Nucleic acids are large molecules which carry genetic information between cells. The most common types are deoxyribonucleic acid and ribonucleic acid which play an important role in cell division and other biological processes. Natural nucleic acids are protonated at the normal pH in the body, which makes them more stable. Very high or low pH will denature the nucleic strands, which inhibits processes such as transcription and is lethal to cells. Artificial nucleic acids include peptide nucleic acid and threose nucleic acid, which are used extensively in research and medicine.