Controlled levels of protein modification through a chromatography-mediated bioconjugation.

Synthetically modified proteins are increasingly finding applications as well-defined scaffolds for materials. In practice it remains difficult to construct bioconjugates with precise levels of modification because of the limited number of repeated functional groups on proteins. This article describes a method to control the level of protein modification in cases where there exist multiple potential modification sites. A protein is first tagged with a handle using any of a variety of modification chemistries. This handle is used to isolate proteins with a particular number of modifications via affinity chromatography, and then the handle is elaborated with a desired moiety using an oxidative coupling reaction. This method results in a sample of protein with a well-defined number of modifications, and we find it particularly applicable to systems like protein homomultimers in which there is no way to discern between chemically identical subunits. We demonstrate the use of this method in the construction of a protein-templated light-harvesting mimic, a type of system which has historically been difficult to make in a well-defined manner

Short-Term Dissolved Organic Carbon Dynamics Reflect Tidal, Water Management, and Precipitation Patterns in a Subtropical Estuary

Estuaries significantly impact the global carbon cycle by regulating the exchange of organic matter, primarily in the form of dissolved organic carbon (DOC), between terrestrial and marine carbon pools. Estuarine DOC dynamics are complex as tides and other hydrological and climatic drivers can affect carbon fluxes on short and long time scales. While estuarine and coastal DOC dynamics have been well-studied, variations on short time scales are less well-constrained. Recent advancements in sonde technology enable autonomous in situ collection of high frequency DOC data using fluorescent dissolved organic matter (FDOM) as a proxy, dramatically improving our capacity to characterize rapid changes in DOC, even in remote ecosystems. This study utilizes high-frequency FDOM measurements to untangle rapid and complex hydrologic drivers of DOC in the Shark River estuary, the main drainage of Everglades National Park, Florida. Non-conservative mixing of FDOM along the salinity gradient suggested mangrove inputs accounted for 6% of the total DOC pool. Average changes in FDOM concentrations through individual tidal cycles ranged from less than 10% to greater than 50% and multi-day trends \u3e100% change in FDOM concentration were observed. Salinity and water level both inversely correlated to FDOM at sub-hourly and daily resolutions, while freshwater controls via precipitation and water management were observed at diel to monthly time-scales. In particular, the role of water management in rapidly shifting estuarine salinity gradients and DOC export regimes at sub-weekly time-scales was evident. Additionally, sub-hourly spikes in ebb tide FDOM indicated rapid exchange of DOC between mangrove sediments and the river channel. DOC fluxes calculated from high-resolution FDOM measurements were compared to monthly DOC measurements with high-resolution fluxes considerably improving accuracy of fluxes (thereby constraining carbon budgets). This study provides a better understanding of short-term DOC dynamics and associated hydrological drivers and indicates the importance of high-frequency measurements to accurately constrain coastal carbon processes and budgets, particularly in coastal systems increasingly altered by hydrologic restoration and climate change

Characterization of dissolved organic matter from a restored urban marsh and its role in the mobilization of trace metals

Dissolved organic matter (DOM), although highly variable and not very well characterized, plays a role in many important environmental reaction and transport processes, including trace metal mobilization. This study characterizes heterogeneous DOM from the pore-water of a restored urban tidal marsh, using chemical, optical, and electrochemical methods for dissolved organic carbon/nitrogen ratios (C:N: 1.8–6.4), spectroscopic characteristics (decreased aromaticity in amended sediments), element ratios (maximum sediment-associated trace metal concentrations measured Pb: 9.5 ± 0.1 > Cr: 7.3 ± 0.1 > Cu: 5.07 ± 0.53), all as a function of sediment depth. Specific DOM properties from the restored marsh were then compared to pore-water samples from a natural marsh and a simulated wetland microcosm which resulted in similar values, while the reference humic acid significantly differed in properties from field DOM. The results revealed that reference humic acids do not accurately represent the complexity of natural heterogeneous DOM, whereas a simulated wetland microcosm may provide a reasonable representation of natural DOM. Clear differences between amended and original soil (transition below 30 cm) were observed in DOM and trace metal properties including: lower DOM content, higher log Kc values, less DOM complexity, development of a iron-sulfide redox buffering pool, and greater affinity for metals in the solid phase occurring in the amended sediments

Precipitation of copper (II) in a two-stage continuous treatment system using sulfate reducing bacteria

Biologically driven precipitation of dissolved copper and other trace metals has been used to treat contaminated aqueous streams. However, high dissolved trace metal concentrations can lead to toxicity, and their bioremediation difficult. Furthermore sorption of trace metals onto biomass might result in large amounts of contaminated byproducts. The aim of this work was to develop and test a two-stage reactor to bypass the toxic effects on the bacteria and chemically precipitate copper without contaminating the bulk of the biomass. Hence, copper removal using a sulfate reducing bacteria culture was investigated in a two-stage continuous treatment system. The first reactor was a sand-filled biological reactor in which the sulfate is reduced, followed by a second reactor/clarifier where the chemical precipitation and sedimentation of a CuS phase occurs. The influent Cu2+ concentration was varied systematically between 15 and 600 mg/L, and the precipitation of Cu2+ metal as CuS was achieved in the second reactor, resulting in complete (within detection limits) Cu2+ removal. EDS analysis on the solid phase collected from the second reactor confirmed the presence of Cu and S in the precipitate. EDS analysis on the solid phase collected from the second reactor confirmed the presence of Cu and S in the precipitate, and a CuS phase with minimal biomass was obtained. This configuration avoids toxicity effects of heavy metals in the biological reactor, as well as the contamination of biomass with the trace metal. Furthermore, the biomass free CuS precipitates can be easily disposed or even used to recover the trace metal

Establishing Canada\u27s First Integrated Domestic Violence Court: Exploring Process, Outcomes, and Lessons Learned

The establishment of domestic violence courts has resulted in significant improvements in responses to family violence, but these courts have generally dealt only with criminal cases and do not address the risks that the victim and children may face in family proceedings. In some locations in the USA, courts have been established to deal with both criminal and family proceedings that arise from a domestic violence situation. This paper describes and analyzes the establishment of the first court in Canada that hears both criminal and family cases concerning families where there are domestic violence issues. The authors report on a study of the views and experiences of 21 stakeholders (judges, Crown, criminal and family lawyers, community supports, victims, and offenders) involved in the Integrated Domestic Violence Court in Toronto. The participants generally report that the Court provides a better approach to dealing with domestic violence post separation, though there are some concerns expressed about its operations, especially by lawyers representing alleged abusers. The Integrated Domestic Violence Court is a promising example of how systems can collaborate to better protect victims and advance the interests of children

‘Race’ and inequality in postcolonial urban settings Examples from Peru, Jamaica, and Indonesia

In this essay we present three case studies of Peru, Jamaica and Indonesia to illustrate the use of the concept of race in daily life in relation to labour, popular culture and beauty respectively. These cases demonstrate how the use of the concept of race changes in the transition from a colonial into a postcolonial setting, depending on the role of the state and nation building. In Peru, we see a clear continuation of racialized thinking; thinking and speaking in terms of ‘race’ is still the norm. In Jamaica we find a process of inversion: the concept of race is maintained as a frame of societal analysis, but blackness is revalidated and has become a prerequisite for national and cultural belonging. In Indonesia racialized categorizations have disappeared almost completely as ‘race’ has become subjected to the development rhetoric, which just allows limited space for ethnic manifestations. However, discrimination on other rhetorical basis, such as non-citizenship, remains

Q^2-Dependence of the Proton's G_1 Structure Function Sum Rule

We study the $Q^2$ variation of the first moment of the nucleon's spin-dependent structure function $G_1$. As $Q^2 \rightarrow 0$ the moment is determined by the low energy theorem for Compton scattering. In the deep-inelastic region the moment is calculated using twist expansion to order $1/Q^2$. Based on these limits, we construct a formula which smoothly interpolates between the two regions.Comment: (revised), 8 pages in REVTEX, 1 figure, MIT-CTP-223