This news item was created by Lindsey Atkinson, Mary Davis, and Darwin Mack as part of their Chemistry 212 Group Project in WS00 under the guidance of Prof. Rainer Glaser.

Glaser's "Chemistry is in the News"
To Accompany Wade Organic Chemistry 4/e.
Chapter 24. Amino Acids, Peptides, and Proteins.

For each of the following questions, please refer to the following article:

(BBC News online, May 20, 1999)

Editorial Comments

Genetically Modified Organisms, or GMO's, are becoming a very important, and possibly hazardous part of our society. Science has made enormous strides in the past century. Things are evolving so rapidly, that at times we do not have the opportunity to think about all of the issues involved in a scientific discovery, until it has already been discovered. This is one of the major problems that GMO's face today.

Genetically modified corn (Bt-corn) is the most widely used GMO crop, at this time. Bt-corn has been genetically altered to produce its own toxin that is specific to its enemy, the corn borer. Bacillus thuringiensis (Bt) is an insecticidal bacterium that contains protein toxins which have a specific mode of action. The Bt protein toxin has been genetically inserted into the corn seed, allowing it to produce its own toxins, or insecticides. Its specific mode of action is based on the acid-base properties of the amino acid toxin within the gut of the borer. The basic conditions in the gut of the corn borer allows the protein toxin to be solubilised. These basic conditions do not exist in humans and higher animals, therefore we do not have any risks to the toxin.

Bt-corn gives farmers some outstanding advantages, such as: higher yields because there is much less crop damage, and less usage, if any, of spray insecticides. But, there are also many environmental issues involved with the usage of GMO crops. It has been discovered that Bt-corn may not be as specific as previously thought. Lab studies have shown that the larvae of the monarch butterfly is at risk to the Bt toxin. Monarch's feed on the milkweed that is found near corn fields. It is possible for the pollen, carrying the toxin from the corn plant, to find its way to the milkweed plant. Another issue environmentalists are concerned with is the acquired resistance to the Bt toxin. Bt resistance is the same type of situation that is occurring with antibiotics in humans, i.e. penicillin. Steps are being taken to help ensure the safety of Bt-corn, but there is no perfect solution as of yet.

Pertinent Text References
Chapter 24. Amino Acids, Peptides, and Proteins.
See in particular the discussion of Acid-Base Properties of Amino Acids in Wade 4/e, p. 1118.


Question 1: What specific pH is required for the toxin to be solubilised? See "Acid -Base properties" link

Answer: 9.5

Question 2: Suggest a general mode of action for the Bacillus thuringiensis amino acid in the corn borer gut. (Hint: Acid-Base Properties)

Answer: The bacillus thuringiensis goes from the zwitterionic form to the anionic form in the basic conditions found in the gut of the corn borer. This makes the protein soluble and allows it to bind to specific sites in the borer gut.

Question 3: What is the enzyme that is the receptor for the Bt toxin in the corn borer gut? See "Acid-Base properties" link

Answer: aminopeptidase-N

Question 4: Can you find a figure in the news article that gives the dollar amount of corn damaged each year by the corn borer?

Answer: $1.2 billion

Question 5: List the advantages and disadvantages for the usage of GMO crops from a farmer's perspective and an environmentalist's perspective. Can you suggest a workable solution, taking into account both perspectives?

Answer: Open to interpretation. We just wanted to make everyone think about all of the different perspectives.