A protein has a sedimentation coefficient of 2.6S, when ultracentrifuged in a 0.1 M NaCl solution; the same protein has a sedimentation coefficient of 4.6S, when centrifuged in a 1.0 M NaCl solution. This change in the sedimentation rate at 1.0 M NaCl, most likely occurs because the protein ____________.
elevated
The change in the sedimentation rate of the protein from 2.6S in 0.1 M NaCl to 4.6S in 1.0 M NaCl indicates that the protein undergoes a conformational change in the high salt concentration solution. The increase in salt concentration causes the screening of electrostatic repulsions between charged groups on the protein, leading to a decrease in the overall size of the protein and a more compact conformation. This change in conformation leads to an increase in the sedimentation coefficient, indicating a higher rate of sedimentation. Therefore, the most likely explanation for the change in sedimentation rate is that the protein undergoes a structural change from an expanded form to a more compact form in response to the increase in salt concentration.
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