Mechanical Properties of the High Cholesterol-Containing Membrane: An AFM Study

Authors

Nawal K. Khadka, Boise State UniversityFollow
Raju Timsina, Boise State UniversityFollow
Erica L. Rowe, Boise State University
Matthew O'Dell, Boise State University
Laxman Mainali, Boise State UniversityFollow

Document Type

Article

Publication Date

8-1-2021

Abstract

Cholesterol (Chol) content in most cellular membranes does not exceed 50 mol%, only in the eye lens’s fiber cell plasma membrane, its content surpasses 50 mol%. At this high concentration, Chol induces the formation of pure cholesterol bilayer domains (CBDs), which coexist with the surrounding phospholipid-cholesterol domain (PCD). Here, we applied atomic force microscopy to study the mechanical properties of Chol/phosphatidylcholine membranes where the Chol content was increased from 0 to 75 mol%, relevant to eye lens membranes. The surface roughness of the membrane decreases with an increase of Chol content until it reaches 60 mol%, and roughness increases with a further increment in Chol content. We propose that the increased roughness at higher Chol content results from the formation of CBDs. Force spectroscopy on the membrane with Chol content of 50 mol% or lesser exhibited single breakthrough events, whereas two distinct puncture events were observed for membranes with the Chol content greater than 50 mol%. We propose that the first puncture force corresponds to the membranes containing coexisting PCD and CBDs. In contrast, the second puncture force corresponds to the “CBD water pocket” formed due to coexisting CBDs and PCD. Membrane area compressibility modulus (K_A) increases with an increase in Chol content until it reaches 60 mol%, and with further increment in Chol content, CBDs are formed, and K_A starts to decrease. Our results report the increase in membrane roughness and decrease K_A at very high Chol content (>60 mol%) relevant to the eye lens membrane.

Copyright Statement

This is an author-produced, peer-reviewed version of this article. © 2021, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-No Derivatives 4.0 license. The final, definitive version of this document can be found online at Biochimica et Biophysica Acta (BBA): Biomembranes, https://doi.org/10.1016/j.bbamem.2021.183625

Creative Commons License

This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.

Publication Information

Khadka, Nawal K.; Timsina, Raju; Rowe, Erica L.; O'Dell, Matthew; and Mainali, Laxman. (2021). "Mechanical Properties of the High Cholesterol-Containing Membrane: An AFM Study". Biochimica et Biophysica Acta (BBA): Biomembranes, 1863(8), 183625. https://doi.org/10.1016/j.bbamem.2021.183625