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101.
Reactions of (-)-carvone with aliphatic, aromatic, heterocyclic, and functional thiols, catalyzed with potassium carbonate, gave the corresponding derivatives in high yields. Isopropyl mercaptan, 2-mercaptoethanol, furfuryl mercaptan, and N-acetylcysteine add across the endocyclic double bond of (-)-carvone with the predominant formation of the isomers with the S configuration of C3, whereas addition of hexadecyl mercaptan and 1,2-ethanedithiol mainly yields the R isomers. 相似文献
102.
The kinetics of free glucose-6-phosphate dehydrogenase (G-6-PDH), biotinylated G-6-PDH, and biotinylated G-6-PDH complexed
with avidin were investigated. The kinetics of the free enzyme were consistent with a sequential rather than a ping-pong mechanism.
The kinetics of the biotinylated enzyme were similar to that of the free enzyme, but the kinetic constants were different;
theK
m value for NADP was halved, whereas theK
m for G-6-P decreased only slightly. In the presence of avidin, theK
m of biotinylated G-6-PDH for G-6-P nearly doubled whereas theK
m for NADP did not change significantly. Avidin complexed with biotinylated G-6-PDH inhibited the enzyme from acting. Based
upon these reactions, it was possible to devise assays for either free biotin or free avidin using biotinylated G-6-PDH as
the indicator enzyme. Concentrations of biotin between 40 and 60 mg/mL, or of 25–95 Μg/mL of avidin could be measured within
2 min through the use of biotinylated G-6-PDH. 相似文献
103.
Raquel Gutirrez-Climente Margaux Clavi Jrmie Gouyon Giang Ngo Yoann Ladner Pascal Etienne Pascal Dumy Pierre Martineau Martine Pugnire Catherine Perrin Gilles Subra Ahmad Mehdi 《Molecules (Basel, Switzerland)》2021,26(19)
Ordered mesoporous materials and their modification with multiple functional groups are of wide scientific interest for many applications involving interaction with biological systems and biomolecules (e.g., catalysis, separation, sensor design, nano-science or drug delivery). In particular, the immobilization of enzymes onto solid supports is highly attractive for industry and synthetic chemistry, as it allows the development of stable and cheap biocatalysts. In this context, we developed novel silylated amino acid derivatives (Si-AA-NH2) that have been immobilized onto SBA-15 materials in biocompatible conditions avoiding the use of toxic catalyst, solvents or reagents. The resulting amino acid-functionalized materials (SBA-15@AA) were characterized by XRD, TGA, EA, Zeta potential, nitrogen sorption and FT-IR. Differences of the physical properties (e.g., charges) were observed while the structural ones remained unchanged. The adsorption of the enzyme lysozyme (Lyz) onto the resulting functionalized SBA-15@AA materials was evaluated at different pHs. The presence of different functional groups compared with bare SBA-15 showed better adsorption results, for example, 79.6 nmol of Lyz adsorbed per m2 of SBA-15@Tyr compared with the 44.9 nmol/m2 of the bare SBA-15. 相似文献
104.
A.T. Ngo P. Bonville M.P. Pileni 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(4):583-592
By using oil in water micelles, cobalt ferrite particles having an average diameter around 3 nm were synthetised. These nanoparticles
are characterized by the presence of cation vacancies and no Fe(II) is observed, as it has been described in literature previously.
Chemical interfacial treatment allows to coat the particles with citrate derivatives. The magnetic properties of uncoated
and coated particles strongly diluted in a polymer substrate are compared by magnetization measurements and 57Fe M?ssbauer spectroscopy. The anisotropy constant is shown to be independent of coating, whereas the magnetization is found
to be larger in the uncoated particles.
Received 3 February 1998 相似文献
105.
Ngo Van Nong 《Solid State Communications》2006,139(5):232-234
Polycrystalline samples of (Ca1−xRx)3Co2O6 with R = Gd, Tb, Dy and Ho at x=0-0.1 were synthesized and the effects of rare earth substitution on their thermoelectric properties were investigated. In the high-temperature region, the rare earth substitution resulted in an increase in the Seebeck coefficients (S), and the S values increased with decreasing ionic radius of rare earth elements in the order Gd3+>Tb3+>Dy3+>Ho3+. In contrast, the influence of rare earth substitution on the electrical resistivity was small. The high-temperature power factor was thereby improved by the late rare earth substitutions, particularly those with Ho3+ for Ca2+. For the Ho-doped samples (x≤0.05), the power factor was significantly improved by increasing Ho concentration. 相似文献
106.
R.T. Zheng N.Q. Ngo L.N. Binh S.C. Tjin J.L. Yang 《Applied physics. B, Lasers and optics》2006,82(1):59-63
We present the design and development of piece-wise stepped-chirp fiber Bragg gratings (FBGs) with arbitrary group delay responses
using a uniform phase mask in a pre-stretched fiber. The method involves writing a series of sub-gratings on a pre-stretched
fiber whose length is varied during the UV exposure process. Two motorized stages are employed to control the length of the
pre-stretched fiber in order to adjust the grating pitch at each writing step to achieve piece-wise stepped chirping of the
FBG. To demonstrate the effectiveness of the method to produce chirped FBGs with arbitrary group delay responses, a linear-chirp
FBG and a quadratic-chirp FBG were fabricated, and their measured performances agree well with analytical predictions.
PACS 42.81.-i; 42.79.Dj; 42.79.Ci 相似文献
107.
J. Zhou W.H. Wong N.Q. Ngo E.Y.B. Pun Y.Q. Shen Y.X. Zhao 《Optics & Laser Technology》2005,37(6):427-431
Polymeric optical waveguides based on a new synthesized bisphenol A–aldehyde polymer (PA-1 resin) have been fabricated using photolithography and reactive ion etching technique. The polymer is novel with relatively high refractive index, low birefringence and absorption at the optical communication wavelengths. The single-mode channel waveguides exhibit a propagation loss of 0.41±0.05 dB/cm at a wavelength of and 0.5±0.05 dB/cm at for both the TE and TM polarizations. The polarization-dependent loss of the waveguides is 0.1±0.05 dB/cm at these wavelengths. 相似文献
108.
109.
We propose a new method for the development of a tunable optical bandpass filter (TOBF) based on a linearly chirped fiber Bragg grating (LCFBG). A NiCr wire heater is used to heat the LCFBG at a small point to introduce a narrow passband within the stop band of the LCFBG. The central wavelength of the passband is tuned by scanning the wire heater along the LCFBG. As an example demonstrating the effectiveness of the proposed method, we demonstrate a TOBF with a very small 3-dB bandwidth of approximately 7 pm, a tuning range of 16.4 nm, and a rejection ratio of more than 25 dB. Compared with previously reported tunable-fiber-based bandpass filters, this method provides the advantages of a large tuning range, continuous tunability, a switchable passband, a simple tuning mechanism, low cost, and narrow bandwidth. 相似文献
110.