Protein micelles from lipoxygenase 3

Endophytic Nanotechnology: An Approach to Study Scope and Potential Applications

Nanotechnology has become a very advanced and popular form of technology with huge potentials. Nanotechnology has been very well explored in the fields of electronics, automobiles, construction, medicine, and cosmetics, but the exploration of nanotecnology's use in agriculture is still limited. Due to climate change, each year around 40% of crops face abiotic and biotic stress; with the global demand for food increasing, nanotechnology is seen as the best method to mitigate challenges in disease management in crops by reducing the use of chemical inputs such as herbicides, pesticides, and fungicides. The use of these toxic chemicals is potentially harmful to humans and the environment. Therefore, using NPs as fungicides/ bactericides or as nanofertilizers, due to their small size and high surface area with high reactivity, reduces the problems in plant disease management. There are several methods that have been used to synthesize NPs, such as physical and chemical methods. Specially, we need ecofriendly and nontoxic methods for the synthesis of NPs. Some biological organisms like plants, algae, yeast, bacteria, actinomycetes, and fungi have emerged as superlative candidates for the biological synthesis of NPs (also considered as green synthesis). Among these biological methods, endophytic microorganisms have been widely used to synthesize NPs with low metallic ions, which opens a new possibility on the edge of biological nanotechnology. In this review, we will have discussed the different methods of synthesis of NPs, such as top-down, bottom-up, and green synthesis (specially including endophytic microorganisms) methods, their mechanisms, different forms of NPs, such as magnesium oxide nanoparticles (MgO-NPs), copper nanoparticles (Cu-NPs), chitosan nanoparticles (CS-NPs), β-d-glucan nanoparticles (GNPs), and engineered nanoparticles (quantum dots, metalloids, nonmetals, carbon nanomaterials, dendrimers, and liposomes), and their molecular approaches in various aspects. At the molecular level, nanoparticles, such as mesoporous silica nanoparticles (MSN) and RNA-interference molecules, can also be used as molecular tools to carry genetic material during genetic engineering of plants. In plant disease management, NPs can be used as biosensors to diagnose the disease.

Anderson polyoxometalates with intrinsic oxidase-mimic activity for "turn on" fluorescence sensing of dopamine

Anderson-type polyoxometalate containing Fe³⁺ and Mo⁶⁺, (NH₄)₃[H₆Fe(III)Mo₆O₂₄] (FeMo₆), was found to work as an oxidase-mimicking nanoenzyme for the first time, exhibiting the ability of catalytic oxidation of o-phenylenediamine (OPD), 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTs), and 3,3',5,5'-tetramethylbenzidine (TMB), which features easy synthesis, low cost, simple operation, and low consumption. Attributed to the nature of FeMo₆ and Fenton-like effect, a novel sensor based on two consecutive "turn on" fluorescence was developed for detecting dopamine (DA) by employing the FeMo₆-OPD system, and the linear range was from 1 to 100 μM with the detection limit 0.0227 μM (3σ/s). Moreover, to increase oxidase-mimic activity of FeMo₆, reduced graphene oxide (rGO) loading FeMo₆ composites (FeMo₆@rGO (n), n = 5%, 10%, 15%) was fabricated, and results show that oxidase-like activities of FeMo₆@rGO (n) are dependent on the mass ratio of FeMo₆/rGO, and FeMo₆@rGO (10%) exhibits the highest oxidase-mimic activity and the fastest respond time (4 min) among all reported oxidase mimic of DA to date. Graphical abstract Anderson-type Mo-POMs FeMo₆ was found to work as an oxidase-mimicking nanoenzyme for the first time and was used to detect DA for two consecutive "turn on" fluorescence sensor modes.

Thermoresponsive Micellar Assembly Constructed from a Hexameric Hemoprotein Modified with Poly(N-isopropylacrylamide) toward an Artificial Light-Harvesting System

Artificial protein assemblies inspired by nature have significant potential in development of emergent functional materials. In order to construct an artificial protein assembly, we employed a mutant of a thermostable hemoprotein, hexameric tyrosine-coordinated heme protein (HTHP), as a building block. The HTHP mutant which has cysteine residues introduced on the bottom surface of its columnar structure was reacted with maleimide-tethering thermoresponsive poly(N-isopropylacrylamide), PNIPAAm, to generate the protein assembly upon heating. The site-specific modification of the cysteine residues with PNIPAAm on the protein surface was confirmed by SDS-PAGE and analytical size exclusion chromatography (SEC). The PNIPAAm-modified HTHP (PNIPAAm-HTHP) is found to provide a 43 nm spherical structure at 60 °C, and the structural changes observed between the assembled and the disassembled forms were duplicated at least five times. High-speed atomic force microscopic measurements of the micellar assembly supported by cross-linkage with glutaraldehyde indicate that the protein matrices are located on the surface of the sphere and cover the inner PNIPAAm core. Furthermore, substitution of heme with a photosensitizer, Zn protoporphyrin IX (ZnPP), in the micellar assembly provides an artificial light-harvesting system. Photochemical measurements of the ZnPP-substituted micellar assembly demonstrate that energy migration among the arrayed ZnPP molecules occurs within the range of several tens of picoseconds. Our present work represents the first example of an artificial light-harvesting system based on an assembled hemoprotein oligomer structure to replicate natural light-harvesting systems.

A supramolecular assembly based on an engineered hemoprotein exhibiting a thermal stimulus-driven conversion to a new distinct supramolecular structure

Supramolecular assembly of an engineered hemoprotein with an externally-attached heme moiety via an azobenzene or stilbene linker demonstrates drastic structural transitions between two distinct forms: the thermodynamically stable fiber-type assembly and the kinetically trapped metastable micelle-type assembly induced by transient thermal stimulus.

Puroindoline-a, a lipid binding protein from common wheat, spontaneously forms prolate protein micelles in solution

The self-assembly in solution of puroindoline-a (Pin-a), an amphiphilic lipid binding protein from common wheat, was investigated by small angle neutron scattering, dynamic light scattering and size exclusion chromatography. Pin-a was found to form monodisperse prolate ellipsoidal micelles with a major axial radius of 112 ± 4.5 Å and minor axial radius of 40.4 ± 0.18 Å. These protein micelles were formed by the spontaneous self-assembly of 38 Pin-a molecules in solution and were stable over a wide pH range (3.5-11) and at elevated temperatures (20-65 °C). Pin-a micelles could be disrupted upon addition of the non-ionic surfactant dodecyl-β-maltoside, suggesting that the protein self-assembly is driven by hydrophobic forces, consisting of intermolecular interactions between Trp residues located within a well-defined Trp-rich domain of Pin-a.

EPR spectroscopy and electrospray ionization mass spectrometry reveal distinctive features of the iron site in leukocyte 12-lipoxygenase

The procedure for the expression and purification of recombinant porcine leukocyte 12-lipoxygenase using Escherichia coli [K.M. Richards, L.J. Marnett, Biochemistry 36 (1997) 6692-6699] was updated to make it possible to produce enough protein for physical measurements. Electrospray ionization tandem mass spectrometry confirmed the amino acid sequence. The redox properties of the cofactor iron site were examined by EPR spectroscopy at 25K following treatment with a variety of fatty acid hydroperoxides. Combination of the enzyme in a stoichiometric ratio with the hydroperoxides led to a g4.3 signal in EPR spectra instead of the g6 signal characteristic of similarly treated soybean lipoxygenase-1. Native 12-lipoxygenase was also subjected to electrospray ionization mass spectrometry. There was evidence for loss of the mass of an iron atom from the protein as the pH was lowered from 5 to 4. Native ions in these samples indicated that iron was lost without the protein completely unfolding.

Electrospray ionization mass spectrometry of soybean lipoxygenases: N-terminal acetylation, chemical modification, and solution conformation

Electrospray ionization mass spectrometry was used to examine both the covalent structure and solution conformation of the soybean lipoxygenases. The post-translational modifications of two lipoxgyenases were identified as N-terminal acetylations by tandem mass spectrometry of peptides generated by trypsin digestion. The N-terminal sequence suggests that the proteins were substrates for the plant homolog of the N-terminal acetyltransferase complex C in yeast. Analysis of samples of native lipoxygenase-3 produced ions corresponding within experimental error to the mass of the N-acetylated polypeptide and one iron atom. The precision of the measurements was within roughly 100 ppm for the 96,856 Da protein. This made it possible to detect the addition of a single oxygen atom to the enzyme in a chemical modification reaction with cumene hydroperoxide. The acid-induced denaturation of lipoxygenase-3, which was accompanied by nearly complete loss of catalytic activity, was observed below pH 3.5 with the appearance of ions in the mass spectrum derived from the apoprotein. There was no evidence for the loss of iron in the absence of unfolding. Solutions of lipoxygenase-3 incubated in 0.1M acetic acid produced ions with a novel charge state distribution suggesting a unique conformation. Circular dichroism measurements showed that the secondary structure features of the native protein were retained in the new conformation. Dynamic light scattering revealed that the new conformation was not a consequence of protein aggregation as the hydrodynamic radius of lipoxygenase-3 was significantly smaller in acetic acid solution than at pH 7.0. Remarkably, the enzyme incubated in acetic acid retained full catalytic activity.