Attached is the manuscript of our Open Commentary en i led The environmental dangers of employing single-use face masks as part of a COVID-19 exit strategy hich my co-authors and I would like to submit for publication in the journal UCL Open: Environment. We, the authors of this paper, are a multidisciplinary group of academics including chemists, materials scientists, engineers, designers, artists, and social scientists from University College London. We are part of the UCL Plastic Waste Innovation Hub whose aim is to develop new ways of designing-out waste from plastic packaging (https://www.plasticwastehub.org.uk). In this Open Commentary we are responding to the current situation in the UK where the general population is under lockdown measures as a result of the COVID-19 pandemic. Without an available vaccine the government is considering different policy options to enable the restoration of freedom of movement and to restart the economy. One measure being considered by many countries is the mandatory wearing of face masks by the general population. This is due to a growing body of evidence to suggest that even basic face masks can be effective in reducing the spread of the virus, by reducing the range and volume of exhaled water droplets containing SARS-CoV-2. Although the World Health Organisation (WHO) does not currently recommend this measure as a means of preventing the spread of COVID-19, a growing number of countries have been adopting this precautionary measure including China, South Korea, Germany, Scotland, Spain amongst many others. In the UK due to shortages of PPE to supply to front-line workers in the hospitals and care homes, there is reluctance to adopt this measure in case this intensifies the shortage of PPE. If and when such PPE shortages abate there may be growing pressure to adopt this precautionary measure. The aim of this paper is to examine the environmental impact of the UK adopting masks for the general population in particular the amount of contaminated plastic waste produced. We conclude that if the government decides to require the wearing of face masks in public, it should mandate reusable masks and not single-use masks. This will preserve single-use mask supplies for front-line healthcare workers, and reduce the environmental risks associated with the disposal of 66,000 tonnes of contaminated plastic mask waste in the household waste stream. Additionally, the use of reusable masks by the general population would significantly reduce plastic waste and the climate change impact of this policy measure. The methodology of the paper is applicable to the analysis of other countries whose use of single-use masks is also likely to be an important environmental issue for the next 12 months.

Chiral auxiliary methodology and chiral assays have been developed to establish the enantiomeric purities of erythrulose and 1,3-dihydroxypentan-2-one generated using wild-type (WT) Escherichia coli transketolase (TK). l-Erythrulose was formed in 95% ee and (3S)-1,3-dihydroxypentan-2-one in 58% ee. Since the latter compound was formed in moderate ee, TK libraries were screened to identify higher performing mutants. A colorimetric screen and chiral assay were successfully applied to a 96-well format, and new active TK mutants were identified, which gave 1,3-dihydroxypentan-2-one in high stereoselectivities. Remarkably, activesite single-point mutants were identified that were able to both enhance and reverse the stereoselectivity of TK.

Pictet-Spenglerases provide a key role in the biosynthesis of many biologically-active alkaloids. There is increasing use of these biocatalysts as an alternative to traditional organic synthetic methods as they provide stereoselective and regioselective control under mild conditions. Products from these enzymes also contain privileged drug scaffolds (such as tetrahydroisoquinoline or b-carboline moieties), so there is interest in the characterisation and use of these enzymes as versatile biocatalysts to synthesize analogues of the corresponding natural products for drug discovery. This review discusses all known Pictet-Spenglerase enzymes and their applications as biocatalysts.

During the coronavirus (COVID-19) pandemic, the UK government mandated the use of face masks in various public settings and recommended the use of reusable masks to combat shortages of medically graded single-use masks in healthcare. To assist decision-making on the choice of masks for future pandemics, where shortages may not be a contributing factor, the University College London (UCL) Plastic Waste Innovation Hub has carried out a multidisciplinary comparison between single-use and reusable masks based on their anatomy, standalone effectiveness, behavioural considerations, environmental impact and costs. Although current single-use masks have a higher standalone effectiveness against bacteria and viruses, studies show that reusable masks have adequate performance in slowing infection rates of respiratory viruses. Material flow analysis (MFA), life cycle assessment (LCA) and cost comparison show that reusable masks have a lower environmental and economic impact than single-use masks. If every person in the UK uses one single-use mask each day for a year, it will create a total of 124,000 tonnes of waste, 66,000 tonnes of which would be unrecyclable contaminated plastic waste (the masks), with the rest being the recyclable packaging typically used for transportation and distribution of masks. Using reusable masks creates >85% less waste, generates 3.5 times lower impact on climate change and incurs 3.7 times lower costs. Further behavioural research is necessary to understand the extent and current practices of mask use; and how these practices affect mask effectiveness in reducing infection rates. Wearing single-use masks may be preferred over reusable masks due to perceptions of increased hygiene and convenience. Understanding behaviour towards the regular machine-washing of reusable masks for their effective reuse is key to maximise their public health benefits and minimise environmental and economic costs.

The tetrahydroisoquinoline (THIQ) ring system is present in a large variety of structurally diverse natural products exhibiting a wide range of biological activities. Routes to mimic the biosynthetic pathways to such alkaloids, by building cascade reactions in vitro, represents a successful strategy and can offer better stereoselectivities than traditional synthetic methods. S‐Adenosylmethionine (SAM)‐dependent methyltransferases are crucial in the biosynthesis and diversification of THIQs; however, their application is often limited in vitro by the high cost of SAM and low substrate scope. In this study, we describe the use of methyltransferases in vitro in multi‐enzyme cascades, including for the generation of SAM in situ. Up to seven enzymes were used for the regioselective diversification of natural and non‐natural THIQs on an enzymatic preparative scale. Regioselectivites of the methyltransferases were dependent on the group at C‐1 and presence of fluorine in the THIQs. An interesting dual activity was also discovered for the catechol methyltransferases used, which were found to be able to regioselectively methylate two different catechols in a single molecule.