scholarly journals A chromatographic approach to the determination of relative free energies of interaction between hydrophobic and amphiphilic amino acid side chains

1992 ◽  
Vol 1 (6) ◽  
pp. 786-795 ◽  
Author(s):  
Thomas C. Pochapsky ◽  
Quinton Gopen
Keyword(s):  
Amino Acid ◽  
Side Chains ◽  
Free Energies ◽  
Amino Acid Side Chains ◽  
Amphiphilic Amino Acid

Peptide Backbone Effect on Hydration Free Energies of Amino Acid Side Chains

2014 ◽  
Vol 118 (46) ◽  
pp. 13162-13168 ◽  
Author(s):  
Timir Hajari ◽  
Nico F. A. van der Vegt
Keyword(s):  
Amino Acid ◽  
Side Chains ◽  
Free Energies ◽  
Peptide Backbone ◽  
Amino Acid Side Chains

scholarly journals Interactions between amino acid side chains in cylindrical hydrophobic nanopores with applications to peptide stability

2008 ◽  
Vol 105 (46) ◽  
pp. 17636-17641 ◽  
Author(s):  
S. Vaitheeswaran ◽  
D. Thirumalai
Keyword(s):  
Amino Acid ◽  
Protein Stability ◽  
Salt Bridge ◽  
Bulk Water ◽  
Side Chains ◽  
Free Energies ◽  
Cylindrical Pore ◽  
Amino Acid Side Chains ◽  
Exit Tunnel ◽  
Dynamics Simulations

Confinement effects on protein stability are relevant in a number of biological applications ranging from encapsulation in the cylindrical cavity of a chaperonin, translocation through pores, and structure formation in the exit tunnel of the ribosome. Consequently, free energies of interaction between amino acid side chains in restricted spaces can provide insights into factors that control protein stability in nanopores. Using all-atom molecular dynamics simulations, we show that 3 pair interactions between side chains—hydrophobic (Ala–Phe), polar (Ser–Asn) and charged (Lys–Glu)—are substantially altered in hydrophobic, water-filled nanopores, relative to bulk water. When the pore holds water at bulk density, the hydrophobic pair is strongly destabilized and is driven to large separations corresponding to the width and the length of the cylindrical pore. As the water density is reduced, the preference of Ala and Phe to be at the boundary decreases, and the contact pair is preferred. A model that accounts for the volume accessible to Phe and Ala in the solvent-depleted region near the pore boundary explains the simulation results. In the pore, the hydrogen-bonded interactions between Ser and Asn have an enhanced dependence on their relative orientations, as compared with bulk water. When the side chains of Lys and Glu are restrained to be side by side, parallel to each other, then salt bridge formation is promoted in the nanopore. Based on these results, we argue and demonstrate that for a generic amphiphilic sequence, cylindrical confinement is likely to enhance thermodynamic stability relative to the bulk.

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