Development of Copper Nanoclusters-Based Turn-Off Nanosensor for Fluorescence Detection of Two Pyrethroid Pesticides (Cypermethrin and Lambda-Cyhalothrin).

Fluorescent copper nanoclusters (Cu NCs) were synthesized by using Withania somnifera (W. somnifera) plant extract as a biotemplate. Aqueous dispersion of W. somnifera-Cu NCs displays intense emission peak at 458 nm upon excitation at 350 nm. This fluorescence emission was utilized for the detection of two pyrethroid pesticides (cypermethrin and lambda-cyhalothrin) via "turn-off" mechanism. Upon the addition of two pyrethiod pesticides independently, the fluorescence emission of W. somnifera-Cu NCs was gradually decreased with increasing concentrations of both pesticides. It was noticed that the decrease in emission intensity at 458 nm was linearly dependent on the logarithm of both pesticides concentrations in the ranges of 0.01-100 µM and of 0.05-100 µM for cypermethrin and lambda-cyhalothrin, respectively. Consequently, the limits of detection were found to be 27.06 and 23.28 nM for cypermethrin and lambda-cyhalothrin, respectively. The as-fabricated W. somnifera-Cu NCs acted as a facile sensor for the analyses of cypermethrin and lambda-cyhalothrin in vegetables (tomato and bottle gourd), which demonstrates that it could be used as portable sensing platform for assaying of two pyrethroid pesticides in food samples.

Elucidation of the interaction of apocarotenoids with calf thymus DNA by biophysical techniques and in vitro study in MCF-7 cells to explore their potential in cancer therapy.

Objectives: DNA is one of the targets of cancer-therapeutic small molecules. Cisplatin, a DNA intercalator, is one of the first-line drugs in the cancer chemo regimen which comes with health-compromising side effects during chemotherapy. The synergistic effect of natural molecules with cisplatin can help to potentiate its anti-cancer efficacy and decrease its negative effect on health. Here, we report the interaction of cisplatin with calf thymus-DNA (ct-DNA) in combination with natural molecules like apocarotenoids which are reported for their therapeutic properties. Materials and Methods: The combinatorial effect of apocarotenoids on ct-DNA was explored through various biophysical techniques such as UV-Visible spectroscopy, circular dichroism studies, DNA melt curve analysis, viscosity measurements, and an in vitro study in MCF-7 cells by cell cycle analysis. Results: UV-Visible spectroscopy studies suggest apocarotenoids and their combination shows a non-intercalative mode of binding. Circular dichroism analysis showed no major changes in DNA form during the interaction of DNA with apocarotenoids and their respective combinations with cisplatin, which is suggestive of the groove-binding mode of apocarotenoids. DNA melt curve analysis showed a decrease in the intensity of the fluorescence for apocarotenoids with cisplatin which indicates the possibility of DNA interaction through groove binding. Viscosity studies suggested a groove binding mode of interaction of ct-DNA with apocarotenoids and their combination as there was minimal change in the viscosity measurements. The in vitro analysis exhibits that the apocarotenoids and their combination have a considerable effect on DNA synthesis. Conclusion: This study provides a better perspective on the possible mode of interaction between ct-DNA and natural molecules along with cisplatin.

Biosynthesis of silver nanoparticles using Lawsonia inermis and their biomedical application.

Developing biosynthesis of silver nanoparticles (Ag-NPs) using plant extract is an environmentally friendly method to reduce the use of harmful chemical substances. The green synthesis of Ag-NPs by Lawsonia inermis extract and its cellular toxicity and the antimicrobial effect was studied. The physical and chemical properties of synthesised Ag-NPs were investigated using UV-visible spectroscopy, infrared spectroscopy, X-ray diffraction (XRD), scanning, and transmission electron microscopy. The average size of Ag-NPs was 40 nm. The XRD result shows peaks at 2θ = 38.07°, 44.26°, 64.43°, and 77.35° are related to the FCC structure of Ag-NPs. Cytotoxicity of synthesised nanoparticles was evaluated by MTT toxicity test on breast cancer MCF7 cell line. Observations showed that the effect of cytotoxicity of nanoparticles on the studied cell line depended on concentration and time. The obtained IC50 was considered for cells at a dose of 250 µg/ml. Growth and survival rates decreased exponentially with the dose. Antimicrobial properties of Ag-NPs synthesised with extract were investigated against Escherichia coli, Salmonella typhimurium, Bacillus cereus, and Staphylococcus aureus to calculate the minimum inhibitory concentration and the minimum bactericidal concentration of (MBC). The results showed that the synthesised Ag-NPs and the plant extract have antimicrobial properties. The lowest concentration of Ag-NPs that can inhibit the growth of bacterial strains was 25 µg/ml.

Formulation and evaluation of a smart drug delivery system of 5-fluorouracil for pH-sensitive chemotherapy.

The conventional chemotherapeutic drugs have many side effects due to their non-selective tissue distribution, reduced drug concentration of the drug at the tumor site, and the drug resistance. To overcome these problems the chemotherapeutic agent should selectively accumulate the tumor site and stays there for a prolonged period of time releasing the payloads in a controlled manner. This can be achieved by the administration of a smart drug delivery system (SDDS) loaded with the active drug molecules. In this work, 5-fluorouracil (5-FU) is loaded into amine functionalised hollow mesoporous silica nanoparticles (HMSN-NH2) and then coated with a biocompatible polydopamine (PDA) to formulate SSDS for 5-FU for pH-sensitive drug release. The physiochemical properties were characterised; the structural morphology was observed by using optical microscope, scanning electron microscope and transmission electron microscope, chemical interaction between the drug and excipients were characterised from Fourier transform infrared spectroscopy, the entrapment efficiency of loaded drug and the pH-dependent drug release rate were evaluated using UV-visible spectroscopy. It was observed that, the drug is compatible with excipients by retaining all the characteristics peaks of 5-FU with negligible changes in the position in all physical mixtures. The PDA coated 5-FU loaded HMSN-NH2 also exhibits a nearly spherical and non-aggregated morphology. The release rate was showed to increase with increase in concentration of structure-directing agent (Triton X 100) in the rate of a maximum release at the end of 72 h in pH 4. The prepared novel PDA coated 5-FU HMSN-NH2 was found to be capable of delivering the anti-cancer drug 5-FU specifically at the tumor site in a pH-dependent stimuli-responsive manner. It also showed a controlled release for a period of 72 h. The enhanced cytotoxicity against HeLa cell line were found for the formulated SSD form.

BSA-drug-ZnO-PEI conjugates interaction with glycans of gp60 endothelial cell receptor protein for targeted drug delivery: a comprehensive spectroscopic study.

The zinc oxide (ZnO) nanoparticles (NPs) have several biomedical applications such as drug delivery, bio-imaging, and biomedical research. ZnO NPs were remedied with polyethyleneimine (PEI) and modified with bovine serum albumin (BSA). Two anticancer drugs - Cisplatin (CIS) and Gemcitabine (GEM) were used in conjugation with BSA. BSA-ZnO-PEI (conjugate 1), BSA-CIS-ZnO-PEI (conjugate 2), and BSA-GEM-ZnO-PEI (conjugate 3) can be used for targeted drug delivery via glycans - N-acetylneuraminic acid (NANA), L-fucose (FUC), N-acetyl glucosamine (NAG), D-mannose (MAN), and D-galactose (GAL), of albumin binding membrane receptor protein (gp60). Considerable interaction and the strong binding of conjugate 2 and conjugate 3 with NANA were observed by UV-visible absorption and fluorescence spectra. The electrostatic stability of conjugate 2 and conjugate 3 with NANA was considerably increased in comparison to conjugate 1 as evident with zeta potential values. The fluorescence quenching data (Ksv and kq) and binding parameters (K and n) of BSA-CIS, BSA-GEM, conjugate 2, and conjugate 3 with NANA and FUC attributes to the strong binding. Amide I and amide III bands of the Raman signal suggested insignificant loss in alpha-helical and beta-sheet content of conjugate 2 and conjugate 3 with NANA and FUC. Therefore, the present study is going to assist in the comprehensive development of conjugates for targeted drug delivery based on the differential glycation pattern of gp60 protein.Communicated by Ramaswamy H. Sarma.

Biophysical Characterization of Iron-Sulfur Proteins.

Iron-sulfur proteins are primordial catalysts and biological electron carriers that today drive major metabolic pathways across all forms of life. They can access a diversity of oxidation states and can mediate electron transfer over an extended range of reduction potentials spanning more than 1 V. Depending on the protein micro-environment and geometry of ligand, co-ordination the iron-sulfur clusters can occur in different forms [2Fe-2S], [3Fe-4S], HiPIP [4Fe-4S], and [4Fe-4S]. There are several spectroscopic methods available to characterize the composition and electronic configuration of the iron-sulfur clusters, such as optical methods and electron paramagnetic resonance. This paper presents the protocols used to characterize the metal center of Coiled-Coil Iron-Sulfur (CCIS), an artificial metalloprotein containing one [4Fe-4S] cluster. It is expected that these protocols will be of general utility for other iron-sulfur proteins.

On determining soot maturity: A review of the role of microscopy- and spectroscopy-based techniques.

Incomplete combustion is the main source of airborne soot, which has negative impacts on public health and the environment. Understanding the morphological and chemical evolution of soot is important for assessing and mitigating the impact of soot emissions. Morphological and chemical structures of soot are commonly studied using microscopy or spectroscopy, and the best technique depends on the parameter of interest and the stage of soot formation considered (i.e., maturity). For the earliest stages of soot formation, particles exhibit simple morphology yet complex and reactive chemical composition, which is best studied by spectroscopic techniques sensitive to the large number of soot precursor species. The only microscope that can offer some morphological information at this stage is the scanning probe microscopy, which can image single polycyclic aromatic hydrocarbons, the precursors of soot. A broader range of types of spectrometers and microscopes can be used by increasing the soot maturity. Mature soot is primarily carbon, and exhibits complex fractal-like morphology best studied with electron microscopy and techniques sensitive to thin oxide or organic coatings. Each characterization technique can target different morphological and chemical properties of soot, from the early to the late stage of its formation. Thus, a guideline for the selection of the appropriate technique can facilitates studies on environmental samples involving the presence of soot.

Fluorometric aptasensor for cadmium(II) by using an aptamer-imprinted polymer as the recognition element.

A fluorometric assay is described for the determination of Cd(II) in environmental and agricultural samples. It is making use of a molecularly imprinted polymer (MIP) and aptamer as dual recognition units, while carbon quantum dots (co-doped with sulphur and nitrogen) and gold nanoparticles (SN-CQD/Au) act as the fluorophores. The aptamer-modified MIP was placed on an SN-CQD/Au-modified indium tin oxide glass electrode. Cd(II) was detected with high selectivity by the recognition sites of the aptamer in the MIP. Fluorescence, with excitation/emission peaks at 370/430 nm, is quenched by Cd(II). Response is linear in the 20 pM to 12 nM concentration range. The detection limit is 1.2 pM. The sensor is selective for Cd(II), and recoveries from spiked waters, soils and vegetables real-world samples range between 82.1 and 113.9%. Graphical abstractA fluorescence sensor composed of a molecularly imprinted polymer and an aptamer as a dual identification system for Cd2+ coupled with and carbon quantum dots (co-doped with sulphur and nitrogen) and gold nanoparticles (SN-CQDs/Au) as fluorescent element that can detect Cd2+ with high selectivity by a dual-recognition mechanism.

Binding of platinum derivative, oxaliplatin to deoxyribonucleic acid: structural insight into antitumor action.

Platinum-derived chemodrugs constitute an active class in cancer therapeutics. Besides being potent against various solid tumors, oxaliplatin has been recognized as the first platinum compound to be approved for the treatment of colorectal cancer. Structurally, oxaliplatin consists of a platinum metal complexed to oxalate and diaminocyclohexane (DACH) and exert its anticancer action by inhibiting DNA replication and transcription. The present study highlights the binding properties of oxaliplatin with calf thymus DNA using spectroscopic methods to comprehend its binding mechanism at molecular level to overcome associated cellular resistance and side effects. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopic outcomes confirm that oxaliplatin is a covalent binding agent and also provide sequence specificity in DNA molecule. Infrared spectral results further indicate that oxaliplatin alkylates purine nitrogenous bases majorly guanine residues (G) in the major groove via formation of either interstrand or intrastrand guanine-guanine d(GpG) and guanine-adenine d(GpA) (N7 position) crosslinks accompanied with a slight external binding to sugar-phosphate backbone. Again, circular dichroism (CD) spectroscopic results suggest subtle conformational changes in DNA molecule due to its complexation with oxaliplatin and duplex attains an intermediate conformational state, having characteristics of both B- and C-forms. Further, a moderate binding strength of 4.12 ± 0.2 × 104 M-1 for the interaction has been estimated via ultraviolet-visible spectroscopy. The inferences obtained from these investigations are encouraging and can form the basis for further exploration in the field of rational drug development based on platinum compounds possessing preferential binding for nucleic acid with improved competence. Communicated by Ramaswamy H. Sarma.

DEPC modification of the CuA protein from Thermus thermophilus.

The CuA center is the initial electron acceptor in cytochrome c oxidase, and it consists of two copper ions bridged by two cysteines and ligated by two histidines, a methionine, and a carbonyl in the peptide backbone of a nearby glutamine. The two ligating histidines are of particular interest as they may influence the electronic and redox properties of the metal center. To test for the presence of reactive ligating histidines, a portion of cytochrome c oxidase from the bacteria Thermus thermophilus that contains the CuA site (the TtCuA protein) was treated with the chemical modifier diethyl pyrocarbonate (DEPC) and the reaction followed through UV-visible, circular dichroism, and electron paramagnetic resonance spectroscopies at pH 5.0-9.0. A mutant protein (H40A/H117A) with the non-ligating histidines removed was similarly tested. Introduction of an electron-withdrawing DEPC-modification onto the ligating histidine 157 of TtCuA increased the reduction potential by over 70 mV, as assessed by cyclic voltammetry. Results from both proteins indicate that DEPC reacts with one of the two ligating histidines, modification of a ligating histidine raises the reduction potential of the CuA site, and formation of the DEPC adduct is reversible at room temperature. The existence of the reactive ligating histidine suggests that this residue may play a role in modulating the electronic and redox properties of TtCuA through kinetically-controlled proton exchange with the solvent. Lack of reactivity by the metalloproteins Sco and azurin, both of which contain a mononuclear copper center, indicate that reactivity toward DEPC is not a characteristic of all ligating histidines.

In vitro biological activities of silver nanoparticles synthesized from Scedosporium sp. isolated from soil

One of the important fields in nanotechnology is the development of an environment friendly method for the synthesis of nanoparticles. Many approaches show that microorganisms are the most reliable tools for biosynthesis of nanoparticles compared to physical and chemical methods. In our study, fungi have been exploited for extracellular production of metal nanoparticles. It was observed that in Scedosporium, silver ions are reduced to silver nanoparticles, which was confirmed by UV-visible spectrophotometry and AFM. Optimization studies showed that as the concentration of AgNO3 used for synthesis increased, particles' size also increased. Size of the particles at different concentrations of AgNO3 was observed to be 79-107 nm with particles being ellipsoidal to spherical in shape. Silver nanoparticles synthesized from 2.0 mM silver nitrate, showed maximum antimicrobial activity compared to all antibiotics tested including synergistic effects. In vitro cytotoxicity of silver nanoparticles against MCF 7 and PC 3 showed that as the concentration of silver nanoparticles increased, a decrease in the percentage cell viability was observed with IC50 values being 60.09 and 57.43 µg/ml respectively. Therefore, through this study, it could be said that extracellular synthesis of silver nanoparticles from Scedosporium was simple, ecofriendly, proving excellent antimicrobial and anticancer agents.

Investigations of vibrational spectra and bioactivity of novel anticancer drug N-(6-ferrocenyl-2-naphthoyl)-gamma-amino butyric acid ethyl ester.

The bioactivity of compounds is mainly dependent on molecular structure and the present work aims to explore the bonding features responsible for biological activity of novel anticancer drug N-(6-ferrocenyl-2-naphthoyl)-gamma-amino butyric acid ethyl ester (FNGABEE). In the present study, we investigate the molecular structural properties of newly synthesized title compound through experimental and quantum chemical studies. The detailed vibrational analysis has been performed using FT IR and FT Raman spectrum, aided by DFT computed geometry, vibrational spectrum, Eigen vector distribution and PED, at B3LYP/6-311++G(d,p) level. The resonance structure of naphthalene, different from that of benzene, revealed by molecular structure has been investigated using CC and CC stretching modes. The proton transfer in amide has been analyzed to obtain spectral distinction between different carbonyl and CN groups which point to the reactive sites responsible for binding with DNA and bovine serum albumin (BSA). The spectral distinction between eclipsed and staggered form of ferrocene has been analyzed. The molecular docking of FNGABEE with BSA and DNA has been performed to find the strength of binding and the moieties responsible for the interactions. The experimental binding studies of FNGABEE with BSA and DNA has been performed using UV absorption spectroscopy and fluorometric assay, to find the nature and strength of binding.

The heme-regulatory motif of nuclear receptor Rev-erbß is a key mediator of heme and redox signaling in circadian rhythm maintenance and metabolism.

Rev-erbß is a heme-responsive transcription factor that regulates genes involved in circadian rhythm maintenance and metabolism, effectively bridging these critical cellular processes. Heme binding to Rev-erbß indirectly facilitates its interaction with the nuclear receptor co-repressor (NCoR1), resulting in repression of Rev-erbß target genes. Fe3+-heme binds in a 6-coordinate complex with axial His and Cys ligands, the latter provided by a heme-regulatory motif (HRM). Rev-erbß was thought to be a heme sensor based on a weak Kd value for the Rev-erbß·heme complex of 2 µm determined with isothermal titration calorimetry. However, our group demonstrated with UV-visible difference titrations that the Kd value is in the low nanomolar range, and the Fe3+-heme off-rate is on the order of 10-6 s-1 making Rev-erbß ineffective as a sensor of Fe3+-heme. In this study, we dissected the kinetics of heme binding to Rev-erbß and provided a Kd for Fe3+-heme of ∼0.1 nm Loss of the HRM axial thiolate via redox processes, including oxidation to a disulfide with a neighboring cysteine or dissociation upon reduction of Fe3+- to Fe2+-heme, decreased binding affinity by >20-fold. Furthermore, as measured in a co-immunoprecipitation assay, substitution of the His or Cys heme ligands in Rev-erbß was accompanied by a significant loss of NCoR1 binding. These results demonstrate the importance of the Rev-erbß HRM in regulating interactions with heme and NCoR1 and advance our understanding of how signaling through HRMs affects the major cellular processes of circadian rhythm maintenance and metabolism.

Colorimetric detection of biothiols based on aggregation of chitosan-stabilized silver nanoparticles.

We have described a simple and reliable colorimetric method for the sensing of biothiols such as cysteine, homocysteine, and glutathione in biological samples. The selective binding of chitosan capped silver nanoparticles to biothiols induced aggregation of the chitosan-Ag NPs. But the other amino acids that do not have thiol group cannot aggregate the chitosan-Ag NPs. Aggregation of chitosan-Ag NPs has been confirmed with UV-vis absorption spectra, zeta potential and transmission electron microscopy images. Under optimum conditions, good linear relationships existed between the absorption ratios (at A500/A415) and the concentrations of cysteine, homocysteine, and glutathione in the range of 0.1-10.0µM with detection limits of 15.0, 84.6 and 40.0nM, respectively. This probe was successfully applied to detect these biothiols in biological samples (urine and plasma).

Gigantol from Dendrobium chrysotoxum Lindl. binds and inhibits aldose reductase gene to exert its anti-cataract activity: An in vitro mechanistic study.

ETHNOPHARMACOLOGICAL RELEVANCE: Dendrobium. chrysotoxum Lindl is a commonly used species of medicinal Dendrobium which belongs to the family of Orchidaceae, locally known as "Shihu" or "Huangcao". D. chrysotoxum Lindl is widely known for medicinal values in traditional Chinese medicine as it possesses anti-inflammatory, anti-hyperglycemic induction, antitumor and antioxidant properties. STUDY AIM: To characterize the interaction between gigantol extracted from D. chrysotoxum Lindl and the AR gene, and determine gigantol's efficacy against cataractogenesis. MATERIALS AND METHODS: Human lens epithelial cells (HLECs) were induced by glucose as the model group. Reverse transcription polymerase chain reaction (RT-PCR) was used to assess AR gene expression. Then, the mode of interaction of gigantol with the AR gene was evaluated by UV-visible spectroscopy, atomic force microscope (AFM) and surface-enhanced Raman spectroscopy (SERS). The binding constant was determined by UV-visible. RESULTS: Gigantol depressed AR gene expression in HLECs. UV-visible spectra preliminarily indicated that interaction between the AR gene and gigantol may follow the groove mode, with a binding constant of 1.85×103L/mol. Atomic force microscope (AFM) data indicated that gigantol possibly bound to insert AR gene base pairs of the double helix. Surface-enhanced Raman spectroscopy (SERS) studies further supported these observations. CONCLUSION: Gigantol extracted from D. chrysotoxum Lindl not only has inhibitory effects on aldose reductase, but also inhibits AR gene expression. These findings provide a more comprehensive theoretical basis for the use of Dendrobium for the treatment of diabetic cataract.

Artificial nose, NIR and UV-visible spectroscopy for the characterisation of the PDO Chianti Classico olive oil.

An authentication study of the Italian PDO (Protected Designation of Origin) olive oil Chianti Classico, based on artificial nose, near-infrared and UV-visible spectroscopy, with a set of samples representative of the whole Chianti Classico production area and a considerable number of samples from other Italian PDO regions was performed. The signals provided by the three analytical techniques were used both individually and jointly, after fusion of the respective variables, in order to build a model for the Chianti Classico PDO olive oil. Different signal pre-treatments were performed in order to investigate their importance and their effects in enhancing and extracting information from experimental data, correcting backgrounds or removing baseline variations. Stepwise-Linear Discriminant Analysis (STEP-LDA) was used as a feature selection technique and, afterward, Linear Discriminant Analysis (LDA) and the class-modelling technique Quadratic Discriminant Analysis-UNEQual dispersed classes (QDA-UNEQ) were applied to sub-sets of selected variables, in order to obtain efficient models capable of characterising the extra virgin olive oils produced in the Chianti Classico PDO area.

A green chemistry approach for synthesizing biocompatible gold nanoparticles.

Gold nanoparticles (AuNPs) are a fascinating class of nanomaterial that can be used for a wide range of biomedical applications, including bio-imaging, lateral flow assays, environmental detection and purification, data storage, drug delivery, biomarkers, catalysis, chemical sensors, and DNA detection. Biological synthesis of nanoparticles appears to be simple, cost-effective, non-toxic, and easy to use for controlling size, shape, and stability, which is unlike the chemically synthesized nanoparticles. The aim of this study was to synthesize homogeneous AuNPs using pharmaceutically important Ganoderma spp. We developed a simple, non-toxic, and green method for water-soluble AuNP synthesis by treating gold (III) chloride trihydrate (HAuCl4) with a hot aqueous extract of the Ganoderma spp. mycelia. The formation of biologically synthesized AuNPs (bio-AuNPs) was characterized by ultraviolet (UV)-visible absorption spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray (EDX), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Furthermore, the biocompatibility of as-prepared AuNPs was evaluated using a series of assays, such as cell viability, lactate dehydrogenase leakage, and reactive oxygen species generation (ROS) in human breast cancer cells (MDA-MB-231). The color change of the solution from yellow to reddish pink and strong surface plasmon resonance were observed at 520 nm using UV-visible spectroscopy, and that indicated the formation of AuNPs. DLS analysis revealed the size distribution of AuNPs in liquid solution, and the average size of AuNPs was 20 nm. The size and morphology of AuNPs were investigated using TEM. The biocompatibility effect of as-prepared AuNPs was investigated in MDA-MB-231 breast cancer cells by using various concentrations of AuNPs (10 to 100 µM) for 24 h. Our findings suggest that AuNPs are non-cytotoxic and biocompatible. To the best of our knowledge, this is the first report to describe the synthesis of monodispersed, biocompatible, and soluble AuNPs with an average size of 20 nm using Ganoderma spp. This study opens up new possibilities of using an inexpensive and non-toxic mushroom extract as a reducing and stabilizing agent for the synthesis of size-controlled, large-scale, biocompatible, and monodispersed AuNPs, which may have future diagnostic and therapeutic applications.

The photoinitiated reaction pathway of full-length cyanobacteriochrome Tlr0924 monitored over 12 orders of magnitude.

The coupling of photochemistry to protein chemical and structural change is crucial to biological light-activated signaling mechanisms. This is typified by cyanobacteriochromes (CBCRs), members of the phytochrome superfamily of photoreceptors that exhibit a high degree of spectral diversity, collectively spanning the entire visible spectrum. CBCRs utilize a basic E/Z isomerization of the bilin chromophore as the primary step in their photocycle, which consists of reversible photoconversion between two photostates. Despite intense interest in these photoreceptors as signal transduction modules a complete description of light-activated chemical and structural changes has not been reported. The CBCR Tlr0924 contains both phycocyanobilin and phycoviolobilin chromophores, and these two species photoisomerize in parallel via spectrally and kinetically equivalent intermediates before the second step of the photoreaction where the reaction pathways diverge, the loss of a thioether linkage to a conserved cysteine residue occurs, and the phycocyanobilin reaction terminates in a red-absorbing state, whereas the phycoviolobilin reaction proceeds more rapidly to a final green-absorbing state. Here time-resolved visible transient absorption spectroscopy (femtosecond to second) has been used, in conjunction with time-resolved IR spectroscopy (femtosecond to nanosecond) and cryotrapping techniques, to follow the entire photoconversion of the blue-absorbing states to the green- and red-absorbing states of the full-length form of Tlr0924 CBCR. Our analysis shows that Tlr0924 undergoes an unprecedented long photoreaction that spans from picoseconds to seconds. We show that the thermally driven, long timescale changes are less complex than those reported for the red/far-red photocycles of the related phytochrome photoreceptors.

Gold nanoparticles decorated with oligo(ethylene glycol) thiols: surface charges and interactions with proteins in solution.

We have studied oligo(ethylene glycol) (OEG) thiol self-assembled monolayer (SAM) coated gold nanoparticles (AuOEG) and their interactions with proteins in solutions using electrophoretic and dynamic light scattering (ELS and DLS). The results are compared with poly(ethylene glycol) (PEG) thiol coated AuNPs (AuPEG). We show that both AuOEG and AuPEG particles carry a low net negative charge and are very stable (remaining so for more than one year), but long-term aging or dialysis can reduce the stability. If the decorated AuNPs are mixed with bovine serum albumin (BSA), both effective size and zeta-potential of the AuNPs remain unchanged, indicating no adsorption of BSA to the colloid surface. However, when mixed with lysozyme, zeta-potential values increase with protein concentrations and lead to a charge inversion, indicating adsorption of lysozyme to the colloid surface. The colloidal solutions of AuOEG become unstable near zero charge, indicated by a cluster peak in the DLS measurements. The AuPEG solutions show similar charge inversion upon addition of lysozyme, but the solutions are stable under all experimental conditions, presumably because of the strong steric effect of PEG. Washing the protein bound colloids by centrifugation can remove only part of the adsorbed lysozyme molecules indicating that a few proteins adsorb strongly to the colloids. The effective charge inversion and rather strongly bound lysozyme on the colloid surface may suggest that in addition to the charges formed at the SAM-water interface, there are defects on the surface of the colloid, which are accessible to the proteins. The results of this study of surface charge, and stability shed light on the interaction with proteins of SAM coated AuNPs and their applications.

An in vitro evaluation of graphene oxide reduced by Ganoderma spp. in human breast cancer cells (MDA-MB-231).

BACKGROUND: Recently, graphene and graphene-related materials have attracted much attention due their unique properties, such as their physical, chemical, and biocompatibility properties. This study aimed to determine the cytotoxic effects of graphene oxide (GO) that is reduced biologically using Ganoderma spp. mushroom extracts in MDA-MB-231 human breast cancer cells. METHODS: Herein, we describe a facile and green method for the reduction of GO using extracts of Ganoderma spp. as a reducing agent. GO was reduced without any hazardous chemicals in an aqueous solution, and the reduced GO was characterized using a range of analytical procedures. The Ganoderma extract (GE)-reduced GO (GE-rGO) was characterized by ultraviolet-visible absorption spectroscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, dynamic light scattering, scanning electron microscopy, Raman spectroscopy, and atomic force microscopy. Furthermore, the toxicity of GE-rGO was evaluated using a sequence of assays such as cell viability, lactate dehydrogenase leakage, and reactive oxygen species generation in human breast cancer cells (MDA-MB-231). RESULTS: The preliminary characterization of reduction of GO was confirmed by the red-shifting of the absorption peak for GE-rGO to 265 nm from 230 nm. The size of GO and GE-rGO was found to be 1,880 and 3,200 nm, respectively. X-ray diffraction results confirmed that reduction processes of GO and the processes of removing intercalated water molecules and the oxide groups. The surface functionalities and chemical natures of GO and GE-rGO were confirmed using Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. The surface morphologies of the synthesized graphene were analyzed using high-resolution scanning electron microscopy. Raman spectroscopy revealed single- and multilayer properties of GE-rGO. Atomic force microscopy images provided evidence for the formation of graphene. Furthermore, the effect of GO and GE-rGO was examined using a series of assays, such as cell viability, membrane integrity, and reactive oxygen species generation, which are key molecules involved in apoptosis. The results obtained from cell viability and lactate dehydrogenase assay suggest that GO and GE-rGO cause dose-dependent toxicity in the cells. Interestingly, it was found that biologically derived GE-rGO is more toxic to cancer cells than GO. CONCLUSION: We describe a simple, green, nontoxic, and cost-effective approach to producing graphene using mushroom extract as a reducing and stabilizing agent. The proposed method could enable synthesis of graphene with potential biological and biomedical applications such as in cancer and angiogenic disorders. To our knowledge, this is the first report using mushroom extract as a reducing agent for the synthesis of graphene. Mushroom extract can be used as a biocatalyst for the production of graphene.