Search for: All records

Type 1 copper (T1Cu) centers are crucial in biological electron transfer (ET) processes, exhibiting a wide range of reduction potentials (E°′T1Cu) to match their redox partners and optimize ET rates. While tuning E°′T1Cu in mononuclear T1Cu proteins like azurin has been successful, it is more difficult for multicopper oxidases. Specifically, while replacing axial methionine to leucine in azurin increased its E°′T1Cu by ~100 mV, the corresponding M298L mutation in small laccase from Streptomyces coelicolor (SLAC) unexpectedly decreased its E°′T1Cu by 12 mV. X-ray crystallography revealed two axial water molecules in M298L-SLAC, leading to the decrease of E°′T1Cu due to decreased hydrophobicity. Structural alignment and molecular dynamics simulation indicated a key difference in T1Cu axial loop position, leading to the different outcome upon methionine to leucine mutation. Based on structural analyses, we introduced additional F195L and I200F mutations, leading to partial removal of axial waters, a 122-mV increase in E°′T1Cu, and a 7-fold increase in kcat/KM from M298L-SLAC. These findings highlight the complexity of tuning E°′T1Cu in multicopper oxidases and provide valuable insights into how structure-based protein engineering can contribute to the broader understanding of T1Cu center, E°′T1Cu and reactivity tuning for applications in solar energy transfer, fuel cells, and bioremediation. 

The impacts of wildfires along the wildland urban interface (WUI) on atmospheric particulate concentrations and composition are an understudied source of air pollution exposure. To assess the residual impacts of the 2021 Marshall Fire (Colorado), a wildfire that predominantly burned homes and other human-made materials, on homes within the fire perimeter that escaped the fire, we performed a combination of fine particulate matter (PM2.5) filter sampling and chemical analysis, indoor dust collection and chemical analysis, community scale PurpleAir PM2.5 analysis, and indoor particle number concentration measurements. Following the fire, the chemical speciation of dust collected in smoke-affected homes in the burned zone showed elevated concentrations of the biomass burning marker levoglucosan (medianlevo = 4147 ng g−1), EPA priority toxic polycyclic aromatic hydrocarbons (median Σ16PAH = 1859.3 ng g−1), and metals (median Σ20Metals = 34.6 mg g−1) when compared to samples collected in homes outside of the burn zone 6 months after the fire. As indoor dust particles are often resuspended and can become airborne, the enhanced concentration of hazardous metals and organics within dust samples may pose a threat to human health. Indoor airborne particulate organic carbon (median = 1.91 μg m−3), particulate elemental carbon (median = .02 μg m−3), and quantified semi-volatile organic species in PM2.5 were found in concentrations comparable to ambient air in urban areas across the USA. Particle number and size distribution analysis at a heavily instrumented supersite home located immediately next to the burned area showed indoor particulates in low concentrations (below 10 μg m−3) across various sizes of PM (12 nm–20 μm), but were elevated by resuspension from human activity, including cleaning. 

The block design test (BDT), in which a person has to recreate a visual design using colored blocks, is notable among cognitive assessments because it makes so much of a person's problem-solving strategy ``visible'' through their ongoing manual actions. While, for decades, numerous pockets of research on the BDT have identified certain behavioral variables as being important for certain cognitive or neurological hypotheses, there is no unifying framework for bringing together this spread of variables and hypotheses. In this paper, we identify 25 independent and dependent variables that have been examined as part of published BDT studies across many areas of cognitive science and present a sample of the research on each one. We also suggest variables of interest for future BDT research, especially as made possible with the advent of advanced recording technologies like wearable eye trackers. 

Abstract The key to type 1 copper (T1Cu) function lies in the fine tuning of the Cu^II/Ireduction potential (E°′_T1Cu) to match those of its redox partners, enabling efficient electron transfer in a wide range of biological systems. While the secondary coordination sphere (SCS) effects have been used to tuneE°′_T1Cuin azurin over a wide range, these principles are yet to be generalized to other T1Cu‐containing proteins to tune catalytic properties. To this end, we have examined the effects of Y229F, V290N and S292F mutations around the T1Cu of small laccase (SLAC) fromStreptomyces coelicolorto match the highE°′_T1Cuof fungal laccases. Using ultraviolet‐visible absorption and electron paramagnetic resonance spectroscopies, together with X‐ray crystallography and redox titrations, we have probed the influence of SCS mutations on the T1Cu and correspondingE°′_T1Cu. While minimal and smallE°′_T1Cuincreases are observed in Y229F‐ and S292F‐SLAC, the V290N mutant exhibits a majorE°′_T1Cuincrease. Moreover, the influence of these mutations onE°′_T1Cuis additive, culminating in a triple mutant Y229F/V290N/S292F‐SLAC with the highestE°′_T1Cuof 556 mV vs. SHE reported to date. Further activity assays indicate that all mutants retain oxygen reduction reaction activity, and display improved catalytic efficiencies (k_cat/K_M) relative to WT‐SLAC.