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Evolution of lowest singlet and triplet excited states with number of thienyl rings in platinum poly-ynesWe present a joint experimental and theoretical investigation of the electronic excitations in transition metal-containing phenylene ethynylenes. The influence of the metal on the nature of the lowest singlet and triplet excited states is characterized. We find that conjugation occurs through the metal sites, which deeply modifies the optical properties of the conjugated chains. We also analyze the chain-length dependence of the singlet-singlet, S 0 →S 1 , singlet-triplet, S 0 →T 1 , and triplet-triplet, T 1 →T n , transition energies; both experimental data and theoretical results indicate that the lowest triplet exciton, T 1 , is strongly localized on a single phenylene ring while the S 1 and T n states extend over a few repeating units. Finally, we estimate the geometric relaxation phenomena occurring in the lowest excited states and perform a Huang-Rhys analysis of the triplet emission spectrum in model systems.

Avian H7N9 influenza viruses are group 2 influenza A viruses that have been identified as the etiologic agent for a current major outbreak that began in China in 2013 and may pose a pandemic threat. Here, we examined the human H7-reactive antibody response in 75 recipients of a monovalent inactivated A/Shanghai/02/2013 H7N9 vaccine. After 2 doses of vaccine, the majority of donors had memory B cells that secreted IgGs specific for H7 HA, with dominant responses against single HA subtypes, although frequencies of H7-reactive B cells ranged widely between donors. We isolated 12 naturally occurring mAbs with low half-maximal effective concentrations for binding, 5 of which possessed neutralizing and HA-inhibiting activities. The 5 neutralizing mAbs exhibited narrow breadth of reactivity with influenza H7 strains. Epitope-mapping studies using neutralization escape mutant analysis, deuterium exchange mass spectrometry, and x-ray crystallography revealed that these neutralizing mAbs bind near the receptor-binding pocket on HA. All 5 neutralizing mAbs possessed low numbers of somatic mutations, suggesting the clones arose from naive B cells. The most potent mAb, H7.167, was tested as a prophylactic treatment in a mouse intranasal virus challenge study, and systemic administration of the mAb markedly reduced viral lung titers.

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18SARS-CoV-2 emerged in late 2019, leading to the COVID-19 pandemic that continues to 19 cause significant global mortality in human populations. Given its sequence similarity to CoV, as well as related coronaviruses circulating in bats, SARS-CoV-2 is thought to have 21 originated in Chiroptera species in China. However, whether the virus spread directly to 22 humans or through an intermediate host is currently unclear, as is the potential for this virus 23to infect companion animals, livestock and wildlife that could act as viral reservoirs. Using a 24 combination of surrogate entry assays and live virus we demonstrate that, in addition to human 25 ACE2, the Spike glycoprotein of SARS-CoV-2 has a broad host tropism for mammalian ACE2 26 receptors, despite divergence in the amino acids at the Spike receptor binding site on these 27proteins. Of the twenty-two different hosts we investigated, ACE2 proteins from dog, cat and 28 rabbit were the most permissive to SARS-CoV-2, while bat and bird ACE2 proteins were the 29 least efficiently used receptors. The absence of a significant tropism for any of the three 30 genetically distinct bat ACE2 proteins we examined indicates that SARS-CoV-2 receptor 31 usage likely shifted during zoonotic transmission from bats into people, possibly in an 32 intermediate reservoir. Interestingly, while SARS-CoV-2 pseudoparticle entry was inefficient 33in cells bearing the ACE2 receptor from bats or birds the live virus was still able to enter these 34 cells, albeit with markedly lower efficiency. The apparently broad tropism of SARS-CoV-2 at 35 the point of viral entry confirms the potential risk of infection to a wide range of companion 36 animals, livestock and wildlife. 37 38Introduction 39 40The β-coronavirus SARS-CoV-2 emerged in late 2019, causing a large epidemic of respiratory 41 disease in the Hubei province of China, centred in the city of Wuhan [1]. Subsequent 42 international spread has led to an ongoing global pandemic, currently responsible for 8 million 43 infections and over 435,000 deaths (as of 11 th June 2020, John Hopkins University statistics; 44 https://coronavirus.jhu.edu/map.html). As for SARS-CoV, which emerged in China in late 45 2002, and MERS-CoV, which emerged in Saudi Arabia in 2012, the original animal reservoir 46 of zoonotic coronaviruses is thought to be bats [2]. Spill-over into humans is suspected or 47 proven to be facilitated through an intermediate host, e.g. civets for SARS-CoV [2] or camels 48 for MERS-CoV [3]. For SARS-CoV-2, a bat origin is supported by the 2013 identification of a 49 related coronavirus RaTG13 from Rhinolophus affinis (intermediate horseshoe bat), which is 50 96% identical at the genome level to SARS-CoV-2 [1]. Identifying the animal reservoir of 51 SARS-CoV-2, and any intermediate hosts via which the virus ultimately spread to humans, 52 may help to understand how, where and when this virus spilled over into people. This 53information could be vital in identifying future risk and preventing subsequent outbreaks of 54 both re...