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ObjectiveTo identify the factors that affect coronavirus disease 2019 (COVID-19) vaccine decision making among individuals diagnosed with a rheumatologic condition, given that previous international studies have demonstrated that a significant proportion of patients with rheumatic disease (RD) are vaccine hesitant.MethodsThis cross-sectional study involved an online survey with adult patients with RD from the Kaye Edmonton Clinic Rheumatology Clinic between June and August 2021. Quantitative results were descriptively analyzed, whereas qualitative thematic analysis was conducted for open-ended responses.ResultsThe survey had a response rate of 70.9% (N = 231). Regarding COVID-19 vaccines, patients with RD were most concerned about the possible effect of vaccination on their rheumatic condition (45.2%) and about vaccine effectiveness (45.1%). Most patients had discussed COVID-19 vaccination (75.9%) and its risks and benefits (66.1%) with their medical team, and 83.6% of respondents were confident in the information provided. Patients’ perceptions of the government’s role in handling the COVID-19 pandemic varied: 33% reported that they found government-instituted public health measures effective. Surprisingly, 9.7% of patients with RD still reported concerns that they could develop COVID-19 from an approved COVID-19 vaccine.ConclusionThis study describes factors implicated in COVID-19 vaccine decision making among patients with RD. Three important themes included possible adverse effects of the vaccine on RD control, reduced vaccine efficacy because of RD/treatment, and risk of contracting SARS-CoV-2 from the COVID-19 vaccine. Knowledge from this study can assist healthcare providers in looking after patients with RD to initiate discussions with patients to share evidence-based vaccine information and assist with informed decision making.

Bacteria that live at the oxic/anoxic interface have to rapidly adapt to changes in oxygen levels within their environment. The facultative anaerobe Shewanella oneidensis MR-1 can use EET to respire in the absence of oxygen, but on exposure to oxygen, EET could directly reduce extracellular oxygen and generate harmful reactive oxygen species that damage the bacterium.

Aim: To assess the level of knowledge and awareness of undergraduate medical students in order to determine whether the undergraduate virology course is up to standard for preparation of the COVID-19 pandemic. Methodology: A cross-sectional study was conducted online by random-sampling method with a multi-central approach. Data was collected from 311 respondents for a time period of one month during May 2020. IRB approval was granted. Descriptive analysis was done on student demographics, their knowledge and opinions, using the research tool SPSS 24. Results: Majority of students had factually correct knowledge about Covid-19, according to the WHO guidelines. However, there was poor knowledge regarding animal reservoirs and other diseases caused by Coronaviruses. Most students had learned about Coronaviruses from sources apart from the syllabi or course material and 93% were in agreement for wanting an improved Coronavirus module in their undergraduate virology courses. Conclusion: Medical students have good knowledge about Coronavirus, but are lacking in some crucial topics such as sources of animal reservoir and types of diseases etc. More studies need to be conducted in order to assess whether undergraduate syllabi are sufficient for educating and training students about future possible pandemics. An efficient prospective course of action should be determined accordingly. Keywords: Medical students, Coronaviruses, Covid-19, Pandemic, Knowledge, Awareness.

Introduction Proactive deprescribing – identifying and discontinuing medicines where harms outweigh benefits (1) – can minimise problematic polypharmacy, but it has not been routinely implemented into practice and can have risks. There are complex barriers and facilitators to deprescribing, however there is little evidence about how to overcome such barriers or promote facilitators and what resources are needed to safely and routinely implement deprescribing in primary care. Aim To co-design deprescribing resources that aid the implementation of safe and routine deprescribing in primary care. Methods Community-dwelling patients aged ≥65 years taking ≥5 medicines, community pharmacists, primary care pharmacists and GPs were invited to co-design workshops conducted in July 2022. Participants were recruited through social media and research networks. This project did not require formal ethical approval as it was a service improvement initiative. Two online workshops were facilitated using Microsoft Teams and Miro boards and were supported by a Patient and Public Involvement representative. The first workshop comprised a briefing about findings from a scoping review, systematic review and interview study with patients and healthcare professionals about deprescribing implementation, followed by idea generation through group activities. Potential resources identified were collated and, through discussions with the wider research team, two were prioritised to be further developed. The second workshop used storyboards to further understand and add detail to how the resources chosen would aid the implementation of routine and safe deprescribing in primary care. A logic model was then developed for the resource developed in the workshop. Results Five patients, two GPs, one primary care pharmacist and one community pharmacist took part. In the first workshop, participants identified:(a) patients were suitable advocates for their own health and could initiate conversations about medicines necessity but may need prompts or suggested questions to do so; and (b) community pharmacist follow-up with patients post-deprescribing could help ensure safe deprescribing and facilitate appraisal of deprescribing for future learning. In the second workshop, five questions patients could ask healthcare professionals during everyday interactions and two questions patients could ask during a medication review were developed to stimulate conversations on the necessity of medicines. A storyboard about how community pharmacy could act as a safety net post-deprescribing was developed and refined, following the workshop, into a Real World Logic Model (2) to explain how this safety net could work, the safety net context, and the anticipated outcomes. Conclusion Patients may be able to stimulate conversations on medicine necessity leading to routine deprescribing, whilst community pharmacists could potentially help ensure deprescribing safety. Questions were developed to empower patients to raise the issue of medicines necessity, and a logic model demonstrating community pharmacists as a deprescribing safety net were developed to aid safe and routine deprescribing in primary care. The co-participation of patients and healthcare professionals ensured that both groups’ values and priorities informed intervention development. However, the acceptability and usability of the co-designed interventions cannot be known until feasibility testing has been conducted. References 1. Scott IA, Hilmer SN, Reeve E, Potter K, Le Couteur D, Rigby D, et al. Reducing Inappropriate Polypharmacy: The Process of Deprescribing. JAMA Internal Medicine. 2015;175(5):827-34. 2. Mills, T., Shannon, R., O’Hara, J., Lawton, R., & Sheard, L. (2022). Development of a ‘real-world’ logic model through testing the feasibility of a complex healthcare intervention: the challenge of reconciling scalability and context-sensitivity. Evaluation, 28(1), 113–131.

Funder: Engineering and Physical Sciences Research Council, Funder: Verband der Chemischen Industrie, Thiosulfate dehydrogenases are bacterial cytochromes that contribute to the oxidation of inorganic sulfur. The active sites of these enzymes contain low-spin c-type heme with Cys-/His axial ligation. However, the reduction potentials of these hemes are several hundred mV more negative than that of the thiosulfate/tetrathionate couple (Em, +198 mV), making it difficult to rationalize the thiosulfate oxidizing capability. Here, we describe the reaction of Campylobacter jejuni thiosulfate dehydrogenase (TsdA) with sulfite, an analogue of thiosulfate. The reaction leads to stoichiometric conversion of the active site Cys to cysteinyl sulfonate (Cα-CH2-S-SO3-) such that the protein exists in a form closely resembling a proposed intermediate in the pathway for thiosulfate oxidation that carries a cysteinyl thiosulfate (Cα-CH2-S-SSO3-). The active site heme in the stable sulfonated protein displays an Em approximately 200 mV more positive than the Cys-/His-ligated state. This can explain the thiosulfate oxidizing activity of the enzyme and allows us to propose a catalytic mechanism for thiosulfate oxidation. Substrate-driven release of the Cys heme ligand allows that side chain to provide the site of substrate binding and redox transformation; the neighboring heme then simply provides a site for electron relay to an appropriate partner. This chemistry is distinct from that displayed by the Cys-ligated hemes found in gas-sensing hemoproteins and in enzymes such as the cytochromes P450. Thus, a further class of thiolate-ligated hemes is proposed, as exemplified by the TsdA centers that have evolved to catalyze the controlled redox transformations of inorganic oxo anions of sulfur.

Nitrous oxide (N2O) is a potent greenhouse and ozone‐reactive gas for which emissions are growing rapidly due to increasingly intensive agriculture. Synthetic catalysts for N2O decomposition typically contain precious metals and/or operate at elevated temperatures driving a desire for more sustainable alternatives. Here we demonstrate self‐assembly of liposomal microreactors enabling catalytic reduction of N2O to the climate neutral product N2. Photoexcitation of graphitic N‐doped carbon dots delivers electrons to encapsulated N2O Reductase enzymes via a lipid‐soluble biomolecular wire provided by the MtrCAB protein complex. Within the microreactor, electron transfer from MtrCAB to N2O Reductase is facilitated by the general redox mediator methyl viologen. The liposomal microreactors use only earth‐abundant elements to catalyze N2O removal in ambient, aqueous conditions.

In peridynamic models for fracture, the dissipated fracture energy is regularized over a non-local region denoted as the peridynamic horizon. This paper investigates the influence of this parameter on the dynamic fracture process in brittle solids, using two as well as three dimensional simulations of dynamic fracture propagation in a notched plate for two loading cases. The predicted crack speed for the various scenarios of the initially stored energy, also known as the velocity toughening behavior as well as characteristics of the crack surface topology obtained in different crack propagation regimes in 3D computational simulations are compared with the experimentally observed crack velocity and fracture surfaces for Polymethyl Methacrylate (PMMA) specimens. In addition, we investigate the influence of the specimen size on the dynamic fracture process using two dimensional peridynamic simulations. The fracture strengths and the velocity toughening relationship obtained from different specimen sizes are compared with the Linear Elastic Fracture Mechanics (LEFM) size effect relationship and with results from experiments, respectively.

Microbial nanowires are fascinating biological structures that allow bacteria to transport electrons over micrometers for reduction of extracellular substrates. It was recently established that the nanowires of both Shewanella and Geobacter are made of multi-heme proteins; but, while Shewanella employs the 20-heme protein complex MtrCAB, Geobacter uses a redox polymer made of the hexa-heme protein OmcS, begging the question as to which protein architecture is more efficient in terms of long-range electron transfer. Using a multiscale computational approach we find that OmcS supports electron flows about an order of magnitude higher than MtrCAB due to larger heme-heme electronic couplings and better insulation of hemes from the solvent. We show that heme side chains are an essential structural element in both protein complexes, accelerating rate-limiting electron tunnelling steps up to 1000-fold. Our results imply that the alternating stacked/T-shaped heme arrangement present in both protein complexes may be an evolutionarily convergent design principle permitting efficient electron transfer over very long distances.

Introduction Problematic polypharmacy in older people living with frailty can cause harm due to adverse drug events and deprescribing (withdrawing inappropriate medication to manage polypharmacy and improve outcomes (1)) is one solution to mitigate this. Structured Medication Reviews (SMRs) have been commissioned in England to be conducted by Primary Care Network (PCN) pharmacists for which older people living with frailty are a priority group. SMRs are an ideal opportunity to deprescribe for this high-risk population and a person-centred approach is required to ensure deprescribing is safe, effective and acceptable to patients. However, the optimal deprescribing process has not been developed and tested in this context. Aim To develop a person-centred process for deprescribing for older people living with frailty which could potentially be implemented within SMRs in primary care. Methods We conducted qualitative research with older people living with frailty, carers and primary healthcare professionals to identify barriers and facilitators to deprescribing in this context in the North of England (2). We then used these findings and a “trigger film” of patients’ experiences to conduct Experience-based Co-design (EBCD), a multi-event process where older people living with frailty, informal carers and primary healthcare professionals came together to determine the key features of an ideal deprescribing process and identify priorities for a complex intervention to support the process. Following this, we presented the process model for feedback at the training day of a large multi-site primary care practice based (involving pharmacists, GPs and administrative practice staff) in the North of England and subsequently refined the model to integrate within their evolving SMR programme. Results The co-designed deprescribing process consisted of 3 phases: 1. Prior to the SMR consultation which involved case-finding of high-risk patients, case-note review for deprescribing eligibility and clinician planning for the consultation, inviting and preparing the patient for the consultation with written information (including what to expect during the medication review, and questions for patients about their medicines to reflect upon); 2. The consultation which included shared decision-making, agreement of plans to stop medicines, recording of decisions in the electronic health record, providing written information for patients on how to safely stop their medicines, safety netting and signposting to post-deprescribing support; 3. Post-consultation which involved evaluating patient experiences and organising follow-up and further review as needed. Key elements of the optimal process to ensure it was person-centred, were effective written and verbal communication for patients (during the entire process), shared decision-making and tailored support post-consultation. Conclusion We have developed a person-centred process for deprescribing for older people living with frailty and adapted it for implementation within nationally commissioned SMRs in England. Although the model is grounded in the requirements of multiple stakeholders, the final version requires evaluation. The next steps are to design and develop tools which can support our deprescribing process and to undertake feasibility testing in primary care. References 1. Reeve E, Gnjidic D, Long J, Hilmer S. A systematic review of the emerging definition of 'deprescribing' with network analysis: implications for future research and clinical practice. Br J Clin Pharmacol. 2015;80(6):1254-1268. 2. Peat G, Fylan B, Marques I, Raynor DK, Breen L, Olaniyan J, Alldred DP. Barriers and enablers of successful deprescribing as described by older patients with frailty, supporting peers and clinicians: A qualitative interview study. BMJ Open 2022. 12:e054279.

Background Carbon monoxide (CO) poisoning is one of the most critical health concerns worldwide due to severe clinical effects with high morbidity and mortality. Tissue hypoxia and cellular damage from CO poisoning results in oxidative stress. Organs and tissues with high O2 demand including central nervous system (CNS) and cardiovascular (CV) system are the most susceptible to this oxidative stress. We investigate and describe the cardiovascular manifestations in 350 patients who were admitted for moderate to severe CO poisoning and treated with hyperbaric oxygen (HBO2) therapy. Purpose This study was conducted to identify the common cardiovascular manifestations of carbon monoxide poisoning. Methods We retrospectively collected data on 350 consecutive adult patients treated for CO poisoning between January 2011 to April 2018. Cardiac biomarkers, EKG and carboxyhemoglobin (COHb) levels were obtained from pre-hospital sources including EMS (emergency medical services) and from outside hospital records at the time of transfer. Glasgow Coma Scale (GCS) measurements were obtained at initial pre-hospital evaluation and upon arrival to the emergency room. Patient demographics, CV, CNS history and cardiac risk factors including hypertension, hyperlipidemia, diabetes, smoking history were obtained from electronic medical record. Myocardial injury was defined by cardiac troponin I level of ≥0.05 ng/mL. Results There were 350 patients admitted for CO poisoning from 2011 to 2018. 72% of the patients received HBO treatment due to severity of their symptoms. The mean age was 47.3 years with 60% men, 89% of the admissions were accidental exposure. Cardiac biomarkers were elevated in 40% of the patients and with 21% having sinus tachycardia. 6% had ischemic EKG changes with 23% having regional wall motion abnormalities on echocardiogram. In terms of intervention, 83% of the patients with elevated cardiac biomarkers received HBO treatment, 9% underwent coronary angiogram out of which 50% were candidate for either percutaneous intervention (PCI) or coronary artery bypass graft (CABG). In hospital mortality amongst this population was 2%. Conclusion Myocardial injury is common and widely seen with CO poisoning as seen by elevated cardiac biomarkers in 40% of the tested population. Initial work up for patients with CO poisoning should include evaluation with an EKG and serial biomarkers. If an abnormality is detected, patient should undergo an echocardiogram. Further evaluation with coronary angiography may be warranted in patients with new left ventricular dysfunction or wall motion abnormalities, especially in patients with risk factors. Funding Acknowledgement Type of funding sources: None.

Proteins achieve efficient energy storage and conversion through electron transfer along a series of redox cofactors. Multiheme cytochromes are notable examples. These proteins transfer electrons over distance scales of several nanometers to >10 μm and in so doing they couple cellular metabolism with extracellular redox partners including electrodes. Here we report pump-probe spectroscopy that provides a direct measure of the intrinsic rates of heme-heme electron transfer in this fascinating class of proteins. Our study took advantage of a spectrally unique His/Met ligated heme introduced at a defined site within the decaheme extracellular MtrC protein of Shewanella oneidensis. We observed rates of heme-to-heme electron transfer on the order of 109 s-1 (3.7-4.3 A edge-to-edge distance), in good agreement with predictions based on density functional and molecular dynamics calculations. These rates are amongst the highest reported for ground state electron transfer in biology. Yet, some fall 2-3 orders of magnitude below the Moser-Dutton ruler because electron transfer at these short distances is through-space and therefore associated with a higher tunneling barrier than the through-protein tunneling scenario that is usual at longer distances. Moreover, we show that the His/Met ligated heme creates an electron sink that stabilizes the charge separated state on the 100 microsecond time scale. This feature could be exploited in future designs of multiheme cytochromes as components of versatile photosynthetic biohybrid assemblies.

Shewanella oneidensis exchanges electrons between cellular metabolism and external redox partners in a process that attracts much attention for production of green electricity (microbial fuel cells) and chemicals (microbial electrosynthesis). A critical component of this pathway is the outer membrane spanning MTR complex, a biomolecular wire formed of the MtrA, MtrB, and MtrC proteins. MtrA and MtrC are decaheme cytochromes that form a chain of close-packed hemes to define an electron transfer pathway of 185 Å. MtrA is wrapped inside MtrB for solubility across the outer membrane lipid bilayer; MtrC sits outside the cell for electron exchange with external redox partners. Here, we demonstrate tight and spontaneous in vitro association of MtrAB with separately purified MtrC. The resulting complex is comparable with the MTR complex naturally assembled by Shewanella in terms of both its structure and rates of electron transfer across a lipid bilayer. Our findings reveal the potential for building bespoke electron conduits where MtrAB combines with chemically modified MtrC, in this case, labeled with a Ru-dye that enables light-triggered electron injection into the MtrC heme chain.

Thiosulfate dehydrogenases (TsdA) are bidirectional bacterial di-heme enzymes that catalyze the interconversion of tetrathionate and thiosulfate at measurable rates in both directions. In contrast to our knowledge of TsdA activities, information on the redox properties in the absence of substrates is rather scant. To address this deficit, we combined magnetic circular dichroism (MCD) spectroscopy and protein film electrochemistry (PFE) in a study to resolve heme ligation and redox chemistry in two representative TsdAs. We examined the TsdAs from Campylobacter jejuni, a micro-aerobe human pathogen, and from the purple sulfur bacterium Allochromatium vinosum. In these organisms, the enzyme functions as a tetrathionate reductase and a thiosulfate oxidase respectively. The active site Heme 1 in both enzymes has His/Cys− ligation in the ferric and ferrous states and the midpoint potentials (Em) of the corresponding redox transformations are similar, −185 mV versus standard hydrogen electrode (SHE). However, fundamental differences are observed in the properties of the second, electron transferring, Heme 2. In C. jejuni TsdA Heme 2 has His/Met ligation and an Em of +172 mV. In A. vinosum TsdA, Heme 2 reduction triggers a switch from His/Lys ligation (Em, −129 mV) to His/Met (Em,+266 mV) but the rates of interconversion are such that His/Lys ligation would be retained during turnover. In summary, our findings have unambiguously assigned Em values to defined axial ligand sets in TsdAs, specified the rates of Heme 2 ligand exchange in the A. vinosum enzyme, and provided information relevant to describing their catalytic mechanism(s).

Campylobacter jejuni is a microaerophilic zoonotic pathogen with an atypical respiratory Complex I that oxidizes a flavodoxin (FldA) instead of NADH. FldA is essential for viability and is reduced via pyruvate and 2-oxoglutarate oxidoreductases (POR/OOR). Here, we show that FldA can also be reduced by FqrB (Cj0559), an NADPH:FldA reductase. An fqrB deletion mutant was viable but displayed a significant growth defect. FqrB is related to flavoprotein reductases from Gram-positive bacteria that can reduce NrdI, a specialized flavodoxin that is needed for tyrosyl radical formation in NrdF, the beta subunit of class 1b-type (Mn) ribonucleotide reductase (RNR). However, C. jejuni possesses a single class Ia-type (Fe) RNR (NrdAB) that would be expected to be ferredoxin dependent. We show that CjFldA is an unusually high potential flavodoxin unrelated to NrdI, yet growth of the fqrB mutant, but not the wild-type or a complemented strain, was stimulated by low deoxyribonucleoside (dRNS) concentrations, suggesting FldA links FqrB and RNR activity. Using purified proteins, we confirmed the NrdB tyrosyl radical could be regenerated in an NADPH, FqrB, and FldA dependent manner, as evidenced by both optical and electron paramagnetic resonance (EPR) spectroscopy. Thus, FldA activates RNR in C. jejuni, partly explaining its essentiality.

This paper presents a novel concept for vibration-based feature extraction to identify damages in cutting discs of Tunnel Boring Machines (TBM). Defect frequencies resulting from repeated interaction of rock and disc defects are analysed. The data set is represented by the normal force acting on the edge of a cutting disc and the rock. Two different methods, the Hilbert transform and the complex demodulation, are used to generate the envelope of the time series, which was used to analyse whether the signal shows a feature representing an existing defect in the frequency domain. For the first proof of concept two numerical models were used - a multi-body system and a peridynamics 3D model simulating time series of normal forces. With both models, the linear motion of the disc on a rock sample with constant velocity was simulated. An experimental setup, mechanically similar to the simulations, was used in two experiments for further comparison. All implemented defects could be detected using vibration data of forces and one of the proposed data analysis techniques.

A growing number of bacterial species are known to move electrons across their cell envelopes. Naturally this occurs in support of energy conservation and carbon-fixation. For biotechnology it allows electron exchange between bacteria and electrodes in microbial fuel cells and during microbial electrosynthesis. In this context Rhodopseudomonas palustris TIE-1 is of much interest. These bacteria respond to light by taking electrons from their external environment, including electrodes, to drive CO2-fixation. The PioA cytochrome, that spans the bacterial outer membrane, is essential for this electron transfer and yet little is known about its structure and electron transfer properties. Here we reveal the ten c-type hemes of PioA are redox active across the window +250 to −400 mV versus Standard Hydrogen Electrode and that the hemes with most positive reduction potentials have His/Met and His/H2O ligation. These chemical and redox properties distinguish PioA from the more widely studied family of MtrA outer membrane decaheme cytochromes with ten His/His ligated hemes. We predict a structure for PioA in which the hemes form a chain spanning the longest dimension of the protein, from Heme 1 to Heme 10. Hemes 2, 3 and 7 are identified as those most likely to have His/Met and/or His/H2O ligation. Sequence analysis suggests His/Met ligation of Heme 2 and/or 7 is a defining feature of decaheme PioA homologs from over 30 different bacterial genera. His/Met ligation of Heme 3 appears to be less common and primarily associated with PioA homologs from purple non-sulphur bacteria belonging to the alphaproteobacteria class.

Redox enzymes can generate electricity from sunlight and produce valuable chemicals, including fuels, from low-value materials. When an electrode takes the role of an enzyme's natural redox partner, these properties inspire creative approaches to generate renewable resources. Enzymatic fuel cells produce electricity, enzyme electrosynthesis drives chemical transformations and biophotovoltaics harness solar energy. Underpinning rational development of these applications, time-dependent currents resolved by dynamic electrochemistry provide quantitative insight into the determinants of enzyme activity. This article reviews popular and emerging routes to sequester, study and exploit redox enzymes on two- and three-dimensional electrode materials. Studies are highlighted that draw on synergies of these different aspects of enzyme electrochemistry.

Peridynamics is a nonlocal continuum model which offers benefits over classical continuum models in cases, where discontinuities, such as cracks, are present in the deformation field. However, the nonlocal characteristics of peridynamics leads to a dispersive dynamic response of the medium. In this study we focus on the dispersion properties of a state-based linear peridynamic solid model and specifically investigate the role of the peridynamic horizon. We derive the dispersion relation for one, two and three dimensional cases and investigate the effect of horizon size, mesh size (lattice spacing) and the influence function on the dispersion properties. We show how the influence function can be used to minimize wave dispersion at a fixed lattice spacing and demonstrate it qualitatively by wave propagation analysis in one- and two-dimensional models of elastic solids. As a main contribution of this paper, we propose to associate peridynamic non-locality expressed by the horizon with a characteristic length scale related to the material microstructure. To this end, the dispersion curves obtained from peridynamics are compared with experimental data for two kinds of sandstone.

Acute myocardial infarction (AMI) and heart failure (HF) are two major causes of cardiovascular mortality and morbidity. Early diagnosis of these conditions is essential to instigate immediate treatment that may result in improved outcomes. Traditional biomarkers of AMI include cardiac troponins and other proteins released from the injured myocardium but there are a number of limitations with these biomarkers especially with regard to specificity. In the past few years circulating nucleic acids, notably microRNA that are small non-coding RNAs that regulate various cellular processes, have been investigated as biomarkers of disease offering improved sensitivity and specificity in the diagnosis and prognostication of various conditions. In this review, the role of microRNAs as biomarkers used in the diagnosis of AMI and HF is discussed, their advantage over traditional biomarkers is outlined and the potential for their implementation in clinical practice is critically assessed.

The high quantum efficiency of natural photosynthesis has inspired chemists for solar fuel synthesis. In photosynthesis, charge recombination in photosystems is minimized by efficient charge separation across the thylakoid membrane. Building on our previous bioelectrochemical studies of electron transfer between a light-harvesting nanoparticle (LHNP) and the decahaem subunit MtrC, we demonstrate photo-induced electron transfer through the full transmembrane MtrCAB complex in liposome membranes. Successful photoelectron transfer is demonstrated by the decomposition of a redox dye, Reactive Red 120 (RR120), encapsulated in MtrCAB proteoliposomes. The photoreduction rates are found to be dependent on the identity of the external LHNPs, specifically, dye-sensitized TiO2, amorphous carbon dots (a-CD) and graphitic carbon dots with core nitrogen doping (g-N-CDs). Agglomeration or aggregation of TiO2 NPs likely reduces the kinetics of RR120 reductive decomposition. In contrast, with the dispersed a-CD and g-N-CDs, the kinetics of the RR120 reductive decomposition are observed to be faster with the MtrCAB proteoliposomes and we propose that this is due to enhancement in the charge-separated state. Thus, we show a proof-of-concept for using MtrCAB as a lipid membrane-spanning building block for compartmentalised photocatalysis that mimics photosynthesis. Future work is focused on incorporation of fuel generating redox catalysts in the MtrCAB proteoliposome lumen.

Nature employs membrane-spanning proteins with electroactive cofactors as conduits for electron exchange between intracellular and extracellular environments. In this issue of Chem , Kirchhofer et al. describe an amphiphilic ferrocene that imitates these proteins by increasing anodic current from lactate-oxidizing Shewanella oneidensis .

The transfer of photoenergized electrons from extracellular photosensitizers across a bacterial cell envelope to drive intracellular chemical transformations represents an attractive way to harness nature's catalytic machinery for solar‐assisted chemical synthesis. In Shewanella oneidensis MR‐1 (MR‐1), trans‐outer‐membrane electron transfer is performed by the extracellular cytochromes MtrC and OmcA acting together with the outer‐membrane‐spanning porin⋅cytochrome complex (MtrAB). Here we demonstrate photoreduction of solutions of MtrC, OmcA, and the MtrCAB complex by soluble photosensitizers: namely, eosin Y, fluorescein, proflavine, flavin, and adenine dinucleotide, as well as by riboflavin and flavin mononucleotide, two compounds secreted by MR‐1. We show photoreduction of MtrC and OmcA adsorbed on RuII‐dye‐sensitized TiO2 nanoparticles and that these protein‐coated particles perform photocatalytic reduction of solutions of MtrC, OmcA, and MtrCAB. These findings provide a framework for informed development of strategies for using the outer‐membrane‐associated cytochromes of MR‐1 for solar‐driven microbial synthesis in natural and engineered bacteria.

The enzymes of the thiosulfate dehydrogenase (TsdA) family are wide-spread diheme c-type cytochromes. Here, redox carriers were studied mediating the flow of electrons arising from thiosulfate oxidation into respiratory or photosynthetic electron chains. In a number of organisms, including Thiomonas intermedia and Sideroxydans lithotrophicus, the tsdA gene is immediately preceded by tsdB encoding for another diheme cytochrome. Spectrophotometric experiments in combination with enzymatic assays in solution showed that TsdB acts as an effective electron acceptor of TsdA in vitro when TsdA and TsdB originate from the same source organism. Although TsdA covers a range from −300 to +150 mV, TsdB is redox active between −100 and +300 mV, thus enabling electron transfer between these hemoproteins. The three-dimensional structure of the TsdB-TsdA fusion protein from the purple sulfur bacterium Marichromatium purpuratum was solved by X-ray crystallography to 2.75 Å resolution providing insights into internal electron transfer. In the oxidized state, this tetraheme cytochrome c contains three hemes with axial His/Met ligation, whereas heme 3 exhibits the His/Cys coordination typical for TsdA active sites. Interestingly, thiosulfate is covalently bound to Cys330 on heme 3. In several bacteria, including Allochromatium vinosum, TsdB is not present, precluding a general and essential role for electron flow. Both AvTsdA and the MpTsdBA fusion react efficiently in vitro with high potential iron-sulfur protein from A. vinosum (Em +350 mV). High potential iron-sulfur protein not only acts as direct electron donor to the reaction center in anoxygenic phototrophs but can also be involved in aerobic respiratory chains.

Acute myocardial infarction (AMI) and heart failure (HF) are two major causes of cardiovascular mortality and morbidity. Early diagnosis of these conditions is essential to instigate immediate treatment that may result in improved outcomes. Traditional biomarkers of AMI include cardiac troponins and other proteins released from the injured myocardium but there are a number of limitations with these biomarkers especially with regard to specificity. In the past few years circulating nucleic acids, notably microRNA that are small non-coding RNAs that regulate various cellular processes, have been investigated as biomarkers of disease offering improved sensitivity and specificity in the diagnosis and prognostication of various conditions. In this review, the role of microRNAs as biomarkers used in the diagnosis of AMI and HF is discussed, their advantage over traditional biomarkers is outlined and the potential for their implementation in clinical practice is critically assessed.

A growing number of bacteria are recognised to conduct electrons across their cell envelope and yet molecular details of the mechanisms supporting this process remain unknown. Here we report the atomic structure of an outer membrane spanning protein complex, MtrAB, that is representative of a protein family known to transport electrons between the interior and exterior environments of phylogenetically and metabolically diverse microorganisms. The structure is revealed as a naturally insulated biomolecular wire possessing a 10-heme cytochrome, MtrA, insulated from the membrane lipidic environment by embedding within a 26 strand β-barrel formed by MtrB. MtrAB forms an intimate connection with an extracellular 10-heme cytochrome, MtrC, which presents its hemes across a large surface area for electrical contact with extracellular redox partners, including electrodes.

Certain bacterial species have a natural ability to exchange electrons with extracellular redox partners. This behavior allows coupling of catalytic transformations inside bacteria to complementary redox transformations of catalysts and electrodes outside the cell. Electricity generation can be coupled to waste-water remediation. Industrially relevant oxidation reactions can proceed exclusively when electrons are released to anodes. Reduced products such as fuels can be generated when electrons are provided from (photo)cathodes. Rational development of these opportunities and inspiration for novel technologies is underpinned by resolution at the molecular level of pathways supporting electron exchange across bacterial cell envelopes. This chapter describes methods for purification, engineering, and in vitro characterization of proteins providing the primary route for electron transport across the outer membrane lipid bilayer of Shewanella oneidensis MR-1, a well-described electrogenic bacterium and chassis organism for related biotechnologies.

Multiheme cytochromes attract much attention for their electron transport properties. These proteins conduct electrons across bacterial cell walls, along extracellular filaments, and when purified can serve as bionanoelectronic junctions. Thus, it is important and necessary to identify and understand the factors governing electron transfer in this family of proteins. To this end we have used ultra-fast transient absorbance spectroscopy, to define heme-heme electron transfer dynamics in the representative multiheme cytochrome STC from Shewanella oneidensis in aqueous solution. STC was photo-sensitized by site-selective labelling with a Ru(II)(bipyridine)3 dye and the dynamics of light-driven electron transfer described by a kinetic model corroborated by molecular dynamics simulation and density functional theory calculations. With the dye attached adjacent to STC Heme IV, a rate constant of 87 x 106 s-1 was resolved for Heme IV → Heme III electron transfer. With the dye attached adjacent to STC Heme I, at the opposite terminus of the tetraheme chain, a rate constant of 125 x 106 s-1 was defined for Heme I → Heme II electron transfer. These rates are an order of magnitude faster than previously computed values for unlabeled STC. The Heme III/IV and I/II pairs exemplify the T-shaped heme packing arrangement, prevalent in multiheme cytochromes, whereby the adjacent porphyrin rings lie at 90o with edge-edge (Fe-Fe) distances of ≈6 (11) Å. The results are significant in demonstrating the opportunities for pump-probe spectroscopies to resolve inter-heme electron transfer in Ru-labeled multiheme cytochromes.

Multi-heme cytochrome c (CytC) proteins are key for transferring electrons out of cells, to enable intracellular oxidation to proceed, also in the absence of O2. In these proteins most of the hemes are arranged in a linear array suggesting a facile path for electronic conduction. To test this, we studied solvent free electron transport across two multi-heme CytC-type: MtrF (deca-heme CytC) and STC (tetra-heme CytC). Transport is measured across monolayers of these proteins in solid state configuration between Au electrodes. Both proteins showed 1,000x higher conductance than single heme, or heme-free proteins, but similar to monolayers of conjugated organics. Conductances are found to be temperature-independent (320-80K), suggesting tunneling as the transport mechanism based on present experimental data. This mechanism is consistent with modelling the I-V curves, results of which could be interpreted by having protein-electrode coupling as rate limiting, rather than transport within the proteins.

Multiheme cytochromes possess closely packed redox-active hemes arranged as chains spanning the tertiary structure. Here we describe five variants of a representative multiheme cytochrome engineered as biohybrid phototransducers for converting light into electricity. Each variant possesses a single Cys sulfhydryl group near a terminus of the heme chain, and this was efficiently labelled with a RuII (2,2'-bipyridine)3 photosensitiser. When irradiated in the presence of a sacrificial electron donor (SED) the proteins exhibited different types of behaviour. Certain proteins were rapidly and fully reduced. Other proteins were rapidly semi-reduced but resisted complete photoreduction. These findings reveal that photosensitised multiheme cytochromes can be engineered to act as resistors, with intrinsic regulation of light-driven electron accumulation, and also as molecular wires with essentially unhindered photoreduction. It is proposed that the observed behaviour arises from interplay between the site of electron injection and the distribution of heme reduction potentials along the heme chain.