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Title: Arabinose substitution effect on xylan rigidity and self-aggregation

Substituted xylans play an important role in the structure and mechanics of the primary cell wall of plants. Arabinoxylans (AX) consist of a xylose backbone substituted with arabinose, while glucuronoarabinoxylans (GAX) also contain glucuronic acid substitutions and ferulic acid esters on some of the arabinoses. Here, we provide a molecular-level description on the dependence of xylan conformational, self-aggregation properties and binding to cellulose on the degree of arabinose substitution. Molecular dynamics simulations reveal fully solubilized xylans with a low degree of arabinose substitution (lsAX) to be stiffer than their highly substituted (hsAX) counterparts. Small-angle neutron scattering experiments indicate that both wild-type hsAX and debranched lsAX form macromolecular networks that are penetrated by water. In those networks, lsAX are more folded and entangled than hsAX chains. Increased conformational entropy upon network formation for hsAX contributes to AX loss of solubility upon debranching. Furthermore, simulations show the intermolecular contacts to cellulose are not affected by arabinose substitution (within the margin of error). Ferulic acid is the GAX moiety found here to bind to cellulose most strongly, suggesting it may play an anchoring role to strengthen GAX-cellulose interactions. The above results suggest highly substituted GAX acts as a spacer, keeping cellulose microfibrils apart,more » whereas low substitution GAX is more localized in plant cell walls and promotes cellulose bundling.« less
Authors:
ORCiD logo [1] ;  [1] ; ORCiD logo [1] ;  [2] ;  [3] ;  [2] ;  [2] ;  [2] ;  [4] ;  [2] ; ORCiD logo [1] ; ORCiD logo [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Pennsylvania State Univ., University Park, PA (United States)
  3. New York City College of Technology, New York, NY (United States)
  4. Univ. of Texas at El Paso, El Paso, TX (United States)
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Cellulose
Additional Journal Information:
Journal Volume: 26; Journal Issue: 4; Journal ID: ISSN 0969-0239
Publisher:
Springer
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; Plant cell wall; Xylan; Molecular simulation; Neutron scattering
OSTI Identifier:
1502603

Shrestha, Utsab R., Smith, Sydney, Pingali, Sai Venkatesh, Yang, Hui, Zahran, Mai, Breunig, Lloyd, Wilson, Liza A., Kowali, Margaret, Kubicki, James D., Cosgrove, Daniel J., O’Neill, Hugh M., and Petridis, Loukas. Arabinose substitution effect on xylan rigidity and self-aggregation. United States: N. p., Web. doi:10.1007/s10570-018-2202-8.
Shrestha, Utsab R., Smith, Sydney, Pingali, Sai Venkatesh, Yang, Hui, Zahran, Mai, Breunig, Lloyd, Wilson, Liza A., Kowali, Margaret, Kubicki, James D., Cosgrove, Daniel J., O’Neill, Hugh M., & Petridis, Loukas. Arabinose substitution effect on xylan rigidity and self-aggregation. United States. doi:10.1007/s10570-018-2202-8.
Shrestha, Utsab R., Smith, Sydney, Pingali, Sai Venkatesh, Yang, Hui, Zahran, Mai, Breunig, Lloyd, Wilson, Liza A., Kowali, Margaret, Kubicki, James D., Cosgrove, Daniel J., O’Neill, Hugh M., and Petridis, Loukas. 2019. "Arabinose substitution effect on xylan rigidity and self-aggregation". United States. doi:10.1007/s10570-018-2202-8.
@article{osti_1502603,
title = {Arabinose substitution effect on xylan rigidity and self-aggregation},
author = {Shrestha, Utsab R. and Smith, Sydney and Pingali, Sai Venkatesh and Yang, Hui and Zahran, Mai and Breunig, Lloyd and Wilson, Liza A. and Kowali, Margaret and Kubicki, James D. and Cosgrove, Daniel J. and O’Neill, Hugh M. and Petridis, Loukas},
abstractNote = {Substituted xylans play an important role in the structure and mechanics of the primary cell wall of plants. Arabinoxylans (AX) consist of a xylose backbone substituted with arabinose, while glucuronoarabinoxylans (GAX) also contain glucuronic acid substitutions and ferulic acid esters on some of the arabinoses. Here, we provide a molecular-level description on the dependence of xylan conformational, self-aggregation properties and binding to cellulose on the degree of arabinose substitution. Molecular dynamics simulations reveal fully solubilized xylans with a low degree of arabinose substitution (lsAX) to be stiffer than their highly substituted (hsAX) counterparts. Small-angle neutron scattering experiments indicate that both wild-type hsAX and debranched lsAX form macromolecular networks that are penetrated by water. In those networks, lsAX are more folded and entangled than hsAX chains. Increased conformational entropy upon network formation for hsAX contributes to AX loss of solubility upon debranching. Furthermore, simulations show the intermolecular contacts to cellulose are not affected by arabinose substitution (within the margin of error). Ferulic acid is the GAX moiety found here to bind to cellulose most strongly, suggesting it may play an anchoring role to strengthen GAX-cellulose interactions. The above results suggest highly substituted GAX acts as a spacer, keeping cellulose microfibrils apart, whereas low substitution GAX is more localized in plant cell walls and promotes cellulose bundling.},
doi = {10.1007/s10570-018-2202-8},
journal = {Cellulose},
number = 4,
volume = 26,
place = {United States},
year = {2019},
month = {1}
}

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