A green and facile synthesis of dithiocarbamate derivatives containing disulfide linkage by the ring opening reaction of trithiocarbonate with amines under solvent and catalyst‐free condition with excellent yields is being reported. Environmental benignity, easy work up, smaller reaction time, and lack of column chromatography are the significant features of this protocol. The cyclic trithiocarbonate ( 1 ) has been used as a starting material for the first time to synthesize compounds of biological interest ( 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h , 3i , 3j , 3k , 3l , 3m , 3n , 3o , 3p , 3q ). 相似文献
Excitation energy transfer between the dye pair acriflavine (donor) to rhodamine-6G (acceptor) in various polymers [polyvinyl alcohol (PVA), cellulose acetate, and polymethyl methacrylate (PMMA)] was studied using steady-state and time-resolved fluorescence spectroscopy at room temperature. In all these polymers, at higher acceptor concentrations, direct energy transfer from acriflavine to rhodamine-6G followed the F?rster theory, which is indicated by the agreement in the values of the observed critical transfer distance with that calculated from spectral overlap. On the other hand, at low acceptor concentrations, the excitation energy migration influences the kinetics, resulting in a significantly higher value of the observed critical transfer distance, which is explained on the basis of Loring et al. (Loring, R. F.; Anderson, H. C.; Fayer, M. D. J. Chem. Phys. 1984, 80, 5731-5744) and Huber (Huber, D. L. Phys. Rev. B: Condens. Matter Mater. Phys. 1979, 20 2307-2314) theories. It was observed that the spectral overlap for donor-donor transport (excitation migration) and donor-acceptor transfer (energy transfer) and thereby other energy transfer parameters were influenced by the microenvironment of the polymers. The efficiency of energy transfer (eta) was the highest in PMMA and the lowest in PVA. Further, the study of acceptor dynamics under energy transfer showed that the rise time of the acceptor also depends on the nature of the polymer microenvironment. 相似文献
The Organisation for the Prohibition of Chemical Weapons (OPCW) has been organising and conducting Official Proficiency Tests (PT) since 1996 in accordance with ILAC-G13 to certify laboratories for the analysis of authentic samples under the provision of Chemical Weapons Convention. The tests are part of a mechanism to ensure that there are laboratories that have proven competence in the analysis of chemicals related to the Convention. Laboratories that have successfully completed the tests are designated by the Director General of the OPCW for analysis of authentic samples. To maintain the Designated Laboratory status, a laboratory must take and pass at least one of the two proficiency tests offered per calendar year. Unlike many proficiency tests, the OPCW PT is qualitative, that is the laboratories must determine if any of a very large set (essentially infinite) of chemicals relevant to the Convention are present in the samples. The tests are organised with the assistance of two laboratories, one preparing the test samples, and the other evaluating the test results. The paper provides an overview of the current status of these PTs and outlines salient features regarding procedure and scope of tests, selection of assisting laboratories, scoring and performance rating of participating labs. The emerging issues are also briefly discussed. 相似文献
The linear syntheses of 4'-C-aminomethyl-2'-O-methyl uridine and cytidine nucleoside phosphoramidites were achieved using glucose as the starting material. The modified RNA building blocks were incorporated into small interfering RNAs (siRNAs) by employing solid phase RNA synthesis. Thermal melting studies showed that the modified siRNA duplexes exhibited slightly lower T(m) (~1 °C/modification) compared to the unmodified duplex. Molecular dynamics simulations revealed that the 4'-C-aminomethyl-2'-O-methyl modified nucleotides adopt South-type conformation in a siRNA duplex, thereby altering the stacking and hydrogen-bonding interactions. These modified siRNAs were also evaluated for their gene silencing efficiency in HeLa cells using a luciferase-based reporter assay. The results indicate that the modifications are well tolerated in various positions of the passenger strand and at the 3' end of the guide strand but are less tolerated in the seed region of the guide strand. The modified siRNAs exhibited prolonged stability in human serum compared to unmodified siRNA. This work has implications for the use of 4'-C-aminomethyl-2'-O-methyl modified nucleotides to overcome some of the challenges associated with the therapeutic utilities of siRNAs. 相似文献
Kinetics of oxidation of six aliphatic aldehydes by Os(VIII) in alkaline solutions have been studied. The reaction is of first order with respect to each of the aldehyde and Os(VIII). The pseudo-first order rate constants decreased with an increase in the concentration of hydroxyl ions. The oxidation of deuterioacetaldehyde (MeCDO) exhibited a substantial primary kinetic isotope effect. Separate rate constants for the oxidation of hydrate and free aldehyde forms have been evaluated. The aldehyde hydrate is postulated as the active reductant. Ionic strength has no noticable effect on the rate. The rate-determining step is, therefore, postulated to be a bimolecular reaction between the aldehyde hydrate and [OsO4(OH)2]?2. The value of the limiting rate constant exhibited an excellent correlation with Taft σ* values; reaction constant being negative. A mechanism involving transfer of a hydride ion from the aldehyde hydrate to Os(VIII) has been proposed. 相似文献
A nanoporous coordination polymer (NPCP) was prepared from palladium(II) chloride and 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole and is shown to act as a peroxidase mimetic. It can catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 which is formed on enzymatic oxidation of glucose by glucose oxidase. Based on these findings, a sensitive glucose test was worked out at 652 nm where the intensity if the greenish-blue product is related to the actual concentration of glucose. Figures of merit include (a) rather low Km value (30 μM) which evidences the strong binding affinity of the NPCP toward glucose, (b) a high v(max) (8.5 M·s?1), (c) a 47 nM detection limit, (d) a lifetime of a month, (e) a wide working pH range (2–10), and (f) a 25–80 °C temperature range. The assay was applied to non-invasive determination of glucose assay in tear, saliva where the detection limits are found to be 61 and 91 nM, respectively.
Graphical abstract DSchematic of the mechanism of the peroxidase like catalytic activity of AHMT-Pd NPCP that was applied in a selective colorimetric method for glucose detection based on TMB oxidation in the presence of enzymatically generated H2O2.
The dielectric dispersion and absorption spectra of formamide (FA), N,N-dimethylformamide (DMF) and their binary mixtures are investigated in the frequency range of 500 MHz to 20 GHz at 30 °C in view of the organic synthesis by microwaves heating using amides solvents. The concentration dependent values of molecular reorientation relaxation times lower than that of the ideal mixing behaviour have been attributed to the cooperative dynamics of H-bonded FA–DMF structures. The molar ratio of stable adduct is 2:1 of FA to the DMF, which is determined from the concentration dependent excess static dielectric constant and the relaxation time plots of these binary mixtures. Electrode polarization effect and ionic conduction in FA and DMF were investigated from their dielectric dispersion spectra in the low frequency region of 20 Hz to 1 MHz. 相似文献