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Nucleic Acids and Protein Calculations Spectrophotometric Conversions
**This web page provides several useful tables of common biological constants and conversions. These include metric prefixes, spectrophotometiric conversions, agarose/polyacrylamide gel resolutions, etc. You can use these tables to aid your DNA/RNA/protein quantification, electrophoresis gel preparation, protein synthesis, calculating molecular mass and other research activities in molecular biology..

Metric Prefixes
Prefix Symbol Factor
kilo k 103
centi c 10-2
milli m 10-3
micro µ 10-6
nano n 10-9
pico p 10-12
femto f 10-15
atto a 10-18
zepto z 10-21

Spectrophotometric Conversions
1 A260 unit of double-stranded DNA=50 µg/ml
1 A260 unit of single-stranded DNA=33 µg/ml
1 A260 unit of single-stranded RNA=40 µg/ml

DNA Molar Conversions
1 µg of 1,000 bp DNA 1.52pmol(3.03pmol of ends)
1 µg of pBR322 DNA 0.36pmol DNA
1 pmol of 1,000 bp DNA 0.66 µg
1 pmol of pBR322 DNA 2.8 µg
pBR322DNA:(4,361bp)

Formulas for DNA Molar Conversions
For dsDNA
To convert pmol to µg:
pmol × N × 660 pg/pmol × 1 µg/106pg = µg
To convert µg to pmol:
µg × 106pg/1 µg × pmol/660pg × 1/N = pmol
For ssDNA
To convert pmol to µg:
pmol × N × 330 pg/pmol × 1µg/106pg = µg
To convert µg to pmol:
µg × 106pg/1 µg × pmol/330pg × 1/N = pmol
where N is the number of nucleotides and 330 pg/pmol is the average MW of a nucleotide

Protein Molar Conversions
100 pmol of 100 kDa protein = 10 µg
100 pmol of 50 kDa protein = 5 µg
100 pmol of 10 kDa protein = 1 µg
100 pmol of 1 kDa protein = 100 ng

Protein/DNA Conversions
1 kb DNA 333 amino acids
  37 kDa protein
270 b DNA 10 kDa protein
810 b DNA 30 kDa protein
1.35 kb DNA 50 kDa protein
2.7 kb DNA 100 kDa protein
average MW of an amino acid 110 daltons
Dalton (Da) is an alternate name for the atomic mass unit, and kilodalton (kDa) is 1,000 daltons. Thus a protein with a mass of 64 kDa has a molecular weight of 64,000 grams per mole

Agarose Gel(%):Resolution of Linear DNA
Recommended % Agarose Optimum Resolution for Linear DNA
(Size of fragments in nucleotides;bp)
0.5 1,000-30,000
0.7 800-12,000
1.0 500-10,000
1.2 400-7,000
1.5 200-3,000
2.0 50-2,000

Polyacrylamide Gel(%):Resolution of Protein
Recommended % Acrylamide Protein Size Range
8 40-200 kDa
10 21-100 kDa
12 10-40 kDa

Length/M.W. of Common Nucleic Acids.
Nucleic Acid Number of Nucleotides Molecular Weight
lambda DNA 48,502(dsDNA) 3.2 × 107
pBR322DNA 4,361(dsDNA) 2.8 × 106
28S rRNA 4,800 1.6 × 106
23S rRNA(E.coli) 2,900 1.0 × 106
18S rRNA 1,900 6.5 × 105
16S rRNA(E.coli) 1,500 5.1 × 105
5S rRNA(E.coli) 120 4.1 × 104
tRNA(E.coli) 75 2.5 × 104
*Molecular weights based on actual sequence.

Standards
1. Average MW of dsDNA base pair = 600.
2. Average MW of ssDNA base =330.
3. Average MW of RNA base =340.