Solid-state NMR spectroscopy is used to characterize the interaction of L-cysteine with gold nanoparticles. The experiments show that there are two types of cysteine in the gold-cysteine complex, with nearly equal populations. We postulate that cysteine forms a two-layer boundary around the gold nanoparticles. The first layer is made of cysteine molecules forming a thiolate bond with the gold surface and having its charged amino and carboxyl groups oriented away from the gold surface. The second layer has its amino and carboxyl groups oriented toward the first layer and its sulfur group oriented away from the gold particles.

There is great interest in using proximal probe techniques to simultaneously image and measure physical properties of surfaces with nanoscale spatial resolution. In this regard, there have been recent innovations in generating time-resolved force interaction between the tip and surface during regular operation of tapping mode atomic force microscopy ͑TMAFM͒. These tip/sample forces can be used to measure physical material properties of surface in an analogous fashion to the well-established static force curve experiment. Since its inception, it has been recognized that operation of TMAFM in fluids differs significantly from that in air, with one of the major differences manifested in the quality factor ͑Q͒ of the cantilever. In air, Q is normally on the order of 200-400, whereas in fluids, it is of the order of approximately 1-5. In this study, we explore the impact of imaging parameters, i.e., set point ratio and free cantilever oscillation amplitude, on time varying tip-sample force interactions in fluid TMAFM via simulation and experiment. The numerical AFM model contains a feedback loop, allowing for the simulation of the entire scanning process. In this way, we explore the impact of varying the Young's modulus of the surface on the maximum tapping force.

Tapping mode atomic force microscopy (AFM) in solution was used to analyze the role of the internally located periplasmic flagella (PFs) of the Lyme disease spirochete Borrelia burgdorferi in withstanding externally applied cellular stresses. By systematically imaging immobilized spirochetes with increasing tapping forces, we found that mutants that lack PFs are more readily compressed and damaged by the imaging process compared to wild-type cells. This finding suggest that the PFs, aside from being essential for motility and involved in cell shape, play a cytoskeletal role in dissipating energy and maintaining cellular integrity in the presence of external stress.

Tissue analysis, which is essential to histology and is considered the benchmark for the diagnosis and prognosis of many illnesses, including cancer, is significant. During surgery, the surgical margin of...

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