锐利的意思Virus, infectious particles consisting of nucleic acid packaged in a protein coat (the capsid), are difficult to resist. Unable to reproduce outside a living cell, virus reproduce only by subverting the genetic mechanisms of a host cell. In one kind of viral life cycle, the virus first binds to the cell’s surface, then penetrates the cell and sheds its capsid. The expod viral nucleic acid produces new virus from the contents of the cell. Finally, the cell releas the viral progeny, and a new cell cycle of infection begins. The human body responds to a viral infection by producing antibodies: complex, highly specific proteins that lectively bind to foreign molecules such as virus. An antibody can either interfere with a virus’s ability to bind to a cell, or can prevent it from releasing its nucleic acid. Unfortunately, the common cold, produced most often by rhinovirus, is intractable to antiviral defen. Humans have difficulty resisting colds becau rhinovirus are so diver, including at least 100 strains. The strains differ most in the molecular structure of the proteins in their capsids. Since dia-fighting antibodies bind to the capsid, an antibody developed to protect against one rhinovirus strain is uless against other strains. Different antibodies must be produced for each strain. A defen against rhinovirus might nonetheless succeed by exploiting hidden similarities among the rhinovirus strains. For example, most rhinovirus strains bind to the same kind of molecule (delta-receptors) on a cell’s surface when they attack human cells. Colonno, taking advantage of the common receptors, devid a strategy for blocking the attachment of rhinovirus to their appropriate r
有道翻译器>韦伯斯特词典eceptors. Rather than fruitlessly arching for an antibody that would bind to all rhinovirus, Colonno realized that an antibody binding to the common receptors of a human cell would prevent rhinovirus from initiating an infection. Becau human cells normally do not develop antibodies to components of their own cells, Colonno injected human cells into mice, which did produce an antibody to the common receptor. In isolated human cells, this antibody proved to be extraordinarily effective at thwarting the rhinovirus. Moreover, when the antibody was given to chimpanzees, it inhibited rhinoviral growth, and in humans it lesned both the verity and duration of cold symptoms. Another possible defen against rhinovirus was propod by Rossman, who described rhinovirus’ detailed molecular structure. Rossman showed that protein quences common to all rhinovirus strains lie at the ba of a deep “canyon” scoring each face of the capsid. The narrow opening of this canyon possibly prevents the relatively large antibody molecules from binding to the common quence, but smaller molecules might reach it. Among the smaller, nonantibody molecules, some might bind to the common quence, lock the nucleic acid in its coat, and thereby prevent the virus from reproducing. 21. The primary purpo of the passage is to (A) discuss viral mechanisms and possible ways of circumventing certain kinds of tho mechanisms (B) challenge recent rearch on how rhinovirus bind to receptors on the surfaces of cells (C) suggest future rearch on rhinoviral growth in chimpanzees (D) defend a controve
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淘宝店铺公告怎么写rsial rearch program who purpo is to discover the molecular structure of rhinovirus capsids (E) evaluate a dispute between advocates of two theories about the rhinovirus life cycle 22. It can be inferred from the passage that the protein quences of the capsid that vary most among strains of rhinovirus are tho (A) at the ba of the “canyon” (B) outside of the “canyon” (C) responsible for producing nucleic acid (D) responsible for preventing the formation of delta-receptors (E) preventing the capsid from releasing its nucleic acid 23. It can be inferred from the passage that a cell lacking delta-receptors will be (A) unable to prevent the rhinoviral nucleic acid from shedding its capsid (B) defenless against most strains of rhinovirus (C) unable to relea the viral progeny it develops after infection (D) protected from new infections by antibodies to the rhinovirus (E) resistant to infection by most strains of rhinovirus 24. Which of the following rearch strategies for developing a defen against the common cold would the author be likely to find most promising? (A) Continuing to look for a general antirhinoviral antibody (B) Searching for common cell-surface receptors in humans and mice (C) Continuing to look for similarities among the various strains of rhinovirus (D) Discovering how the human body produces antibodies in respon to a rhinoviral infection (E) Determining the detailed molecular structure of the nucleic acid of a rhinovirus连锁店英文
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