Characteristics specific extinction coefficient

Visual pigments display characteristic absorption spectra which result from the very specific interactions between protein and chromophore in the binding site, i.e., the absorbance spectrum of retinal at ca. 380 nm is red-shifted to ca. 500 nm in bovine rhodopsin. However, depending on species, rhodopsins absorb from 440 to ca. 600 nm. Porphyropsins show a similar spread in their absorption maxima, absorb at longer wavelengths than the corresponding rhodopsins, and have lower extinction coefficients (ca. 75%) than rhodopsins (e.g., bovine rhodopsin e, ca. 40500) [17] as shown in Fig. 2. 

This esterified hemin is soluble in ligating solvents such as pyridine and also halogenated hydrocarbons, ethers such as tetrahydrofuran, and benzene. It is slightly soluble in alcohols and insoluble in water. In the presence of traces of water in a solution it will slowly convert to the n-oxo form. It can also dehydrate to the proto forms i under specific conditions. Other chemical, physical, and biological properties are similar to those for the protoporphyrin IX com-plex.i Extinction coefficients for the various characteristic spectra of this material are not well defined, as the solutions are generally unstable with time, going to mixtures of the various ligated and jx-oxo forms. 

For a given compound, the area under a chromatographic peak is directly proportional to the amount of compound. By using standards of known concentration, it is possible to calibrate a chromatographic system and to use it to establish the amount of a known compound in a sample. Of course, in the isolation of an unknown compound, no standard is available, and as each compound has a characteristic extinction coefficient (absorptivity), the degree of UV absorbance is specific to individual compounds. It is possible to quantify material corresponding to a particular peak only in relative terms. 

NO (reactant) and CO (product) molecules were used as IR probes of the copper oxidation state in H-Cu-ZSM-5 catalysts. CO adsorption is specific to Cu sites. Its characteristic band at 2158 cm provides quantitative results on integrating its molar extinction-coefficient (e) NO decomposes oxidizing Cu to Cu. Propane and oxygen in a special IR reactor cell always yielded chemisorbed CO. Use of e indicates the NO influence on Cu state. 

Upon exposure to thermal energy, absorption of light, or involvement in specific chemical reactions, interconversion of lycopene isomers is known to take place. The cis isomers of lycopene, formed by rotation around any of its conjugated double bonds, have chemical and physical characteristics distinctly different from their all-frans counterparts. Some of the differences resulting from trans-to-cis isomerization include lower melting point, decreased color intensity, a shift in the lambda max, smaller extinction coefficients, and the appearance of a new maximum in the ultraviolet spectrum. ... 

A = absorbance, expressed as Iq/I Iq = the intensity of the incident light I = the intensity of the light transmitted through the sample 8 = molar absorbtivity, or the extinction coefficient (a constant characteristic of the specific molecule being observed) values for conjugated dienes typically range from 10,000 to 25,000 c = concentration (mol/L)... 

The electron absorption spectrum of the chlorophylls and their derivatives is very characteristic and is attributed to the system of conjugated double bonds making up the basic porphyrin structure. Electron transitions in the chlorophyll molecules, detected by photosensitive optical equipment, produce absorption bands [8,64,65], The intensity of a particular absorption band is normally expressed by its molar specific coefficient of extinction s), which, according to the Beer-Lambert law, depends on the optic density (A), the molar concentration (C), and the optical pathway of the light beam through the solution, expressed in centimeters (L). 

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