Deoxyribonucleic acid, single stranded from human placenta

Human placental DNA is isolated from donor placenta, but will contain some maternal DNA. The DNA fragments are sonicated to produce fragments of consistent size.

Sonicated Deoxyribonucleic acid, single stranded from human placenta, was used as blocking agent in Southern hybridization of DNA from human papillomavirus (HPV) positive SiHa, HeLa and CaSki cell-lines. It was used as standard in GC/MS analysis of exocyclic DNA adducts.

Many factors contribute to the signal-to-noise ratio in nucleic acid hybridizations. These factors include the presence of solvent (formamide), hybridization temperature, length of hybridization, volume of hybridization solution, degree and method of agitation, use of blocking reagents, concentration and specific activity of the probe, use of molecular agents to increase the rate of nucleic acid reassociation, and the degree of stringency used during the washing of the membrane.

In order to decrease any non-specific hybridization of the probe to a substrate, blocking agents must be used. Generally, a combination of blocking reagent, detergent, and denatured, fragmented DNA is used to accomplish this. Sigma offers sonicated, denatured DNA from a variety of species for use as a blocking agent in Northern and Southern blotting and other nucleic acid hybridization techniques.

• High quality human DNA.
• DNA fragments of defined sizes.

DNA is supplied in a solution of 100mM phosphate buffer.  This is a ready to use concentrated solution
of 9-12 mg/ml DNA in 100mM phosphate buffer. However, it will reanneal on standing at room temperature so it is recommended to boil the solution for 10 minutes and then cool on ice for at least 5 minutes prior to use. Cooling on ice will
reduce the chances for reannealing, as it is more likely to reanneal if cooled at room temperature.