Screening and Identification of Nucleic Acid Aptamers Specifically Binding to Human Lipocalin 6 / 中国生物化学与分子生物学报

It is an urgent and difficult task to establish a simple and efficient method for identifying and isolating sperm cells from mixed stains in forensic science. Nucleic acid aptamers targeting sperm cell-surface proteins can be used for the separation and purification of sperms from mixed stain samples. Human lipocalin 6 (hLCN6) is an epididymal secreted protein that binds to the head and tail of sperm cells and is associated with sperm maturation. Using the systematic evolution of ligands by the exponential enrichment (SELEX) technique, magnetic bead-bound hLCN6 was used as the target molecule to screen for aptamers with high affinity and specificity to hLCN6 from a random single-stranded DNA (ssDNA) library. Through 15 rounds of positive selection and 3 rounds of negative selection, 24 clones were selected and subjected to sequence analysis. Subsequently, 4 candidate aptamers were selected and further examined for their binding affinity and specificity by enzyme-linked oligonucleotide adsorption (ELONA) and cell binding assays. One aptamer (H2) against hLCN6 with a high affinity and specificity was isolated and investigated by dot blotting and immunofluorescence staining. The result revealed that the candidate aptamer H2 with a dissociation constant of (3. 21 ± 0. 75) nmol/ L was able to recognize and specifically bind to hLCN6. The aptamer H2 also showed high affinity and specificity to human sperms in vitro, which establishes the foundation for the separation of sperm cells from mixed stain based on nucleic acid-protein interactions and provides a new scheme.

Research Progress on Accumulated Degree Days for PMI Estimation / 法医学杂志

Among many factors that affect postmortem interval （PMI）, temperature is undoubtedly the most important factor, but simply considering temperature in estimation of PMI has limitations. Accumulated degree days （ADD） is an important indicator related to biological growth and development, which considers two major variables, environmental temperature and elapsed time. Therefore, the establishment of mathematical model of ADD and some evaluation indicators to estimate PMI, is obviously better than single temperature variable. This article briefly describes the research history of ADD, its application in PMI estimation, and the problems it faces, to provide reference for the further development of ADD to improve the accuracy of PMI estimation.

Sequential Changes of Total Adenine Nucleotide and Adenylic-Acid Energy Charge in Muscles of Rats after Death / 法医学杂志

Objective To determine the purine adenylate [adenosine triphosphate （ATP）, adenosine diphosphate （ADP）, adenosine monophosphate （AMP）] content in the muscles of both hind limbs of rats at different postmortem interval （PMI）, calculate the changes in the total adenine nucleotide （TAN） content and the adenylic-acid energy charge （AEC）, and explore their relationship with PMI. Methods Healthy rats were sacrificed by cervical dislocation and kept at 20 ℃. The muscles of their hind limbs were extracted at 0, 24, 48, 72, 96, 120, 144, and 168 h after death. Reversed-phase high performance liquid chromatography was used to determine the content of purine adenylates, the TAN and AEC of the muscles of the both hind limbs were calculated, and the related regression equations of their relationship with PMI were established. Results Within 168 h of death of rats, the trend of ATP change was different from ADP, and the content of AMP continuously increased. The TAN value gradually increased with the extension of PMI, and the AEC showed a downward trend within 168 h after death. Among them, the patterns of AEC changes with PMI were obvious, the correlation coefficient was high （ R2=0.903）, and the curve fitting relationship was good; the fitting relationship between ATP, ADP, AMP, TAN and PMI was poor （ R2=0.198-0.754）. Conclusion The postmortem change patterns of AEC provide new research ideas for PMI estimation in the forensic field.

Analysis of chemical constituents of fatty acids and their esters of Coicis Semen by UPLC-Triple-TOF-MS / 中草药

Objective: To establish a rapid qualitative analysis method for fatty acids and esters in Coicis Semen by ultra-performance liquid chromatography triple quadrupole time-of-flight mass spectrometry (UPLC-Triple-TOF-MS). Methods: Agilent ZORBAX-SB C18 (250 mm × 4.6 mm, 5.0 μm) column was used. The mobile phase was acetonitrile-isopropanol (1:1) elution, the flow rate was 1 mL/min, the detection wavelength was 210 nm, the column temperature was 30 ℃, and the injection quantity was 10 μL. Electrospray ion source positive ion mode was adopted, and the scanning range was m/z 100-1 500. The sample data were collected by full scanning mode, and the fatty acid chemical composition of Coicis Semen was quickly identified according to the information obtained by high-resolution mass spectrometry combined with secondary mass spectrometry. Results: A total of 29 kinds of fatty acids and esters in Coicis Semen were detected, and the cracking rules of the compounds were analyzed. Through the mass-to-charge ratio of molecular ion peaks and fragment ions, the Scifinder and Reaxy network databases, and the literature, these compounds were different under the action of ion source by losing the structure of oleic acid, linoleic acid, palmitic acid, oxidizing oleic acid and the like. The mass-to-charge ratio of the fragment ions, and the name and structural formula of the 29 fatty acids and their ester compounds were inferred. Conclusion: The method of qualitative analysis of the fatty acids and esters of Coicis Semen established in this study is accurate, rapid and sensitive, which provides experimental basis for improving the quality control level of Coicis Semen and further elucidating the pharmacodynamic substance basis of Coicis Semen.