核酸、核苷酸的基本换算

一、核酸的换算

1、 摩尔数与质量

1 μg 1,000bp DNA = 1.52 pmol

1 μg SV40 DNA (5,243bp) = 0.29 pmol

1 μg FX174 DNA (5,386bp) = 0.28 pmol

1 μg lambda phage DNA (48,502bp) = 0.03 pmol

1 μg M13mp18/19 DNA (7.249bp) = 0.21 pmol

1 μg pBR322 DNA (4,361bp) = 0.35 pmol

1 μg pUC18/19 DNA (2,686bp) = 0.57 pmol

1 pmol 1,000bp DNA = 0.66 μg

1 pmol M13mp18/19 DNA (7.249bp) = 4.78 μg

1 pmol SV40 DNA (5,243bp) = 3.46 μg

1 pmol pUC18/19 DNA (2,686bp) = 1.77 μg

1 pmol pBR322 DNA (4,361bp) = 2.88 μg

1 pmol lambda phage DNA (48,502bp) = 32.01 μg

1 pmol FX174 DNA (5,386bp) = 3.54 μg

2、 光吸收值与浓度

1 OD260 dsDNA = 50  μg/ml

1 OD260 ssDNA = 33  μg/ml

1 OD260 ssRNA = 40  μg/ml

3、 分子量

1个脱氧核糖核酸碱基的平均分子量为333 Daltons

1个核糖核酸碱基的平均分子量为340 Daltons

4、核酸末端浓度

线性DNA：pmol ends = pmol DNA ′ (number of cuts ′ 2 + 2)

环状DNA：pmol ends = pmol DNA ′ number of cuts ′ 2

1 μg 线性1,000bp DNA = 3.04 pmol ends

1 μg 线性 FX174 DNA (5,386bp) = 0.56 pmol ends

1 μg 线性 pUC18/19 DNA (2,686bp) = 1.14 pmol ends

1 μg 线性 SV40 DNA (5,243bp) = 0.58 pmol ends

1 μg 线性 pBR322 DNA (4,361bp) = 0.7 pmol ends

1 μg 线性 lambda phage DNA (48,502bp) = 0.06 pmol ends

1 μg 线性 M13mp18/19 DNA (7.249bp) = 0.42 pmol ends

二、核苷酸的换算

1、  分子量

MW (Da) = 333 ′ N (number of bases)

2、  浓度

C (mmol/L or pmol/ml) = OD260 / (0.01 ′ N) C (ng/ml) = OD260 ′ MW / (0.01 ′ N)

注：MW —— molecular weight；N —— number of bases；OD260 —— absorbance at 260 nm

3、  双链DNA与寡核苷酸的熔点：

短于20bp的双链寡核苷酸：Tm = 2 (A + T) + 4 (G + C)

长于20bp的双链寡核苷酸： Tm = 81.5 + 16.6 ( lg[J+] ) + 0.41 (%GC) –(600/N)

注： N —— 引物的长度(以碱基数计算)；J+ —— 单价阳离子浓度

4、  DNA与表达蛋白之间分子量换算

1 kb DNA = 333 amino acid ≈ 3.7 ′ 104 Da

10,000 Da Protein ≈ 270 bp DNA     30,000 Da Protein ≈ 810 bp DNA

50,000 Da Protein ≈ 1350 bp DNA     100,000 Da Protein ≈ 2700 bp DNA