Determination of materials present in skeletonized human remains and the associated DNA: Development of a GC/MS protocol.

DNA testing of skeletonized human remains is considered to be challenging, especially when the remains have been exposed to inhibitory materials during decomposition. Inhibitors affect the processing of DNA, either by preventing efficient extraction or interfering with down-stream PCR-based processes. Limited studies have been performed on real-world samples that have been exposed to such inhibitors. This paper presents the development of a gas chromatography/mass spectrometry (GC/MS) protocol for the evaluation of materials present in skeletonized human remains recovered from the field, as well as the DNA extracted from the same materials. Twenty-one bone samples and seventeen DNA extracts were evaluated across three solvents and multiple GC/MS parameters to determine the optimal conditions for the recovery of trace materials present. The aim of this work is to provide a technique that can determine the presence of inhibitors prior to DNA extraction, allowing analysts to optimize removal of inhibitory materials.

Casting of 3-dimensional footwear prints in snow with foam blocks.

Commercially available foam blocks are presented as an alternative material for the casting and preservation of 3-dimensional footwear impressions located in snow. The method generates highly detailed foam casts of questioned footwear impressions. These casts can be compared to the known outsole standards made from the suspects' footwear. Modification of the commercially available foam casting blocks is simple and fast. The foam block is removed and a piece of cardboard is secured to one side of the block with painter's masking tape. The prepared foam block is then placed back into its original box, marked appropriately, closed and stored until needed. When required the foam block is carefully removed from its storage box and gently placed, foam side down, over the questioned footwear impression. Next, the crime scene technician's hands are placed on top of the cardboard and pressure is gently applied by firmly pressing down onto the impression. The foam cast is removed, dried and placed back into its original container and sealed. The resulting 3D impressions can be directly compared to the outsole of known suspected item(s) of footwear.

Novel method for the detection of nitroglycerin in smokeless powders.

Nitroglycerin is an active component in many explosive substances. Notably, it is found as an active ingredient in double-base smokeless powders, differentiating them from single-base powders, whose main active ingredient is nitrocellulose. It is proposed that the detection of nitroglycerin within various types of ammunition will allow for the differentiation between single and double-base smokeless powders, thus allowing for a method of distinguishing ammunition or bulk powder samples that may be found during the course of a criminal investigation. Presumptive tests are an effective tool in field-testing for forensic science. These tests are used primarily as rapid, sensitive means of elucidating the chemical characteristics of an unknown sample in-situ. In this paper, the authors present a novel method for the detection of nitroglycerin in smokeless powders with the use of a presumptive color test reagent, dimethylaminocinnamaldehyde (p-dmac). Twenty-five smokeless powders were tested using this reagent to evaluate the color change that would occur in the presence of nitroglycerin. All presumptive results were confirmed via gas chromatography-mass spectrometry.

Surface modification for the collection and identification of fingerprints and colorimetric detection of urea nitrate.

Glass surfaces were modified with a combination of dyes and reagents to allow for the potential simultaneous recording of a detailed fingerprint and the detection of the explosive urea nitrate (UN), as a proof of principle of surface modification for simultaneous linking of identity to manipulation of explosives. By coating microscope slides with 9,10-diphenylanthracene (DPA), p-dimethylaminobenzaldehyde (p-DMAB) and p-dimethylaminocinnamaldehyde (p-DMAC), a colorimetric change was observed in the presence of UN, while revealing a fingerprint with enough resolution to isolate at least 10 minutiae. This is the first step in creating point-of-care devices capable of detecting low concentrations of explosives and drug metabolites and connecting them to a fingerprint.

Amplified electrocatalysis at DNA-modified nanowires.

Arrayed gold nanowires are a novel and useful platform for electrochemical DNA detection. Pilot studies testing the use of these templated structures with an electrocatalytic reporter system revealed that very low detection thresholds for target DNA sequences can be obtained. One factor contributing to the heightened sensitivity is the high signal-to-noise ratio achieved with the large electrocatalytic signals observed at DNA-modified nanowires. Here, we explain the improved sensitivity with evidence illustrating that electrocatalysis at DNA-modified nanostructures generates amplified signals that are significantly larger than those observed at bulk gold surfaces. The results presented strongly suggest that the three-dimensional architectures of the nanowires facilitate the electrocatalytic reaction because of enhanced diffusion occurring around these structures. Effects unique to the nanoscale are shown to underlie the utility of nanowires for DNA biosensing.

Synthesis, characterization, and cellular uptake of DNA-binding rose bengal peptidoconjugates.

Peptide conjugates of the xanthene dye rose bengal (RB) are described featuring sequences that promote DNA binding. The complexation of these conjugates with DNA causes efficient quenching of the fluorophore singlet state and suppresses singlet oxygen production. When incubated with human cells, the RB conjugates pass through the cell membrane but are not visualized in the nucleus. This behavior is in stark contrast to that exhibited by structurally analogous conjugates containing the unhalogenated xanthene dye fluorescein. These results highlight the marked sensitivity of cell permeability characteristics to subtle structural differences.