In this study ,a wild type Salmonella typhimurium (S .typhimurium) strain was isolated and identified in Hong Kong (S129) ,then the asdA gene was knocked out and replaced with kanamycin resistant gene in a Salmonella typhi-murium strain S129 using the λ RED-mediated recombination method .The constructed mutant asdAΔS129 was validated by culturing in the presence or absence of 2 ,6-diaminopimelic acid (DAP) growth in vitro and evaluating its virulence in BALB/c mice challenge assay .Therefore ,this study has demonstrated that an asdA mutant Salmonella typhimurium has been success-fully constructed .

Objective To detect the molecular characteristics of the serum samples of rats suffered from sudden unexpected death of acute myocardial ischemia (experimental group) and death caused by air embolism (control group) applied by ATR-FTIR, and to discuss the forensic signiifcance of identiifcation of causes of death by sudden unexpected death of acute myocardial ischemia by two-dimension infrared spectroscopy. Methods Adult male SD rats were randomly divided into SCD group and DCAE group. The serum samples were analyzed by ATR-FTIR. The similarity coefifcient of spectra between two groups was analyzed by OMNIC software. The spectra with higher signal-noise ratio were obtained and used to build two-dimension spectra model by Matlab 2010a software. Results The peak shapes, positions and intensities of the spectra were extremely similar between two groups, and the similarity coefifcient reached 99.78%. Meanwhile, the similarity coefifcient of second derivative spectra decreased to 98.62% between two groups. Moreover, on the two-dimension spectra model, the component differences were present at about 1 625cm-1, 1 550cm-1, 1 080cm-1 and 860cm-1, and the number of auto-peaks was different, which suggested that the evident differences were related to the molecular contents of protein, glycogen, nuclear acid, and so on. Conclusion It is hard to differentiate the molecular differences of serum samples of rats between SCD and DACE based on one-dimension spectra. However, two-dimension infrared spectra could intuitively and effectively relfect the molecular differences, and it would apply to determining the cause of death in forensic science.

Objective To explore the value of lipidic degradation in puparium cases of C.megacephala during weathering in postmortem interval estimation. Methods The puparium cases of reared C.megacephala were collected, and laid outdoor. They were taken back 5 days and 10 days later, and then be stored at -20℃. The samples of control group were cleaned and cryopreserved immediately. The spectra were collected and preprocessed. The peak position and peak height were read and performed statistical analysis by SPSS 19.0 software. Results Compared to control group, the positions of Vas CH3 band showed no shift, and the Vas CH2 band showed blue shift, meanwhile, the Vs CH2 band disappeared in both experimental groups, moreover, the Vs CH3 band showed red shift only in 10d group;except of the Vs CH3 band in 5d group, the intensities of both the other two lipidic bands reduced in both experimental groups. Compared with 5day group, the Vs CH3 band showed red shift in 10d group, meanwhile, the differences of all the lipidic bands had statistical signiifcance. Conclusion Detection of lipidic degradation in puparium cases of C. megacephala during weathering by micro-FTIR provides a novel way to estimate postmortem interval and performs its potential for forensic applications.

Objective To observe the protein degredation of empty puparium cases ofC. megacephala after weathering and to explore its practical significance on postmortem interval estimation in forensic science. MethodsThe standardized feeding was used inC. megacephala, and the empty puparium cases were collected and put into the forest. They were taken back 5 days, and 10 days later, respectively. The spectra were collected and preprocessed, and then the absorption peaks of amides were read, and curve fitting was performed in the average spectra of each group. The statistical analysis was performed by SPSS 19.0.Results Compared to control group, ifve days post weathering, the position of amideⅠabsorption peak showed blue shift, but the amideⅡabsorption peak showed no shift, moreover, none of the amide absorption peaks showed changes inpeak intensity. For the secondary structures, α-helix decreased and β-sheet increased slightly, however, β-turn did not change; Ten days post weathering, the positions of both amideⅠandⅡabsorption peaks showed blue shift, and an obviousshoulder peak appeared in amide I absorption peak. Meanwhile, both of amideⅠandⅡabsorption peaks showed decreased in peak intensity. Moreover, for the secondary structures, α-helix and β-sheet showed the same tendency as in the 5th day group, except for the β-turn increased dramaticlly.Conclusion The spectra of the empty puparium cases of C. megacephala showed that the absorption peaks of amideⅠandⅡpresented certain characteristic features within ten days post weathering, and estimate relative long-time postmortem interval.