New stable folding of beta-lactoglobulin induced by 2-propanol.
beta-lactoglobulin A has been studied in 2-propanol-water mixtures by means of circular dichroism, fluorescence and small angle X-ray scattering. At a low ionic strength, 2-propanol induces an increase in alpha-helix structure followed by a further transformation which gives rise to a new feature, rich of beta-sheet fragments. The second step of the secondary structure transformation is time-dependent and depressed at high ionic strength. As a consequence, the tertiary structure is completely modified and a new stable protein folding may be hypothesized. Small angle X-ray scattering measurements reveal that 2-propanol induces a diffuse protein aggregation, but the complex equilibria among intra- and inter-molecular hydrophobic and electrostatic interactions may be modulated by balancing the ionic strength and/or alcohol percentage.
Barteri
M
M
Dipartimento di Chimica, Universitá degli Studi di Roma La Sapienza, Italy. barteri@axcasp.caspur.it
Gaudiano
M C
MC
Mei
G
G
Rosato
N
N
D019840:2-Propanol / Q000737:chemistry*; D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D005453:Fluorescence; D007782:Lactoglobulins / Q000737:chemistry*; D017510:Protein Folding; D014961:X-Ray Diffraction
D007782:Lactoglobulins; D019840:2-Propanol