モル吸光係数

WordNet

no longer in existence; "the extinction of a species" (同)defunctness
no longer active; extinguished; "the extinction of the volcano"
the reduction of the intensity of radiation as a consequence of absorption and radiation
the act of extinguishing; causing to stop burning; "the extinction of the lights" (同)extinguishing, quenching
a conditioning process in which the reinforcer is removed and a conditioned response becomes independent of the conditioned stimulus (同)experimental extinction
complete annihilation; "they think a meteor cause the extinction of the dinosaurs" (同)extermination
pertaining to large units of behavior; "such molar problems of personality as the ego functions"--R.R. Hunt
grinding tooth with a broad crown; located behind the premolars (同)grinder
containing one mole of a substance; "molar weight"
designating a solution containing one mole of solute per liter of solution
of or pertaining to the grinding teeth in the back of a mammals mouth; "molar teeth"
a constant number that serves as a measure of some property or characteristic

PrepTutorEJDIC

消滅(絶滅)すること,(火などが)消えること;(…を)消滅(絶滅)させること,(火などが)消すこと《+『of』+『名』》
臼歯(きゅうし)
(数学で)係数,(物理で)係数,率

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/08/27 03:44:32」(JST)

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The molar attenuation coefficient is a measurement of how strongly a chemical species attenuates light at a given wavelength. It is an intrinsic property of the species. The SI unit of molar attenuation coefficient is the square metre per mole (m²/mol), but in practice, it is usually taken as the M⁻¹⋅cm⁻¹ or the L⋅mol⁻¹⋅cm⁻¹. In older literature, the cm²/mol is sometimes used with corresponding values 1,000 times larger. In practice these units are the same, with the difference being expression of volume in either cm³ or in L. The molar attenuation coefficient is also known as the molar extinction coefficient and molar absorptivity, but the use of these alternative terms has been discouraged by the IUPAC.^[1]^[2]

The absorbance of a material that has only one attenuating species also depends on the pathlength and the concentration of the species, according to the Beer–Lambert law

where

ε is the molar attenuation coefficient of that material;
c is the amount concentration of those species;
ℓ is the pathlength.

Different disciplines have different conventions as to whether absorbance is decadic (10-based) or Napierian (e-based), i.e., defined with respect to the transmission via common logarithm (log₁₀) or a natural logarithm (ln). The molar attenuation coefficient is usually decadic.^[3] When ambiguity exists, it is best to indicate which one applies.

When there are N attenuation species in a solution, the overall absorbance is the sum of the absorbances for each individual species i:

The composition of a mixture of N attenuating species can be found by measuring the absorbance at N wavelengths (the values of the molar coefficient of attenuation for each species at these wavelengths must also be known). The wavelengths chosen are usually the wavelengths of maximum absorption (absorbance maxima) for the individual species. None of the wavelengths must be an isosbestic point for a pair of species. The set of the following simultaneous equations can be solved to find the concentrations of each attenuating species:

\begin{cases} A(\lambda_1) = \ell\sum_{i=1}^N \varepsilon_i(\lambda_1) c_i,\\ \ldots\\ A(\lambda_N) = \ell\sum_{i=1}^N \varepsilon_i(\lambda_N) c_i.\\ \end{cases}

The molar attenuation coefficient (in units of cm²) is directly related to the attenuation cross section via the Avogadro constant N_A:^[4]

The mass attenuation coefficient is equal to the molar attenuation coefficient times the molar mass.

In biochemistry, the molar attenuation 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.^[5]

If the molar attenuation coefficient is known, it can be used to determine the concentration of a protein in solution.

References

^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "Extinction".
^ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "Absorptivity".
^ [1][2][3]
^ Lakowicz, J. R. (2006). Principles of Fluorescence Spectroscopy (3rd ed.). New York: Springer. p. 59. ISBN 9780387312781.
^ Gill, S. C.; von Hippel, P. H. (1989). "Calculation of protein extinction coefficients from amino acid sequence data". Analytical Biochemistry 182 (2): 319–326. PMID 2610349.

External links

Nikon MicroscopyU: Introduction to Fluorescent Proteins includes a table of molar attenuation coefficient of fluorescent proteins.

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