When the total pressure is considered, as in chemical analysis and in thermodynamics it is often referred to as psia or absolute pressure of the substance or of the fluid which would then include the atmospheric pressure. It is important to include the subscript g or a to define which pressure is being noted. Psi can also be the difference between two pressures, be they gage or absolute. Psi is also used in materials engineering referring to the unit stress caused when a load is imposed on a structure or on a part.
Adenine is one of the two purine nucleobases (the other being guanine) used in forming nucleotides of the nucleic acids. In DNA, adenine binds to thymine via two hydrogen bonds to assist in stabilizing the nucleic acid structures. In RNA, which is used for protein synthesis, adenine binds to uracil.
They hold the two strands of DNA together. The nitrogenous bases in DNA are A (adenine), C (cytosine), G (guanidine), and T (thymine). In each of these bases, the nitrogen of the secondary amine bonds to the deoxyribose in the backbone. DNA consists of two strands running in opposite directions. The hydrophobic nitrogenous bases are on the inside, hidden from water. Hydrogen bonds between the nitrogenous base hold the two strands of DNA together. These hydrogen bonds are base specific. That is, A (adenine) can form hydrogen bonds only with T (thymine). C (cytosine) can form hydrogen bonds only with G (guanine). The thymine-adenine pair interacts through two hydrogen bonds.