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The Chemistry of Vision April 17, 2008 Andrew Isleib Eric Sterne Jonathan Arnold Min Eun Lee Samara Shiromani
Agenda <ul><li>Introduction: Retinol and Eye Biology </li></ul><ul><li>Chemistry of photoreception </li></ul><ul><li>Color...
Introduction <ul><li>Conjugated systems - Dr. Phillips presented   -Carotene and retinol </li></ul><ul><li>We will explai...
Introduction: Sources of Vitamin A (Retinol) <ul><li>Humans cannot synthesize retinol from scratch </li></ul><ul><ul><li>M...
Introduction: The Eye <ul><li>Photoreception takes place in Rod and Cone cells of the retina </li></ul>Retina Rod Cells Co...
<ul><li>- Opsin : Transmembrane G-Protein receptor </li></ul><ul><li>Retinal: Chromaphore responsible for visible light ab...
Introduction: Phototransduction <ul><li>A photon is absorbed by Rhodopsin which causes a conformational change in retinal ...
Introduction: Phototransduction <ul><li>The conformational change allows a G-protein to replace GDP with GTP - initiates t...
Chemistry: Retinal Binding <ul><li>Mechanism of Schiff Base (Imine) formation </li></ul><ul><ul><li>Lysine side chain ends...
Chemistry: Rhodopsin Absorption   <ul><li>Positive charge distributed over conjugated   -bond system </li></ul><ul><ul><...
Color Vision: Cone Cells
Color Vision <ul><li>Trichromatic Vision: Red, Green Blue </li></ul>
Ishihara Test <ul><li>What numbers do you see? </li></ul>
Color Blindness <ul><li>Missing or defective pigment proteins for certain cone cell types </li></ul><ul><ul><li>~8% of men...
Losing the Light <ul><li>Introduction to Age-Related Macular Degeneration </li></ul>
Normal Retina
Retina with AMD
Progression of AMD
Chemistry: A2E-epoxides <ul><li>A2E: autofluorescent pigment </li></ul><ul><ul><li>Pyridinium polar head group </li></ul><...
Conclusion <ul><li>Improved understanding of how we see? </li></ul><ul><li>Just found out you are color blind?  </li></ul>...
References <ul><li>Shichi, Hitoshi.  Biochemistry of Vision.  New York: Academic Press, 1983. </li></ul><ul><li>Chang, Ray...
References <ul><li>Ophartd, Charles, E. “Chemistry of Vision.” 2003. Elmhurst College. 15 Mar 2008.  <http://www.elmhurst....
References <ul><li>Nolan, Donia, E. “Normal Age Related Vision Loss and Related Services for the Elderly.” 2002. Stephen F...
Introduction <ul><li>Conjugated systems - Dr. Phillips presented   -Carotene and retinal </li></ul><ul><li>We will explai...
ß-Carotene
Vitamin A - All Trans Retinol <ul><li>Humans cannot synthesize retinol from scratch </li></ul><ul><ul><li>Must ingest it d...
Retinal to Vitamin A
Ishihara Test
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Chemistry Of Vision Final

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Transcript of "Chemistry Of Vision Final"

  1. 1. The Chemistry of Vision April 17, 2008 Andrew Isleib Eric Sterne Jonathan Arnold Min Eun Lee Samara Shiromani
  2. 2. Agenda <ul><li>Introduction: Retinol and Eye Biology </li></ul><ul><li>Chemistry of photoreception </li></ul><ul><li>Color Vision and Color Blindness </li></ul><ul><li>Macular Degeneration </li></ul><ul><li>Concluding Remarks </li></ul><ul><li>References </li></ul>
  3. 3. Introduction <ul><li>Conjugated systems - Dr. Phillips presented  -Carotene and retinol </li></ul><ul><li>We will explain retinol’s role in vision and problems with vision </li></ul><ul><ul><li>Retinal - Aldehyde form of Retinol </li></ul></ul>
  4. 4. Introduction: Sources of Vitamin A (Retinol) <ul><li>Humans cannot synthesize retinol from scratch </li></ul><ul><ul><li>Must ingest it directly or one of its precursors </li></ul></ul><ul><li>Animal sources of preformed vitamin A </li></ul><ul><ul><li>Liver, Milk, Butter, Cheese, Egg Yolk </li></ul></ul><ul><li>Provitamin A Carotenoids - convertible into vitamin A in body </li></ul><ul><ul><li>Beta-Carotene: Carrots, Spinich, Kale, Collard Greens, Sweet Potatoes, Pumpkin, Cantaloupe </li></ul></ul><ul><ul><li>Lutein and Zeaxanthin </li></ul></ul>
  5. 5. Introduction: The Eye <ul><li>Photoreception takes place in Rod and Cone cells of the retina </li></ul>Retina Rod Cells Cone Cell
  6. 6. <ul><li>- Opsin : Transmembrane G-Protein receptor </li></ul><ul><li>Retinal: Chromaphore responsible for visible light absorption </li></ul><ul><li>Retinal + Opsin = Rhodopsin </li></ul>Introduction: Rhodopsin
  7. 7. Introduction: Phototransduction <ul><li>A photon is absorbed by Rhodopsin which causes a conformational change in retinal </li></ul>11-Cis Retinal
  8. 8. Introduction: Phototransduction <ul><li>The conformational change allows a G-protein to replace GDP with GTP - initiates transduction pathway. </li></ul>“ All-Trans” Retinal
  9. 9. Chemistry: Retinal Binding <ul><li>Mechanism of Schiff Base (Imine) formation </li></ul><ul><ul><li>Lysine side chain ends in -NH2 </li></ul></ul>
  10. 10. Chemistry: Rhodopsin Absorption  <ul><li>Positive charge distributed over conjugated  -bond system </li></ul><ul><ul><li>Stabilized by amino acid environment </li></ul></ul><ul><ul><li>Narrows distance between HOMO and LUMO: Red Shift </li></ul></ul><ul><li>Entire photon must be absorbed </li></ul><ul><ul><li>Lower energy - Longer wavelength </li></ul></ul>MO Energy HOMO LUMO HOMO LUMO Retinal Rhodopsin  max = 370nm  max = 498nm MO Energy
  11. 11. Color Vision: Cone Cells
  12. 12. Color Vision <ul><li>Trichromatic Vision: Red, Green Blue </li></ul>
  13. 13. Ishihara Test <ul><li>What numbers do you see? </li></ul>
  14. 14. Color Blindness <ul><li>Missing or defective pigment proteins for certain cone cell types </li></ul><ul><ul><li>~8% of men, rare in women </li></ul></ul><ul><ul><li>X chromosome codes for cones </li></ul></ul><ul><li>Types of Color Blindness </li></ul><ul><ul><li>Achromatopsia - black and white vision </li></ul></ul><ul><ul><li>Dichromacy - 2 functioning cone types </li></ul></ul><ul><ul><li>Anomalous Trichromacy - shifted cone absorption </li></ul></ul><ul><li>Non-Genetic Causes </li></ul><ul><ul><li>Disease, Accidents, Medication </li></ul></ul>
  15. 15. Losing the Light <ul><li>Introduction to Age-Related Macular Degeneration </li></ul>
  16. 16. Normal Retina
  17. 17. Retina with AMD
  18. 18. Progression of AMD
  19. 19. Chemistry: A2E-epoxides <ul><li>A2E: autofluorescent pigment </li></ul><ul><ul><li>Pyridinium polar head group </li></ul></ul><ul><ul><li>Two hydrophobic retinoid tails </li></ul></ul><ul><li>With light A2E creates epoxides at its C=C double bonds </li></ul><ul><li>A2E-epoxides damage DNA </li></ul><ul><ul><li>DNA Lesions, Altered gene expression </li></ul></ul><ul><ul><li>Potential link to AMD </li></ul></ul><ul><li>Vitamin E and C reduce A2E-epoxide </li></ul>
  20. 20. Conclusion <ul><li>Improved understanding of how we see? </li></ul><ul><li>Just found out you are color blind? </li></ul><ul><ul><li>Support Group: </li></ul></ul><ul><ul><li>http://dailystrength.org/c/Color-Blindness/support-group </li></ul></ul><ul><li>Age Related Macular Degeneration </li></ul><ul><ul><li>Antioxidants: protect your vision as you age </li></ul></ul><ul><li>See Better: keep up your supply of retinol </li></ul><ul><ul><li>Eat your carrots, greens, liver, etc. </li></ul></ul>
  21. 21. References <ul><li>Shichi, Hitoshi. Biochemistry of Vision. New York: Academic Press, 1983. </li></ul><ul><li>Chang, Raymond. Physical Chemistry for the Biosciences. Sausalito, California: United Science Books, 2005. </li></ul><ul><li>Lugtenburg, Johan, Muradin-Szweykowska, Maria, Heeremans, Carola, and Pardoen, Johannes A. “Mechanism for the opsin shift of retinal's absorption in bacteriorhodopsin.” J. Am. Chem. Soc., 108, 11, 3104 - 3105, 1986, 10.1021/ja00271a050. </li></ul><ul><li>Wachtler, T. Doi, E., Lee, T.-W., & Sejnowski, T.J. (2007). &quot;Cone selectivity derived from the responses of the retinal cone mosaic to natural scenes. Journal of Vision, 7(8):6, 1-14. <http://www.journalofvision.org/7/8/6/>, doi:10.1167/7.8.6. </li></ul><ul><li>Casidy, Rachel and Regina Frey. “’I Have Seen the Light!’: Vision and Light-Induced Molecular Changes.” Department of Chemistry. 2000. Washington University. 25 Mar 2008, <http://www.chemistry.wustl.edu/~edudev/LabTutorials/Vision/Vision.html>. </li></ul><ul><li>Ishihara Test for Color Blindness. <http://www.toledo-bend.com/colorblind.Ishihara.html> </li></ul>
  22. 22. References <ul><li>Ophartd, Charles, E. “Chemistry of Vision.” 2003. Elmhurst College. 15 Mar 2008. <http://www.elmhurst.edu/~chm/vchembook/531vision.html>. </li></ul><ul><li>Ophartd, Charles, E. “Beta-Carotene and Vitamin A.” 2003. Elmhurst College. 15 Mar 2008. <http://www.elmhurst.edu/~chm/vchembook/532vitaminA.html> </li></ul><ul><li>Dutton, Frank. “Ishihara Test for Color Blindness.” 2 Apr 2008. <http://www.toledo-bend.com/colorblind/Ishihara.html> </li></ul><ul><li>Sparrow, Janet R., Heidi R. Vollmer-Snarr, Jilin Zhou, Young P. Jang, Steffen Jockusch, Yasuhiro Itagaki, and Koji Nakanishi. “A2E-epoxides Damage DNA in Retinal Pigment Epithelial Cells: Vitamin E and Other Antioxidants Inhibit A2E-Epoxide Formation.” The Journal of Biological Chemistry. Vol. 278, No. 20, Issue of May 16, pp. 18207–18213, 2003. </li></ul><ul><li>Wade, L. G. Jr. Organic Chemistry. Sixth Edition, New Jersey: Pearson Prentice Hall, 2006 </li></ul><ul><li>Yamadaa, A. T. Kakitania, S. Yamamotob and T. Yamato. “A computational study on the stability of the protonated Schiff base of retinal in rhodopsin.” Chemical Physical Letters, Vol. 366, Issues 5-6, 20 December, pp. 670-675, 2002 </li></ul>
  23. 23. References <ul><li>Nolan, Donia, E. “Normal Age Related Vision Loss and Related Services for the Elderly.” 2002. Stephen F. Austin State University. 20 Mar. 2008. <http://hubel.sfasu.edu/research/donia/aging_visual_changes.htm> </li></ul><ul><li>Bowmaker J.K. and Dartnall H.J.A., &quot;Visual pigments of rods and cones in a human retina.&quot; J. Physiol. 298: pp501-511 (1980). </li></ul><ul><li>“ Sensory Systems.” 2006. Bellarmine University Department of Biology. 2 Apr. 2008. <http://cas.bellarmine.edu/tietjen/HumanBioogy/sensory_systems.htm> </li></ul><ul><li>Gill, Cynthia. “Web Page for Bio 416L.” 2007. Hampshire College. 2 Apr. 2008 <http://helios.hampshire.edu/~cjgNS/sputtbug/416l/HumanPhys.html> </li></ul><ul><li>Polans A, Baehr W, and Palczewski K. “Turned on by Ca2+! The physiology and pathology of Ca2+-binding proteins in the retina.” Trends in Neurosciences. vol. 19(12). 1996. Pages 547-554 </li></ul><ul><li>Ramón y Cajal, Santiago. “Drawing of Layers of Retina.” Online Image. 1911. Wikipedia. 21 Mar. 2008. <http://en.wikipedia.org/wiki/Image:Fig_retine.png> </li></ul><ul><li>Escher, M.C. “Eye.” Online Image. 1946. Pictures by M.C Escher. 15 Mar 2008. <http://aaronbaird.net/pictures/Escher/> </li></ul><ul><li>Omikron, “Magnified image of the rods and cones of the human eye.” Free Health Encyclopedia. 3 Apr. 2008. <http://www.faqs.org/health/Sick-V1/Color-Blindness.html> </li></ul>
  24. 24. Introduction <ul><li>Conjugated systems - Dr. Phillips presented  -Carotene and retinal </li></ul><ul><li>We will explain retinal’s role in vision and problems with vision </li></ul>
  25. 25. ß-Carotene
  26. 26. Vitamin A - All Trans Retinol <ul><li>Humans cannot synthesize retinol from scratch </li></ul><ul><ul><li>Must ingest it directly or one of its precursors </li></ul></ul>
  27. 27. Retinal to Vitamin A
  28. 28. Ishihara Test
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