Natural electrophoresis of norepinephrine and ascorbic acid.
The electric field produced by cell membranes, extending only a few nanometers, is 1000 times stronger than the electric fields required to produce dissociation of molecular complexes. Using the complex formed by norepinephrine (NE) and ascorbic acid (AA), we have demonstrated the quantitative binding of AA to NE, the use of capillary electrophoresis to measure quantitative binding of nonelectrolyte complexes, the determination of a dissociation constant (Kd) from electric field-dissociation constants (Ke), and a model for natural dissociation of the NE-AA complex due to the electric field generated by a cell membrane. NE-AA dissociation constants show little effect of NE concentration or pH changes. NE-related compounds also bind AA: epinephrine > norepinephrine > tyrosine > histamine > phenylalanine. Serotonin does not bind AA. Phosphorylated AA and glucose also bind NE at 0.05 and 0.08 of the AA binding, respectively. Natural electrophoresis of molecular complexes allows compounds to travel through the body in a protected state and still be available for physiological activity upon reaching a membrane.
Dillon
P F
PF
Department of Physiology, Michigan State University, East Lansing, Michigan 48823, USA. dillon@psl.msu.edu
Root-Bernstein
R S
RS
Sears
P R
PR
Olson
L K
LK
D001205:Ascorbic Acid / Q000737:chemistry*; D001667:Binding, Competitive / Q000187:drug effects; D002462:Cell Membrane / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D019075:Electrophoresis, Capillary; D004837:Epinephrine / Q000737:chemistry; D005947:Glucose / Q000737:chemistry; D006632:Histamine / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological; D009638:Norepinephrine / Q000737:chemistry* / Q000494:pharmacology; D010649:Phenylalanine / Q000737:chemistry; D010766:Phosphorylation; D012701:Serotonin / Q000737:chemistry; D055672:Static Electricity; D014443:Tyrosine / Q000737:chemistry
D012701:Serotonin; D014443:Tyrosine; D010649:Phenylalanine; D006632:Histamine; D005947:Glucose; D001205:Ascorbic Acid; D009638:Norepinephrine; D004837:Epinephrine