Nucleic Acid MW
ssDNA (e.g., Oligonucleotides)
MW = (An x 313.2) 
   + (Tn x 304.2) 
   + (Cn x 289.2) 
   + (Gn x 329.2) 
   + 79.0 (5’-P if any)
   An, Tn, Cn, and Gn number of each nucleotide.
Average MW of a base = 330 (with sodium)
dsDNA
Average MW of a DNA base pair = 660 (610 without sodium)
Average dsDNA MW = 660 x N (N – number of base pairs)

Oligonucleotide Concentration
C (µM or pmol/µl) = A260 / (0.01 x N) 
C (ng/ml) = (A260 x MW) / (0.01 x N) 
MW - molecular weight or relative molecular mass (Mr) 
A260 - absorbance at 260nm 
N - number of bases

DNA Spectrophotometric Conversions 
ds DNA: 1.0 A260 unit = 50 µg/ml = 0.15 mM (in nucleotides) 
ss DNA: 1.0 A260 unit = 33 µg/ml = 0.10 mM (in nucleotides) 

1 mM dsDNA (in nucleotides) = 6.7 A260 units 
1 mM ssDNA (in nucleotides) = 10.0 A260 units 

Molar Conversions for common plasmids
1 µg of 1000 bp DNA = 1.52 pmol 
                    = 9.1 X 1011 molecules 
1 µg of pUC18/19 DNA (2686 bp) = 0.57 pmol 
                               = 3.4 X 10(11) molecules 
1 µg of pBR322 DNA (4361 bp) = 0.35 pmol 
                             = 2.1 X 10(11) molecules 
1 µg of SV40 DNA (5243 bp) = 0.29 pmol 
1 µg of PhiX174 DNA (5386 bp) = 0.28 pmol 
1 µg of M13mp18/19 DNA (7249 bp) = 0.21 pmol 
                                 = 1.3 X 10(11) molecules 
1 µg of lambda phage DNA (48502 bp) = 0.03 pmol 
                                    = 1.8 X 10(10) molecules

1 pmol of 1000 bp DNA = 0.66 µg 
1 pmol of pUC18/19 DNA (2686 bp) = 1.77 µg 
1 pmol of pBR322 DNA (4361 bp) = 2.88 µg 
1 pmol of SV40 DNA (5243 bp) = 3.46 µg 
1 pmol of PhiX174 DNA (5386 bp) = 3.54 µg 
1 pmol of M13mp18/19 DNA (7250 bp) = 4.78 µg 
1 pmol of lambda phage DNA (48502 bp) = 32.01 µg

DNA Coding capacity
1.0 kb DNA = 333 amino acids 
10 kDa protein @ 270 bp DNA 
37 kDa protein @ 1.0 kb DNA
50 kDa protein @ 1.35 kb DNA 

DNA End Concentration 
ends (pmol) = DNA (pmol) x (number of cuts x 2)
Add one cut if the DNA was already linear before cleavage

1 µg of 1000 bp DNA = 3.04 pmol ends 
1 µg of linearized pUC18/19 DNA = 1.14 pmol ends 
1 µg of linearized pBR322 DNA = 0.7 pmol ends
1 µg of linearized SV40 DNA = 0.58 pmol ends 
1 µg of linearized PhiX174 DNA = 0.56 pmol ends 
1 µg of linearized M13mp18/19 DNA = 0.42 pmol ends 
1 µg of linearized lambda phage DNA = 0.06 pmol ends

Nucleotide Properties
Compound MW      λmax (nm) e (M-1 x cm-1)
Ribonucleotide Triphosphates      (Avg. MW = 499.5)
ATP      507.2   259       15,400
CTP      483.2   271        9,000
GTP      523.2   253       13,700
UTP      484.2   262       10,000

Deoxyribonucleotide triphosphates (Avg. MW = 487.0)
dATP     491.2   259       15,200
dCTP     467.2   271        9,300
dGTP     507.2   253       13,700
dTTP     482.2   267        9,600

lambda max determined at pH 7.0 
e = molar absorption coefficient 
  = absorbance at lambda max for 1 M solution at pH 7.0.

Nucleotide Conversion Formula 
C = A / e x 10(3), where 
C - mM concentration of compounds 
A - absorbance at λmax (OD) for 1 cm cuvette
e - molar absorption coefficient (M-1 x cm-1)

Base Pair Structure