Advances in Bioscience Education Summer Workshop

1. Advances in Bioscience Education Summer Workshop Immunolabeling for Fluorescence and Electron Microscopy June 27 - 29, 2006 Biological Electron Microscope Facility Pacific Biosciences Research Center University of Hawai’i at Manoa

2. Biological Electron Microscope Facility • Pacific Biosciences Research Center, University of Hawai’i at Manoa • Instrumentation, service and training • State-of-the-art instruments for biological microscopy • In operation since 1984 • Personnel: • Dr. Richard D. Allen, Director • Dr. Marilyn F. Dunlap, Manager • Tina M. (Weatherby) Carvalho, M.S., Supervisor

3. Light and Electron Microscopy • Light microscopy • Glass lenses • Source of illumination is usually light of visible wavelengths • Tungsten bulb • Mercury vapor or Xenon lamp • Laser • Electron microscopy • Electromagnetic lenses • Source of illumination is electrons • Hairpin tungsten filament (thermionic emission) • Pointed tungsten crystal (cold cathode field emission) • Lanthanum hexaboride

4. Epifluorescence Microscopy • Olympus BX51 upright microscope • Broad-band epifluorescence excitation and detection • DIC optics • Optronics scientific grade digital camera

5. Epifluorescence Green photos courtesy Dr. Teena Michaels, KCC Red photo courtesy Dr. Claude Jourdan-LeSaux

6. Common FluorescenceApplications • Localize/identify specific organelles • Detect live cells vs. dead cells, necrotic vs. apoptotic cells • Determine cell membrane permeability • Localize antigen-specific molecules • Multiple labeling

7. Laser Scanning Confocal Microscope • Olympus Fluoview FV1000 • Three colors + Trans-mitted simultaneously • Excitation with 405, 458, 488, 515, 543, and 633 nm lasers • Various emission filters • Optical sectioning • 3-D reconstruction • Stereo views • Animations

8. Laser Scanning Confocal Microscopy • Adjustable pinhole aperture eliminates out-of-focus glare • Better resolution • Serial optical sections can be collected from thick specimens • Live or fixed cell and tissue imaging Drosophila eye Photo courtesy of Gregg Meada & Dr. Gert DeCouet, UHM

9. Epifluorescence vs. Confocal Sample courtesy Gregg Meada & Dr. Gert DeCouet, UHM

10. Field Emission Scanning Electron Microscopy (FESEM) • Hitachi S-800 FESEM • High magnification (40x to 300,000x) • High resolution (better than 2 nm) • Easy to learn • Hi-res digital images • Prep equipment: critical point dryer, sputter coater

11. SEM Images

12. Transmission Electron Microscopy(TEM) • Zeiss 10/A conventional TEM • Excellent for training • Film only

13. LEO 912 Energy-Filtering TEM • In-column energy filter (electromagnetic prism) • Ultrathin to 0.5 µm sections • Contrast tuning • Elemental analysis with electron energy loss spectroscopy (EELS) • Elemental mapping with electron spectrographic imaging (ESI) • Eucentric goniometer stage • Digital images

14. Conventional TEM Micrographs Bacteria in cell Apoptosis Skin Chloroplast Collagen Virus in cell

15. Negative Staining • Viruses, small particles, proteins, molecules • No sectioning • Same day results

16. EFTEM - Electron Spectrographic Imaging (ESI) - elemental mapping • Calcium in mitochrondria from ischemic brain • Iron in liver

17. EFTEM- Electron Energy Loss Spectroscopy (EELS) • EELS spectrum

18. Ultramicrotomy • Ultrathin (60-90 nm) sectioning of resin-embedded specimens • Several brands/models available • Cryoultramicrotomy

19. Cryotechniques • Ultrarapid cryofixation • Metal mirror impact • Liquid propane plunge • Freeze fracture with Balzers 400T • Cryosubstitution • Cryoultramicrotomy – Ultrathin frozen sections (primarily for antibody labeling)

20. Cryo Examples • Freeze fracture, deep-etch, rotary shadow • Cryosection/im-munogold label • Cryosubstitution

21. Image Manipulation and Analysis • Soft Imaging System analySIS professional software • EFTEM acquisition and analysis • Light Microscopy • Images from other sources • Particle counting and analysis • Feature extraction • Image and results database

22. Immunolocalization • LM • Fluor/confocal • TEM • SEM with backscatter detector

23. Approaches to Immunolabeling • Direct Method: Primary antibody contains label • Indirect Method: Primary antibody followed by labeled secondary antibody • Amplified Method: Methods to add more reporter to labeled site • Protein A Method: May be used as secondary reagent instead of antibody

24. Direct Labeling Method • Labeled primary antibody reacts directly with the antigen in the histological or cytological preparation

25. Two-step Indirect Method • Fluorescent-conjugated secondary antibody attaches to primary antibody that is bound to antigen

26. Amplified Method • If the antibody reporter signal is weak, the signal can be amplified by several methods, e.g., streptavidin-biotin complex

27. Double-labeling Method • Use primary antibodies derived from different animals (e.g., one mouse antibody and one rabbit antibody) • Then use two secondary antibodies conjugated with reporters that can be distinguished from one another

28. Immunolabeling for Transmission Electron Microscopy • Normally do Two-Step Method • Primary antibody applied followed by colloidal gold-labeled secondary antibody • May also be enhanced with silver • Can also do for LM

29. Preparation of Biological Specimens for Immunolabeling • The goal is to preserve tissue as closely as possible to its natural state while at the same time maintaining the ability of the antigen to react with the antibody • Chemical fixation of whole mounts prior to labeling for LM • Chemical fixation, dehydration, and embedment in paraffin or resin for sectioning for LM or TEM • Chemical fixation for cryosections for LM • Cryofixation for LM or TEM

30. Chemical Fixation • Antigenic sites are easily denatured or masked during chemical fixation • Glutaraldehyde gives good fixation but may mask antigens, plus it is fluorescent • Paraformaldehyde often better choice, but results in poor morphology , especially for electron microscopy • May use e.g., 4% paraformaldehyde with 0.5% glutaraldehyde as a good compromise

31. Preembedding or Postembedding Labeling • May use preembedding labeling for surface antigens or for permeabilized cells • The advantage is that antigenicity is more likely preserved • Postembedding labeling is performed on sectioned tissue, on grids, allowing access to internal antigens • Antigenicity probably partially compromised by embedding

32. Steps in Labeling of Sections • Chemical fixation • Dehydration, infiltration, embedding and sectioning • Optional etching of embedment, permeabilization • Blocking • Incubation with primary antibody • Washing • Incubation with secondary antibody congugated with reporter (fluorescent probe, colloidal gold) • Washing, optional counterstaining • Mount and view

33. Controls! Controls! Controls! • Omit primary antibody • Irrelevant primary antibody • Pre-immune serum • Perform positive control • Check for autofluorescence • Check for non-specific labeling • Dilution series

34. Dilutions are Important • Typically should do an extensive dilution series to determine best concentration of both primary and secondary antibodies • This shows an antibody at concentrations of 1:100 and 1:2000

35. Know Your Artifacts • And use them to your advantage! • Green is label; orange-red is autofluorescence • Acts as counterstain

36. Autofluorescence • Need to select label that will be readily distinguished from autofluorescence • Several techniques to quench autofluorescence

37. What is a Microscope? • A tool that magnifies and improves resolution of the components of a structure • Has three components: one or more sources of illumination, a magnifying system, and one or more detectors • Light microscopes use a beam of light for illumination and include fluorescence and confocal microscopes • Electron microscopes use electrons as a source of illumination and include transmission and scanning electron microscopes

38. Light and Electron Microscopes • Lenses are used to control a beam of illumination, magnify, and direct an image to a detector

39. Light Microscopes

40. Objective Lenses • Objective lens choice is important! • Not all objective lenses are created equal • The more correction a lens has, the less transmission • Resolution is dictated by Numerical Aperture (NA) • Talk to your microscope company representative

41. Light Microscopes - Resolution • Resolution depends on the light gathering of the objective, which depends on the NA, and on the light path, which includes the slide, sample, mountingmedium,coverslip, and air or immersion oil

42. Light Path in Fluorescence • Light delivered through excitation filter and then objective lens to specimen where it is absorbed; emitted light goes back through objective lens through barrier filter and emission filter and then to detector.

43. Fluorescence Microscopes • Illumination light path is the same as the sampling light path • Need to maximize the light throughput in both directions – no more than 22% of light will be detected on a good day • Need to match refractive indices (RI) • Use the best optics with the fewest elements

44. Optical Choices for Fluorescence • Minimize the number of lens elements to increase light throughput, but correct for spherical aberration • Optimize magnification and NA; best choice often a 60X 1.4NA plan objective • Only use magnification required to collect the information needed • Use a mercury lamp for normal work and a xenon lamp for quantitative studies

45. Kohler Illumination • Kohler illumination is essential for good transmitted light contrast • Focus slide • Close field diaphragm • Focus diaphragm in field by adjusting condenser height • Center diaphragm in field • Open diaphragm to fill field and recheck centration • Adjust iris diaphragm (on condenser) to taste (affects contrast and depth of focus)

46. Elements of Fluorescence Microscope • Light source • Mercury vapor • Xenon • Laser • Optical lenses • Optical filters • Detection system • Eye • Film camera • Digital camera • Photomultiplier tube (PMT)

47. Fluorescence • Photons of a certain energy excite the fluorochrome, raising it to a higher energy state, and as it falls back to it’s original state it releases energy in the form of a photon of lower energy than the excitation energy.

48. Fluorescence • Fluorochromes are excited by specific wavelengths of light and emit specific wavelengths of a lower energy (longer wavelength)

49. Filter Cubes for Fluorescence • Filter cubes generally have an excitation filter, a dichroic element, and an emission filter • The elements of a cube are selected for the excitation and fluorescence detection desired

50. Classification of Filters • Long pass – passes longer wavelengths • Short pass – passes shorter wavelengths • Band pass – passes defined wavelengths • Dichromatic mirror – transmits long wavelengths, reflects shorter wavelengths