Nanoscale structural analyses on Rod Outer Segments (ROS) membranes and retina of bovine eye: 3D structure of photoreceptor nanodomains


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Orujalipoor I., Erbakan M. , İde S.

Journal of Nanomedicine, vol.3, no.1, pp.1-8, 2020 (Refereed Journals of Other Institutions)

  • Publication Type: Article / Article
  • Volume: 3 Issue: 1
  • Publication Date: 2020
  • Doi Number: 10.33582/2578-8760/1018
  • Title of Journal : Journal of Nanomedicine
  • Page Numbers: pp.1-8

Abstract

The present study aims nanoscopic observation and detection of rhodopsin (a G protein- coupled receptor) nanodomains in their native biological environment to investigate their kinematics related to the photocycle. In the first phase of the planned work, the retina segments were obtained from bovine eyeballs and different sample preparation methods were tested to identify the densely packed rhodopsin nanodomains.

Transmission Small- and Wide-Angle X-Ray Scattering (SAXS and WAXS) methods were used for nanoscale analyses of the prepared samples. The compact conformations of rhodopsin nanodomains in the structure of the native retina and the Rod Outer Segments (ROS) isolated from retina were elucidated. The related scattering data were used to reveal nanoscale morphologies and internal structures of the rhodopsin nanodomains. Nanostructure of rhodopsin within the intact retina was also directly identified to compare the rhodopsin structure in isolated ROS. Direct measurement of the retina reveals similar hierarchical structure defined by paracrystalline arrays suggesting that nanostructural features of rhodopsin domains.

The quantitative results indicate an inter-disk spacing of 30.00 nm and a bilayer thickness of 6.84 nm for the ROS membrane. 3D structure of the rhodopsin was also characterized by ellipsoidal globules including sizes of the main axes and electron densities. The results showed that SAXSWAXS analyses are effective in monitoring the nanoscale bioactivation of rhodopsin in retina and the flexible cylinder model is in good coherence with the alpha-helical transmembrane domains of rhodopsin.