A study of multi-ligand beta-lactoglobulin complex formation

Comparing the binding interaction between β-lactoglobulin and flavonoids with different structure by multi-spectroscopy analysis and molecular docking

Four kinds of flavonoids (apigenin, naringenin, kaempferol, genistein) were skillfully selected to investigate the interaction between flavonoids and β-lactoglobulin (β-LG) by multi-spectroscopy analysis and molecular docking. Hydrogenation on C2C3 double bond weakened the affinity of apigenin for β-LG and it's most obvious, followed by hydroxylation of C3 and position isomerism of phenyl ring B. The main interaction force for apigenin and naringenin binding to β-LG (van der Waals forces and hydrogen bonds) was different from that of genistein and kaempferol (hydrophobic interactions). Circular dichroism and fluorescence experiments indicated that conformation of β-LG became loose and surface hydrophobicity of β-LG was reduced in the presence of flavonoids. Molecular docking indicated that flavonoids interacted with specific amino acid residues located on the outer surface of β-LG. These findings can provide a deep understanding about the interaction mechanism between flavonoids and protein, and it may be valuable in dairy incorporation with flavonoids.

The interaction of beta-lactoglobulin with ciprofloxacin and kanamycin; a spectroscopic and molecular modeling approach

A vast research has been conducted to find suitable and safe carriers for vital and pH-sensitive drugs including antibiotics. This article reports the use of easily accessible and abundant purified beta-lactoglobulin (β-LG) protein as the potential carrier of widely used Kanamycin (Kana) and Ciprofloxacin (Cip) antibiotics. Spectroscopic techniques (Fluorescence, UV-vis, Circular Dichroism) combined with molecular docking were used to determine the binding mechanism of these drugs. Fluorescence studies showed moderate binding affinity with the calculated binding constants KCip = 60.1 (±0.2) × 103 M-1 and Kkana = 2.5 (±0.6) × 103 M-1 with the order of Cip > Kana. Results of UV-vis were consistent with fluorescence measurements and demonstrated a stronger complexation for Cip rather than Kana. The secondary structure of β-LG was preserved upon interaction with Kana; however, a reduction in β-sheet content from 39.1 to 31.9% was convoyed with an increase in α-helix from 12.8 to 20.5% due to complexation of Cip. Molecular docking studies demonstrated that preferred binding sites of these drugs are not the same and several amino acids are involved in stabilizing the interaction. Based on the achieved results, Kana and Cip can spontaneously bind to β-LG and this protein may serve as their transport vehicle.

Formation of a Multiligand Complex of Bovine Serum Albumin with Retinol, Resveratrol, and (-)-Epigallocatechin-3-gallate for the Protection of Bioactive Components

Clarification of the interaction mechanisms between proteins and bioactive components is important to develop effective carriers for encapsulation and protection of bioactive components. Bovine serum albumin (BSA), a globular protein in serum and milk, contains multiple sites to bind a variety of low-molecular-weight molecules, forming protein-monoligand complexes. In this study, the interactions of BSA with retinol, resveratrol, and/or (-)-epigallocatechin-3-gallate (EGCG) were investigated by using fluorescence, circular dichroism, and molecular docking techniques. BSA-triligand complexes were successfully formed when added in the sequence of retinol, resveratrol, and EGCG. The stability of these bioactive components was improved in the complexes relative to free ones. The complexes provided a better protective effect on retinol and resveratrol than did BSA-monoligand complexes, in which the presence of EGCG played an important role.

β-Lactoglobulin: An efficient nanocarrier for advanced delivery systems

Thanks to the progress of nanotechnology there are several agent-delivery systems that can be selected to achieve rapid and specific delivery of a wide variety of biologically active agents. Consequently, the manipulation and engineering of biopolymers has become one of the most exciting subjects for those who study delivery systems on the nanoscale. In this regard, both nanoparticle formation and a carrier role have been observed in the case of the globular milk whey protein, β-lactoglobulin (β-LG), setting it apart from many other proteins. To date, many efforts adopting different approaches have created β-LG nanoparticles useful in forming delivery systems for various agents with specific targets. In this review, the potential of β-LG to play the role of an efficient and diverse carrier protein, as well as its ability to form a well-targeted nano-scale delivery system is discussed.

Binding of Folic Acid Induces Specific Self-Aggregation of Lactoferrin: Thermodynamic Characterization

In the study presented here, we investigated the interaction at pH 5.5 between folic acid (FA) and lactoferrin (LF), a positively charged protein. We found a binding constant Ka of 10(5) M(-1) and a high stoichiometry of 10 mol of FA/mol of LF. The size and charge of the complexes formed evolved during titration experiments. Increasing the ionic strength to 50 mM completely abolished the isothermal titration calorimetry (ITC) signal, suggesting the predominance of electrostatic interactions in the exothermic binding obtained. We developed a theoretical model that explains the complex triphasic ITC profile. Our results revealed a two-step mechanism: FA/LF interaction followed by self-association of the complexes thus formed. We suggest that 10 FA molecules bind to LF to form saturated reactive complexes (FA10/LF) that further self-associate into aggregates with a finite size of around 15 nm. There is thus a critical saturation degree of the protein, above which the self-association can take place. We present here the first results that provide comprehensive details of the thermodynamics of FA/LF complexation-association. Given the high stoichiometry, allowing a load of 55 mg of FA/g of LF, we suggest that FA/LF aggregates would be an effective vehicle for FA in fortified drinks.

Isolation and purification of beta-lactoglobulin from cow milk

Aim:

The present study was undertaken to standardize a convenient method for isolation and purification of β-lactoglobulin (β-lg) from cow milk keeping its antigenicity intact, so that the purified β-lg can be used for detection of cow milk protein intolerance (CMPI).

Materials and Methods:

Raw milk was collected from Gir breed of cattle reared in Haringhata Farm, West Bengal. Milk was then converted to skimmed milk by removing fat globules and casein protein was removed by acidification to pH 4.6 by adding 3 M HCl. β-lg was isolated by gel filtration chromatography using Sephacryl S-200 from the supernatant whey protein fraction. Further, β-lg was purified by anion-exchange chromatography in diethylaminoethyl-sepharose. Molecular weight of the purified cattle β-lg was determined by 15 percent one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and was analyzed by gel documentation system using standard molecular weight marker.

Results:

The molecular weight of the purified cattle β-lg was detected as 17.44 kDa. The isolated β-lg was almost in pure form as the molecular weight of purified β-lg monomer is 18kDa.

Conclusion:

The study revealed a simple and suitable method for isolation of β-lg from whey protein in pure form which may be used for detection of CMPI.

Encapsulation of testosterone and its aliphatic and aromatic dimers by milk beta-lactoglobulin

The encapsulation of testosterone and it aliphatic dimer (alip) and aromatic dimer (arom) with milk β-lactoglobulin (β-LG) was studied in aqueous solution at pH 7.4. Multiple spectroscopic methods, transmission electron microscopy (TEM) and molecular modeling were used to characterize testosterone-β-LG binding and protein aggregation process. Spectroscopic analysis showed that steroids bind β-LG via hydrophobic and H-bonding interactions with overall binding constants K test-β-LG = 5.6 (± 0.6) × 10(4)M(-1), K test-dimeralip-β-LG = 4.8 (± 0.5) × 10(3)M(-1) and K test-dimer-arom-β-LG = 2.9 (± 0.4) × 10(4)M(-1). The binding affinity was testosterone > testosterone dimer-aromatic > testosterone dimer-aliphatic. Transmission electron microscopy showed major changes in protein morphology as testosterone-protein complexation occurred with increase in the diameter of the protein aggregate indicating encapsulation of steroids by β-LG. Modeling showed the presence of H-bonding stabilized testosterone-β-LG complexes with the free binding energy of -9.82 Kcal/mol indicating that the interaction process is spontaneous at room temperature.