TABLE 1.

Biochemically and pharmacologically relevant characteristics of MB and leucoMB^a

Parameter	Value(s)	Reference(s) and/or source
Redox potential (mV)
MB+/leucoMB	+11	20, 41
MB+/MB radicalb	−230
pKa
MB	∼0	41, 51
leucoMB	4.5, 5.8
MB radical	9
Solubility
MB trihydrate at pH 7.0 [mg/ml (mM)]	20 (53.4)	20 and this report
LeucoMB (μM)	<50
ε value (mM−1 cm−1)c
MB
340 nm	3.90	This report
455 nm	1.1	45, 46
613 nm	40.0	45, 46
leucoMB
258 nm	17.2 (peak)	This report
320 nm	4.0 (peak)
340 nm	3.30
Between 380 and 800 nm	<0.1
Fluorescence (nm)	664 (excitation), 682 (emission)	21
Monomer-dimer equilibrium of MB (μM)	170 < Kdiss < 252	3, 41, 51
Binding of MB to bovine serum albumin (Kdiss) (μM)	2.90	58
Adsorption to surfaces	Langmuir data	20, 41, 47
EC50 of MB against P. falciparum in vitro (nM) ± SDd	6.5 ± 1.8	2
Therapy of malaria in children using MB (mg/kg of body wt) orally over 3 days	36-72	39
Treatment of hereditary methemoglobinemia using MB (mg) orally per day	250	17

^aUnless stated otherwise, the in vitro data refer to 100 mM phosphate buffer at pH 7.0.

^bTwo MB radicals disproportionate to give MB and leucoMB. This explains why erroneous midpoint potentials of less than −200 mV have also been reported for the MB⁺/leucoMB pair, e.g., by Atamna et al. and Schirmer et al. (6, 51).

^cMB exhibits absorption peaks at 250, 292, and 663 nm with ε values of 18, 38, and ∼75 mM⁻¹ cm⁻¹, respectively. leucoMB showed peaks at 210 nm, 258 nm, and 320 nm, with the ε values being >60, 17.4, and 4.0 mM⁻¹ cm⁻¹, respectively.

^dEC₅₀, 50% effective concentration.