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Is a Steak in the Mirror World Tasty?
Interesting feature of chemistry in the mirror world
By Kohei Sato

Kohei Sato, Postdoctoral Fellow at Northwestern University, Simpson Querrey Institute for BioNanotechnology, spoke about interesting features of the chemistry in the mirror world during the 13th Japanese Researchers Crossing in Chicago held on April 15.

If you can enter the mirror world and eat a steak, what will its taste look like?

In the mirror world, right and left are opposite, so the mirror image of the steak is opposite. Besides, a molecule of amino acid, which composes the steak, is opposite as well. As diagram I indicates, the original amino acid molecule and the one in the mirror world have the same components and structure, but when you eat it, it is tasteless.

Sato said that amino acid in the mirror world can be made artificially, and you can actually taste it; however, it is not delicious at all.

Why is an amino acid molecule in the mirror world different from the original one?

Let’s simplify the structure of amino acid molecule as diagram II, and turn the molecule in the mirror world clockwise. As you can see in diagram III, the two molecules are the same shape; however, the positions of the red ball and the blue ball are switched. The two cannot be superimposed on one another; therefore, the two are different substances.

Our left hand and right hand have a mirror like relationship. If you try to put your left hand on the top of your right hand, you cannot superimpose them. Thus, the two are not superimposable, so they are different. As we have left hand and right hand, there is a left-handed amino acid and a right-handed amino acid. The former belongs to our world, and the later belongs to the mirror world.

Do we recognize left-handed and right-handed amino acid?

Our body is entirely composed of left-handed amino acid. The reason for this is yet elucidated. “If you find it, you will be a Nobel laureate,” Sato said.

Because we have left-handed character, we can recognize only left-handed amino acid and enjoy the taste of a steak in our world. On the other hand, we don’t recognize right-handed amino acid, so we feel it to be tasteless. If you are a person in the mirror world, you may enjoy the taste of right-handed amino acid.

Left-handed substance and right-handed substance in medicines

Many medicines have a left-handed substance and a right-handed substance. For example, Ibuprofen is consisted of the both substances at the ratio of 50% and 50%. Its left-handed substance brings down fever and kills pain, and the right-handed substance does nothing. Sato said that making only left-hand substance was technically difficult and costly.

What would happen on a right-handed substance when you swallow a pill?

Our body basically tries to digest what we eat, and we have a special protein to change a right-handed substance to left-handed one, then our body digests it. When the right-handed substance is changed to the left, it works as a medicine to reduce fever and pain just before it is digested.

Does right-handed substance cause a side effect?

The sleeping pill Thalidomide was a mixture of a half left and a half right substance. It was sold in Japan in 1958. The right-handed substance worked as a sleep agent, and the left-handed one was said to be a cause of birth defects. The sale of Thalidomide was discontinued four years later.

After a 40 year sales ban, Thalidomide was reapproved as an anticancer drug. Sato said that similar incidents actually happened in the past. A left or right-handed substance worked as a medicine, and another became as a toxin to our body.

To avoid such incidents, serious studies about left and right-handed substances have been done. Even a medicine, which is extracted from a natural plant and has only left-handed substance, becomes mixture of both when it is reproduced artificially. As a change of right to left may occur in our body, toxin check has become mandatory today.

From such a background, technologies to produce one sided substance are tremendously advanced. The technologies that select the good one from mixture are also enormously advanced. Japanese researchers like Nobel laureate Ryoji Noyori and Professor Yoshio Okamoto have made large contribution to this field.

Sato said, “Left and right-handed substances play important roles in our body, so I wanted you to know about them today.”

Sato’s recent study

Sato has been studying if our body is able to recognize a left-handed helix and a right-handed helix.
To regenerate our nerves and bone, our cells have to grow. When our cells grow, they need collagen beneath them. (Sato said taking collagen from the mouth would not work in this case.)

Sato made nano-size collagen ropes. One rope group was left-handed helix, and another was right-handed helix. He put cells on each rope group and observed how they grew. The cells on the left-handed helix grew well; however, another group didn’t grow at all and died. “The experiment revealed that our body was able to recognize a left-handed helix and a right-handed helix,” Sato said.

Kohei Sato, Postdoctoral Fellow at Northwestern University, Simpson
Querrey Institute for BioNanotechnology