In this paper, attention is focused on analysis of the fragmentation of α-hydroxy-β-amino phosphonate esters designed as inhibitors of protein kinase A. An interesting proton migration mechanism in the cleavage of the P-C bond is investigated by electrospray ionization tandem mass spectrometry. A possible rearrangement mechanism is proposed and verified by high-resolution mass spectra using isotope deuterium/hydrogen-exchange technology and additionally checked by detailed DFT calculation based on Gaussian software. The result clearly indicates that this mechanism proceeds by a five-membered ring concerted transition state with activation energy 11.3 kcal mol(-1) for the compound 3f. The overall reaction is endothermic with an energy 13.2 kcal mol(-1). The effect of different substituents and different metal ions for rearrangement of these esters is studied by experiment and theory. It is concluded that this rearrangement process is energetically unfavorable and hence only occurs in the mass spectrometer. 相似文献
Based on perfect rotational isomeric state model of polyethylene chainwithout any torsional stretch or chain twisting, the separation distance between a zig-zagsegment and its re-entry ones in lamella has been investigated. The intervals were definedby a pair of quantum numbers (kx, ky) according to the formula: D=0.153/(31/2)((8kx2+16ly2)1/2)(nm)kx and ky are integers just as the lattice coordinates on the respective & and α- axes ofthe crystal lattices for polyethylene. The crystal lattices of polyethylene can be accessible by the re-entry stems,whether it is adjacent fold or not.Conformations,until 14-bond fold,of the fold part were investigated.The sequence TTGTTG'G'TTGGTTG possesses the lowest average conformation energy per bond for (110) fold,and TGTTG'G'TTTG' for (020) fold.TTTGGTGGTTGTG'etc.for(200) fold. 相似文献
Triazophos is mainly used in Asian and African countries for the control of insects in agricultural production. Camelid variable domains of heavy-chain antibodies (VHHs) show great promise in monitoring environmental chemicals such as pesticides. To improve the rate of success in the generation of VHHs against triazophos, genes specifically encoding VHH fragments from the unique allotype IgG3a of an immunized Camelus bactrianus were amplified by using a pair of novel primers and introduced to construct a diverse VHH library. Five out of seven isolated positive clones, including the VHH T1 with the highest affinity to triazophos, were derived from the allotype IgG3a. A one-step enzyme-linked immunosorbent assay (ELISA) using VHH T1 genetically fused with alkaline phosphatase (AP) had a half-maximum inhibition concentration of 6.6 ng/mL for triazophos. This assay showed negligible cross-reactivity with a list of important organophosphate pesticides (< 0.1%). The average recoveries of triazophos from water, soil, and apple samples determined by the one-step ELISA ranged from 83 to 108%, having a good correlation with those by a gas chromatography mass spectrometry (R2 = 0.99). The VHH-AP fusion protein shows potential for the analysis of triazophos in various matrices.
