A study of folch-P1 apoprotein. II. Relation between polymerization state and conformation

The Molecular Size and Shape of the Folch‐Pi Apoprotein in Aqueous and Organic Solvents

“…1 for the protein in 1% acetic acid and in dioxan/l% acetic acid (2/3, v/v). In 1 % acetic acid, extrapolation to zero concentration gives equal to 3.9 S in agreement with a first evaluation of 5,, of 3.7 S* 10% [3]. Increasing the concentration of acetic acid up to 6% does not lead to significant changes either in the slope, or for &o,w (4.1 S), in contrast with the results on aldolase and ,!3-lactoglobulin [19 -211.…”

“…In such conditions, the choice of solvent was rather limited. The solvation properties of 1% acetic acid for the Folch-Pi apoprotein have been demonstrated [3,71; 6% acetic acid and mixed dioxan/water have been described as dissociating agents by affecting either the electrostatic or hydro-phobic interactions [I 3, 19 -221; 2-chloroethanol was chosen as the organic solvent instead of the chloroform/methanol mixture (2 : 1, v/v) used for extraction of the protein because it is a single-component solvent precluding hydrophobic interactions and has been well studied for its helix-promoting properties on proteins 1231.…”

Raman spectroscopic study of the interactions of dimyristoyl- and 1-palmitoyl-2-oleoylphosphatidylcholine liposomes with myelin proteolipid apoprotein

“…The 10 °C depression in the gel-liquid-crystalline phase transition temperature Tm observed in the present work is compared to the Curatolo et al (1978) study in which essentially no depression in Tm was observed. The dramatic difference in the extent to which the apoprotein perturbs the bilayer in the two studies probably arises from an increase in molecular weight (vide infra) which occurs during the transfer of the apoprotein from an organic medium to an aqueous solution (Nicot et al, 1973;Nguyen Le, 1976;Lavialle et al, 1979).…”

“…Although the myelin proteolipid apoprotein may be obtained in soluble form from either organic solvents or aqueous solutions, the structural studies described above were performed by adding the appropriate lipids to the organic solution of the apoprotein. Since significant conformational and molecular weight differences arise for the apoprotein depending upon the solvent system used in its prepa-ration (Sherman & Folch-Pi, 1970;Nicot et al, 1973;Lees et al, 1979; Nguyen Le et al, 1976;Lavialle et al, 1979), we examine the vibrational data for the reconstituted bilayer systems which specifically incorporated the apoprotein prepared in aqueous medium. These spectral data indicate that this form of the apoprotein induces substantially different bilayer effects depending upon the degree of unsaturation within the hydrophobic region of the lipid matrix.…”

Spectroscopic analysis of acylated and deacylated myelin proteolipid protein

“…Intrinsic fluorescence (Cockle et al, 1978), extrinsic fluorescence (Feinstein & Felsenfeld, 1975), and CD spectroscopic studies (Sherman & Folch, 1970;Moscarello et al, 1973) have demonstrated conformational flexibility of the protein as a consequence of the transfer from one medium to another. Thus, while the protein is largely monomeric inorganic solvents with most of its segments in a helical configuration (Moscarello et al, 1973;Nguyen-Le et al, 1976), the water-soluble form occurs as a polydisperse solution (Gagnon et al, 1971;Nguyen-Le et al, 1976) in which most of the hydrophobic side-chain amino acids are buried in the internal folds of the protein.…”