The relative contributions of eight nitrated aromatic compounds (NACs: nitrophenols and nitrated salicylic acids) to the light absorption of aqueous particle extracts and particulate brown carbon were determined from aerosol particle samples collected in Germany and China. High-volume filter samples were collected during six campaigns, performed at five locations in two seasons: (I) two campaigns with strong influence of biomass-burning (BB) aerosol at the TROPOS institute (winter, 2014, urban background, Leipzig, Germany) and the Melpitz research site (winter, 2014, rural background); (II) two campaigns with strong influence from biogenic emissions at Melpitz (summer, 2014) and the forest site Waldstein (summer, 2014, Fichtelgebirge, Germany); and (III) two CAREBeijing-NCP campaigns at Xianghe (summer, 2013, anthropogenic polluted background) and Wangdu (summer, 2014, anthropogenic polluted background with a distinct BB episode), both in the North China Plain. The filter samples were analyzed for NAC concentrations and the light absorption of aqueous filter extracts was determined. Light absorption properties of particulate brown carbon were derived from a seven-wavelength aethalometer during the campaigns at TROPOS (winter) and Waldstein (summer). The light absorption of the aqueous filter extracts was found to be pH dependent, with larger values at higher pH. In general, the aqueous light absorption coefficient (Abs₃₇₀) ranged from 0.21 to 21.8 Mm⁻¹ under acidic conditions and 0.63 to 27.2 Mm⁻¹ under alkaline conditions, over all campaigns. The observed mass absorption efficiency (MAE₃₇₀) was in a range of 0.10–1.79 m² g⁻¹ and 0.24–2.57 m² g⁻¹ for acidic and alkaline conditions, respectively. For MAE₃₇₀ and Abs₃₇₀, the observed values were higher in winter than in summer, in agreement with other studies. The lowest MAE was observed for the Waldstein (summer) campaign (average of 0.17 ± 0.03 m² g⁻¹), indicating that freshly emitted biogenic aerosols are only weakly absorbing. In contrast, a strong relationship was found between the light absorption properties and the concentrations of levoglucosan, corroborating findings from other studies. Regarding the particulate light absorption at 370 nm, a mean particulate light absorption coefficient b_abs, 370 of 54 Mm⁻¹ and 6.0 Mm⁻¹ was determined for the TROPOS (winter) and Waldstein (summer) campaigns, respectively, with average contributions of particulate brown carbon to b_abs, 370 of 46 % at TROPOS (winter) and 15 % at Waldstein (summer). Thus, the aethalometer measurements support the findings from aqueous filter extracts of only weakly absorbing biogenic aerosols in comparison to the more polluted and BB influenced aerosol at TROPOS (winter). The mean contribution of NACs to the aqueous extract light absorption over all campaigns ranged from 0.10 to 1.25 % under acidic conditions and 0.13 to 3.71 % under alkaline conditions. The high variability among the measurement sites showed that the emission strengths of light-absorbing compounds and the composition of brown carbon were very different for each site. The mean contribution of NACs to the particulate brown carbon light absorption was 0.10 ± 0.06 % (acidic conditions) and 0.13 ± 0.09 % (alkaline conditions) during the Waldstein (summer) campaign and 0.25 ± 0.21 % (acidic conditions) and 1.13 ± 1.03 % (alkaline conditions) during the TROPOS (winter) campaign. The average contribution of NACs to the aqueous extract light absorption over all campaigns was found to be 5 times higher than their mass contribution to water-soluble organic carbon indicating that even small amounts of light-absorbing compounds can have a disproportionately high impact on the light absorption properties of particles.

The ability of unevolved amino acid sequences to become biological catalysts was key to the emergence of life on Earth. However, billions of years of evolution separate complex modern enzymes from their simpler early ancestors. To probe how unevolved sequences can develop new functions, we use ultrahigh-throughput droplet microfluidics to screen for phosphoesterase activity amidst a library of more than one million sequences based on a de novo designed 4-helix bundle. Characterization of hits revealed that acquisition of function involved a large jump in sequence space enriching for truncations that removed >40% of the protein chain. Biophysical characterization of a catalytically active truncated protein revealed that it dimerizes into an α-helical structure, with the gain of function accompanied by increased structural dynamics. The identified phosphodiesterase is a manganese-dependent metalloenzyme that hydrolyses a range of phosphodiesters. It is most active towards cyclic AMP, with a rate acceleration of ~10⁹ and a catalytic proficiency of >10¹⁴ M⁻¹, comparable to larger enzymes shaped by billions of years of evolution.

Life as we know it would not exist without the ability of protein sequences to bind metal ions. Transition metals, in particular, play essential roles in a wide range of structural and catalytic functions. The ubiquitous occurrence of metalloproteins in all organisms leads one to ask whether metal binding is an evolved trait that occurred only rarely in ancestral sequences, or alternatively, whether it is an innate property of amino acid sequences, occurring frequently in unevolved sequence space. To address this question, we studied 52 proteins from a combinatorial library of novel sequences designed to fold into 4-helix bundles. Although these sequences were neither designed nor evolved to bind metals, the majority of them have innate tendencies to bind the transition metals copper, cobalt, and zinc with high nanomolar to low-micromolar affinity.

Modulation-format and bit-rate awareness is realized in DLI-based OSNR monitor using pilot-tones. The autonomous signal quality decisions are made even in presence of modulation-dependent cross-talk. This capability facilitates scalable cross-layer impairment-aware-routing in mixed-signal environments.