Combined voltammetric and spectroscopic analysis of small molecule–biopolymer interactions: The levodopa and serum albumin system

Functionalization of Fe3O4/rGO magnetic nanoparticles with resveratrol and in vitro DNA interaction

Based on the previous research, we found that the magnetic nanocomposite Fe₃O₄/rGO (reduced graphene oxide) has a good drug loading effect. Therefore, in this paper, we studied the positive role of Fe₃O₄/rGO as a drug carrier in the interaction between resveratrol (RES) and calf-thymus DNA (ct-DNA). The fluorescence experiment is used to evaluate by the Stern-Volmer equation, the quenching constant of RES - ct-DNA system with and without Fe₃O₄/rGO decreases with the increasing temperature. It was found the quenching mode of RES - ct-DNA and Fe₃O₄/rGO - RES - ct-DNA systems were all static quenching, but the binding constant of RES -ct-DNA increased from 4.14 ± 0.21 × 10⁴ L mol^-1 to 10.12 ± 0.02 × 10⁴ L mol^-1. It was found that Fe₃O₄/rGO formed a ternary complex with RES and ct-DNA by ultraviolet spectrum (UV-vis), resonance light scattering experiments (RLS) and scanning electron microscope (SEM). Meanwhile, Fourier transform infrared (FT-IR) and circular dichroism (CD) experiments show that Fe₃O₄/rGO and Fe₃O₄/rGO loaded with RES have effect on the secondary structure of ct-DNA and change the conformation of ct-DNA. On the cellular level, the comet assay shows that Fe₃O₄/rGO and Fe₃O₄/rGO - RES could not cause DNA strand break to the mouse hepatocytes after 24 co-incubation. These results confirm that Fe₃O₄/rGO nanocomposites have good application potential, which can be used as a good drug carrier in a wide range of therapeutic methods.

Chemometrics in investigation of small molecule-biomacromolecule interactions: A review

Chemometrics is chemical discipline in which mathematical and statistical methods are coupled with chemical data to extract useful information which cannot be extracted by the use of conventional methods. When experimental techniques are assisted by chemometric methods, very interesting studies will be performed which enable us to obtain valuable information about the system under our study. Chemico-biological interactions are very useful studies which are performed to obtain information about binding of small molecules with biological macromolecules. Recently, these studies have been assisted by chemometric methods to perform advanced studies which can help us to have a deep insight to them. Literature survey showed us that multivariate analysis of the chemico-biological interactions is becoming popular and nowadays, chemometricians are using multivariate chemometric methods for resolving chemico-biological interactions. This article focuses on the works published in the literature to provide a background for those who are interested to work in this field and finally, the results will be discussed and concluded.

Investigation of the binding properties between levamlodipine and HSA based on MCR-ALS and computer modeling

Levamlodipine (LEE) is a drug commonly used for antihypertensive treatment in clinical therapy. The overlapping fluorescence spectra of LEE and human serum albumin (HSA) cause some trouble in analysis of interactions between them by using the classic fluorescence method. Here, the multivariate curve resolution-alternating least squares (MCR-ALS) approach was used to overcome this disadvantage. Meanwhile, the binding properties of LEE-HSA complex were then explored through computer modeling. The MCR-ALS results suggested that LEE-HSA complex was present in the mixture solution of LEE and HSA. This conclusion was then confirmed by the Stern-Volmer equation and time-resolved fluorescence experiment. The binding constant (K_a) was 2.139 × 10⁴ L·mol^-1 at 298 K. LEE was located close to the Trp-214 residue of HSA, with van der Waals forces and hydrogen bonding as main driving forces for this interaction. LEE can alter the conformation of HSA, in which the content of α-helix reduced from 57.2% to 52.3%. The Pi-Alkyl interactions contributed to maintaining the stability of the LEE-HSA complex. The results of molecular dynamics simulations showed that LEE-HSA complex was formed within 5 ns, and the particle size (R_g) of HSA was altered by the binding reaction. This study would promote better understanding of the transportation and distribution mechanisms of LEE in the human body.

Interaction between aspirin and vitamin C with human serum albumin as binary and ternary systems

Foods generally contain special ingredients which easily to interact with drugs human intaking, thus affecting drug efficacy and excretion, and even cause adverse reactions. Vitamin C (Vit. C) is abundant in fresh fruits and vegetables. It plays a regulatory role in redox metabolism, and its absence can cause scurvy. Aspirin (ASP) can be used to treat many diseases, is the earliest, common and widely used as antipyretic, analgesic and antirheumatic medicine. Human serum albumin (HSA) is the most abundant protein in vertebrate plasma and has the property of combining and transporting endogenous and exogenous substances. In this paper, the effects of Vit. C on the combination of ASP and HSA were studied by multi-spectra and voltammetric approaches. Fluorescence spectra showed that the quenching mode between Vit. C and HSA is dynamic, and the main binding force is hydrophobic force. The quenching mode between ASP and HSA is static one, and the main binding force is hydrogen bond and van der Waals force. For ternary biological system of (HSA-ASP)-Vit. C, the binding constant decreases compared with HSA-Vit. C system. However, for (HSA-Vit. C)-ASP system, the binding constant does not change when compared with binary system of HSA-ASP. Based on the technology combination of voltammetry, infrared, three-dimensional fluorescence and circular dichroism (CD), it is proved that the existence of ASP will influence the binding process of Vit. C to HSA. It could be concluded that taking Vit. C first doesn't affect the absorption of ASP and may be good for health; in contrast, it is not good to take Vit. C immediately as one have just taken ASP, because the existence of ASP reduce the absorption of Vit. C for human body.

Competitive interactions between glucose and lactose with BSA: which sugar is better for children?

The study strongly suggested that, as compared with glucose, lactose is more likely to promote the growth and development of healthy children.

Groove binding interaction between daphnetin and calf thymus DNA

The binding characteristics of daphnetin with calf thymus DNA (ctDNA) were investigated by multispectroscopic and chemometric approaches coupled with DNA viscosity measurements, melting studies and molecular docking technique. The expanded UV-vis spectral data matrix was processed by multivariate curve resolution-alternating least-squares method to obtain the concentration profiles of the components (daphnetin, ctDNA and daphnetin-ctDNA complex) to quantitatively monitor the daphnetin-ctDNA interaction. The groove mode of daphnetin binding to ctDNA was concluded by little change in melting temperature, viscosity of ctDNA and iodide quenching effect as well as increase in single-stranded DNA quenching effect. Moreover, the quantitative data for the competitive binding between daphnetin and Hoechst 33258 for ctDNA obtained by resolving the three-way synchronous fluorescence spectra data using parallel factor analysis modeling further supported the groove binding. The molecular docking visualized the results of the Fourier transform infrared analysis that the adenine and thymine bases in the minor groove of ctDNA were the main binding sites for daphnetin, and the circular dichroism spectra showed that the groove binding of daphnetin to ctDNA led to the conformational change in ctDNA from B-form to A-form. This study revealed the interaction mechanism of daphnetin with ctDNA.

Spectroscopic studies on the interaction between tetrandrine and two serum albumins by chemometrics methods

The binding interactions of tetrandrine (TETD) with bovine serum albumin (BSA) and human serum albumin (HSA) have been investigated by spectroscopic methods. These experimental data were further analyzed using multivariate curve resolution-alternating least squares (MCR-ALS) method, and the concentration profiles and pure spectra for three species (BSA/HSA, TETD and TETD-BSA/HSA) existed in the interaction procedure, as well as, the apparent equilibrium constants Kapp were evaluated. The binding sites number n and the binding constants K were obtained at various temperatures. The binding distance between TETD and BSA/HSA was 1.455/1.451nm. The site markers competitive experiments indicated that TETD primarily bound to the tryptophan residue of BSA/HSA within site I. The thermodynamic parameters (ΔG, ΔH and ΔS) calculated on the basis of different temperatures revealed that the binding of TETD-BSA was mainly depended on the hydrophobic interaction strongly and electrostatic interaction, and yet the binding of TETD-HSA was strongly relied on the hydrophobic interaction. The results of synchronous fluorescence, 3D fluorescence and FT-IR spectra show that the conformation of proteins has altered in the presence of TETD. In addition, the effect of some common ions on the binding constants between TETD and proteins were also discussed.

Investigation the interaction of Daphnin with human serum albumin using optical spectroscopy and molecular modeling methods

The interaction between Daphnin with human serum albumin has been studied for the first time by spectroscopic methods including fluorescence quenching technology, circular dichroism (CD) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy under simulative physiological conditions. The results of fluorescence titration revealed that Daphnin can quench the intrinsic fluorescence of HSA by static quenching and there is a single class of binding site on HSA. In addition, the studies of CD spectroscopy and FT-IR spectroscopy showed that the protein secondary structure changed with increases of α-helices at the drug to protein molar ratio of 2. Furthermore, the thermodynamic functions ΔH(0) and ΔS(0) for the reaction were calculated to be 11.626 kJ mol(-1) and 118.843 J mol(-1)K(-1) according to Van't Hoff equation. The thermodynamic parameters (ΔH(0) and ΔS(0)) and the molecular modeling study indicated that hydrophobic force played an important role to stabilize the Daphnin-HSA complex, and Daphnin could bind within the subdomain IIA of the HSA.