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Table 1 Estimated and observed relative mobilities of some of the small molecules that were encountered in this report.

From: A versatile polyacrylamide gel electrophoresis based sulfotransferase assay

Moleculesa

Chargesb on -SO3-

Other Chargesb

q

m

q/m× 1000

Estimated Relative mobility (M')

Observed relative mobility

Dopamine-1S

-1

+1c

0

234.2

0.00

0.00

0.05

GlcNAc-Man-1S

-1

0

-1

477.4

-2.09

0.35

0.35

Estradiol-1S

-1

0

-1

352.4

-2.84

0.48

0.37

DHEA-1S

-1

0

-1

367.5

-2.72

0.46

0.45

Lithocholic acid-1S

-1

-1

-2

455.6

-4.39

0.74

0.63

Dopamine-2S

-2

0 ~ +1d

-2 ~ -1

312.2/313.2

-3.19 ~ -6.39

0.54 ~ 1.07

0.72

α-Naphthol-1S

-1

0

-1

224.2

-4.46

0.75

0.80

p-nitrophenol-1S

-1

0

-1

218.1

-4.59

0.77

0.96

APS

-1

-1

-2

425.28

-4.70

0.79

0.96

PAPS

-1

-2

-3e

504.3

-5.95

1.00

1.00

Bromophenol bluef

 

-2

-2

668

-2.99

0.50

0.63

Free sulfate

 

-2

-2

96

-20.83

3.5

1.24

  1. aNumbers of sulfate groups are indicated as -nS.
  2. bThe charge numbers on the molecules were estimated based on the numbers of their charged groups, such as -COO-, -NH3+ and -SO3-. Because some functional groups were partially charged due to the influence of other neighboring functional groups, the corresponding charge number and relative mobility were only estimation.
  3. cAssuming the -NH3+ on mono-sulfated dopamine (estimated pKa = 9.5) is completely protonated at pH 8.0.
  4. dAssuming the amine group on the di-sulfated dopamine can only partially protonated, because the two negatively charged sulfate groups could shift the pKa of the -NH3+ closer to 8.0.
  5. e Fully charged PAPS would have a charge number of -4; however, under the assay conditions, PAPS could be partially charged and the charge number -3 was assumed here. The most similar molecule, ATP, can exist in MgATP2-, ATP4- and ATP3- species [34] and overall charge number could be close to -3 too.
  6. fBromophenol blue has about half of the mobility of PAPS and is used as an indicator during electrophoresis.