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341.
The synthesis of mono-6-(3-methylimidazolium)-6-deoxyperphenylcarbamoyl-beta-cyclodextrin chloride (MPCCD) and its application in chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC) are being reported. This chiral selector is coated onto silica gel in different weight percentages (15, 20 and 35%, w/w) to obtain CSPs having different loading content. These new chiral stationary phases are tested using normal-phase HPLC for enantioseparation of racemic aromatic alcohols. Indeed, the enantiodiscrimination abilities of these CSPs are found to be influenced by the loading content of the chiral selector. Among the three columns (MPCCD-C15, MPCCD-C20 and MPCCD-C35), the best enantioseparation results are obtained using a column containing 20% (w/w) of MPCCD (MPCCD-C20). The resolution (R(s)) obtained for p-fluorophenylethanol, p-chlorophenylethanol, p-bromophenylethanol, p-iodophenylethanol and p-fluorophenyl-3-buten-1-ol using MPCCD-C20 ranges from 3.83 to 5.65. Good enantioseparation results are obtained for these analytes under SFC separation conditions using the MPCCD-C20 column. 相似文献
342.
Dr. Jacky C. H. Chu Dr. Clarence T. T. Wong Prof. Dennis K. P. Ng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(2):e202214473
Targeted delivery and specific activation of photosensitizers can greatly improve the treatment outcome of photodynamic therapy. To this end, we report herein a novel dual receptor-mediated bioorthogonal activation approach to enhance the tumor specificity of the photodynamic action. It involves the targeted delivery of a biotinylated boron dipyrromethene (BODIPY)-based photosensitizer, which is quenched in the native form by the attached 1,2,4,5-tetrazine unit, and an epidermal growth factor receptor (EGFR)-targeting cyclic peptide conjugated with a bicycle[6.1.0]non-4-yne moiety. Only for cancer cells that overexpress both the biotin receptor and EGFR, the two components can be internalized preferentially where they undergo an inverse electron-demand Diels–Alder reaction, leading to restoration of the photodynamic activity of the BODIPY core. By using a range of cell lines with different expression levels of these two receptors, we have demonstrated that this stepwise “deliver-and-click” approach can confine the photodynamic action on a specific type of cancer cells. 相似文献
343.
The infrared (IR)-vacuum ultraviolet (VUV)-pulsed field ionization-photoelectron (IR-VUV-PFI-PE) spectrum for C2H4(X1A(g), v11 = 1, N'(Ka'Kc') = 3(03)) in the VUV range of 83,000-84,800 cm(-1) obtained using a single mode infrared laser revealed 24 rotationally resolved vibrational bands for the ion C2H4(+)(X2B(3u)) ground state. The frequencies and symmetry of the vibrational bands thus determined, together with the anharmonic frequency predictions calculated at the CCSD(T)/aug-cc-pVQZ level, have allowed the unambiguous assignment of these vibrational bands. These bands are mostly combination bands. The measured frequencies of these bands yield the fundamental frequencies for v8+ = 1103 +/- 10 cm(-1) and v10+ = 813 +/- 10 cm(-1) of C2H4(+)(X2B(3u)), which have not been determined previously. The present IR-VUV-PFI-PE study also provides truly rovibrationally selected and resolved state-to-state cross sections for the photoionization transitions C2H4(X1A(g); v11, N'(Ka'Kc')) --> C2H4(+)(X2B(3u); vi+, N+(Ka+Kc+)), where N'(Ka'Kc') denotes the rotational level of C2H4(X1A(g); v11), and vi+ and N+(Ka+Kc+) represent the vibrational and rotational states of the cation. 相似文献
344.
Li Shiuan Ng Dr. Tharishinny Raja Mogan Jinn-Kye Lee Dr. Haitao Li Dr. Chi-Lik Ken Lee Prof. Hiang Kwee Lee 《Angewandte Chemie (International ed. in English)》2023,62(47):e202313695
The production of green hydrogen through photocatalytic water splitting is crucial for a sustainable hydrogen economy and chemical manufacturing. However, current approaches suffer from slow hydrogen production (<70 μmol ⋅ gcat−1 ⋅ h−1) due to the sluggish four-electrons oxygen evolution reaction (OER) and limited catalyst activity. Herein, we achieve efficient photocatalytic water splitting by exploiting a multifunctional interface between a nano-photocatalyst and metal–organic framework (MOF) layer. The functional interface plays two critical roles: (1) enriching electron density directly on photocatalyst surface to promote catalytic activity, and (2) delocalizing photogenerated holes into MOF to enhance OER. Our photocatalytic ensemble boosts hydrogen evolution by ≈100-fold over pristine photocatalyst and concurrently produces oxygen at ideal stoichiometric ratio, even without using sacrificial agents. Notably, this unique design attains superior hydrogen production (519 μmol ⋅ gcat−1 ⋅ h−1) and apparent quantum efficiency up to 13-fold and 8-fold better than emerging photocatalytic designs utilizing hole scavengers. Comprehensive investigations underscore the vital role of the interfacial design in generating high-energy photoelectrons on surface-degenerate photocatalyst to thermodynamically drive hydrogen evolution, while leveraging the nanoporous MOF scaffold as an effective photohole sink to enhance OER. Our interfacial approach creates vast opportunities for designing next-generation, multifunctional photocatalytic ensembles using reticular chemistry with diverse energy and environmental applications. 相似文献
345.
Poulsen A William A Lee A Blanchard S Teo E Deng W Tu N Tan E Sun E Goh KL Ong WC Ng CP Goh KC Bonday Z 《Journal of computer-aided molecular design》2008,22(12):897-906
The Aurora family of serine/threonine kinases are mitotic regulators involved in centrosome duplication, formation of the
bipolar mitotic spindle and the alignment of the chromosomes along the spindle. These proteins are frequently overexpressed
in tumor cells as compared to normal cells and are therefore potential therapeutic oncology targets. An Aurora A high throughput
screen revealed a promising sub-micromolar indazole-benzimidazole lead. Modification of the benzimidazole portion of the lead
to a C2 linker with a phenyl ring was proposed to achieve novelty. Docking revealed that a conjugated linker was optimal and
the resulting compounds were equipotent with the lead. Further structure-guided optimization of substituents on the 5 & 6
position of the indazole led to single digit nanomolar potency. The homology between the Aurora A & Aurora B kinase domains
is 71% but their binding sites only differ at residues 212 & 217 (Aurora A numbering). However interactions with only the
latter residue may be used for obtaining selectivity. An analysis of published Aurora A and Aurora B X-ray structures reveals
subtle differences in the shape of the binding sites. This was exploited by introduction of appropriately sized substituents
in the 4 & 6 position of the indazole leading to Aurora B selective inhibitors. Finally we calculate the conformational energy
penalty of the putative bioactive conformation of our inhibitors and show that this property correlates well with the Aurora
A binding affinity. 相似文献
346.
Ng SH Tran N Bramnik KG Hibst H Novák P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(35):11141-11148
Li(4)V(3)O(8) materials have been prepared by chemical lithiation by Li(2)S of spherical Li(1.1)V(3)O(8) precursor materials obtained by a spray-drying technique. The over-lithiated vanadates were characterised physically by using scanning electron microscopy (SEM) and X-ray diffraction (XRD), and electrochemically using galvanostatic charge-discharge and cyclic voltammetry measurements in both the half-cell (vs. Li metal) and full-cell (vs. graphite) systems. The Li(4)V(3)O(8) materials are stable in air for up to 5 h, with almost no capacity drop for the samples stored under air. However, prolonged exposure to air will severely change the composition of the Li(4)V(3)O(8) materials, resulting in both Li(1.1)V(3)O(8) and Li(2)CO(3). The electrochemical performance of these over-lithiated vanadates was found to be very sensitive to the conductive additive (carbon black) content in the cathode. When sufficient carbon black is added, the Li(4)V(3)O(8) cathode exhibits good cycling behaviour and excellent rate capabilities, matching those of the Li(1.1)V(3)O(8) precursor material, that is, retaining an average charge capacity of 205 mAh g(-1) at 2800 mA g(-1) (8C rate; 1C rate means full charge or discharge of a battery in one hour), when cycled in the potential range of 2.0-4.0 V versus Li metal. When applied in a non-optimised full cell system (vs. graphite), the Li(4)V(3)O(8) cathode showed promising cycling behaviour, retaining a charge capacity (Li(+) extraction) above 130 mAh g(-1) beyond 50 cycles, when cycled in the voltage range of 1.6-4.0 V, at a specific current of 117 mA g(-1) (C/3 rate). 相似文献
347.
Zhou L Yang SW Ng MF Sullivan MB Tan VB Shen L 《Journal of the American Chemical Society》2008,130(12):4023-4027
We present a theoretical study on a series of novel organometallic sandwich molecular wires (SMWs), which are constructed with alternating iron atoms and cyclopentadienyl (Cp) rings, using DFT and nonequilibrium Green's function techniques. It is found that that the SMWs are stable, flexible structures having half-metallic (HM) properties with 100% negative spin polarization near the Fermi level in the ground state. Some SMWs of finite size show a nearly perfect spin filter effect (SFE) when coupled between ferromagnetic electrodes. Moreover, their I-V curves exhibit negative differential resistance (NDR), which is essential for certain electronic applications. The SMWs are the first linear molecules with HM, high SFE, and NDR and can be easily synthesized. In addition, we also analyze the underlying mechanisms via the transmission spectra and spin-dependent calculations. These findings strongly suggest that the SMWs are promising materials for application in molecular electronics. 相似文献
348.
Zhou L Zhang Y Gapter LA Ling H Agarwal R Ng KY 《Chemical & pharmaceutical bulletin》2008,56(10):1459-1462
A new lanostane-type triterpene, 29-hydroxypolyporenic acid C (8), was isolated from the dried sclerotia of Poria cocos together with eight other known compounds pachymic acid (1), dehydropachymic acid (2), 3-acetyloxy-16alpha-hydroxytrametenolic acid (3), polyporenic acid C (4), 3-epi-dehydropachymic acid (5), 3-epi-dehydrotumulosic acid (6), tumulosic acid (7), and dehydrotumulosic acid (9). The compounds were identified by spectral analysis and comparison with spectroscopic data reported in the literatures. Although none of the nine (1 to 9) compounds showed promising antioxidant activity, 1 through 6 and 8 showed good cytotoxicity against human lung cancer cell line A549 and human prostate cancer cell line DU145. Interestingly, all these compounds exhibited better cytotoxicity towards A549 than DU145 cells. 相似文献
349.
A series of photochromic spirooxazine-containing zinc(II) diimine bis-thiolate complexes were successfully synthesized, and their photophysical and photochromic properties were studied. The X-ray crystal structure of complex 1a has also been determined. Upon excitation by UV light at 330 nm, all the ligands and complexes exhibit photochromic behavior. The thermal bleaching kinetics of the ligands and the complexes were studied in dimethylformamide at various temperatures. The photochemical quantum yields for the photochromic reactions of the ligands and complexes were also determined. 相似文献
350.
Four cubane-like Cu4I4 units are assembled around an iodine atom to form the giant, mixed-valent Cu(II)Cu(I)15I17 cluster. The Cu(II)Cu(I)15I17 cluster and a bipyrazole linker form a 3D open framework with paramagnetic and thermochromic properties. This paper also touches on the resemblance of this cluster to the self-similar object of a Sierpinski tetrahedron. 相似文献