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1.
Dr. Desmond MacLeod Carey Dr. Tatiana Gomez Dr. Cesar Morales-Verdejo Dr. Alvaro Muñoz-Castro 《ChemistryOpen》2015,4(5):651-655
The complexation of metal cations into a host–guest situation is particularly well exemplified by [2.2.2]paracyclophane and AgI, which leads to a strong cation–π interaction with a specific face of the host molecule. Through this study we sought a deeper understanding of the effects the metal center has on the NMR spectroscopic properties of the prototypical organic host, generating theoretical reasons for the observed experimental results with an aim to determine the role of the cation–π interaction in a host–guest scenario. From an analysis of certain components of the induced magnetic field and the 13C NMR shielding tensor under its own principal axis system (PAS), the local and overall magnetic behavior can be clearly described. Interestingly, the magnetic response of such a complex exhibits a large axis-dependent behavior, which leads to an overall shielding effect for the coordinating carbon atoms and a deshielding effect for the respective uncoordinated counterparts, evidence that complements previous experimental results. This proposed approach can be useful to gain further insight into the local and overall variation of NMR shifts for host–guest pairs involving both inorganic and organic hosts. 相似文献
2.
Aliyu D. Mohammed Desmond A. Young Hermanus C. M. Vosloo 《Research on Chemical Intermediates》2017,43(4):2187-2200
Glycerol acrylate (GA) is synthesised by an acryloylation reaction with acryloyl chloride. An ester was used as a cross-linking agent at varying proportions in the synthesis of poly acrylic acid (PAA). The amount of cross-linking density in the product (GA-PAA) and degree of neutralisation determine the absorbency of the polymer samples. A sample of GA-PAA containing 0.8 % GA was discovered to absorb 395 and 66 g/g of water and saline solution, respectively. Different solvent uptakes were tested with the sample showing varying capacity for different solvents. The temperature of the reaction was maintained at 60 °C and a reaction time of 2½ h. FTIR, TGA, SEM and XRD analyses were used to characterise the products. 相似文献
3.
For the work on the synthesis of 2-acyl-5-methoxynaphthoquinones as tricyclic analogues of daunomycinone1, we wanted to develop an efficient regioselective synthesis of 5-methoxy-2-acyl-1-naphthols without using Lewis acids. This requirement precluded the use of the thermal Fries but not the photo-Fries rearrangement. Although the mechanistic aspects of the photo reaction have received much study2, the reaction has been little used preparatively3 because it usually gives poor yields of hydroxy ketones even when only one product is possible. 相似文献
4.
Glycoproteins are produced by the post‐translational modification process of proteins and they play an important role in mediating various biological processes. Our understanding towards biochemical functions of individual glycoproteins has been seriously hampered due to the heterogeneous expression of carbohydrate parts in glycoproteins. Despite the advancement in recombinant expression and chromatographic techniques, the isolation of pure glycoforms remains nearly impossible. To obtain homogenous glycoproteins, tremendous efforts hves been spent in developing various ligation and glycosylation techniques. This minireview discusses selected methods for the preparation and ligation of glycopeptides. The importance of the development of new chemical synthesis method for glycoproteins has also been discussed, which would be one of the next directions in this field. 相似文献
5.
Muchena J. Kailemia Melvin Park Desmond A. Kaplan Andre Venot Geert-Jan Boons Lingyun Li Robert J. Linhardt I. Jonathan Amster 《Journal of the American Society for Mass Spectrometry》2014,25(2):258-268
High-field asymmetric waveform ion mobility spectrometry (FAIMS) is shown to be capable of resolving isomeric and isobaric glycosaminoglycan negative ions and to have great utility for the analysis of this class of molecules when combined with Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and tandem mass spectrometry. Electron detachment dissociation (EDD) and other ion activation methods for tandem mass spectrometry can be used to determine the sites of labile sulfate modifications and for assigning the stereochemistry of hexuronic acid residues of glycosaminoglycans (GAGs). However, mixtures with overlapping mass-to-charge values present a challenge, as their precursor species cannot be resolved by a mass analyzer prior to ion activation. FAIMS is shown to resolve two types of mass-to-charge overlaps. A mixture of chondroitin sulfate A (CSA) oligomers with 4–10 saccharides units produces ions of a single mass-to-charge by electrospray ionization, as the charge state increases in direct proportion to the degree of polymerization for these sulfated carbohydrates. FAIMS is shown to resolve the overlapping charge. A more challenging type of mass-to-charge overlap occurs for mixtures of diastereomers. FAIMS is shown to separate two sets of epimeric GAG tetramers. For the epimer pairs, the complexity of the separation is reduced when the reducing end is alkylated, suggesting that anomers are also resolved by FAIMS. The resolved components were activated by EDD and the fragment ions were analyzed by FTICR-MS. The resulting tandem mass spectra were able to distinguish the two epimers from each other. Figure
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6.
In this article active non-linear optical effects in semiconductors are reviewed. These processes arise because of the dynamics of excited populations of charge carriers temporarily created in otherwise empty states when a beam of laser radiation is incident on the material. A large number of different effects have been observed in different semiconductor materials recently and the non-linearities cover a wide range of magnitudes both in time-scale and size of non-linearity. The theory and physical concepts relevant to these processes are described and experimental observations using both high power pulsed and low power c.w. lasers are reviewed. Applications in optical bistability, phase conjugation, optical gating and optoelectronic gating are discussed. 相似文献
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An efficient procedure for the oxidation of acetophenone to phenylglyoxal and its subsequent in situ conversion to the title compound is described herein. 相似文献
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