chromophore

Examples of chromophore in the following topics:

• UV-Visible Absorption Spectra

  • Such light absorbing groups are referred to as chromophores.
  • A list of some simple chromophores and their light absorption characteristics is provided below.
  • The presence of chromophores in a molecule is best documented by UV-Visible spectroscopy, but the failure of most instruments to provide absorption data for wavelengths below 200 nm makes the detection of isolated chromophores problematic.
  • Molar absorptivities may be very large for strongly absorbing chromophores (>10,000) and very small if absorption is weak (10 to 100).
  • The magnitude ofε reflects both the size of the chromophore and the probability that light of a given wavelength will be absorbed when it strikes the chromophore.

• The Importance of Conjugation

  • A comparison of the absorption spectrum of 1-pentene, λmax = 178 nm, with that of isoprene (above) clearly demonstrates the importance of chromophore conjugation.
  • The appearance of several absorption peaks or shoulders for a given chromophore is common for highly conjugated systems, and is often solvent dependent.
  • To understand why conjugation should cause bathochromic shifts in the absorption maxima of chromophores, we need to look at the relative energy levels of the pi-orbitals.
  • Many other kinds of conjugated pi-electron systems act as chromophores and absorb light in the 200 to 800 nm region.
  • This "substituent effect" is general for dienes and trienes, and is even more pronounced for enone chromophores.

• Plant Responses to Light

  • The response of plants to light is mediated by different photoreceptors: a protein covalently-bonded to a light-absorbing pigment called a chromophore; together, called a chromoprotein.
  • The chromophore of the photoreceptor absorbs light of specific wavelengths, causing structural changes in the photoreceptor protein.

• Blue Light Response

  • Like all plant photoreceptors, phototropins consist of a protein portion and a light-absorbing portion, called the chromophore, which senses blue wavelengths of light.
  • Phototropins belong to a class of proteins called flavoproteins because the chromophore is a covalently-bound molecule of flavin.
  • Their chromophores also contain a flavin-based chromophore.

• Sun Damage, Sunscreen, and Sunblock

  • Sunscreens contain one or more of the following ingredients: organic chemical compounds that absorb ultraviolet light; inorganic particulates that reflect, scatter, and absorb UV light (such as titanium dioxide, zinc oxide, or a combination of both); organic particulates that mostly absorb light-like organic chemical compounds but contain multiple chromophores, may reflect and scatter a fraction of light like inorganic particulates, and behave differently in formulations than organic chemical compounds.

• The Phytochrome System and Red Light Response

  • The phytochromes are a family of chromoproteins with a linear tetrapyrrole chromophore, similar to the ringed tetrapyrrole light-absorbing head group of chlorophyll.
  • Absorption of red or far-red light causes a massive change to the shape of the chromophore, altering the conformation and activity of the phytochrome protein to which it is bound.

• Carotenoids and Phycobilins

  • Phycobilins (from Greek: φ (phykos) meaning "alga", and from Latin: bilis meaning "bile") are chromophores (light-capturing molecules) found in cyanobacteria and in the chloroplasts of red algae, glaucophytes and some cryptomonads (though not in green algae and higher plants).

• Mechanistic Background

  • In careful studies of specific chromophores, sources of monochromatic light may be desired.
  • In this section we shall focus chiefly on the nature and behavior of the electronic excited states formed when a photon is absorbed by a chromophoric functional group.

• Conjugated π-Orbital Functions

  • This would be especially important when the chromophore is encapsulated in a protein or bilayer membrane.