one possibility [50].…”

Probing the Interaction Between Cellulose and Cellulase with a Nanomechanical Sensor

“…Typical dimensions of a microcantilever, which are similar to AFM probes, are 200 μm long, 1 μm thick, and 20 μm wide (Goeders et al, 2008;Lavrik et al, 2004). The microcantilever is capable of detecting minute changes in interaction energy between individual molecules in the thin film of a polymer coating (cellulose, protein, DNA, or polymer brush) in the form of a measurable bending (10 -6 to 10 -12 m) of the microcantilever (Moulin et al, 1999;Mukhopadhyay et al, 2005;Shu et al, 2005;Yan et al, 2006;Zhao et al, 2010;Zhou et al, 2006). The microcantilever bending can be measured based on the deflection of a laser beam reflecting from the tip of the microcantilever in the AFM (Figure 9).…”

“…The surface stress and the deflection of the microcantilever are quantitatively related (Yan et al, 2006):…”

“…Using the static mode microcantilever sensor, Ji and coworkers investigated the conformational change of calmodulin (Yan et al, 2006). Sauers and coworkers successfully detected 2-mercaptoethanol using a gold-coated microcantilever (Datskos & Sauers, 1999).…”