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131.
Alkaline phosphatase (ALP) is a phosphomonoester hydrolase that is commonly used as a conjugating enzyme in biological research. A wide variety of substrates have been developed to assay its activity. In this study, we developed an ALP assay method utilizing merocyanine 700 (MC700) based substrate MC700 phosphate (MC700p). MC700 is a near-infrared fluorescent merocyanine dye, and has excitation/emission maxima at 686 nm/722 nm in ALP assay buffer. Upon hydrolysis by ALP, MC700p is converted to MC700. The fluorescence of MC700 is dependent on the pH and detergent concentration in the buffer. The fluorescence signal produced by MC700p hydrolysis is linearly related to the ALP amount and substrate concentration. A stop solution containing EDTA could be used to stop the ALP/MC700p reaction. It was also demonstrated that MC700p could substitute pNpp as the ALP substrate in a commercial 17β-Estradiol enzyme immunoassay kit. 相似文献
132.
A dual-catalysis approach, namely the combination of an achiral nucleophilic catalyst and a chiral anion-binding catalyst, was applied to the Steglich rearrangement to provide α,α-disubstituted amino acid derivatives in a highly enantioselective fashion. Replacement of the nucleophilic co-catalyst for isoquinoline resulted in a divergent reaction pathway and an unprecedented transformation of O-acylated azlactones. This strategy provided highly substituted α,β-diamino acid derivatives with excellent levels of stereocontrol. 相似文献
133.
The present preliminary investigation reports, for the first time, the effects of typical cationic and anionic surfactants
on the microwave-assisted solid-state intercalation and polymerization of carbazole (Cz) in the basal spacings of Bentonite.
The intercalation of cetyl pyridinium chloride (CPCl), a cationic surfactant, and naphthalene sulfonic acid (NSA), an anionic
surfactant, in Bentonite was carried out at two loadings—25 and 50 wt%—using microwave irradiation. The in situ polymerization
of Cz was successfully carried out into the surfactant-modified galleries of Bentonite. This was confirmed by Gel permeation
chromatography (GPC). The intercalation of poly(carbazole) (PCz) was confirmed by FT-IR, UV–Visible, and XRD analyses. Although
polymerization was carried out in the solid-state, the UV–Visible spectra revealed the doped state of PCz and the presence
of a charge carrier tail. The XRD studies showed that the increase in the height of the galleries was higher in case of Bentonite/CPCl/PCz
nanocomposites as compared to Bentonite/NSA/PCz nanocomposites. It also revealed different orientations of the two surfactants
in the galleries of the clay. The average particle size of Bentonite/CPCl/PCz (1:0.25:0.25) and (1:0.5:0.5) nanocomposites
was found to be in the range of 25–35 and 50–60 nm, respectively. The Bentonite/NSA/PCz (1:0.25:0.25) and (1:0.5:0.5) nanocomposites
showed the average particle size in the range of 20–30 nm and 40–50 nm, respectively. The results revealed that both cationic
and anionic surfactants strongly influenced the morphology of Bentonite/PCz nanocomposites. The difference in the mechanisms
of solid-state intercalation of PCz in the presence of these surfactants has been proposed. 相似文献
134.
Nisha Sharma Amiya K. Pani Kapil K. Sharma 《Advances in Computational Mathematics》2018,44(5):1537-1571
In this paper, an expanded mixed finite element method with lowest order Raviart Thomas elements is developed and analyzed for a class of nonlinear and nonlocal parabolic problems. After obtaining some regularity results for the exact solution, a priori error estimates for the semidiscrete problem are established. Based on a linearized backward Euler method, a complete discrete scheme is proposed and a variant of Brouwer’s fixed point theorem is used to derive an existence of a fully discrete solution. Further, a priori error estimates for the fully discrete scheme are established. Finally, numerical experiments are conducted to confirm our theoretical findings. 相似文献
135.
Dr. Ashley J. Winter Dr. R. Nisha Khanizeman Dr. Abigail M. C. Barker-Mountford Dr. Andrew J. Devine Dr. Luoyi Wang Dr. Zhongshu Song Dr. Jonathan A. Davies Prof. Paul R. Race Dr. Christopher Williams Prof. Thomas J. Simpson Prof. Christine L. Willis Prof. Matthew P. Crump 《Angewandte Chemie (International ed. in English)》2023,62(47):e202312514
Mupirocin is a clinically important antibiotic produced by a trans-AT Type I polyketide synthase (PKS) in Pseudomonas fluorescens. The major bioactive metabolite, pseudomonic acid A (PA−A), is assembled on a tetrasubstituted tetrahydropyran (THP) core incorporating a 6-hydroxy group proposed to be introduced by α-hydroxylation of the thioester of the acyl carrier protein (ACP) bound polyketide chain. Herein, we describe an in vitro approach combining purified enzyme components, chemical synthesis, isotopic labelling, mass spectrometry and NMR in conjunction with in vivo studies leading to the first characterisation of the α-hydroxylation bimodule of the mupirocin biosynthetic pathway. These studies reveal the precise timing of hydroxylation by MupA, substrate specificity and the ACP dependency of the enzyme components that comprise this α-hydroxylation bimodule. Furthermore, using purified enzyme, it is shown that the MmpA KS0 shows relaxed substrate specificity, suggesting precise spatiotemporal control of in trans MupA recruitment in the context of the PKS. Finally, the detection of multiple intermodular MupA/ACP interactions suggests these bimodules may integrate MupA into their assembly. 相似文献