计算溶液所需的质量、体积或浓度。
Reverse transcriptases are enzymes encoded in retroviruses viral genome. The enzyme is responsible for transcription of the viral RNA to produce a dsDNA that can be inserted into the host genome.
Reverse transcriptases are multifunctional enzymes. These enzymes exhibit an RNA and DNA directed polymerase activity. In addition reverse transcriptases catalyze the degradation of RNA in an RNA-DNA hybrid. The exonucleolytic activity proceeds in a 5' ---> 3' direction. The RNA or DNA directed activity requires a template (RNA or DNA) and a primer. The following is a schematic illustration of the reaction:
Unit definition: One unit incorporates 1 nanomole of tritiated dTMP into acid insoluble productsusing poly(A)•oligo(dT) 12-18 as the template-primer in 20 minutes at 37° C.

Applications
HIV reverse transcriptase is used for research on the AIDS primer. However it can be substituted for AMV reverse transcriptase, which is mainly used to transcribe mRNA into double stranded cDNA, that can be inserted into prokaryotic vectors. The enzyme can also be used with either single stranded DNA or RNA templates to make probes for use in hybridization experiments. It can be used for labeling the termini of DNA fragments with protruding 5' termini. The enzyme can also be used to sequence DNAs by the dideoxy chain termination method of Sanger when the Klenow fragment of E. coli DNA polymerase I, or the T7 DNA polymerase yield unsatisfactory results.
Reagents
0.05 M Tris, pH 8.3, containing 0.008 M MgCl2
1 mg/ml polyadenylic acid in water (poly A)
DNA primer:Oligo d(T)12-18
1 μ mole dTTP/mL stock solution
[methyl-3H]-Thymidine 5'-triphosphate (3H-dTTP)
dTTP-3H-dTTP working mix: Add 1-2 μL 3H-dTTP per mL of 100 nmol/mL dTTP in order to obtain 1 to 1.5 x 105 cpm/mL
1% bovine serum albumin
10% perchloric acid
1% perchloric acid
Buffer substrate reaction mixture: Prepare fresh, immediately before use:
For each 1mL of reaction mixture required mix:
0.7 mL Tris/HCl, pH 8.3, 0.008M MgCl2
0.3 mL 1 mg/mL poly(A) RNA template
0.005 mL 0.02 mg/mL oligo d(T)12-18 DNA primer
0.02mL 1% BSA
Enzyme
dilute as needed wtih 0.05M Tris/HCl, pH 8.3, 0.008M MgCl2 containing 0.1 mg/mL (1%) BSA
Procedure
Pipette into each tube as follows:
Buffer substrate mix:0.1 mL
dTTP-3H3-dTTP:0.1 mL
Enzyme:5-10 μL
Incubate 20 minutes at 37° C. Stop reaction by adding 1 ml 10% cold perchloric acid. Filter through 0.2μ manifold filters used with Millipore vacuum manifold. Wash four times using 2mL 1% cold perchloric acid/wash. Transfer filter to scintillation vials. Add 2mL Cellosolve (or 2-methoxyethanol) to dissolve filter. Filters become opaque upon addition of Cellosolve. Make sure filters are dissolved before proceeding. Add 10mL scintillation cocktail and count.
Calculation
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