RESUMO
Atomic force microscopy (AFM) is a powerful technique for imaging molecules, macromolecular complexes, and nanoparticles with nanometer resolution. However, AFM images are distorted by the shape of the tip used. These distortions can be corrected if the tip shape can be determined by scanning a sample with features sharper than the tip and higher than the object of interest. Here we present a 3D DNA origami structure as fiducial for tip reconstruction and image correction. Our fiducial is stable under a broad range of conditions and has sharp steps at different heights that enable reliable tip reconstruction from as few as ten fiducials. The DNA origami is readily codeposited with biological and nonbiological samples, achieves higher precision for the tip apex than polycrystalline samples, and dramatically improves the accuracy of the lateral dimensions determined from the images. Our fiducial thus enables accurate and precise AFM imaging for a broad range of applications.
Assuntos
DNA , Nanopartículas , Microscopia de Força Atômica/métodos , DNA/químicaRESUMO
We have quantified the structure of the colloidal gas-liquid interface using synchrotron X-ray reflectivity measurements on a model colloid-polymer mixture. The interfacial width shows mean-field scaling with the colloid density difference, and the density profiles appear to be monotonic. Furthermore, our measurements allow us to distinguish between different theoretical polymer descriptions commonly used to model colloid-polymer mixtures. Our results highlight the importance of capturing the correct polymer physics in obtaining a quantitative theoretical description of the colloidal gas-liquid interface.
