问题 多项选择题

生物素-亲和素系统的应用特点有( )

A.灵敏度高

B.特异性强

C.稳定性好

D.适用范围广

答案

参考答案:A,B,C,D

解析:生物素-亲和素系统的应用特点有:①灵敏度高:生物素易与多种生物大分子形成生物素衍生物,且后者具有多价性;亲和素每个分子有四个生物素结合部位,可同时以多价方式结合生物素化的大分子衍生物和标记物。②特异性强:生物素、亲和素间有极高的亲和力,使其结合具有高度的专一性,故在提高灵敏度的同时,不会增加检测方法的非特异性干扰,而前两者的结合不受高度稀释的影响。③稳定性好:生物素、亲和素结合形成的复合物的解离系数很小,反应具有不可逆性。而且多种理化及生物因素不影响其结合。④适用范围广:两者不仅可与各种标记技术相结合,用于各种标记免疫测定方法,而且还可制成生物介质,用于多种昂贵生物材料的分离纯化。此外,容易制成相应商品化试剂。⑤可以减少高价试剂(如抗原特异性抗体)的用量,降低实验成本。

单项选择题
阅读理解

Lucky is the man who has no “skeleton in his closet.” When a man has done something in his life that he is ashamed of, that he wants to hide, he is said to have a “skeleton in his closet.” Some people may have more than one skeleton.

As we have noted many times, it is hard to find out how these expressions begin. Sometimes, we get some hard facts. But more often we have to depend on guesswork. And that is true of this phrase, which came from England.

Before 1832, English law did not permit a doctor to cut open a dead human body for scientific examination, unless it was the corpse(尸体) of an executed(处决) criminal.

But when it became legal, more and more doctors demanded skeletons for a more scientific study of medicine. It was helping in the advance of modern medicine. The demand had become so strong that men began to rob tombs and sell skeletons to doctors at high prices.

We are told that a doctor would usually buy just one skeleton for scientific study. It became very important in his work. But he had to keep it hidden because most people objected to keeping such a thing. As a rule, the doctor keep his skeleton in some dark corner where it could not be seen, or hide it in a closet.

After a time, people began to suspect every doctor of hiding a skeleton in the closet. From this suspicion, the phrase“a skeleton in the closet”took on a broader, more general meaning: to describe anything that a man wanted to keep others from discovering. It could be proof of a criminal act, or something much less serious. Well, that is one theory.

One writer, however, believes that the phrase might have come from something that really happened. It is his guess that a hidden closet in some old English country home may have turned up a real skeleton, clear proof of some old family shame or crime. Well, one man's guess is as good as another. But this sounds like a story by the great French novelist, Balzac.

Balzac tells us of a man who suspected his wife of having a lover. The husband comes home by surprise. But she hears him and quickly hides her lover in the closet of her bedroom. He enters her room and asks her if she is hiding her lover. He says he will not open the door to the closet if she promises him there is no one there; He will believe her. She answers firmly that she is not hiding anyone in the closet.

The husband then begins to build a solid brick wall against the closet. His wife watches, knowing that her lover will never come out alive. But she will not change her story and admit her guilt.

小题1:Which of the following situations is now suitable for using the phrase “skeleton in the closet”?

A.You have stolen something precious and hide them in the closet.

B.You are a doctor and have to keep a skeleton for research.

C.If you have cut open a dead human body for scientific examination you should keep the

skeleton secret.

D.You have done a crime or done something foolish, but you want to keep others from discovering it.

小题2:Which of the following is right according to the text?

A.In the 19th century, doctors realized the importance of anatomy (解剖) in the development of

medicine.

B.The doctors of the ancient times liked to collect as many skeletons as possible

C.The thieves stole skeletons from tombs in order to help the doctors.

D.It is legal that corpses of anybody are cut open for scientific examination in history.小题3:From the story Balzac told we know that the wife's lover must have become ______.

A.a corpse

B.a phrase

C.a skeleton

D.a story