ISOLATION AND CHARACTERIZATION OF THE PRESUMED PHOTORECEPTOR PROTEIN OF Blepharisma japonicum

Abstract— Photosensory responses in the ciliated protozoan Blepharisma japonicum are mediated by a hypericin-like chromophore, blepharismin, localized in granules distributed under the cell membrane. A blepharismin-binding protein, with an apparcnt molecular weight ranging between 35 and 38 kDa, has been isolated by means of column separations and preparative isoelectric focusing and characterized by means of gel electrophoresis, analytic isoelectric focusing as well as absorption and fluorescence spectroscopy.     

The complement: a solution to liquid drop finite size effects in phase transitions

The effects of the finite size of a liquid drop undergoing a phase transition are described in terms of the complement, the largest (but mesoscopic) drop representing the liquid in equilibrium with the vapor. Vapor cluster concentrations, pressure, and density from fixed mean density lattice gas (Ising) calculations are explained in terms of the complement generalization of Fisher's model. Accounting for this finite size effect is important for extracting the infinite nuclear matter phase diagram from experimental data.     

FLUORESCENCE OF Euglena gracilis PHOTORECEPTOR PIGMENT: AN in vivo MICROSPECTROFLUOROMETRIC STUDY

Abstract— The spectroscopic characterization of the photoreceptor pigment is one of the main questions in the study of the photosensory transduction chains in photomotile microorganisms. One of the possible techniques that can be used is in vivo microspectrofluorometry. By means of a tunable dye-laser microspectrofiuorometer developed by us, we have investigated some of the spectroscopic properties of the photoreceptor pigment of the green flagellate Euglena gracilis. The in vivo fluorescence excitation spectrum has been determined and the fluorescence quantum yield has been measured. The results show that flavins are indeed present in the paraflagellar body of E. gracilis and that their fluorescence quantum yield is much lower than that of a free flavin. An estimate of the order of magnitude of the rate constants for primary molecular reactions is tentatively given.     

UVB Monochromatic Action Spectrum for the Inhibition of Photosynthetic Oxygen Production in the Green Alga Dunaliella saha

The effect of monochromatic UVB (280–315 nm) irradiation on the photosynthetic activity of the marine green alga Dunaliella salina was investigated by monitoring the rate of oxygen exchange. Samples were irradiated with narrow bands centered at different UV wavelengths (281, 290, 300, 310 and 322 nm). In a first set of experiments the samples were preirradiated keeping constant the irradiance and varying exposure time. By increasing UVB fluence, a wavelength-dependent decrease in the rate of oxygen production was observed. In a second set of experiments oxygen exchange was monitored simultaneously to UVB irradiation. The decline in the rate of oxygen production was sharper at short wavelengths and faster with increasing UVB photon flux density. The photon fluence action spectra derived from the two sets of experiments are in good agreement and indicate a decrease in the UVB-inhibiting effectiveness of two orders of magnitude from about 0.2 (mmol m-2)-1 at 281 nm to about 0.003 (mmol m-2)-1 at 322 nm. The photon flux density action spectrum derived from the second set of experiments indicates a smoother decrease from about 0.2 (pmol s-l m-2)-1 at 281 nm to about 0.05 (pmol s-l m-z)-l at 310 nm.     

ACTION SPECTRA OF THE PHOTOPHOBIC RESPONSE OF BLUE AND RED FORMS OF Blepharisma japonicum

Abstract— When exposed, in the presence of molecular oxygen, to light intensities of the order of3–30 W m^-2, the ciliate Blepharisma japonicum changes its color from red to blue, because of the photooxidation of the photoreceptor pigment, blepharismin, to pxyblepharismin. Both red-and blue-pigmnentes cells show step-up photophobic responses. The action spectra f the light-dependent behaviour of the red and the blue form of Blepharisma have been determined; their structure is very similar to that the photosensing and phototransducing properties of blepharismin are maintained in its photooxidized form. oxyblepharismin.     

An XPS study of SO2 ON A CaO surface derived from Ca(OH)2

The adsorption of SO₂ on a CaO surface derived from Ca(OH)₂ has been studied by X-ray photoelectron Spectroscopy. It is shown that SO₂ adsorbs molecularly on the CaO surface forming SO₃²⁻ and SO₄²⁻. The adsorbate SO₃²⁻ species shift the Ca2p core levels about 2 eV toward higher binding energy. However, the formation of SO₄²⁻ species does not induce any further observable changes in the Ca core line spectra. These results are explained and discussed in terms of an electronic charge transfer from the substrate metal atoms to the adsorbed molecules and vice versa.     

Biological weighting function of the UV-B-induced impairment of phototaxis in the freshwater ciliate Ophryoglena flava

We determined the biological weighting function (BWF) of the effect of UV radiation on phototaxis of the freshwater, histophagous ciliate Ophryoglena flava. Dose-effect curves were measured by exposing the cells to 12 different irradiation regimens obtained with two different levels of UV-B radiation and by using six filters with cutoff wavelengths ranging from 280 to 335 nm. The results show that there are significant damages to phototaxis at the doses used and that the effect increases when the cutoff is shifted toward short wavelengths. The data were used to calculate the BWF of phototaxis impairment by applying a nonlinear fit procedure. The BWF thus obtained decays exponentially with increasing wavelength in agreement with similar findings reported in the literature for other systems.     

Proteophenes – Amino Acid Functionalized Thiophene-based Fluorescent Ligands for Visualization of Protein Deposits in Tissue Sections with Alzheimer's Disease Pathology

Protein deposits composed of specific proteins or peptides are associated with several neurodegenerative diseases and fluorescent ligands able to detect these pathological hallmarks are vital. Here, we report the synthesis of a class of thiophene-based ligands, denoted proteophenes, with different amino acid side-chain functionalities along the conjugated backbone, which display selectivity towards specific disease-associated protein aggregates in tissue sections with Alzheimer's disease (AD) pathology. The selectivity of the ligands towards AD associated pathological hallmarks, such as aggregates of the amyloid-β (Aβ) peptide or tau filamentous inclusions, was highly dependent on the chemical nature of the amino acid functionality, as well as on the location of the functionality along the pentameric thiophene backbone. Finally, the concept of synthesizing donor-acceptor-donor proteophenes with distinct photophysical properties was shown. Our findings provide the structural and functional basis for the development of new thiophene-based ligands that can be utilized for optical assignment of different aggregated proteinaceous species in tissue sections.