A direct comparison of the interaction of bovine serum albumin and gelatin with sodium deoxycholate in aqueous solutions

Insight into the Effect of Submicellar Concentrations of Sodium Deoxycholate on the Structure, Stability, and Activity of Bovine and Human Serum Albumin: An Interesting Comparison between Single and Double Tryptophan Proteins

The progressive escalation in the applications of bile salts in diverse fields has triggered research on their interaction with various biological macromolecules, especially with proteins. A proper understanding of the interaction process of bile salts, particularly in the lower concentrations range, with the serum albumin seems important since the normal serum concentration of bile salts is approximately in the micromolar range. The current study deals with a comprehensive and comparative analysis of the interaction of submicellar concentrations of sodium deoxycholate (NaDC) with two homologous transport proteins: bovine serum albumin (BSA) and human serum albumin (HSA). HSA and BSA with one and two tryptophans, respectively, provide the opportunity for an interesting comparison of tryptophan fluorescence behavior on interaction with NaDC. The study suggests a sequential interaction of NaDC in three discrete stages with the two proteins. A detailed study using warfarin and ibuprofen as site markers provides information about the sites of interaction, which is further confirmed by inclusive molecular dynamics simulation analysis. Moreover, the comparison of the thermodynamics and stability of the NaDC-serum albumin complexes confirms the stronger interaction of NaDC with BSA as compared to that with HSA. The differential interaction between the bile salt and the two serum albumins is further established from the difference in the extent of decrease in the esterase-like activity assay of the proteins in the presence of NaDC. Therefore, the present study provides important insight into the effect of submicellar concentrations of NaDC on the structure, stability, and activity of the two homologous serum albumins and thus can contribute not only to the general understanding of the complex nature of serum albumin-bile salt interactions but also to the design of more effective pharmaceutical formulations in the field of drug delivery and biomedical research.

Realizing enhanced luminescence of silver nanocluster-peptide soft hydrogels by PEI reinforcement

Metal nanoclusters (NCs) are a new type of fluorescent nanomaterial composed of several to several tens of metal ions or atoms with a wide range of applications in the fields of catalysis, optics, and biomedicine. However, fluorescence quenching when existing as individuals in aqueous solutions greatly limits their applications. In this study, six-core Ag(i) NCs (Ag₆-NCs) were interacted with peptides (DD-5) in water to form soft hydrogels with the aggregation-induced emission (AIE) of Ag₆-NCs. The introduction of polyethyleneimine (PEI) into the Ag₆-NCs/DD-5 hydrogel succeeded in further enhancing the fluorescence intensity. This dual-AIE behavior of the Ag₆-NCs/DD-5/PEI hydrogels is mainly ascribed to the strong hydrogen bonding among the carboxyl groups of Ag₆, those of DD-5 and the amino groups of PEI, which effectively restricted intramolecular vibration of the capping ligands on the Ag₆-NCs. Moreover, the addition of PEI can effectively promote the gelation speed of Ag₆-NCs/DD-5 and act as a physical cross-linker, leading to an increase of the mechanical strength of the hydrogel. This work opens a new pathway for the fabrication of smart composite materials with multiple functions, which show a variety of applications such as chemical/biosensing and bioimaging.

A multispectroscopic and molecular docking investigation of the binding interaction between serum albumins and acid orange dye

The interaction of Acid Orange 10 (AO10) with bovine serum albumin (BSA) was investigated comparatively with that of human serum albumin (HSA) using multispectroscopic techniques for understanding their toxic mechanism. Further, density functional theory calculations and docking studies have been carried out to gain more insights into the nature of interactions existing between AO10 and serum albumins. The fluorescence results suggest that AO10 quenched the fluorescence of BSA through the combination of static and dynamic quenching mechanism. The same trend was followed in the interaction of AO10 with HSA. In addition to the type of quenching mechanism, the fluorescence spectroscopic results suggest that the binding occurs near the tryptophan moiety of serum albumins and the binding. AO10 has more binding affinity towards BSA than HSA. An AO10-Trp model has been created to explicitly understand the CHπ interactions from Bader's quantum theory of atoms in molecules analysis which confirmed that AO10 bind more strongly with BSA than that of HSA due to the formation of three hydrogen bonds with BSA whereas it forms two hydrogen bonds in the case of HSA. These obtained results provide an in-depth understanding of the interaction of the acid azo dye AO10 with serum albumins. This interaction study provides insights into the underlying reasons for toxicity of AO10 relevant to understand its effect on bovids and humans during the blood transportation process.