An electrochemical microtiter plate for parallel spectroelectrochemical measurements

Nanomaterials Synthesis Discovery via Parallel Electrochemical Deposition

Electrodeposition of nanoparticles is investigated with a multichannel potentiostat in electrochemical and chemical arrays. De novo deposition and shape control of palladium nanoparticles are explored in arrays with a two-stage strategy. Initial conditions for electrodeposition of materials are discovered in a first stage and then used in a second stage to logically expand chemical and electrochemical parameters. Shape control is analyzed primarily with scanning electron microscopy. Using this approach, optimized conditions for the electrodeposition of cubic palladium nanoparticles were identified from a set of previously untested electrodeposition conditions. The parameters discovered through the array format were then successfully extrapolated to a traditional bulk three-electrode electrochemical cell. Electrochemical arrays were also used to explore electrodeposition parameters reported in previous bulk studies, further demonstrating the correspondence between the array and bulk systems. These results broadly highlight opportunities for electrochemical arrays, both for discovery and for further investigations of electrodeposition in nanomaterials synthesis.

Legion: An Instrument for High-Throughput Electrochemistry

Electrochemical arrays promise utility for accelerated hypothesis testing and breakthrough discoveries. Herein, we report a new high-throughput electrochemistry platform, colloquially called "Legion," for applications in electroanalysis and electrosynthesis. Legion consists of 96 electrochemical cells dimensioned to match common 96-well plates that are independently controlled with a field-programmable gate array. We demonstrate the utility of Legion by measuring model electrochemical probes, pH-dependent electron transfers, and electrocatalytic dehalogenation reactions. We consider advantages and disadvantages of this new instrumentation, with the hope of expanding the electrochemical toolbox.

Enhancement of the Antioxidant and Antimicrobial Activities of Porphyran through Chemical Modification with Tyrosine Derivatives

The chemical modification of porphyran hydrocolloid is attempted, with the objective of enhancing its antioxidant and antimicrobial activities. Sulfated galactan porphyran is obtained from commercial samples of the red algae Porphyra dioica using Soxhlet extraction with water at 100 °C and precipitation with isopropyl alcohol. The extracted porphyran is then treated with modified L-tyrosines in aqueous medium in the presence of NaOH, at ca. 70 °C. The modified tyrosines L1 and L2 are prepared through a Mannich reaction with either thymol or 2,4-di-tert-butylphenol, respectively. While the reaction with 2,4-di-tert-butylphenol yields the expected tyrosine derivative, a mixture of products is obtained with thymol. The resulting polysaccharides are structurally characterized and the respective antioxidant and antimicrobial activities are determined. Porphyran treated with the N-(2-hydroxy-3,5-di-tert-butyl-benzyl)-L-tyrosine derivative, POR-L2, presents a noticeable superior radical scavenging and antioxidant activity compared to native porphyran, POR. Furthermore, it exhibited some antimicrobial activity against S. aureus. The surface morphology of films prepared by casting with native and modified porphyrans is studied by SEM/EDS. Both POR and POR-L2 present potential applicability in the production of films and washable coatings for food packaging with improved protecting characteristics.

Stabilization-destabilization and redox properties of laccases from medicinal mushroom Ganoderma lucidum and human pathogen Yersinia enterocolitica

Laccases or benzenediol oxygen oxidoreductases (EC 1.10.3.2) are polyphenol multicopper oxidases that are known for their structural and functional diversity in various life forms. In the present study, the molecular and physico-chemical properties (redox-potential and secondary structures) of fungal laccase isozymes (FLIs) isolated from a medicinal mushroom Ganoderma lucidum were analyzed and compared with those of the recombinant bacterial laccases (rLac) obtained from different Yersinia enterocolitica strains. It was revealed that the FLIs contained His-Cys-His as the most conserved residue in its domain I Cu site, while the fourth and fifth residues were variable (Ile, Leu, or Phe). Evidently, the cyclic voltammetric measurements of Glac L2 at Type 1 Cu site revealed greater E° for ABTS/ABTS⁺ (0.312 V) and ABTS⁺/ABTS²⁺ (0.773 V) compared to the E° of rLac. Furthermore, circular dichroism-based conformational analysis revealed structural stability of the FLIs at acidic pH (3.0) and low temperature (<30 °C), while the isozymes were destabilized at neutral pH (7.0) and high-temperature conditions (>70 °C). The zymographic studies further confirmed the functional inactivation of FLIs at high temperatures (≥70 °C), predominantly due to domain unfolding. These findings provide novel insight into the evolution of the catalytic efficiency and redox properties of the FLIs, contributing to the existing knowledge regarding stress responses, metabolite production, and the biotechnological utilization of metabolites.

Proteomic analysis reveals the damaging role of low redox laccase from Yersinia enterocolitica strain 8081 in the midgut of Helicoverpa armigera

OBJECTIVE

Earlier, we have found that the enteropathogenic Yersinia enterocolitica have evolved the survival mechanisms that regulate the expression of laccase-encoding genes in the gut. The present study aims to characterize the purified recombinant laccase from Y. enterocolitica strain 8081 biovar 1B and understand its effect on the midgut of cotton bollworm, Helicoverpa armigera (Hübner) larvae.

RESULTS

The recombinant laccase protein showed high purity fold and low molecular mass (~ 43 kDa). H. armigera larvae fed with laccase protein showed a significant decrease in body weight and damage in the midgut. Further, transmission electron microscopy (TEM) studies revealed the negative effect of laccase protein on trachea, malpighian tubules, and villi of the insect. The proteome comparison between control and laccase-fed larvae of cotton bollworm showed significant expression of proteolytic enzymes, oxidoreductases, cytoskeletal proteins, ribosomal proteins; and proteins for citrate (TCA cycle) cycle, glycolysis, stress response, cell redox homeostasis, xenobiotic degradation, and insect defence. Moreover, it also resulted in the reduction of antioxidants, increased melanization (insect innate immune response), and enhanced free radical generation.

CONCLUSIONS

All these data collectively suggest that H. armigera (Hübner) larvae can be used to study the effect of microbes and their metabolites on the host physiology, anatomy, and survival.

Molecular modeling and MD-simulation studies: Fast and reliable tool to study the role of low-redox bacterial laccases in the decolorization of various commercial dyes

Synthetic dyes are toxic and carcinogenic in nature, which also causes environmental pollution. The present study was aimed to decolorize various commercial dyes using purified recombinant bacterial laccases. Laccase gene from Yersinia enterocolitica strain 8081 (yacK), Y. enterocolitica strain 7 (yacK) and Bacillus pumilus DSKK1 was cloned in vector pET28a and overproduced in host Escherichia coli BL21. The high yield of recombinant laccase protein resulted in the formation of inclusion bodies, which were further solubilized, refolded, and purified. The purified recombinant laccases were alkali-tolerant and thermostable, with pH optima at 7-8, temperature optima at 60-70 °C and low redox potential. For in silico studies, laccase protein models of B. pumilus DSKK1, Y. enterocolitica strain 7 and Y. enterocolitica strain 8081 were docked with commercial dyes. This is the first and foremost study where the stability of docked complexes of pathogenic and non-pathogenic microorganism has been explored via molecular dynamics (MD) simulations using Gromacs version 4.5.5 with the gromos96 43a force field. Finally, the in silico results were validated experimentally and it was found that purified laccases from B. pumilus DSKK1 and Y. enterocolitica strain 7 efficiently decolorized rose bengal (90.4%), malachite green (77.7%), and congo red (74.5%) dyes.

An integrated mass spectrometry platform enables picomole-scale real-time electrosynthetic reaction screening and discovery

The identification of new electrosynthetic pathways enables environmentally friendly synthetic applications. However, the development of miniaturized screening procedures/platforms to expedite the discovery of electrooxidation reactions remains challenging. Herein, we developed an integrated system that serves as a reactor and ion source in a single experimental step using only picomole-scale reactants to monitor electrooxidation in real-time. This reaction screening platform utilizes the intrinsic electrochemical capabilities of nano-electrospray ionization mass spectrometry. We validated the feasibility of this method by reproducing three known electrochemical reactions. We also discovered two new electroorganic reaction pathways: (i) C-N dehydrodimerization of 8-methyl-1,2,3,4-tetrahydroquinoline to construct a novel quinoline skeleton, and (ii) TEMPO-mediated accelerated electrooxidative dehydrogenation of tetrahydroisoquinolines. Moreover, the radical cations and key intermediates captured by this screening platform provided direct evidence for the mechanism of these novel electrochemical reactions.

Crystallographic insights into a cobalt (III) sepulchrate based alternative cofactor system of P450 BM3 monooxygenase

P450 BM3 is a multi-domain heme-containing soluble bacterial monooxygenase. P450 BM3 and variants are known to oxidize structurally diverse substrates. Crystal structures of individual domains of P450 BM3 are available. However, the spatial organization of the full-length protein is unknown. In this study, crystal structures of the P450 BM3 M7 heme domain variant with and without cobalt (III) sepulchrate are reported. Cobalt (III) sepulchrate acts as an electron shuttle in an alternative cofactor system employing zinc dust as the electron source. The crystal structure shows a binding site for the mediator cobalt (III) sepulchrate at the entrance of the substrate access channel. The mediator occupies an unusual position which is far from the active site and distinct from the binding of the natural redox partner (FAD/NADPH binding domain).