Poly(amidoamine) dendrimer-methotrexate conjugates: the mechanism of interaction with folate binding protein.

Generation 5 poly(amidoamine) (G5 PAMAM) methotrexate (MTX) conjugates employing two small molecular linkers, G5-(COG-MTX)n, G5-(MFCO-MTX)n were prepared along with the conjugates of the G5-G5 (D) dimer, D-(COG-MTX)n, D-(MFCO-MTX)n. The monomer G5-(COG-MTX)n conjugates exhibited only a weak, rapidly reversible binding to folate binding protein (FBP) consistent with monovalent MTX binding. The D-(COG-MTX)n conjugates exhibited a slow onset, tight-binding mechanism in which the MTX first binds to the FBP, inducing protein structural rearrangement, followed by polymer-protein van der Waals interactions leading to tight-binding.

An isothermal titration and differential scanning calorimetry study of the G-quadruplex DNA-insulin interaction.

The binding of insulin to the G-quadruplexes formed by the consensus sequence of the insulin-linked polymorphic region (ILPR) was investigated with differential scanning calorimetry (DSC) and isothermal titration calorimetry (ITC). The thermal denaturation temperature of insulin was increased by almost 4 °C upon binding to ILPR G-quadruplex DNA as determined by DSC. The thermodynamic parameters (K(D), ΔH, ΔG, and ΔS) of the insulin-G-quadruplex complex were further investigated by temperature-dependent ITC measurement over the range of 10-37 °C.