On the structural stability and solvent denaturation of proteins. II. Denaturation by the ureas.
نویسندگان
چکیده
The effects of the water-miscible straight chain and branched alcohols and glycols on the native conformation of sperm whale myoglobin, cytochrome c, and oc-chymotrypsinogen have been investigated by spectral, difference spectral, and optical rotatory dispersion methods. Based on the midpoints of the denaturation transitions, that is, the amount of alcohol or glycol required to produce 50% denaturation at 25”, it is concluded that the effectiveness of the alcohols as protein denaturants increases with increasing chain length or hydrocarbon content, in conformance of what is expected of the disorganization of the hydrophobic interior of these proteins revealed by their detailed three-dimensional x-ray structure. As a rule, branching of the hydrocarbon portion of the alcohols tends to reduce their effectiveness as protein denaturants. The glycols are found to be less effective than the corresponding alcohols, suggesting that increased polarity or hydrogen-bonding capacity is of secondary importance when compared with the effects of increasing hydrocarbon content. The theories of Peller and Flory, used to account for the effects of denaturants and salts on the temperature transition of proteins and polypeptides, were extended to the analysis of isothermal denaturation data, with appropriate binding and Setschenow parameters based on free energy of transfer data taken from the literature or calculated from N-acetyl-L-tryptophan ethyl ester solubilities. The denaturation midpoints, S,, based on the assumption of a hydrophobic mechanism of alcohol-protein side chain interactions, are found to be in satisfactory agreement with the experimentally obtained Sm values. Both the increased hydrophobicity with increasing chain length and the somewhat reduced effectiveness of the alcohols on branching are in most cases correctly predicted. For the straight chain alcohols, fairly satisfactory agreement with the experimental data is also obtained with binding constants based on estimates of free energies of hydrophobic bond formation, obtained by Scheraga and associates using the Nemethy and Scheraga theory of hydrophobic bonding.
منابع مشابه
Thermal stability of P-lactoglobulin Bin the presence of ‘ucrnse, sorbitol and trehalose as osmolJtes
Thermal denaturation of p-Iactoglobulin type B in the absence and pteNcno: of g arious concentrations oftrehalo5e, sucrose and sork toles sugar osmolytes and twlyols were nuyoured hy monitoring changes in theabsorption coefficients at pH 2.0. These measurements gave aliss, or I. mpdpDint of denaturation), Al-fis(enthalpy change at Ty). and ACp (consttun-pressure heal capaciit eh.iltgtii under a...
متن کاملThermal stability of a-Lactalbumin in the presence of various sugars as osmolytes
Thermal denaturation of a-Lactalbumin in the absence and presence of various concentrations of sucrose,sorbitol, glucose and galactose as sugar osmolytes were measured by monitoring changes in the absorptions thatcarried out in a Lambd 35 UV-Vis double beam spectrophotometer at pH 6.0. These measurements gave valuesof T., (midpoint of denaturation), AH., (enthalpy change at T.), and ACp (consta...
متن کاملMolecular dynamics studies on the denaturation of polyalanine in the presence of guanidinium chloride at low concentration
Molecular dynamic simulation is a powerful method that monitors all variations in the atomic level in explicit solvent. By this method we can calculate many chemical and biochemical properties of large scale biological systems. In this work all-atom molecular dynamics simulation of polyalanine (PA) was investigated in the presence of 0.224, 0.448, 0.673, 0.897 and 1.122 M of guanidinium chlorid...
متن کاملComparative analysis of chemical and thermal denatured 13-lactoglobu1in A in the presence of sugar osmolytes
Chemical denaturation and thermal denaturation of13-lactoglobulin A (f3 — lgA) in the absenceand presence of various concentrations sugar osmolytes and polyols were measured bymonitoring changes in the absorption coefficients at pH 2.0. It has been observed that AGD°(H20), (Gibbs free energy change in absence of denaturant at 25 °C) of f3-1gA in the presenceof 10% (w/v) Trehalose, Sucrose, Sorb...
متن کاملEffects of surface charge on denaturation of bovine carbonic anhydrase.
This work compares the denaturation of two proteins-bovine carbonic anhydrase II (BCA) and its derivative with all lysine groups acetylated (BCA-Ac(18))-by urea, guanidinium chloride (GuHCl), heat, and sodium dodecyl sulfate (SDS). It demonstrates that increasing the net negative charge of the protein by acetylation of lysines reduces its stability to urea, GuHCl, and heat, but increases its ki...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- The Journal of biological chemistry
دوره 245 10 شماره
صفحات -
تاریخ انتشار 1970