摘要：

The purified integral membrane protein, band 3, from human erythrocytes was inserted into egg lecithin liposomes. The insertion of band 3 was determined from thermal transition data from the analysis of the C-H stretching region bands recorded at temperatures from 25 to 22°C. Raman spectra show that band 3 considerably broadens and lowers the thermal transition of egg lecithin liposomes, suggesting the insertion of band 3. The band 3-inserted liposomes were irradiated with gamma-rays (40 Gy) and the radiation target groups were determined by the analysis of the structural sensitive Raman bands in the 16001700 cm1 (amide I), 12001300 cm1 (amide III) and 5501030 cm1 (side chain amino groups) regions. The radiation-sensitive groups as identified from Raman spectra in the region 5501030 cm1 are tyrosines and cysteines. The radiation-induced changes in the secondary structure were determined from amide I and III bands. Quantitative estimation using the curve fitting method shows that band 3 contains 44% total helix, 48% beta strand and 8% undefined plus turns (error ±4%). The secondary structure changes to 35% total helix, 42% total beta-strand and 23% turned and undefined upon irradiating band 3 containing liposomes. We suggest that ionizing radiation preferably damages tyrosine and cysteine side chain residues and reduces the amount of alpha-helical configuration of band 3.

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