Diffusion coefficients of retinoids.
OBJECTIVE
Diffusion coefficients of various retinoids have not been measured previously. It is important to know the diffusion coefficients of the retinoids because this property might be rate-limiting in dark adaptation. Also, retinoid diffusion is important to explore given that rhodopsin regeneration is not impaired in IRBP knockout mice.


METHODS
Measurements of lateral diffusion coefficients (D) of 9-cis-retinal, all-trans-retinal, and all-trans-retinol were made by Fourier transform pulsed-gradient spin-echo NMR measurements (FT-PGSE NMR) in several solvents. Also,(3)H-all-trans-retinoic acid was used to measure diffusion from an aqueous agarose matrix and absorption into a toluene based scintillation fluid in a biphase assay.


RESULTS
In a 1:1 mixture of CD(3)OD:D(2)O the D's of the retinoids were, 2.4 to 3.0 x 10(-6)cm( 2)/s. In the biphase assay,(3)H-all trans-retinoic acid exhibited a diffusion coefficient of 2.3 x 10(-6)cm(2)/s.


CONCLUSIONS
The lower than expected D for retinoids and our calculations suggest that mechanisms in addition to pure aqueous diffusion may be needed to account for normal rhodopsin regeneration rates in the mammalian retina.
Dodson
Christopher S
CS
Department of Ophthalmology, Emory University, Atlanta, GA 30322, USA.
Peresypkin
Andrey V
AV
Rengarajan
Kalpana
K
Wu
Shaoxiong
S
Nickerson
John M
JM
D000042:Absorption; D004058:Diffusion; D005583:Fourier Analysis; D019906:Nuclear Magnetic Resonance, Biomolecular; D012176:Retinoids / Q000737:chemistry*; D014783:Viscosity
D012176:Retinoids