缓冲液中DSC扫描检测方案(差示扫描量热)

智能文字提取功能测试中

M133 Choice of Buffers For a DSC Scan Christin T. Choma TA Instruments， 109 Lukens Drive， New Castle， DE 19720，USA Ithoughitis oftenassumed thatthepHofabufferAsolution remains constant during a differentialiscanning calorimetry (DSC) experiment， the pKof a buffer can in fact change significantly between0℃ and 100℃.Such pH changes can result in sampledenaturation，aggregation and precipitationthat，intheabsence of knowledge about the temperature stabilityof the buffer， could erroneously be ascribed solely totemperature-induced unfolding of the biomolecule. The table below is a compilation of calculated pKvalues of common biological buffers as a function oftemperature： Phosphate produces the most temperature-stablebuffer in the physiological pH range 7.0 to 7.7.All buffers should be prepared using thoroughly-degassed ultra-pure water， and be briefly degassedagain immediately prior to use. Addition of thermallyunstable additives such as bacteriocides should beavoided.Dithiothreitol is preferable as a reducingagent to mercaptoethanol， which oxidizessandthermally denatures easily. Temp(°C) acetate MES PIPES Phos BES MOPS TES HEPES Tris Bicine TAPS CAPS 0 4.73 6.35 6.98 6.92 7.40 7.44 7.93 7.73 8.98 8.63 8.97 11.06 10 4.71 6.24 6.90 6.86 7.23 7.30 7.71 7.58 8.65 8.45 8.69 10.74 20 4.70 6.15 6.84 6.82 7.08 7.16 7.50 7.46 8.34 8.28 8.42 10.43 30 4.70 6.06 6.77 6.79 6.93 7.04 7.31 7.34 8.06 8.12 8.18 10.15 40 4.70 5.97 6.70 6.77 6.79 6.91 7.13 7.22 7.81 7.97 7.95 9.88 50 4.71 5.89 6.64 6.76 6.86 6.80 6.98 7.11 7.57 7.83 7.74 9.63 60 4.73 5.81 6.58 6.78 6.54 6.69 6.81 7.00 7.35 7.70 7.54 9.39 70 4.75 5.74 6.53 6.77 6.42 6.58 6.66 6.89 7.15 7.58 7.38 9.16 80 4.78 5.67 6.47 6.79 6.31 6.48 6.53 6.79 6.96 7.46 7.18 8.94 90 4.81 5.60 6.42 6.82 6.21 6.38 6.40 6.69 6.76 7.35 7.02 8.74 100 4.84 5.53 6.37 6.85 6.11 6.28 6.29 6.60 6.62 7.25 6.87 8.84 (Phos：phosphate. Values from H.Fukada and K. Takahashi (1987)，Laboratory of Biophysical Chemistry， College of Agriculture，Sakai，Osaka，Japan.) Although it is often assumed that the pH of a buffer solution remains constant during a differential scanning calorimetry (DSC) experiment, the pK of a buffer can in fact change signifi cantly between 0 oC and 100 oC. Such pH changes can result in sample denaturation, aggregation and precipitation that, in the absence of knowledge about the temperature stability of the buffer, could erroneously be ascribed solely to temperature-induced unfolding of the biomolecule.