He Xiaohua, Lu Sixin, Cheng Luisa W, Rasooly Reuven, Carter John Mark
Western Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Albany, California 94710, USA.
J Food Prot. 2008 Oct;71(10):2053-8. doi: 10.4315/0362-028x-71.10.2053.
A cell-free translation assay was applied for the quick detection of ricin in food samples. Three economically important foods-ground beef, low-fat milk, and liquid chicken egg--were tested. The results indicated that ground beef had very little matrix effect on the assay, whereas low-fat milk and liquid chicken egg showed clear interference on the protein translation. A simple dilution in phosphate-buffered saline (PBS) effectively eliminated the translational inhibition from these foods. The concentrations inhibiting 50% of luciferase translation derived from the current study were 0.01 nM for the pure ricin A chain, 0.02 nM for pure ricin, and 0.087 nM for crude ricin in PBS. In most cases, the half inhibitory concentration values for ricin in food matrices were significantly lower than for those in PBS buffer, suggesting that some components in these food matrices might potentiate the activity of ricin. Thermal stability tests indicated that the ricin A chain was the least stable among the three forms of ricin in all matrices measured. The thermal stability of pure and crude ricins varied depending on the matrices. The specific activities of ricin in PBS buffer were confirmed by a neutralization test with ricin-specific and nonspecific antibodies. This study demonstrates that the cell-free translation assay is a rapid and sensitive method for detection of biologically active ricin toxin in ground beef, low-fat milk, and liquid chicken egg and that food matrices can greatly affect the thermal stability of ricin.
采用无细胞翻译检测法快速检测食品样本中的蓖麻毒素。对三种具有重要经济价值的食品——碎牛肉、低脂牛奶和液态鸡蛋进行了检测。结果表明，碎牛肉对该检测的基质效应很小，而低脂牛奶和液态鸡蛋对蛋白质翻译有明显干扰。在磷酸盐缓冲盐水（PBS）中进行简单稀释可有效消除这些食品的翻译抑制作用。本研究得出的抑制50%荧光素酶翻译的浓度分别为：PBS中纯蓖麻毒素A链为0.01 nM，纯蓖麻毒素为0.02 nM，粗制蓖麻毒素为0.087 nM。在大多数情况下，食品基质中蓖麻毒素的半数抑制浓度值显著低于PBS缓冲液中的值，这表明这些食品基质中的某些成分可能会增强蓖麻毒素的活性。热稳定性测试表明，在所测的所有基质中，三种形式的蓖麻毒素中蓖麻毒素A链最不稳定。纯蓖麻毒素和粗制蓖麻毒素的热稳定性因基质而异。通过用蓖麻毒素特异性和非特异性抗体进行中和试验，证实了PBS缓冲液中蓖麻毒素的比活性。本研究表明，无细胞翻译检测法是一种快速、灵敏的检测碎牛肉、低脂牛奶和液态鸡蛋中生物活性蓖麻毒素的方法，并且食品基质会极大地影响蓖麻毒素的热稳定性。
