Cationic pyridinium porphyrins appending different peripheral substituents: spectroscopic studies on their interactions with bovine serum albumin

Binding of Two Tetrasulfophthalocyanines (Fe(III) and Metal-Free) to Lysozyme: Fluorescence Spectroscopic and Computational Approach

The interactions between tetrasulfophthalocyanines and lysozyme were studied using fluorescence spectroscopic and computational analyses. Lysozyme has been found to be widely studied as an anticancer agent, however, there are few reports of its interaction with phthalocyanines. Fe(III) tetrasulfophthalocyanine (FeTSPc) and free base tetrasulfophthalocyanine (TSPc) used in this study, were synthesized by our research group. Experimental results suggested that the metalled complex FeTSPc has a much higher affinity than TSPc. The binding stoichiometry between each tetrasulfophthalocyanine and lysozyme was 1:1. Stern-Volmer analysis suggested that the fluorescence quenching proceedes through a static process. Binding thermodynamics (ΔG, ΔH and ΔS) confirmed that mainly hydrogen bonds, van der Waals, and electrostatic forces are responsible for the binding process. We carried out molecular dynamics simulations, molecular docking, and binding energy calculations. Molecular dynamics simulations yielded the most populated cluster of lysozyme structures, and a representative structure from this cluster was used for the docking studies with these phthalocyanines. 1000 poses were generated for each ligand. The strudtures of the resulting complexes revealed that Arg 73 and Arg 112 are important for the binding affinity of the tetrasulfophthalocyanines, generating mainly an electrostatic favorable environment for the SO3- groups. In addition, hydrophobic contacts were involved with Trp 62, Trp 63 and Trp 108, explaining the fluorescence quenching observed experimentally. Binding energies were determined for these models, confirming that the interactions with lysozyme were more favorable for FeTSPc compared to TSPc. The understanding of the molecular mechanisms is relevant to characterize the nature of tetrasulfophthalocyanines in photodynamic therapy.

In vitro interaction and computational studies of glycosylated photosensitizers with plasma proteins

A series of glycosylated photosensitizers (porphyrin, chlorin, and isobacteriochlorin) in the presence of plasma proteins: bovine serum albumin (BSA) and human serum albumin (HSA), were investigated in a buffer at pH 7.4, using ultraviolet-visible (UV-vis) absorption and fluorescence spectroscopies. Due to the excitation of the tryptophan residue of BSA and HSA, its fluorescence emission was monitored around 340 nm. During each titration experiment and with each addition of the corresponding glycosylated photosensitizer, there was a concentration-dependent quenching of the intrinsic fluorescence of BSA and HSA. Using Stern–Volmer and double logarithmic plots we determined that fluorescence quenching was static for all molecules. We calculated the average binding constant for BSA and HSA for each porphyrin-type compound. To support our experimental studies, computational molecular docking and molecular dynamics simulations were used to identify the binding sites and binding poses of the each of the glycosylated photosensitizers onto BSA and HSA. The three compounds are binding to the Hemin site located in the subdomain IB of BSA forming strong interactions with Trp134, while they are binding to the subdomain IIA of HSA close to the Sudlow’s site I, and interacting with Trp214.

The Bio-Safety Concerns of Three Domestic Temporary Hair Dye Molecules: Fuchsin Basic, Victoria Blue B and Basic Red 2

Hair-coloring products include permanent, semi-permanent and temporary dyes that vary by chemical formulation and are distinguished mainly by how long they last. Domestic temporary hair dyes, such as fuchsin basic, basic red 2 and Victoria blue B, are especially popular because of their cheapness and facile applications. Despite numerous studies on the relationship between permanent hair dyes and disease, there are few studies addressing whether these domestic temporary hair dyes are associated with an increased cancer risk. Herein, to ascertain the bio-safety of these temporary hair dyes, we comparatively studied their percutaneous absorption, hemolytic effect and cytotoxic effects in this paper. Furthermore, to better understand the risk of these dyes after penetrating the skin, experimental and theoretical studies were carried out examining the interactions between the dyes and serum albumins as well as calf thymus (CT)-DNA. The results showed that these domestic temporary hair dyes are cytotoxic with regard to human red blood cells and NIH/3T3 cell lines, due to intense interactions with bovine serum albumin (BSA)/DNA. We conclude that the temporary hair dyes may have risk to human health, and those who use them should be aware of their potential toxic effects.

Surface-enhanced Raman scattering investigation of bovine serum albumin by Au nanoparticles with different sizes

BACKGROUND

Surface-enhanced Raman scattering (SERS) has become a useful spectroscopic tool for studying biomolecule structures. The main types of plasmonic substrates used in biological systems are Au nanoparticles (AuNPs), whose surface plasmon resonance depends on the nanoparticle size, morphology, particle interspace, and so on.

METHODS

In this study, AuNP colloids with different sizes were synthesized and used as the sensors to probe SERS signals of different biomarkers and biomolecules.

RESULTS

The results showed that an AuNP colloid of ~50 nm had excellent SERS effects in probing various molecules, and could be preserved for about 3 months with excellent repeatability and reproducibility (RSD <5%) in terms of the probed signal intensity (rhodamine 6G and crystal violet). Meanwhile, the fabricated AuNPs were applied to study the SERS signals and structural information of bovine serum albumin (BSA) in aqueous solution. It was found that SERS could rapidly provide the structural information and vibration characteristics of BSA.

CONCLUSION

It was concluded that biocompatible AuNP colloid may be a promising biosensor in the rapid and label-free detection of biological systems.

Characterization of the complex between native and reduced bovine serum albumin with aquacobalamin and evidence of dual tetrapyrrole binding

Serum albumin binds to a variety of endogenous ligands and drugs. Human serum albumin (HSA) binds to heme via hydrophobic interactions and axial coordination of the iron center by protein residue Tyr161. Human serum albumin binds to another tetrapyrrole, cobalamin (Cbl), but the structural and functional properties of this complex are poorly understood. Herein, we investigate the reaction between aquacobalamin (H₂OCbl) and bovine serum albumin (BSA, the bovine counterpart of HSA) using Ultraviolet-Visible and fluorescent spectroscopy, and electron paramagnetic resonance. The reaction between H₂OCbl and BSA led to the formation of a BSA-Cbl(III) complex consistent with N-axial ligation (amino). Prior to the formation of this complex, the reactants participate in an additional binding event that has been examined by fluorescence spectroscopy. Binding of BSA to Cbl(III) reduced complex formation between the bound cobalamin and free cyanide to form cyanocobalamin (CNCbl), suggesting that the β-axial position of the cobalamin may be occupied by an amino acid residue from the protein. Reaction of BSA containing reduced disulfide bonds with H₂OCbl produces cob(II)alamin and disulfide with intermediate formation of thiolate Cbl(III)-BSA complex and its decomposition. Finally, in vitro studies showed that cobalamin binds to BSA only in the presence of an excess of protein, which is in contrast to heme binding to BSA that involves a 1:1 stoichiometry. In vitro formation of BSA-Cbl(III) complex does not preclude subsequent heme binding, which occurs without displacement of H₂OCbl bound to BSA. These data suggest that the two tetrapyrroles interact with BSA in different binding pockets.

Daunomycin-loaded superparamagnetic iron oxide nanoparticles: Preparation, magnetic targeting, cell cytotoxicity, and protein delivery research

The clinical use of daunomycin is restricted by dose-dependent toxicity and low specificity against cancer cells. In the present study, modified superparamagnetic iron oxide nanoparticles were employed to load daunomycin and the drug-loaded nanospheres exhibited satisfactory size and smart pH-responsive release. The cellular uptake efficiency, targeted cell accumulation, and cell cytotoxicity experimental results proved that the superparamagnetic iron oxide nanoparticle-loading process brings high drug targeting without decreasing the cytotoxicity of daunomycin. Moreover, a new concern for the evaluation of nanophase drug delivery's effects was considered, with monitoring the interactions between human serum albumin and the drug-loaded nanospheres. Results from the multispectroscopic techniques and molecular modeling calculation elucidate that the drug delivery has detectable deleterious effects on the frame conformation of protein, which may affect its physiological function.

Cationic porphyrin@SPION nanospheres as multifunctional anticancer therapeutics: magnetic targeting, photodynamic potential and bio-safety research

Porphyrin@SPION nanospheres are described as pH-controllable, multifunctional photosensitizations with delivery bio-safety.

Porphyrins functionalized by quaternary pyridinium units

In this review, free-base and metalloporphyrins, functionalized on meso-positions by quaternary pyridinium units, also referred to as cationic porphyrins, are presented. The article consists of five parts. In the first part free-base porphyrins are described, especially taking account on generation of singlet oxygen; next parts concern metalloporphyrins. The second and third parts deal with zinc and manganese porphyrins, respectively; in the fourth part copper, palladium, and platinum porphyrins are presented. In the fifth part, describing porphyrins with various metal ions an attention is paid to porphyrin metal-organic frameworks (MOFs) and metal-organic materials (MOMs) in which metalloporphyrins are immobilized; syntheses and characterization of obtained products are shown.

Investigation and comparison of bovine hemoglobin binding to Al₁₃ and Al(III): evidences from spectroscopic studies

The UV-vis, steady state/time resolved fluorescence spectroscopy and circular dichroism spectroscopy are employed to investigate the interaction mechanisms of Al(13)-Hb and Al(III)-Hb, respectively. The UV-vis studies represent that Al(13) and Al(III) could directly disturb the structure of Hb and induce the heme group exposed to the aqueous medium. Steady state/time resolved and synchronous fluorescence spectroscopy reveal that Al(13) and Al(III) can change the polarity around the fluorophore molecule of Hb. Al(13) makes the protein unfolding and Al(III) induces the protein buried inside the structure. The interaction processes are static quenching mechanisms and the main forces are electrostatic interactions. Moreover, circular dichroism spectra display Al(13) makes greater effect than Al(III), which is reflected on the degrees of α-helix of Hb. The comparison results suggest that Al(13) displays stronger toxicity.