Microscopy News Round Up - AFM examines Sickle Cell, 3-D Atomic-Resolution View of Nanoparticle, Twisting an Electron Beam

AFM examines Sickle Cell, 3-D Atomic-Resolution View of Nanoparticle, Twisting an Electron Beam

George Lykotrafitis from the University of Connecticut is examining the membranes of red blood cells with sickle cell anemia through the eyes of an engineer. He’s an assistant professor in the Department of Mechanical Engineering and is using atomic force microscopy (AFM) to measure the membrane stiffness of red blood cells with sickle cell and to quantify the concentration of proteins on the cell membrane that cause the cells to adhere to the lining of blood vessels, causing blockages and decreasing oxygen flow. An AFM needle coated with an antibody to a target protein will bind to the protein as it scans across the cell, building a map of the protein’s concentration across the membrane. The 3-D topographical AFM images shown are by graduate student Jamie Maciaszek. The deoxygenated red blood cells (A, B) from patients with sickle cell disease have a highly irregular morphology, compared to the characteristic biconcave shape of normal erythrocytes (C). Lykotrafitis hopes his research will answer questions about sickle cell disease such as how much red blood cell adhesion plays a role in the disease. Read more about Lykotrafitis’ research, including publications, on the Cellular Mechanics Laboratory website.

Scientists from Empa and ETH Zurich in collaboration with a Dutch team, have developed an electron microscopy method that can create an atomic resolution 3-D reconstruction of a nanoparticle. As published in a Nature paper, the researchers prepared silver nanoparticles in an aluminum matrix, which made it easier to tilt the silver nanoparticles in different crystallographic orientations under the electron beam while also protecting them from damage by the beam. The researchers used the TEAM0.5 microscope electron microscope at the Lawrence Berkeley National Laboratory. It has a maximum resolution of less than 50 picometers, about half the diameter of an atom. To protect the sample further, the electron microscope was set to produce images at an atomic resolution with a lower accelerating voltage (80 kilovolts rather than the normal 200 to 300 kilovolts). The researchers sharpened the resulting images, making it possible to count the individual silver atoms along different crystallographic directions. They then used only two images of an embedded silver nanoparticles to form a 3-D reconstruction by topographically reconstructing the atomic structure based on a mathematical algorithm. In the image, the yellow spheres graphically depict atoms that form the ~2 nm diameter silver nanoparticle. Previously only the rough outlines of nanoparticles could be visualized with images taken from different perspectives, and atomic structures could only be simulated on the computer. The new method might one day be used for applications such as determining which atom configurations become active on the surface of nanoparticles with a toxic or catalytic effect.

Researchers from National Institute of Standards and Technology and the University of Maryland, have found that passing an electron beam through a carefully prepared hologram twists the beam in a way that might allow higher-resolution images than a conventional transmission electron microscope (TEM). Imprinting angular momentum onto optical beams has already enhanced optical imaging, and since electrons also have wave-particle duality they can be described in terms of a characteristic wavelength. As described in a Science paper, the researchers produced an electron vortex beam by passing an electron beam through a hologram that can diffract electrons. They imparted a controlled amount of orbital angular momentum onto the electrons as they moved through the hologram grid by controlling the grid’s periodicity and building in a specialized defect. The electron vortex beam might allow electron energy-loss spectroscopy and spiral phase microscopy in a TEM. Spiral phase microscopy could enhance visibility of the edges in samples such as unstained biological specimens that have low absorption contrast, without a sacrifice in spatial resolution.

Coffee Break Moment...

Take a break, lean back in your chair and read the newest invited review paper in the Journal of Microscopy, “Optical complexities of living cytoplasm – implications for live cell imaging and photo-micromanipulation techniques.”  The authors point out that using light to manipulate the intracellular environment of living cells has led to a greater understanding of how cells react to their environment. However, there has been little discussion on how the optical properties of living cytoplasm influence such measurements and manipulations. They discuss the importance of understanding cytoplasm’s optical properties as well as how imperfections in experimental interpretation can arise.