Binding Studies of AICAR and Human Serum Albumin by Spectroscopic, Theoretical, and Computational Methodologies

Abstract

The interactions of small molecule drugs with plasma serum albumin are important because of the influence of such interactions on the pharmacokinetics of these therapeutic agents. 5-Aminoimidazole-4-carboxamide ribonucleoside (AICAR) is one such drug candidate that has recently gained attention for its promising clinical applications as an anti-cancer agent. This study sheds light upon key aspects of AICAR’s pharmacokinetics, which are not well understood. We performed in-depth experimental and computational binding analyses of AICAR with human serum albumin (HSA) under simulated biochemical conditions, using ligand-dependent fluorescence sensitivity of HSA. This allowed us to characterize the strength and modes of binding, mechanism of fluorescence quenching, validation of FRET, and intermolecular interactions for the AICAR–HSA complexes. We determined that AICAR and HSA form two stable low-energy complexes, leading to conformational changes and quenching of protein fluorescence. Stern–Volmer analysis of the fluorescence data also revealed a collision-independent static mechanism for fluorescence quenching upon formation of the AICAR–HSA complex. Ligand-competitive displacement experiments, using known site-specific ligands for HSA’s binding sites (I, II, and III) suggest that AICAR is capable of binding to both HSA site I (warfarin binding site, subdomain IIA) and site II (flufenamic acid binding site, subdomain IIIA). Computational molecular docking experiments corroborated these site-competitive experiments, revealing key hydrogen bonding interactions involved in stabilization of both AICAR–HSA complexes, reaffirming that AICAR binds to both site I and site II.

Aflatoxin B1 Induced Structural and Conformational Changes in Bovine Serum Albumin: A Multispectroscopic and Circular Dichroism-Based Study

“…This result confirms conformational changes in proteins and corroborates our UV absorbance spectroscopic and fluorescence spectroscopic findings. Our findings are consistent with the previous studies on the interaction of small molecules with BSA. , The intensities and wavelengths corresponding to different fluorescence peaks are shown in Table .…”

A Comprehensive Spectroscopic Analysis of the Ibuprofen Binding with Human Serum Albumin, Part II

“…The obtained results indicate that stronger complexes were formed with increasing temperature, which means a lower therapeutic effect. Peng made similar conclusions in the study concerning the interaction between coenzyme Q 10 and human serum albumin and Hashempour in analyzing the interaction between HSA and 5-aminoimidazole-4carboxamide ribonucleoside [3,47]. They observed that the K SV value increases with temperature.…”

Recrystallization of Adenosine for Localized Drug Delivery

“…The Stern–Volmer analysis ( F 0 / F vs conc.) yielded positive deviations at all three temperatures (Figure B), indicating the presence of transient intermolecular collision (dynamic) and stable binding (static) modes of interactions. − These results suggest that albumin may serve as a solubilizer of ADO in the crystalline suspension (Figure ) and may be considered a method for producing cocrystals …”