Abstract
Thermal unfolding of ribonuclease, lysozyme, chymotrypsinogen, and β-lactoglobulin was studied in the absence or presence of poly(ethylene glycols). The unfolding curves were fitted to a two-state model by a nonlinear least-squares program to obtain values of ΔH, ΔS, and the melting temperature Tm. A decrease in thermal transition temperature was observed in the presence of poly(ethylene glycol) for all of the protein systems studied. The magnitude of such a decrease depends on the particular protein and the molecular size of poly(ethylene glycol) employed. A linear relation can be established between the magnitude of the decrease in transition temperature and the average hydrophobicity of these proteins; namely, the largest observable decrease is associated with the protein of the highest hydrophobicity. Further analysis of the thermal unfolding data reveals that poly(ethylene glycols) significantly effect the relation between ΔH° of unfolding and temperature for all the proteins studied. For β-lactoglobulin, a plot of ΔH versus Tm indicates a change in slope from a negative to a positive value, thus implying a change in ΔCp in thermal unfolding caused by the presence of poly(ethylene glycols). Results from solvent-protein interaction studies indicate that at high temperature poly(ethylene glycol) 1000 preferentially interacts with the denatured state of protein but is excluded from the native state at low temperature. These observations are consistent with the fact that poly(ethylene glycols) are hydrophobic in nature and will interact favorably with the hydrophobic side chains exposed upon unfolding; thus, it leads to a lowering of thermal transition temperature.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 7813-7819 |
| Number of pages | 7 |
| Journal | Biochemistry |
| Volume | 26 |
| Issue number | 24 |
| State | Published - 1987 |
| Externally published | Yes |
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- Biochemistry
Cite this
Thermal stability of proteins in the presence of poly(ethylene glycols). / Lee, Lucy L Y; Lee, James.
In: Biochemistry, Vol. 26, No. 24, 1987, p. 7813-7819.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Thermal stability of proteins in the presence of poly(ethylene glycols)
AU - Lee, Lucy L Y
AU - Lee, James
PY - 1987
Y1 - 1987
N2 - Thermal unfolding of ribonuclease, lysozyme, chymotrypsinogen, and β-lactoglobulin was studied in the absence or presence of poly(ethylene glycols). The unfolding curves were fitted to a two-state model by a nonlinear least-squares program to obtain values of ΔH, ΔS, and the melting temperature Tm. A decrease in thermal transition temperature was observed in the presence of poly(ethylene glycol) for all of the protein systems studied. The magnitude of such a decrease depends on the particular protein and the molecular size of poly(ethylene glycol) employed. A linear relation can be established between the magnitude of the decrease in transition temperature and the average hydrophobicity of these proteins; namely, the largest observable decrease is associated with the protein of the highest hydrophobicity. Further analysis of the thermal unfolding data reveals that poly(ethylene glycols) significantly effect the relation between ΔH° of unfolding and temperature for all the proteins studied. For β-lactoglobulin, a plot of ΔH versus Tm indicates a change in slope from a negative to a positive value, thus implying a change in ΔCp in thermal unfolding caused by the presence of poly(ethylene glycols). Results from solvent-protein interaction studies indicate that at high temperature poly(ethylene glycol) 1000 preferentially interacts with the denatured state of protein but is excluded from the native state at low temperature. These observations are consistent with the fact that poly(ethylene glycols) are hydrophobic in nature and will interact favorably with the hydrophobic side chains exposed upon unfolding; thus, it leads to a lowering of thermal transition temperature.
AB - Thermal unfolding of ribonuclease, lysozyme, chymotrypsinogen, and β-lactoglobulin was studied in the absence or presence of poly(ethylene glycols). The unfolding curves were fitted to a two-state model by a nonlinear least-squares program to obtain values of ΔH, ΔS, and the melting temperature Tm. A decrease in thermal transition temperature was observed in the presence of poly(ethylene glycol) for all of the protein systems studied. The magnitude of such a decrease depends on the particular protein and the molecular size of poly(ethylene glycol) employed. A linear relation can be established between the magnitude of the decrease in transition temperature and the average hydrophobicity of these proteins; namely, the largest observable decrease is associated with the protein of the highest hydrophobicity. Further analysis of the thermal unfolding data reveals that poly(ethylene glycols) significantly effect the relation between ΔH° of unfolding and temperature for all the proteins studied. For β-lactoglobulin, a plot of ΔH versus Tm indicates a change in slope from a negative to a positive value, thus implying a change in ΔCp in thermal unfolding caused by the presence of poly(ethylene glycols). Results from solvent-protein interaction studies indicate that at high temperature poly(ethylene glycol) 1000 preferentially interacts with the denatured state of protein but is excluded from the native state at low temperature. These observations are consistent with the fact that poly(ethylene glycols) are hydrophobic in nature and will interact favorably with the hydrophobic side chains exposed upon unfolding; thus, it leads to a lowering of thermal transition temperature.
UR - http://www.scopus.com/inward/record.url?scp=0023505188&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0023505188&partnerID=8YFLogxK
M3 - Article
C2 - 3427106
AN - SCOPUS:0023505188
VL - 26
SP - 7813
EP - 7819
JO - Biochemistry
JF - Biochemistry
SN - 0006-2960
IS - 24
ER -