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Complexing Cations by Polyethylene Oxide. Binding Site and Binding Mode
KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.ORCID-id: 0000-0002-0231-3970
2017 (Engelska)Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207Artikel i tidskrift (Refereegranskat) In press
Ort, förlag, år, upplaga, sidor
2017.
Nationell ämneskategori
Fysikalisk kemi
Forskningsämne
Kemi
Identifikatorer
URN: urn:nbn:se:kth:diva-201731OAI: oai:DiVA.org:kth-201731DiVA, id: diva2:1074683
Anmärkning

QCR 20170216

Tillgänglig från: 2017-02-15 Skapad: 2017-02-15 Senast uppdaterad: 2017-11-29Bibliografiskt granskad
Ingår i avhandling
1. Ions interacting with macromolecules: NMR studies in solution
Öppna denna publikation i ny flik eller fönster >>Ions interacting with macromolecules: NMR studies in solution
2017 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Specific ion effects, identified for more than hundred years, play an important role in a wide range of phenomena and applications. Several mechanisms such as direct ion interaction with molecules have been suggested to explain these effects, but quantitative experimental evidence remains scarce. Electrophoretic NMR (eNMR) has been emerging as a very powerful tool for studying molecular association and ionic transport in a variety of systems. Yet its potential in studying specific ion effect has been unexplored. In this thesis, eNMR was in part developed further as an analytical method and was in part used as one of the main techniques to study ions interacting with macromolecules in aqueous and non-aqueous solutions.

The complexation of a large group of cations with poly ethylene oxide (PEO) in methanol was studied with eNMR. The binding of monovalent ions was demonstrated not to follow the Hofmeister order; multivalent cations except barium all showed negligible complexation. As a unifying feature, only cations with surface charge density below a threshold value were able to bind suggesting that ion solvation is critical. The binding mechanism was examined in greater detail for K+ and Ba2+ with oligomeric PEO of different chain lengths. Those two cations exhibited different binding mechanisms. K+ was found to bind to PEO by having at least 6 repeating units wrap around it while retaining the polymer flexibility. On the other hand, Ba2+ (and, to some extent, (BaAnion)+) needs a slightly shorter section to bind, but the molecular dynamics at the binding site slow considerably.

The binding of anions with poly (N-isopropylacrylamide) in water was quantified at low salt concentration with eNMR and the binding affinity, though very weak, followed the Hofmeister order. This result indicates the non-electrostatic nature of this specific ion effects. The increase of binding strength with salt concentration is well described by a Langmuir isotherm.

The specific ion binding to a protein, bovine serum albumin (BSA), was also studied at pH values where BSA has either net positive and negative charges. Our results show that anions have the same binding affinity irrespective of the surface charge while the binding strength of cations is reversed with the change in net surface charge. This indicates different binding mechanisms for cations and anions.

The ionization of cellobiose in alkaline solutions was measured quantitatively by eNMR. The results show a two-step deprotonation process with increasing alkaline strength. Supported by results from 1H-13C HSQC NMR and MD simulation, ionization was proposed to be responsible for the improved solubility of cellulose in alkaline solution. eNMR was also used to characterize the effective charge of tetramethylammonium ions in a variety of solvents. In solvents of high polarity, the results agree well with predictions based on Onsager’s limiting law but for nonpolar solvents deviations were found that were attributed to ion pair formation. 

Ort, förlag, år, upplaga, sidor
KTH Royal Institute of Technology, 2017. s. 61
Serie
TRITA-CHE-Report, ISSN 1654-1081 ; 2017 : 12
Nyckelord
electrophoretic NMR, diffusion NMR, specific ion effects, Hofmeister, ion binding
Nationell ämneskategori
Fysikalisk kemi
Forskningsämne
Kemi
Identifikatorer
urn:nbn:se:kth:diva-201732 (URN)978-91-7729-282-1 (ISBN)
Disputation
2017-03-22, F3, Lindstedtsvägen 26, Stockholm, 10:00 (Engelska)
Opponent
Handledare
Anmärkning

QC 20170216

Tillgänglig från: 2017-02-16 Skapad: 2017-02-15 Senast uppdaterad: 2017-05-30Bibliografiskt granskad

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