The interaction of Bovine Serum Albumin (BSA) with limonene has been studied by UV-visible spectroscopy, fluorescence spectroscopy and molecular docking, and its effects on protein conformation, topology and stability were determined by Circular Dichroism (CD), Dynamic Light Scattering (DLS) and Differential Scanning Calorimetry (DSC). A gradual decrease in Stern–Volmer quenching constants with the increase in temperature showed the static mode of fluorescence quenching. The obtained binding constant (Kb) was ∼104 M−1. The temperature dependent Kb, Gibbs free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) changes were calculated, which revealed that the reaction is spontaneous and exothermic. The UV-visible spectra showed a change in the peaks within the aromatic region indicating hydrophobic interactions with Trp, Tyr and Phe in the protein. Moreover, limonene induced an increase in α-helical contents probably on the cost of random coils or/and β-sheets of BSA, as observed from the far-UV CD spectra. The topology of BSA in the presence of limonene was slightly altered, as obtained from DLS results. The stability was also enhanced as revealed through thermal denaturation study by DSC and CD. Molecular docking study depicted that limonene fits into the hydrophobic pocket close to Sudlow site I in domain IIA of BSA. The present study will be helpful in understanding the binding mechanism of limonene and associated stability and conformational changes.

Elucidating the interaction of limonene with bovine serum albumin: a multi-technique approach

The interactions of 3-carboxyphenoxathiin with Bovine Serum Albumin (BSA) and Human Serum Albumin (HSA) have been studied by fluorescence and circular dichroism spectroscopy. The binding of 3-carboxyphenoxathiin quenches the BSA and HSA fluorescence, revealing a 1:1 interaction with a binding constant of about 10(5) M(-1). In addition, according to the synchronous fluorescence spectra of BSA and HSA in presence of 3-carboxyphenoxathiin, the tryptophan residues of the proteins are most perturbed by the binding process. Finally, the distance between the acceptor, 3-carboxyphenoxathiin, and the donor, BSA or HSA, was estimated on the basis of the Forster resonance energy transfer (FRET). The fluorescence results are correlated with those obtained from the circular dichroism spectra, which reveal the change of the albumin conformation during the interaction process.

https://www.mdpi.com/1420-3049/15/6/3905/pdf?view=inline

Bovine and human serum albumin interactions with 3-carboxyphenoxathiin studied by fluorescence and circular dichroism spectroscopy.

Characterization of the baicalein–bovine serum albumin complex without or with Cu2+or Fe3+ by spectroscopic approaches

Analysis of binding interaction between puerarin and bovine serum albumin by multi-spectroscopic method.

Four 2-oxo-1,2-dihydroquinoline-3-carbaldehyde N-substituted thiosemicarbazone ligands (H2-OQtsc-R, where R = H, Me, Et or Ph) and their corresponding new copper(II) complexes [CuCl2(H2-OQtsc-H)]·2H2O (1), [CuCl2(H2-OQtsc-Me)]·2H2O (2), [CuCl2(H2-OQtsc-Et)(CH3OH)]Cl (3) and [CuCl(H-OQtsc-Ph)]·CH3OH (4) have been synthesized in order to correlate the effect of terminal N-substitution on coordination behaviour, structure and biological activity. Single crystal X-ray diffraction studies revealed that the complexes 1, 2 and 3 have square pyramidal geometry around the central metal ion. In the complexes 1 and 2, the copper ion is coordinated by the ligand with ONS donor atoms, one chloride ion in apical position and the other chloride in the basal plane. Complex 3 consists of [CuCl2(H2-OQtsc-Et)(CH3OH)]+ cation and a chloride as counter ion. The copper ion is coordinated by the ligand with ONS donor atoms and by one chloride ion in the basal plane. One methanol molecule is bonded through its neutral oxygen in the apical position. Complex 4 is square planar with the ligand coordinating through uni-negative tridentate ONS− and by one chloride ion in the basal plane. The binding of complexes with lysozyme protein was carried out by fluorescence spectroscopy. Investigations of antioxidation properties showed that all the copper(II) complexes have strong radical scavenging properties. The cytotoxicity of the complexes 3 and 4 against NIH 3T3 and HeLa cell lines showed that synergy between the metal and ligands results in a significant enhancement in the cell death with IC50 of ∼10–40 μM. A size dependence of substitution at terminal N in the thiosemicarbazones on the biological activities of the complexes has been observed.

Effect of terminal N-substitution in 2-oxo-1,2-dihydroquinoline-3-carbaldehyde thiosemicarbazones on the mode of coordination, structure, interaction with protein, radical scavenging and cytotoxic activity of copper(II) complexes

The interaction between 3,3-bis(4-hydroxy-1-naphthyl)-phthalide (NPP) and bovine serum albumin (BSA) have been studied by fluorescence spectroscopy. The binding of NPP quenches the BSA fluorescence. By the fluorescence quenching results, it was found that the binding constant K  = 5.30 × 10 4  L mol −1 , and number of binding sites n  = 0.9267. In addition, according to the synchronous fluorescence spectra of BSA, the results showed that the fluorescence spectra of BSA mainly originate from the tryptophan residues. Finally, the distance between the acceptor NPP and BSA was estimated to be 1.94 nm using Foster's equation on the basis of fluorescence energy transfer. The interaction between NPP and BSA has been verified as consistent with the static quenching procedure and the quenching mechanism is related to the energy transfer.

Study on the interaction of 3,3-bis(4-hydroxy-1-naphthyl)-phthalide with bovine serum albumin by fluorescence spectroscopy

The interation of caffeine and theophylline with bovine serum albumins has been studied by fluorescence spectroscopy. The results indicated that enoxacin could bind with BSA strongly at molar ratio 1:1 and the equilibrium constants were Kc = 1.673 x 10(4) L x mol(-1) and Kt = 6.802 x 10(3) L x mol(-1), respectively. Good linear Stern-Volmer lines were observed on the fluorescence of BSA quenched by enoxacin of different concentration, indicating that the combination reaction of enoxacin with BSA is a single static quenching process.

Yan-li Wei

Papers

Study on the interaction of 3,3-bis(4-hydroxy-1-naphthyl)-phthalide with bovine serum albumin by fluorescence spectroscopy

Study on Interaction of Caffeine and Theophylline with Bovine Serum Albumins