The present study developed an improved analytical method for simultaneous quantification of seven neonicotinoids in food by ultraperformance liquid chromatography combined with electrospray ionization triple quadrupole tandem mass spectrometry (UPLC-MS/MS) under the multiple reaction monitoring (MRM) mode. The optimization of extraction, cleanup, UPLC separation and MS/MS parameters of analytes were especially focused on. The low limits of quantification (LOQs) of neonicotinoids ranged from 0.1 to 6 microg kg(-1). Meanwhile, reasonable recoveries (65-120%) of seven neonicotinoids for food including apple, cabbage, potato, rice, tea, milk, chicken, pork and egg were demonstrated in different spiked levels within their respective linear range (0.025-150 microg kg(-1)). The developed analytical method would be appropriate for the routine, high throughput, high sensitivity quantification of seven neonicotinoids using simple sample pretreatment.
The ground state Raman spectra of all-trans-beta-carotene in n-hexane and CS2 solutions are measured by simultaneously changing the solvent environment and molecular structure under high hydrostatic pressure. The diverse pressure dependencies of several representative Raman bands are explained using a competitive mechanism involving bond length changes and vibronic coupling. It is therefore concluded that (a) the in-phase C=C stretching mode plays an essential role in the conversion of energy from S1 to S0 states in carotenoids, (b) internal conversion and intramolecular vibrational redistribution can be accelerated by high pressure, and (c) the environmental effect, but not the structural distortion or pi-electron delocalization, is responsible for the spectral properties of a given carotenoid species. These findings revealed the potential of high pressure in exploring the nature of the biological functions of carotenoids.
Vegetative growth of Chinese cabbage undergoes the four successive stages which are characterized with the definite types of juvenile, rosette, folding and head leaves. From shoot tips of Chinese cabbage at early folding stage, we constructed a cDNA library and screened the differentially expressed cDNA clones using the cDNAs derived from developing folding leaves and rosette leaves as probes. One complete length of cDNA clone is designated asBcpLH. Computer alignment matched BcpLH to the domains of double-stranded RNA binding (DBRM) and the homologous regions were recognized between BcpLH and human and mouse double-stranded RNA-binding protein TRBP. PCR expression analysis shows that during vegetative growthBcpLH gene was expressed preferentially in folding leaves at folding stage. Transcripts ofBcpLH gene were increased when plants were sprayed with IAA. It is deduced thatBcpLH gene may be related to initiation of folding leaf and leafy head and induced by auxin in the aspect of transcriptional expression.
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