Optimum tip angle and relaxation delay for quantitative analysis

Traficante, Daniel D.

doi:10.1002/cmr.1820040204

Cited by 35 publications

(25 citation statements)

References 4 publications

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“…All data were acquired with the sample maintained at 25jC. Selection of NMR data acquisition parameters for quantitative analysis was done according to previous studies (14). The exact resonance positions integrated for each lipid class are given below.…”

Section: Nmr Data Acquisitionmentioning

confidence: 99%

Quantitative evaluation of sebum lipid components with nuclear magnetic resonance

Robosky

Wade

Woolson

et al. 2008

Journal of Lipid Research

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A NMR spectroscopic method is described that enables the quantitation of specific lipid classes and components, independent of fatty acid composition. We demonstrate this method for measuring cholesterol, squalene, and pools of sterol esters, wax esters (WEs), and triglyceride (TG) components in sebum and meibum. When 600 MHz NMR equipment is used in conjunction with highly sensitive cryogenically cooled probes, this method has adequate sensitivity, and for some applications, advantages over commonly used HPLC-evaporative light-scattering detection and mass spectrometry-based approaches. This method is shown to be useful for preclinical and clinical monitoring of the efficacy of sebum-reducing agents in animals and humans. In Syrian hamsters, 3% topical flutamide and 20 mg/kg oral isotretinoin reduced sterol esters by 18.7% and 30.0%, respectively, and reduced WEs by 32.9% and 31.8%, respectively, as measured in a punch biopsy of the ear. In a 72 patient clinical methodology study, the assay delivered reproducible and noninvasive measurements of WEs, cholesteryl esters, TGs, and squalene from Sebutape: skin blots. The quantitative results of sebum analysis obtained by the NMR method correlate well with those obtained with HPLC-based approaches. This approach may be broadly applicable to cases in which fatty acid-independent quantification of lipid classes is desired. Mammalian skin is composed of three primary layers: the stratum corneum, the epidermis, and the dermis. The outer layer of the skin, the stratum corneum, primarily functions as a barrier to the external environment, preventing water loss and the invasion of microorganisms. Sebum secreted to the stratum corneum from the sebaceous glands is a key component of the skin surface and has various demonstrated and postulated functions (1). Sebum itself is a complex mixture of lipids and is produced by the sebaceous glands. At maturation, the acinar cells of the sebaceous glands lyse and release sebum into the lumenal duct, from which the sebum is secreted. Cholesterol, sterol esters, wax esters (WEs), and triglycerides (TGs) are the primary lipids found in the sebum of many mammals, and squalene is also a major component of human sebum. In humans, the predominant sterol esters are cholesteryl esters (CEs), whereas in male Syrian hamster (a common sebum model), they are chiefly fatty acid esters of a single predominant noncholesterol sterol (2). The identity of the sterol constituting these esters in this species has not been identified, and herein we will refer to these as hamster sterol esters (HSEs). WEs are unique to sebum in that they are not synthesized by other cells in the body. Sebum composition can be modified from its native state by the action of xenobiots, which can greatly increase the complexity of its biochemical makeup; for example, bacterial hydrolytic enzymes are known to break down TGs to produce free fatty acids (3).A number of methods to isolate and qualitatively and/ or quantitatively analyze the lipid components of sebum and/...

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Section: Nmr Data Acquisitionmentioning

confidence: 99%

Quantitative evaluation of sebum lipid components with nuclear magnetic resonance

Robosky

Wade

Woolson

et al. 2008

Journal of Lipid Research

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“…We suspect that these conditions may not be suitable for studying a transient system. In the experiments listed in this work, we made use of the recommendations in recent literature for improving NMR analyses (Traficante, 1992;Traficante and Steward, 1994). These articles showed that a 74" tip angle, and a pulse repetition period (PR) to relaxation time ratio (PR/Tl) of 2, yield 90% integral accuracy.…”

Section: Discussionmentioning

confidence: 97%

Reaction of methanol with chlorate ions in acid solution containing Hg⁺² by NMR

et al. 1996

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“…Experimental spectra were collected using a 10 µs pulse‐width, which equated to a ~30° tip angle. By using a reduced tip‐angle for quantitative NMR, the required recycle delay for re‐magnetization is greatly reduced, and can be calculated using eqn , from Traficante :

\frac{italicPR}{T_{1}} = In (\frac{100 - italicRC * cos italicα}{100 - italicRC})

where PR = recycle delay, T 1 = target t 1 , RC = recovered magnetization (%) and α = tip angle.…”

Section: Methodsmentioning

confidence: 99%

Application of quantitative nuclear magnetic resonance spectroscopy to biological acidification of barley mashes

DiCaprio¹,

Edwards²

2014

J. Inst. Brew.

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Spontaneous biological acidification has long been a part of the German brewing tradition, and was historically used to optimize the pH of brewhouse mashes. By facilitating the growth of native barley flora, the production of lactic, acetic and succinic acids sours the mash, functioning in a similar way to the addition of food-grade acids, which are prohibited under the Reinheitsgebot of 1516. Traditionally, sour mashes have been performed at the 'optimum' temperature of 49°C. Quantitative proton nuclear magnetic resonance spectroscopy was used for the investigation and quantitation of organic acids produced by acidified mashes over a range of temperatures. All target metabolites demonstrated an inverse relationship with temperature, although lactic acid reached a relative maximum at 49°C, which is in agreement with the customary sour mash temperature. Therefore, it would seem that the optimization of a sour mash is dependent not on absolute acid concentration, which would give the greatest pH regulation potential, but on the relative acid concentration, an important factor influencing the final flavour profile of a beer.

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Optimum tip angle and relaxation delay for quantitative analysis

Cited by 35 publications

References 4 publications

Quantitative evaluation of sebum lipid components with nuclear magnetic resonance

Quantitative evaluation of sebum lipid components with nuclear magnetic resonance

Reaction of methanol with chlorate ions in acid solution containing Hg⁺² by NMR

Application of quantitative nuclear magnetic resonance spectroscopy to biological acidification of barley mashes

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Optimum tip angle and relaxation delay for quantitative analysis

Cited by 35 publications

References 4 publications

Quantitative evaluation of sebum lipid components with nuclear magnetic resonance

Quantitative evaluation of sebum lipid components with nuclear magnetic resonance

Reaction of methanol with chlorate ions in acid solution containing Hg+2 by NMR

Application of quantitative nuclear magnetic resonance spectroscopy to biological acidification of barley mashes

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Reaction of methanol with chlorate ions in acid solution containing Hg⁺² by NMR