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Copyright of Science Technology & Engineering is the property of Chinese Society of Technology Economics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Hebei University of Science & Technology is the property of Hebei University of Science & Technology, Journal of Hebei University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Water Conservancy & Electric Power Technology & Application is the property of Omniscient Pte. Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Telecommunications Science is the property of Beijing Xintong Media Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Polycarboxylic acids (PACs) are important metabolic products in almost all living bodies, yet current analytical methods for detection of PACs in tea beverages are still unsatisfactory due to the complex matrix and physicochemical properties of PACs. In this work, a rapid method was developed for the simultaneous determination of 7 PACs, including tartaric acid, α-ketoglutaric acid, malic acid, malonic acid, cis -aconitic acid, succinic acid, and fumaric acid, in beverages, based on selective removal of the matrix in combination with liquid chromatography–mass spectrometry (LC-MS) analysis. By stirring with activated carbon and the Na2CO3 solution, the matrix in beverages was selectively removed, and PACs were almost retained in the supernatant of diluted Na2CO3 solution. Under optimized parameters, the limit of quantitation for the PACs was in the range of 1–50 ng/mL, and the content of the PACs in 8 beverages was determined with the recovery range of 72.2%–122.5%. The contents of malic acid, malonic acid, and succinic acid in tea beverages were found to be greater than those in non-tea beverages. Moreover, the concentration of these PACs in beverages was found to be multiplied many times in their deterioration period, especially for fumaric acid and α-ketoglutaric acid. These results indicated that PACs can be selected as a criterion to differentiate qualified tea beverages from spoiled beverages. [ABSTRACT FROM AUTHOR]

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Clarithromycin has significant antibacterial effect against Gram positive bacteria, and has been widely used as an important clinical antibiotic at present. As a derivative of microbial secondary metabolites, however, clarithromycin products have a large number of impurities, and some trace impurities also need further structural analysis. In this study, the mass spectrometric fragmentation reactions of clarithromycin K and its impurities of KL and KO were systematically studied by electrospray ionization tandem mass spectrometry ( ESI-MS/ MS) and quantum calculation. Quantum calculation showed that the amino N atom of deoxyaminoglycosides ( the No. 5 side chain unit) is the most preferred protonation site in the structure of clarithromycin. Upon collisional activation, the protonated molecules undergo a serie of proton migration and fragmentation reactions on side chain groups as the followings: 1) The ionizing proton transfers to the 0 5a atom in the No. 5 side chain group and triggers the loss of macrolides to form an oxoniumion of the dehydrided deoxyaminoglycoside (KSa-P, m/ z 158.1). 2) The ionizing proton transfers to the 05b atom in the No. 5 side chain group, which triggers the ring-opeaning reaction of the deoxyaminoglycosides group to give a characteristic fragment ion of N-(3-hydroxybutylidene)-N-methylmethanaminium (KSc-P, m/ z 11 6. 1 ). 3) Migration of the ionizing proton to the 06 atom results in the loss of methanol. 4) Migration of t he ionizing proton to the 03a atom results in the formation of K3a, which undergoes migration of the pyranose unit due to the nucleophilic attack of the 05d atom of the No. 5 side chain unit, and the subsequent loss of macrolides to form anoxoniumion at m/ z 316. 2 (K3a-1P). 5) K3a can also undergo nucleophilic reaction due to the nucleophilic attack of the 03c atom of the para hydroxyl, and subsequent fragmentation to produce the characteristic ion K3a-2P by losing C8 H12O3, and further cleavage to give the characteristic ion K3a-2P-P via the loss of methanol. The impurities of KL and KO have high similarity to clarithromycin in structure, which only differ in the No. 9 side chain unit. As expected, they have very similar tandem mass spectra, in which there are several characteristic neutral losses of CH4O, C8 H12 O3 and (C8 H12 O3 + CH4O) in the high mass region, and abundant characteristic fragment ions at m/z 316, m/z 158 and m/z 11 6 in the low mass region. This work summarizes the MS fragmentation law of clarithromycin and its analogue, provides a reference for the structure derivation of the other impurities of clarithromycin and it metabolites. [ABSTRACT FROM AUTHOR]

Copyright of Journal of East China University of Science & Technology is the property of Journal of East China University of Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Clarithromycin has significant antibacterial effect against Gram positive bacteria. and has been widely used as an important clinical antibiotic at present. As a derivative of microbial secondary metabolites, however. clarithromycin products have a large number of impurities, and some trace impurities also need further structural analysis. In this study. the mass spectrometric fragmentation reactions of clarithromycin K and its impurities of KL and KO were systematically studied by electrospray ionization tandem mass spectrometry (ESI-MS/MS) and quantum calculation. Quantum calculation showed that the amino N atom of deoxyaminoglycosides (the No. 5 side chain unit is the most preferred protonation site in the structure of clarithromycin. Upon collisional activation, the protonated molecules undergo a serie of proton migration and fragmenta tion reactions on side chain groups as the followings: 1) The lonizing proton transfers to the O5a atom in the No, 5 side chain group and triggers the loss of macrolides to form an oxonium ion of the dehydrided deoxyaminoglycoside (K5a-P, m/z 158. 1). 2) The ioni- zing proton transfers to the 05b atom in the No. 5 side chain group, which triggers the ning opesting reaction of the deoxyaminoglycosides group to give a characteristic frog mention of N-(3-hydroxybutylidene)-N-methylmethanaminium (K5e-P, m/= 116. 1). 3) Migration of the ionizing proton to the 06 atom results in the loss of methanol: Migration of the ionizing proton to the 03a atom results in the formation of K3a, which undergoes migration of the pyranose unit due to the nucleophilic attack of the 05 atom of the No. 5 side chain unit, and the subsequent loss of macrolides to form an oxo nium ion stm/z 316.2 (K3a-1P), 5) K3a can also undergo nucleophilic reaction due to the nucleophilic attack of the O3c atom of the pura hydroxyl, and subsequent fragmen tation to produce the characteristic ion K3-2P by losing C, H,O,. and further cleavage to give the characteristic ion K3a-2P-P via the loss of methanol. The impurities of KL and KO have high similarity to clarithromycin in structure. which only differ in the No. 9 side chain unit. As expected. they have very similar tandem mass spectra, in which there are several characteristic neutral losses of CH4O,C8H12O3, and (C8H12O3+ CH4O) in the high mass region. and abundant characteristic fragment ions at m/z 316. m/z 158 and m/z 116 in the low mass region. This work summarizes the MS fragmentation law of clarithromycin and its analogue. provides a reference for the structure derivation of the other impurities of clarithromycin and it metabolites. [ABSTRACT FROM AUTHOR]

Copyright of Silicone Material is the property of Silicone Material Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)