Novel Instrumentation and Methods for Chemical Applications of Dissolution Dynamic Nuclear Polarization

One of the major disadvantages of Nuclear Magnetic Resonance (NMR) is its low sensitivity, mainly due to a very low spin polarization. Since 2003, Dissolution Dynamic Nuclear Polarization (D-DNP) provides a way of overcoming this drawback in solution by increasing polarization by factors exceeding 10'000-fold. In a D-DNP experiment, the high electron spin polarization at low temperatures is transferred to other nuclei (like 1H and 13C) by microwave irradiation, and the frozen sample is subsequently dissolved to room temperature while preserving part of the polarization. This thesis presents novel conceptual and instrumental developments in D-DNP that enable a better hyperpolarization of several nuclear spins. More specifically, after a brief introduction to NMR and D-DNP in Part A, we will discuss in Part B new strategies for improving microwave irradiation and implementing Longitudinal Detection Electron Spectroscopy Resonance (LODESR) in situ, c.a. at low temperature and high magnetic field. We will see how Cross Polarization can be made fully compatible with D-DNP with an original double resonance circuit developed in our laboratory (1H and another nucleus like 13C, 15N, 29Si or 129Xe). Finally, we will show how the problem of low field transfer of hyperpolarized solutions can be overcome by the use of a novel concept of a magnetic tunnel that sustains the magnetic field and prevent excessive losses of our hyperpolarized "ambitions". Finally, new applications in D-DNP that were either enabled or better realized by these new strategies are briefly presented in Chapter C

Long-Lived States of Magnetically Equivalent Spins Populated by Dissolution-DNP and Revealed by Enzymatic Reactions

Hyperpolarization by dissolution dynamic nuclear polarization (D-DNP) offers a way of enhancing NMR signals by up to five orders of magnitude in metabolites and other small molecules. Nevertheless, the lifetime of hyperpolarization is inexorably limited, as it decays toward thermal equilibrium with the nuclear spin-lattice relaxation time. This lifetime can be extended by storing the hyperpolarization in the form of long-lived states (LLS) that are immune to most dominant relaxation mechanisms. Levitt and co-workers have shown how LLS can be prepared for a pair of inequivalent spins by D-DNP. Here, we demonstrate that this approach can also be applied to magnetically equivalent pairs of spins such as the two protons of fumarate, which can have very long LLS lifetimes. As in the case of para-hydrogen, these hyperpolarized equivalent LLS (HELLS) are not magnetically active. However, a chemical reaction such as the enzymatic conversion of fumarate into malate can break the magnetic equivalence and reveal intense NMR signals

Hyperpolarized Water to Study Protein-Ligand Interactions

The affinity between a chosen target protein and small molecules is a key aspect of drug discovery. Screening by popular NMR methods such as Water-LOGSY suffers from low sensitivity and from false positives caused by aggregated or denatured proteins. This work demonstrates that the sensitivity of Water-LOGSY can be greatly boosted by injecting hyperpolarized water into solutions of proteins and ligands. Ligand binding can be detected in a few seconds, whereas about 30 min is usually required without hyperpolarization. Hyperpolarized water also enhances proton signals of proteins at concentrations below 20 M so that one can verify in a few seconds whether the proteins remain intact or have been denatured

Cross polarization from H-1 to quadrupolar Li-6 nuclei for dissolution DNP

Cross polarization from protons to quadrupolar Li-6 nuclei is combined with dynamic nuclear polarization of protons at 1.2 K and 6.7 T using TEMPOL as a polarizing agent followed by rapid dissolution. Compared to direct Li-6 DNP without cross-polarization, a higher nuclear spin polarization P(Li-6) can be obtained in a shorter time. A double resonance H-1-Li-6 probe was designed that is equipped for Longitudinally Detected Electron Spin Resonance

CARACTERIZAÇÃO FLORÍSTICA E DIVERSIDADE NA FLORESTA NACIONAL DE SÃO FRANCISCO DE PAULA, RS, BRASIL

Objetivou-se com esse trabalho encontrar os melhores indicadores para avaliar a estrutura e a diversidade no componente arbóreo em área de Floresta Ombrófila Mista na Floresta Nacional de São Francisco de Paula, RS. A amostragem da vegetação foi realizada por meio de 180 subunidades de 10 m x 10 m, onde foram inventariados todos os indivíduos arbóreos com CAP ≥ 30 cm. Foram calculados os parâmetros de frequência e densidade, os índices de dispersão de McGuinnes, Fracker e Brischle e Payandeh e diferentes índices de diversidade alfa. Os índices de dispersão revelaram o mesmo comportamento para as espécies, sendo a maioria classificadas como agregadas ou com tendência ao agrupamento, o que mostra que a floresta ainda não atingiu um estado maduro e avançado de desenvolvimento. Os índices de Margalef e Shannon obtiveram valores subestimados possivelmente influenciados pelo tamanho da unidade amostral, denotando baixa diversidade de espécies quando comparado com outras áreas. O índice de Menhinick representou a diversidade de forma bastante real mesmo em unidades amostrais pequenas, caracterizando a floresta de média a alta diversidade. Os índices de Simpson e MacIntosh denotaram baixa dominância e os índices de equidade demonstraram alta uniformidade nas espécies

Optically Enhanced Solid-State ¹H NMR Spectroscopy

International audienceLow sensitivity is the primary limitation toextending nuclear magnetic resonance (NMR) techniques tomore advanced chemical and structural studies. Photochemicallyinduced dynamic nuclear polarization (photo-CIDNP) is an NMRhyperpolarization technique where light is used to excite a suitabledonor−acceptor system, creating a spin-correlated radical pairwhose evolution drives nuclear hyperpolarization. Systems thatexhibit photo-CIDNP in solids are not common, and this effecthas, up to now, only been observed for 13C and 15N nuclei.However, the low gyromagnetic ratio and natural abundance ofthese nuclei trap the local hyperpolarization in the vicinity of thechromophore and limit the utility for bulk hyperpolarization. Here,we report the first example of optically enhanced solid-state 1HNMR spectroscopy in the high-field regime. This is achieved viaphoto-CIDNP of a donor−chromophore−acceptor molecule in a frozen solution at 0.3 T and 85 K, where spontaneous spindiffusion among the abundant strongly coupled 1H nuclei relays polarization through the whole sample, yielding a 16-fold bulk 1Hsignal enhancement under continuous laser irradiation at 450 nm. These findings enable a new strategy for hyperpolarized NMRbeyond the current limits of conventional microwave-driven DNP

Challenges in preparing, preserving and detecting para-water in bulk: overcoming proton exchange and other hurdles

Para-water is an analogue of para-hydrogen, where the two proton spins are in a quantum state that is antisymmetric under permutation, also known as singlet state. The populations of the nuclear spin states in para-water are believed to have long lifetimes just like other Long-Lived States (LLSs). This hypothesis can be verified by measuring the relaxation of an excess or a deficiency of para-water, also known as a "Triplet-Singlet Imbalance'' (TSI), i.e., a difference between the average population of the three triplet states T (that are symmetric under permutation) and the population of the singlet state S. In analogy with our recent findings on ethanol and fumarate, we propose to adapt the procedure for Dissolution Dynamic Nuclear Polarization (D-DNP) to prepare such a TSI in frozen water at very low temperatures in the vicinity of 1.2 K. After rapid heating and dissolution using an aprotic solvent, the TSI should be largely preserved. To assess this hypothesis, we studied the lifetime of water as a molecular entity when diluted in various solvents. In neat liquid H2O, proton exchange rates have been characterized by spin-echo experiments on oxygen-17 in natural abundance, with and without proton decoupling. One-dimensional exchange spectroscopy (EXSY) has been used to study proton exchange rates in H2O, HDO and D2O mixtures diluted in various aprotic solvents. In the case of 50 mM H2O in dioxane-d(8), the proton exchange lifetime is about 20 s. After dissolving, one can observe this TSI by monitoring intensities in oxygen-17 spectra of H2O (if necessary using isotopically enriched samples) where the AX(2) system comprising a "spy'' oxygen A and two protons X-2 gives rise to binomial multiplets only if the TSI vanishes. Alternatively, fast chemical addition to a suitable substrate (such as an activated aldehyde or ketone) can provide AX2 systems where a carbon-13 acts as a spy nucleus. Proton signals that relax to equilibrium with two distinct time constants can be considered as a hallmark of a TSI. We optimized several experimental procedures designed to preserve and reveal dilute para-water in bulk

Características Físico-Químicas de Sementes de Genótipos de Gergelim

O gergelim é uma oleaginosa que possui propriedades nutricionais interessantes sendo utilizado como matéria-prima de produtos industrializados e caseiros. Objetivou-se com este trabalho analisar as características físico-químicas das sementes de genótipos de gergelim, cultivados sob irrigação no cariri cearense. O experimento foi conduzido no laboratório de Bromatologia do Centec – Instituto Centro de Ensino Tecnológico – Unidade Cariri, utilizando sementes oriundas de ensaio de genótipos de gergelim de Valor de Cultivo e Uso – VCU do Programa de Melhoramento do gergelim da Embrapa Algodão. O delineamento experimental foi o de blocos casualizados, com sete tratamentos (genótipos: Mexicano, CNPAG 90-57, CNPAG 90-12, CNPAG 93-36, CNPAG 90-174, CNPAG 93-114 e CNPA 90-70) e cinco repetições. Os genótipos CNPAG 90-174 e CNPAG 93-114 podem ser considerados os melhores; o primeiro por apresentar teores mais elevados em lipídios e sódio, e o segundo em proteínas, ferro e fósforo. Todos os genótipos apresentaram bom teor de proteína (23,44%) e podem ser utilizados no melhoramento genético para geração de variedades adequadas às exigências do mercado

Slow release fertilizer in development of Schinus terebinthifolius and Sebastiania commersoniana seedlings

 O objetivo do trabalho foi avaliar diferentes doses de fertilizante de liberação lenta (FLL) no desenvolvimento de mudas de Schinus terebinthifolius e Sebastiania commersoniana. O estudo foi realizado na região do Vale do Itajaí (SC), entre março e dezembro de 2009, em viveiro localizado no município de Rio do Sul, com sementes provenientes da própria região. O delineamento experimental foi inteiramente casualizado, com 6 tratamentos em 4 repetições, tendo 40 plantas como unidade experimental. Os tratamentos foram: T1–0 kg (testemunha); T2–2 kg; T3–4 kg; T4–6 kg; T5–8 kg e T6–10 kg de FLL por m³ de substrato-base. Decorridos 189 (aroeira) e 245 (branquilho) dias da semeadura, foram analisadas as variáveis altura total, diâmetro do coleto, biomassa seca da parte aérea, biomassa seca da raiz, biomassa seca total e dose de máxima eficiência técnica. As mudas de aroeira e branquilho tiveram um melhor crescimento com a dose de 10 kg de FLL por m³ de substrato padrão e 6 kg de FLL por m3, respectivamente. Ambas as plantas responderam significativamente ao uso do fertilizante de liberação lenta, apresentando as seguintes doses de máxima eficiência técnica: 9,48 (aroeira) e 5,54 kg.m-3 (branquilho) de Basacote 6M.Palavras-chave:Branquilho; aroeira-vermelha; fertilização; produção de mudas; qualidade de mudas florestais.AbstractSlow release fertilizer in development of Schinus terebinthifolius and Sebastiania commersoniana seedlings. This reserach aimed to evaluate different doses of slow-release fertilizer (FLL) in  Schinus terebinthifolius and Sebastiania commersoniana seedlings development. The study was conducted in Vale do Itajai (SC), between March and December 2009, in a nursery in the city of Rio do Sul, with seeds from the region. The experimental design was completely randomized with 6 treatments in 4 replications, with 40 plants as experimental unit. The treatments were: T1-0 kg (control), T2-2 kg, T3- 4kg-, T4-6 kg; T5-8kg; and T6-10 kg per m³ FLL substrate base. After 189 (aroeira) and 245 (branquilho) days of sowing, the variables analyzed were total height, diameter, shoot dry biomass, root dry weight, total biomass and maximum dose of technical efficiency. The seedlings of aroeira and branquilho had better growth with the dose of 10 kg per cubic meter of FLL standard substrate and 6 kg per m3 of FLL, respectively. Both plants responded significantly to the use of slow release fertilizer, with the following maximum doses of technical efficiency 9.48 (aroeira) and 5.54 kg.m-3 (branquilho) of Basacote 6M.Keywords: Sebastiana; red aroeira; fertilization; seedling production; quality forest seedlings.  AbstractThis reserach aimed to evaluate different doses of slow-release fertilizer (FLL) in  Schinus terebinthifolius and Sebastiania commersoniana seedlings development. The study was conducted in Vale do Itajai (SC), between March and December 2009, in a nursery in the city of Rio do Sul, with seeds from the region. The experimental design was completely randomized with 6 treatments in 4 replications, with 40 plants as experimental unit. The treatments were: T1-0 kg (control), T2-2 kg, T3- 4kg-, T4-6 kg; T5-8kg; and T6-10 kg per m³ FLL substrate base. After 189 (aroeira) and 245 (branquilho) days of sowing, the variables analyzed were total height, diameter, shoot dry biomass, root dry weight, total biomass and maximum dose of technical efficiency. The seedlings of aroeira and branquilho had better growth with the dose of 10 kg per cubic meter of FLL standard substrate and 6 kg per m3 of FLL, respectively. Both plants responded significantly to the use of slow release fertilizer, with the following maximum doses of technical efficiency 9.48 (aroeira) and 5.54 kg.m-3 (branquilho) of Basacote 6M.Keywords: Sebastiana; red aroeira; fertilization; seedling production; quality forest seedlings.