Phosphorus Nuclear Magnetic Resonance Studies of Ortho and Condensed Phosphates

Crutchfield, M. M.; Callis, C. V.; Irani, R. R.; Roth, Guenther

doi:10.1021/ic50004a020

Cited by 86 publications

(48 citation statements)

References 2 publications

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“…The chemical shifts of the first two are pD dependent in the region near the pKa, and the resonances shift upfield upon deuteration, in line with the behavior of other phosphates (16). Small proton-phosphorus coupling constants of [5][6][7] Hz are observed, due to the adjacent methylene protons.…”

Section: Resultsmentioning

confidence: 58%

Headgroup conformation and lipid--cholesterol association in phosphatidylcholine vesicles: a 31P(1H) nuclear Overhauser effect study.

Yèagle¹,

Hutton²,

Huang³

et al. 1975

Proc. Natl. Acad. Sci. U.S.A.

157

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The nuclear Overhauser effect has been observed in the nuclear magnetic resonance spectra of 31p. The information content of the nuclear Overhauser effect has been applied to the structure and dynamic properties of phosphatidylchoiine vesicles. In the vesicles only % of the theoretical maximum nuclear Overhauser effect enhancement is observed. This result is accounted for by dipolar interactions between the N-methyl protons and the phosphate of phosphatidylcholine, and a correlation time for internal motion of 1.4 X 10-9 sec. Addition of up to 30% cholesterol does not change the nuclear Overhauser effect enhancement or spin-lattice relaxation time of the vesicles. It is argued that the OH group of cholesterol is hydrogen bonded to the ester carbonyl oxygen of the phosphatidylcholine molecules. Amphiphilic molecules such as phospholipids and sterols are major lipid constituents of many membranes of mammalian cells and subcellular organelles. In recent years the molecular interactions of phospholipids and steroids in the lamellar gel and liquid-crystalline phases have been studied in detail by a variety of physical techniques (1-5). Although the effects of cholesterol on the structural and motional properties of phospholipid bilayers are becoming better understood (6, 7), the emphasis of previous investigations has been placed primarily on the hydrocarbon region of the bilayer system. Information on the importance of the interactions between phospholipids and steroids, especially the involvement of 30-OH group of cholesterol, in the polar head region is accumulating (8, 9), but little is known about either the precise position of the hydrophilic hydroxyl group of cholesterol in the bilayer, or which of the groups, such as the phosphate, quaternary ammonium, and carbonyl groups of phosphatidylcholine, is participating in the phospholipid-cholesterol interaction in the polar head region of the bilayer system. In order to investigate the interactions involving the polar groups of phosphatidylcholine with cholesterol, we have used phosphorus nuclear magnetic resonance (31P NMR).In this communication, we report evidence for a choline N-methyl proton interaction with the phosphate group of phosphatidylcholine in a vesicle bilayer system. The results suggest an intermolecular association which provides a model for the surface of the bilayer, and for molecular motion in the headgroup. The effects of added cholesterol lead to the conclusion that cholesterol does not interact with the phosphate group and that high percentages of cholesterol change the conformation of the headgroup, or, alternatively, the motion of that region. EXPERIMENTAL MATERIALS AND PROCEDURESEgg phosphatidylcholine (PC) was isolated and purified as described (10). PC in which the N-methyl groups were fully deuterated was prepared by Dr. Barry Lentz with phosphatidic acid hydrolyzed from egg PC by action of phospholipase D, and subsequently condensed with deuterated choline acetate (11). The lipid was purified by silicic acid chromatography. Cho...

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Section: Resultsmentioning

confidence: 58%

Headgroup conformation and lipid--cholesterol association in phosphatidylcholine vesicles: a 31P(1H) nuclear Overhauser effect study.

Yèagle¹,

Hutton²,

Huang³

et al. 1975

Proc. Natl. Acad. Sci. U.S.A.

157

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“…Estudos de fosfatos condensados realizados em 1955 mostravam a obtenção de espectros com deslocamentos químicos bem resolvidos para diferentes grupos de fosfatos: isolados, do interior de cadeias e terminais. 6,7 Porém, a determinação quantitativa dessas espécies era ainda limitada pela baixa resolução dos equipamentos disponíveis naquela época. Com o desenvolvimento de equipamentos de alta resolução, o emprego de RMN de 31 P na análise quantitativa de fosfatos já era viável no início da década de 90.…”

Section: Determinações De Massas Molares Médias De Polifosfatos Por Aunclassified

Fracionamento de polifosfato de sódio e caracterização por RMN de 31P: um experimento para aulas de físico-química

et al. 2010

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Recebido em 11/12/09; aceito em 10/5/10; publicado na web em 24/8/10 FRACTIONAL PRECIPITATION OF SODIUM POLYPHOSPHATE AND CHARACTERIZATION BY 31 P NMR: AN EXPERIMENT FOR PYSICAL CHEMISTRY CLASSES. This text describes an experiment on fractional precipitation of a polymer together with determination of average degree of polymerization by NMR. Commercial sodium polyphosphate was fractionated by precipitation from aqueous solution by adding increasing amounts of acetone. The polydisperse salt and nine fractions obtained from it were analyzed by 31 P Nuclear Magnetic Resonance and the degree of polymerization of the salts and of the fractions were calculated. Long-chain sodium polyphosphate was also synthesized and analyzed. This experiment was tested in a PChem lab course but it can be used also to illustrate topics of inorganic polymers and analytical chemistry.Keywords: sodium polyphosphate; fractional precipitation; 31 P NMR. INTRODUÇÃOA melhoria da infraestrutura de equipamentos para ensino e pesquisa nas universidades públicas brasileiras trouxe a possibilidade de exposição dos alunos a tópicos mais abrangentes e interdisciplinares, em um contexto contemporâneo. No estudo de materiais poliméricos, a determinação da massa molar média dos polímeros é de fundamental importância para todas as propriedades e, portanto, para suas aplicações tecnológicas.A determinação de massa molar média de polímeros é um assunto normalmente tratado em disciplinas experimentais de físico-química. Nessas aulas, muito frequentemente, se utilizam medidas de viscosidade de soluções diluídas de polímeros orgânicos para a determinação de massa molar média. 1,2A técnica de ressonância magnética nuclear (RMN) possibilita a identificação e quantificação de núcleos de elementos formadores de cadeias poliméricas em ambientes químicos diferentes permitindo, assim, distingui-los. Deste modo, a comparação entre os números de grupos terminais de uma macromolécula e de seus grupos intermediários pode fornecer a massa molar média numérica (M n ) da mesma.3 A técnica de RMN aplica-se à determinação de massa molecular de polímeros lineares de massa molar de até 20.000 g mol -1. Essa limitação se dá devido à dificuldade na detecção quantitativa dos grupos terminais nos polímeros de alta massa molar, que se encontram em quantidade muito inferior à dos grupos de meio de cadeias. Uma vantagem da RMN em comparação a outros métodos de determinação de massa molar de polímeros, como a cromatografia de permeação em gel, é que RMN é um método absoluto. A análise por RMN dispensa o uso de padrões de massa molar conhecida, uma vez que as concentrações dos grupos podem ser obtidas diretamente da integração dos respectivos picos, tornando-se desnecessário o uso de padrões de cada fração do material de interesse. Além disso, a técnica de RMN dispensa o controle de força iônica do meio, uma importante vantagem dessa técnica em comparação com outros métodos convencionais de determinação de massa molar, como o espalhamento de luz e a viscosimetria.O fracionamento do p...

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“…[ 29,30] Accordingly, the peak at 0.1 ppm is characteristic of H 3 PO 4 , whereas the peaks at À10.8 and À22.8 ppm were attributed to terminal and internal phosphate groups of condensed phosphates,r espectively. [30] Krawietz et al assigned the peak at À35.9 ppm to silicon hydrogen tripolyphosphate (À35 ppm).…”

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confidence: 99%

“…[30] Krawietz et al assigned the peak at À35.9 ppm to silicon hydrogen tripolyphosphate (À35 ppm). [31] For H 3 [33] The authors assigneda na dditional peak at À30 ppm to phosphorous oxidese xhibiting PÀOÀPm otifs.…”

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confidence: 99%

Role of Vanadium and Phosphorus in Substituted Keggin‐Type Heteropolyoxo Molybdates Supported on Silica SBA‐15 in Selective Propene Oxidation

2015

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Vanadium‐containing Keggin‐type heteropolyoxo molybdate ([PV2Mo10O40]5−) was supported on silica SBA‐15 (denoted as PV2Mo10‐SBA‐15). The structural evolution and catalytic activity of PV2Mo10‐SBA‐15 and a suitable reference V2Mo10Ox‐SBA‐15 were investigated under selective propene oxidation conditions by using in situ X‐ray absorption spectroscopy. 31P MAS NMR measurements of supported PV2Mo10‐SBA‐15 and reference H3PO4‐SBA‐15 were performed after the catalytic reaction. PV2Mo10‐SBA‐15 formed a mixture of mainly tetrahedral [MoOx] and [VOx] units during thermal treatment under propene oxidation conditions. Changes in the average local structure around V centers coincided with the changes in the average local structure around Mo centers and the onset of catalytic activity. In addition, mainly tetrahedral [MoOx] and [VOx] units seemed to be in close proximity and interacted under catalytic conditions. Conversely, in the reference material V2Mo10Ox‐SBA‐15 synthesized with individual V and Mo source precursors, Mo and V centers appeared to be more separated from each other. The structural environment of P in PV2Mo10‐SBA‐15 under catalytic conditions corresponded to a mixture of various species. P was connected to both the support material SBA‐15 via POSi bonds and [MoOx] or [VOx] units. Apparently, the proximity of V and Mo in Keggin precursors was a prerequisite for obtaining (Mo,V) oxide species on the support material.

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Phosphorus Nuclear Magnetic Resonance Studies of Ortho and Condensed Phosphates

Cited by 86 publications

References 2 publications

Headgroup conformation and lipid--cholesterol association in phosphatidylcholine vesicles: a 31P(1H) nuclear Overhauser effect study.

Headgroup conformation and lipid--cholesterol association in phosphatidylcholine vesicles: a 31P(1H) nuclear Overhauser effect study.

Fracionamento de polifosfato de sódio e caracterização por RMN de 31P: um experimento para aulas de físico-química

Role of Vanadium and Phosphorus in Substituted Keggin‐Type Heteropolyoxo Molybdates Supported on Silica SBA‐15 in Selective Propene Oxidation

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