Detection of free radical transfer in lipoxygenase I-B-catalyzed linoleic acid-soybean protein interaction by electron spin resonance spectroscopy (ESR).
Effects of lipoxygenase I-B (LOX)-catalyzed oxidation of linoleic acid on soybean proteins was evaluated by electron spin resonance (ESR) and fluorescence spectroscopy in different model systems in the presence or absence of antioxidants. A strong central singlet signal was detected by ESR spectroscopy and identified as the carbon radical (g value range 2.0041-2.0054). A downfield shoulder attributed to the sulfur radical (g value 2.019-2.028) was also observed. The changes in soybean proteins were accompanied by an increase in fluorescence, indicating the formation of cross-links. Natural antioxidants such as ascorbic acid and alpha-tocopherol as well as synthetic antioxidants butyl hydroxytoluene (BHT) inhibited the development of both the free radical signal and the fluorescence when added to soybean proteins prior to incubation with linoleic acid and lipoxygenase I-B; the central singlet signal attributed to the carbon radical was reduced by 35-65%. This paper clearly indicates direct free radical transfer from oxidizing linoleic acid catalyzed by LOX to soybean proteins.
Huang
Youru
Y
Department of Biological Science and Food Engineering, Changshu Institute of Technology, Changshu 215500, Jiangsu Province, People's Republic of China.
Yu
Da
D
Hua
Yufei
Y
Qiu
Aiyong
A
D004578:Electron Spin Resonance Spectroscopy; D006801:Humans; D019787:Linoleic Acid / Q000737:chemistry*; D030262:Soybean Proteins / Q000737:chemistry*
D030262:Soybean Proteins; D019787:Linoleic Acid