Macquarie University

About: Macquarie University is a education organization based out in Sydney, New South Wales, Australia. It is known for research contribution in the topics: Population & Context (language use). The organization has 14075 authors who have published 47673 publications receiving 1416184 citations. The organization is also known as: Macquarie uni.

Biomarker evidence for green and purple sulphur bacteria in a stratified Palaeoproterozoic sea

Abstract: Rising oxygen levels in the Earth's early atmosphere marked the end of a 2.5-billion-year period dominated by oceans with low levels of oxygen. But geochemical evidence suggests that for the following billion years the oceans remained largely devoid of oxygen. The discovery of molecular fossils (hydrocarbon biomarkers) in 1.6-billion-year-old sedimentary rocks from a marine basin in northern Australia now offers insights into the marine ecosystem at the time. The biomarkers record an anoxic and sulphidic world hostile to to many forms of life but supporting blooms of sulphide-breathing green and purple bacteria. The disappearance of iron formations from the geological record ∼1.8 billion years (Gyr) ago was the consequence of rising oxygen levels in the atmosphere starting 2.45–2.32 Gyr ago1,2,3. It marks the end of a 2.5-Gyr period dominated by anoxic and iron-rich deep oceans. However, despite rising oxygen levels and a concomitant increase in marine sulphate concentration, related to enhanced sulphide oxidation during continental weathering4, the chemistry of the oceans in the following mid-Proterozoic interval (∼1.8–0.8 Gyr ago) probably did not yet resemble our oxygen-rich modern oceans. Recent data5,6,7,8 indicate that marine oxygen and sulphate concentrations may have remained well below current levels during this period, with one model indicating that anoxic and sulphidic marine basins were widespread, and perhaps even globally distributed4. Here we present hydrocarbon biomarkers (molecular fossils) from a 1.64-Gyr-old basin in northern Australia, revealing the ecological structure of mid-Proterozoic marine communities. The biomarkers signify a marine basin with anoxic, sulphidic, sulphate-poor and permanently stratified deep waters, hostile to eukaryotic algae. Phototrophic purple sulphur bacteria (Chromatiaceae) were detected in the geological record based on the new carotenoid biomarker okenane, and they seem to have co-existed with communities of green sulphur bacteria (Chlorobiaceae). Collectively, the biomarkers support mounting evidence for a long-lasting Proterozoic world in which oxygen levels remained well below modern levels.

Lifetime-engineered NIR-II nanoparticles unlock multiplexed in vivo imaging.

Abstract: Deep tissue imaging in the second near-infrared (NIR-II) window holds great promise for physiological studies and biomedical applications1–6. However, inhomogeneous signal attenuation in biological matter7,8 hampers the application of multiple-wavelength NIR-II probes to multiplexed imaging. Here, we present lanthanide-doped NIR-II nanoparticles with engineered luminescence lifetimes for in vivo quantitative imaging using time-domain multiplexing. To achieve this, we have devised a systematic approach based on controlled energy relay that creates a tunable lifetime range spanning three orders of magnitude with a single emission band. We consistently resolve selected lifetimes from the NIR-II nanoparticle probes at depths of up to 8 mm in biological tissues, where the signal-to-noise ratio derived from intensity measurements drops below 1.5. We demonstrate that robust lifetime coding is independent of tissue penetration depth, and we apply in vivo multiplexing to identify tumour subtypes in living mice. Our results correlate well with standard ex vivo immunohistochemistry assays, suggesting that luminescence lifetime imaging could be used as a minimally invasive approach for disease diagnosis. Using lifetime-resolved imaging techniques, engineered nanoparticles can be used to perform multiplexed imaging in the NIR-II region with limited interference from biological tissues, thus by-passing the challenges of conventional deep imaging.

The role of the fluid phase during regional metamorphism and deformation

Abstract: Evidence from rock microstructures, mass transfer and isotopic exchange indicates that substantial quantities of aqueous fluids are involved in low- and medium-grade regional metamorphism. Similar conclusions are drawn from many retrograde environments, whereas high-grade metamorphic fluids may be melt dominated. The mobile fluids play essential roles in metamorphic reactions, mass transport and deformation processes. These processes are linked by the mechanical consequences of meta- morphic fluid pressures (Pr) generally being greater than or equal to the minimum principal compressive stress. Under such conditions meta- morphic porosity comprises grain boundary tubules and bubbles together with continuously generated (and healed) microfractures. Deform- ation results in significant interconnected porosity and hence enhanced permeability. Lithologically and structurally controlled perme- ability variations may cause effective fluid channelling. Simple Rayleigh-Darcy modelling of a uniformly permeable, crustal slab shows that convective instability of metamorphic fluid is expected at the permeabilities suggested for the high Pf metamorphic conditions. Complex, large- scale convective cells operating in overpressured, but capped systems may provide a satisfactory explanation for the large fluid/rock ratios and extensive mass transport demonstrated for many low- and medium-grade metamorphic environ- ments. Such large-scale fluid circulation may have important consequences for heat transfer in and the thermal evolution of metamorphic

How many human proteoforms are there

Abstract: Despite decades of accumulated knowledge about proteins and their post-translational modifications (PTMs), numerous questions remain regarding their molecular composition and biological function O