sentences:  In 2012, a group of American scientists led by Floyd E. Romesberg, a chemical biologist at the Scripps Research Institute in San Diego, California, published that his team designed an unnatural base pair (UBP).The two new artificial nucleotides or "Unnatural Base Pair" (UBP) were named d5SICS and dNaM.More technically, these artificial nucleotides bearing hydrophobic nucleobases, feature two fused aromatic rings that form a (d5SICS–dNaM) complex or base pair in DNA.