Yet nobody knew for sure. The structure of that LF synthase was unknown. Biochemists study the molecules at work in living things. Golczak and a team of researchers wanted to know how the eye-irritating LF forms. To do that, they turned LF synthase into a crystal.
Now they could use a technique called X-ray crystallography to map its structure. First, the researchers mixed the enzyme with an acid. This caused crystals to grow in the mixture. The researchers froze the crystals in liquid nitrogen. Then they used a special camera to shoot X-ray beams at the crystals. When those beams hit the crystal, the X-rays scattered. By measuring the angles of the scattered beams, the researchers could construct a 3-dimensional picture of the enzyme.
The gas triggers pain receptors in the eyes and nose designed to protect you from chemicals, smoke and other dangers. The tear glands lacrimal glands in the eyes then make tears to wash away the irritant. Tears help to lubricate your eyes and protect them from dust and other irritants, says Dr. Darryl Glover, an optometrist, author and speaker. Reflexive tears — These tears irrigate the eyes and flush away irritants. A healthy tear film — plenty of basal tears — helps prevent your eyes from becoming irritated in the first place, while reflexive tears help to wash away irritants and protect the eyes, Dr.
Glover says. If you cut an onion and start to cry, wash your hands thoroughly and blot your eyes with a clean paper towel, Dr. Glover recommends. Finally, put a few drops of preservative-free artificial tears in your eyes. Some contact lens wearers swear their lenses provide a shield against eye-irritating onion fumes. I wear contact lenses and also own a spare pair of glasses, so I decided to put this question to the test.
Before starting my experiment, I asked Dr. Glover if he thought contacts could either protect my eyes during onion cutting or worsen the irritation. As Dr. Glover explains it: On one hand, a contact lens covers the cornea, which contains nerves and pain receptors that react to the gas released when cutting onions.
On the other hand, contact lenses can disrupt the tear film and may lead to dry eyes , which affects basal tear production. This is one way that plants defend themselves — producing substances that repel creatures who might eat them. Other plants have thorns or stinging leaves, or are made of special cells that make them hard to chew.
One sulfur compound in onions, called propyl sulfoxide, escapes into the air when you slice an onion. When it comes into contact with moisture, such as water vapor in the air or the natural moisture around your eyes, it changes into sulfuric acid. Sulfuric acid has a strong smell and irritates your eyes, so they make tears to wash it away.
But just like onions, your eyes are also equipped with a defense mechanism meant to protect them from harm. When the nerves in each eye detect a lachrymatory agent, they generate tears to flush it out. Some people are more likely to cry when cutting onions than others. The onions that generate the harshest chemical reaction have lots of sulfur-containing compounds. These include yellow, red, and white onions.
Sweeter types, such as green onions , have less sulfur, are less pungent, and produce fewer tears in most people. Through genetic transformation, crop scientists have also created tear-free onion varieties. While not yet mass-produced, you can find tear-free onions called Sunions in some specialty markets.
Here are some tips to reduce crying from onion irritation:. First, keep in mind that the length of time you store onions affects their potency and tear-producing abilities. Fresher onions are less likely to cause crying than those that have been stored for an extended period of time. However you slice them, try to avoid cutting your onion near the root end.
This is the part that contains the highest concentration of sulfuric compounds that can make you cry. Using a sharp knife may also help. The sharper the knife, the less damage is done to the onion, and fewer irritations are released into the air as a result. To reduce or eliminate onion tears, you may have the best luck if you diminish the sulfuric acid compounds in the onion itself.
To do this, try chilling your onion in a bowl of ice water for 30 minutes before cutting. Some people also prefer to cut their onions while submerged in cold water.
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