pyrimidine

Purine

Colorless powder or crystal, easily soluble in water, insoluble in organic solvents, and optically active

The maximum absorption value is around 260 nm

right-handed double helix

Antiparallel double strands: the deoxyribose monophosphate backbone is on the outside, the bases are on the inside, and the base pair plane is perpendicular to the longitudinal axis

Surface functional area: the minor groove is shallow and the major groove is deep, which is the basis for protein recognition and DNA binding.

Base complementary pairing, AT pairing, CG pairing

Stabilizing force: Hydrogen bonding double strands stabilize transversely, base stacking force stabilizes double strands longitudinally

Positive supercoiling is the same as DNA helix, tight coiling effect

Negative supercoiling is the opposite of DNA helix, unwinding effect

The finished products of RNA and its components nucleotides, nucleosides, purine bases, and pyrimidine bases are all in the form of white powder or crystals, while DNA is a loose asbestos-like fibrous solid. Except for inosinic acid and guanylic acid, which have an umami taste, most nucleic acids and nucleotides have a sour taste.

Both are slightly soluble in water, insoluble in ethanol, ether, chloroform and other organic solvents, and their sodium salts are easily soluble in water.

DNA is more sticky than RNA.

Definition: Under the action of certain physical and chemical factors, the double strands of DNA unwind and form two single strands.

Denaturation factors: excessive acid and alkali heating

Nature of denaturation: breakage of hydrogen bonds between double strands

The main changes in the physical and chemical properties after denaturation: increase in UV absorption, decrease in viscosity, increase in sedimentation coefficient, and loss of biological activity.

Dissolution temperature tm value: The temperature at which 50% of the DNA melts is also called the melting temperature

Definition: Under appropriate conditions, the two complementary strands of denatured DNA can restore their native double helix conformation. This phenomenon is called denaturation.

The thermally denatured DNA can be renatured after slow cooling. This process is called annealing.

Primary structural characteristics

secondary structure

tertiary structure

Correction tRNA

primary structure

secondary structure

Primary structural characteristics

high level structure