Petri Ingman

1H NMR metabonomics approach to the disease continuum of diabetic complications and premature death

Subtle metabolic changes precede and accompany chronic vascular complications, which are the primary causes of premature death in diabetes. To obtain a multimetabolite characterization of these high‐risk individuals, we measured proton nuclear magnetic resonance (1H NMR) data from the serum of 613 patients with type I diabetes and a diverse spread of complications. We developed a new metabonomics framework to visualize and interpret the data and to link the metabolic profiles to the underlying diagnostic and biochemical variables. Our results indicate complex interactions between diabetic kidney disease, insulin resistance and the metabolic syndrome. We illustrate how a single 1H NMR protocol is able to identify the polydiagnostic metabolite manifold of type I diabetes and how its alterations translate to clinical phenotypes, clustering of micro‐ and macrovascular complications, and mortality during several years of follow‐up. This work demonstrates the diffuse nature of complex vascular diseases and the limitations of single diagnostic biomarkers. However, it also promises cost‐effective solutions through high‐throughput analytics and advanced computational methods, as applied here in a case that is representative of the real clinical situation.

A novel Bayesian approach to quantify clinical variables and to determine their spectroscopic counterparts in 1H NMR metabonomic data

BackgroundA key challenge in metabonomics is to uncover quantitative associations between multidimensional spectroscopic data and biochemical measures used for disease risk assessment and diagnostics. Here we focus on clinically relevant estimation of lipoprotein lipids by 1H NMR spectroscopy of serum.ResultsA Bayesian methodology, with a biochemical motivation, is presented for a real 1H NMR metabonomics data set of 75 serum samples. Lipoprotein lipid concentrations were independently obtained for these samples via ultracentrifugation and specific biochemical assays. The Bayesian models were constructed by Markov chain Monte Carlo (MCMC) and they showed remarkably good quantitative performance, the predictive R-values being 0.985 for the very low density lipoprotein triglycerides (VLDL-TG), 0.787 for the intermediate, 0.943 for the low, and 0.933 for the high density lipoprotein cholesterol (IDL-C, LDL-C and HDL-C, respectively). The modelling produced a kernel-based reformulation of the data, the parameters of which coincided with the well-known biochemical characteristics of the 1H NMR spectra; particularly for VLDL-TG and HDL-C the Bayesian methodology was able to clearly identify the most characteristic resonances within the heavily overlapping information in the spectra. For IDL-C and LDL-C the resulting model kernels were more complex than those for VLDL-TG and HDL-C, probably reflecting the severe overlap of the IDL and LDL resonances in the 1H NMR spectra.ConclusionThe systematic use of Bayesian MCMC analysis is computationally demanding. Nevertheless, the combination of high-quality quantification and the biochemical rationale of the resulting models is expected to be useful in the field of metabonomics.

NMR Studies of Carbosilane Dendrimer with Terminal Mesogenic Groups

The 4-generation carbosilane dendrimer with terminal cyanobiphenyl mesogenic groups in dilute solution of CDCl(3) was investigated using (1)H NMR technique. The spectrum was obtained and the relaxation time, T(1), was measured in the temperature range 320-225 K. For the first time, the extrema of T(1) values were achieved for majority of the dendrimer functional groups. The values of activation energies of the dendrimer functional groups were obtained. The relaxation data for outer and inner methyl groups show that the dendrimer investigated has dense corona and hollow core. This structure is formed because the mesogenic groups do not allow terminal segments to penetrate into the dendrimer, that is, the backfolding effect is absent. The NMR spectral and relaxation data give evidence for changing conformation of the dendrimer internal segments with decreasing temperature. This reorganization is most likely connected with a change of dendrimer size. We suppose that our experimental results will provide additional information for understanding principles of dendrimer nanocontainer operation. NMR can possibly be a tool for indicating the encapsulation effect as well as the dendrimer effective size.

Average relaxation time of internal spectrum for carbosilane dendrimers: Nuclear magnetic resonance studies

A new theoretical description of the interior mobility of carbosilane dendrimers has been tested. Experiments were conducted using measurements of the (1)H NMR spin-lattice relaxation time, T(1H), of two-, three- and four-generation carbosilane dendrimers with three different types of terminal groups in dilute chloroform solutions. Temperature dependences of the NMR relaxation rate, 1/T(1H), were obtained for the internal CH(2)-groups of the dendrimers in the range of 1/T(1H) maximum, allowing us to directly evaluate the average time of the internal spectrum for each dendrimer. It was found that the temperature of 1/T(1H) maximum is practically independent of the number of generations, G; therefore, the theoretical prediction was confirmed experimentally. In addition, the average time of the internal spectrum of carbosilane dendrimers was found to be near 0.2 ns at room temperature, and this value correlates well with the values previously obtained for other dendrimer structures using other experimental techniques.

Non-Spherical Ion Dynamics and Rotational Diffusion for Imidazolium Based Ionic Liquids

While liquid electrolyte salts, comprised predominantly of ions and ion pairs, were studied already in the early half of the 1800s (see for example papers by Faraday or Hittorf), modern advancements of ionic materials have given rise to various combinations resulting in liquid phases at convenient temperatures. For this reason, a “renewed” interest in ionic liquids (ILs) has exploded worldwide, with hopes to solve problems of interest to the industrial chemistry community. Furthermore, it emerges that their unique physical properties lead to challenging solvation characteristics, ultimately the result of complex reorientational ion dynamics. Of fundamental importance to understanding the solvation properties of liquids, aside from enlightening dielectric relaxation studies, are nuclear spin dynamics, obtained using experimental NMR relaxation techniques. In this context, the nuclear spin is allowed to return to its equilibrium magnetisation (i.e. relaxation occurs) after being disturbed by an externally applied radiofrequency (rf) magnetic field. Experiments yield selective information regarding the rotational dynamics of the assembly containing the nuclei of interest because the return to equilibrium is governed by the assembly’s reorientational motion. For a C nucleus in a planar asymmetric skeleton, such as ring carbons comprising any imidazolium based IL, two sources of relaxation must be considered: that due to dipole–dipole (DD) interactions and that due to the chemical shift anisotropy (CSA). We present here C T1 (longitudinal or spin–lattice) relaxation data across two different magnetic fields, for 3-methyl-1Himidazolium bromide, [Hmim]Br. We found the so-called “extreme narrowing” motional regime clearly applies for this IL, greatly simplifying the subsequent theoretical treatments. These data were further used to develop a simple analytical procedure to determine the diagonalised rotational diffusion tensor, which depends upon ionic reorientation, as described below. The rotational diffusion constants obtained describe all ionic reorientational motion of the [Hmim] cation. In this way, the view of ionic rotational reorientation extends beyond that of the idealised isotropic rotor towards that based on the “nonideal” anisotropic tumbler. In recent years, literature reports focusing on ion spin dynamics for imidazolium based ILs have become more commonplace; however, the accompanying theoretical treatments often employ simplifying assumptions. In this context, anisotropic tumblers (which all imidazolium cations are) have been assumed to exhibit isotropic motional characteristics, where accompanying theoretical treatments generally make exclusive use of idealised spherical approximations. In this way, issues arising from the fact that non-spherical rotors possess two or more non-equivalent symmetry planes, where reorientations are described by a variety of non-equivalent motion, have in general been neglected. The associated errors are especially apparent in view of relations describing the correlation time constants derived from the required Hamiltonian, in the context of rotational diffusion. For a comparison of the correlation time, t2, (associated with a rank two tensor) required for description of spherical rotors, with that of symmetric rotors, of any given axial symmetry, see Scheme 1 [Eqs. (1) and (2)]:

Unexpected Temperature Behavior of Polyethylene Glycol Spacers in Copolymer Dendrimers in Chloroform.

We have studied copolymer dendrimer structure: carbosilane dendrimers with terminal phenylbenzoate mesogenic groups attached by poly(ethylene) glycol (PEG) spacers. In this system PEG spacers are additional tuning to usual copolymer structure: dendrimer with terminal mesogenic groups. The dendrimer macromolecules were investigated in a dilute chloroform solution by 1H NMR methods (spectra and relaxations). It was found that the PEG layer in G = 5 generations dendrimer is “frozen” at high temperatures (above 260 K), but it unexpectedly becomes “unfrozen” at temperatures below 250 K (i.e., melting when cooling). The transition between these two states occurs within a small temperature range (~10 K). Such a behavior is not observed for smaller dendrimer generations (G = 1 and 3). This effect is likely related to the low critical solution temperature (LCST) of PEG and is caused by dendrimer conformations, in which the PEG group concentration in the layer increases with growing G. We suppose that the unusual behavior of PEG fragments in dendrimers will be interesting for practical applications such as nanocontainers or nanoreactors.

Molecular mobility of counterion functional groups in ionic liquid 1-ethyl-3-methylimidazolium acetate according to 1H and 13C NMR relaxation data

Abstract1-Ethyl-3-methylimidazolium acetate was studied by NMR relaxation. The temperature dependences of the spin-lattice relaxation rates (1/T1) for 1H and 13C were obtained. The curves with maxima were observed for the majority of the temperature dependences 1/T1, which provided a reliable temperature dependence of the correlation times (τc). In the low-temperature range, the proton relaxation rates tend to an asymptotic value, which is related, most likely, to spin diffusion manifested in the studied samples. The values of correlation times τc calculated for 1H and 13C of the same functional group almost coincide at high temperatures, which confirms that the used approach is adequate for the determination of characteristic times of rotational reorientation of counterions in the studied ionic liquid.

Composition of Ni2+ cation solvation shell in NiCl2–methanol solution by multinuclear NMR

1H-, 2H- and 13C-NMR spectra have been used to test the Ni2+ solvation shell composition in the 1.1 molal methanol solution of NiCl2. It has been confirmed that Cl− anion takes part in the nearest environment of Ni2+ cation at all the temperatures investigated. Using 2H-NMR allowed us to detect for the first time OD-signal of methanol in the primary solvation shell of Ni2+ cation. Both 2H- and 13C-NMR spectra show that the composition of the cation solvation shell becomes more complicated at temperatures lower than 220 K.