A Balance between Transmembrane-Mediated ER/Golgi Retention and Forward Trafficking Signals in Glycophorin-Anion Exchanger-1 Interaction.

Anion exchanger-1 (AE1) is the main erythroid Cl-/HCO3- transporter that supports CO2 transport. Glycophorin A (GPA), a component of the AE1 complexes, facilitates AE1 expression and anion transport, but Glycophorin B (GPB) does not. Here, we dissected the structural components of GPA/GPB involved in glycophorin-AE1 trafficking by comparing them with three GPB variants-GPBhead (lacking the transmembrane domain [TMD]), GPBtail (mainly the TMD), and GP.Mur (glycophorin B-A-B hybrid). GPB-derived GP.Mur bears an O-glycopeptide that encompasses the R18 epitope, which is present in GPA but not GPB. By flow cytometry, AE1 expression in the control erythrocytes increased with the GPA-R18 expression; GYP.Mur+/+ erythrocytes bearing both GP.Mur and GPA expressed more R18 epitopes and more AE1 proteins. In contrast, heterologously expressed GPBtail and GPB were predominantly localized in the Golgi apparatus of HEK-293 cells, whereas GBhead was diffuse throughout the cytosol, suggesting that glycophorin transmembrane encoded an ER/Golgi retention signal. AE1 coexpression could reduce the ER/Golgi retention of GPB, but not of GPBtail or GPBhead. Thus, there are forward-trafficking and transmembrane-driven ER/Golgi retention signals encoded in the glycophorin sequences. How the balance between these opposite trafficking signals could affect glycophorin sorting into AE1 complexes and influence erythroid anion transport remains to be explored.

[Study on greenhouse gas emissions from urban waste disposal system: a case study in Xiamen].

Waste disposal is one of the sources of greenhouse gas (GHG) emissions from urban human activities. According to the method recommended by IPCC Guidelines for National Greenhouse Gas Inventories 2006, a calculation model was established to assess GHG emissions of waste disposal in Xiamen. Then GHG emissions from waste disposal in Xiamen during the year of 2005-2010 were estimated, including solid waste landfill, solid waste incineration and wastewater treatment. The results showed that total GHG emissions quantified in carbon dioxide equivalents (CO2e) from waste disposal was 406.3 kt in 2005, and increased to 704.6 kt in 2010. Because of the improvement of wastewater treatment process and rapid increasing municipal solid waste (MSW), the main source of emissions was from wastewater treatment turning to solid waste landfill. GHG emissions from solid waste landfill accounted for about 90% of total emissions from solid waste disposal process in 2005, and the proportion decreased to 75% in 2010. GHG emissions (quantified in CO2e) from waste water treatment reached the highest value 325.5 kt in 2007. Chemical raw materials and chemical industry have been the highest CH4 emission industry during 2005-2010, which accounted for more than 55% of total CH4 emission from industrial wastewater treatment.

[Urban sustainability assessment based on eco-efficiency and its application].

Comprehensive assessment on urban ecological system is one of important issues for regional sustainable development research. Urban eco-efficiency is the effective tool to integrate sustainabable strategies into the development planning and management initiatives, which expresses the relationship of inputs of ecological impact and outputs of social welfare. An evaluation model of urban sustainability based on eco-efficiency was proposed by integrating Ecological Footprint model and Human Development Index. Using this model, a case study of Xiamen City was carried out using the statistical data from 2000 to 2006. There is a fluctuation of ecoefficiency which showed a steady increase first, then a sharp decline and a marginal increase towards the end. During 2000-2006, the per-capita ecological footprint increases from 4.279 hm2 to 5.462 hm2; and the Human Development Index increases from 0.831 to 0.896; thus the eco-efficiency, resource efficiency and environmental efficiency declines by 15.5%, 15.7% and 15.3% respectively. Xiamen experiences sustainability hypo-increasing phase first, sustainability increasing phase secondly, then sustainability decreasing phase, and sustainability increasing phase in the end. On the whole, the urban sustainability shows a decreasing trend.