✍ Scribed by Alexander E. Ivanov; Igor Yu. Galaev; Bo Mattiasson
No coin nor oath required. For personal study only.
Summary: Binding of adenosine to the thermosensitive copolymer of N‐isopropylacrylamide and 3‐(acrylamido)aminophenylboronic acid (82:18, $\overline M _{\rm n}$ = 47 000 g · mol^−1^) was studied by equilibrium dialysis at 22 °C and 37 °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 °C under the above conditions. At 22 °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 °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 × 10^−3^ M, 22 °C) very probably testifies to competition of the nucleoside with hydrophobic polyNIPAM segments for binding to the pendant phenylboronates.
Scheme of the specific complex formation between adenosine and the pendent boronate groups of AAPBA‐NIPAM copolymer.
magnified imageScheme of the specific complex formation between adenosine and the pendent boronate groups of AAPBA‐NIPAM copolymer.
📜 SIMILAR VOLUMES