Patterns of crystal organization and calcite twin formation in planktonic,rotaliid, foraminifera shells and spines

The foraminiferal order Rotaliida represents one third of the extant genera of foraminifers. The shells of these organisms are extensively used to decipher characteristics of marine ecosystems and global climate events.It was shown that shell calcite of benthic Rotaliida is twinned. We extend our previous work on microstructure and texture characterization of benthic Rotaliida and investigate shell calcite organization for planktonic rotaliid species. Based on results gained from electron backscattered diffraction (EBSD) and field emission electron microscopy (FESEM) imaging of chemically etched/fixed shell surfaces we show for the planktonic species Globigerinoides sacculifer, Pulleniatina obliquiloculata, Orbulina universa (belonging to the two main planktonic, the globigerinid and globorotaliid, clades): very extensive 60°-{0 0 1}-twinning of the calcite and describe a new and specific microstructure for the twinned crystals. We address twin and crystal morphology development from nucleation within a biopolymer template (POS) to outermost shell surfaces. We demonstrate that the calcite of the investigated planktonic Rotaliida forms through competitive growth. We complement the structural knowledge gained on the clade 1 and clade 2 species with EBSD results of Globigerinita glutinata and Candeina nitida shells (clade 3 planktonic species). The latter are significantly less twinned and have a different shell calcite microstructure.We demonstrate that the calcite of all rotaliid species is twinned, however, to different degrees. We discuss for the species of the three planktonic clades characteristics of the twinned calcite and of other systematic misorientations. We address the strong functionalization of foraminiferal calcite and indicate how the twinning affects biocalcite material properties.     

Hexagonal-columnar mesophases of acylated azacrowns with enhanced stabilities

A series of discotic liquid crystals based on completely acylated macrocyclic oligoamines (azacrowns) has been synthesized. Discotic mesophases could be very highly stabilized by making use of an increased steric hindrance, caused by supplemental lateral meta-substituents which were introduced into the cinnamic acids used as the acylation agents. Employing this method yields compounds exhibiting hexagonal mesophases over a very broad range of more than 300°. Even if very large macrocycles are used as the core of such disc-shaped compounds, enantiotropic mesophases are achieved. Themeta-substituents as well as the size of the azacrowns were varied and their influence on the mesomorphic behavior was studied.     

Structure of low density lipoprotein in complexes formed with arterial matrix components

Temperature dependent techniques (differential scanning calorimetry, polarizing light microscopy and n.m.r. spectroscopy) were used to study the physico-chemical state of low density lipoprotein (LDL) in LDL-aorta glycosaminoglycan and LDL aorta proteoglycan complexes. Complex formation between LDL and glycosaminoglycans (GAGs) resulted in a reversible liquid-liquid crystalline reorganization of the core lipids within the LDL molecule. In the proteoglycan-LDL complexes, prepared by the addition of porcine arterial proteoglycans or of human ‘lipoprotein complexing proteoglycan’, the formation of liquid crystals was an irreversible process, suggesting that the protein moiety of the proteoglycans also participates in the interaction with LDL. Arterial specimens were also examined. In atheromatous intima samples, spherulites with the above characteristics could be identified at the sites of lipoprotein deposition. Since proteoglycans are present in the arterial intima media, the phenomena observed in the present model system may also take place in vivo. The formation of proteoglycan-LDL complexes may result in the establishment of a liquid crystalline LDL structure and may thus play a role in the immobilization of LDL and in the development of the atherosclerotic lesion.     

NMR studies of membranes composed of glycolipids and phospholipids

Lipid membranes composed of monogalactosyldiacylglycerol (MGDG) and dimyristoylphosphatidylcholine (DMPC) were studied by means of NMR spectroscopy. The macroscopic phase behaviour was investigated by ³¹P NMR under stationary conditions, whereas microscopic properties such as segmental ordering were probed by two-dimensional ¹H-¹³C separated local field experiments under magic-angle spinning conditions. Our results clearly show that ordering/disordering effects occur for the headgroups as well as for the acyl chains when the sample composition is varied. In particular, the ¹H-¹³C dipolar couplings within the galactose headgroup of MGDG exhibited significant concentration dependence.     

Hydrogel baits pose minimal risk to non-target insects and beneficial species

Invasive ants are a significant pest around the world and have negative impact on natural and agricultural environments. Chemical control is mainly accomplished with residual sprays and toxic baits. Hydrogel baits are a novel bait formulation that has proven highly effective against multiple invasive ant species, but potential non-target effects have not been investigated. The baits are typically saturated in 25% sucrose solution which makes them attractive to foraging ants and potentially non-target organisms such as pollinators. The objective of the current study was to perform field studies to assess the potential attractiveness of hydrogel baits to various pollinating and non-pollinating arthropods in a variety of ecosystems, including tallgrass prairies, urban pollinator gardens, and commercial apiaries. The study focused on social Hymenoptera as pesticides are acutely toxic to various Hymenoptera and have been implicated as one of the contributing factors in pollinator declines. Results show that Diptera were overwhelmingly the most common visitors and accounted for >40% of all visitors. Other common groups included beetles and yellowjackets. Common pollinating insects such as honeybees, solitary bees, and butterflies rarely visited the baits and accounted for ca. 3% of all visits and were never found on ground baits. Results show that the risk to pollinators is relatively low; most arthropods attracted to the baits were taxa that are extremely abundant, not of conservation concern, and in some cases pestiferous or invasive. The deployment of hydrogels for invasive ant control in areas where multiple invasive insect taxa are present may have the additional benefit of controlling multiple pests.     

Generalised local bond order parameter analysis: application to colloidal particles with dendritic polymer brushes

This study examines the self-assembly of colloidal particles with spherical dendritic brushes. The effective interaction between these particles was studied in Monte Carlo simulations of the Kremer–Grest model. Results confirmed the transferability of the effective potential at different temperatures. Using the potential of mean force obtained from Monte Carlo simulations, the structural formation of the system was studied in a three-dimensional system. The system is a crystalline state in the intermediate density range and exhibits re-entrant melting at much higher densities. Based on generalised local bond order analysis, a refined numerical method is proposed for analysing the structural formation of colloidal particles in three-dimensional systems. The numerical technique accurately reproduced the formation of the colloidal system.     

Preliminary X-ray analysis of crystals of plasminogen activator inhibitor-1

Crystals of bacterially expressed plasminogen activator inhibitor (PAI-1) suitable for X-ray diffraction analysis have been obtained from 8% (w/v) PEG 1500, pH 8.25. The space group is P1, and the lattice constants are a = 82.17 A, b = 47.82 A, c = 62.89 A, alpha = 90.00 degrees, beta = 106.90 degrees, gamma = 106.84 degrees. The diffraction limit is 2.3 A, and the unit cell contains two molecules of PAI-1. The crystals contain latent PAI-1 which can be partly reactivated by exposure to denaturants.     

Sieve-Element Characters of the Proteaceae and Elaeagnaceae: Nuclear Crystals,Phloem Proteins and Sieve-Element Plastids

The sieve-element characters of 34 species from the Proteaceae and Elaeagnaceae have been studied by transmission electron microscopy. While nondispersive protein bodies and dispersive P-protein are typical components of both families, specific forms and/or their distinctive origin accentuate some taxa. Within the Grevilloideae, subfamily of Proteaceae, a number of Australian species and genera contain protein crystals of nuclear origin arranged into rosette-like bodies, while in the other members studied from the same subfamily no nondispersive protein bodies were found. Several Australian and South African genera of the Proteoideae contain compound-spherical nondispersive protein bodies that reside in the cytoplasm from their very beginning. In the Elaeagnaceae three different P-protein bodies are present of which one is tubular and dispersing, another is nondispersive and of irregular-stellate form, and a third is globular (resembling a P-protein from Cucurbita). The great majority of the species studied from the Proteaceae contains form-Ss sieve-element plastids, Lomatia ilicifolia and Macadamia ternifolia are distinct in having form-Pcs plastids. The average diameter of stem sieve-element plastids in the family is 1.38 μm. The Elaeagnaceae (three species investigated) is a pure form-So family (average diameter: 0.8 μm). There are no specific sieve-element characters that would support any relationship between the Proteaceae and Elaeagnaceae. While affinities of the former to pre-Gondwanan parts of the Rosanae/Myrtanae are discussed, a reconsideration of the Elaeagnaceae as a possible member of the Violanae (identical features with Cucurbitaceae) is proposed.