Tyrosinase-catalyzed site-specific immobilization of engineered C-phycocyanin to surface

Enzymes in "Green" Synthetic Chemistry: Laccase and Lipase

Enzymes play an important role in numerous natural processes and are increasingly being utilized as environmentally friendly substitutes and alternatives to many common catalysts. Their essential advantages are high catalytic efficiency, substrate specificity, minimal formation of byproducts, and low energy demand. All of these benefits make enzymes highly desirable targets of academic research and industrial development. This review has the modest aim of briefly overviewing the classification, mechanism of action, basic kinetics and reaction condition effects that are common across all six enzyme classes. Special attention is devoted to immobilization strategies as the main tools to improve the resistance to environmental stress factors (temperature, pH and solvents) and prolong the catalytic lifecycle of these biocatalysts. The advantages and drawbacks of methods such as macromolecular crosslinking, solid scaffold carriers, entrapment, and surface modification (covalent and physical) are discussed and illustrated using numerous examples. Among the hundreds and possibly thousands of known and recently discovered enzymes, hydrolases and oxidoreductases are distinguished by their relative availability, stability, and wide use in synthetic applications, which include pharmaceutics, food and beverage treatments, environmental clean-up, and polymerizations. Two representatives of those groups-laccase (an oxidoreductase) and lipase (a hydrolase)-are discussed at length, including their structure, catalytic mechanism, and diverse usage. Objective representation of the current status and emerging trends are provided in the main conclusions.

Oxidoreductase enzymes: Characteristics, applications, and challenges as a biocatalyst

Oxidoreductases are enzymes with distinctive characteristics that favor their use in different areas, such as agriculture, environmental management, medicine, and analytical chemistry. Among these enzymes, oxidases, dehydrogenases, peroxidases, and oxygenases are very interesting. Because their substrate diversity, they can be used in different biocatalytic processes by homogeneous and heterogeneous catalysis. Immobilization of these enzymes has favored their use in the solution of different biotechnological problems, with a notable increase in the study and optimization of this technology in the last years. In this review, the main structural and catalytical features of oxidoreductases, their substrate specificity, immobilization, and usage in biocatalytic processes, such as bioconversion, bioremediation, and biosensors obtainment, are presented.

Development of a novel ultrasound- and biocrosslinking-enhanced immobilization strategy with application to food enzymes

The increasing demand for greener food production makes biocatalysts more desirable than traditional production approaches. One limiting factor for biocatalyst efficiency is the immobilization strategy. In this work, a novel immobilization method was developed with the tyrosine-tag crosslinking mechanism. The immobilization efficiency was further enhanced with ultrasound treatment. Such a strategy was proven to be efficient with food enzyme lipase, d-amino acid oxidase and glucose dehydrogenase when they were immobilized on macroporous resins, amino resins, epoxy resins, and multiwalled carbon nanotubes. For lipase, glucose dehydrogenase and d-amino acid oxidase, the immobilization yield on macroporous resins increased by 20.4%, 21.1% and 24.1%, respectively. In addition, the immobilized enzymes had enhanced reusability, with a high degree of activity (more than 85%) detected after six cycles. Furthermore, the enzyme electrochemical sensors constructed by enzyme crosslinking have higher sensitivity, with peak currents 4-8 times those of sensors with uncrosslinked enzymes. The enzyme immobilization strategy developed in this study paves the way for better application of biocatalysts in the food industry.

Surface Functionalization and Texturing of Optical Metasurfaces for Sensing Applications

Optical metasurfaces are planar metamaterials that can mediate highly precise light-matter interactions. Because of their unique optical properties, both plasmonic and dielectric metasurfaces have found common use in sensing applications, enabling label-free, nondestructive, and miniaturized sensors with ultralow limits of detection. However, because bare metasurfaces inherently lack target specificity, their applications have driven the development of surface modification techniques that provide selectivity. Both chemical functionalization and physical texturing methodologies can modify and enhance metasurface properties by selectively capturing analytes at the surface and altering the transduction of light-matter interactions into optical signals. This review summarizes recent advances in material-specific surface functionalization and texturing as applied to representative optical metasurfaces. We also present an overview of the underlying chemistry driving functionalization and texturing processes, including detailed directions for their broad implementation. Overall, this review provides a concise and centralized guide for the modification of metasurfaces with a focus toward sensing applications.

Designed protein multimerization and polymerization for functionalization of proteins

Abstract

Multimeric and polymeric proteins are large biomacromolecules consisting of multiple protein molecules as their monomeric units, connected through covalent or non-covalent bonds. Genetic modification and post-translational modifications (PTMs) of proteins offer alternative strategies for designing and creating multimeric and polymeric proteins. Multimeric proteins are commonly prepared by genetic modification, whereas polymeric proteins are usually created through PTMs. There are two methods that can be applied to create polymeric proteins: self-assembly and crosslinking. Self-assembly offers a spontaneous reaction without a catalyst, while the crosslinking reaction offers some catalyst options, such as chemicals and enzymes. In addition, enzymes are excellent catalysts because they provide site-specificity, rapid reaction, mild reaction conditions, and activity and functionality maintenance of protein polymers. However, only a few enzymes are applicable for the preparation of protein polymers. Most of the other enzymes are effective only for protein conjugation or labeling. Here, we review novel and applicable strategies for the preparation of multimeric proteins through genetic modification and self-assembly. We then describe the formation of protein polymers through site-selective crosslinking reactions catalyzed by enzymes, crosslinking reactions of non-natural amino acids, and protein-peptide (SpyCatcher/SpyTag) interactions. Finally, we discuss the potential applications of these protein polymers.

Graphical abstract

A Metal Ion-Controlled Molecular "Open Bridge" Detecting Oxidative Stress-Disrupted Apoptotic Signaling in Pediatric Neuroblastoma

Neuroblastoma is a metastatic tumor almost exclusively plaguing young children. To provide an early warning for timely medical interference that may prevent such tragedies from happening, we mimic the biomolecular pathology of this disease and have obtained an assay without using costly biomolecules such as antibodies and enzymes but can still sensitively detect trace level metal ions and metastatic marker proteins in the cerebrospinal fluid of neuroblastoma-bearing children in a one-step and reagentless fashion. Specifically, a surface-tethered "open bridge"-like molecular machine is designed. This probe, after interacting with cupric ions, can form an electrochemically active peroxidase-like artificial enzyme. Its activity first opens the probe, freeing the Bcl-2-targeting sequence of the probe to adopt the most favorable conformation, forming a noncovalent complex with Bcl-2. Then, the peroxidase-like activity of the probe induces the formation a robust fluorescence covalent linkage with the target protein. This fluorescence and electrochemical dual detection allows an analytical performance not inferior to the commercially available methods, pointing to possible clinical application in the early screening of pediatric metastatic conditions in the near future.

Application of bacterial tyrosinases in organic synthesis

Bacterial tyrosinases, as in the case of other bacterial oxidative enzymes, have been found to possess biochemical characteristics that typically make them more suited to applications requiring special operational conditions such as alkaline pH, high or low temperature, the presence of organic solvents, and the presence of inhibitors. Even though a great deal is known about fungal tyrosinases, bacterial tyrosinases still vastly remain underexplored for their potential application in organic synthesis. A literature survey in particular highlights the gaps in our knowledge pertaining to their biochemical properties. Bacterial tyrosinases have not only shown promise in the synthesis of medically important compounds such as L-3,4-dihydroxyphenylalanine (L-DOPA) and melanin but have also seen application in cross-linking reactions of proteins and the polymerization of environmental pollutants. Their ability to catalyse o-hydroxylation reactions have shown some degree of promise in the biocatalytic conversion of resveratrol to piceatannol, tyrosol to hydroxytyrosol, and many more. In this review, we will explore the world of bacterial tyrosinases, their current applications, and future perspectives for the application of these enzymes in organic synthesis.

Reconstruction of the absorption spectrum of Synechocystis sp. PCC 6803 optical mutants from the in vivo signature of individual pigments

In this work, we reconstructed the absorption spectrum of different Synechocystis sp. PCC 6803 optical strains by summing the computed signature of all pigments present in this organism. To do so, modifications to in vitro pigment spectra were first required: namely wavelength shift, curve smoothing, and the package effect calculation derived from high pigment densities were applied. As a result, we outlined a plausible shape for the in vivo absorption spectrum of each chromophore. These are flatter and slightly broader in physiological conditions yet the mean weight-specific absorption coefficient remains identical to the in vitro conditions. Moreover, we give an estimate of all pigment concentrations without applying spectrophotometric correlations, which are often prone to error. The computed cell spectrum reproduces in an accurate manner the experimental spectrum for all the studied wavelengths in the wild-type, Olive, and PAL strain. The gathered pigment concentrations are in agreement with reported values in literature. Moreover, different illumination set-ups were evaluated to calculate the mean absorption cross-section of each chromophore. Finally, a qualitative estimate of light-limited cellular growth at each wavelength is given. This investigation describes a novel way to approach the cell absorption spectrum and shows all its inherent potential for photosynthesis research.

Complete inclusion of bioactive molecules and particles in polydimethylsiloxane: a straightforward process under mild conditions

By applying a slow curing process, we show that biomolecules can be incorporated via a simple process as liquid stable phases inside a polydimethylsiloxane (PDMS) matrix. The process is carried out under mild conditions with regards to temperature, pH and relative humidity, and is thus suitable for application to biological entities. Fluorescence and enzymatic activity measurements show that the biochemical properties of the proteins and enzyme tested are preserved, without loss due to adsorption at the liquid-polymer interface. Protected from external stimuli by the PDMS matrix, these soft liquid composite materials are new tools of interest for robotics, microfluidics, diagnostics and chemical microreactors.

From Protein Features to Sensing Surfaces

Proteins play a major role in biosensors in which they provide catalytic activity and specificity in molecular recognition. However, the immobilization process is far from straightforward as it often affects the protein functionality. Extensive interaction of the protein with the surface or significant surface crowding can lead to changes in the mobility and conformation of the protein structure. This review will provide insights as to how an analysis of the physico-chemical features of the protein surface before the immobilization process can help to identify the optimal immobilization approach. Such an analysis can help to preserve the functionality of the protein when on a biosensor surface.

Hierarchical Multicomponent Inorganic Metamaterials: Intrinsically Driven Self-Assembly at the Nanoscale

Increasingly intricate in their composition and structural organization, hierarchical multicomponent metamaterials with nonlinear spatially reconfigurable functionalities challenge the intrinsic constraints of natural materials, revealing tremendous potential for the advancement of biochemistry, nanophotonics, and medicine. Recent breakthroughs in high-resolution nanofabrication utilizing ultranarrow, precisely controlled ion or laser beams have enabled assembly of architectures of unprecedented structural and functional complexity, yet costly, time- and energy-consuming high-resolution sequential techniques do not operate effectively at industry-required scale. Inspired by the fictional Baron Munchausen's fruitless attempt to pull himself up, it is demonstrated that metamaterials can undergo intrinsically driven self-assembly, metaphorically pulling themselves up into existence. These internal drivers hold a key to unlocking the potential of metamaterials and mapping a new direction for the large-area, cost-efficient self-organized fabrication of practical devices. A systematic exploration of these efforts is presently missing, and the driving forces governing the intrinsically driven self-assembly are yet to be fully understood. Here, recent progress in the self-organized formation and self-propelled growth of complex hierarchical multicomponent metamaterials is reviewed, with emphasis on key principles, salient features, and potential limitations of this family of approaches. Special stress is placed on self-assembly driven by plasma, current in liquid, ultrasonic, and similar highly energetic effects, which enable self-directed formation of metamaterials with unique properties and structures.

ortho-Quinones and Analogues Thereof: Highly Reactive Intermediates for Fast and Selective Biofunctionalization

Fast, selective and facile functionalization of biologically relevant molecules is a pursuit of ever‐growing importance. A promising approach in this regard employs the high reactivity of quinone and quinone analogues for fast conjugation chemistry by nucleophilic addition or cycloadditions. Combined with in situ generation of these compounds, selective conjugation on proteins and surfaces can be uniquely induced in a time and spatially resolved manner: generation of a quinone can often be achieved by simple addition of an enzyme or stoichiometric amounts of chemoselective oxidant, or by exposure to light. In this Minireview, we discuss the generation and subsequent functionalization of quinones, iminoquinones, and quinone methides. We also discuss practical applications regarding these conjugation strategies.

Inducible, Site-Specific Protein Labeling by Tyrosine Oxidation-Strain-Promoted (4 + 2) Cycloaddition

Genetically encoded tyrosine (Y-tag) can be utilized as a latent anchor for inducible and site-selective conjugation. Upon oxidation of tyrosine with mushroom tyrosinase, strain-promoted cycloaddition (SPOCQ) of the resulting 1,2-quinone with various bicyclo[6.1.0]nonyne (BCN) derivatives led to efficient conjugation. The method was applied for fluorophore labeling of laminarinase A and for the site-specific preparation of an antibody-drug conjugate.

Recombinant Tyrosinase from Polyporus arcularius: Overproduction in Escherichia coli, Characterization, and Use in a Study of Aurones as Tyrosinase Effectors

Tyrosinases act in the development of organoleptic properties of tea, raisins, etc., but also cause unwanted browning of fruits, vegetables, and mushrooms. The tyrosinase from Agaricus bisporus has been used as a model to study tyrosinase inhibitors, which are also indispensable in the treatment of skin pigmentation disorders. However, this model has disadvantages such as side enzyme activities and the presence of multiple isoenzymes. Therefore, we aimed to introduce a new tyrosinase model. The pro-tyrosinase from Polyporus arcularius was overproduced in Escherichia coli. Trypsin digestion led to a cleavage after R388 and hence enzyme activation. The tyrosinase was a homodimer and transformed L-DOPA and tert-butylcatechol preferentially. Various aurons were examined as effectors of this enzyme. 2'- and 3'-hydroxyaurones acted as its activators and 2',4'-dihydroxyaurone as an inhibitor, whereas 4'-hydroxyaurones were its substrates. The enzyme is a promising model for tyrosinase effector studies, being a single isoenzyme and void of side enzyme activities.

Encapsulation of FRET-based glucose and maltose biosensors to develop functionalized silica nanoparticles

Silicate nanoparticles with immobilized FRET-based biosensors were developed for the detection of glucose and maltose.

Protein retention on plasma-treated hierarchical nanoscale gold-silver platform

Dense arrays of gold-supported silver nanowires of about 100 nm in diameter grown directly in the channels of nanoporous aluminium oxide membrane were fabricated and tested as a novel platform for the immobilization and retention of BSA proteins in the microbial-protective environments. Additional treatment of the silver nanowires using low-temperature plasmas in the inductively-coupled plasma reactor and an atmospheric-pressure plasma jet have demonstrated that the morphology of the nanowire array can be controlled and the amount of the retained protein may be increased due to the plasma effect. A combination of the neutral gold sublayer with the antimicrobial properties of silver nanowires could significantly enhance the efficiency of the platforms used in various biotechnological processes.

Plasma treatment for next-generation nanobiointerfaces

Energy deficiency, global poverty, chronic hunger, chronic diseases, and environment conservation are among the major problems threatening the whole mankind. Nanostructure-based technologies could be a possible solution. Such techniques are now used for the production of many vitally important products including cultured and fermented food, antibiotics, various medicines, and biofuels. On the other hand, the nanostructure-based technologies still demonstrate low efficiency and controllability, and thus still are not capable to decisively address the global problems. Furthermore, future technologies should ensure lowest possible environmental impact by implementing green production principles. One of the most promising approaches to address these challenges are the sophisticatedly engineered biointerfaces. Here, the authors briefly evaluate the potential of the plasma-based techniques for the fabrication of complex biointerfaces. The authors consider mainly the atmospheric and inductively coupled plasma environments and show several examples of the artificial plasma-created biointerfaces, which can be used for the biotechnological and medical processes, as well as for the drug delivery devices, fluidised bed bioreactors, catalytic reactors, and others. A special attention is paid to the plasma-based treatment and processing of the biointerfaces formed by arrays of carbon nanotubes and graphene flakes.

Enzymatic multi-functionalization of microparticles under aqueous neutral conditions

Enzymatic multi-functionalization of microparticles under aqueous neutral conditions using tyrosinase.