Hydrophilic and hydrophobic residues

Both hydrophilic and hydrophobic residues cover the entrance channel with hydrophobic residues dominating the lower part near the vanadate-binding site. Interestingly, amino acid residues from both monomers contribute to the substrate... 

A. beta-pleated sheets with alternating hydrophilic and hydrophobic residues. 

The AFP has hydrophilic and hydrophobic residues arranged as patches on the faces of silica. In contrast, PVP has hydrophilic residue groups randomly exposed to the silica surface. These residues do not have a regular arrangement, and we speculate that the PVP molecules can easily interact with each other as well as aggregate on the Si02 surface, forming a loose film (Fig. 5). 

Unintended precipitation can be difficult to predict as the effect depends on a combination of the distribution of hydrophilic and hydrophobic residues on the protein surface, the pH, ionic strength, protein concentration, temperature, and composition of the aqueous phase. A perfectly clear solution may gradually become turbid during application to a chromatographic colunm that results in column blocking. 

Fig. 39. (A) A schematic representation of the three-dimensional structure of the PLC-(51 PH domain. The a-helices and -sheets are indicated by cylinders and arrows, respectively. Ala residues are indicated by open circles. IP3 is shown by a CPK model. (B) The amphipathic a2-helix viewed from the C-terminus. Hydrophilic and hydrophobic residues are shown by gray and black circles, respectively. (C) A model of the conformational change of the PLC-51 PH domain-induced at the membrane surface.

According to the accumulated knowledge, a membrane is a necessary component of the protocell, as it is of the modern cell. Membrane organization follows the phase separation stage. The presence of hydrophilic and hydrophobic residues, as well as electrically polar groups within the polymers, appear to be sufficient conditions for self-assembly of membraneous structures. 

Figure 6.3 Self-assembled nanostructures based on P-sheet (a) peptides packing into sheets and fibers based on hydrophobic interactions on one face of the molecule, and complementary ionic interaction on the other (b) peptides with alternating hydrophilic and hydrophobic residues assemble into P-sheet structures (left) that form twisted ribbons (right) and bundle into larger fibers and (c) self-assembly based on amphiphilic triblock peptides, where the central hydrophobic block forces self-assembly via hydrophobic interactions between molecules and hydrogen bonding along the fiber axis.

KLD-12 peptide shows how the P-sheet structure is formed on the special arrangement of the amino acid residues of the peptide. The backbone of the peptide showed that hydrophilic residues such as lysines-K and aspartic acids (D) are on the bottom of the model while the hydrophobic residues such as leucines-L are on the top. The alternative appearance of hydrophilic and hydrophobic residues in the backbone of the peptide promotes the formation of p-sheet structure, which in turn promotes the self-assembly through intermolecular interactions. (Figure adapted from Ref [43] (Copyright 2002) National Academy Sciences.)... 

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