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Nucleic Acids and Protein Calculations
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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 and other research activities.
Metric Prefixes
Spectrophotometric Conversions
DNA Molar Conversions
Formulas for DNA Molar Conversions
Protein Molar Conversions
Protein/DNA Conversions
Agarose Gel(%):Resolution of Linear DNA
Polyacrylamide Gel(%):Resolution of Protein
Length/M.W. of Common Nucleic Acids.
Standards
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
≈
1.52 pmol(3.03 pmol of ends)
1 µg of pBR322 DNA
≈
0.36 pmol 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/106 pg = µg
To convert µg to pmol:
µg × 106 pg/1 µg × pmol/660 pg × 1/N = pmol
For ssDNA
To convert pmol to µg:
pmol × N × 330 pg/pmol × 1µg/106 pg = µg
To convert µg to pmol:
µg × 106 pg/1 µg × pmol/330 pg × 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.
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