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Nano-Size Sewing of Chemical Substance

by Tatsuhiro Tsukamoto
PhD student, University of Chicago

• Tsukamoto’s research is centered on the issue of effectively producing new chemical substances such as organic compounds.

• Our daily life is supported by all sorts of chemical substances, from face wash, toothpaste, shampoo and lotion to a wide range of medicines that work within our bodies to alleviate fever, headache, etc. Tsukamoto has been working to develop methods to produce such substances to meet our needs.

• For example, salicylic acid in typical acne face wash, aspirin as in painkiller, and menthol in chewing gums and toothpastes all have relatively simple chemical structure, while that of Taxol, a well-known anti-cancer drug, is fairly complex.

• Taxol is made of substance extracted from bark of a tree that is known to have a powerful anti-cancer effect. It would take tons of cut-down trees to obtain a few milligrams of Taxol. Can it be chemically synthesized in a test tube at a lab?

• It would require more processes to artificially produce it in proportion to the complexity of the chemical structure of the substance to be emulated. Tsukamoto’s goal is to make these processes more effective and shorten the time to create the targeted chemical.

• A complex compound can’t be obtained through a single step of chemical reaction; it requires numerous steps. For example, the effectiveness rate of obtaining a compound in one chemical reaction is 90% if you get 90 grams of the compound out of 100 grams of the starting material. At this rate, the final compound you get after 10 steps of chemical reactions will be 30 to 40 grams. If the rate is 80%, the final product would be only about 10% of the starting material after 10 steps. The only solution to this problem is to make one stage of chemical reaction highly effective so the entire process to reach the desired final result will be cut as short as possible.

• In the area of organic chemistry, there are generally three types of chemical reactions as shown in Diagram I:

• Addition reaction – to create a new compound by simply adding a red ball to a blue ball.
• Elimination reaction – to create a compound of a red ball and a blue ball by removing the white ball from a compound of the red, blue and white balls.
• Substitution reaction – just like people holding hands with each other, while the blue and the red hold their hands, the blue lets go of the hand of the white. In this case, two simultaneous reactions are occurring and a compound of the blue and the red is obtained.

• Number 2 and 3 above make the white into a waste and therefore are considered environmentally unfriendly. The first type is the mainstream option today.

• Consider using two kinds of starting materials (black and white) where the bond is difficult to cut, and creating a compound of two white balls each bonded with black ball (see Diagram II). The traditional method requires a long process consisting of multiple steps of chemical reactions. This results in a drastically reduced amount of the final product as explained earlier.

• In order to avoid this bind, Tsukamoto and his colleagues have been working on a new chemical reaction called “sawing” reaction. The idea is to “cut” the chemical link of the starting material with something equivalent to scissors, thereby temporarily producing highly reactive chemical species, and then “saw” them to the other starting material to produce new chemical bonds (see Diagram III). This results in a much shorter process to reach the end result.

• The most obvious chemical elements in nature that affect us are hydrogen and carbon, which are the absolute necessity for organic compounds. By reacting to oxygen, nitrogen and other elements, hydrogen and carbon can take on various chemical and physical characteristics and play a significant role for human use, such as in cold medicine. Because these two are highly stable due to the environmental factors such as temperature and atmospheric pressure, their chemical bond is hard to break.

• Tsukamoto and his colleagues have succeeded in cutting the chemical bond of carbon in the lab using metal catalysts, and created two new chemical compounds. The result of their study was published by Science, an international science journal.

• The “cut and saw” method is hoped to enable the production of new, useful compounds using highly stable materials that are structurally simple and industrially cheap. For example, simple and common materials may be morphed into a new compound that has anti-cancer functions.

• According to Tsukamoto, this new method depends on the catalytic power of metal catalysts. “I’ve been involved in the project concerning metal catalysts, and trying to create molecular compounds and models,” he said.

Tatsuhiro Tsukamoto, PhD student, University of Chicago

Three general types of chemical reactions
(The image is borrowed from Tsukamoto's presentation)