问题 单项选择题 A1型题

在体外放射分析中,应用PEG等物质进行化学分离或沉淀分离,该分离法的缺点是()。

A.分离需要时间长

B.分离的试剂成本高

C.试剂的通用性不强

D.分离时要求条件高

E.特异性和分离效果较差

答案

参考答案:E

解析:化学分离法又称沉淀分离法,常用的有PEG、三氯醋酸等。它可使蛋白质乳胶脱水,并综合其电荷,从而使蛋白质失去乳胶性质而沉淀下来,通过离心达到分离。此法经济、快速、通用性强,缺点是特异性和分离效果差。

阅读理解

根据短文内容,回答下列问题。

This is my story. I’m French. I fly planes in Africa.

One day, when I was flying a very small plane, there was something wrong with the engine(发动机).The engine stopped. The plane was light and I could land it safely on the ground.

Where was I? I couldn’t see any houses or farms. I had a bottle of water and two oranges. I had a map, too. The first day, I didn’t eat anything. In the evening, I began walking. When the sun went down, the air got cold. Where should I walk? I looked at my map and the moon and the stars. I walked and walked.

The sun came up on the morning of the second day. It was too hot to walk. In the evening, I began walk. I ate an orange and drank a little water.

The third day, I ate the second orange. The bottle of water was now empty. There were no houses, no trees, and no water.

The hot sun came up on the fourth day. Would this be the last day on the earth? I didn’t know. What was that? A bird? A man on a hill? No! Yes, it was! I walked to him excitedly and said hello to him. He looked at me and then gave me some water. I drank and drank...

小题1:Where does the writer come from?     

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小题2:What happened to the writer one day?          

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小题3:What did the writer take with him?      

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小题4:How was the weather in the daytime?    

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小题5:When did the writer see a man on a hill?       

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