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161.
《Magnetic resonance in chemistry : MRC》2003,41(11):959-961
17O‐enriched acetic acid (2.5% in 17O) was synthesized by hydrolysis of acetic anhydride with 17O‐enriched water. The reaction was monitored by 17O and 1H NMR spectroscopy. Acetic anhydride, 17O‐enriched in both the ether and the carbonyl oxygens, was observed as an intermediate. This can be ascribed to competition between acetic acid and water for nucleophilic attack on acetic anhydride. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
162.
163.
Hongping Wei Yan Kang Zhi-ping Zhang Zong-qiang Cui Yafeng Zhou 《International journal of environmental analytical chemistry》2013,93(13):947-956
The activity of Botulinum neurotoxin type A (BoNT A) can be measured by monitoring the toxin's endopeptidase reaction with its peptide substrate. In this report, a sensitive and simple capillary electrophoresis (CE) method for analysing BoNT A activity was developed using a peptide substrate labelled with Fluorescein isothiocynate (FITC) at the N-terminal and biotin at the C-terminal. This dual labelling enables not only highly sensitive laser induced fluorescence (LIF) detection of the reaction product, but also good analytical separation of the product from the peptide substrate by Micellar Electrokinetic Chromatography (MEKC). The separation between the product peak and the substrate peak was approximately 5 min using the dual-labelled substrate, while just about 1 min using the FITC-labelled substrate without biotinylation. Using the current assay method, BoNT A with concentration as low as 0.1 ng ml?1 (3.6 U mL?1 in mouse LD50) in water was detected with a S:N ratio of 3 (RSD <19%) and a linear range of four orders of magnitude. With CE's advantages of very small sample volume needed, this method may find particular applications as in assays of BoNT A activity in water samples and kinetic analyses of toxin activity. 相似文献
164.
M. N. M. van Lieshout 《Annals of the Institute of Statistical Mathematics》2006,58(2):235-259
We propose a new summary statistic for marked point patterns. The underlying principle is to compare the distance from a marked
point to the nearest other marked point in the pattern to the same distance seen from an arbitrary point in space. Information
about the range of interaction can be inferred, and the statistic is well-behaved under random mark allocation. We develop
a range of Hanisch style kernel estimators to tackle the problems of exploding tail variance earlier associated with J-function plug-in estimators, and carry out an exploratory analysis of a forestry data set. 相似文献
165.
Iliya Bouyukliev 《Discrete Applied Mathematics》2006,154(12):1693-1708
All binary projective codes of dimension up to 6 are classified. Information about the number of the codes with different minimum distances and automorphism group orders is given. 相似文献
166.
167.
《Helvetica chimica acta》2017,100(12)
Due to the biological complexity of the N‐methyl‐d ‐aspartate receptor (NMDAR ), the development of a positron emission tomography radiotracer for the imaging of NMDAR has met with limited success. Recent studies have established the presence of GluN2A subunit of the NMDAR in the heart and its role in the regulation of intracellular calcium levels. In our efforts to develop an imaging agent for the GluN2A subunit, we designed three new compounds based on a quinoxaline scaffold. The synthesis of the analogues was based on a two‐step Kabachnik–Fields reaction in sequence with Suzuki cross‐coupling and acid hydrolysis. They exhibited comparable high binding affinity values below 5 nm . A two‐step radiolabeling procedure was successfully developed for the synthesis of [18F] 1 . [18F] 1 was obtained in a modest overall radiochemical yield of 5.5 ± 4.2%, a good specific radioactivity of 254 ± 158 GBq/μmol, and a radiochemical purity > 99%. While compounds 2 and 3 showed comparable binding affinity towards NMDAR , sluggish radiolabeling, prevented their further evaluation. For [18F] 1 , in vitro autoradiography on rat heart slices demonstrated heterogeneous but unspecific accumulation, whereas for the brain a high in vitro specificity towards NMDAR , could be demonstrated. 相似文献
168.
Due to the considerable scientific and commercial interest in poly(ethylene glycol) (PEG) grafted solid surfaces for biomedical applications, it is important to characterize the properties and behaviour of these modified surfaces. In this study, we applied a unique method to predict the magnitude of interactive forces exerted between a globular protein and PEG-grafted matrices. Carboxyl functionalized solid matrices were covalently grafted with PEG-amine derivatives at varying PEG surface concentrations and layer thicknesses by controlling the grafting reaction parameters. X-ray photoelectron spectroscopy was used to characterize these PEG-grafted matrices using the standard overlay model. A detailed and systematic correlation between PEG layer thickness and the distance between the grafted PEG chains resulted in valuable information regarding protein interactions with these PEG-grafted matrices. Finally, this predicted interaction behaviour was validated with fluorescent images obtained from fluorescein isothiocyanate-labelled Cytochrome c-conjugated solid matrices using confocal laser scanning microscopy. 相似文献
169.
Ioannis D. Petsalakis Giannoula Theodorakopoulos Anna Grochol Pawel Kowalczyk Wodzimierz Jastrzebski 《Chemical physics》2009,362(3):130-134
Theoretical multireference configuration interaction (MRDCI) calculations on the excited 1Σ+ and 1Π states of NaLi are presented. They improve the results of a previous study by two of the present authors, resolve some differences with other theoretical results and lead to overall good agreement with experimental observations. To extend the experimental data base of electronic states in NaLi, a previously unknown 1Σ+ state is investigated by polarisation labelling spectroscopy. Comparison with accompanying and previous theoretical calculations leads to a conclusion that the observed system consists of two band systems switching smoothly from one adiabatic state to the other and allows assignment of the bands as 51Σ+ ← X1Σ+ in the lower energy part and to 61Σ+ ← X1Σ+ for higher energies. 相似文献
170.
We investigate the following modification of the well-known irregularity strength of graphs. Given a total weighting w of a graph G=(V,E) with elements of a set {1,2,…,s}, denote wtG(v)=∑evw(e)+w(v) for each vV. The smallest s for which exists such a weighting with wtG(u)≠wtG(v) whenever u and v are distinct vertices of G is called the total vertex irregularity strength of this graph, and is denoted by . We prove that for each graph of order n and with minimum degree δ>0. 相似文献