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排序方式: 共有163条查询结果,搜索用时 31 毫秒
81.
Filali M Meier MA Schubert US Gohy JF 《Langmuir : the ACS journal of surfaces and colloids》2005,21(17):7995-8000
Gold nanoparticles of improved stability against aggregation were prepared using poly(ethylene oxide)-block-poly(epsilon-caprolactone) (PEO-b-PCL) star-block copolymers. A five-arm star-shaped macroinitiator (PEO) was utilized for the automated parallel controlled ring-opening polymerization of epsilon-caprolactone to prepare a series of PEO-b-PCL star-block copolymers with a constant PEO core linked to PCL blocks of variable length. The PEO core was swelled with KAuCl4 in N,N-dimethylformamide (DMF), and gold nanoparticles were subsequently obtained by reduction with NaBH4. Since the process was always templated by the same PEO core for all investigated polymers, the average dimension of the formed gold nanoparticles was in the same range for all star-block copolymers. In sharp contrast, the size distribution and long-term stability against aggregation of the gold nanoparticles dispersed in DMF were strongly dependent on the PCL block length, confirming the role of PCL blocks as stabilizing blocks for these nanoparticles. 相似文献
82.
A Novel Synthesis of 1‐Aryl‐6‐bromo‐3‐(5‐ethylthio‐4‐phenyl‐4H‐1,2,4‐triazol‐3‐yl)‐1H‐pyrazolo[4,3‐b]quinolin‐9(4H)‐ones via Thermal Cyclization of 4‐Azidopyrazoles 下载免费PDF全文
Hanadi Y. Medrasi Mariam Al‐Sheikh Kamal Usef Sadek Ramadan Ahmed Mekheimer 《Journal of heterocyclic chemistry》2016,53(4):1159-1167
2‐Aryl‐hydrazononitriles 3a , 3b , 3c were prepared by coupling 3‐ethylthio‐5‐cyanomethyl‐4‐phenyl‐1,2,4‐triazole ( 1 ) with diazonium salts 2a , 2b , 2c . Reacting 3a , 3b , 3c with both ethyl bromoacetate ( 4a ) and 4‐bromobenzyl bromide ( 4b ) in DMF, in the presence of K2CO3, at 80 °C for 3–4 h, gave the corresponding 4‐amino‐pyrazoles 6a , 6b , 6c , 6d , 6e , 6f . Diazotization of 6a , 6b , 6c , 6d , 6e , 6f , followed by reaction with NaN3, leads to the formation of 4‐azidopyrazoles 8a , 8b , 8c , 8d , 8e , 8f , a new heterocyclic ring system. Interestingly, fusion of 4‐azidopyrazoles 8d , 8e , 8f at temperature higher than their melting points with 5 °C for 2 min did not give the expected fused pyrazolo[4,3‐c]isoxazoles 9 but furnished instead the novel pyrazolo[4,3‐b]quinolinones 10a , 10b , 10c , in high yields. 相似文献
83.
Zare Abdolkarim Kohzadian Alireza Filian Hossein Nezhad Mariam Sadat Ghoreishi Karami Amirali 《Research on Chemical Intermediates》2022,48(4):1631-1644
Research on Chemical Intermediates - In this research, highly efficient protocols for the production of pyrido[2,3-d:6,5-d′]dipyrimidine and bis(pyrazolyl)methane derivatives using an acid... 相似文献
84.
Fluorescent nucleic acid base mimics serve as excellent site‐specific and real‐time reporters of the local and global dynamics. In this work, using the fluorescent guanine mimic 6‐methylisoxanthopterin (6‐MI), we unravel the differential dynamics of replication fork barrier/terminator sequences (RFB1 and RFB3) mediated by fork blocking protein (Fob1). By strategic and site‐specific incorporation of this probe, we show that 6‐MI is able to capture the changes in global dynamics exhibited by Fob1 and aids in distinguishing between varied architectural forms like double‐stranded DNA versus Holliday junctions (HJs). This is important as these barriers are hotspots for recombination. Fluorescence lifetime and anisotropy decay studies further revealed that Fob1 strongly dampens the dynamics in double‐stranded RFB1, and the sequence inherently possesses lesser flexibility in comparison to RFB3. We show that 6‐MI can probe the differential oligomeric status of Fob1 in response to various architectures, that is, double‐stranded versus HJs. This work highlights the unique advantages of 6‐MI as a probe when incorporated in nucleic acid frameworks. 相似文献
85.
Dr. Majid M. Heravi Mariam Hosseini Hossein A. Oskooie Bita Baghernejad F. Farzaneh 《中国化学》2010,28(10):2045-2048
A simple and convenient protocol is described for the preparation of polyhydroquinolines via one‐pot, multi component reaction of an aromatic aldehyde, ethylacetoacetate, ammonium acetate and dimedone using iron loaded mesoporous materials as an efficient catalyst in good yields. 相似文献
86.
Mariam Mnatsakanyan David Shock Tiffany A. Goodie Neil W. Barnett R. Andrew Shalliker 《Talanta》2010,82(4):1349-1827
Differences between alkyl, dipole-dipole, hydrogen bonding, and π-π selective surfaces represented by non-resonance and resonance π-stationary phases have been assessed for the separation of ‘Ristretto’ café espresso by employing 2DHPLC techniques with C18 phase selectivity detection. Geometric approach to factor analysis (GAFA) was used to measure the detected peaks (N), spreading angle (β), correlation, practical peak capacity (np) and percentage usage of the separations space, as an assessment of selectivity differences between regional quadrants of the two-dimensional separation plane. Although all tested systems were correlated to some degree to the C18 dimension, regional measurement of separation divergence revealed that performance of specific systems was better for certain sample components. The results illustrate that because of the complexity of the ‘real’ sample obtaining a truly orthogonal two-dimensional system for complex samples of natural origin may be practically impossible. 相似文献
87.
Mariam Khvedelidze Tamaz Mdzinarashvili Tamar Partskhaladze Noha Nafee Ulrich F. Schaefer Claus-Michael Lehr Marc Schneider 《Journal of Thermal Analysis and Calorimetry》2010,99(1):337-348
The calorimetric investigation of non-coated and chitosan-coated PLGA nanoparticles (NP) shows that at initial temperatures
of heating particle swelling takes place what results in an internal architectural change at lower than physiological temperature.
It has shown that the temperature of NP tightness perturbing depends on solvent polarity: as more polar is the solvent more
stable are particles. The break of existing bonds in NP shell is accompanied with heat absorption peak which undergoes significant
changes depending on heating rate. In the wide pH 2–8 interval in transition temperature no changes occurred. The obtained
results show that such NP could be used in acidic area for drug transfer, which gives possibility to take medicine orally.
It was shown that DNA attaches only to chitosan-coated NP. The optimal ratio for DNA loading onto the NP was found to be 7:1
(WNP/WDNA). 相似文献
88.
Niers JM Chen JW Lewandrowski G Kerami M Garanger E Wojtkiewicz G Waterman P Keliher E Weissleder R Tannous BA 《Journal of the American Chemical Society》2012,134(11):5149-5156
We have developed a multifaceted, highly specific reporter for multimodal in vivo imaging and applied it for detection of brain tumors. A metabolically biotinylated, membrane-bound form of Gaussia luciferase was synthesized, termed mbGluc-biotin. We engineered glioma cells to express this reporter and showed that brain tumor formation can be temporally imaged by bioluminescence following systemic administration of coelenterazine. Brain tumors expressing this reporter had high sensitivity for detection by magnetic resonance and fluorescence tomographic imaging upon injection of streptavidin conjugated to magnetic nanoparticles or fluorophore, respectively. Moreover, single photon emission computed tomography showed enhanced imaging of these tumors upon injection with streptavidin complexed to (111)In-DTPA-biotin. This work shows for the first time a single small reporter (~40 kDa) which can be monitored with most available molecular imaging modalities and can be extended for single cell imaging using intravital microscopy, allowing real-time tracking of any cell expressing it in vivo. 相似文献
89.
Rauf MA Graham JP Bukallah SB Al-Saedi MA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,72(1):133-137
The absorption and fluorescence spectra of Rose Bengal dye were studied in various solvents. It was found that solvent effects on the absorption wavelength are consistent with the solvatochromic model of Kamlet, Abboud and Taft. The solvent polarizability value pi* was found to have a linear relationship with the absorption wavelength of the dye in various solvents. Additionally, the normalized transition energy value (E(T)(N)) showed some scattering when plotted versus Deltanu(af). Density functional calculations were used to assign the absorption in the region 540-570 nm to a pi-pi* transition between the HOMO and LUMO of the anion. Experimental ground state and excited state dipole moments were calculated by using the solvatochromatic shifts of absorption and fluorescence spectra as a function of the dielectric constant (epsilon) and refractive index (n). The dipole moment for Rose Bengal was found to be 1.72 Debye in the ground state, whereas this value was 2.33 Debye in the excited state. 相似文献
90.
DM Panov PV Petrovskii MG Ezernitskaya AF Smol'yakov FM Dolgushin AA Koridze 《Dalton transactions (Cambridge, England : 2003)》2012,41(32):9667-9671
Rhodium and iridium complexes of a new ferrocene-derived bis(N-heterocyclic carbene) ligand, [M(cod){1,2-(MeNCHCHNCCH(2))(2)C(5)H(3)}Fe(C(5)H(5))]BF(4) (M = Rh, 8a; M = Ir, 8b; cod = 1,5-cyclooctadiene), were synthesized from the corresponding bis(imidazolium) salt 6. The molecular structure of 8a was determined by single-crystal X-ray diffraction. Complexes 8a and 8b smoothly react with CO with displacement of the chelating cod ligand to give the corresponding dicarbonyl derivatives 9a and 9b. 相似文献