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Probing Dynamics of Oligosaccharides by Interference Phenomena in NMR Relaxation
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
Responsible organisation
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Oligosaccharides (carbohydrates) are a large class of biological molecules that are important as energy sources in the human body and have enormously varied biological functions. It is generally believed that biological activities of carbohydrates are related to their internal dynamics. The dynamic properties of some oligosaccharides in solution are studied in this thesis, by NMR relaxation. We have employed relaxation interference effects to investigate the conformational dynamics within oligosaccharides (in-tramolecular dynamics) and paramagnetic relaxation enhancement (PRE) as an experimental tool to study intermolecular dynamics. Most of the thesis concerns the dynamics of the methylene group in the two possibly mobile parts of the oligosaccharide: in the exocyclic hydroxymethyl moiety and in the glycosidic linkage position. To perform conformational dynamic studies, the more traditional auto-relaxation pa-rameters are combined with the relaxation interference terms or the cross-correlated relaxation rates (CCRRs). Some experimental schemes based on the initial-rate technique were developed for measuring CCRRs. The techniques are useful for labelled sugars as well as naturally abundant ones. Furthermore, various dynamical models ranging from the Lipari–Szabo approach to several more informative and complicated models such as the two-site jump model, restricted internal rotation and slowly relaxing local structure (SRLS), have been employed to interpret our experimental data. We have combined and com-pared different models; we have also developed a novel approach to existing models, by scaling dipolar coupling constants (DCC), to extract the dynamic behaviour and structural properties of the system. We found that the auto- and cross-correlated relaxation data analyses yield a consistent picture of the dynam-ics in all cases. Additionally, our investigations show that CCRRs are practically important for verifica-tion of certain dynamical and structural information that is difficult to be determined by other means. Moreover, the anisotropy of the carbon-13 chemical shielding tensor in the methylene group has been estimated, using the interference between dipole-dipole and chemical shift anisotropy.

This thesis also discusses using the PRE to investigate sugar dynamics relative to a paramagnetic MRI contrast agent in solution, which might be important in medicine. We have studied the intramolecu-lar dynamics of the trisaccharide raffinose in the presence of a gadolinium complex. We also investigated the effect of translational diffusion instead of rotational diffusion, which is normally more important in NMR. The paramagnetically enhanced spin–lattice relaxation rates of aqueous protons over a wide range of magnetic fields and of carbon-13 and protons of the sugar at high fields have been measured. The nuclear magnetic relaxation dispersion of water protons and the PREs of proton and carbon in the sugar are interpreted in terms of the model recently developed in our laboratory, allowing both outer- and inner-sphere PREs for water protons, but allowing only the outer sphere PRE for nuclei in the sugar. We found that the relative diffusion has a stronger effect on the PRE than the electron spin relaxation.

Place, publisher, year, edition, pages
Stockholm: Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi , 2008. , 73 p.
Keyword [en]
NMR, sugars, oligosaccharides, carbon-13 relaxation, cross-correlated relaxation, molecular dynamics, internal motion, random jumps, PRE, paramagnetic relaxation
National Category
Other Basic Medicine
Research subject
Physical Chemistry
Identifiers
URN: urn:nbn:se:su:diva-8211ISBN: 978-91-7155-714-8 (print)OAI: oai:DiVA.org:su-8211DiVA: diva2:199815
Public defence
2008-09-12, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 10:00
Opponent
Supervisors
Available from: 2008-09-18 Created: 2008-09-18Bibliographically approved
List of papers
1. Internal dynamics of hydroxymethyl rotation from CH2 crosscorrelation in methyl-β-glucopyranoside
Open this publication in new window or tab >>Internal dynamics of hydroxymethyl rotation from CH2 crosscorrelation in methyl-β-glucopyranoside
Show others...
2004 In: Journal of Magnetic Resonance, ISSN 1090-7807, Vol. 167, no 2, 273-281 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25478 (URN)
Note
Part of urn:nbn:se:su:diva-8211Available from: 2008-09-18 Created: 2008-09-18Bibliographically approved
2. Cross-correlated and conventional dipolar carbon-13 relaxation in methylene groups in small, symmetric molecules
Open this publication in new window or tab >>Cross-correlated and conventional dipolar carbon-13 relaxation in methylene groups in small, symmetric molecules
2007 In: Concepts in Magnetic Resonance, Part A: Bridging Education and Research, ISSN 1546-6086, Vol. 30A, no 2, 100-115 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25479 (URN)000245073900003 ()
Note
Part of urn:nbn:se:su:diva-8211Available from: 2008-09-18 Created: 2008-09-18Bibliographically approved
3. NMR relaxation interference effects and internal dynamics in γ-cyclodextrin
Open this publication in new window or tab >>NMR relaxation interference effects and internal dynamics in γ-cyclodextrin
2008 (English)In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 195, no 1, 1-8 p.Article in journal (Refereed) Published
Abstract [en]

Multiple-magnetic field (9.4, 14.1 and 21.1 T) measurements of 13C spin–lattice and spin–spin relaxation rates, the heteronuclear Overhauser enhancement and cross-correlated relaxation rates (CCRRs) in the methylene groups are reported for γ-cyclodextrin in water/dimethylsulfoxide solution at 323 and 343 K. The CCRRs are obtained from differences in the initial relaxation rates of the components of the CH2 triplet in the 13C spectra. The relaxation data are analyzed using the Lipari–Szabo approach and a novel modification of the two-site jump model. According to the latter model, inclusion of the dipolar (CH,CH) cross-correlated longitudinal and transverse relaxation is important for estimating the rate of the conformational jumps in the hydroxymethyl group. Using the dynamic information from the jump model, we have also used the differences in the initial relaxation rates for the triplet components to estimate the anisotropy of the chemical shielding tensor.

Keyword
Carbon-13 relaxation, Cross-correlated relaxation, Molecular dynamics, Internal motion, Random jumps
National Category
Environmental Sciences
Identifiers
urn:nbn:se:su:diva-25480 (URN)10.1016/j.jmr.2008.07.025 (DOI)000260398000001 ()
Available from: 2008-09-18 Created: 2008-09-18 Last updated: 2017-12-13Bibliographically approved
4. NMR relaxation study of the motional dynamics of methylene groups in oligosaccharides by applying Slowly Relaxing Local Structure model
Open this publication in new window or tab >>NMR relaxation study of the motional dynamics of methylene groups in oligosaccharides by applying Slowly Relaxing Local Structure model
Show others...
Manuscript (Other academic)
Identifiers
urn:nbn:se:su:diva-25481 (URN)
Note
Part of urn:nbn:se:su:diva-8211Available from: 2008-09-18 Created: 2008-09-18 Last updated: 2010-01-13Bibliographically approved
5. Nuclear spin relaxation study of aqueous raffinose solution in the presence of a gadolinium contrast agent
Open this publication in new window or tab >>Nuclear spin relaxation study of aqueous raffinose solution in the presence of a gadolinium contrast agent
2005 In: Magnetic Resonance in Chemistry, ISSN 0749-1581, Vol. 43, no 3, 235-239 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25482 (URN)
Note
Part of urn:nbn:se:su:diva-8211Available from: 2008-09-18 Created: 2008-09-18Bibliographically approved

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