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jmren3361銅蟲 (正式寫手)
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[求助]
熒光探針
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最近在學習熒光定量PCR,有幾個不懂的地方請教大家: TaqMan探針結(jié)合到模板上后,由于Taq酶的活性,被切割產(chǎn)生熒光 FRET、Molecular beacon、Scorpion primer結(jié)合到模板上后,是不是一直待在模板上?探針與模板的結(jié)合會不會影響PCR擴增?探針與模板的結(jié)合與PCR擴增是如何同步進行的? |
木蟲 (著名寫手)
清風小木蟲
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為了表達準確我來個外文的原文(麻煩自己翻譯,以免別人的產(chǎn)生誤解,原版的外文分子生物學,絕對錯不了。)SYBR® Green monitors the total amount of double-stranded DNA but cannot dis-tinguish between different sequences. To be sure that the correct target sequence is being amplified a sequence specific fluorescent probe is needed. An example is theTaqMan® probe (Applied Biosystems, Foster City, CA). The TaqMan® probe consistsof two fluorophores linked by a DNA sequence that will hybridize to the middle of the target DNA. Fluorescence resonance energy transfer (FRET) transfers the energy from the short-wavelength fluorophore on one end to the long wavelength fluorophore at the other end. This quenches the short wave emission. During PCR the TaqMan® probe binds to the target sequence after the denaturation step that separates the two DNA strands. As the Taq polymerase extends the primer during the next PCR cycle it will eventually bump into the TaqMan® probe.The Taq poly-merase is not only capable of displacing strands ahead of it but also has a 5‘-nuclease activity that degrades the DNA strand of the probe.This breaks the linkage between the two fluorophores and disrupts the FRET. The short-wavelength fluorophore is now free from quenching and its fluorescence increases. In this case the increase in fluorescence is directly related to the amount of the specific target sequence that has been amplified。 |
金蟲 (小有名氣)

木蟲 (正式寫手)
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1. 探針不是一直待在模板上,在變性的時候也會解鏈,但由于探針的退火溫度高(一般設計的時候會比引物的退火溫度高10度以上),在引物還沒有退火結(jié)合到模板上的時候,探針已經(jīng)退火和模板結(jié)合了,因此探針和模板的結(jié)合程度高于引物。 2. 探針與模板的結(jié)合會不影響PCR擴增,因為PCR的時候已經(jīng)有較穩(wěn)定的探針-模板結(jié)合物 3. Taq酶的3'切割活性會在遇到探針-模板結(jié)合物的時候切割探針,使PCR繼續(xù)下去 |
銅蟲 (正式寫手)
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