X-Ray Diffraction and Reflectivity Validation of the Depletion Attraction in the Competitive Adsorption of Lung Surfactant and Albumin

Lung surfactant (LS) and albumin compete for the air-water interface when both are present in solution. Equilibrium favors LS because it has a lower equilibrium surface pressure, but the smaller albumin is kinetically favored by faster diffusion. Albumin at the interface creates an energy barrier to subsequent LS adsorption that can be overcome by the depletion attraction induced by polyethylene glycol (PEG) in solution. A combination of grazing incidence x-ray diffraction (GIXD), x-ray reflectivity (XR), and pressure-area isotherms provides molecular-resolution information on the location and configuration of LS, albumin, and polymer. XR shows an average electron density similar to that of albumin at low surface pressures, whereas GIXD shows a heterogeneous interface with coexisting LS and albumin domains at higher surface pressures. Albumin induces a slightly larger lattice spacing and greater molecular tilt, similar in effect to a small decrease in the surface pressure. XR shows that adding PEG to the LS-albumin subphase restores the characteristic LS electron density profile at the interface, and confirms that PEG is depleted near the interface. GIXD shows the same LS Bragg peaks and Bragg rods as on a pristine interface, but with a more compact lattice corresponding to a small increase in the surface pressure. These results confirm that albumin adsorption creates a physical barrier that inhibits LS adsorption, and that PEG in the subphase generates a depletion attraction between the LS aggregates and the interface that enhances LS adsorption without substantially altering the structure or properties of the LS monolayer.     

Sensitive detection of cardiac biomarker using ZnS nanoparticles as novel signal transducers

C-reactive protein (CRP), a 115 kDa pentameric protein, is one of the important cardiac biomarkers that are indicative of coronary heart events. Sensitive detection of CRP in human serum is critical for the diagnosis of coronary heart disease. This work presents a sensitive sandwich immunoassay for the detection of CRP in human serum using zinc sulfide (ZnS) nanoparticles as novel fluorescence signal transducers. In this assay, monoclonal anti-CRP antibodies are used to capture CRP in human serum, and then the captured CRPs are incubated with biotinylated monoclonal anti-CRP and Neutravidin coated ZnS nanoparticle to form sandwich immunocomplexes. Quantification of CRP occurs when zinc ions released from ZnS nanoparticle labels are mixed with zinc-ion sensitive fluorescence indicator Fluozin-3 for fluorescence generation. The developed assay presents a detection limit around 10 pM and a detection range with more than two orders of magnitude.     

Human chromosome 6- and 11-encoded factors support human immunodeficiency virus type 1 Rev function in A9 cells.

The precise mechanism of Rev-mediated expression of human immunodeficiency virus (HIV-1) late genes is not well characterized. We recently proposed a requirement for HIV-1 Rev responsive element (RRE) RNA binding host nuclear proteins in Rev function. In this report, using a transient transfection assay of Rev function, we further demonstrate the role of host cell factors in HIV-1 Rev function. Murine A9 cells, which are inefficient in forming RRE-host protein ribonucleoprotein complexes, are also inefficient in supporting Rev function. We also show that host cell factor(s) encoded by human chromosomes 6 and 11 can support HIV-1 Rev-mediated expression of unspliced viral mRNAs in murine A9 cells.     

Chemical genetics reveals a role for Mps1 kinase in kinetochore attachment during mitosis

Accurate chromosome segregation depends on proper assembly and function of the kinetochore and the mitotic spindle. In the budding yeast, Saccharomyces cerevisiae, the highly conserved protein kinase Mps1 has well-characterized roles in spindle pole body (SPB, yeast centrosome equivalent) duplication and the mitotic checkpoint. However, an additional role for Mps1 is suggested by phenotypes of MPS1 mutations that include genetic interactions with kinetochore mutations and meiotic chromosome segregation defects and also by the localization of Mps1 at the kinetochore, the latter being independent of checkpoint activation. We have developed a new MPS1 allele, mps1-as1, that renders the kinase specifically sensitive to a cell-permeable ATP analog inhibitor, allowing us to perform high-resolution execution point experiments that identify a novel role for Mps1 subsequent to SPB duplication. We demonstrate, by using both fixed- and live-cell fluoresence techniques, that cells lacking Mps1 function show severe defects in mitotic spindle formation, sister kinetochore positioning at metaphase, and chromosome segregation during anaphase. Taken together, our experiments are consistent with an important role for Mps1 at the kinetochore in mitotic spindle assembly and function.     

Further investigation of simian immunodeficiency virus Vif function in human cells

Primate lentivirus Vif proteins function by suppressing the antiviral activity of the cell-encoded apolipoprotein B mRNA-editing enzyme-catalytic polypeptide-like (APOBEC) proteins APOBEC3G and APOBEC3F. It has been hypothesized that species-specific susceptibilities of APOBEC proteins to Vif proteins may help govern the transmission of primate lentiviruses to new host species. Consistent with this view and with previous results, we report that the Vif proteins of several diverse simian immunodeficiency viruses (SIVs) that are not known to infect humans are not effective inhibitors of human APOBEC3G or APOBEC3F when assessed in transient-transfection experiments. Unexpectedly, this lack of SIV Vif function did not prevent the replication of two vif-deficient SIVs (SIVtan and SIVmnd1; isolated from tantalus monkeys and mandrills, respectively) in a human T-cell line, HUT78, that expresses both APOBEC 3G and APOBEC3F, a finding which demonstrates that some SIVs are partially resistant to the antiretroviral effects of these enzymes irrespective of Vif function. Additional virus replication studies also revealed that the Vif protein of SIVtan is, in fact, active in human T cells, as it substantially enhanced the replication of its cognate virus and human immunodeficiency virus type 1. In sum, we now consider it improbable that species-specific restrictions to SIV Vif function can explain the lack of human infection with certain SIVs. Instead, our data reveal that the species-specific modulation of Vif function is more complex than previously envisioned and that additional (as-yet-unidentified) viral or host factors may be involved in regulating this dynamic interaction between host and pathogen.     

A clarification of two congeners,Pseudodiaptomus lobipes and P. binghami (Calanoida,Pseudodiaptomidae) from India,with description of P. mixtus sp.n. from Bangladesh

Two closely related and often confused species of Pseudodiaptomus from the Lobus-species group, P. lobipes and P. binghami are redescribed from various locations along the east coast of India. These species predominately occur in freshwater though they can survive temporary periods of increased salinity. The distinctive features of the species are found on: female caudal ramal setae, female and male urosome 1–2 spinulation patterns, and fifth legs. A new species P. mixtus from Bangladesh is described.     

Effects of the endosomal lipid bis(monoacylglycero)phosphate on the thermotropic properties of DPPC: A 2H NMR and spin label EPR study

Bis(monoacylglycero)phosphate (BMP) is an endosomal lipid with a unique structure that is implicated in the formation of intraendosomal vesicular bodies. Here we have characterized the effects of dioleoyl-BMP (BMP_18:1) at concentrations of 5, 10, 15 and 20 mol% on the thermotropic behavior of dipalmitoyl phosphatidylcholine (DPPC) vesicles, and compared them to those of equimolar concentrations of dioleoyl phosphatidylglycerol (DOPG), a structural isoform of BMP_18:1. Because BMP is found in the acidic environments of the late endosome and intralysosomal vesicles, samples were prepared at pH 4.2 to mimic the pH of the lysosome. Both ²H NMR of perdeuterated DPPC and spin-labeled EPR with 16-doxyl phosphatidylcholine were utilized in these investigations. NMR and EPR results show that BMP_18:1 induces a lowering in the main phase transition temperature of DPPC similar to that of DOPG. The EPR studies reveal that BMP_18:1 induced more disorder in the L_β phase when compared to equimolar concentrations of DOPG. Analysis from dePaked ²H NMR spectra in the L_α phase reveals that BMP_18:1 induces less disorder than equal concentrations of DOPG. Additionally, the results demonstrate that BMP mixes with other phospholipids as a phospholipid and not as a detergent molecule as once speculated.     

Mapping sea level rise impacts to identify climate change adaptation opportunities in the Chesapeake and Delaware Bays,USA

Wetlands Ecology and Management - Salt marshes are at risk globally if they cannot keep pace with sea level rise. Along the United States Mid-Atlantic coast, high marsh has already declined, and is...     

Biology and Functional Ecology of Equisetum with Emphasis on the Giant Horsetails

Horsetails are unique survivors of a very ancient group of vascular plants, the Sphenophyta, which has a history reaching back to the Upper Devonian. Despite the striking conservatism of Equisetum architecture and anatomy and the small number of species (15) in the modern flora, their ability to thrive under a wide range of conditions is remarkable. This is due to a diverse suite of adaptations that allow tolerance of disturbance, soil anoxia, high metals, and salinity, along with efficient nutrient uptake and nitrogen fixation. The giant horsetails represent the largest living Sphenophyta and provide insights into how their larger ancestors lived and how this ancient lineage has managed to survive in tropical regions.