Nucleosides spectral properties

CH3), which was converted with aqueous alkali to 5 -methyl-2 -thiouri-dine.233 Similarly, 3-ethoxyacryloyl isothiocyanate (LXXI, R = H, R" = C2H5) plus LXX yielded the tribenzoate ester of LXXIII (R = H) which was converted with sodium alkoxide or ammonia to 2 -thiouridine. These D-ribo-2 -thionucleosides exhibit ultraviolet spectral properties similar to those shown by l-methyl-2-thiouracil123 and an enzymically prepared sample of 2 -thiouridine.236 Treatment of 2 -thiouridine with monochloroacetic acid afforded uridine this finding permitted assignment of the l-(/ -D-ribo-furanosyl) structure to these 2-thiouracil nucleosides.233... 

Table VII is a comprehensive list of spectral properties of some nucleosides, bases, and other biologically important compounds, normally found in serum or plasma ultrafiltrates or red blood cell lysates.

The absorption of nucleic acids also arises from n n and n- n transitions of purine and pyrimidine bases. The spectra of nucleic acids and derivatives occur around 200-300nm (Table 7.3). The spectra of all four nucleosides are sensitive to pH. Protonation of C and G results in a large red shift. Deprotonation of U and T also results in a large red shift. In a typical nucleic acid, the spectral properties of the isolated chromophores merge into a smooth single band with = 260nm. The average molar extinction coefficient of... 

Purines, Pyrimidines, Nucleosides, and Nucleotides Physical Constants and Spectral Properties (Nucleic Acids, p. 65-215)... 

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