Study On Releasing DNA From Extracted Biological Samples From Lignocellulosic Carrier

With the continuous advancement of modern technology,DNA technology has received more and more attention.As a powerful tool to identify locked suspects.DNA testing technology has been widely used in criminal case testing and played an important role in major difficult cases.Old biological sample testing is a difficult problem to be solved in current DNA testing technology.In actual work,we found that the evidence of old biological samples often showed incomplete detection of the test sites,and even the phenomenon of effective classification could not be obtained.As a result,some major difficult cases have caused the impact of the old biological samples to be affected by the infiltration of biological samples into the lignocellulosic carrier,which is inevitably affected by the light,air and moisture in the external conditions^[1]..Existing biological sample processing and DNA extraction methods are insufficient for the biological samples crosslinked by the biological sample embedded in the compact carrier and the lignocellulosic carrier,and the biological sample cannot be fully released.For DNA samples with long storage times,severe protein denaturation,and severe cross-linking with carriers,DNA extraction is not ideal,and sometimes even effective DNA is not available,thus wasting valuable biological samples and on-site materials,affecting case detection and The acquisition of key evidence.In order to extract and test DNA biosamples from aged samples of lignocellulosic materials containing biological samples.In this study,the aging simulation experiment was carried out on the physical evidence by means of high temperature aging.Since in the forensic science,the lignocellulosic materials are mainly divided into paper and cotton,this study has studied two categories.Since the acid-base conditions required for DNA detection were alkaline,three commercial enzymes having high activity at pH 9 were selected.Enzymatic method,that is,cellulase^[2],Commercial Cellulase A^[3]and Commercial Cellulase B are respectively compounded on paper^[4]lignocellulosic materials and cloth lignocellulosic materials.The required biological sample DNA is eluted from the loose structure of the fiber formed by degradation of the lignocellulosic material,and the biological sample DNA is successfully extracted and detected by STR-PCR technology.After the enzyme activity measurement and protein content determination of the selected three commercial enzymes,the optimal enzyme compounding scheme for degrading paper lignocellulosic materials is the ratio of cellulase to alkaline Commercial Cellulase A protein of18.7:17.9.The protein content of Commercial Cellulase B was 3.21 mg/ml,and the Commercial Cellulase B was dissolved in liquid enzyme,and the supernatant was centrifuged,and then the enzyme having a protein concentration of 1.66 mg/ml was prepared with a pH of 9 Tris-HCI solution.The liquid is the final cellulase for the paper.The optimal enzyme compounding scheme for degradable fabric lignocellulosic materials is that the ratio of cellulase to alkaline Commercial Cellulase A protein is 26.18:10.74,and the content of solid Commercial Cellulase B protein is 3.21 mg/ml.The sugar content was the highest.On the basis of this compounding scheme,when the protein concentration was 1.348mg/ml with the pH 9 Tris-HCI solution,the degradation of cotton material was the best.In order to examine the degradation effect of the lignocellulosic material,the damage of the cellulose of the sample was observed by a scanning electron microscope.The results showed that scanning electron microscopy showed that the hydrolysis of two kinds of compound enzymes caused obvious damage to paper and cloth fibers;it effectively solved the biological sample DNA required for the evidence of lignocellulosic materials containing biological samples.Extracting this key problem;and using the method of compound enzyme degradation for several old cases,the obtained biological sample DNA was subjected to STR-PCR typing test,and the experimental group not treated with enzymatic method could obtain more effects.A good characteristic peak,that is,an enzymatic method,can effectively degrade a lignocellulosic material test sample containing an old biological sample,thereby releasing the desired biological sample DNA for testing.This research not only provides a powerful means for the detection of old-age accumulative cases,but also provides new ideas and methods for the progressive development of forensic science.