[Show abstract][Hide abstract] ABSTRACT: The South Atlantic has experienced periods of intense anoxia and black shale deposition that form an important hydrocarbon source. Here we have investigated the depositional environment during the initial opening phase of the South Atlantic during the Early Cretaceous. The period is crucial as it is characterized by extensive source rock deposition and because it sets the stage for subsequent periods of anoxia within the northern sub-basin of the South Atlantic. Within an Aptian sequence of organic-rich sediments (up to 40% total organic carbon, TOC) from Deep Sea Drilling Project (DSDP) Site 364, we found a distinct biomarker distribution, including the presence of isorenieratane and an array of thiophenic (S-containing) compounds. Our results indicate that, during the time of deposition, corresponding to the initial phase of opening of the South Atlantic, most of the water column in the Angola Basin was hypersaline (> 40‰) and euxinic, with euxinia episodically reaching the photic zone. The low relative abundance of marine biomarkers in the samples suggests that these extreme conditions were unfavourable for typical marine organisms. Stratigraphically up-section, the biomarker distribution changed as the TOC content gradually decreased (< 20 wt.%), isorenieratane and thiophenic compounds became less abundant and marine biomarkers became more abundant. We interpret the results to reflect a shift towards more open marine conditions, with less extensive euxinia/anoxia and normal marine salinity as the opening of the South Atlantic continued and the basin became less restricted. Our results demonstrate that the opening of the South Atlantic was the dominant control on the deposition of organic rich shales in the Angola Basin during the Aptian, highlighting the control of local basin geography on the depositional environment and formation of organic rich black shales during the Early Cretaceous.
[Show abstract][Hide abstract] ABSTRACT: Pioneering work by Edler et al. has spawned a new sub-set of mesostructured materials. These are solid, self-supporting films comprising surfactant micelles encased within polymer hydrogel; composite polymer-surfactant films can be grown spontaneously at the air-liquid interface and have defined and controllable mesostructures. Addition of siliconalkoxide to polymer-surfactant mixtures allows for the growth of mesostructured hybrid polymer-surfactant silica films that retain film geometry after calcinations and exhibit superior mechanical properties to typically brittle inorganic films. Growing films at the air-liquid interface provides a rapid and simple means to prepare ordered solid inorganic films, and to date the only method for generating mesostructured films thick enough (up to several hundred microns) to be removed from the interface. Applications of these films could range from catalysis to encapsulation of hydrophobic species and drug delivery. Film properties and mesostructures are sensitive to surfactant structure, polymer properties and polymer-surfactant phase behaviour: herein it will be shown how film mesostructure can be tailored by directing these parameters, and some interesting analogies will be drawn with more familiar mesostructured silica materials.
Advances in Colloid and Interface Science. 01/2014;
[Show abstract][Hide abstract] ABSTRACT: This review discusses recent advances in the design and construction of protocell models based on the self-assembly or microphase separation of non-lipid building blocks. We focus on strategies involving partially hydrophobic inorganic nanoparticles (colloidosomes), protein–polymer globular nano-conjugates (proteinosomes), amphiphilic block copolymers (polymersomes), and stoichiometric mixtures of oppositely charged biomolecules and polyelectrolytes (coacervates). Developments in the engineering of membrane functionality to produce synthetic protocells with gated responses and control over multi-step reactions are described. New routes to protocells comprising molecularly crowded, cytoskeletal-like hydrogel interiors, as well as to the construction of hybrid protocell models are also highlighted. Together, these strategies enable a wide range of biomolecular and synthetic components to be encapsulated, regulated and processed within the micro-compartmentalized volume, and suggest that the development of non-lipid micro-ensembles offers an approach that is complementary to protocell models based on phospholipid or fatty acid vesicles.
Current Opinion in Chemical Biology. 01/2014; 22:1–11.
[Show abstract][Hide abstract] ABSTRACT: Highlights
•Silica nanoparticles were dispersed in organic solvent with cationic surfactants.•Both Ho and Nd surfactants produce charged, electrophoretic particles.•Only the surfactant with Ho (high magnetic moment) produces magnetically-responsive particles.
Journal of Colloid and Interface Science 01/2014; 426:252–255.
[Show abstract][Hide abstract] ABSTRACT: A series of glycan-coated quantum dots were prepared to probe the effect of glycan presentation in intracellular localization in HeLa and SV40 epithelial cells. We show that glycan density mostly impacts on cell toxicity, whereas glycan type affects the cell uptake and intracellular localization. Moreover, we show that lactose can act as a "Trojan horse" on bi-functionalized QDs to help intracellular delivery of other non-internalizable glycan moieties and largely avoid the endosomal/lysosomal degradative pathway.
[Show abstract][Hide abstract] ABSTRACT: An original- syn: The first enantioselective Suzuki-Miyaura cross-coupling of chiral, enantioenriched secondary allylic boronic esters is described (see scheme; DME=dimethoxyethane). Mechanistic studies show that the reactions proceed via γ-selective transmetalation followed by reductive elimination. The reaction provides the first independent confirmation that the transmetalation of boronic esters proceeds via a syn pathway.
[Show abstract][Hide abstract] ABSTRACT: The pyrene nucleus is a valuable component for materials, supramolecular and biological chemistry, due to its photophysical/electronic properties and extended rigid structure. However, its exploitation is hindered by the limited range of methods and outcomes for the direct substitution of pyrene itself. In response to this problem, a variety of indirect methods have been developed for preparing pyrenes with less usual substitution patterns. Herein we review these approaches, covering methods which involve reduced pyrenes, transannular ring closures and cyclisations of biphenyl intermediates. We also showcase the diverse range of substituted pyrenes which have been reported in the literature, and can serve as building blocks for new molecular architectures.
[Show abstract][Hide abstract] ABSTRACT: We present a general multi-reference framework for treating strong correlation in vibrational structure theory, which we denote the vibrational active space self-consistent field (VASSCF) approach. Active configurations can be selected according to excitation level or the degrees of freedom involved, or both. We introduce a novel state-specific second-order multi-configurational perturbation correction that accounts for the remaining weak correlation between the vibrational modes. The resulting VASPT2 method is capable of accurately and efficiently treating strong correlation in the form of large anharmonic couplings, at the same time as correctly resolving resonances between states. These methods have been implemented in our new dynamics package DYNAMOL, which can currently treat up to four-body Hamiltonian coupling terms. We present a pilot application of the VASPT2 method to the trans isomer of formic acid. We have constructed a new analytic potential that reproduces frozen core CCSD(T)(F12*)/cc-pVDZ-F12 energies to within 0.25% RMSD over the energy range 0-15 000 cm(-1). The computed VASPT2 fundamental transition energies are accurate to within 9 cm(-1) RMSD from experimental values, which is close to the accuracy one can expect from a CCSD(T) potential energy surface.
The Journal of Chemical Physics 11/2013; 139(19):194108.
[Show abstract][Hide abstract] ABSTRACT: The funeral preparations for ancient Egyptian dead were extensive. Tomb walls were often elaborately painted and inscribed with scenes and objects deemed desirable for the afterlife. Votive objects, furniture, clothing, jewelry, and importantly, food including bread, cereals, fruit, jars of wine, beer, oil, meat, and poultry were included in the burial goods. An intriguing feature of the meat and poultry produced for the deceased from the highest levels of Egyptian society was that they were mummified to ensure their preservation. However, little is known about the way they were prepared, such as whether balms were used, and if they were used, how they compared with those applied to human and animal mummies? We present herein the results of lipid biomarker and stable carbon isotope investigations of tissues, bandaging, and organic balms associated with a variety of meat mummies that reveal that treatments ranged from simple desiccation and wrapping in bandages to, in the case of the tomb of Yuya and Tjuia (18th Dynasty, 1386-1349 BC), a balm associated with a beef rib mummy containing a high abundance of Pistacia resin and, thus, more sophisticated than the balms found on many contemporaneous human mummies.
Proceedings of the National Academy of Sciences 11/2013;
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