The alkylation of DNA by antitumor agents such as mechlorethamine hydrochloride (mustargen), thiophosphoramide (TSPA), mitomycin
c (MMC), bleomycin-A5 and dacarbazine (DTIC) can be detected with quartz crystal resonators (QCR). In the course of alkylation, the resonator frequency
change in polyethylene glycol (PEG)-DNA solutions follows the cross-linking of DNA and the cleavage of the sugarphosphate
backbone of DNA. It is at least partly attributed to the viscosity change of the PEG-DNA solution and possibly to some extent
to the change of mass adsorbed on the QCR surface due to cross-linking and cleavage. Experimental results are consistent with
that expected from theory.
Received: 15 April 1996 / Revised: 3 July 1996 / Accepted: 9 July 1996 相似文献
Abstract— 1-Aryl-2-methyl-4,5-dihydropyrrol-3-carboxylic acid ethyl ester (a cyclic enamine) was observed to dehydrogenate to give 1-aryl-2-methyl-pyrrol-3-carboxylic acid ethyl ester upon irradiation in the presence of oxygen and in the presence or absence of meso -tetraphenylporphine (TPP). N -Aryl cyclic amines were shown to be singlet oxygen sensitizers. 相似文献
The thermal reaction of HNCO has been studied in a static cell at temperatures between 873 and 1220 K and a constant pressure of 800 torr under highly diluted conditions. The reaction was measurable above 1000 K by FTIR spectrometry. The products detected include CO, CO2, HCN, NH3, and the unreacted HNCO. In this moderate temperature regime, the rates of product formation and HNCO decay cannot be accounted for by a previously established high-temperature mechanism, assuming HNCO → NH + CO (1) as the initiation process. Instead, a new bimolecular reaction, 2HNCO → CO2 + HNCNH (2), has been invoked to interpret the disappearance of HNCO as well as the formation of various products, most importantly CO2. The concentration profiles of all measured species can be quantitatively modeled, throughout the temperature range analyzed, by varying k2 using a modified mechanism. The kinetically modeled values of k2 can be effectively represented by This result agrees closely with that computed with the conventional transition-state theory using the TST parameters predicted by the BAC-MP4 method: The bimolecular reaction takes place via a stable 4-membered ring intermediate which is isoelectronic with diketene; viz. 相似文献
A unique matrix system consisting mostly of 4-nitrophenol has shown to be very effective for matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analysis of large DNA oligomers when a cooled sample stage was used to prevent the sublimation of this matrix under vacuum. Using this 4-nitrophenol matrix with UV laser desorption, detection of picomole quantities of DNA oligomers containing up to approximately 800 nucleotides was routinely achieved. The effectiveness of this matrix was further demonstrated by the observation of a double-stranded DNA oligomer larger than 1000 base pairs, seen as a denatured single-stranded species, with a molecular ion mass exceeding 300 000 Da. The potential applications of 4-nitrophenol as a matrix for DNA sizing are discussed. 相似文献
Nitration of 2-bromo or 2-chlorotropone gave a new compound, 2,7-dinitrotropone: The halegen atom on the 2-position was displaced by the nitro group through an electrophilic substitution reaction. Nitration of 3,5,7-tribromotropolone gave 3,7-dibromo-5-nitropolone: the nitro group again displaced the bromine atom at position 5. 相似文献
The electron impact mass spectra of eleven N-arylglycines and seven substituted aniline-N,N-diacetic acids were obtained under 70 eV and 14 eV ionization energies. The fragmentation patterns are similar to those of α-amino acids except for the degree of cleavage. The dehydration process of the diacetic acids may be considered as the characterestic process for this group of compounds. 相似文献