Spectroscopic study on binding of gentisic acid to bovine serum albumin

Spectroscopy combined with spatiotemporal multiscale strategy to study the adsorption mechanism of soybean protein isolate with meat flavor compounds (furan): Differences in position and quantity of the methyl

The interaction mechanism between soybean protein isolate (SPI) and furan flavor compounds with different structures is studied using spectroscopy, molecular docking, and MD simulation methods. The order of binding ability between SPI and furan flavor compounds is 2-acetylfuran>furfural>5-methylfurfural. The structural differences (position and quantity of methyl groups) of three furan flavor compounds are key factors leading to the different adsorption abilities of SPI for furan flavor compounds. The findings from spectroscopy analyses suggest that the interaction between SPI and furan flavor compounds involves both static and dynamic quenching mechanisms, with static quenching being the main factor. Molecular docking and MD simulations reveal the atomic-level mechanisms underlying the stable binding for SPI and furan flavor compounds at spatiotemporal multiscale. This study provides a theoretical framework for the production and adjustment of meat essence formula in the production of soybean protein-based meat products.

Unusually High Affinity of the PLK Inhibitors RO3280 and GSK461364 to HSA and Its Possible Pharmacokinetic Implications

The binding processes of two Polo-like kinase inhibitors, RO3280 and GSK461364, to the human serum albumin (HSA) protein as well as the protonation equilibria of both compounds have been studied combining absorbance and fluorescence spectroscopy experiments together with density functional theory calculations. We found that the charge states of RO3280 and GSK461364 are +2 and +1, respectively, at the physiological pH. Nevertheless, RO3280 binds to HSA in the charge state +1 prior to a deprotonation pre-equilibrium. Binding constants to site I of HSA of 2.23 × 10⁶ and 8.80 × 10⁴ M^-1 were determined for RO3280 and GSK461364, respectively, at 310 K. The binding processes of RO3280 and GSK461364 to HSA are entropy- and enthalpy-driven, respectively. The positive enthalpy found for the RO3280-HSA complex formation could be related to a proton pre-equilibrium of RO3280.

Non-covalent interactions of selected flavors with pea protein: Role of molecular structure of flavor compounds

The influence of the molecular structures of flavor compounds (specifically, variations in chain length and functional groups) on the binding of the flavor compounds (Z)-2-penten-1-ol, hexanal, and (E)-2-octenal to pea protein was investigated. The results showed that the molecular structures of the flavor compounds strongly influenced their binding affinity for pea protein. Specifically, (E)-2-octenal exhibited a higher binding affinity and a higher Stern-Volmer constant with pea protein than both hexanal and (Z)-2-penten-1-ol. Thermodynamic analysis indicated that the flavor compound-pea protein interactions were spontaneous. Hydrophobic interactions were dominant in the non-covalent interactions between (E)-2-octenal/(Z)-2-penten-1-ol and pea protein, whereas hydrogen bonding was dominant in the non-covalent interactions between hexanal and pea protein. Surface hydrophobicity measurements, the use of bond-disrupting agents, and molecular docking further supported the hypothesis that hydrogen bonding, as well as hydrophobic interactions, occurred between the flavor compounds and pea protein.

Typical Umami Ligand-Induced Binding Interaction and Conformational Change of T1R1-VFT

Umami taste receptor type 1 member 1/3 (T1R1/T1R3) heterodimer has multiple ligand-binding sites, most of which are located in T1R1-Venus flytrap domain (T1R1-VFT). However, the critical binding process of T1R1-VFT/umami ligands remains largely unknown. Herein, T1R1-VFT was prepared with a sufficient amount and functional activity, and its binding characteristics with typical umami molecules (monosodium l-glutamate, disodium succinate, beefy meaty peptide, and inosine-5'-monophosphate) were explored via multispectroscopic techniques and molecular dynamics simulation. The results showed that, driven mainly by hydrogen bond, van der Waals forces, and electrostatic interactions, T1R1-VFT bound to umami compound at 1:1 (stoichiometric interaction) and formed T1R1-VFT/ligand complex (static fluorescence quenching) with a weak binding affinity (K_a values: 252 ± 19 to 1169 ± 112 M^-1). The binding process was spontaneous and exothermic (ΔG, -17.72 to -14.26 kJ mol^-1; ΔH, -23.86 to -12.11 kJ mol^-1) and induced conformational changes of T1R1-VFT, which was mainly reflected in slight unfolding of α-helix (Δα-helix < 0) and polypeptide chain backbone structure. Meanwhile, the binding of the four ligands stabilized the active conformation of the T1R1-VFT pocket. This work provides insight into the binding interaction between T1R1-VFT/umami ligands and improves understanding of how umami receptor recognizes specific ligand molecules.

Interaction Mechanism of Mangiferin and Ovalbumin Based on Spectrofluorimetry and Molecular Docking

Mangiferin (MAG) is a kind of polyphenol with many bioactivities. However, its application in medicines and functional foods is restricted because of its poor aqueous solubility and stability. The construction of a MAG/protein complex is an effective way to solve this bottleneck. In this study, the interaction of MAG and ovalbumin (OVA) was systematically investigated by spectrofluorimetry, and their binding mode was clarified based on molecular docking. The results suggested that MAG could cause the static fluorescence quenching of OVA with the quenching constant ( Kq) of >2 × 1010 L/(mol·s). Their binding performance increased with increasing temperature, and the binding-site number ( n) was close to 1. The thermodynamic analysis indicated that the binding was a spontaneous process, which was mainly driven by hydrophobic force. During this process, there was no apparent change in the microenvironment surrounding the tyrosine and tryptophan residues of OVA. The molecular docking results demonstrated the hydrophobic interaction and hydrogen bonding in the complex, which well-confirmed the results of the fluorescence experiments.

Shedding light on the binding mechanism of kinase inhibitors BI-2536, Volasetib and Ro-3280 with their pharmacological target PLK1

In the present work, the interactions of the novel kinase inhibitors BI-2536, Volasetib (BI-6727) and Ro-3280 with the pharmacological target PLK1 have been studied by fluorescence spectroscopy and molecular dynamics calculations. High Stern-Volmer constants were found in fluorescence experiments suggesting the formation of stable protein-ligand complexes. In addition, it was observed that the binding constant between BI-2536 and PLK1 increases about 100-fold in presence of the phosphopeptide Cdc25C-p that docks to the polo box domain of the protein and releases the kinase domain. All the determined binding constants are higher for the kinase inhibitors than for their competitor for the active center (ATP) being BI-2536 and Volasertib the inhibitors that showed more affinity for PLK1. Calculated binding free energies confirmed the higher affinity of PLK1 for BI-2536 and Volasertib than for ATP. The higher affinity of the inhibitors to PLK1 compared to ATP was mainly attributed to stronger van der Waals interactions. Results may help with the challenge of designing and developing new kinase inhibitors more effective in clinical cancer therapy.

Exploration of the binding between ellagic acid, a potentially risky food additive, and bovine serum albumin

Ellagic acid (EA), a natural plant polyphenol, is usually used as a functional additive in variety of health foods. However, the potential toxicity of EA to human health should be paid enough attention. To clarify its biological toxicity in vivo, this study explored the binding mechanism of EA with bovine serum albumin (BSA) by means of spectroscopic approaches and molecular docking insimulative physiological conditions. The results showed that the mixture of BSA with EA could spontaneously cause the formation of BSA-EA complex through electrostatic interaction under simulative physiological conditions (0.01 mol·L^-1Tris-HCl, 0.015 mol L^-1 NaCl, pH = 7.4). Molecular docking experiments revealed that EA was primarily bound to the hydrophobic pocket of the site I (subdomain IIA) of BSA. It has been reported that the binding of small functional molecules to serum albumins remarkably impacts their absorption, distribution, metabolism, and excretion features. Therefore, this study might be helpful for human to have an in-depth understanding of the biological effect of EA in vivo and guide human to take it safely and reasonably.

Structure-affinity relationship of the binding of phenolic acids and their derivatives to bovine serum albumin

Phenolic acids perform biological effects which are largely influenced by their binding to serum albumin. Therefore, investigating structure-affinity relationship of binding between phenolic acids and serum albumin is important. In this study, 114 phenolic acids and their derivatives, sharing the benzoic acid core with different substituents groups, were selected to investigate structure-affinity relationships with bovine serum albumin. The binding constants were obtained through fluorescence quenching, and a comprehensive mathematical model with inner-filter effect correction was applied. The results showed that the hydroxy group at the 2-position led to stronger binding affinity, while it had a negative influence at the 4-position. Substituting hydroxy groups with methoxy groups at 4-position and with methyl groups at 3-position both strengthened the binding affinity, respectively. Hydrogen bonding was one of the key binding forces for this binding interaction. Our findings provide a fundamental insight on the binding mechanism of phenolic acids to bovine serum albumin.

Binding of the anticancer drug BI-2536 to human serum albumin. A spectroscopic and theoretical study

BI-2536 is a potent Polo-like kinase inhibitor which induces apoptosis in diverse human cancer cell lines. The binding affinity of BI-2536 for human serum albumin (HSA) protein may define its pharmacokinetic and pharmacodynamic profile. We have studied the binding of BI-2536 to HSA by means of different spectroscopic techniques and docking calculations. We have experimentally observed that the affinity of BI-2536 for HSA is higher than that of other common HSA binding drugs. Therefore, it can be postulated that the drug dose should be increased to achieve a certain concentration of free drug in plasma, although BI-2536 could also reach tumour tissues by uptaking HSA/BI-2536 complex. Only a single binding site on HSA has been observed for BI-2536 which seems to correspond to the subdomain IIA pocket. The formation of the HSA/BI-2536 complex is a spontaneous and entropy-driven process that does not cause a significant change of the secondary structure of the protein. Its endothermic character could be related to proton release. Thermodynamic analysis showed that the main protein-drug interactions are of the van der Waals type although the presence of amide and ether groups in BI-2536 could also allow H-bonding with some residues in the subdomain IIA pocket.

Analysis of binding ability of two tetramethylpyridylporphyrins to albumin and its complex with bilirubin

An interaction between 5,10,15,20-tetrakis-(N-methyl-x-pyridyl)porphyrins, x=2; 4 (TMPyPs) with bovine serum albumin (BSA) and its bilirubin (BR) complex was investigated by UV-Viz and fluorescence spectroscopy under imitated physiological conditions involving molecular docking studies. The parameters of forming intermolecular complexes (binding constants, quenching rate constants, quenching sphere radius etc.) were determined. It was showed that the interaction between proteins and TMPyPs occurs via static quenching of protein fluorescence and has predominantly hydrophobic and electrostatic character. It was revealed that obtained complexes are relatively stable, but in the case of TMPyP4 binding with proteins occurs better than TMPyP2. Nevertheless, both TMPyPs have better binding ability with free protein compared to BRBSA at the same time. The influence of TMPyPs on the conformational changes in protein molecules was studied using synchronous fluorescence spectroscopy. It was found that there is no competition of BR with TMPyPs for binging sites on protein molecule and BR displacement does not occur. Molecular docking calculations have showed that TMPyPs can bind with albumin via tryptophan residue in the hydrophilic binding site of protein molecule but it is not one possible interaction way.

Controlled release of recombinant human cementum protein 1 from electrospun multiphasic scaffold for cementum regeneration

Periodontitis is a major cause for tooth loss, which affects about 15% of the adult population. Cementum regeneration has been the crux of constructing the periodontal complex. Cementum protein 1 (CEMP1) is a cementum-specific protein that can induce cementogenic differentiation. In this study, poly(ethylene glycol) (PEG)-stabilized amorphous calcium phosphate (ACP) nanoparticles were prepared by wet-chemical method and then loaded with recombinant human CEMP1 (rhCEMP1) for controlled release. An electrospun multiphasic scaffold constituted of poly(ε-caprolactone) (PCL), type I collagen (COL), and rhCEMP1/ACP was fabricated. The effects of rhCEMP1/ACP/PCL/COL scaffold on the attachment proliferation, osteogenic, and cementogenic differentiations of human periodontal ligament cells, (PDLCs) were systematically investigated. A critical size defect rat model was introduced to evaluate the effect of tissue regeneration of the scaffolds in vivo. The results showed that PEG-stabilized ACP nanoparticles formed a core-shell structure with sustained release of rhCEMP1 for up to 4 weeks. rhCEMP1/ACP/PCL/COL scaffold could suppress PDLCs proliferation behavior and upregulate the expression of cementoblastic markers including CEMP1 and cementum attachment protein while downregulating osteoblastic markers including osteocalcin and osteopontin when it was cocultured with PDLCs in vitro for 7 days. Histology analysis of cementum after being implanted with the scaffold in rats for 8 weeks showed that there was cementum-like tissue formation but little bone formation. These results indicated the potential of using electrospun multiphasic scaffolds for controlled release of rhCEMP1 for promoting cementum regeneration in reconstruction of the periodontal complex.

Albumin-based nanoparticle trehalose lyophilisation stress-down to preserve structure/function and enhanced binding

The aim of this study was to preserve albumin nanoparticle structure/function during the lyophilisation process. Bovine serum albumin nanoparticles were obtained by γ-irradiation. Nanoparticles were lyophilised in buffer, miliQ water or in trehalose/miliQ solution. The size and charge of the nanoparticles were tested after lyophilisation by light scattering and Z potential. The most relevant results in size of BSA nanoparticle were those lyophilised in PBS between 20 and 350nm, assembled in different aggregates, and negative Z potential obtained was 37±8mV in all, and those nanoparticles lyophilised with trehalose had a size range of 70±2nm and a negative Z potential of 20±5mV. Structure determination of surface aminoacids SH groups in the BSA NP lyophilised in PBS showed an increase in the free SH groups. Different aggregates had different amount of SH groups exposure from 55 to 938 (from smaller to bigger aggregates), whereas BSA NP lyophilised with trehalose showed no significant difference if compared with BSA NP. The binding properties of the BSA nanoparticle with a theragnostic probe (merocyanine 540) were studied after lyophilisation. Results showed more affinity between the BSA NP lyophilised with trehalose than that observed with non lyophilised BSA NP. As a result, the lyophilisation condition in trehalose 100μM solution is the best one to preserve the BSA NP structure/function and the one with the enhance binding affinity of the BSA NP.