Oxygen isotopic compositions of silicates in eclogites and whiteschists from the Kokchetav massif were analyzed by whole-grain CO2-laser fluorination methods. Systematic analyses yield extremely low delta(18)O for eclogites, as low as -3.9parts per thousand for garnet; these values are comparable with those reported for the Dabie-Sulu UHP eclogites. Oxygen isotopic compositions are heterogeneous in samples of eclogite, even on an outcrop scale. Schists have rather uniform oxygen isotope values compared to eclogites, and low delta(18)O is not observed. Isotope thermometry indicates that both eclogites and schists achieved high-temperature isotopic equilibration at 500-800 degreesC. This implies that retrograde metamorphic recrystallization barely modified the peak-metamorphic oxygen isotopic signatures. A possible geological environment to account for the low-delta(18)O basaltic protolith is a continental rift, most likely subjected to the conditions of a cold climate. After the basalt interacted with low delta(18)O meteoric water, it was tectonically inserted into the surrounding sedimentary units prior to, or during subduction and UHP metamorphism.

Multiple sulfur isotope system is a powerful new tracer for atmospheric, volcanic, and biological influences on sulfur cycles in the anoxic early Earth. Here, we report high-precision quadruple sulfur isotope analyses (S-32/S-33/S-34/S-36) of barite, pyrite in barite, and sulfides in related hydrothermal and igneous rocks Occurring in the ca. 3.5 Ga Dresser Formation, Western Australia. Our results indicate that observed isotopic variations are mainly controlled by mixing of mass-dependently (MD) and non-mass-dependently fractionated (non-MD) Sulfur reservoirs. Based on the quadruple Sulfur isotope systematics (delta S-34-Delta S-33-Delta S-36) for these minerals, four end-member Sulfur reservoirs have been recognized: (1) non-MD sulfate (delta S-34 = -5 +/- 2%; Delta S-33 = -3 +/- 1%); (2) MD sulfate (delta S-34 = +10 +/- 3%; (3) non-MD sulfur (delta S-34 > +6%; Delta S-33 > +4%); and (4) igneous MD sulfur (delta S-34 = Delta S-33 = 0%. The first and third components show it clear non-MD signatures, thus probably represent Sulfate and sulfur aerosol inputs. The MD sulfate component (2) is enriched in S-34(+10 +/- 3%) and may have originated from microbial and/ or abiotic disproportionation of volcanic S or SO2. Our results reconfirm that the Dresser barites contain small amounts of pyrite depleted in S-34 by 15-22% relative to the host barite. These barite-pyrite pairs exhibit a mass-dependent relationship of delta S-33/delta S-34 with slope less than 0.512, which is consistent with that expected for microbial Sulfate reduction and is significantly different from that of equilibrium fractionation (0.515). The barite-pyrite pairs also show up to 1% difference in Delta S-36 values and steep Delta S-36/Delta S-33 slopes, which deviate from the main Archean array (Delta S-36/Delta S-33 = -0.9) and are comparable to isotope effects exhibited by sulfate reducing microbes (Delta S-36/Delta S-33 = -5 to -11). These new lines of evidence support the existence of sulfate reducers at ca. 3.5 Ga, whereas microbial sulfur disproportionation may have been more limited than recently suggested. (C) 2008 Elsevier Ltd. All rights reserved.

Telomerase is a ribonucleoprotein enzyme responsible for maintaining the telomeric end of the chromosome. The telomerase enzyme requires two main components to function: the telomerase reverse transcriptase (TERT) and the telomerase RNA (TR), which provides the template for telomeric DNA synthesis. TR is a long non-coding RNA, which forms the basis of a large structural scaffold upon which many accessory proteins can bind and form the complete telomerase holoenzyme. These accessory protein interactions are required for telomerase activity and regulation inside cells. The interacting partners of TERT have been well studied in yeast, human, and Tetrahymena models, but not in parasitic protozoa, including clinically relevant human parasites. Here, using the protozoan parasite, Trypanosoma brucei (T. brucei) as a model, we have identified the interactome of T. brucei TERT (TbTERT) using a mass spectrometry-based approach. We identified previously known and unknown interacting factors of TbTERT, highlighting unique features of T. brucei telomerase biology. These unique interactions with TbTERT, suggest mechanistic differences in telomere maintenance between T. brucei and other eukaryotes.