On-Line LC-GC for the Analysis of the Minor Components in Edible Oils and Fats – The Direct Method Involving Silylation

The precise location of a substrate in cytochrome P450 (CYP) governs the orientation of the oxidation position. Such information is generally obtained from biochemical data, but modeling approaches have also been used to explain these locations. We used X-ray data and modeling techniques to distinguish between the series of putative linear or curved channels which lead the substrate from the outer side of the protein to the inner, and then into the heme pocket; these techniques were also used to identify the largest such channels. Two new methods for precisely determining the 3-D structure of proteins using X-ray crystallography were proposed in order to identify these channels: first, the use of both straight and curved channels, and second, the sphere method. These data are compared with Poulos channels, and with Caver (or Mol on line) modeling methodologies. Our methods were developed from studies of the interaction between cytochrome P450CAM(CYP101) fromPseudomonas putida(as expressed inEscherichia coli) and the indolic base β-carboline. Apart from the identification of potential access channels leading to the heme-containing active site, a new explanation was advanced for the substrate's hydroxylation position. The sphere method seems to have potential to become a general and direct method for prediction of substrate access channels from reduced- or low-resolution crystallographic data.

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Laser-Induced Breakdown Spectroscopy of AL-Samples: Application to Chemical Analysis of Metallic Elementsf

Laser Chemistry ◽

10.1155/1995/90962 ◽

1995 ◽

Vol 16 (2) ◽

pp. 75-82 ◽

Cited By ~ 11

Author(s):

B. Bescós ◽

J. Castaño ◽

A. González Ureña

Keyword(s):

Chemical Analysis ◽

Simultaneous Detection ◽

Laser Induced Breakdown Spectroscopy ◽

Minor Components ◽

Experimental Conditions ◽

Breakdown Spectroscopy ◽

Non Invasive ◽

Multichannel Analysis ◽

Laser Induced Breakdown ◽

On Line

This paper reports on the simultaneous detection of Mg, Mn, Fe and Pb in Al samples using laser-induced breakdown spectroscopy and optical multichannel analysis of the photoablated microplasma. Using calibrated samples, well characterized linear working curves were determined for these minor components over the 0.01–1% concentration range. In addition optimum experimental conditions were found that allow the analysis to be carded out in a fast and non-invasive manner. The potential application of the method to on-line industrial analysis is also suggested.

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Direct method for quantification of glycidol fatty acid esters in edible oils

European Journal of Lipid Science and Technology ◽

10.1002/ejlt.201000395 ◽

2011 ◽

Vol 113 (3) ◽

pp. 356-360 ◽

Cited By ~ 25

Author(s):

Hiroki Shiro ◽

Naoki Kondo ◽

Nobuyuki Kibune ◽

Yoshinori Masukawa

Keyword(s):

Fatty Acid ◽

Edible Oils ◽

Direct Method ◽

Fatty Acid Esters ◽

Acid Esters

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The composition of edible oils modifies β-sitosterol_γ-oryzanol oleogels Part I: Purified triglyceride oils

10.22541/au.161591574.43176928/v1 ◽

2021 ◽

Author(s):

Maria Scharfe ◽

Eckhardt Flöter ◽

Daniel Prange

Keyword(s):

Network Formation ◽

Edible Oils ◽

Sol Gel ◽

Small Deformation ◽

Tube Formation ◽

Oxidation Products ◽

Minor Components ◽

Fa Composition ◽

Oil Components

The role of solvent composition, in particular, minor oil components on sterol/sterol ester oleogels, has been studied recently [1]. Reportedly, deterioration products hamper network formation and modify the gel’s macroscopic properties, probably due to alterations of the scaffolding elements’ interactions. However, the role of the FA composition of TAGs has not yet been addressed. In this study, minor oil components of three vegetable oils with varying degrees of unsaturation (iodine values) were removed, and the oils were chemically and physically characterized before and after the treatment. Consequently, β sitostero/γ-oryzanol oleogels were produced, and the gel-sol (DSC) and sol-gel (rheology) transitions were monitored. Moreover, large and small deformation tests were performed, and the results were linked to oil parameters. In contrast to minor oil components, the FA composition has little impact on oleogel properties. The decline in gel hardness with IV is possibly linked to a lower solvent viscosity. However, a considerable drop in gel-sol transition temperature was observed with increasing IV indicating fewer elements of scaffolding. That was linked to the rapid formation of primary oxidation products in purified flaxseed oil during oleogel preparation, impairing tube formation. Similar to previous results on deterioration products, these minor components seem to aid network strength at low concentrations resulting in similar transition enthalpies and G’. That might be due to shifted network interactions in the presence of molecular species with functional groups. In the second part of this study, these modified interactions in the presence of selected minor components will be discussed.

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Photodegradation of Riboflavin under Alkaline Conditions: What can Gas-Phase Photolysis Tell Us About What Happens in Solution?

10.20944/preprints202108.0307.v1 ◽

2021 ◽

Author(s):

Natalie G.K. Wong ◽

Chris Rhodes ◽

Caroline E.H. Dessent

Keyword(s):

Mass Spectrometry ◽

Gas Phase ◽

Direct Method ◽

Photochemical Reactions ◽

Solution Phase ◽

Ionization Mass ◽

Phase Reaction ◽

Esi Ms ◽

Alkaline Conditions ◽

On Line

The application of electrospray ionization mass spectrometry (ESI-MS) as a direct method for detecting reactive intermediates is a technique of developing importance in the routine monitoring of solution-phase reaction pathways. Here, we utilize a novel on-line photolysis ESI-MS approach to detect the photoproducts of riboflavin in aqueous solution under mildly alkaline conditions. Riboflavin is a constituent of many food products, so its breakdown processes are of wide interest. Our on-line photolysis setup allows for solution-phase photolysis to occur within a syringe using UVA LEDs, immediately prior to being introduced into the mass spectrometer via ESI. Gas-phase photofragmentation studies via laser-interfaced mass spectrometry of deprotonated riboflavin, [RFH], the dominant solution-phase species under the conditions of our study, are presented alongside the solution-phase photolysis. The results obtained illustrate the extent to which gas-phase photolysis methods can inform our understanding of the corresponding solution-phase photochemistry. We determine that the solution-phase photofragmentation observed for [RFH] closely mirrors the gas-phase photochemistry, with the m/z 241 ion being the only major condensed-phase photoproduct. Further gas-phase photoproducts are observed at m/z 255, 212, and 145. The value of exploring both the gas- and solution-phase photochemistry to characterize photochemical reactions is discussed.

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