A femtosecond study of the interaction of human serum albumin with a surfactant (SDS)

The interaction of a protein, human serum albumin (HSA) with a surfactant (sodium dodecyl sulfate, SDS) was studied by femosecond up-conversion. HSA was labeled covalently with a probe (CPM, 7-dimethylamino-3-(4-maleimidophenyl)-4-methyl-coumarin). Binding of SDS to HSA is found to accelerate the solvation dynamics similar to 1.3-fold. The solvation dynamics in HSA displays two time components: 30 ps (20 %) and 800 ps (80 %). When similar to 10 SDS molecules bind to HSA the components are 15 ps (40 %) and 800 ps (60%). It is argued that SDS may increase the solvent exposure of the probe (CPM); it may also displace the buried water molecules in the immediate vicinity of CPM.