Resolving the Morphology of Peptoid Vesicles at the 1 nm Length Scale Using Cryogenic Electron Microscopy

Journal Article · 10 January 2019 · Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry

DOI: https://doi.org/10.1021/acs.jpcb.8b11752 · OSTI ID:1492105

Jiang, Xi  ^[1]; Spencer, Ryan K. ^[1]; Sun, Jing  ^[2]; Ophus, Colin ^[1]; Zuckermann, Ronald N.  ^[1]; Downing, Kenneth H.  ^[1]; Balsara, Nitash P.  ^[3]

---

1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
2. Qingdao Univ. of Science and Technology, Qingdao (China)
3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)

Vesicle formation in a series of amphiphilic sequence-defined polypeptoid block co-polymers comprising a phosphonated hydrophilic block and an amorphous hydrophobic block, poly-N-(2-ethyl)hexylglycine-block-poly-N-phosphonomethylglycine (pNeh-b-pNpm), is studied. The hydrophobic/hydrophilic block ratio was varied keeping the total chain length of the co-polymers constant. A new approach for characterizing the vesicle membrane morphology based on low-dose cryogenic electron microscopy (cryo-EM) is described. The individual low-dose micrographs cannot be interpreted directly due to low signal-to-noise ratio. Sorting and averaging techniques, developed in the context of protein structure determination, were thus applied to vesicle micrographs. Molecular dynamic simulations of the vesicles were used to establish the relationship between membrane morphology and averaged cryo-EM images. This approach enables resolution of the local thickness of the hydrophobic membrane core at the 1 nm length scale. The thickness of the hydrophobic core of the pNeh-b-pNpm membranes increases linearly with the length of the hydrophobic block.

• Research Organization: University of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1492105
• Alternate ID(s): OSTI ID: 1508807; OSTI ID: 1594906
• Journal Information: Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry, Vol. 123, Issue 5; ISSN 1520-6106
• Publisher: American Chemical SocietyCopyright Statement
• Country of Publication: United States
• Language: English