Solid evidence for the defence: How ArcticZymes’ heat-labile dsDNase has revolutionised the handling of precious DNA samples in forensic labs
Contamination – a forensic challenge
Isolating a perpetrator’s DNA from a victim of sexual assault involves complex and labour-intensive steps, which could potentially result in a poor DNA sample.
To reduce processing steps, ArcticZymes’ newly developed enzyme provides an effective solution for DNA isolation without the need for harsh, contamination-prone preparation steps. In this way it can improve forensic analysis and preserve much stronger evidence for the courtroom.
In order to obtain relatively pure sperm DNA from a vaginal swab, one needs to selectively remove the victim’s DNA from the sample. This is achieved by first chemically lysing the victim’s cells (the sperm is not damaged by this step). The sample is then spun down and washed repeatedly to remove the victim’s DNA from the sperm.
However, this washing step is not only time-consuming, but can also result in significant loss of sperm, leading to a suboptimal or even failed forensic analysis.
A collaborating scientist working in a forensic lab set out to develop a protocol that would eradicate the need for the washing step. To achieve this, the researcher proposed that ArcticZymes’ unique dsDNase could be used to remove any contaminating victim’s DNA without the need for washing. The only problem was that the available dsDNase at that time required inactivation for 20 minutes at 65˚C, a temperature that risks damaging the sperm sample.
A revolutionary approach to enzyme design
To find an ideal solution, the researcher asked if ArcticZymes could create a dsDNase that could be inactivated at a lower temperature, and for a shorter time.
With the challenge set, and in close collaboration with NorStruct at the University of Tromsø, Norway, ArcticZymes’ scientists began to experiment with the structure of the enzymes. What they discovered was that by changing one or more of 11 specific amino acids, they could modify the enzyme’s heat-labile characteristic, while maintaining its enzymatic activity.
ArcticZymes’ scientists manipulated these specific amino acids through several targeted mutations. All mutated genes were cloned and transformed into Pichia pastoris (a type of yeast) to produce enzymes for functional studies.
Functional testing unveiled an optimal enzyme product, named HL-dsDNase (Heat-Labile dsDNase), that can be inactivated by a five-minute incubation at 58°C, thereby achieving the initial goal to create a uniquely custom product with drastically-reduced inactivation temperature and time.
Once engineered, HL-dsDNase was sent to the forensic scientist where it achieved excellent results. By design, it eradicated the need for the washing step, thereby minimising damage to samples and significantly decreasing the time needed to process DNA samples. Furthermore, by simplifying the procedure, there was less chance of introducing contaminating DNA into the mix.
For extra reassurance, HL-dsDNase was found to be useful for the purification of reagents such as Taq polymerase, primers and dNTPs, which are easily prone to contaminated through handling. Therefore it is very important to eliminate contaminating DNA from all sources to prevent incrimination of the wrong person.
HL-dsDNase was born out of a unique combination of ArcticZymes’ distinct, high-quality enzymes and its customer-oriented expertise in genetic engineering.
By working directly with researchers in the field, ArcticZymes’ scientists are able to tailor-design cutting-edge products that can simplify and improve the workflows of any scientific lab or product development of prospective commercial partners.