Tyrosine light absorption

Comparison of the light absorption spectra of the aromatic amino acids tryptophan and tyrosine at pH 6.0. The amino acids are present in equimolar amounts (10 3 m) under identical conditions. The measured absorbance of tryptophan is as much as four times that of tyrosine. Note that the maximum light absorption for both tryptophan and tyrosine occurs near a wavelength of 280 nm. Light absorption by the third aromatic amino acid, phenylalanine (not shown), generally contributes little to the spectroscopic properties of proteins. 

Fig. 8. Products of iV-acetyl-L-tyrosine treatment with NaOCl studied by HPLC method. Peak denoted 4 represents A -acetyltyrosine, peak denoted 6 is iV-acetyl 3-chlorotyrosine. Minute peak denoted 8 represents 3,5-dichlorotyrosine. Graph respresents column eluate light absorption at 280 nm plotted versus column retention time. (From Drabik and Naskalski, unpublished results.)...

Purple acid phosphatases. Diiron-tyrosinate proteins with acid phosphatase activity occur in mammals, plants, and bacteria. Most are basic glycoproteins with an intense 510- to 550-nm light absorption band. Well-studied members come from beef spleen, from the uterine fluid of pregnant sows (uteroferrin), and from human macrophages and osteoclasts. " " One of the two iron atoms is usually in the Fe(III) oxidation state, but the second can be reduced to Fe(II) by mild reductants such as ascorbate. This half-reduced form is enzymatically active and has a pink color and a characteristic EPR signal. Treatment with oxidants such as H2O2 or hexacyannoferrate (III)... 

Spectra of proteins and nucleic acids. Most proteins have a strong light absorption band at 280 nm (35,700 cm ) which arises from the aromatic amino acids tryptophan, tyrosine, and phenylalanine (Fig. 3-14). The spectrum of phenylalanine resembles that of toluene (Fig. 23-7)whose 0-0 band comes at 37.32 x 10 cm. The vibrational structure of phenylalanine can be seen readily in the spectra of many proteins (e.g., see Fig. 23-llA). The spectrum of tyrosine is also similar (Fig. 3-13), but the 0-0 peak is shifted to a lower energy of 35,500 cm (in water). Progressions with spacings of 1200 and 800 cm are prominent. The low-energy band of tryptophan consists of two overlapping transitions and The Lb transition has well-resolved vibrational subbands, whereas those of the La transition are more diffuse. Tryptophan derivatives in hydrocarbon solvents show 0-0 bands for both of these transitions at approximately... 

Reactions of ozone with proteins can be observed in vitro as well as in vivo [14, 16]. The primary reaction of ozone with egg albumin is similar to its denaturation. Changes of the UV-light absorption, particularly in the tyrosine spectrum, and a reduced solubility occur. These structural changes are sufficient to induce the production of antibodies when the ozonized proteins are injected into rabbits. The exposure of rabbits to an environment containing 10 ppm ozone for one hour weekly for six weeks induced the formation of antibodies in the blood serum in detectable... 

Subunit B1 of . coli ribonucleotide reductase is an SH protein carrying several binding sites of different affinity for substrate and effector nucleotides these interactions will be discussed in a later paragraph. The most unusual features of the smaller subunit B 2 are its iron content and a tyrosine residue present as stable free radical. Both these components are essential for enzyme catalysis and structurally coupled. They confer characteristic light absorption to the protein, with a broad maximum around 370 nm (a =... 

A number of investigators have studied the effect of ozone on the ultraviolet absorption spectra of proteins and amino acids. A decrease in the absorption of 280-nm light in a number of proteins was originally reported ly Giese et aV to be a consequence of ozone exposure they suggested that this was due to an interaction of ozone with the ring structures of tyrosine and tryptophan. Exposure of a solution of tryptophan to ozone resulted in a decrease in 280-nm absorption, whereas the extinction coefficient of tyrosine increased. Similar results with tyrosine were reported by Scheel et who also noted alterations in the ultraviolet spectra of egg albumen, perhaps representing denaturation by ozone. 

Side chains of the three aromatic amino acids phenylalanine, tyrosine, and tryptophan absorb ultraviolet light in the 240- to 300-nm region, while histidine and cystine absorb to a lesser extent. Figure 3-13 shows the absorption spectrum of a "reference compound" for tyrosine. There are three major absorption bands, the first one at 275 nm being a contributor to the well-... 

Determination of protein concentration by measuri ng absorbance at 280 nm (A2g0) is based on the absorbance of UV light by the aromatic amino acids tryptophan and tyrosine, and by cystine, disulfide bonded cysteine residues, in protein solutions. The measured absorbance of a protein sample solution is used to calculate the concentration either from its published absorptivity at 280 nm (a280) or by comparison with a calibration curve prepared from measurements with standard protein solutions. This assay can be used to quantitate solutions with protein concentrations of 20 to 3000 pg/ml. 

Tyrosine is one of the important a-amino acids and is oxidatively polymerized with tyrosinase to melanin, the black pigment in animals [25-30], Melanin plays a role in the prevention of damage to the organism that occurs through the absorption of ultraviolet light. Melanin is the only major paramagnetic organic com-... 

Absorption spectrum is the plot of light intensity as a function of wavelength. Figure 1.2 shows the absorption spectra of tryptophan, tyrosine, and phenylalanine in water. A strong band at 210-220 nm and a weaker band at 260-280 nm can be seen. 

The part of a molecule that absorbs the light and is, therefore, responsible for its colour (whether in the visible or UV region) is called the chromophore, and the wavelength dependence of the absorption defines its absorption spectrum. Figure 7-3 illustrates the absorption spectrum of the three aromatic amino acids tryptophan, tyrosine and phenylalanine. 

The absorption of ultraviolet light by proteins at wavelength 280 nm is caused mostly by the amino acids tyrosine and tryptophan along the protein molecular chains. The molecular absorption coefficients for these two amino acids are ... 

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