Protein design - Salt Bridges

Salt bridges in proteins are bonds between oppositely charged residues that are sufficiently close to each other to experience electrostatic attraction. They contribute to protein structure and to the specificity of interaction of proteins with other biomolecules, but in doing so they need not necessarily increase a protein’s free energy of unfolding. The net electrostatic free energy of a salt bridge can be partitioned into three components: charge-charge interactions, interactions of charges with permanent dipoles, and desolvation of charges. Energetically favorable Coulombic charge-charge interaction is opposed by often unfavorable desolvation of interacting charges. As a consequence, salt bridges may destabilize the structure of the folded protein. There are two ways to estimate the free energy contribution of salt bridges by experiment: the pK(a) approach and the mutation approach. In the pK(a) approach, the contribution of charges to the free energy of unfolding of a protein is obtained from the change of pK(a) of ionizable groups caused by altered electrostatic interactions upon folding of the protein. The pK(a) approach provides the relative free energy gained or lost when ionizable groups are being charged. In the mutation approach, the coupling free energy between interacting charges is obtained from a double mutant cycle. The coupling free energy is an indirect and approximate measure of the free energy of charge-charge interaction. Keywords —------------------------ In addition to hydrogen bonding, what other interactions could contribute to the stabilization of this Alpha helix? Specify the interactions and use lines to connect residues involved in these interactions. PENQWKQELDTRYRNAL #alphaHelix #aminoAcid #polypeptide #oligopeptide #hydrogenBond #helix #proline #saltBridges #ionicBridges #NikolaysGeneticsLessons #protein #peptide #disulfideBridges #covalentBounding #ionicBounding #hydrophobicInteraction #proteinStructure #proteinSequence #proteinFolding #ImidazolRing #Histidine #polypeptideChain #hydrolysesSynthesis #condensationReaction #condensationSynthesis #peptides #globularProteins #fibrousProteins #Genetics