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The energy of the exciton is transferred to a chlorophyll molecule (P680, where P stands for pigment and 680 for its absorption maximum at 680 nm) in the reaction center of photosystem II via resonance energy transfer. P680 can also directly absorb a photon at a suitable wavelength.
In biochemistry, the molar absorption coefficient of a protein at 280 nm depends almost exclusively on the number of aromatic residues, particularly tryptophan, and can be predicted from the sequence of amino acids. [6] Similarly, the molar absorption coefficient of nucleic acids at 260 nm can be predicted given the nucleotide sequence.
The infrared spectrum of liquid water is dominated by the intense absorption due to the fundamental O-H stretching vibrations. Because of the high intensity, very short path lengths, usually less than 50 μm, are needed to record the spectra of aqueous solutions.
[1] [2] In physical and analytical chemistry, infrared spectroscopy (IR spectroscopy) is a technique used to identify chemical compounds based on the way infrared radiation is absorbed by the compound. The absorptions in this range do not apply only to bonds in organic molecules.
Chlorophyll a absorbs light within the violet, blue and red wavelengths. Accessory photosynthetic pigments broaden the spectrum of light absorbed, increasing the range of wavelengths that can be used in photosynthesis. [5] The addition of chlorophyll b next to chlorophyll a extends the absorption spectrum.
If a compound dissolves in water, then it is considered to be hydrophilic. [6] Zinc chloride and calcium chloride, as well as potassium hydroxide and sodium hydroxide (and many different salts), are so hygroscopic that they readily dissolve in the water they absorb: this property is called deliquescence.
The color of chemicals is a physical property of chemicals that in most cases comes from the excitation of electrons due to an absorption of energy performed by the chemical. The study of chemical structure by means of energy absorption and release is generally referred to as spectroscopy.
The nature of the central metal can also influence the absorption spectrum of the metal-macrocycle complex or properties such as excited state lifetime. [ 4 ] [ 5 ] [ 6 ] The tetrapyrrole moiety in organic compounds which is not macrocyclic but still has a conjugated pi-bond system still acts as a chromophore.