The Inverse and Direct Hofmeister Series of Hen Egg White Lysozyme at Ph Below the Isoelectric Point (Pi) as Seen by Small Angle X-Ray Scattering(SAXS)
The structural changes of Hen Egg White Lysozyme (HEWL) in the intermediate stages leading up to Hofmeister anion-induced aggregation were measured using small-angle x-ray Scattering (SAXS). We used three concentrations of HEWL: 10mg/ml, 60mg/ml and 200mg/ml and two concentrations of salts: 0.1M and 1.0M, mostly in a Tris-buffer solution with a pH of 9.0. For 200mg/ml in Di-water solution, the scattering signal was best fit using an ellipsoidal form factor with equatorial radius of 28.4±0.1 Å and polar radius of 11.3±0.1 Å, and a screened Coulomb repulsive structure factor with an effective radius of 19.9±0.1 Å and protein surface charge of 6.9±0.2 times the charge of an electron (e). At 10mg/ml and 60mg/ml, the interaction between HEWL was negligible and data were fitted using spherical and ellipsoidal form factor respectively. We observe a partial pattern of increase in the radius of HEWL at 10mg/ml with both 0.1M and 1.0M Hofmeister sodium salts (SO42-, F-, Cl-, Br-, NO3-, I-, SCN-) as we add salts from left to right in the series. The variation of the polar radius of HEWL at 60mg/ml with 0.1M of various Hofmeister sodium salts shows an elongation of the protein as we go from left to right in the Hofmeister series. The results for 10mg/ml and 60mg/ml show that each salt type has different effect on the solution-state structure of HEWL, notably a symmetric to an asymmetric shape transition, which partially follows the Hofmeister series.
Koirala, Pawan, "The Inverse and Direct Hofmeister Series of Hen Egg White Lysozyme at Ph Below the Isoelectric Point (Pi) as Seen by Small Angle X-Ray Scattering(SAXS)" (2018). ETD Collection for University of Texas, El Paso. AAI10822142.