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61.
Standard reference materials for foods and dietary supplements 总被引:1,自引:0,他引:1
Sharpless KE Thomas JB Christopher SJ Greenberg RR Sander LC Schantz MM Welch MJ Wise SA 《Analytical and bioanalytical chemistry》2007,389(1):171-178
Well-characterized certified reference materials are needed by laboratories in the food testing, dietary supplement, and nutrition
communities to facilitate compliance with labeling laws and improve the accuracy of information provided on product labels,
so that consumers can make good choices. As a result of the enactment of the Nutrition Labeling and Education Act of 1990
and the Infant Formula Act of 1980, the National Institute of Standards and Technology (NIST) worked to develop a series of
food-matrix standard reference materials (SRMs) characterized for nutrient concentrations. These include SRM 1544 Fatty Acids
and Cholesterol in a Frozen Diet Composite, SRM 1546 Meat Homogenate, SRM 1548a Typical Diet, SRM 1566b Oyster Tissue, SRM
1846 Infant Formula, SRM 1946 Lake Superior Fish Tissue, SRM 1947 Lake Michigan Fish Tissue, SRM 2383 Baby Food Composite,
SRM 2384 Baking Chocolate, SRM 2385 Slurried Spinach, and SRM 2387 Peanut Butter. With the enactment of the Dietary Supplement
Health and Education Act of 1994, NIST has been working to develop suites of dietary supplement SRMs characterized for active
and marker compounds and for toxic elements and pesticides, where appropriate. An updated SRM 1588b Organics in Cod Liver
Oil, a suite of ephedra-containing materials (SRMs 3240–3245), a carrot extract in oil (SRM 3276), and a suite of ginkgo-containing
materials (SRMs 3246–3248) are available. Several other materials are currently in preparation. Dietary supplements are sometimes
provided in forms that are food-like; for these, values may also be assigned for nutrients, for example SRM 3244 Ephedra-Containing
Protein Powder. Both the food-matrix and dietary supplement reference materials are intended primarily for validation of analytical
methods. They may also be used as “primary control materials” in assignment of values to in-house (secondary) control materials
to confirm accuracy and to establish measurement traceability to NIST. 相似文献
62.
Heterologous Production of Fungal Maleidrides Reveals the Cryptic Cyclization Involved in their Biosynthesis 下载免费PDF全文
Dr. Katherine Williams Agnieszka J. Szwalbe Dr. Nicholas P. Mulholland Dr. Jason L. Vincent Dr. Andrew M. Bailey Prof. Christine L. Willis Prof. Thomas J. Simpson Prof. Russell J. Cox 《Angewandte Chemie (International ed. in English)》2016,55(23):6784-6788
Fungal maleidrides are an important family of bioactive secondary metabolites that consist of 7, 8, or 9‐membered carbocycles with one or two fused maleic anhydride moieties. The biosynthesis of byssochlamic acid (a nonadride) and agnestadride A (a heptadride) was investigated through gene disruption and heterologous expression experiments. The results reveal that the precursors for cyclization are formed by an iterative highly reducing fungal polyketide synthase supported by a hydrolase, together with two citrate‐processing enzymes. The enigmatic ring formation is catalyzed by two proteins with homology to ketosteroid isomerases, and assisted by two proteins with homology to phosphatidylethanolamine‐binding proteins. 相似文献
63.
64.
Gregory B. Kharas Wellington M. B. Barros Katherine E. Ackerman Alexa Chanos Brendan M. Comuzzie Remy Dalloul 《高分子科学杂志,A辑:纯化学与应用化学》2016,53(10):605-609
Novel trisubstituted ethylenes, ring-substituted propyl 2-cyano-3-phenyl-2-propenoates, RPhCH?C(CN)CO2C3H7 (where R is 2-C6H5CH2O, 3-C6H5CH2O, 4-C6H5CH2O, 4-CH3COO, 3-CH3CO, 4-CH3CONH, 2-CN, 3-CN, 4-CN, 4-(CH3)2N, 4-(C2H5)2N) were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and propyl cyanoacetate, and characterized by CHN analysis, IR, 1H and 13C-NMR. All the ethylenes were copolymerized with styrene (M1) in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, 1H and 13C-NMR. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500°C range with residue (2.7–8.6% wt.), which then decomposed in the 500–800°C range. 相似文献
65.
Bradley H. C. Greene Katherine N. Robertson John C. O'C. Young 《Green Chemistry Letters and Reviews》2016,9(1):1-11
Chitin and chitosan are potentially useful and environmentally friendly biopolymers with a wide range of value-added applications. Effective and green technologies for isolation of these materials are potentially important. Here, we report the use of lactic acid for the demineralization of green crab shells. Green crab shells and lactic acid, produced during cheese making, are two waste streams that could be tapped for large-scale chitin and chitosan processing. We have studied the effect of concentration and temperature on the demineralization of green crab shells. An unusual calcium lactate/lactic acid complex was also isolated and crystallographically characterized. The results have implications not only for the use of weak acids in the isolation of chitin and chitosan but also for the use of lactic acid as a solvent in green chemistry. 相似文献
66.
This paper reports on an integrated analytical approach for the noninvasive characterization of Chinese nephrite samples,
encompassing both geological reference specimens and museum objects. Natural variations induced by cationic substitutions,
as well as human-induced alterations such as heating, which both affect color, are the focus of this contribution. Totally
noninvasive methods of analysis were used, including X-ray fluorescence spectroscopy, Raman microspectroscopy, visible reflectance
spectroscopy and X-ray diffraction; moreover, the feasibility of using a portable Raman spectrometer for the in-field identification
of jades has been demonstrated. Fe/Fe+Mg (% p.f.u.) ratios of the jades have been calculated based on hydroxyl stretching
Raman bands, which will provide an important addition to similar data that are being collected at major museums in the Western
and Eastern hemispheres.
相似文献
67.
68.
Dwyer JT Holden J Andrews K Roseland J Zhao C Schweitzer A Perry CR Harnly J Wolf WR Picciano MF Fisher KD Saldanha LG Yetley EA Betz JM Coates PM Milner JA Whitted J Burt V Radimer K Wilger J Sharpless KE Hardy CJ 《Analytical and bioanalytical chemistry》2007,389(1):37-46
This article illustrates the importance of having analytical data on the vitamin and mineral contents of dietary supplements
in nutrition studies, and describes efforts to develop an analytically validated dietary supplement ingredient database (DSID)
by a consortium of federal agencies in the USA. Preliminary studies of multivitamin mineral supplements marketed in the USA
that were analyzed as candidates for the DSID are summarized. Challenges are summarized, possible future directions are outlined,
and some related programs at the Office of Dietary Supplements, National Institutes of Health are described. The DSID should
be helpful to researchers in assessing relationships between intakes of vitamins and minerals and health outcomes. 相似文献
69.
Charkoudian LK Pham DM Kwon AM Vangeloff AD Franz KJ 《Dalton transactions (Cambridge, England : 2003)》2007,(43):5031-5042
Several new analogs of salicylaldehyde isonicotinoyl hydrazone (SIH) and salicylaldehyde benzoyl hydrazone (SBH) that contain an aryl boronic ester (BSIH, BSBH) or acid (BASIH) in place of an aryl hydroxide have been synthesized and characterized as masked metal ion chelators. These pro-chelators show negligible interaction with iron(III), although the boronic acid versions exhibit some interaction with copper(II), zinc(II) and nickel(II). Hydrogen peroxide oxidizes the aryl boronate to phenol, thus converting the pro-chelators to tridentate ligands with high affinity metal binding properties. An X-ray crystal structure of a bis-ligated iron(III) complex, [Fe(SBH(m-OMe)(3))(2)]NO(3), confirms the meridonal binding mode of these ligands. Modifications of the aroyl ring of the chelators tune their iron affinity, whereas modifications on the boron-containing ring of the pro-chelators attenuate their reaction rates with hydrogen peroxide. Thus, the methoxy derivative pro-chelator (p-OMe)BASIH reacts with hydrogen peroxide nearly 5 times faster than the chloro derivative (m-Cl)BASIH. Both the rate of pro-chelator to chelator conversion as well as the metal binding affinity of the chelator influence the overall ability of these molecules to inhibit hydroxyl radical formation catalyzed by iron or copper in the presence of hydrogen peroxide and ascorbic acid. This pro-chelator strategy has the potential to improve the efficacy of medicinal chelators for inhibiting metal-promoted oxidative stress. 相似文献
70.
Haxton KJ Cole-Hamilton DJ Morris RE 《Dalton transactions (Cambridge, England : 2003)》2007,(31):3415-3420
A method of calculating the bite (P-M-P) angle for dendritic ligands is reported. Diphenylphosphine terminated dendritic ligands were modified with either a single rhodium or a rhodium complex [HRh(CO)(2)] and molecular dynamics techniques used to run simulations to determine the dynamic bite angle (beta(d)) as a time averaged property. The effects of changing the composition of the dendritic branches is investigated and comparison with experimental hydroformylation data reveals that the dendrimer with the highest linear: branched ratio also has a dynamic bite angle closest to the theoretical ideal value of 120 degrees . 相似文献