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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	≈	1.52pmol(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.