Hydrophobic Interactions Flashcards
thermodynamics of dissolving non-polar solutes in polar solvents
dG > 0
dH < 0, exothermic
dS < 0, dramatic decrease
entropy in forming solvent cages
polar solvents form solvent cages around nonpolar molecules, makes stable H-bonds between solvent molecules, giving -ve dH and overall decrease in entropy as disorder decreases
hydrophobic
+ve dG for transfer from nonpolar to polar solvent
hydrophilic
-ve dG for transfer from nonpolar to polar solvent
why do nonpolar molecules clump together in a polar solvet
system always moves to increase entropy, fewer solvent molecules needed to form one big cage than many small cages, gives more disordered system as more free solvent molecules therefore higher entropy
clathrate
lattice of one molecule trapping and containing another
methane clathrate hydrates
potential energy source, risk of release of methane into atmosphere as global warming progresses
native conformation of proteins
consequence of the sequence of amino acid residues forming the primary structure and the pattern of interactions among residues and their environment
hydrophobic collapse of proteins
nonpolar amino acids exposed to water, water organises around nonpolar amino acids in cages therefore decreasing S and destabilising system, gives collapse of nonpolar regions giving a nonpolar protein core, this frees water molecules and increases S, also has knock-on effect of enhancing dispersion interaction therefore increasing the enthalpic stabilisation
Ramachandran plot
stability of a peptide as a function of 2 angles, visualises energetically allowed regions for backbone dihedral AA residues in a protein structure
why common combinations of angles in Ramachandran plot
corresponds to formation of a-helix and b-sheets which are both stabilised by H-bonds
