Balance between fluorescence enhancement and association affinity in fluorescent heteroditopic indicators for imaging zinc ion in living cells

A fluorescent heteroditopic indicator for the zinc(II) ion possesses two different zinc(II) binding sites. The sequential coordination of zinc(II) at the two sites can be transmitted into distinct fluorescence changes. In the heteroditopic ligand system that our group developed, the formations of mono- and dizinc(II) complexes along an increasing gradient of zinc(II) concentration lead to fluorescence enhancement and an emission bathochromic shift, respectively. The extents of these two changes determine the sensitivity and, ultimately, the effectiveness of the heteroditopic indicator in quantifying zinc(II) ion over a large concentration range. In this work, a strategy to increase the degree of fluorescence enhancement upon the formation of the monozinc(II) complex of a heteroditopic ligand under simulated physiological conditions is demonstrated. Fluorination of the pyridyl groups in the pentadentate N,N,N'-tris(pyridylmethyl)ethyleneamino group reduces the apparent pK(a) value of the high-affinity site, which increases the degree of fluorescence enhancement as the monozinc(II) complex is forming. However, fluorination impairs the coordination strength of the high-affinity zinc(II) binding site, which in the triply fluorinated ligand reduces the binding strength to the level of the low-affinity 2,2'-bipyridyl. The potential of the reported ligands in imaging zinc(II) ion in living cells was evaluated. The subcellular localization properties of two ligands in five organelles were characterized. Both benefits and deficiencies of these ligands were revealed, which provides directions for the near future in this line of research.     

Harmonic morphisms and bicomplex manifolds

We use functions of a bicomplex variable to unify the existing constructions of harmonic morphisms from a 3-dimensional Euclidean or pseudo-Euclidean space to a Riemannian or Lorentzian surface. This is done by using the notion of complex-harmonic morphism between complex-Riemannian manifolds and showing how these are given by bicomplex-holomorphic functions when the codomain is one-bicomplex dimensional. By taking real slices, we recover well-known compactifications for the three possible real cases. On the way, we discuss some interesting conformal compactifications of complex-Riemannian manifolds by interpreting them as bicomplex manifolds.     

Non-invasive quantification of brain tumor-induced astrogliosis

Background  

CNS injury including stroke, infection, and tumor growth lead to astrogliosis, a process that involves upregulation of glial fibrillary acidic protein (GFAP) in astrocytes. However, the kinetics of astrogliosis that is related to these insults (i.e. tumor) is largely unknown.     

XPS study of laser fabricated titanium/KaptonFN interfaces

KaptonFN film consists of a polyimide core that has been laminated with FEP fluoropolymer outer layers. This composite material's resistance to most chemical solvents, heat sealability and low moisture uptake make KaptonFN attractive as a packaging material for electronics and implantable devices. KaptonFN/Ti micro-joints were fabricated by using focused infrared laser irradiation. The micro-joints were mechanically debonded, and the KaptonFN/Ti interfaces were studied by using X-ray photoelectron spectroscopy (XPS). The locus of failure of the joints was found to be in the FEP layer near the interface with the Ti. The XPS results give evidence for the formation of TiF bond in the interfacial region.     

What Factors Affect Attitudes Toward Women in Science Held by High School Biology Students?

To achieve the goal of science for all Americans, students of both genders must believe that careers in science are equally appropriate for women. Yet male and female students in high school science classes do not have the same views of women in science. This study investigated the influence of 17 factors on high school students' attitudes toward women in science. Data were collected from 844 students enrolled in biology classes in an urban school district in Georgia. Multiple regression determined that the 17 factors significantly influence students' attitudes toward women in science, accounting for 28% of common variance. The four most significant factors - student gender, science ability, level of education the student plans to complete, and career interest-accounted for 24.6% of total variance. Female students who have high science ability, plan to complete high levels of education, and who have career interests in science showed more favorable attitudes toward women in science. Males with low science ability, low levels of education they plan to complete, and no interest in science as a career had the least favorable attitudes toward women in science. Male students with less positive attitudes toward science careers for women need to be included in programs aimed at encouraging all students to consider science careers.     

Angle-resolved photoemission from CO chemisorbed on Rh(110)

He(II)-excited UPS spectra of CO chemisorbed on Rh(110) have been acquired in symmetry-equivalent directions relative to the substrate. In these spectra a marked anisotropy was noted in the emission from the 4σ level. Comparison of the experimental spectra with calculations of the differential photoionization cross-sections suggests that the CO molecule is chemisorbed in an end-on configuration with the carbon end nearer to the surface.     

MNDO calculations of the effects of substitution on antioxidant activity of phenols and Vitamin E

MNDO calculations are reported for the O-H bond dissociation energy in phenol and -OH, -CH₃, and -NH₂ substituted phenols. The phenol dissociation energy agrees well with the experimental result, as does the change due to a para -OH group; the agreement is less good for methyl substitution. The effect of rotating the O-H substituent out of the benzene plane is explored and analyzed, and the calculations are related to corresponding effects in Vitamin E chemistry.     

First symmetry tests in polarized Z0 decays to bbg

We have made the first direct symmetry tests in the decays of polarized Z0 bosons into fully identified bbg states, collected in the SLD experiment at SLAC. We searched for evidence of parity violation at the bbg vertex by studying the asymmetries in the b-quark polar- and azimuthal-angle distributions, and for evidence of T-odd, CP-even or CP-odd, final-state interactions by measuring angular correlations between the three-jet plane and the Z0 polarization. We found results consistent with standard model expectations and set 95% C. limits on anomalous contributions.     

Observation of quantum coherence in mesoscopic molecular magnets

By applying a transverse magnetic field B( perpendicular) of sufficient strength to the uniaxial molecular magnets Fe8 and Mn12, the tunneling splitting Delta(t) of their S = +/-10 magnetic ground states can be made large compared to perturbations such as hyperfine and dipolar interactions. We present evidence for such a Delta(t) from magnetic specific heat data below 1 K that is consistent with coherent quantum mechanical tunneling in a "mesoscopic" system under such conditions.     

Reduced-symmetry deep-cavity cavitands

The syntheses of reduced-symmetry deep-cavity cavitands by two-stage stereoselective bridging with substituted benzal bromides is reported. Conditions for the optimal formation of the trisbridged derivatives were readily established. However, it was not possible to determine conditions which selectively promoted formation of either one of the two bisbridged species, or the monobridged compound, above the other products. A comparison of yields for A/B bisbridged derivatives verses A/C bisbridged derivatives may indicate that the one-pot formation of deep-cavity cavitands occurs primarily through the former species.