Ivanov Alexander E, Galaev Igor Yu, Mattiasson Bo
Department of Biotechnology, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, S-221 00 Lund, Sweden.
Macromol Biosci. 2005 Aug 12;5(8):795-800. doi: 10.1002/mabi.200500035.
Binding of adenosine to the thermosensitive copolymer of N-isopropylacrylamide and 3-(acrylamido)aminophenylboronic acid (82:18, Mn = 47,000 g . mol(-1)) was studied by equilibrium dialysis at 22 degrees C and 37 degrees C, in a 0.1 M glycine buffer containing 0.1 M NaCl at pH 9.2. The copolymer exhibited a the phase transition temperature (T(p)) of 26.5 degrees C under the above conditions. At 22 degrees C the binding of adenosine to the water-soluble copolymer was well described by a Langmuir model, accounting for preferential ionisation of the boronate-nucleoside complexes and, therefore, restricted reactivity of the rest of boronates. At saturation, the copolymer contained 38% of its phenylboronic acid groups in the form of complexes, whereas the association constant was 1,400 M(-1). At 37 degrees C no binding of adenosine to thermally precipitated copolymer was found, presumably owing to interaction of the phenylboronates with hydrophobic segments of polyNIPAM. At high loading of the copolymer by the reversibly bound adenosine the T(p) steeply increases with increasing fraction of the phenylboronate-adenosine complexes in the chains. The increase of the T(p) observed above the saturating adenosine concentration (>1 x 10(-3) M, 22 degrees C) very probably testifies to competition of the nucleoside with hydrophobic polyNIPAM segments for binding to the pendant phenylboronates.
在22℃和37℃下，于pH 9.2、含有0.1 M NaCl的0.1 M甘氨酸缓冲液中，通过平衡透析研究了腺苷与N-异丙基丙烯酰胺和3-(丙烯酰胺基)氨基苯硼酸的热敏共聚物（82:18，Mn = 47,000 g·mol⁻¹）的结合情况。在上述条件下，该共聚物的相转变温度（T(p)）为26.5℃。在22℃时，腺苷与水溶性共聚物之间的结合可用Langmuir模型很好地描述，该模型考虑了硼酸酯 - 核苷络合物的优先电离，因此硼酸酯其余部分的反应活性受到限制。在饱和时，共聚物中38%的苯基硼酸基团以络合物形式存在，而缔合常数为1400 M⁻¹。在37℃时，未发现腺苷与热沉淀共聚物有结合，这可能是由于苯基硼酸酯与聚NIPAM的疏水链段相互作用所致。当共聚物被可逆结合的腺苷高负载时，T(p)会随着链中苯基硼酸酯 - 腺苷络合物比例的增加而急剧升高。在饱和腺苷浓度（>1×l0⁻³ M，22℃）以上观察到的T(p)升高很可能证明了核苷与疏水聚NIPAM链段竞争与侧链苯基硼酸酯结合这一情况。
