Saints and Orphans

Postcard from Brooke Carstensen, during the Linfield College January Term Program in Indi

Effect of charged lipids on the ionization behavior of glutamic acid containing transmembrane helices

Transmembrane proteins make up critical components of living cells. Protein function can be greatly impacted by the charged state of its respective components, the side chains of amino acid residues. Thus far, in the lipid membrane, little is known about the properties of residues such as glutamic acid. To explore these properties, I have included glutamic acid in a suitable model peptide-lipid system for fundamental biophysical experiments. Within the system, I have placed a glutamic acid residue instead of leucine in the L14 position of the helical hydrophobic peptide GWALP23 (acetyl-GGALWLALALALAL14ALALWLAGA-amide). Substitutions of glutamine and aspartic acid serve as controls for the properties of the peptide helix in lipid bilayer membranes. The GWALP23 peptide derivatives are placed in various lipid bilayer environments. Specifically, I investigated the impact of glutamic acid (position E14) when differently charged lipids are present in the bilayer. The underlying importance is to understand the charged or neutral state behavior of glutamic acid under conditions where it is important for the functioning of several types of membrane proteins, such as ion channels, drug transporters and others. For the experimental plan, core alanine resides of GWALP23 were labeled with deuterium to enable detection of helix characteristics by solid-state 2H NMR spectroscopy. The peptide-lipid samples included primarily the neutral lipid DMPC, 1,2-dimyristoylphosphatidylcholine, (with 14-carbon acyl chains), along with 10% of a charged lipid. For each membrane system, I confirmed lipid bilayer formation for the particular peptide-lipid mixture by solid-state 31P NMR. The charged lipids consisted of the negatively charged lipid DMPG, 1,2-dimyristoylphosphatidylglycerol, and the positively charged lipid DMTAP, 1,2-dimyristoyl-3-trimethylammonium-propane. These charged lipids were found to influence the properties of the GWALP23 helix when E14 was present. DMTAP, in particular, improves the 2H NMR spectra and the prospects for characterizing helix dynamics when a glutamic acid residue is present. While some experiments were cut short due to a global emergency, the results show promise for characterizing glutamic acid in model helices and actual membrane proteins

Se Doefel Daner

When the Angles, Saxons and Jutes invaded England during the fifth century, they wiped out the native Celts both physically and linguistically. Except for place-names, only a half-dozen or so Celtic words entered Old English. By the ninth century, with the Celts all but exterminated, the Anglo-Saxons settled down to enjoy the good English life

Performance of the CMS Level-1 Trigger

The first level trigger of the CMS experiment is comprised of custom electronics that process data from the electromagnetic and hadron calorimeters and three technologies of muon detectors in order to select the most interesting events from LHC collisions, such as those consistent with the production and decay of the Higgs boson. The rate of events selected by this Level-1 trigger must be reduced from the beam crossing frequency to no more than 100 kHz further processing can occur, a major challenge since the LHC instantaneous luminosity has increased by six orders of magnitude since the start of operations to more than 6E33 cm-2s-1 today. The performance of the Level-1 trigger, in terms of rates and efficiencies of the main objects and trigger algorithms, as measured from LHC proton collisions at 7 and 8 TeV center-of-mass energies is presented here.Comment: Presented at 36th International Conference on High Energy Physics, July 4-11, 2012, Melbourne, Australi

Hydraulic Fracturing: Yay or Nay?

The Texas Orato

Unaccustomed As I, Unh ...

Ancient calendars were based on the lunar month and the solar year. Because the solar year is not an integral multiple of the lunar month, the months tended to drift through the seasons, and before anyone quite realized it February was the first month of the year instead of March. It was embarrassing to have a spring festival in the middle of a snowstorm, so one of the functions of the high priest was to occasionally insert or intercalate an extra month into a year to bring the seasons back into synchronization