Liquefaction of human vitreous in model aphakic eyes by 300-nm UV photolysis: monitoring liquefaction by fluorescence.
After the lens is removed in cataract surgery, the vitreous presumably receives all of the ambient 300-nm light that has filtered through the cornea. Using this model for aphakic eyes, we progressively irradiated intact vitreous samples of a 49-year-old human with 300-nm light and monitored changes in absorption, fluorescence, and circular dichroism (CD) properties. CD and fluorescence measurements of unirradiated vitreous samples showed a) a strong tryptophan fluorescence band of non-collagenous protein at 336 nm and a very weak band around 430 nm due to N-formylkynurenine (N-FK), a photoproduct of tryptophan, and b) a strong, negative CD band below 250 nm representing a composite spectrum of hyaluronic acid, collagen, and non-collagenous protein. Upon irradiation, the tryptophan emission band at 336 nm progressively decreased with time and the band maximum was concomitantly red-shifted; the N-FK fluorescence band at 430 nm, on the other hand, continually increased with the time of irradiation. A significant increase in the fluidity (liquefaction) of the vitreous gel also was noted upon irradiation, a change that was monitored successfully by measuring the progressive decrease in the polarization value of tryptophan fluorescence. The extent of liquefaction, measured spectroscopically, was found to be 40% upon irradiation for 10 hr. In addition, CD measurements indicated a partial loss in the secondary structure of the non-collagenous protein.
Ueno
N
N
Eye Research Institute, Boston, MA 02114.
Chakrabarti
B
B
D001036:Aphakia, Postcataract / Q000473:pathology*; D002942:Circular Dichroism; D005136:Eye Proteins / Q000378:metabolism; D005260:Female; D006801:Humans; D007737:Kynurenine / Q000378:metabolism; D008875:Middle Aged; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000378:metabolism; D014466:Ultraviolet Rays / Q000009:adverse effects*; D014783:Viscosity; D014822:Vitreous Body / Q000378:metabolism / Q000528:radiation effects*
D005136:Eye Proteins; D007737:Kynurenine; D014364:Tryptophan