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831.
Acrylamide: update on selected research activities conducted by the European food and drink industry
Taeymans D Andersson A Ashby P Blank I Gondé P van Eijck P Faivre V Lalljie SP Lingnert H Lindblom M Matissek R Müller D Stadler RH Studer A Silvani D Tallmadge D Thompson G Whitmore T Wood J Zyzak D 《Journal of AOAC International》2005,88(1):234-241
This paper reviews the progress made by the European food and drink industry (CIAA) on acrylamide with regard to analytical methods, mechanisms of formation, and mitigation research in the major food categories. It is an update on the first CIAA review paper, "A Review of Acrylamide: An Industry Perspective on Research, Analysis, Formation and Control." Initial difficulties with the establishment of reliable analytical methods, in most cases, have now been overcome, but challenges remain in terms of the need to develop simple and rapid test methods and certified reference materials. Many trials have been conducted under laboratory and experimental conditions in a variety of foods, and a number of possible measures have been identified to relatively lower the amounts of acrylamide in food. Promising applications were studied in reconstituted potato models by addition of amino acids or use of asparaginase. In bakery wares, predictive models have been established to determine the role of ammonium carbonate and invert sugar in acrylamide formation. Studies in several commercial foods showed that acrylamide is not stable over time in roasted and ground coffee. Some progress in relatively lowering acrylamide in certain food categories has been achieved, but at this stage can only be considered marginal. Any options that are chosen to reduce acrylamide in commercial products must be technologically feasible and must not adversely affect the quality and safety of the final product. 相似文献
832.
Summary Silver and lead, respectively, are determined in a microcalorimeter by measuring the effect of the cation concentration upon an enzyme catalyzed reaction. The reduction in heat of the glucose oxidase catalyzed reaction in presence of Ag+ and Pb2+ is confirmed.
This work was supported by USPHS Grant CA 08023. 相似文献
Zusammenfassung Silber bzw. Blei kann man mit einem Mikrokalorimeter bestimmen, indem die Wirkung der Konzentration des Kations auf eine enzymatische Reaktion gemessen wird. Die Herabsetzung der Wärmetönung der durch Glukoseoxydase katalysierten Reaktion in Gegenwart von Ag+ bzw. Pb2+ wurde bestätigt.
This work was supported by USPHS Grant CA 08023. 相似文献
833.
834.
Ana Snchez‐Migalln Antonio delaHoz Concepcin Lpez RosaM. Claramunt Lourdes Infantes Sam Motherwell Kenneth Shankland Harriott Nowell Ibon Alkorta Jos Elguero 《Helvetica chimica acta》2003,86(4):1026-1039
The crystal structure of 1‐hydroxy‐2,4,5‐triphenyl‐1H‐imidazole 3‐oxide ( 1 ) has been determined from laboratory X‐ray powder‐diffraction data. The two independent molecules in the asymmetric unit form chains via O? H???O hydrogen bonds related by a twofold screw axis. One of the O???O distances is extremely short (2.32(1) and 2.43(1) Å). Solid‐state NMR spectroscopy (CPMAS) combined with calculation of absolute shieldings (GIAO/B3LYP/6‐31G*) allowed us to determine that the compound behaves as if the O? H???O hydrogen bond has the proton in the middle (single‐well potential), resulting in the near identity of both 15N‐NMR signals. 相似文献
835.
Groenhof G Bouxin-Cademartory M Hess B De Visser SP Berendsen HJ Olivucci M Mark AE Robb MA 《Journal of the American Chemical Society》2004,126(13):4228-4233
Atomistic QM/MM simulations have been carried out on the complete photocycle of Photoactive Yellow Protein, a bacterial photoreceptor, in which blue light triggers isomerization of a covalently bound chromophore. The "chemical role" of the protein cavity in the control of the photoisomerization step has been elucidated. Isomerization is facilitated due to preferential electrostatic stabilization of the chromophore's excited state by the guanidium group of Arg52, located just above the negatively charged chromophore ring. In vacuo isomerization does not occur. Isomerization of the double bond is enhanced relative to isomerization of a single bond due to the steric interactions between the phenyl ring of the chromophore and the side chains of Arg52 and Phe62. In the isomerized configuration (ground-state cis), a proton transfer from Glu46 to the chromophore is far more probable than in the initial configuration (ground-state trans). It is this proton transfer that initiates the conformational changes within the protein, which are believed to lead to signaling. 相似文献
836.
The mechanism of the transformation of (η5-C5H5)2NbCl2 to (η5-C5H5)2NbH3 by hydridoaluminate reducing agents has been investigated. Results suggest disproportionation of a niobium(IV) hydrite, leading to the trihydride product and a niobium(III) hydridoaluminate, (η5-C5H5)2NbH2AlR2, which in turn is converted to the trihydride on hydrolysis. (η5-C5H5)2NbH2AlH2 has been isolated; deuterium labelling shows that hydrogens exchange between ring and metal-bridging positions in this molecule. 相似文献
837.
Ionic liquid (IL) was covalently bonded onto the silica capillary surface and the electroosmotic flow was reversed over a pH range of 3.5 to 7. Sildenafil (SL) and its metabolite UK-103,320 (UK) in human serum were detected by solid-phase extraction followed by capillary zone electrophoresis-mass spectrometry analysis. The running buffer contained 10 mM acetic acid adjusted to pH 4.5 with 1 M ammonia, and the separating voltage was set to -25 kV. The adsorption of the analytes onto the bare capillary wall was eliminated by the IL coating and the drugs were baseline-separated within 14 min with detection limits (S/N = 3) of 14 and 17 ng/mL for SL and UK, respectively. The method developed showed good intraday precision in terms of relative standard deviation (RSD) with respect to migration time (RSD = 0.76%, n = 5) and peak area (RSD = 3.4%, n = 5); the relative coefficients of linear regression for both targets were better than 0.99 within linear dynamic range (SL: 50-600 ng/mL; UK: 40-400 ng/mL). Satisfactory interday precision was obtained with respect to the slope of the regression (RSD = 4.21%, n = 9) and the migration time (RSD = 1.1%, n = 9). The IL coating could be used with stable electroosmotic flow (RSD = 2.78%, n = 10) for at least 80 h. 相似文献
838.
In Howa Jeong Young Sam Park Myong Sang Kim Yong Sup Song 《Journal of fluorine chemistry》2003,120(2):195-209
α- or β-Trifluoromethylated vinylstannanes 1, 2a, 3 and 4 were prepared form 1,1-bis(phenylthio)-2,2,3,3,3-pentafluoropropylbenzene (5) via several steps. The cross-coupling arylation reactions of 1–4 with aryl iodides bearing a bromo, methoxy, methyl, nitro or trifluoromethyl group on para- or meta-position of benzene ring afforded the corresponding coupling products in good yields. Compounds 1, 2a and 4 underwent the acylation reaction with various types of acyl chlorides to give the corresponding trifluoromethylated enone derivatives in good yields. Reduction of trifluoromethylated enone derivatives with LiAlH4, followed by Fridel-Craft’s type of cyclization with AlCl3 provided trifluoromethylated indene derivatives in good yields. 相似文献
839.
[reaction: see text] Type II isopentenyl diphosphate:dimethylallyl diphosphate (IPP:DMAPP) isomerase from Synechocystis PCC 6803 catalyzes the interconversion of IPP and DMAPP. Upon incubation of the enzyme with IPP or DMAPP in 2H2O, one deuterium is incorporated into the C2 methylene of IPP, two deuteriums are incorporated at C4, and three deuteriums are incorporated into the (E)-methyl of DMAPP. 相似文献
840.
Sam Huckaba 《Proceedings of the American Mathematical Society》1996,124(5):1393-1401
A -dimensional version is given of a -dimensional result due to C. Huneke. His result produced a formula relating the length to the difference , where is primary for the maximal ideal of a -dimensional Cohen-Macaulay local ring , is a minimal reduction of , , and is the Hilbert-Samuel polynomial of . We produce a formula that is valid for arbitrary dimension, and then use it to establish some formulas for the Hilbert coefficients of . We also include a characterization, in terms of the Hilbert coefficients of , of the condition .