Sweep, Step, Pulse, and Frequency-Based Techniques Applied to Protein Monolayer Electrochemistry at Nanoparticle Interfaces

Protein monolayer electrochemistry (PME), a strategy using synthetic platforms to study the electron transfer (ET) properties of adsorbed proteins, has been successfully applied to proteins adsorbed at monolayer-protected gold cluster (MPCs) assembled films, an adsorption interface shown to be an effective alternative, compared to traditional self-assembled monolayer (SAM) films, for the immobilization and study of ET proteins. Within PME studies, cyclic voltammetry (CV) remains the most commonly applied electrochemical technique in spite of several limitations that occur when the sweep technique is used at either platform. In particular, CV for PME at MPC films results in analysis complications stemming from the increased charging current inherent to electrochemical interfaces incorporating MPCs with capacitive properties. In this study, multiple electroanalytical techniques, involving step (chronocoulometry, CC), pulse (square wave voltammetry, SWV), and frequency-based impedance (electrochemical impedance spectroscopy, EIS) measurements, are applied to monolayers of adsorbed Pseudomonas aeruginosa azurin and horse heart cytochrome c at both MPC film assemblies as well as traditional SAMs. Electrochemical parameters (formal potential, electroactive surface coverage, double-layer capacitance, and ET rate constant) measured from these various techniques are directly compared and offer insight into the performance and reliability of each technique’s effectiveness in PME. While certain techniques result in measurements indistinguishable from CV, others offer distinct differences. Moreover, the application of alternative techniques reveals systemic limitations and complications within the electrochemical analysis that we further explore, including strategies for applying fast scanning techniques like SWV as well as the construction of MPC platforms with controlled levels of charging current that enable successful impedance analysis. The application of more advanced electrochemical techniques to developing electrochemical interfaces such as MPC film assemblies allows for a greater understanding of not only PME but also the applicability and effectiveness of these techniques to optimize the measurement of specific electrochemical parameters

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Genomic reconstruction of the SARS-CoV-2 epidemic in England

AbstractThe evolution of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus leads to new variants that warrant timely epidemiological characterization. Here we use the dense genomic surveillance data generated by the COVID-19 Genomics UK Consortium to reconstruct the dynamics of 71 different lineages in each of 315 English local authorities between September 2020 and June 2021. This analysis reveals a series of subepidemics that peaked in early autumn 2020, followed by a jump in transmissibility of the B.1.1.7/Alpha lineage. The Alpha variant grew when other lineages declined during the second national lockdown and regionally tiered restrictions between November and December 2020. A third more stringent national lockdown suppressed the Alpha variant and eliminated nearly all other lineages in early 2021. Yet a series of variants (most of which contained the spike E484K mutation) defied these trends and persisted at moderately increasing proportions. However, by accounting for sustained introductions, we found that the transmissibility of these variants is unlikely to have exceeded the transmissibility of the Alpha variant. Finally, B.1.617.2/Delta was repeatedly introduced in England and grew rapidly in early summer 2021, constituting approximately 98% of sampled SARS-CoV-2 genomes on 26 June 2021.</jats:p