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NMR Research Group
Seminars

 

Seminars 2003

The weekly seminar of the NMR group, held at Fridays in the spectroscopy coffee room, FY216, at 14.00, is open for everyone interested. Coffee, bakings and the latest research of the group!

 

7.2. Susanna Ahola
Experimental determination of the 2H quadrupole coupling constant in deuterated benzenes

14.2 Jussi Soukkamäki
Characterization and Use of Bragg Gratings in Optical Communications

28.2 Jukka Jokisaari
NMR properties of carbon diselenide

Abstract:
Properties of the carbon diselenide (CSe2) molecule have been studied in our group by applying various experimental NMR techniques and calculation methods. The 13C and 77Se shielding tensor anisotropies were determined by liquid crystal NMR and T1 measurements at variable magnetic fields. These properties have also been computed. The secondary isotope effects on the 13C and 77Se shielding were also investigated both experimentally and theoretically. Recently, the anisotropies of the 13C-77Se and 77Se-77Se spin-spin coupling tensors were calculated by ZORA DFT and analysed from the corresponding experimental anisotropic (D) couplings. The talk will summarize the results.

7.3. Harri Koskela
Experimental determination of heteronuclear long-range coupling constants

Abstract:
The relation between three-bond coupling constant and torsional angle can be described by Karplus equation. Thus the knowledge of long-range couplings is vital in conformational studies of a molecule structure. A couple of methods to acquire heteronuclear long-range coupling information are discussed.

14.3. Juhani Lounila
EFFECTS OF INTERNAL MOTIONS ON RESIDUAL DIPOLAR COUPLINGS OF A PROTEIN

Abstract:
So-called residual dipolar couplings currently gain increasing interest for structure determination of dissolved biomolecules such as proteins. These couplings can be observed in NMR spectra if the molecules in solution exhibit a partial alignment leading to an incomplete averaging of anisotropic magnetic dipole-dipole interactions.

Interest has primarily been focused on structural applications, because the long-range orientational constraints derived from the residual dipolar couplings complement the short-range constraints typically obtained from other data such as NOEs. However, dipolar couplings are sensitive to internal motions spanning a wide range of time scales and, thus, can potentially serve as valuable probes of biologically relevant motions. Moreover, in order to extract reliable structural information from the dipolar data, the effects of the internal motions should be known. Most of the existing structure refinement protocols for analysing dipolar couplings implicitly assume that internal motions are either absent, negligibly small, or uniform and axially symmetric in nature. Studies of small molecules in liquid crystals have shown that these are generally not good approximations.

In this talk, the effect of internal motions on observed residual dipolar couplings is discussed with an application to the well-studied protein ubiquitin.

4.4. Tuomas Koskela
129Xe lineshape limiting cases of adsorbed xenon in aluminophosphate molecular sieves

Abstract:
The shielding of 129Xe in nanochannels of various dimensions and shapes is studied and predictions of lineshapes resulting from anisotropic averaging of the shielding tensor in various limiting cases of nanochannels are made, based on ab initio calculations of shielding surfaces. The predictions are made for various cross-sections, Xe loadings, and at variable temperatures. The talk will compare original results done by Jameson and de Dios to experimental observations with aluminophosphate molecular sieves.

11.4. Jani Saunavaara
Investigation of the 10B1M7 Liquid Crystal

Abstract:
10B1M7 liquid crystal has ferro-, ferri-, and antiferroelectric phases. Previously 1H, 2H and 13C NMR spectroscopies have been employed to study the structure and the dynamics of this smectic liquid crystal. Now we have applied 129Xe NMR to investigate its properties.

16.4. Pekka Manninen
Magnetic field dependence of NMR shielding in closed-shell atoms and molecules

Abstract:
In 1970, Ramsey proposed the dependence of the nuclear magnetic shielding on, to the leading order, the square of the external magnetic field. Bendall and Doddrell measured the field dependence of Co-57 nuclear magnetic shielding and found, in two compounds, an increased chemical shift (decreased shielding) at higher field. A response theory formulation for the magnetic field-dependence of nuclear magnetic shielding is presented for closed-shell atoms and molecules, based on a nonrelativistic reference state. Under particular interest are the Co-57 -complexes, for which the experimental observation of field-dependent shielding was made. Calculations are carried out for the field-dependence coefficient using SCF and correlated MCSCF wave functions as well as DFT to provide the reference state for linear and nonlinear response theories.

25.4. Jochen Autschbach
Relativistic density functional computations of NMR parameters on heavy atom systems

Abstract:
Recent years have seen very active research acvities devoted to the calculation of NMR parameters of heavy nuclei in molecules. We will give a concise overview of the available methodology and present our density functional approach based on the two-component relativistic ZORA Hamiltonian. A number of applications, in particular to spin-spin coupling constants involving heavy nuclei, will be presented. Emphasis will be put on environmental effects (coordination, solvent) and their important consequences for even a qualitatively correct understanding of experimental data for metal complexes. NMR chemical shifts and shielding anisotropies will also be discussed.

9.5. Ville-Veikko Telkki
The freezing and melting phenomena of acetonitrile confined in mesoporous silica gels as studied by 129Xe NMR

16.5. Matti Hanni
Calculations of the second virial coefficient of gas-phase 129Xe shielding

Abstract:
The second virial coefficient of gas-phase 129Xe shielding is calculated as a function of temperature and compared to both experimental and theoretical results. Both experimental and theoretical interatomic potentials are used in the calculation of the second virial coefficient. The results are found to be strongly dependent on the shape of interatomic potential function used in the calculation. A more accurate theoretical interatomic potential is attained by introducing effective core potentials (ECPs) in energy calculations with the coupled cluster singles and doubles with non-iterative triples (CCSD(T)) theory. Other potential reasons for the discrepancy between experimental and theoretical results of second virial coefficient are considered.

23.5. Teemu Pennanen
Calculations of oxygen and proton gas-to-liquid shifts for water

Abstract:
Gas-to-liquid shift is a difference between the shielding constant of a gaseous phase and the shielding constant in a liquid phase. It's calculational determination not only requires a treatment for a single molecule without an environment, which represents the gas phase, but also a treatment for a molecule surrounded by other similar molecules, which is the case in the liquid phase. Thus the environmental effects play an important role and the results depend drastically on the ability of modelling these so called solvent effects. In the presentation the strategy of taking the solvent effects into account is considered and the results of the gas-to-liquid shifts are provided.

19.9. Jukka Jokisaari
15N CSA in proteins

Abstract:
15N CSA in proteins will be discussed in the light of a few recently appeared articles. Methods for the determination of 15N CSA as well as its application to the protein structure refinement are brought forth.

26.9. Juhani Lounila
Hyperpolarized NMR in solution at room temperature

Abstract:
Very recently, a novel method for obtaining strongly polarized nuclear spins in solution has been introduced. For a number of different molecules, it allows an increase in signal-to-noise ratio by more than 10 000 times. This method is discussed in the seminar talk.

3.10. Jukka Jokisaari
NMR of atoms and small molecules trapped in cryptophane-A

Abstract:
The cavity volume of practically spherical cryptophane-A is ca. 95 c. Thus it is possible to introduce atoms, such as xenon, or small molecules, such as methane and chloroform, into this volume. The lecture will deal with what kind of information can be derived about the system through the NMR of trapped atoms and molecules.

10.10. Jani Saunavaara
129Xe diffusion in 10B1M7 Liquid Crystal

Abstract:
Diffusion studies are a valuable source of information on molecular organization and phase structure. NMR methods for studying diffusion and the results of 129Xe self-diffusion experiments in 10B1M7 LC are introduced.

16.10. Jyrki Ruohonen NB Thu at 3 p.m.
Diffusion MRI

Abstract:
During the last years diffusion magnetic resonance imaging (MRI) has become an important tool not only in the research work but also in the diagnostic MRI. This talk will shortly introduce the basic principles of diffusion MRI. The basic pulse sequences for diffusion weighted imaging, the calculation of the diffusion image and some applications of the diffusion MRI in diagnostic work- up will be presented.

23.10. Pekka Manninen NB Thu at 2 p.m.
Completeness-optimized basis sets: A cost-effective way to the CBS limit in quantum chemical calculations

Abstract:
Of the general features limiting the accuracy of the quantum chemical methods the choice of one-particle basis is perhaps the most important resolution in setting up a calculation. A competence of a basis set in calculation of molecular magnetic properties - indirect spin-spin coupling, nuclear magnetic shielding, and magnetizability - is evaluated with ab initio calculations and completeness profiles. New, completeness-optimized exponent sets designed for pronounced properties are introduced. It turns out that with these basis sets, it is possible to reach the complete basis set (CBS) limit with one-fifth of amount of basis functions as compared to the unoptimized basis set.

31.10. Matti Hanni
Ground state potential energy curves for rare gas dimer Xe2

Abstract:
Basic principles for deriving theoretical potential energy curves (PECs) are discussed in context with non-relativistic and pseudopotential approaches. Some early models for potential functions of diatomic species are shown. Typical sources of error in PEC are listed. A comparison of selected ground state PECs for rare gas dimer Xe2 is done via equilibrium distance Re and well depth De. A couple of PECs are presented as a function for interatomic distance for qualitative discussion.

7.11. Anu Kantola
Methods of measuring CH-couplings in liquid crystals

Abstract:
Dipolar couplings can be utilised to obtain information about the stucture and dynamics of liquid crystals. However, because of the complexity of the spectra it is impossible to measure these couplings with traditional methods. The scope of this talk is to give an insight into the NMR methods that make it possible to receive information about the CH-couplings in anisotropic samples.

14.11. Juhani Lounila
The origin of dipolar couplings from denatured proteins

Abstract:
A number of treatments can cause proteins to unfold by disrupting the weak bonds that hold a protein together. When this happens, the protein is said to be denatured. Even a small protein has an astronomical number of configurations it can adopt when unfolded, and the ensemble of conformations is expected to converge toward those of a statistical random coil. Hence, when a protein unfolds in an anisotropic environment, its net alignment is expected to vanish. However, recent experiments have demonstrated that the residual dipolar couplings of denatured proteins are not lost. The origin of these dipolar couplings is discussed in the seminar talk.

21.11. Ville Telkki
New methods to get at the pore sizes 129Xe NMR studies

Abstract:
The samples containing mesoporous materials, different liquids or liquid crystals, and xenon gas have been studied by 129Xe NMR spectroscopy. The aim of the investigations has been to find new correlations between the pore size and behavior of the signals. The results will be presented in the talk and the usefulness of the found correlations will be discussed.

28.11. Teemu Pennanen
Results and Discussion on the Combined Molecular Dynamics and Quantum Chemical Study of Water: Nuclear magnetic shielding and quadrupole coupling tensors.

5.12. Perttu Lantto
Relativistic heavy atom effect in heavy atom shielding (HAHA) in XH3- (X = C, Si, Ge, Sn, Pb)

Abstract:
The effects of relativity has to be taken into account in theoretical calculations of NMR observables, such as nuclear shielding tensors, already for fairly light elements. The heavy atom effect on the shielding of the heavy atom itself (HAHA) is due to many reasons, particularly the ``active'' second-order cross-term of the Fermi contact interaction and the kinetic energy correction to the spin-Zeeman interaction (FC/SZ-KE). In the talk, the molecular orbital origin of the HAHA effect is discussed.

12.12. Hannu Luukinen
Drawing NMR pulse sequence diagrams with computer

Abstract:
A novel program is made to help to draw NMR pulse sequences for publications and for teaching. Also the program is one effort to standardisize pulse diagrams. The interface of program is graphical and secuences drawn with program can be exported in binary format or in scalable EPS-format.

 

 

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