Showing papers on "Salt bridge (protein and supramolecular) published in 1994"

Contributions of a hydrogen bond/salt bridge network to the stability of secondary and tertiary structure in lambda repressor.

Abstract: In the N-terminal domain of lambda repressor, the Asp 14 side chain forms an intrahelical, hydrogen bond/salt bridge with the Arg 17 side chain and a tertiary hydrogen bond with the Ser 77 side chain. By measuring the stabilities to urea denaturation of the wild-type N-terminal domain and variants containing single, double, and triple alanine substitutions at positions 14, 17, and 77, the side-chain interaction energies, the coupling energy between interactions, and the intrinsic effects of each wild-type side chain on protein stability have been estimated. These studies indicate that the Asp 14-Arg 17 and Asp 14-Ser 77 interactions are stabilizing by roughly 0.8 and 1.5 kcal/mol, respectively, but that Asp 14, by itself, is destabilizing by roughly 0.9 kcal/mol. We also show that a peptide model of alpha-helix 1, which contains Asp 14 and Arg 17, forms a reasonably stable, monomeric helix in solution and responds to alanine mutations at positions 14 and 17 in the fashion expected from the intact protein studies. These studies suggest that it is possible to view the stability effects of mutations in intact proteins in a hierarchical fashion, with the stability of units of secondary structure being distinguishable from the stability of tertiary structure.

Adhesion Force Arising from Solid Salt Bridge Formed after Drying of Liquid Bridge.

Abstract: 工業的に用いられる粒子の多くは粒子間接触部に液架橋が形成され, またその架橋液中には塩類などの溶解性不純物が含まれていることが多い.そのような粒子の雰囲気の湿度が低下すると架橋液中の水は蒸発し, さらにある湿度以下になると塩類が結晶として析出して粒子間に固体架橋が形成される.本研究ではNaCl, KCl, KNO3およびNa2SO4の水溶液によって2つのガラス球間に液架橋を形成させ, それを種々の湿度中においたときの固体架橋の引張り力を測定した.その結果、次のことが明らかとなった. (1) 粒子間の間隙を埋めるように均質に固体架橋が形成される場合, 固体架橋付着力は結晶析出前の液架橋付着力よりも1～2桁大きい, (2) 平均的な固体架橋付着力は結晶体積と粒子半径の積の1/2乗にほぼ比例する, (3) NaClおよびKClの塩は完全に再結晶する湿度以上では微量の水分を含むために, 雰囲気の湿度に応じて付着力が変化する (準固体的に).