L. Boulkanz et al., FT-IR ANALYSIS FOR STRUCTURAL CHARACTERIZATION OF ALBUMIN ADSORBED ONTHE REVERSED-PHASE SUPPORT RP-C-6, Applied spectroscopy, 49(12), 1995, pp. 1737-1746
The aim of this study is to demonstrate the reliability of the use of
FT-IR spectroscopy to monitor conformational changes when a protein (H
SA) is adsorbed under chromatographic conditions on the silica materia
l RP-C-6. In the aqueous eluent (D2O), the amount of protein retained
on the phase is minimal for 30% CH3CN, whereas no protein is retained
for 40%. Structural results are deduced from quantitative analyses of
the infrared Amide I' absorptions and from measurements of the peptide
NH-ND exchange. Both are performed for HSA in solution and for HSA ad
sorbed on RP-C-6 in suspension in equivalent eluents. For the solution
s, 30% CH3CN in the solvent weakly unfolds some structured loops of th
e protein. Hydration and aggregation are enhanced in 40% CH3CN, which
significantly denatures alpha- and beta-domains. When the protein is a
dsorbed with 0-30% CH3CN in the solvent, about one-tenth of HSA backbo
ne unfolds. In the adsorbed state, the protein is more hydrated and se
lf-associated than in the corresponding solutions. The larger contacts
between HSA and RP-C-6 are observed when the retention amount is the
weakest (30% CH3CN). Results show that retention should have a hydroph
obic origin. The irreversibility of the retention is supposed to be de
pendent on the protein structural and solvation changes observed from
the solutions to the adsorbed states. To explain the elution with orga
nic solvent > similar to 38%, a competition between acetonitrile and t
he solid phase in solvating hydrophobic domains of the protein is sugg
ested.