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To cope with volume constraints, DNA can pack itself in the appropriate solution conditions with the help of ions and other molecules. Usually, DNA condensation is defined as "the collapse of extended DNA chains into compact, orderly particles containing only one or a few molecules". [ 3 ]
The highest DNA adsorption efficiencies occur in the presence of buffer solution with a pH at or below the pKa of the surface silanol groups. The mechanism behind DNA adsorption onto silica is not fully understood; one possible explanation involves reduction of the silica surface's negative charge due to the high ionic strength of the buffer.
The buoyant density of most DNA is 1.7g/cm 3. [11] DNA does not usually exist as a single strand, but instead as a pair of strands that are held tightly together. [9] [12] These two long strands coil around each other, in the shape of a double helix.
For biological systems with water as a solvent, hydrophobic effect contributes and helps in formation of a helix. [8] Stacking is the main stabilizing factor in the DNA double helix. [9] Contribution of stacking to the free energy of the molecule can be experimentally estimated by observing the bent-stacked equilibrium in nicked DNA.
The topology of the DNA is described by the equation below in which the linking number is equivalent to the sum of Tw, which is the number of twists or turns of the double helix, and Wr, which is the number of coils or "writhes." If there is a closed DNA molecule, the sum of Tw and Wr, or the linking number
At the start of his experiment he named the primary culture "phase one". Phase two is defined as the period when cells are proliferating; Hayflick called this the time of "luxuriant growth". After months of doubling the cells eventually reach phase three, a phenomenon he named " senescence ", where cell replication rate slows before halting ...
The Meselson–Stahl experiment is an experiment by Matthew Meselson and Franklin Stahl in 1958 which supported Watson and Crick's hypothesis that DNA replication was semiconservative. In semiconservative replication, when the double-stranded DNA helix is replicated, each of the two new double-stranded DNA helices consisted of one strand from ...
Plasmid miniprep. 0.8% agarose gel ethidium bromide-stained.. A plasmid preparation is a method of DNA extraction and purification for plasmid DNA.It is an important step in many molecular biology experiments and is essential for the successful use of plasmids in research and biotechnology.