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Nucleic acid hydration is crucially important for their conformation and utility [1093], as noted by Watson and Crick [828]. The strength of these aqueous interactions is far greater than those for proteins due to their highly ionic character [542b]. The DNA double helix can take up a number of conformations (for example, right handed A-DNA pitch 28.2 Å 11 bp, B-DNA pitch 34 Å 10 bp, C-DNA pitch 31Å 9.33 bp, D-DNA pitch 24.2 Å 8 bp and the left handed Z-DNA pitch 43Å 12 bp) with differing hydration. The predominant natural DNA, B-DNA, has a wide and deep major groove and a narrow and deep minor groove and requires the greatest hydration.
The importance of water is actually secondary. The key to life, i.e. a selfreplicating molecule, is the hydrogen bond, which is what holds the strands of DNA together and determines how a single strand can precisely replicate its complement. It happens that the hydrogen bond is also responsible for all the remarkable and anomalous properties of water, and if you want to create daughter molecules from the mitosis of a DNA strand, that can only happen in an environment that does not distort hydrogen bonds - i.e. water.
An interesting water affect is water flowing through carbon nanotubes. The water will move intermittently, like stop and go traffic, with flow rates higher than predicted by standard models. One explanation is connected to the binary nature of hydrogen bonding. The carbon nano-tubes have all the carbon atoms with four covalent bonds. The result is water cannot from the covalent state of the hydrogen bonding with the carbon, since the carbon can't share electrons that way. Rather water can only form the polar state of hydrogen bonding by interacting with the carbon via van der Waals forces. This one-sidedness causes the water to become potentiated; higher average enthalpy, since both bonding states would like to happen with the covalent state slightly more stable. The pure polar state of the hydrogen bonding also defines higher entropy than found in normal water. The intermittent nature of the movement seems to show that the water is attempting to lower potential through covalent hydrogen bonding, causing the water to self gel for an instant; stops due to viscosity. But since the energy difference between this and the pure polar state is small and carbon is not cooperating, the water changes state back to polar, full of energy and entropy; traffic goes again. This affect is useful for water moving through membranes.
Quote from: puppypower on 09/11/2015 11:59:43An interesting water affect is water flowing through carbon nanotubes. The water will move intermittently, like stop and go traffic, with flow rates higher than predicted by standard models. One explanation is connected to the binary nature of hydrogen bonding. The carbon nano-tubes have all the carbon atoms with four covalent bonds. The result is water cannot from the covalent state of the hydrogen bonding with the carbon, since the carbon can't share electrons that way. Rather water can only form the polar state of hydrogen bonding by interacting with the carbon via van der Waals forces. This one-sidedness causes the water to become potentiated; higher average enthalpy, since both bonding states would like to happen with the covalent state slightly more stable. The pure polar state of the hydrogen bonding also defines higher entropy than found in normal water. The intermittent nature of the movement seems to show that the water is attempting to lower potential through covalent hydrogen bonding, causing the water to self gel for an instant; stops due to viscosity. But since the energy difference between this and the pure polar state is small and carbon is not cooperating, the water changes state back to polar, full of energy and entropy; traffic goes again. This affect is useful for water moving through membranes.I am unfamiliar with these studies, can you provide a link?I am surprised that water in a carbon nanotube would have increased entropy. Typically water at interfaces is more ordered (as counterintuitive as it is, the separation of oil and water is actually driven by entropic terms, by reducing the surface area of the oil and water, more of the water is free to relax into the bulk state, rather than the highly ordered, almost ice-like, state that it adopts at the interface.) I would have expected water in a CNT to display the same behavior, thereby decreasing entropy.Also, hydrogen bonding is not a covalent interaction. It is almost purely electrostatic (one can see this because the orientation is determined by the dipole moments of the H-bonded molecules, not by orbital symmetry)
Hydrogen bonds tend to form with a geometry in which the hydrogen bond donor, the hydrogen and the hydrogen-bond acceptor are arranged in a straight line. In electrostatic terms this arrangement is clearly less favorable than an arrangement in which the two dipoles are “folded over” on top of one another to bring both positive charge centers directly into contact with the two negative charge centers. This is clearly not what is happening in the case of hydrogen bonds, so there has to be another component to hydrogen bonding beyond pure electrostatics.Quantum mechanical calculations show that the free electron pairs found on nitrogen and oxygen are delocalized around the hydrogen nucleus similar to the way electrons are shared by bonded atoms in a normal covalent bond. This “covalent” component of the interaction is strongly orientation dependent, i.e. in order to get this covalent interaction the orbital with the free electron pairs of the hydrogen bond acceptor have to be aligned quite well just like the geometry of covalent bonding is rather restrictive.
the folding is very stable and always results in exact folding, with no statistical variation. It is weakly held together and should show variation but it does not.
Quote from: puppypowerthe folding is very stable and always results in exact folding, with no statistical variation. It is weakly held together and should show variation but it does not. There are several diseases caused by misfolding of proteins, for example "Mad Cow Disease" is caused by misfolding of PrP, and hints that other important neurological diseases like Alzheimer's could be caused by misfolding and polymerization of several other proteins like amyloid and tau. Water cannot protect these proteins, and it cannot refold the protein correctly once it is misfolded.One must conclude that the genetic sequence of the protein and its sequence of construction are just as important in folding proteins as the temperature, salinity and polar characteristics of the water in which they are formed. Water itself does not create life.See: https://en.wikipedia.org/wiki/Prion