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81.
Evidence is presented demonstrating that the magnitudes of the 13C chemical shifts originating from heme meso carbons provide a straightforward diagnostic tool to elucidate the coordination state of high-spin heme proteins and enzymes. Pentacoordinate high-spin heme centers exhibit 13C meso shifts centered at approximately 250 ppm, whereas their hexacoordinate counterparts exhibit 13C shifts centered at approximately -80 ppm. The relatively small spectral window (400 to -100 ppm) covering the meso-13C shifts, the relatively narrow lines of these resonances, and the availability of biosynthetic methods to prepare 13C-labeled heme (Rivera, M.; Walker, F. A. Anal. Biochem. 1995, 230, 295-302) make this approach practical. The theoretical basis for the distinct chemical shifts observed for meso carbons from hexacoordinate high-spin hemes relative to their pentacoordinate counterparts are now well understood (Cheng, R.-J.; Chen, P. Y.; Lovell, T.; Liu, T.; Noodleman, L.; Case, D. A. J. Am. Chem. Soc. 2003, 125, 6774-6783), which indicates that the magnitude of the meso-carbon chemical shifts can be used as a simple and reliable diagnostic tool for determining the coordination state of the heme active sites, independent of the nature of the proximal ligand. Proof of the principle for the 13C NMR spectroscopic approach is demonstrated using hexa- and pentacoordinate myoglobin. Subsequently, 13C NMR spectroscopy has been used to unambiguously determine that a recently discovered heme protein from Shigella dysenteriae (ShuT) is pentacoordinate. 相似文献
82.
Anderson N Pollacchi A Hayes P Therapondos G Newsome P Boyter A Smith K 《Biomedical chromatography : BMC》2002,16(6):365-372
During the acute phase response (APR) to tissue injury or infection, the liver is responsible for the level of mediators such as cytokines required at the site of inflammation and providing the essential components for wound healing and tissue repair. Additionally there are substantial alterations in the expression of plasma proteins of hepatic origin such as alpha-1-acid glycoprotein (AGP). The APR also results in alterations to the branching, sialylation and fucosylation of the oligosaccharide chains of AGP. This study investigated whether liver damage could be correlated with changes in AGP glycosylation in groups of patients with various liver diseases (alcoholic liver disease, hepatitis B, hepatitis C, cirrhosis). Hyperfucosylation occurred in all cases of liver disease, although the hepatitis B and C samples showed a more significant increase in comparison with the others. Additionally N-acetylgalactosamine (GalNAc) was detected in the majority of the hepatitis C samples, which was unexpected since this monosaccharide is not a usual component of the N-linked oligosaccharide chains. It was also determined by concanavalin (con) A chromatography that there is a shift towards the increased branching of the oligosaccharide chains in inflammatory liver diseases compared to normal serum. 相似文献
83.
Reactivity-based one-pot synthesis of oligomannoses: defining antigens recognized by 2G12, a broadly neutralizing anti-HIV-1 antibody 总被引:3,自引:0,他引:3
84.
Albermann C Soriano A Jiang J Vollmer H Biggins JB Barton WA Lesniak J Nikolov DB Thorson JS 《Organic letters》2003,5(6):933-936
[reaction: see text] In an effort to expand the scope of natural product in vitro glycorandomization (IVG), the substrate specificity of NovM was investigated. A test of four aglycon analogues and over 40 nucleotide sugars revealed NovM has a surprisingly stringent substrate specificity and provided only three new "unnatural" natural products. On the basis of the determined substrate specificity, an alternative to the sugar nucleotide biosynthetic dogma and a cautionary note for the general applicability of IVG are introduced. 相似文献
85.
Michael P. Brown Susan J. Cooper Aileen A. Frew Ljubica Manojlović-Muir Kenneth W. Muir Richard J. Puddephatt Mary A. Thomson 《Journal of organometallic chemistry》1980,198(2):C33-C35
The complex [Pt2Me2(μ-H)(μ-dppm)2][PF6] (I, dppm = Ph2PCH2PPh2) has been prepared and characterised by 1H and 31P NMR spectroscopy and by a full molecular structure determination by X-ray methods. The complex undergoes only slow reductive elimination of methane induced by added tertiary phosphine at 70°C. 相似文献
86.
Pernites R Vergara A Yago A Cui K Advincula R 《Chemical communications (Cambridge, England)》2011,47(35):9810-9812
A facile approach of making scalable nanocomposite and electro-patterned films using graphene oxide (GO) and poly(N-vinylcarbazole) (PVK) is reported. The method involves the layering of polystyrene colloidal templates, electrodeposition of the composite film on template array, and finally removal of the sacrificial templates to reveal the patterned GO-PVK arrays. 相似文献
87.
Aileen P. LothianChristopher A. Ramsden Maxine M. ShawRachel G. Smith 《Tetrahedron》2011,67(15):2788-2793
Reaction of aryltrimethylsilanes with xenon difluoride in C6F6/Pyrex® at room temperature gives aryl fluorides in good yield. The reaction is inhibited when acetonitrile is used as solvent but proceeds well in CFCl3/Pyrex® or CH2Cl2/Pyrex®. Pyrex® appears to be a very effective heterogeneous catalyst for this ipso-fluorination. The reaction does not proceed in PTFE, quartz, soda glass or glassy-carbon flasks or Pyrex® flasks pre-rinsed with 2 M NaOH. Aryltrimethylstannanes and arylboronic acids and their esters do not undergo ipso-fluorination under similar conditions. Plausible mechanisms involving electrophilic addition of polarised xenon difluoride [FXeδ+?F→Pyrexδ−] followed by ligand coupling are discussed. 相似文献