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Molecular formaldehyde. A colorless gas with a characteristic pungent, irritating odor. It is stable at about 150 °C, but it polymerizes when condensed to a liquid. 1,3,5-Trioxane, with the formula (CH 2 O) 3. It is a white solid that dissolves without degradation in organic solvents. It is a trimer of molecular formaldehyde.
Formaldehyde or glutaraldehyde fixes tissue or cells by irreversibly connecting a primary amine group in a protein molecule with a nearby nitrogen in a protein or DNA molecule through a -CH 2 - linkage called a Schiff base. The end result also creates the simulation, via color changes, of the appearance of blood flowing under the skin.
Methanediol, also known as formaldehyde monohydrate or methylene glycol, is an organic compound with chemical formula CH 2 (OH) 2. It is the simplest geminal diol . In aqueous solutions it coexists with oligomers (short polymers).
The degree of unwinding varies depending on the intercalator; for example, ethidium cation (the ionic form of ethidium bromide found in aqueous solution) unwinds DNA by about 26°, whereas proflavine unwinds it by about 17°. This unwinding causes the base pairs to separate, or "rise", creating an opening of about 0.34 nm (3.4 Å).
This is a ball and stick model of a water molecule. It has a permanent dipole pointing to the bottom left hand side. In a true covalent bond, the electrons are shared evenly between the two atoms of the bond; there is little or no charge separation. Covalent bonds are generally formed between two nonmetals.
Formaldehyde can react with macromolecules in two steps: first it reacts with a nucleophilic group on a DNA base for example, and forms a methylol adduct, which is then converted to a Schiff base. [15] In the second step, the Schiff base, which can decompose rapidly, forms a methylene bridge with another functional group on another molecule. [15]
DNA nanotechnology is the field that seeks to design nanoscale structures using the molecular recognition properties of DNA molecules. [178] DNA nanotechnology uses the unique molecular recognition properties of DNA and other nucleic acids to create self-assembling branched DNA complexes with useful properties. [179]
At least three DNA conformations are believed to be found in nature, A-DNA, B-DNA, and Z-DNA. The B form described by James Watson and Francis Crick is believed to predominate in cells. [27] It is 23.7 Å wide and extends 34 Å per 10 bp of sequence. The double helix makes one complete turn about its axis every 10.4–10.5 base pairs in solution.