Initial results for urban metal distributions in house dusts of syracuse,New York,USA

A program of house dust sample collection and analysis has begun in Syracuse, New York, USA, in order to determine the feasibility of a geography-based exposure assessment for urban metals. The sampling program, and the protocols it employs, is described for two different types of wipe media, Ghost Wipes and Whatman Filters. Preliminary results show that strong spatial patterns of floor dust loading (mg dust per square foot) can be observed for data aggregated at a spatial scale of about 1600 m (～2.5 km²). Floor dust metal concentrations were similar to those found in other urban environments, with some regional variation. The median floor dust Pb concentration was ～108 mg · kg^?1 for this initial data set of ～264 sampled residential locations, and varied from 50 to 1100 mg Pb · kg^?1.     

Production of Diamino propionic acid ammonia lyase by a new strain of Salmonella typhimurium PU011

Background  

Seeds of the legume plant Lathyrus sativus, which is grown in arid and semi arid tropical regions, contain Diamino Propionic acid (DAP). DAP is a neurotoxin, which, when consumed, causes a disease called Lathyrism. Lathryrism may manifest as Neurolathyrism or Osteolathyrism, in which the nervous system, and bone formation respectively, are affected. DAP ammonia lyase is produced by a few microorganisms such as Salmonella typhi, Salmonella typhimurium and Pseudomonas, and is capable of detoxifying DAP.     

Functional and structural conservation in the mechanosensitive channel MscL implicates elements crucial for mechanosensation

mscL encodes a channel in Escherichia coli that is opened by membrane stretch force, probably serving as an osmotic gauge. Sequences more or less similar to mscL are found in other bacteria, but the degree of conserved function has been unclear. We subcloned and expressed these putative homologues in E . coli and examined their products under patch clamp. Here, we show that each indeed encodes a conserved mechanosensitive channel activity, consistent with the interpretation that this is an important and primary function of the protein in a wide range of bacteria. Although similar, channels of different bacteria differ in kinetics and their degree of mechanosensitivity. Comparison of the primary sequence of these proteins reveals two highly conserved regions, corresponding to domains previously shown to be important for the function of the wild-type E . coli channel, and a C-terminal region that is not conserved in all species. This structural conservation is providing insight into regions of this molecule that are vital to its role as a mechanosensitive channel and may have broader implications for the understanding of other mechanosensitive systems.     

Structural studies of hydroxycitrates and their relevance to certain enzymatic mechanisms.

The crystal structures of the ethylenediamine salts of two diastereoisomeric hydroxycitratesy are described, and their conformations in the solid state are analyzed. In both structures, the HOCCOH torsion angle is approximately 60 ° as found for many tartrates and mesotartrates. The presence of three carboxyl groups and two hydroxyl groups in hydroxycitrates leads to 10 possible types of tridentate metal chelates. Since bacterial citrate lyase and ATP citrate lyase require metal ions, the possible geometries of hydroxycitrate chelation have been compared with those of citrate, and as a result, some information on the geometry of each enzymic active site has been obtained. If the hydroxycitrate binds in the same manner as citrate, the C(3)&;z.sbnd;C(4) bond will be in the correct position to be cleaved. Other modes of binding of hydroxycitrate, if they can be accommodated in the active site of the enzyme, are nonproductive and compete with the citrate-like mode causing inhibition. It is possible, in these alternate modes of binding of hydroxycitrates, for additional binding to side chains in the active site of the enzyme to occur, resulting in extremely potent inhibition.     

Stereochemistry of chapliatrin and its congeners from Liatris gracilis

Re-examination of Liatris gracilis afforded the known sesquiterpene lactones chapliatrin, isochapliatrin, acetlisochapliatrin, five new closely related 5,10-epoxygermacranolides and a new eudesmanolide. The stereochemistry of the 5,10-epoxygermacranolides has been settled by an X-ray analysis of isochapliatrin.