Imaging Technology and Staining Techniques CHAPTER 1.3

 Three factors affect how well you can see an object in a microscope…  1. magnification  2. contrast  3. resolution

 In brightfield microscopy, light passes through cells which are seen as colourless.  Manipulating the light source can improve contrast  Stains and colouring agents also improve contrast (they kill the cells) CONTRAST

 Resolution, or resolving power, is the ability to distinguish between two structures that are very close together RESOLUTION The human eye can distinguish images of objects that are 0.1 mm or larger.

 In the early 1950’s, techniques were developed to improve images by altering the light path through the specimen  Darkfield  Phase contrast  Differential interference contrast illumination CONTRAST ENHANCING TECHNIQUES

 Gives information about molecules on the cell surface  Fluorescent molecules on specimen reflect UV light at different wavelengths, causing it to glow FLUORESCENCE MICROSCOPY

 A laser concentrates light onto a specimen  The reflection is passed through a tiny hole (confocal pinhole)  Reaches an electronic detector that converts light into image  Many slices of images are combined to form a 3D picture CONFOCAL TECHNOLOGY

 Uses beams of electrons instead of light waves (produces finer detail)  The image is formed by absorption or scattering of the electron beam  Electron-dense materials do not let the electrons pass through  Focus with electromagnetics ELECTRON MICROSCOPY

 Transmission electron microscope (TEM) depends on a beam of electrons passed through a very thin section of fixed and stained tissue embedded in plastic. The electrons fall on film and photographs are produced  Can magnify specimen up to x TEM

 Developed in 1940’s  Gives information of the surface features of the specimen  Show structural arrangements like the double layer of the cell membrane  Recently allows the use of live material SEM

FeatureLight MicroscopeElectron Microscope SourceLamp or laserElectron gun RadiationUV or visible lightElectron beam LensesCurved glass surfacesElectromagnets ReceiverEye or digital imageFluorescent screen or digital image FocusUp and down movement of lensesAdjustment of magnetic field COMPARISON OF LIGHT AND ELECTRON MICROSCOPES

 Scanning Tunnelling Microscope and Atomic Force Microscope are able to reveal even smaller structures than the TEM or SEM CHAPTER 1.4 – CELL RESEARCH

 The mapping of DNA sequences in genes involves may techniques…  Breaking cells down to release their DNA  Using Chemical techniques to make many copies of DNA  Finding the sequence of chemical subunits through computer analysis GENE MAPPING

 An open system is one that must interact with its environment to maintain its existence. CELL COMMUNICATION

 X-ray crystallography uses x-rays, special sensors that analyze patterns of x-ray scattering, and computer technology to allow scientists to learn the details of molecular structure to help them understand how the molecule works 3-D STRUCTURE