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Belopolskaya, T. V.; Tsereteli, G. I.; Grunina, N. A.; Vaveliouk, O. L.

doi:10.1023/a:1010158610943

Cited by 12 publications

(7 citation statements)

References 13 publications

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“…The temperature and intensity of this overshoot increase with increasing annealing time. This result is consistent with previous studies 45 and is known as enthalpy relaxation, which has also been observed in many glass-forming, protein-water and polymeric systems. 32,46,47 However, as the water content of DNA decreases, the intensity of the additional maximum is greatly reduced.…”

Section: Resultssupporting

confidence: 93%

“…The temperature and intensity of this overshoot increase with increasing annealing time. This result is consistent with previous studies and is known as enthalpy relaxation, which has also been observed in many glass-forming, protein−water and polymeric systems. ,, However, as the water content of DNA decreases, the intensity of the additional maximum is greatly reduced. For instance, at the water content of 4.7 wpn, only a small annealing prepeak developed despite annealing the DNA sample at 25 °C for a month (Figure b), indicating that only minor and slow enthalpy relaxation occurs during annealing at 25 °C at such low hydration.…”

Section: Resultssupporting

confidence: 93%

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A Calorimetric and Spectroscopic Study of DNA at Low Hydration

et al. 2004

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Differential scanning calorimetry (DSC) and infrared spectroscopy (IR) were used to study the thermal behavior of DNA as a function of water content up to 12 wpn (water molecules per nucleotide). The DSC and IR results show cooperativity of thermal DNA denaturation at 12 wpn. In the 3.3 to 7.2 wpn range, an early structural change involving slight disruption of base stacking arises, followed at higher temperature by a denaturation process where the major changes in backbone conformation occur. DNA thermal denaturation in the 3.3 to 12 wpn range is irreversible. However, structural disruptions caused by dehydration are fully reversible. The loss of the DNA ordered conformation upon dehydration leads to a decrease in the endothermic maximum that characterizes the thermal denaturation of DNA. At 3.3 wpn, the DNA loses most of its ordered conformation and undergoes a glasslike transition similar to the transition that denatured DNA experiences during reheating. The calorimetric manifestation of the glass transition is established for denatured DNA at low hydration through the study of water plasticizing effects on T g and enthalpy relaxation. At 1.0 wpn (the lowest water content achieved in this study), the DSC and IR data do not show any thermal or structural transitions, indicating the fully amorphous character of DNA at such low hydration.

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Section: Resultssupporting

confidence: 93%

Section: Resultssupporting

confidence: 93%

A Calorimetric and Spectroscopic Study of DNA at Low Hydration

et al. 2004

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“…To recall the criterion, an irreversible transition is not observed in the TMSC measurements, but is observed in the DSC measurements. Therefore, if the C p ′ endothermic peak at 346.2 K in Figure 1A,C,D and in Figure 2 was to be seen as an indication that an irreversible denaturation of lysozyme is occurring, as concluded in the earlier studies, [1][2][3][4][5][6] our TMSC experiments would not show the same broad C p ′ endothermic peak. Instead, one would expect to observe values of C p ′ which would correspond to equilibrium heat capacity of the mixture, that is, C′ p,mixture ) x native C′ p,native + x denat C′ p,denat , where x native is the weight fraction and C′ p,native the equilibrium heat capacity of the native lysozyme, and x denat and C′ p,denat are the corresponding quantities of the denatured lysozyme.…”

Section: Discussionsupporting

confidence: 51%

“…Since the denaturation of proteins is an irreversible process, it follows that the equilibrium thermodynamic equations cannot be used for interpreting the DSC measurements. Despite that, equilibrium thermodynamic approach has been widely used in studying the temperature-induced changes that lead to denaturation of proteins. − It has also been suggested that part of the processes involved such as isomerization and clustering and unclustering in the denaturation process may be reversible . This leads to concern as to whether the denaturation of proteins can be seen as entirely a thermodynamic transition that occurs gradually over a broad temperature range or whether it consists of a series of transformations some of which are reversible, but the consecutive nature of the transformation leads to irreversibility.…”

Section: Introductionmentioning

confidence: 99%

The Endothermic Effects during Denaturation of Lysozyme by Temperature Modulated Calorimetry and an Intermediate Reaction Equilibrium

et al. 2002

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To gain insight into the thermodynamics of protein denaturation, the complex heat capacity, C p * () C p ′ -iC p ′′) of lysozyme-water system has been measured at pH 2.5 in the 293-368 K range by using temperaturemodulated scanning calorimetry (TMSC), a technique in which the thermally reversible enthalpy changes are measured separately and simultaneously with the thermally irreversible enthalpy changes. The plot of C p ′ against the temperature T shows a broad peak, which is similar to that observed in C p,DSC , measured here and elsewhere by differential scanning calorimetry (DSC), a technique which gives the sum of both the reversible and irreversible contributions in the apparent heat capacity value. This peak in C p,DSC has been generally attributed to endothermic heat absorption on reversible and irreversible unfolding processes and irreversible thermal denaturation. It is shown that the observed C p ′ peak results from heat absorption when the equilibrium constant between the native lysozyme state and a conformationally different intermediate state increases with T. The plot of C p ′ versus T is subdivided into four regions, corresponding to the dominance of a certain process. Thermal denaturation of lysozyme was found to occur according to a scheme, native state T unfolded (intermediate) state f denatured state. This conclusion is consistent with the general view that the first step of denaturation of small one-domain globular protein like lysozyme is a reversible conformational (unfolding) transition, and the second step is irreversible denaturation. It is shown that when kept isothermally at T > 341 K, i.e., within the transition temperature range, C p ′ of lysozyme decreases. This decrease is exponential in time and corresponds to a rate constant, which varies according to the Arrhenius-type equation, with a preexponential factor of 5 × 10 20 s -1 and energy of 167 kJ/mol. The overall kinetics of the denaturation reaction is of the first order.

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“…[17][18][19][20] Above these, there are several related reports. [5][6][7][8][21][22][23][24] In the studies of the structural change of myoglobin by surfactant, changes of characteristic heme [25][26][27] and its environment have been examined variously, but changes of the secondary structure have been rather unnoticed.…”

Section: Introductionmentioning

confidence: 99%

Critical Temperature of Secondary Structural Change of Myoglobin in Thermal Denaturation up to 130 °C and Effect of Sodium Dodecyl Sulfate on the Change

Moriyama

Takeda

2010

J. Phys. Chem. B

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The secondary structural change of horse heart myoglobin was examined in the thermal denaturation up to 130 degrees C. The original helicity of 82% gradually decreased to 67% with rise of temperature until 75 degrees C. Thereafter, it suddenly decreased to 24% at 90 degrees C and then slightly decreased to 14% at 130 degrees C. The helices of this protein were mostly destroyed between 75 and 100 degrees C. On the other hand, upon cooling to 25 degrees C from temperatures below 75 degrees C, the helicity completely recovered to the original value, but it did not after heating to temperatures above 80 degrees C. Thus, myoglobin maintains the reversibility of the structural change up to a temperature as high as 75 degrees C. This protein had another critical temperature around 90-100 degrees C in addition to 75 degrees C in the present thermal denaturation. Upon cooling to 25 degrees C after heating to temperatures above 80 degrees C, the extent of recovered helicity decreased with rise of temperature before cooling. The additive effect of sodium dodecyl sulfate (SDS) on the structural change of myoglobin differed below and above the critical temperature at 75 degrees C. In the temperature range below 75 degrees C where the structural change was reversible, the presence of SDS cooperated with the thermal denaturation to disrupt the structure. On the contrary, the presence of the surfactant more or less restrained the decrement of helicity at high temperatures above 85 degrees C. The helicity decreased and increased with an increase of SDS concentration upon cooling to 25 degrees C after heating to temperatures below 75 degrees C and after heating to temperatures above 85 degrees C, respectively. Then, upon cooling to 25 degrees C from any temperature, the helicity settled to a magnitude around 60% in the presence of the surfactant above 0.6 mM.

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Cited by 12 publications

References 13 publications

A Calorimetric and Spectroscopic Study of DNA at Low Hydration

A Calorimetric and Spectroscopic Study of DNA at Low Hydration

The Endothermic Effects during Denaturation of Lysozyme by Temperature Modulated Calorimetry and an Intermediate Reaction Equilibrium

Critical Temperature of Secondary Structural Change of Myoglobin in Thermal Denaturation up to 130 °C and Effect of Sodium Dodecyl Sulfate on the Change

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