3D Movies of Microscopic Systems

Juli 29, 2009

Physicists at New York University (NYU), US have developed a technique to record three-dimensional movies of microscopic systems, such as biological molecules, through holographic video. The technique, developed in the laboratory of NYU Physics Professor David Grier, is comprised of two components: making and recording the images of microscopic systems and then analyzing these images. To generate and record images, the researchers created a holographic microscope. It is based on a conventional light microscope, which uses a collimated laser beam instead of on an incandescent illuminator.
When an object is placed into path of the microscope’s beam, the object scatters some of the beam’s light into a complex diffraction pattern. The scattered light overlaps with the original beam to create an interference pattern reminiscent of overlapping ripples in a pool of water. The microscope then magnifies the resulting pattern of light and dark and records it with a conventional digital video recorder. Each snapshot in the resulting video stream is a hologram of the original object. Unlike a conventional photograph, each holographic snapshot stores information about the three-dimensional structure and composition of the object that created the scattered light field. The recorded holograms appear as a pattern of concentric light and dark rings.
For analyzing the images the researchers based their work on a quantitative theory, the Lorenz-Mie theory, which maintains that the way light is scattered can reveal the size and composition of the object that is scattering it.
The application of the technique ranges from research in fundamental statistical physics to analyzing the composition of fat droplets in milk.
www.nyu.edu

In the microscope, a laser beam illuminates the sample. Light scattered by the sample creates an interference pattern which is magnified and recorded. Then measurements of the particle’s position, size, and refractive index are obtained.

In the microscope, a laser beam illuminates the sample. Light scattered by the sample creates an interference pattern which is magnified and recorded. Then measurements of the particle’s position, size, and refractive index are obtained.


Distinguishing Single Cells With Nothing But Light

April 6, 2009

Researchers at the University of Rochester have developed a novel optical technique that permits rapid analysis of single human immune cells using only light. Andrew Berger, associate professor of optics and his graduate student Zachary Smith integrated Raman and angular-scattering microscopy into a single system, which they call IRAM. This is the first time clear differences between two types of immune cells have been seen using a microscopy system that gathers chemical and structural information by combining two previously distinct optical techniques, according to Berger. „Conceptually it’s pretty straightforward – you shine a specified wavelength of light onto your sample and you get back a large number of peaks spread out like a rainbow,“ says Berger. „The peaks tell you how the molecules you’re studying vibrate and together the vibrations give you the chemical information.“ Until now scientists have not had a non-invasive way to see how human cells, like T cells or cancer cells, activate individually and evolve over time.
www.rochester.edu

IRAM scattering data from a single granulocyte.

IRAM scattering data from a single granulocyte.

IRAM scattering data from a single lymphocyte. Clear differences are visible when compared to data from a granulocyte.

IRAM scattering data from a single lymphocyte. Clear differences are visible when compared to data from a granulocyte.