Limitations of constant-force-feedback experiments.

Single-molecule force spectroscopy has provided important insights into the properties and mechanisms of biological molecules and systems. A common experiment is to measure the force dependence of conformational changes at equilibrium. Here, we demonstrate that the commonly used technique of force feedback has severe limitations when used to evaluate rapid macromolecular conformational transitions.

Direct observation of a force-induced switch in the anisotropic mechanical unfolding pathway of a protein.

Many biological processes generate force, and proteins have evolved to resist and respond to tension along different force axes. Single-molecule force spectroscopy allows for molecular insight into the behavior of proteins under force and the mechanism of protein folding in general. Here, we have used src SH3 to investigate the effect of different pulling axes under the low-force regime afforded by an optical trap.

The molten globule state is unusually deformable under mechanical force.

Recently, the role of force in cellular processes has become more evident, and now with advances in force spectroscopy, the response of proteins to force can be directly studied. Such studies have found that native proteins are brittle, and thus not very deformable. Here, we examine the mechanical properties of a class of intermediates referred to as the molten globule state.

Development of a protein chip: a MS-based method for quantitation of protein expression and modification levels using an immunoaffinity approach.

Protein chip technology permits analysis of the expression and modification status of numerous targeted proteins within a single experiment, mainly through the use of antibody-based microarrays. Despite recent improvements in these protein chips, their applications are still limited for a variety of reasons, which include technical challenges in fabrication of the antibody chips as well as the very low specificity achieved by current detection methods. We have developed a unique approach for relative and/or absolute quantitation of protein expression and modification based on the capture of epitope peptides on affinity beads, which can be used to develop a mass-spectrometry-based protein chip technology.