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Dew drop on a hydrophobic leaf surface Cutting a water droplet using a superhydrophobic knife on superhydrophobic surfaces Water drops on the hydrophobic surface of grass. In chemistry, hydrophobicity is the chemical property of a molecule (called a hydrophobe) that is seemingly repelled from a mass of water. [1] In contrast, hydrophiles are ...
[1] [2] The word hydrophobic literally means "water-fearing", and it describes the segregation of water and nonpolar substances, which maximizes the entropy of water and minimizes the area of contact between water and nonpolar molecules. In terms of thermodynamics, the hydrophobic effect is the free energy change of water surrounding a solute. [3]
Hydrophobins are characterised by the presence of 8 conserved cysteine residues that form 4 disulphide bonds. [15] They are able to reverse the wettability of surfaces by spontaneous self-assembly of the monomeric proteins into amphipathic monolayers at hydrophobic:hydrophilic surfaces.
A hydrophobic barley field increased crop yield from 1.7 to 3.4 t/ha, and a field of lupins increased the yield by 1 t/ha within 2 years of claying. [3] Liming is a method to reduce soil water repellency in acidic soils. [3] The liming process consists of adding calcium carbonate, which increases the pH of the soil towards neutral.
Cloth, treated to be hydrophobic, shows a high contact angle. The theoretical description of contact angle arises from the consideration of a thermodynamic equilibrium between the three phases: the liquid phase (L), the solid phase (S), and the gas or vapor phase (G) (which could be a mixture of ambient atmosphere and an equilibrium concentration of the liquid vapor).
The higher the contact angle the higher the hydrophobicity of a surface. Surfaces with a contact angle < 90° are referred to as hydrophilic and those with an angle >90° as hydrophobic. Some plants show contact angles up to 160° and are called ultrahydrophobic, meaning that only 2–3% of the surface of a droplet (of typical size) is in contact.
Hydrophobic collapse is a proposed process for the production of the 3-D conformation adopted by polypeptides and other molecules in polar solvents. The theory states that the nascent polypeptide forms initial secondary structure ( ɑ-helices and β-strands ) creating localized regions of predominantly hydrophobic residues .
Within the cork domain is the TonB binding region (residues 7 to 11). The large membrane spanning monomeric β-barrel domains have 22 β-strands of variable length, several of which extend significantly beyond the membrane hydrophobic core into the extracellular space. There are 11 extracellular loops numbered L1 to L11.