The spatial and temporal variation of organochlorine pesticides (OCs) in air across Mexico was investigated by deploying passive samplers at eleven stations across the country during 2005-2006. Integrated samples were taken over three-month periods and quantified for DDT compounds, endosulfans, toxaphenes, components of technical chlordane, hexachlorocyclohexanes (HCHs), and dieldrin. Enantiomers of chiral chlordanes and o,p'-DDT were determined on chiral stationary phase columns as an indicator of source and age. Results are discussed in combination with pumped air samples taken at four other stations in southern Mexico during 2002-2004. DDT and its metabolites, endosulfan and toxaphene were the most abundant OCs detected in all sampling sites. Atmospheric concentrations of SigmaDDT (p,p'-DDT + o,p'-DDT + p,p'-DDE + o,p'-DDE + p,p'-DDD + o,p'-DDD) ranged from 15 to 2360 pg m(-3) with the highest concentrations found in southern Mexico and the lowest found in northern and central Mexico. A fresher DDT residue was observed at sites with greater DDT use and in the southern part of the country, as shown from the higher FDDTe = p,p'-DDT/(p,p'-DDT + p,p'-DDE) and nearly racemic o,p'-DDT. This agrees with the former heavy use of DDT in the endemic malarious area of the country. A local hotspot of endosulfan was identified at an agricultural area in Mazatlan, Sinaloa, with a annual mean concentration of SigmaENDO (endosulfans I + II + endosulfan sulfate) = 26,800 pg m(-3). At this site, higher concentrations of SigmaENDO were recorded during the winter (November to February) and spring (February to May) periods. From back trajectory analysis, this coincides with a shift in the air mass coming from the Pacific Ocean (May to November) to the inland agricultural area (November to May). The elevated SigmaENDO observed is likely due to the local agricultural usage. HCHs, chlordanes, transnonachlors, and dieldrin were more evenly distributed across the country likely due to them being aged residues and more diffuse in the environment. In contrast, hotspots of endosulfans, DDTs, and toxaphenes were observed as they were heavily used in localized agricultural or malarious regions of Mexico.

Histidine phosphorylation plays a key role in prokaryotic signaling and accounts for approximately 6% of the protein phosphorylation events in eukaryotics. Phosphohistidines generally act as intermediates in the transfer of phosphate groups from donor to acceptor molecules. Examples include the bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS) and the histidine kinases found in two-component signal transduction pathways. The latter are utilized by bacteria and plants to sense and adapt to changing environmental conditions. Despite the importance of histidine phosphorylation in two-component signaling systems, relatively few proteins have so far been identified as containing phosphorylated histidine residues. This is largely due to the instability of phosphohistidines, which, unlike the phosphoesters formed by serine, threonine, and tyrosine, are labile and susceptible to acid hydrolysis. Nevertheless, it is possible to preserve and identify phosphorylated histidine residues in target proteins using appropriate sample preparation, affinity purification, and mass spectrometric techniques. This chapter provides a brief overview of such techniques, describes their use in confirming histidine phosphorylation of a known PTS protein (HPr), and suggests how this approach might be adapted for large-scale identification of histidinephosphorylated proteins in two-component systems.[27]identification of histidine phosphorylations 549

[Introducción]: La movilidad urbana actual está produciendo una serie de conflictos ambientales advertidos a nivel global; la mayor parte están vinculados al uso de transporte motorizado, responsable del consumo energético, la fragmentación y ocupación del territorio por la construcción de vialidades, además de contaminación acústica y atmosférica. La calidad del aire es monitoreada en algunas ciudades del mundo, pero en América Latina y en particular en México, el número de ciudades atentas a esta afectación ambiental se reduce; mientras que los impactos negativos a la salud humana y a los ecosistemas aumentan. La falta de datos respecto a la calidad del aire se debe a la complejidad de los métodos de monitoreo y a los costos en su aplicación. [Objetivo]: En esta publicación se presenta una metodología formulada para cuantificar las emisiones de algunos contaminantes criterio y precursores (CO, NOx, SO2, COV, PM10 y PM2.5) producidos por el parque vehicular que circula en la zona metropolitana de San Luis Potosí, México, [Metodología]: a partir del análisis del reparto modal de los viajes cotidianos de la población, del análisis de la actividad vehicular y del cálculo de emisiones utilizando el modelo MOVES. [Conclusiones]: Identificando que la movilidad motorizada contribuye con el 56 % de las emisiones de contaminantes criterio y precursores generados por las fuentes móviles identificadas, por lo que es importante dar seguimiento al análisis de la calidad del aire, hacer un uso racional del automóvil e impulsar políticas de monitoreo, control y minimización de la contaminación atmosférica.