(转贴)核酸、核苷酸的基本换算

核酸、核苷酸的基本换算
1．核酸的换算：
(1)摩尔数与质量：
1 μg 1,000bp DNA = 1.52 pmol
1 μg pUC18/19 DNA (2,688bp) = 0.57 pmol
1 μg pBR322 DNA (4,361bp) = 0.35 pmol
1 μg SV40 DNA (5,243bp) = 0.29 pmol
1 μg FX174 DNA (5,386bp) = 0.28 pmol
1 μg M13mp18/19 DNA (7.250bp) = 0.21 pmol
1 μg l phage DNA (48,502bp) = 0.03 pmol
1 pmol 1,000bp DNA = 0.66 μg
1 pmol pUC18/19 DNA (2,688bp) = 1.77 μg
1 pmol pBR322 DNA (4,361bp) = 2.88 μg
1 pmol SV40 DNA (5,243bp) = 3.46 μg
1 pmol FX174 DNA (5,386bp) = 3.54 μg
1 pmol M13mp18/19 DNA (7.250bp) = 4.78 μg
1 pmol l phage DNA (48,502bp) = 32.01 μg
(2)光吸收值与浓度：
1 OD260 dsDNA = 50 μg/ml = 0.15 mmol/L
1 OD260 ssDNA = 33 μg/ml = 0.10 mmol/L
1 OD260 ssRNA = 40 μg/ml = 0.12 mmol/L
1 mmol/L dsDNA = 6.7 OD260
1 mmol/L ssDNA = 10.0 OD260
1 mmol/L ssRNA = 8.3 OD260
(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：
环状DNA
pmol ends = pmol DNA × number of cuts ×2
线性DNA
pmol ends = pmol DNA ×(number of cuts ×2 + 2)
1 μg 1,000 bp DNA = 3.04 pmol ends
1 μg pUC18/19 DNA (2,688 bp) = 1.14 pmol ends
1 μg pBR322 DNA (4,361 bp) = 0.7 pmol ends
1 μg SV40 DNA (5,243 bp) = 0.58 pmol ends
1 μg FX174 DNA (5,386 bp) = 0.56 pmol ends
1 μg M13mp18/19 DNA (7.250 bp) = 0.42 pmol ends
1 μg l phage DNA (48,502 bp) = 0.06 pmol ends
2．核苷酸的换算：
(1)分子量：
MW (Da) = 333 × N (number of bases)
(2)浓度：
C (μmol/L or pmol/ml) = OD260 / (0.01 × N)
C (ng/ml) = OD260´ MW / (0.01 × N)
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25bp的双链寡核苷酸
Tm = 2 (A + T) + 4 (G + C)
长于25bp的双链寡核苷酸
Tm = 81.5 + 16.6 ( lg[J+] ) + 0.41 (%GC) - (600/N) - 0.63 (%formamide)
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 ≈2701 bp DNA
100,000 Da Protein ≈ 27 kb DNA