Fluorescence Emission Spectroscopy Research Articles

Structural and Biological Properties of Heteroligand Copper Complexes with Diethylnicotinamide and Various Fenamates: Preparation, Structure, Spectral Properties and Hirshfeld Surface Analysis

Herein, we discuss the synthesis, structural and spectroscopic characterization, and biological activity of five heteroligand copper(II) complexes with diethylnicotinamide and various fenamates, as follows: flufenamate (fluf), niflumate (nifl), tolfenamate (tolf), clonixinate (clon), mefenamate (mef) and N, N-diethylnicotinamide (dena). The complexes of composition: [Cu(fluf)2(dena)2(H2O)2] (1), [Cu(nifl)2(dena)2] (2), [Cu(tolf)2(dena)2(H2O)2] (3), [Cu(clon)2(dena)2] (4) and [Cu(mef)2(dena)2(H2O)2] (5), were synthesized, structurally (single-crystal X-ray diffraction) and spectroscopically characterized (IR, EA, UV-Vis and EPR). The studied complexes are monomeric, forming a distorted tetragonal bipyramidal stereochemistry around the central copper ion. The crystal structures of all five complexes were determined and refined with an aspheric model using the Hirshfeld atom refinement method. Hirshfeld surface analysis and fingerprint plots were used to investigate the intermolecular interactions in the crystalline state. The redox properties of the complexes were studied and evaluated via cyclic voltammetry. The complexes exhibited good superoxide scavenging activity as determined by an NBT assay along with a copper-based redox-cycling mechanism, resulting in the formation of ROS, which, in turn, predisposed the studied complexes for their anticancer activity. The ability of complexes 1–4 to interact with calf thymus DNA was investigated using absorption titrations, viscosity measurements and an ethidium-bromide-displacement-fluorescence-based method, suggesting mainly the intercalative binding of the complexes to DNA. The affinity of complexes 1–4 for bovine serum albumin was determined via fluorescence emission spectroscopy and was quantitatively characterized with the corresponding binding constants. The cytotoxic properties of complexes 1–4 were studied using the cancer cell lines A549, MCF-7 and U-118MG, as well as healthy MRC-5 cells. Complex 4 exhibited moderate anticancer activity on the MCF-7 cancer cells with IC50 = 57 μM.

Diverse Magnetic Properties of Two New Binuclear Complexes Affected by [FeN6] Octahedral Distortion: Two-Step Spin Crossover versus Antiferromagnetic Interactions

Polymetallic complexes with covalently bridged metal centers that interact magnetically are important in the molecular magnetism field, with binuclear compounds receiving special attention because they represent the simplest type of multinuclear species with covalently bridged metal centers. Herein, we report the synthesis and properties of two new binuclear FeII complexes, namely, {[Fe(abpt-TPE)(NCS)2]2(bpym)}·2MeOH·2MeCN (1) and {[Fe(abpt-TPE)(NCS)2]2(bpym)}·2CH2Cl2 (2) (bpym = 2,2′-bipyrimidine). The crystal structure is analyzed at different temperatures, and its properties are analyzed by variable-temperature magnetic susceptibility and variable-temperature fluorescence emission spectroscopy tests. Variable-temperature magnetic susceptibility measurements of two binuclear compounds show different types of magnetic behavior. Complex 1 exhibits two-step spin transition behavior with an intermediate state near 150 K (Tc1 = 191 K, Tc2 = 111 K); 1 undergoes an [LS–LS] ↔ [LS–HS] ↔ [HS–HS] spin transition during thermal induction. On the other hand, complex 2 exhibits intramolecular antiferromagnetic coupling, with J = −0.47 cm−1. The analysis of correlations between the structural characteristics and different types of magnetic behaviors for two binuclear complexes, revealed that the different magnetic behaviors shown by the two complexes are attributable to different degrees of [FeN6] octahedral distortion caused by different lattice solvents, ligand strain and crystal stacking.

Elucidation of DNA-Eltrombopag Binding: Electrochemical, Spectroscopic and Molecular Docking Techniques.

Eltrombopag is a powerful adjuvant anticancer drug used in treating MS (myelodysplastic syndrome) and AML (acute myeloid leukemia) diseases. In this study, the interaction mechanism between eltrombopag and DNA was studied by voltammetry, spectroscopic techniques, and viscosity measurements. We developed a DNA-based biosensor and nano-biosensor using reduced graphene oxide-modified glassy carbon electrode to detect DNA-eltrombopag binding. The reduction of desoxyguanosine (dGuo) and desoxyadenosine (dAdo) oxidation signals in the presence of the drug demonstrated that a strong interaction could be established between the eltrombopag and dsDNA. The eltrombopag-DNA interaction was further investigated by UV absorption and fluorescence emission spectroscopy to gain more quantitative insight on binding. Viscosity measurements were utilized to characterize the binding mode of the drug. To shed light on the noncovalent interactions and binding mechanism of eltrombopag molecular docking and molecular dynamics (MD), simulations were performed. Through simultaneously carried out experimental and in silico studies, it was established that the eltrombopag binds onto the DNA via intercalation.

DNA groove binder and significant cytotoxic activity on human colon cancer cells: Potential of a dimeric zinc (II) phthalocyanine derivative

The interaction of a multi-component system consisting of benzene-1,4-diyldimethanimine-bridged dimeric zinc-phthalocyanine groups (4OMPCZ) with calf thymus DNA (ct-DNA) was investigated using UV–Vis absorption, fluorescence emission spectroscopy methods, and viscosity measurements. The binding constant, Kb, which is an important parameter to gain information about the binding mode, was found as 9.7 × 107 M−1 from the UV–Vis absorption studies. Another important spectrophotometric tool is competitive displacement assays with Ethidium bromide and Hoechst 33342. Through this experiment, a higher KSV value was obtained with Hoechst for the phthalocyanine derivative, 4OMPCZ, and the ct-DNA complex than with ethidium bromide. Additionally, molecular docking studies were conducted to calculate the theoretical binding constant and visualize the interactions of 4OMPCZ with a model DNA. According to docking results, although the interactions are mainly located in the major groove of the DNA helix, due to the wrapping, these interactions can also be extended to the minor groove of the DNA. Spectrophotometric, molecular docking, and viscosity studies revealed that the interaction of 4OMPCZ with DNA is likely to be via the major and minor grooves. The in vitro cytotoxic activity of 4OMPCZ was evaluated by MTT assay on human colon cancer cells (HT29) after 72 h of treatment. 4OMPCZ indicated significant cytotoxic activity when stimulated with UV light compared to the standard chemotherapy drugs, fluorouracil (5-FU), and cisplatin on HT29 colon cancer cells. The IC50 value of 4OMPCZ displayed considerably lower concentrations compared to the standard drugs, 5-FU, and cisplatin.

The synergistic effect of electron lone pairs and aromaticity on the binding affinity towards metal surfaces

Non-covalent binding interactions of organic molecules through their electron lone pairs and aromatic functional groups towards metal surface are understood. Four isoxazole derivatives containing different sequential aromatic groups and lone pair of electrons are designed and synthesized along with cobalt nanoparticles as a representative of metal surface and titrated against each other. Multiple characterization techniques including UV-Vis absorption spectroscopy, fluorescence emission spectroscopy, hydrodynamic size, and zeta potential are used to study binding and results are compared to each other. We are able to differentiate and understand binding interactions of these functionalities towards metal surface, where the binding mechanism is different based on variations in these molecules. The binding ability of lone pair of electrons (1.48 × 108) is slightly stronger than the π-bond electronic cloud of aromatic benzene group (1.46 × 108), however presence of both functionalities tends to enhance the binding more than twice (3.24 × 108), a synergistic effect that is very strongly observed. These results are also verified by DFT calculations. This work will certainly be helpful to design molecules for their specific interaction required for various applications.

Erbium(III) coordination compounds with substituted salicylaldehydes: Characterization and biological profile

Five erbium(III) complexes with salicylaldehyde (saloH for 1), and mono– (5–X–saloH; X = NO2 and Me for 2 and 3, respectively) or di–substituted salicylaldehydes (3,5–diX–saloH; X = Cl and Br for 4 and 5, respectively) were synthesized and characterized by physicochemical and spectroscopic techniques and single–crystal X–ray crystallography. All five complexes have the general formula [Er(deprotonated salicylaldehyde)3(MeOH)(H2O)]. The structure of complexes [Er(3,5–diCl–salo)3(MeOH)(H2O)]·1.5MeOH (complex 4) and [Er(3,5–diBr–salo)3(MeOH)(H2O)]·1.75MeOH (complex 5) were verified by single–crystal X–ray crystallography. The evaluation of antioxidant activity of the complexes was focused on their ability to scavenge 1,1–diphenyl–picrylhydrazyl and 2,2′–azinobis–(3–ethylbenzothiazoline–6–sulfonic acid) free radicals and to reduce H2O2. The interaction of the complexes with calf–thymus DNA was investigated by UV–vis spectroscopy, viscosity measurements and via competitive studies with ethidium bromide in order to evaluate the possible DNA–binding mode and to determine the corresponding DNA–binding constants. The affinity of the complexes for bovine and human serum albumins was explored by fluorescence emission spectroscopy and the corresponding binding constants were determined.

Synthesis and Photophysical Properties of Anthracene Bisimide–butadiynylene Linear Dimer and Trimer

Linear dimer and trimer of anthracene bisimide (ABI) units linked by butadiynylene spacers were synthesized through Hay coupling of 9,10-diethynyl ABI derivatives. Chain length effects on π-conjugation were experimentally and computationally investigated using DFT. UV-vis spectroscopy revealed that increasing the number of ABI units caused a bathochromic shift of the absorption maxima. Fluorescence emission spectroscopy revealed that these ABI-based oligomers had higher fluorescence quantum yields than those of their anthrylene counterparts, which might be attributed to strong fluorescence properties of the ABI units.

Highly Efficient Triplet–Triplet Annihilation Upconversion with a Thermally Activated Delayed Fluorescence Molecule as Triplet Photosensitizer

Thermally activated delayed fluorescence (TADF) molecules have great potential for practical applications as triplet photosensitizers, owing to their long triplet lifetimes, almost negligible energy loss in intersystem crossing, and excellent light-harvesting ability. Recently, several triplet–triplet annihilation (TTA) upconversion systems using the TADF photosensitizer have been reported. To provide comprehensive dynamic information for designing an optimized system in the future, more experiments with the new TADF photosensitizers are necessary. Herein, we conducted a new TTA upconversion system with a recently developed TADF molecule, DMACPDO, as the triplet photosensitizer and 9,10-diphenylanthracene (DPA) as the annihilator. The overall upconversion yield was determined to be relatively high, e.g., 22.3% in toluene, 21.9% in benzene, and 8.1% in chlorobenzene. By examining elementary photophysical and photochemical processes with time-resolved transient absorption and fluorescence emission spectroscopy, we revealed the influence of solvent polarity and viscosity on each step. Our conclusion highlights the elusive solvent effect in TTA upconversion application of the TADF photosensitizer.

Preparation of a g-C3N4/Ag3PO4 composite Z-type photocatalyst and photocatalytic degradation of Ofloxacin: Degradation performance, reaction mechanism, degradation pathway and toxicity evaluation

In this study, a g-C3N4/Ag3PO4 composite Z-heterojunction photocatalyst was prepared with a simple in situ deposition method, and was first applied to the degradation of Ofloxacin (OFX). When the theoretical g-C3N4 to Ag3PO4 mass ratio was 1:10 (denoted as AC-10), the OFX degradation was optimal, and the degradation efficiency reached 71.9 % within 10 min. Steady state fluorescence emission spectroscopy (PL), electrochemical impedance spectroscopy (EIS), transient photocurrent (I-t) and N2 adsorption-desorption (BET) studies showed that AC-10 had the best charge separation efficiency and highest specific surface area. Additionally, the effects of AC-10 dosage, OFX concentration, pH value, anions, humic acid and water source on the degradation process were also studied. A cycling experiment showed that AC-10 exhibited good stability. Three-dimensional excitation-emission matrix spectroscopy (3D EEMs), LC-MS data and ECOSAR models were used to explore the process for degradation of OFX and predict the biotoxicities of byproducts, and these results indicated that the catalyst was environmentally friendly. In addition, electron spin resonance (ESR) experiments and capture of the active species showed that photogenerated holes (h+) played a major role in the reaction. Finally, the optical properties and the energy band structure of the catalyst were analyzed by UVvis diffuse reflectance spectroscopy (DRS) and Mott-Schottky (M-S) methods, and a Z-type heterojunction charge transfer mechanism was proposed.

Identification of binding sites for Tartary buckwheat protein-phenols covalent complex and alterations in protein structure and antioxidant properties

To investigate the effects of structure, multiple binding sites and antioxidant property of Tartary buckwheat protein-phenols covalent complex, protein was combined with different concentrations of phenolic extract. Four kinds of phenols were identified by UPLC-Q/TOF-MS, which were rutin, quercetin, kaempferol and myricetin. UV–vis absorption spectroscopy and X-ray diffraction showed that the phenols can successfully bind to BPI. Fourier-transform infrared, circular dichroism and fluorescence emission spectroscopy showed that the binding of phenol can change the secondary/tertiary structure of protein. The particle distribution indicated that the binding of phenols could reduce the particle size (from 304.70 to 205.55 nm), but cross-linking occurred (435.35 nm) when the bound phenol content was too high. Proteomics showed that only rutin, quercetin and myricetin can covalently bind to BPI. Meanwhile, 4 peptides covalently bound to phenols were identified. The DPPH· scavenging capacity of complexes were from 8.38 to 33.76 %, and the ABTS·+ binding activity of complexes were from 19.35 to 63.99 %. The antioxidant activity of the complex was significantly higher than that of the pure protein. These results indicated that protein-phenol covalent complexes had great potential as functional components in the food field.

Solvent induced selective response to metal ions of three HNBO-based chemosensors

The 2-(2-hydroxy-3-naphthyl)-4-methylbenzoxazole (HNBO) fluorophore has been linked to three different amine scaffolds obtaining three fluorescent chemosensors (L1–L3). The ESIPT (excited-state intramolecular proton transfer) behavior was investigated in ACN and DMSO by UV–Vis spectrophotometric and spectrofluorimetric measurements, revealing the occurrence of an ESIPT process only in ACN, in the case of L1 and L2, and in both aprotic solvents, besides protic solvents (water and EtOH-water mixture), in the case of L3. The emission of L1–L3 is related to the deprotonated form of the ligand. The binding properties of L1–L3 towards Alkali, Alkaline-earth and some transition metal ions were investigated in different solvents by UV–Vis absorption, fluorescence emission and NMR spectroscopies. The fluorescence switches-ON in the presence of selected metal ions, always showing a mechanism different from ESIPT. All L1–L3 show a selectivity for Mg2+ in DMSO, while in ACN the selectivity of L1 and L2 shifts towards Zn2+ and Cd2+. L3 is also able to respond to Mg2+ in other aprotic solvents (THF and dioxane). L1 and L3 also showed the ability to signal the presence of metal ions on a paper support (L1: Zn2+; L3: Zn2+, Cd2+ and Mg2+). Therefore, L3 revealed able to signal the presence of Mg2+ both in solution, in different solvents, as well as on a paper support.

Cancer cells inhibition by cationic carbon dots targeting the cellular nucleus

Nucleus targeting is tremendously important in cancer therapy. Cationic carbon dots (CCDs) are potential nanoparticles which might enter cells and penetrate nuclear membranes. Although some CCDs have been investigated in nucleus targeting and applied in nuclear imaging, the CCDs derived from drugs, that are able to target the nucleus, bind with DNA and inhibit the growth of cancer cells have not been reported. In this project, 1, 2, 4, 5-benzenetetramine (Y15, a focal adhesion kinase inhibitor) derived cationic carbon dots (Y15-CDs) were prepared via a hydrothermal approach utilizing Y15, folic acid and 1,2-ethylenediamine as precursors. Based on the structural, optical, and morphologic characterizations, Y15-CDs possess rich amine groups and nitrogen in structure, an excitation-dependent photoluminescence emission, and a small particle size of 2 to 4 nm. The DNA binding experiments conducted through agarose gel electrophoresis, UV–vis absorption, fluorescence emission, and circular dichroism spectroscopies, prove that Y15-CDs might bind with DNA via electrostatic interactions and partially intercalative binding modes. In addition, the cell imaging and cytotoxicity studies in human foreskin fibroblasts (HFF), prostate cancer (PC3) and osteosarcoma cells (U2OS) indicate the nucleus targeting and anticancer abilities of Y15-CDs. Most interestingly, Y15-CDs exhibit a higher cytotoxicity to cancer cells (PC3 and U2OS) than to normal cells (HFF), inferring that Y15-CDs might be potentially applied in cancer therapy.

Enzyme PTP-1B Inhibition Studies by Vanadium Metal Complexes: a Kinetic Approach.

The medical field now needs more novel drugs to treat obesity and type-2 diabetes mellitus (T2D) than ever before. Obesity and T2D are both characterized by resistance to the hormones leptin and insulin. PTP-1B is a promising target for drug growth, as strong genetic, pharmacological, and biochemical evidence points to the possibility of treating diabetes and obesity by blocking the PTP-1B enzyme. Studies have also found that PTP-1B is overexpressed in patients with diabetes and obesity, suggesting that inhibiting PTP-1B may be a useful technique in their care. There are no clinically used PTP-1B inhibitors, despite the fact that numerous naturally occurring PTP-1B inhibitors have demonstrated great therapeutic promise. This is most likely due to their low activity or lack of selectivity. It is still important to look for more effective and focused PTP-1B inhibitors. A few organovanadium metal complexes were synthesized and characterized, and binding studies on vanadium complexes with PTP-B were also performed using fluorescence emission spectroscopy. Additionally, we theoretically (molecular modeling) and experimentally (enzyme kinetics) examined the PTP-1B inhibitory effects of these vanadium metal complexes and found that they have excellent PTP-1B inhibitory properties.

Advances in Physicochemical and Biochemical Characterization of Archaeosomes from Polar Lipids of Aeropyrum pernix K1 and Stability in Biological Systems.

Archaeosomes are vesicles made from archaeal lipids. They are characterized by remarkable thermostability, resistance to enzymatic degradation, long-term stability, and immunomodulatory properties. In this review the current status of physicochemical properties of archaeal lipids and their stability in biological systems is presented, focusing on total polar lipids from Aeropyrum pernix K1. The isolated total polar lipids from Aeropyrum pernix K1 consist exclusively of glycerol ether lipids with isoprenoid groups attached to glycerol via ether linkages. More specifically, the two major polar lipids extracted from the membranes are C25,25-achaetidyl(glucosyl)inositol and C25,25-achaetidylinositol. An overview of the results of the effects of temperature and pH on the stability, structural organization, fluidity, and permeability of archaeosomes composed of pure C25,25 was examined by a combination of techniques, including fluorescence emission spectroscopy, electron paramagnetic resonance, differential scanning calorimetry, and confocal microscopy. We also compared the physicochemical properties of pure vesicles composed of either archaeal lipids or conventional lipids (e.g., 1,2-dipalmitoyl-sn-glycero-3-phosphocholine) with mixed vesicles composed of both lipid types. Archaeal lipids are discussed in terms of their potential use as a targeted drug delivery system based on the results of in vivo and cytotoxicity studies.

Understanding non-covalent interactions of graphene oxide toward transition metal surfaces and relation of binding constants with titration end points from dynamic light scattering studies

The understanding of non-covalent binding interactions of graphene oxide toward transition metal surfaces (Fe, Co, Ni, and Cu) was observed by ultraviolet–visible absorption spectroscopy, fluorescence emission spectroscopy, hydrodynamic size, and zeta potential studies through titration experiments. These interactions mainly occur through C=C double bonds of graphene oxide. Iron and cobalt nanoparticles interact strongly as compared to nickel and copper nanoparticles. The obtained Stern–Volmer plots are curved indicating that static and dynamic quenching occur simultaneously in these systems. The curves obtained for size titration graphs indicated the saturation end point for these titrations, which were then compared with binding constants obtained from linear Stern–Volmer plots. Interestingly, with lower binding constants, a higher concentration of nanoparticles was required for titration end points. These two complimentary techniques stood well quantitatively toward each other. Upon titrating the nanoparticles with graphene oxide, the zeta potential always lowered close to the value of graphene oxide, indicating that hybrids are more stable than the nanoparticles.

Improvement of heat-induced nanofibrils formation of soy protein isolate through NaCl and microwave

A novel method involving microwave heating (MH) at 85 °C can be applied to induce the self-assembly of soy protein isolate (SPI) into SPI-nanofibrils at low pH and in the presence of NaCl. The effect of heating type (MH and conventional heating (CH)), heating times (0, 30, 60, and 90 min), and NaCl (0 and 160 mM) on the formation and physicochemical properties of SPI-nanofibrils at pH 2.0 and 85 °C were investigated. The SPI-nanofibrils were characterized through thioflavin T (Th T) fluorescence, intrinsic fluorescence emission spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM), surface charge density, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and Fourier transform infrared spectrometer (FTIR). The sample treated with MH for 30 min in the presence of NaCl had the highest potential to form SPI-nanofibrils as evidenced by Th T. The AFM (998 nm) and TEM (1573 nm) results demonstrated that the longest SPI-nanofibrils were formed in the sample treated with MH for 60 min in the presence of NaCl. MH and NaCl procedures had a significant effect on the level of β-sheet and led to increasing its level (35.3%). The results of SDS-PAGE indicated that progressive polypeptide hydrolysis occurred upon heating, and the polypeptide hydrolysis for the samples treated with MH was much more severe than the samples treated with CH. From the surface charge density results, MH and NaCl led to decreasing electrostatic repulsion. Hence, these phenomena might increase the SPI-nanofibrils level by the electrostatic interaction. Finally, the data suggest that MH and NaCl not only can enhance the potential for SPI-nanofibrils formation but also increase the length of SPI-nanofibrils.

Illuminating milling mechanochemistry by tandem real-time fluorescence emission and Raman spectroscopy monitoring.

In pursuit of accessible and interpretable methods for direct and real-time observation of mechanochemical reactions, we demonstrate a tandem spectroscopic method for monitoring of ball-milling transformations combining fluorescence emission and Raman spectroscopy, accompanied by high-level molecular and periodic density-functional theory (DFT) calculations, including periodic time-dependent (TD-DFT) modelling of solid-state fluorescence spectra. This proof-of-principle report presents this readily accessible dual-spectroscopy technique as capable of observing changes to the supramolecular structure of the model pharmaceutical system indometacin during mechanochemical polymorph transformation and cocrystallisation. The observed time-resolved in situ spectroscopic and kinetic data are supported by ex situ X-ray diffraction and solid-state nuclear magnetic resonance spectroscopy measurements. The application of first principles (ab initio) calculations enabled the elucidation of how changes in crystalline environment, that result from mechanochemical reactions, affect vibrational and electronic excited states of molecules. The herein explored interpretation of both real-time and ex situ spectroscopic data through ab initio calculations provides an entry into developing a detailed mechanistic understanding of mechanochemical milling processes and highlights the challenges of using real-time spectroscopy.

Poly(glycerol monomethacrylate)-encapsulated upconverting nanoparticles prepared by miniemulsion polymerization: morphology, chemical stability, antifouling properties and toxicity evaluation.

In this report, upconverting NaYF4:Yb3+,Er3+ nanoparticles (UCNPs) were synthesized by high-temperature coprecipitation of lanthanide chlorides and encapsulated in poly(glycerol monomethacrylate) (PGMMA). The UCNP surface was first treated with hydrophobic penta(propylene glycol) methacrylate phosphate (SIPO) to improve colloidal stability and enable encapsulation by reversible addition-fragmentation chain transfer miniemulsion polymerization (RAFT) of glycidyl methacrylate (GMA) in water, followed by its hydrolysis. The resulting UCNP-containing PGMMA particles (UCNP@PGMMA), hundreds of nanometers in diameter, were thoroughly characterized by transmission (TEM) and scanning electron microscopy (SEM), dynamic light scattering (DLS), infrared (FTIR) and fluorescence emission spectroscopy, and thermogravimetric analysis (TGA) in terms of particle morphology, size, polydispersity, luminescence, and composition. The morphology, typically raspberry-like, depended on the GMA/UCNP weight ratio. Coating of the UCNPs with hydrophilic PGMMA provided the UCNPs with antifouling properties while enhancing chemical stability and reducing the cytotoxicity of neat UCNPs to a non-toxic level. In addition, it will allow the binding of molecules such as photosensitizers, thus expanding the possibilities for use in various biomedical applications.

New AB3-type porphyrins with piperidine and morpholine motifs; synthesis and photo-physicochemical and biological properties.

In this study, new unsymmetrical meso-tetraaryl AB3-type porphyrins 1 and 2 were successfully synthesized by the reaction of p-bromobenzaldehyde and p-hydroxybenzaldehyde with pyrrole in propionic acid. AB3-type porphyrin building blocks with hydroxyl functionality (1 and 2) were further used to generate both covalently linked metal free and Zn(II) porphyrins 3-6 having piperidine and morpholine heterocyclic units. These novel compounds were characterized by using 1H NMR, 13C NMR, FT-IR and MALDI-TOF spectrophotometry. The photophysical and photochemical properties of compounds 1-6 were investigated by employing UV-vis absorption and fluorescence emission spectroscopy in tetrahydrofuran (THF). From the view of biological properties, the antioxidant capacities of porphyrins were determined by using DPPH radical scavenging activity and 2 was determined as the most potent porphyrin analog with a value of 98.42% at 200 mg L-1. All the targeted compounds displayed significant DNA nuclease activity. In addition, the antimicrobial potential of compounds 1-6 was also investigated by a micro-dilution process and 2 was found to be the most effective candidate against the tested microbial strains. The newly synthesized porphyrins also showed 100% microbial cell viability inhibition against E. coli at all examined concentrations. In terms of biofilm inhibition activity, the best results for the maximum photodynamic antimicrobial biofilm inhibition of S. aureus and P. aeruginosa were obtained by compound 2 with the values of 99.75% and 93.39%, respectively.

Structure and DNA/BSA binding study of zinc(II) complex with 4-ethynyl-2,2’-bipyridine

In the present study, a zinc(II) complex with 4-ethynyl-2,2?-bipyridine (ebpy), [Zn(ebpy)Cl2], was synthesized and characterized by spectroscopic (1H-NMR, IR and UV?Vis) methods and molar conductivity measurement. The crystal structure of the [Zn(ebpy)Cl2] complex was determined by single-crystal X-ray diffraction analysis, confirming the bidentate coordination of the ebpy ligand through its two nitrogen atoms, while the remaining two coordination sites are occupied by two chloride ions. With the aim to investigate the reactivity of the synthesized zinc(II) complex toward biologically important molecules, its binding affinity to calf thymus DNA (ct-DNA) and bovine serum albumin (BSA) was studied by fluorescence emission spectroscopy. From the obtained results, it can be concluded that [Zn(ebpy)Cl2] complex binds to bovine serum albumin reversibly, while the combination of ethidium bromide (EthBr) and Hoechst 33258 (2?-(4-hydroxyphenyl)-5-[5-(4-methylpiperazine- 1-yl)benzimidazo-2-yl]-benzimidazole) competitive binding study suggests that this complex interacts with ct-DNA through the minor groove binding, which is in agreement with molecular docking study.