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.