NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE Rice ’n Beans or Ricin Beans? A Deadly Swap by Ann T.S. Taylor Department of Chemistry Wabash College, Crawfordsville, IN “Hi Mom, I’m home!” Taylor gave her mom a hug and handed her a laundry bag. “I’m starving. What’s for dinner?” “Rice and beans … that’s all we can afford after this semester’s tuition bill.” Mom laughed. “Better make sure they aren’t ricin beans, dear.” Dad peeked his head over the newspaper. “But seriously, Taylor, I’m so glad you’re home! How were midterms?” Taylor joined her dad at the breakfast nook table. “Good, though I’m not done yet. I have a paper assignment due next Friday—I have to find a natural poison and explain how it works. What was up with the ricin beans?” Dad chuckled and showed Taylor an article. “Remember the poisonous letter sent to a politician? When they confronted one of the suspects, he thought they were talking about rice, not ricin.1 But then again, he was an Elvis impersonator, he probably doesn’t read National Geographic very much.” Mom chimed in. “You mean that National Geographic article about how ricin works?2 I thought it was fascinating that ricin is a protein found in castor beans. I guess that’s another reason to avoid Grandma’s castor oil fix for everything.” Taylor was quiet for a minute. “Ricin comes from castor beans? That might be perfect for my project. Is that the poison that was on Breaking Bad that one time?3 It’s strange to think that a protein from a bean plant could kill a person. How does the plant not die from it?” “That does sound perfect for your project, Taylor,” Dad replied. “And remember, there are lots of poisonous things in nature. Natural doesn’t mean not dangerous—just think about hemlock, mushrooms, and puffer fish.”4 “Taylor, when you are done with your project, could you please email Dad and I something we could understand?” Mom asked as she joined them at the table. “I’d like to know more about how ricin affects cells, but that is definitely your area of expertise.” “Sure,” Taylor replied. “I appreciate how supportive you are of my education. But can we talk about something else during dinner? Poison and dinner just don’t go well together.” “Definitely. I don’t want to think about ricin beans as I eat my rice and beans either,” Dad quipped. “So how is your dating life? No, I take it back…that makes me almost as sick to my stomach as poison discussion does!” 1 ABC News video story. April 24, 2013. Ricin suspect released: “I don’t even eat rice”; remark occurs at 0:55 in video at http://abcnews.go.com/ GMA/video/ricin-letters-mailed-obama-elvis-impersonator-suspect-released-19029161, accessed 6/2/14. 2 Newman, C. April 19, 2013. Ricin back in the headlines: what is it? National Geographic News, http://news.nationalgeographic.com/ news/2013/13/130417-ricin-letter-poison-obama-roger-wicker-toxicology/, accessed 5/27/15. 3 Locker, M. April 17, 2013. Ricin attack sadly familiar to fans of Breaking Bad. Time. http://entertainment.time.com/2013/04/17/ricinattacks-sadly-familiar-to-fans-of-breaking-bad/ accessed 5/27/15. 4 Illinois Poison Center Blog. September 16, 2011. Mother Nature’s most dangerous toxins. http://ipcblog.org/2011/09/06/mother-natures-mosttoxic/ accessed 5/27/15. “Rice ’n Beans or Ricin Beans?” by Ann T.S. Taylor Page 1 NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE Part I – An Early Experiment Taylor comes to you and the rest of your small group, asking for help with this project. You start digging in the literature and find some useful references. An early experiment into the mechanism of ricin was published in 1971 (Lin et al.). The experiment measured the incorporation rate of 3H labelled leucine, 3H labelled thymidine, and 3H labeled uridine into tumor cells treated with varying concentrations of ricin (Figure 1). Figure 1. Incorporation of tritiated reagents in tumor cells (Lin et al., 1971). Questions 1. Why were these three particular radioactive tracers used in this experiment? What process was each tracer monitoring? 2. What do you think was the hypothesis the researchers were testing? 3. What new hypothesis can be formed from these results? 4. Design an experiment to test your hypothesis. “Rice ’n Beans or Ricin Beans?” by Ann T.S. Taylor Page 2 NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE Part II – Inhibition In Vitro Another study looked at ricin inhibition of in vitro translation (Olsnes and Pihl, 972). 5. Make a list of all the components you would need to make an in vitro translation system. 6. In this experiment, the researchers “cheated”—they used a cell extract from rabbit reticulocytes. Mark with an asterisk all the components you listed in (5) that would be provided in a cell extract. 7. The researchers also added 15 mM creatine phosphate and 50 μg/mL creatine kinase. What is the role of these components? 8. Look at the figure legend for Figure 2. a. Why was the system pre-incubated for 40 minutes in the absence of labelled compounds? b. What is the role of the poly-U? c. What process did this experiment monitor? d. Why is the background level of incorporation not zero? 9. What conclusion can be drawn from this experiment? “Rice ’n Beans or Ricin Beans?” by Ann T.S. Taylor Figure 2. Effect of ricin on polyphenylalanine synthesis. A cell free system was preincubated at 28° for 40 minutes in the absence of labelled compounds. Then 4 μCi of 14C phenylalanine was added, and the system was divided into three equal samples. One sample () was used as a control, another sample () contained 100 μg of poly-U and a third sample (×) contained 100 μg of poly-U and 0.5 μg of ricin. The samples were incubated at 28°C and aliquots were removed as indicated, and the acid-precipitatable radioactivity was determined. Source: Redrawn from Figure 2 of Olsnes and Phl, 1972. Page 3 
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