Among dissociation methods, negative electron transfer dissociation (NETD) has been proven the most useful for glycosaminoglycan (GAG) sequencing because it produces informative fragmentation, a low degree of sulfate losses, high sensitivity, and translatability to multiple instrument types. The challenge, however, is to distinguish positional sulfation. In particular, NETD has been reported to fail to differentiate 4-O- versus 6-O-sulfation in chondroitin sulfate decasaccharide. This raised the concern of whether NETD is able to differentiate the rare 3-O-sulfation from predominant 6-O-sulfation in heparan sulfate (HS) oligosaccharides. Here, we report that NETD generates highly informative spectra that differentiate sites of O-sulfation on glucosamine residues, enabling structural characterizations of synthetic HS isomers containing 3-O-sulfation. Further, lyase-resistant 3-O-sulfated tetrasaccharides from natural sources were successfully sequenced. Notably, for all of the oligosaccharides in this study, the successful sequencing is based on NETD tandem mass spectra of commonly observed deprotonated precursor ions without derivatization or metal cation adduction, simplifying the experimental workflow and data interpretation. These results demonstrate the potential of NETD as a sensitive analytical tool for detailed, high-throughput structural analysis of highly sulfated GAGs.
A highly water‐soluble phenothiazine (PTZ)–boron dipyrromethene (BODIPY)‐based electron donor–acceptor dyad ( WS‐Probe ), which contains BODIPY as the signaling antennae and PTZ as the OCl? reactive group, was designed and used as a fluorescent chemosensor for the detection of OCl?. Upon addition of incremental amounts of NaOCl, the quenched fluorescence of WS‐Probe was enhanced drastically, which indicated the inhibition of reductive photoinduced electron transfer (PET) from PTZ to 1BODIPY*; the detection limit was calculated to be 26.7 nm . Selectivity studies with various reactive oxygen species, cations, and anions revealed that WS‐Probe was able to detect OCl? selectively. Steady‐state fluorescence studies performed at varied pH suggested that WS‐Probe can detect NaOCl and exhibits maximum fluorescence in the pH range of 7 to 8, similar to physiological conditions. ESI‐MS analysis and 1H NMR spectroscopy titrations showed the formation of sulfoxide as the major oxidized product upon addition of hypochlorite. More interestingly, when WS‐Probe was treated with real water samples, the fluorescence response was clearly visible with tap water and disinfectant, which indicated the presence of OCl? in these samples. The in vitro cell viability assay performed with human embryonic kidney 293 (HEK 293) cells suggested that WS‐probe is non‐toxic up to 10 μm and implicates the use of the probe for biological applications. 相似文献
The pivotal aim of the present study is to employ fractional natural decomposition method (FNDM) to find the solution for a nonlinear system arising in thermoelasticity. The considered coupled system is generalised many physical phenomena associated with the material with elastic characters and its temperature and also which is called a Cauchy problem. We consider the coupled system by incorporating the Caputo fractional operator and investigate three distinct cases for different initial values to illustrate the applicability and efficiency of the FNDM. With respect to fractional order, we capture the behaviour of the achieved solution cited in three different cases and exemplified with the aid of 2D and 3D plots for the particular value of the parameters in the model. Moreover, some interesting behaviours of the projected model are confirms the prominence of the employed fractional operator while analysing the nonlinear coupled equations exemplifying real-world problems and also shows the capability of the considered algorithm. 相似文献
The cross-coupling reaction of triarylbismuths with acid chlorides using a catalytic amount of PdCl2/PPh3 afforded the corresponding ketones in high yields. The reactions of aromatic and aliphatic acid chlorides occurred with atom efficiency, as 3 equiv of acid chlorides coupled effectively with 1 equiv of triarylbismuths to yield 3 equiv of the corresponding diaryl and alkyl aryl ketones. 相似文献
Kinetics of the reaction between solid cobalt(II) acetate and solid substituted aniline hydrochlorides have been studied by thermal analysis. All the reactions go to completion. The crystalline products were characterized by physico-chemical methods. The energy of activation is 83.4,44.2,64.2,100.9,79.8,99.9, 135.9 and 168.7 kJ mol–1for the reactions of aniline, 3- and 4-chloro-, 4-iodo-, 4-bromo-, 4-fluoro-, 4-methyl- and 4-methoxy aniline hydrochlorides with cobalt acetate. A plot of energy of activation against Hammett's constant is linear with a slope of –169.9 kJ mol–1. A comparison between the reactivity of these reactions by the capillary and the thermal methods has been done.
Zusammenfassung Mittels Thermoanalyse wurde die Kinetik der Festkörperreaktion zwischen Kobalt(II)azetat und substituierten Anilinhydrochloriden untersucht. Alle Reaktionen laufen vollständig ab. Die kristallinen Produkte wurden mittels physikalisch-chemischer Methoden charakterisiert. Die Aktivierungsenergie der Reaktion von Kobalt(II)azetat mit Anilin, 3- und 4-Chlor-, 4-Jod-,4-Brom-, 4-Fluor-, 4-Methoxy- und 4-Methylanilin beträgt 83.4,44.2,64.2,100.9,79.8,99.9,168.7 bzw. 135.9 kJ/mol. Bei der Darstellung der Aktivierungsenergie in Abhängigkeit von der Hammettkonstante konnte Linearität mit einem Anstieg von – 169.9 kJ/mol festgestellt werden. Die Reaktivität dieser Reaktionen wurde mittels Kapillar- und thermischen Verfahrens verglichen.
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