Essay On Tertiary Swabs

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Recommended: The Action of Salivary Amylase practial report

I. Introduction

The problem While DNA profiles can be obtained from evidentiary swabs, forensic science is currently deficient in the methods to determine the tissue source of the DNA. While proper confirmatory tests exist for biological fluids such as semen1,2 and blood3, similar tests for the confirmatory identification of saliva are lacking. Being able to confidently identify the source material of the DNA may help criminal investigators corroborate the claims of an alleged victim or suspect. For example, analysis of an evidentiary swab from an alleged suspects finger. The alleged victim states that she was sexual assaulted and the suspect used his finger to penetrate her. The alleged suspect states that no sexual assault occurred and …show more content…

This method is flawed for various reasons. The first is that tests rely on α-amylase activity (such Phadebas®), which can be a problem on degraded or weathered samples as well as samples that are contaminated with factors that may inhibit activity. Another problem is that immunoassays (such as RSID™-Saliva) are inherently presumptive because one can never be certain that an antibody is not cross-reacting with a non-target molecule. An additional problem lies within the fact that various other body fluids contain α-amylase, although typically in levels much lower than those seen in saliva. For example, typically saliva will contain 263000 to 376000 IU/L of α-amylase, where urine will contain 263 to 940 IU/L, blood will contain 110 IU/L, and semen will contain 35 IU/L.4 However, false positives have been …show more content…

I will also be collecting 10 samples of other bodily fluids (peripheral blood, semen, vaginal secretions, menstrual blood, and urine) from different individuals using Diva Cups®, SoftCups™, sterile collection cups, while obtaining peripheral blood samples from a certified phlebotomist. I will be enriching whole saliva for small peptides using a combination of a TFA acid crash and 30 kDa molecular weight cut-off filters. I will then digest the peptides for analysis. I will be testing this prep method using LCMS. Once a sufficient prep method is devised, I will analyze 50 saliva samples using ultra-performance liquid chromatography–quadrupole–time-of-flight mass spectrometry (UPLC QTOF) in order to make a structural confirmation of the protein sequence via tandem MS/MS. I will be using reversed phase chromatography with a gradient of acetonitrile (ACN) and water as my solvents. I will be repeating the method on 10 samples of other bodily to ensure that the biomarkers chosen as markers for confirmatory identification of saliva are not present in any other

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