Chromophore

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Chromophore

A chromophore is part (or moiety

Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
) of a molecule

Molecule

In chemistry, a molecule is defined as a sufficiently stable, electric charge neutral group of at least two atoms in a definite arrangement held together by very strong chemical bonds....
responsible for its color

Color

Color or colour is the visual perception property corresponding in humans to the categories called red, yellow, blue and others....
.

When a molecule absorbs certain wavelengths of visible light

Visible spectrum

The visible spectrum is the portion of the electromagnetic spectrum that is visual perception to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light....
and transmits or reflects others, the molecule has a color. A chromophore is a region in a molecule where the energy difference between two different molecular orbitals falls within the range of the visible spectrum.

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Encyclopedia

A chromophore is part (or moiety

Functional group

In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules....
) of a molecule

Molecule

Color

Visible spectrum

Electron

The electron is a subatomic particle that carries a negative electric charge. It has elementary particle and is believed to be a point particle....
from its ground state into an excited state

Excited state

Excitation is an elevation in energy level above an arbitrary baseline energy state. In physics there is a specific technical definition for energy level which is often associated with an atom being excited to an excited state....
.

In biological molecules that serve to capture or detect light energy, the chromophore is the moiety

Moiety

Moiety may mean:*A part or half of a molecule *In anthropology, a type of descent group*An Australian Aboriginal kinship*Native Hawaiian realm ruled by a Mo'i or Ali'i...
that causes a conformational change

Conformational change

A macromolecule is usually flexible and dynamic. It can change its shape in response to changes in its environment or other factors; each possible shape is called a conformation, and a transition between them is called a conformational change....
of the molecule when hit by light.

Chromophores almost always arise in one of two forms: conjugated pi systems

Conjugated system

A conjugated system occurs in an organic compound where atoms covalently Chemical bond with alternating single and multiple bonds and influence each other to produce a region called electron delocalization....
and metal complexes

Complex (chemistry)

In chemistry, a complex, also called a "coordination compound" or "metal complex", is a structure consisting of a central atom or molecule connected to surrounding atoms or molecules....
.

In the former, the energy levels that the electrons jump between are extended pi orbitals

Pi bond

In chemistry, pi bonds are covalent bond chemical bonds where two lobes of one involved electron atomic orbital overlap two lobes of the other involved electron orbital....
created by a series of alternating single and double bonds

Chemical bond

A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds....
, often in aromatic systems. Common examples include retinal

Retinal

Retinal, also called retinaldehyde or vitamin A aldehyde, is one of the three forms of vitamin A. Retinal is a polyene chromophore, and bound to proteins called opsins, is the chemical basis of animal vision....
(used in the eye to detect light), various food coloring

Food coloring

A food coloring is any substance that is added to food or drink to change its color. Food coloring is used both in commercial food production and in domestic cooking....
s, fabric dyes (azo compound

Azo compound

Azo compounds are chemical compound bearing the functional group R-N=N-R', in which R and R' can be either aryl or alkyl. The N=N group is called an azo group, although the parent compound, HNNH, is called diimide....
s), lycopene

Lycopene

Lycopene is a bright red carotenoid pigment and phytochemical found in tomatoes and other red fruits.In plants, algae, and other Photosynthesis, lycopene is an important intermediate in the biosynthesis of many carotenoids, including beta carotene, responsible for yellow, orange or red pigmentation, photosynthesis, and photo-protection....
, ß-carotene

Carotene

The term carotene is used for several related substances having the formula C40Hx, which are synthesized by plants but cannot be made by animals....
, and anthocyanins.

The metal complex chromophores arise from the splitting of d-orbitals by binding of a transition metal

Transition metal

In chemistry, the term transition metal has two possible meanings:*It commonly refers to any element in the d-block of the periodic table, including the group 12 element elements zinc, cadmium and Mercury ....
to ligands. Examples of such chromophores can be seen in chlorophyll

Chlorophyll

Chlorophyll is a green pigment found in most plants, algae, and cyanobacteria. Its name is derived from Greek language: ?????? and f????? ....
(used by plants for photosynthesis

Photosynthesis

File:Seawifs global biosphere.jpgPhotosynthesis is a metabolic pathway that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight....
), hemoglobin

Hemoglobin

Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of vertebrates, and the tissues of some invertebrates....
, hemocyanin

Hemocyanin

Hemocyanins are respiratory proteins in the form of metalloproteins containing two copper atoms that reversibly bind a single oxygen molecule ....
, and colorful minerals such as malachite

Malachite

Malachite is a Carbonate minerals normally known as "copper carbonate" with the chemical formula coppercarbonate.copperhydroxide2. This green-colored mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmite masses....
and amethyst

Amethyst

Amethyst is a violet variety of quartz often used as an ornamental stone in jewelry. The name comes from the Ancient Greek a- and methustos , a reference to the belief that the stone protected its owner from drunkenness; the Ancient Greece and Ancient Rome wore amethyst and made drinking vessels of it in the belief that it would prev...
.

A common motif in biochemistry is chromophores consisting of four pyrrole

Pyrrole

Pyrrole, or pyrrol, is a heterocyclic aromatic organic compound, a five-membered ring with the chemical formula carbon4hydrogen4nitrogenH....
rings. These come in two types:

the pyrroles form an open chain, no metal: phytochrome
Phytochrome

Phytochrome is a photoreceptor protein, a pigment that plants use to detect light. It is sensitive to light in the red and far-red region of the visible spectrum....
, phycobilin
Phycobilin

Phycobilins are chromophores found in cyanobacteria and in the chloroplasts of red algae, glaucophytes and some cryptomonads . They are unique among the photosynthetic pigments in that they are bonded to certain water-soluble proteins, known as phycobiliproteins....
, bilirubin
Bilirubin

Bilirubin is the yellow breakdown product of normal heme catabolism. Heme is formed from hemoglobin, a principal component of red blood cells. Bilirubin is excreted in bile, and its levels are elevated in certain diseases....
the pyrroles form a ring (porphyrin
Porphyrin

Porphyrins are a group of chemical compounds of which many occur in nature, such as in green leaves and red blood cells, and in bio-inspired synthetic catalysts and devices....
), with a metal in the center: heme
Heme

A heme or haem is a prosthetic group that consists of an iron atom contained in the center of a large heterocyclic organic ring called a porphyrin....
, chlorophyll
Chlorophyll

Chlorophyll is a green pigment found in most plants, algae, and cyanobacteria. Its name is derived from Greek language: ?????? and f????? ....

External links

: physical mechanisms by which color is generated.
- Azonano.com

Chromophore

See also

External links