Molecular Interactions at the Cellulose-Lignin Interface ...
Transcript of Molecular Interactions at the Cellulose-Lignin Interface ...
![Page 1: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/1.jpg)
Molecular Interactionsatthe Cellulose-Lignin Interface Exploredvia Molecular Simulation
Josh Vermaas, Gregg Beckham, and Michael Crowley
Fall 2019ACSNational Meeting San Diego, California
August28th,2019 NREL/PR-2700-74305
![Page 2: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/2.jpg)
LigninIntroduction
• Ligninisanaromatic heteropolymerthatmakesup between15-40%ofthedry weightofterrestrialplants
• Largestsourceofrenewable aromatics
• Manypotentialindustrialuses • Implicatedasasignificant
driverofcellwallrecalcitrance
2
![Page 3: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/3.jpg)
LignocelluloseSimulation
Vermaasetal.2015 3
![Page 4: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/4.jpg)
LigninBindstoCellulose…
• Lignincoversroughlya quarterofthecellulose surface
• Doesitcoatthesurface evenly?
• Doesligninchemistry matter?
Vermaasetal.2015 4
![Page 5: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/5.jpg)
…ParticularlyHydrophobicCelluloseFaces
• Prefershydrophobicfaces • Blockscellulasebinding • Canwequantifythethermodynamic
preferencebetweenfaces?
Vermaasetal.2015 5
![Page 6: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/6.jpg)
TheManyFacesofCellulose
• Onlythe200faceis hydrophobic
• Otherprimaryfacesare hydrophilic
• Normalcellulosetwists • Infinitecellulosedoesnot
6
Fernandesetal.2015
![Page 7: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/7.jpg)
200 110
1-10 010
TheNextExperiment
• Construct“infinite”sheetsof cellulosewithdifferentfaces exposedtosolution
• Placeligninderivedcompounds insolution
• Simulate for 200 ns • Determine binding free energies
ofcompoundstoindividualfaces
7
![Page 8: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/8.jpg)
WhatCompounds? OH OH OH OH
O OH
R' R Gua
iaco
l (G) Ph
enol (H)
HO
β1
* *
HO
O O
ββ
* *
* *
OH
OH
O
OH
OH O O O
OH OH
O
Syring
ol (S)
OH
O O α-ester γ-ester Phenolics OH OH
O *
*
OH
OH OH Ca
tech
ol (C)
OH HO 4O5 HO
OH β5 OH
OH
* O HO
O HO O
OHHO
*
OH O
R R' R R' OH
* *
Chiralcenter
OH O OH
R
OH OH R' OH OH
Monolignols 5-5 αO4 & βO4 βO4 8
![Page 9: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/9.jpg)
PotentialBindingMetricsforFreeEnergyDetermination
• Free energy isrelatedto probability
• Trajectoriescanbeusedto determinerelative probabilities
• Howdowedefineabound vs unbound state?
9
![Page 10: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/10.jpg)
DistanceandContactMetrics, Compared
• Distance • LigninCenter of
masstocellulose centerofmass
• Veryeasytoexplain • Contactnumber
• Pairwisecontacts betweencellulose andlignin
• Isnotbiasedby ligninshape
Unb
ound
Bo
und
Unb
ound
10
![Page 11: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/11.jpg)
CelluloseBindingforMonomers
• Hydrophobic200face predominantforbinding
• Ferulatepreferssolution • Fitswellwithits
physiologicalrole • 110facebetterfor
bindingthantheother OH OH OH OH OH OH OH OH OH OH OH MeO OMe OMe OH MeO MeO OMe OH MeO OH MeO MeO hydrophilicfaces
OH
O OH OH O O OH O OH
11
![Page 12: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/12.jpg)
MultimericBinding
• 200>>110>010>1-10 • Planarligninmoleculeslike
estersdemonstrateparticular affinitytothe200face
• Comparisonsbetween stereoisomerssuggestlonger simulationmaybebeneficial
12
![Page 13: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/13.jpg)
��
����
1
2
3
4
5
6
CelluloseFace-DependentBindingRelationships
100
G
bindi
ng
(kT
) 0
-
-
-
-
-
-r2 = 0.77 r2 = 0.56 r2 = 0.44
P henols Alcohols Carboxylates ↵O4& O4 O4
55 4O5 Esters 1 5
-2 0 -2 0 -2 0 110 Gbinding (kT) 1-10 Gbinding (kT) 010 Gbinding (kT) 13
![Page 14: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/14.jpg)
14
HowDoesBindingScalewithPolymerSize?
• Monomersanddimersarenot perfectmodelsforreallignin
• Drawfromestablishedlignin polymerlibraries
• Determine ligninbinding affinity
![Page 15: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/15.jpg)
UnbiasedLigninContactstoCellulose
15
![Page 16: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/16.jpg)
TechnicalChallenges
• Bindingisspontaneousand irreversibleontypicalMD timescalesforlargerlignin
• Usereplicaexchangeumbrella samplingonacontact-number reactioncoordinatetoestimate binding free energy
16
![Page 17: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/17.jpg)
SurfaceAreaComparison
• Contactnumberasdefinedisa strongproxyforcontactsurface areabetweenligninandcellulose
16.0 kDa lignin polymer 1200 200
110
1-10 1000 010
800
600
400
200
0
0 500 1000 1500 A2) 17 Lignin-Cellulose Contact Area (˚
Lig
nin
-Cel
lulo
se C
onta
cts
![Page 18: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/18.jpg)
BindingFreeEnergyProfiles
18
![Page 19: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/19.jpg)
SizeDependenceofLignin-CelluloseInteractions
• Bindingfreeenergygrows withthelogarithmofthe ligninmass
• Trendisweak, highly inconsistent
19
• Bindingfreeenergygrows directlywiththenumberof contactspresentatthefree energy minimum
• Slopesareconsistentacross faces
CelluloseFace 200 0.0111 110 0.0083 1-10 0.0107 010 0.0107
![Page 20: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/20.jpg)
Summary
• Bindingstrengthquantificationcaninformligninmodification • Ligninrelatedcompoundsprefer tobindtohydrophobic cellulose
facesbyaboutafactorof2 • Mayberelatedtothe“flatness”ofthe200face, whichfits
wellwithplanararomaticrings, creatingmorenonspecific interactionsites
• Lignincontactnumber/contactareaismoreimportantthan polymersizeindeterminingbindingstrength • Ligninagglomerationisnotconsidered, butwouldlikely
additivelyincreasebindingstrength 20
![Page 21: Molecular Interactions at the Cellulose-Lignin Interface ...](https://reader030.fdocuments.us/reader030/viewer/2022012501/617ac80602659b17dd0477bc/html5/thumbnails/21.jpg)
GreggBeckham MichaelCrowley
Questions?
www.nrel.gov
This work was authored by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding provided by the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Bioenergy Technologies Office. The views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for U.S. Government purposes.