15 research outputs found

    The effect of iron binding on the conformation of transferrin. A small angle x-ray scattering study.

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    Distance distribution functions, p(r), radii of gyration, Rg, and radii of gyration of cross section, Rq, of apotransferrin, monoferric transferrin, and diferric transferrin have been compared. The alteration of Rg and Rq upon iron binding has been determined by a difference method. An unusual feature of the stepwise structural changes of transferrin upon iron saturation is that binding of the first ferric ion is responsible for more than half of the whole change in Rq, whereas Rg alters significantly only after the binding of the second ferric ion

    Application of a Novel Small-Scale Sample Cleanup Procedure Prior to MALDI-TOF-MS for Rapid Pigment Fingerprinting of Red Wines

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    This study evaluates the anthocyanin and derived pigment composition of Vitis vinifera red wines of Vranec, Merlot, and Cabernet Sauvignon produced in 2006, 2007, and 2008 vintages from the Tikve š wine region in the Republic of Macedonia.Their profile was established using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) technique. A total of 22 anthocyanins and derived pigments have been identified in the samples including 10 anthocyanins, 1 ethyl-bridged flavanol – anthocy- anin adduct, and 11 pyranoanthocyanins. MALDI-TOF-MS analysis was performed after solid-phase extraction of the wines by using, for the first time, the Zip-Tip® C18 stationary phase, introducing a novel small-scale sample cleanup proce- dure prior to the rapid MALDI-TOF-MS fingerprinting of wine samples. 2 ′ ,4 ′ ,6 ′ -Trihydroxyacetophenone (dissolved in acetonitrile/water 1:1, v / v ) was used as a matrix. The qualitative screening of anthocyanins and derived pigments with MALDI- TOF-MS confirmed the presence of glucoside, acetylglucoside, and p -coumaroylglucoside derivatives of anthocyanins in the wine samples. Furthermore, pyranoanthocyanins formed by reactions of anthocyanins with pyruvic acid and acetaldehyde, as well as flavanol – pyranoanthocyanins and ethyl-bridged flavan-3-ol-anthocyanin adduct pigments have been detected in the samples
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