There are a few visible
There are a few visible DNA staining methods, which use dyes such as methylene blue, brilliant cresyl blue , crystal violet , Nile blue ,  and ethyl violet . However, although safe, these methods require long staining times, lack sensitivity and are not specific for nucleic acids.
In other scientific fields (e.g., cell metabolism and viability measurements, histochemistry assays and alkaline phosphatase assays), visualization has been accomplished by means of tetrazolium salts, which are organic oxidants that are in themselves colorless or weakly colored. The principle of those methods is the reduction of tetrazolium salts to form a brightly colored formazan product mainly through NADH and NADPH action , , , . Of interest to the nucleic IAA-94 field, bivalent tetrazolium salts with electron withdrawing chemical groups, like Nitro Blue Tetrazolium (NBT), have been shown to bind DNA using their positive tetrazolium rings .
Materials and methods
Discussion The analysis of biomolecules such as proteins and nucleic acids is of great importance in life sciences research as well as for diagnostics in clinical and industrial applications. Current methods limit many such analyses with specialized equipment (e.g., UV-illuminators). This has also limited the expansion of these analyses to much needed and demanded applications such as in situ diagnostics and education.
Acknowledgements This work was supported by the Fondo Nacional de Desarrollo Científico y Tecnológico (Fondecyt), Chile, Project 11130263 (to CW), Project 1090336 (to JB), Project CONICYT + NERC + Programa de Colaboración Internacional PCI-PII20150073 (to CW) and U-inicia from the Vicerrectoría de Investigación Universidad de Chile to CW. We thank Gabriela Contreras for help in an early stage of this work, and Dr. Amalia Sapag, Dr. Victoria Guixé, Felipe Vásquez, Claudia Payacán and all members of the Molecular Biology, Biochemistry and Microbiology laboratories of Universidad de Chile for helpful discussions.
Introduction In most sexual assault cases, standardized evidence kits (rape kits) are used by medical professionals to gather biological material that may have been left on the victim’s body by the assailant. As the probability of recovering DNA on the victim’s body rapidly decreases with time, rape kits are not usually used when the delay between the assault and the medical examination is more than five or seven days [, , ]. In these cases, or when ejaculation did not occur in or on the body, bedding and clothing may represent essential pieces of evidence. Dried semen on fabric is extremely resilient and genetic profiles have been obtained from dried semen stains several decades old . In some cases, items of clothing or bedding have been washed prior to being collected by crime scene personnel, thus decreasing the quantity of DNA available for forensic analysis . However, the power of genetic analysis has greatly improved in the past years, with commercial STR kits becoming increasingly sensitive. As only minute amounts of input DNA are now required, it is possible to obtain a complete genetic profile from semen stains washed up to three times . Washed items are thus valuable exhibits that can potentially reveal the genetic profile of the perpetrator in sexual assault cases.
Materials and methods
Declaration of interest
Introduction Although not fully understood, the molecular toxicology of sulfur mustard (bis(2-chloroethyl)sulfide, SM; CAS–Nr. 505-60-2), an alkylating warfare agent, has been attributed to DNA alkylation , , . The same principle holds true for other alkylating compounds such as nitrogen mustards or monofunctional agents such as the SM analog CEES (2-chloroethyl ethyl sulfide) , , . The resulting DNA adducts can be used for the analytical verification of SM exposure . The procedures required are complex, however, when they are based on sensitive mass spectrometry methods. In general, it is highly unlikely that such techniques are available in conflict zones. Attempts have thus been made to develop convenient detection methods that can be used in the field.