High-Resolution Probing of Heterogeneous Samples by Spatially Selective Pure Shift NMR Spectroscopy.

Liquid NMR spectroscopy generally encounters two major challenges for high-resolution measurements of heterogeneous samples, namely, magnetic field inhomogeneity caused by spatial variations in magnetic susceptibility and spectral congestion induced by crowded NMR resonances. In this study, we demonstrate a spatially selective pure shift NMR approach for high-resolution probing of heterogeneous samples by suppressing effects of field inhomogeneity and J coupling simultaneously. A Fourier phase encoding strategy is proposed and implemented for spatially selective pure shift experiments to enhance signal intensity and further boost the applicability. The spatially selective pure shift method can serve as an effective tool for high-resolution probing of heterogeneous samples, thus presenting interesting prospects for extensive applications in the fields of chemistry, physics, biology, and food science

Fat and water signals in nuclear magnetic resonance imaging

This thesis is intended to explore fat and water differentiation in nuclear magnetic resonance imaging. The need to create separate fat and water images is discussed and a critical review of current practices in the field is presented. These techniques include chemical shift imaging, coupled spin mapping and methods based on relaxation time differences. As an extension of this review, alternative slice cycling procedures are proposed that afford an improvement in the conventional chemical shift selective presaturation sequence. A new, hybrid fat or water suppression sequence is studied in detail, including a theoretical description of the role of the sequence parameters, as well as direct experimental comparison with its most closely related conventional fat and water differentiation techniques. The proposed scheme is shown to be robust in normal use and more tolerant than the conventional methods to mis-settings of experimental parameters. In vivo demonstration of the method is also performed. Further work involves the generation of differential fat and water relaxation time maps. A critical review of current, conventional techniques that allow production of longitudinal relaxation calculated images is presented. Novel pulse sequence schemes for the measurement of fat and water longitudinal relaxation times are described, and the accuracy of these measurements is evaluated using phantoms. The results obtained are also being compared with conventional spectroscopic and imaging methods

Automated Analysis of Quantitative NMR Spectra

NMR spectroscopy is an invaluable tool for structure elucidation in chemistry and molecular biology, which is able to provide unique information not easily obtained by other analytical methods. However, performing quantitative NMR experiments and mixture analysis is considerably less common due to constraints in sensitivity/resolution and the fact that NMR observes individual nuclei, not molecules. The advances in instrument design in the last 25 years have substantially increased the sensitivity of NMR spectrometers, diminishing the main weakness of NMR, while increases in field strength and ever more intricate experiments have improved the resolving power and expanded the attainable information. The minimal need for sample preparation and its non-specific nature make quantitative NMR suitable for many applications ranging from quality control to metabolome characterization. Furthermore, the development of automated sample changers and fully automated acquisition have made high-throughput NMR acquisition a more feasible and attractive, yet expensive, possibility. This work discusses the fundamental principles and limitations of quantitative liquid state NMR spectroscopy, and tries to put together a summary of its various aspects scattered across literature. Many of these more subtle features can be neglected in simple routine spectroscopy, but become important when extracting quantitative data and/or when trying to acquire and process vast amounts of spectra consistently. The original research presented in this thesis provides improved methods for data acquisition of quantitative 13C detected NMR spectra in the form of modified INEPT based experiments (Q-INEPT-CT and Q-INEPT-2D), while software tools for automated processing and analysis of NMR spectra are also presented (ImatraNMR and SimpeleNMR). The application of these tools is demonstrated in the analysis of complex hydrocarbon mixtures (base oils), plant extracts and blood plasma samples. The increased capability of NMR spectroscopy, the rising interest in metabolomics and for example the recent introduction of benchtop NMR spectrometers are likely to expand the future use of quantitative NMR in the analysis of complex mixtures. For this reason, the further development of robust, accurate and feasible analysis methods and tools is essential.NMR-spektroskopia on keskeinen mm. kemiassa ja molekyylibiologiassa käytetty analyysimenetelmä, joka perustuu atomiydinten havaitsemiseen voimakkaassa magneettikentässä radioaaltojen avulla. Menetelmä soveltuu erityisen hyvin molekyylirakenteiden selvittämiseen, ja sillä voidaan saada tietoa myös molekyylien kolmiulotteisesta rakenteesta sekä niiden välisistä interaktioista. NMR-spektroskopia on myös epäselektiivinen menetelmä, jolla on helppo tutkia erityyppisiä näytteitä ilman monimutkaista esikäsittelyä. Perinteisesti NMR-spektroskopian heikkoutena on ollut spektrometrien kalleus ja huono herkkyys, joka on rajannut sen käyttöä laimeiden näytteiden ja etenkin seosten analysoinnissa. Laitteistojen ja analyysitekniikoiden parantuminen viimeisten 20-30 vuoden aikana on kuitenkin kohentanut tilannetta merkittävästi, ja NMR-spektroskopian käyttäminen seosten kvantitatiiviseen analyysiin on selvässä kasvussa. Etenkin metaboliittien analysoimisesta erilaisista biologisista näytteistä on muodostunut tärkeä sovellus. Tätä kehitystä on vauhdittanut myös näytteenkäsittelyn ja spektrien prosessoinnin automaation kehittyminen, joka helpottaa suurien näytemäärien tutkimista. Suurin osa NMR-spektrien käsittelyyn tarkoitetuista ohjelmistoista ei kuitenkaan vielä ole suunniteltu ensisijaisesti suurten näytesarjojen tai seosten analysointiin. Tämä työ keskittyy kvantitatiiviseen NMR-spektroskopiaan ja sen sovelluksiin. Työssä kehitettiin kvantitatiivisia NMR-menetelmiä (pulssisarjat), sekä spektrien analyysiin soveltuvia ohjelmistotyökaluja (ImatraNMR ja SimpeleNMR), joiden tavoitteena on etenkin suurten näytesarjojen automaattisen analysoinnin helpottaminen. Kehitettyjä työkaluja käytettiin hiilivetyseosten (perusöljyt) ja kasviekstraktien analysointiin, mutta niitä voidaan soveltaa myös moniin muihin näytesarjoihin tai esimerkiksi reaktioseosten analysointiin

58th Annual Rocky Mountain Conference on Magnetic Resonance

Final program, abstracts, and information about the 58th annual meeting of the Rocky Mountain Conference on Magnetic Resonance, co-endorsed by the Colorado Section of the American Chemical Society and the Society for Applied Spectroscopy. Held in Breckenridge, Colorado, July 17-21, 2016