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Statistical Mechanical Studies of Titrating Polyelectrolytes

Ullner, Magnus LU (1996)
Abstract (Swedish)
Popular Abstract in Swedish

Som titeln antyder behandlar avhandlingen titrerande polyelektrolyter, d.v.s. stora molekyler med många syra-basgrupper. Sådana molekyler kan vi finna lite överallt, ja till och med i våra kroppar, som innehåller en mängd olika polyelektrolyter. Deras egenskaper kan variera starkt beroende på omständigheterna och har många biologiska och industriella tillämpningar. Att en molekyl titrerar innebär att dess laddning ändras och den elektrostatiska växelverkan leder till förändrade syra-basegenskaper. Hos vissa polyelektrolyter sker dessutom strukturella förändringar. Effekterna påverkas både av egenskaper hos molekylen själv, t.ex. antalet titrerande grupper och avstånden mellan dessa, och av den... (More)
Popular Abstract in Swedish

Som titeln antyder behandlar avhandlingen titrerande polyelektrolyter, d.v.s. stora molekyler med många syra-basgrupper. Sådana molekyler kan vi finna lite överallt, ja till och med i våra kroppar, som innehåller en mängd olika polyelektrolyter. Deras egenskaper kan variera starkt beroende på omständigheterna och har många biologiska och industriella tillämpningar. Att en molekyl titrerar innebär att dess laddning ändras och den elektrostatiska växelverkan leder till förändrade syra-basegenskaper. Hos vissa polyelektrolyter sker dessutom strukturella förändringar. Effekterna påverkas både av egenskaper hos molekylen själv, t.ex. antalet titrerande grupper och avstånden mellan dessa, och av den omgivande lösningen, vars salthalt kan reducera den elektrostatiska växelverkan.



Detta är vad vi har studerat. Vi har tillämpat och jämfört en rad olika teoretiska metoder och modeller. Bland de statistisk mekaniska tekniker vi använt har Monte Carlo simulering en särställning, eftersom "rätt svar" erhålls för en given modell utan ytterligare approximationer. Simuleringarna fungerar alltså i viss mån som "facit" och utgör en lämplig referens vid utvärderingen av olika modeller och metoder. Förutom simuleringarna har vi utnyttjat olika former av variationsberäkningar och integralekvationsteori samt undersökt ett antal stela modeller som tidigare förekommit i litteraturen. Det faller sig ju även naturligt att jämföra med experiment, vilket vi också har gjort.



Avhandlingen vänder sig i första hand till personer som har ett särkilt intresse av titrerande polyelektrolyter, men sammanfattningen är ändå skriven utifrån ett minimalt krav på förkunskaper och är en genomgång av de grundläggande begrepp och teorier som används i artiklarna. (Less)
Abstract
Different models and statistical mechanical approximations for titrating polyelectrolytes are studied and the results compared with Monte Carlo simulations and experimental data. Three types of models have been used in the simulations: i) rigid structures and freely jointed chains with ii) rigid bonds and iii) flexible, harmonic bonds. Sampling is facilitated for the latter two by the use of pivot algorithms, which allow simulations of literally thousands of monomers. Electrostatic interactions are treated within the primitive model. There are no interactions between macromolecules; only single chain properties are investigated.



The main part of the thesis is devoted to the study of flexible polyelectrolytes, which... (More)
Different models and statistical mechanical approximations for titrating polyelectrolytes are studied and the results compared with Monte Carlo simulations and experimental data. Three types of models have been used in the simulations: i) rigid structures and freely jointed chains with ii) rigid bonds and iii) flexible, harmonic bonds. Sampling is facilitated for the latter two by the use of pivot algorithms, which allow simulations of literally thousands of monomers. Electrostatic interactions are treated within the primitive model. There are no interactions between macromolecules; only single chain properties are investigated.



The main part of the thesis is devoted to the study of flexible polyelectrolytes, which represent systems like polyacrylic acid and polyglutamic acid. The apparent dissociation constant and the end-to-end separation are calculated for varying degree of dissociation, bond length/bond strength, number of monomers and salt concentration. Simple scaling relations obtained by a Flory type approach are investigated as well as the results of more elaborate variational calculations using a Gaussian Ansatz where all interactions are modelled by harmonic springs. Various rigid models that have appeared in the literature are also examined.



The last part of the thesis deals with integral equation theory in the form of RISM-MSA for proteins and other more or less rigid polyelectrolytes. The theory is applied to the calcium binding and titrational behaviour of the protein calbindin D9k. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Prof. Joanny, Jean-Francois, Institut Charles Sadron, Strasbourg, France
organization
publishing date
type
Thesis
publication status
published
subject
keywords
integral equation theory, variational calculations, Monte Carlo simulations, end-to-end separation, apparent dissociation constant, titrating polyelectrolytes, electrostatic interactions, Physical chemistry, Fysikalisk kemi
pages
69 pages
publisher
Biophysical Chemistry (LTH), Lund University
defense location
Lecture hall F, Chemical Center
defense date
1996-03-08 14:15
external identifiers
  • Other:ISRN: LUTKDH/TKFK-1003-1996-SE
ISBN
91-628-1934-8
language
English
LU publication?
yes
id
c67f48ce-52c2-44df-b4c8-618f3b4cf882 (old id 28237)
date added to LUP
2007-06-11 14:35:36
date last changed
2016-09-19 08:45:10
@misc{c67f48ce-52c2-44df-b4c8-618f3b4cf882,
  abstract     = {Different models and statistical mechanical approximations for titrating polyelectrolytes are studied and the results compared with Monte Carlo simulations and experimental data. Three types of models have been used in the simulations: i) rigid structures and freely jointed chains with ii) rigid bonds and iii) flexible, harmonic bonds. Sampling is facilitated for the latter two by the use of pivot algorithms, which allow simulations of literally thousands of monomers. Electrostatic interactions are treated within the primitive model. There are no interactions between macromolecules; only single chain properties are investigated.<br/><br>
<br/><br>
The main part of the thesis is devoted to the study of flexible polyelectrolytes, which represent systems like polyacrylic acid and polyglutamic acid. The apparent dissociation constant and the end-to-end separation are calculated for varying degree of dissociation, bond length/bond strength, number of monomers and salt concentration. Simple scaling relations obtained by a Flory type approach are investigated as well as the results of more elaborate variational calculations using a Gaussian Ansatz where all interactions are modelled by harmonic springs. Various rigid models that have appeared in the literature are also examined.<br/><br>
<br/><br>
The last part of the thesis deals with integral equation theory in the form of RISM-MSA for proteins and other more or less rigid polyelectrolytes. The theory is applied to the calcium binding and titrational behaviour of the protein calbindin D9k.},
  author       = {Ullner, Magnus},
  isbn         = {91-628-1934-8},
  keyword      = {integral equation theory,variational calculations,Monte Carlo simulations,end-to-end separation,apparent dissociation constant,titrating polyelectrolytes,electrostatic interactions,Physical chemistry,Fysikalisk kemi},
  language     = {eng},
  pages        = {69},
  publisher    = {ARRAY(0xa1d6d28)},
  title        = {Statistical Mechanical Studies of Titrating Polyelectrolytes},
  year         = {1996},
}