Serum albumin absorption spectra

Figure 2.11. The dependence of the position of the fluorescence spectrum maximum on excitation wavelength for tryptophan in a model medium (glycerol) at different temperatures (a) and singletryptophan proteins (b). 1, Whiting parvalbumin, pH 6.S in the presence of Ca2+ ions 2, ribonuclease Th pH 6.5 3, ribonuclease C2, pH 6.5 4, human serum albumin, pH 7.0, +10"4 M sodium dodecyl sulfate 5, human serum albumin, pH 3.2 6, melittin, pH 7.5, +0.15 M NaCl 7, protease inhibitor IT-AJ from Actinomyces janthinus, pH 2.9 8, human serum albumin, pH 7.0 9, -casein, pH 7.5 10, protease inhibitor IT-AJ, pH 7.0 11, basic myelin protein, pH 7.0 12, melittin in water. The dashed line is the absorption spectrum of tryptophan.

B. Hicks, M. White, C. A. Ghiron, R. R. Kuntz, and W. A. Volker, Flash photolysis ofhuman serum albumin Characterization of the indole triplet absorption spectrum and decay at ambient temperature, Proc. Natl. Acad. Sci. U.S.A. 75, 1172-1175 (1978). 

The absorption spectrum of ANS bound to serum albumin shows a peak at 370 nm, different from 350 nm observed for ANS alone and 385 nm observed in the excitation spectrum. In general, the excitation spectrum is much more accurate than the absorption spectrum because it characterizes the real emitting fluorophores (here ANS bound to BSA). The absorption spectrum characterizes the sum of all absorbing molecules in the different ground states, here free and bound ANS. 

Fig. 13 indicates spectra of various samples of serum albumin treated with 2-mercaptoethanol or ferrous salt, or both. The sample treated with 2-mercaptoethanol alone contains no iron and no labile sulfur, whereas the sample treated with ferrous salt alone contains iron but not labile sulfur. Further, the sample treated with both 2-mercaptoethanol and ferrous salt exhibits a visible absorption and it contains 81.3 mp.-atoms of iron per mg of protein and 82.4 mjxmoles of labile sulfur per mg of protein. The spectrum of methylene blue derived from labile sulfur in the artificial iron protein by Lath s reaction is identical with that derived from a standard solution of Na2S or from native adrenodoxin. 

Reactions of NO were also studied with the synthetic heme protein discussed earlier, namely the recombinant human serum albumin (rHSA) with eight incorporated TPPFe derivatives bearing a covalently linked axial base, were also investigated. The UV-vis absorption spectrum of the phosphate buffer solution at physiological pH showed absorption band maxima at 425 and 546 nm upon the addition of NO to form the nitrosyl species, which was also formed when the six-coordinate CO-adducts were reacted with NO gas. EPR spectroscopy revealed that the albumin-incorporated iron(II) porphyrin formed six-coordinate nitrosyl complexes. It was observed that the proximal imidazole moiety does not dissociate from the central iron when NO binds to the trans position. The NO-binding affinity P1 /2no was 1.7 X 10 torr at pH 7.3 and 298 K, significantly lower than that of the porphyrin complex itself, and was interpreted as arising from the decreased association rate constant (kon(NO), 8.9 x 10 M s" -1.5 x 10 M s ). Since NO-association is diffusion controlled, incorporation of the synthetic heme into the albumin matrix appears to restrict NO access to the central iron(II). ... 

The application of low-temperature techniques to the investigation of protein spectra in the ultraviolet region was initiated by Lavin and Northrop (1935) who investigated the ultraviolet absorption spectra of pepsin, serum albumin, and ovalbumin in glycerol, and showed that the fine structure of the protein spectrum was enhanced at — 100°C. Preliminary reports of similar work have been published by Randall and Brown (1949) on thin films of sublimed tryptophan and phenylalanine at 90°C., and by Sinsheimer et al. (1949) for tryptophan at 77.6°K. Loof-bourow and his coworkers (Sinsheimer et al., 1950) have begun publication of a series of papers reporting much more comprehensive work on the influence of low temperature on the spectra of amino acids and proteins in thin films and in solid solution. Beaven et al. (1950) have reported a few results on thin Aims of the aromatic amino acids. 

Figure 6.3. Absorption spectrum of TNS in phosphate buffer at pH 7 (a ) and fluorescence excitation spectrum of TNS in presence of bovine serum albumin (b) = 460 nm.

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... 

Figure 6 MIR absorption spectra for selected serum constituents. The spectra for urea, glucose, and albumin were acquired for aqueous solutions using an optical path length of 6 pm (the spectrum of water has been subtracted). Those for cholesterol and tripalmitin (tripalmitidoylglycerol) were measured for solutions in carbon tetrachloride using an optical path length of 0.5 mm.

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