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Beulen MW Bugler J de Jong MR Lammerink B Huskens J Schonherr H Vancso GJ Boukamp BA Wieder H Offenhauser A Knoll W van Veggel FC Reinhoudt DN 《Chemistry (Weinheim an der Bergstrasse, Germany)》2000,6(7):1176-1183
We have developed synthesis routes for the introduction of short and long dialkylsulfides onto the primary side of alpha-, beta-, and gamma-cyclodextrins. Monolayers of these cyclodextrin adsorbates were characterized by electrochemistry, wettability studies, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and atomic force microscopy (AFM). The differences in thickness and polarity of the outerface of the monolayers were measured by electro-chemistry and wettability studies. On average about 70% of the sulfide moieties were used for binding to the gold, as measured by XPS. Tof-SIMS measurements showed that the cyclodextrin adsorbates adsorb without any bond breakage. AFM measurements revealed for beta-cyclodextrin monolayers a quasi-hexagonal lattice with a lattice constant of 20.6 A, which matches the geometrical size of the adsorbate. The alpha-cyclodextrin and gamma-cyclodextrin monolayers are less ordered. Interactions of the anionic guests 1-anilinonaphthalene-8-sulfonic acid (1,8-ANS) and 2-(p-toluidinyl)naphthalene-6-sulfonic acid (2,6-TNS) and the highly ordered monolayers of heptapodant beta-cyclodextrin adsorbates were studied by surface plasmon resonance (SPR) and electrochemical impedance spectroscopy. The SPR measurements clearly showed interactions between a beta-cyclodextrin monolayer and 1,8-ANS. Electrochemical impedance spectroscopy measurements gave high responses even at low guest concentrations (< or = 5 microM). The association constant for the binding of 1,8-ANS (K = 289,000 +/- 13,000M-1) is considerably higher than the corresponding value in solution. (Partial) methylation of the secondary side of the beta-cyclodextrin strongly decreases the binding. 相似文献
34.
A highly selective and efficient method for the unmasking of p-methoxybenzyl (PMB) ethers and esters has been developed by use of 20 mol % of zirconium(IV) chloride as Lewis acid in acetonitrile. The present method is very fast, and the conditions are tolerable to a variety of acid/base-sensitive protecting groups and substrates such as carbohydrates, terpenes, and amino acids. The products are obtained in good to high yields. 相似文献
35.
Kosuri MR Cone R Li Q Han SM Bunker BC Mayer TM 《Langmuir : the ACS journal of surfaces and colloids》2004,20(3):835-840
We have investigated the liquid-phase self-assembly of 1-alkanethiols (HS(CH2)n-1CH3, n = 8, 16, and 18) on hydrogenated Ge(111), using attenuated total reflection Fourier transform infrared spectroscopy as well as water contact angle measurements. The infrared absorbance of C-H stretching modes of alkanethiolates on Ge, in conjunction with water contact angle measurements, demonstrates that the final packing density is a function of alkanethiol concentration in 2-propanol and its chain length. High concentration and long alkyl chain increase the steady-state surface coverage of alkanethiolates. A critical chain length exists between n = 8 and 16, above which the adsorption kinetics is comparable for all long alkyl chain 1-alkanethiols. The steady-state coverage of hexadecanethiolates, representing long-chain alkanethiolates, reaches a maximum at approximately 5.9 x 10(14) hexadecanethiolates/cm2 in 1 M solution. The characteristic time constant to reach a steady state also decreases with increasing chain length. This chain length dependence is attributed to the attractive chain-to-chain interaction in long-alkyl-chain self-assembled monolayers, which reduces the desorption-to-adsorption rate ratio (kd/ka). We also report the adsorption and desorption rate constants (ka and kd) of 1-hexadecanethiol on hydrogenated Ge(111) at room temperature. The alkanethiol adsorption is a two-step process following a first-order Langmuir isotherm: (1) fast adsorption with ka = 2.4 +/- 0.2 cm3/(mol s) and kd = (8.2 +/- 0.5) x 10(-6)(s-1); (2) slow adsorption with ka = 0.8 +/- 0.5 cm3/(mol s) and kd = (3 +/- 2) x 10(-6) s(-1). 相似文献
36.
Madhava B. Mallia Anupam Mathur Rohit Sharma Chandan Kumar H. D. Sarma Sharmila Banerjee Ashutosh Dash 《Journal of Radioanalytical and Nuclear Chemistry》2018,317(3):1203-1210
Conventional 99mTc-radiopharmaceuticals for the detection of tumor hypoxia generally possess a single nitroimidazole moiety. Herein, we report the synthesis and evaluation of a 99mTc-complex with three-nitroimidazole moieties in an attempt to improve hypoxic cell detection. Isocyanide derivative of metronidazole (MetroNC) was synthesized and subsequently radiolabeled with [99mTc(CO)3(H2O)3]+ precursor complex, wherein the three labile water molecules were replaced with MetroNC ligand to form a pseudo-octahedral [99mTc(CO)3(MetroNC)3]+ complex. Analysis of corresponding Re(CO)3-analog prepared in macroscopic scale confirmed the formation of expected complex. Cyclic voltammetric studies of [Re(CO)3(MetroNC)3]+ complex showed no significant change in single-electron reduction potential (SERP) of MetroNC ligand (??0.96 V) upon forming the [Re(CO)3(MetroNC)3]+ complex (??0.90 V). In vitro studies in Chinese hamster ovary (CHO) cells showed three-fold preferential accumulation of [99mTc(CO)3(MetroNC)3]+ complex in hypoxic cells over normoxic cells. Biodistribution studies of [99mTc(CO)3(MetroNC)3]+ complex in Swiss mice bearing fibrosarcoma tumor showed tumor uptake and steady retention till 60 min post injection. Present study constitutes a novel design approach towards development of a 99mTc-radiopharmaceutical for hypoxia imaging application, which could be extended to other potential nitroimidazole ligands. 相似文献
37.
L. Madhava Reddy V. Veerabadra Reddy V. Satteyyanaidu J.K. Lakshmi Ch. Krishna Reddy B.V. Subba Reddy 《Tetrahedron letters》2018,59(12):1084-1086
A tandem Prins strategy has been developed for the synthesis of 1,8-dioxa 3-azaspiro[4.5]dec-2-ene derivatives using 5?mol% Cu(OTf)2 in dichloromethane at 0?°C under mild reaction conditions in short reaction times. This method provides the products in good yields with a diverse substitution pattern. 相似文献
38.
Yadav P Madhava Rao BS Batchelor SN O'Neill P 《The journal of physical chemistry. A》2005,109(10):2039-2042
Rate constants are reported for the 1-electron reduction of the azo dye Orange II in water (pH 7.0) by 10 different alpha-hydroxy radicals. The radicals were created by pulse radiolysis of aqueous solutions of the corresponding alcohol/sugar. The rate constants varied from 1 x 10(8) to 2.7 x 10(9) mol(-1) dm(3) s(-1) and radicals with beta-hydroxy groups had the lowest rate constant. The reaction was found to be controlled by the reduction potentials of the radicals, with steric influences having little effects. Good fits of the data were obtained using the Marcus equation with lambda =140 kJ/mol. 相似文献
39.