What Is Tryptophan Fluorescence? (with picture)

E.A. Sanker
E.A. Sanker
Tryptophan fluorescence is a phenomenon that occurs when tryptophan is exposed to ultraviolet (UV) light.
Tryptophan fluorescence is a phenomenon that occurs when tryptophan is exposed to ultraviolet (UV) light.

Tryptophan fluorescence, which is seen in proteins containing the amino acid tryptophan, is a phenomenon that occurs when tryptophan is exposed to ultraviolet (UV) light. Electrons in the tryptophan are excited to a higher energy state by UV absorption and then drop again to ground state, emitting fluorescence in the process. Tryptophan is an intrinsically fluorescent component of proteins and has many applications in biochemistry, where it is used as a probe to study protein folding and behavior.

As one of several amino acids, tryptophan is an organic molecule that links in chains with other amino acids to form proteins. It is also one of the 10 essential amino acids in the diet of human beings. Chemically, tryptophan is aromatic, meaning that its molecular structure includes a ring of atoms connected in such a way as to allow electrons to cycle around the ring. The electrons in this ring structure absorb UV light, allowing tryptophan fluorescence to take place.

Electrons in an atom or molecule typically exist in the lowest possible energy state, the ground state. When an electron absorbs energy from a photon, or light particle, the energy from that photon causes the electron to jump to a higher energy state — an excited state. The excited electron returns to ground state by emitting energy, often in the form of light known as fluorescence. Tryptophan fluorescence is an example of this process.

Ultraviolet light, the same type of light found in sunlight, is not visible to the human eye. Its wavelengths are too short for humans to perceive visually, ranging from 10 nanometers (nm) to 400 nm in length. Tryptophan can absorb wavelengths of light up to 280 nm in length and emits slightly longer wavelengths over a spectrum, with most emissions at about 320 to 375 nm in length.

Organic compounds including tryptophan are analyzed in laboratories using a technique known as fluorescence spectroscopy. A beam of UV light is directed at the protein or molecular structure under study, causing its electrons to become excited. The wavelength of fluorescence that the electrons emit as they fall to the ground state is then measured. Fluorescence spectroscopy can be useful in studying the folded structure of proteins.

Tryptophan fluorescence also provides a tool for analyzing biochemical compounds. In medical research, for example, tryptophan fluorescence is sometimes used as a probe to determine how proteins in tissues or blood are behaving or bonding with other molecules. Variations in fluorescence wavelengths can indicate chemical changes in tryptophan's immediate environment.

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Discussion Comments


@bfree - First of all, congratulations on your promotion. One thing to remember is that you're not alone, millions of people suffer from insomnia. The important thing is that you're willing to find help the all natural way from the foods you eat.

High levels of tryptophan can be found in dairy products, red meats, soybeans and other soy products, bananas, turkey, tuna, shellfish, and nuts and seeds.

I'm sure that if you add some of these foods to your daily diet, you'll be sleeping like a baby in no time. You might also want to do some meditation or yoga exercises before bedtime to help relieve your tension.

It does wonders at increasing your levels of serotonin that leaves you feeling very calm and relaxed. That's just a suggestion, but do try adding more tryptophan based foods to your diet. Good luck and sweet dreams.


I've recently been promoted at my work and although I love my new position, I've noticed that due to the higher levels of stress and anxiety, I've been unable to get a good nights sleep.

I've been reading a lot lately on the necessities of both essential and non-essential amino acids in our diets.

If eating enough foods high in tryptophan is indeed a remedy for insomnia then please tell me what foods they are.

I've never had a problem sleeping before my promotion and because of it I have poor concentration at work. I just want to crawl under my desk and take a nap. Please help.


@whitesand - There are three main factors for eating foods high in tryptophan. It helps to regulate your appetite, elevate your mood and helps you get a better nights sleep.

Some of the conditions that can indicate a need to increase high tryptophan foods in your diet are mood swings like depression, anxiety and irritability. Other indications could be insomnia, impatience, lack of concentration, and impulsiveness.

There could also be a need to increase tryptophan in your diet if you have unexplained weight gain or weight loss or overeating and cravings of carbohydrates.


What are the benefits of eating foods high in tryptophan and what are some of the conditions that indicate a need to increase your intake of high tryptophan foods?

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    • Tryptophan fluorescence is a phenomenon that occurs when tryptophan is exposed to ultraviolet (UV) light.
      Tryptophan fluorescence is a phenomenon that occurs when tryptophan is exposed to ultraviolet (UV) light.