ABSTRACT
Based on melamine-Cu conjugate and subsequent interruption of formation of polythymine (Poly T)-templated copper nanoclusters (CuNCs), a novel fluorescent strategy was developed for detection of melamine.The method relied on the principle that the coordination of melamine to copper would be unfavorable for the reduction of Cu2+ in the poly T-CuNCs synthesis process, and thereby resulting in the decrease of fluorescence intensity of CuNCs.By this method, the fluorescence response of CuNCs displayed an linear relationship with melamine concentration in the range from 5 μmol/L to 120 μmol/L.The detection limit was 1.5 μmol/L.Furthermore, the assay was successfully applied in the detection of melamine in milk samples with good recoveries.
ABSTRACT
Objective To analyze the polymorphism of histidine rich protein 2(HRP II)gene in Plasmodium falciparum (Pfhrp2)from falciparum malaria patients in Yunnan Province,so as to lay the foundation for studying the defection of antigen genes of Plasmodium. Methods The filter paper blood samples and related information of falciparum malaria cases reported were obtained in Yunnan Province from August 2012 to September 2015. Under the guidance of the specific primers,the exon2 regions in Pfhrp2 gene in P. falciparum from DNA samples were amplified by PCR,and the PCR products were sequenced. The sequences of exon2 region in Pfhrp2 gene were blasted by comparing with the reference sequences AY816237,AY816240,and AY816301. Next,the polymorphism of the sequence in exon2 region of Pfhrp2 gene was analyzed by MEGA 5.04 software. The conserved sites and genetic distances between sequences were calculated by using the software as well,and the clustering tree was drawn according to the genetic distances between the amino acid sequences. Results A total of 218 bloods samples from the falciparum malaria cases in 15 prefectures of Yunnan Province were collected,and the sources of infection included Yun?nan,Africa and Myanmar. The PCR results showed that the exon2 regions in Pfhrp2 genes of 155 samples were positive by am?plification and their products were sequenced successfully. The sequence analysis showed that the length range of the amino acid residues of exon2 region in Pfhrp2 gene was from 115 aa to 298 aa,the average length was 239.7 aa. There was no statistically significance among the means of the amino acid residues of the isolates from Africa( 239.9 aa),Myanmar(239.5 aa)and Yun?nan(241.6 aa)(F=0.025,P>0.05). All the 155 amino acid sequences ended with type 12 repeat,98.1%(152/155)of them started with type 1 repeat and 1.9%(3/155)of them started with type 2. Type 2 presented most frequently repeat in all the se?quences and the average repeat times were 12.9. The homologous locus of the DNA sequences in exon2 regions of the 155 Pfhrp2 genes was 894 bp,among which the conservative sites accounted for 20.6%(186/894),and the variable sites for 78.2%(699/894). The genetic distances between the sequences of Africa isolates ranged from 0 to 0.741,and those of the Myanmar and Yun?nan isolates were 0-0.948 and 0-0.750,respectively. The cluster analysis showed that all the 155 sequences clustered into 3 cat?egories on genetic distances between amino acid sequences according to the size of the amino acid sequence length. At the same level,the sequences had approximate lengths and amino acid repeat types. Conclusion The sequence of exon2 region in Pfhrp2 gene of P. falciparum from falciparum malaria cases in Yunnan Province is highly polymorphic,the P. falciparum iso?lates are clustered mainly according to the size of the amino acid sequence of exon2 region in Pfhrp2 gene.
ABSTRACT
A direct current glow discharge mass spectrometry ( GD-MS) for the determination of Li, Be, Na, Mg, Si, P, K, Ca, Ti, V, Cr, Mn, Co, Ga, Sr, Mo, Ag, Cd, Sn, Sb, W and Pb in nickel-zinc ferrites was developed. Copper powder as the conductive medium was evenly mixed with nickel-zinc ferrites powder for tableting, and then the impurity elements in nickel-zinc ferrites were determined by GD-MS. The influence of sample preparation and the glow discharge conditions including discharge current, discharge voltage, discharge gas flow rate and pre-sputter time on discharge stability and analysis sensitivity were investigated. The mass spectrometry interferences of analytes were investigated, as well as appropriate isotopes were selected. Most of the mass spectrometry interferences were avoided by measuring in medium resolution mode and high resolution mode. Total signal of Fe, Ni, Zn, O and Cu normalization was adopted, and the impurity elements in nickel-zinc ferrites were calculate in subtraction. The results showed that the detection limits for the investigated elements were in the range of 0. 001-0. 29 μg/g, the relative standard deviations of each element were within 3 . 5%-18 . 6%. The analysis results were consistent with those obtained by inductively coupled plasma mass spectrometry.