Spectroscopic investigation on the interaction of CHAPS, the zwitterionic steroidal surfactant, with bovine and human serum albumins: A comparative study

CHAPS, the zwitterionic derivative of cholic acid, has garnered significant research attention owing to its biocompatibility, electro-neutrality over a wide pH range, and non-denaturing nature towards proteins. The escalating demand of CHAPS in biomedical and pharmaceutical industries mandates information on its interaction with various biological macromolecules, especially proteins. The present study involves a comprehensive investigation on the interaction of CHAPS in a wide concentration range (0.001 mM-32 mM), with two extensively used transport proteins, BSA (Bovine Serum Albumin) and HSA (Human Serum Albumin). The study suggests a concentration dependent sequential interaction of CHAPS in discreet stages with the two proteins. A detailed study using warfarin and ibuprofen as site markers provides information about the sites of interaction at different stages. The study indicates significant difference in the effect of CHAPS on these two homologous proteins in terms of their esterase-like activity and effect of chemical denaturant. Moreover, a comparison between CHAPS and its structural bile salt analogues, Sodium cholate and Sodium taurocholate, towards their interaction and effect on the two serum albumins, reveals the mildness of CHAPS towards the proteins, thus endorsing it as a more suitable drug carrier in comparison to its bile salt analogues.

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.

Synthesis and evaluation of sulfosuccinate-based surfactants as counterions for hydrophobic ion pairing

Hydrophobic ion pairing is a promising strategy to raise the lipophilic character of therapeutic peptides and proteins. In past studies, docusate, an all-purpose surfactant with a dialkyl sulfosuccinate structure, showed highest potential as hydrophobic counterion. Being originally not purposed for hydrophobic ion pairing, it is likely still far away from the perfect counterion. Thus, within this study, docusate analogues with various linear and branched alkyl residues were synthesized to derive systematic insights into which hydrophobic tail is most advantageous for hydrophobic ion pairing, as well as to identify lead counterions that form complexes with superior hydrophobicity. The successful synthesis of the target compounds was confirmed by FT-IR, ¹H-NMR, and ¹³C-NMR. In a screening with the model protein hemoglobin, monostearyl sulfosuccinate, dioleyl sulfosuccinate, and bis(isotridecyl) sulfosuccinate were identified as lead counterions. Their potential was further evaluated with the peptides and proteins vancomycin, insulin, and horseradish peroxidase. Dioleyl sulfosuccinate and bis(isotridecyl) sulfosuccinate significantly increased the hydrophobicity of the tested peptides and proteins determined as logP or lipophilicity determined as solubility in 1-octanol, respectively, in comparison to the gold standard docusate. Dioleyl sulfosuccinate provided an up to 8.3-fold higher partition coefficient and up to 26.5-fold higher solubility in 1-octanol than docusate, whereas bis(isotridecyl) sulfosuccinate resulted in an up to 6.7-fold improvement in the partition coefficient and up to 44.0-fold higher solubility in 1-octanol. The conjugation of highly lipophilic alkyl tails to the polar sulfosuccinate head group allows the design of promising counterions for hydrophobic ion pairing. STATEMENT OF SIGNIFICANCE: Hydrophobic ion pairing enables efficient incorporation of hydrophilic molecules into lipid-based formulations by forming complexes with hydrophobic counterions. Docusate, a sulfosuccinate with two branched alkyl tails, has shown highest potential as anionic hydrophobic counterion. As it was originally not purposed for hydrophobic ion pairing, its structure is likely still far away from the perfect counterion. To improve its properties, analogues of docusate with various alkyl tails were synthesized in the present study. The investigation of different alkyl residues allowed to derive systematic insights into which tail structures are most favorable for hydrophobic ion pairing. Moreover, the lead counterions dioleyl sulfosuccinate and bis(isotridecyl) sulfosuccinate bearing highly lipophilic alkyl tails provided a significant improvement in the hydrophobicity of the resulting complexes.

Interaction of Bis-Guanidinium Acetates Surfactants with Bovine Serum Albumin Evaluated by Spectroscopy

The interactions between cocopropane bis-guanidinium acetates, tallowpropane bis-guanidinium acetates with bovine serum albumin (BSA) in an aqueous solution were studied by fluorescence and circular dichroic spectroscopy measurements. The aim of the study was to elucidate the influence of the hydrophilic group and the length of the hydrophobic chain of these surfactants on the mechanism of binding to BSA. The results revealed that for both surfactants, at low concentrations, the Stern–Volmer plots had an upward curvature and at high concentrations, the quenching efficiency was decreased with increase in surfactant concentration. Different thermodynamics parameters demonstrated the existence of hydrogen bond and van der Waals force which acting as binding forces. Static quenching was observed among the protein and surfactant. The conformation of BSA was changed at higher surfactant concentrations as shown by synchronous fluorescence and CD spectroscopy. This work reveals the mechanism and binding characteristics between guanidine surfactants and protein, and provided the basis for further applications of surfactants.

Structural alteration of myoglobin with two homologous cationic surfactants and effect of β-cyclodextrin: multifaceted insight and molecular docking study

Structural alteration and regeneration of myoglobin.

Unraveling the interaction of hemoglobin with a biocompatible and cleavable oxy-diester-functionalized gemini surfactant

Surfactant-protein mixtures have attracted considerable research interest in recent years at the interface of chemical biology and medicinal chemistry. Herein, the interaction between a green gemini surfactant (C₁₆-E2O-C₁₆) and a redox protein hemoglobin was examined through a series of in vitro experimental techniques with an attempt to provide a comprehensive knowledge of the surfactant-protein binding interactions. Quantitative appraisal of the fluorescence/CV data showed that the binding of C₁₆-E2O-C₁₆ to Hb leads to the formation of thermodynamically favorable non-covalent adduct with 1:1 stoichiometry. UV-vis spectra demonstrated that the effect of C₁₆-E2O-C₁₆ on Hb is highly concentration dependent. Far-UV and near-UV CD spectra together elucidated the formation of molten globule state of Hb upon C₁₆-E2O-C₁₆ addition. Temperature dependent CD explicated the effect of C₁₆-E2O-C₁₆ on the thermal stability of Hb. Furthermore, the structural investigation of Hb via pyrene/synchronous/three-dimensional fluorescence and FT-IR spectroscopy provided the complementary information related to its microenvironmental and conformational changes. Computational studies delineated that C₁₆-E2O-C₁₆ binds in the vicinity of β-37 Trp at the α₁β₂ interface of Hb. Overall, this study is expected to clarify the binding mechanism between Hb/other congeners and surfactant at the molecular level that are known to have immense potential in biomedical and industrial areas.

Binding interaction of an anionic amino acid surfactant with bovine serum albumin: physicochemical and spectroscopic investigations combined with molecular docking study

Exploration of binding interaction between anionic amino acid surfactant and BSA.