A derivative of all-trans-retinal (RAL) and ethanolamine, A2-E, is the main fluorescent component of human retinal lipofuscin. The accumulation of lipofuscin has been correlated with exposure to ambient radiation and loss of photoreceptors. A possible precursor to A2-E is the imine formed from RAL and ethanolamine. This compound, (E,E,E,E)-2-[9-(2-hydroxyethyl)imino-3,7-dimethyl-1,3,5,7-decatrien-1-yl]-1,3,3-trimethylcyclohexene (HIDD), has been synthesized and structurally characterized. The photophysical and photochemical properties of HIDD and its protonated form, HIDD-H , have been investigated using steady-state and time-resolved methods. Both HIDD and HIDD-H are weakly fluorescent, and the fluorescence lifetime and quantum yield for HIDD are ca 0.6 ns and 4.0 ± 0.5 × 10–4, respectively. HIDD forms a triplet excited state on direct excitation that decays with kd = 3.4 × 104 s–1. The extinction coefficient and quantum yield of intersystem crossing for the HIDD triplet are measured as 7.6 ± 1.3 × 104 M–1cm–1 and 0.055 ± 0.006, respectively. The triplet excited state of HIDD-H can be sensitized by triplet energy transfer and has a decay rate constant of 1.6 × 104 s–1. The lifetime of the HIDD triplet excited state is observed to decrease with increasing concentration of the well-known electron or hydrogen atom donors, 2,3,5,6-tetramethyl-1,4-phenylenediamine and 2,3,5-trimethylhydroquinone, and the bimolecular rate constants for these reactions are approximately 5.4 × 106 M–1s–1 and 1.7 × 108 M–1s–1, respectively. These types of reactions may model photooxidative mechanisms of damage in the retina.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 78 • No. 3