Resonant soft-X-ray emission as a bulk probe of correlated electron behavior in metallic SrxCa1-xVO3.

The evolution of electron correlation in SrxCa1-xVO3 has been studied using a combination of bulk-sensitive resonant soft x-ray emission spectroscopy, surface-sensitive photoemission spectroscopy, and ab initio band structure calculations. We show that the effect of electron correlation is enhanced at the surface. Strong incoherent Hubbard subbands are found to lie ∼20% closer in energy to the coherent quasiparticle features in surface-sensitive photoemission spectroscopy measurements compared with those from bulk-sensitive resonant soft x-ray emission spectroscopy, and a ∼10% narrowing of the overall bandwidth at the surface is also observed.

Parvalbumins from coelacanth muscle. I. General survey.

Parvalbumins from coelacanth (Latimeria chalumnae) myogen have been isolated by gel filtration of Sephadex G-75 and DEAE-cellulose chromatography. Disc electrophoresis and cellulose acetate electrophoresis showed the homogeneity of the three first major parvalbumin peaks (pI = 5.44, pI = 4.95 and pI = 4.52). The fourth component was partially resolved into two more parvalbumins (pI = 3.78 and pI = 3.50) by preparative gel electrophoresis. Amino acid analyses and tryptic peptide maps separated the five components in two major categories. The two less acidic components differ only in the presence or absence of an N-terminal blocking group. The three more acidic components constitute the second category; in spite of this heterogeneity, they share the same amino acid sequence.

Parvalbumins from coelacanth muscle. III. Amino acid sequence of the major component.

The primary structure of the major parvalbumin (pI = 4.52) from coelacanth muscle (Latimeria chalumnae) has been determined. Sequence analysis of the tryptic peptides, in some cases obtained with beta-trypsin, accounts for the total amino acid content of the protein. Chymotryptic peptides provide appropriate sequence overlaps, to complete the localization of the tryptic peptides. Examination of the amino acid sequence of this protein shows the typical structure of a beta-parvalbumin. Its position in the dendrogram of related calcium-binding proteins corresponds to that usually accepted for crossopterygians.

Complete amino acid sequence of the sarcoplasmic calcium-binding protein (SCP-I) from crayfish (Astacus leptodactylus).

The complete amino acid sequence of the alpha chain of the dimeric sarcoplasmic Ca2+-binding protein (SCP-I = alpha 2) from crayfish (Astacus leptodactylus) has been determined by partial automatic sequencing of the peptides derived from tryptic digests of the protein after citraconylation or treatment with 1,2-cyclohexanedione. Overlapping peptides were obtained by cleavage with o-iodosobenzoic acid, or digestion with Staphylococcus aureus protease, thermolysin and pepsin. The acetylated N-terminus was identified by fast atom bombardment mass spectrometry. The monomeric protein contains 192 amino acids and has an Mr of 21,643. The sequence shows the presence of three calcium-binding sites and perhaps of two others that may be degenerated.

Conformational changes induced by Mg2+ on actin monomers. An immunologic attempt to localize the affected region.

The effect of Mg2+ ions on the conformation of G-actin and in particular on the accessibility of its antigenic regions has been tested. Experiments were performed with G-actin coupled to Sepharose 4B which was, therefore, maintained in the monomeric state. The results presented her show that the 2mM MgCl2-perturbed antigenic site is located in a central region of the actin sequence.

Analytical methodologies for atomic spectrometric determination of metallic oxides in UV sunscreen creams.

In this study, methodologies for determining titanium oxide, zinc oxide and iron oxide are proposed and assayed in commercial sunscreen products. The proposed methodology for TiO2, determination in sunscreens is based on a microwave-assisted treatment for digesting the organic components in a closed teflon reactor in presence of HNO3 and HCl. Titanium is determined by inductive coupled plasma emission spectrometry (ICP-AES). The proposed methodologies for measuring ZnO and Fe2O3 are based on a sample emulsification in water with a non ionic tensioactive and IBMK, followed by Zn and Fe determination by flame atomic absorption spectrometry (FAAS). The methodologies allow a precise and accurate determination of metallic oxides in UV sunscreen creams, where the sample treatment is less time-consuming than in the classic methods. To our knowledge this is the first study focused to the determination of metallic oxides in commercial sunscreen products.

[Voice quality in laryngectomees with phonatory prosthesis]. / Estudio de la calidad de la voz en laringuectomizados con prótesis fonatoria.

The Work is a study of quality voice in laryngectomy patients with speech prosthetic supports. We have studied the quality voice objective and subjective. We explain the results.

Thermal diffusion of Mn through GaAs overlayers on (Ga, Mn)As.

Thermally stimulated diffusion of Mn through thin layers of GaAs has been studied by x-ray photoemission. (Ga, Mn)As samples with 5 at% Mn were capped with 4, 6 and 8 monolayer (ML) GaAs, and Mn diffusing through the GaAs was trapped on the surface by means of amorphous As. It was found that the out-diffusion is completely suppressed for an 8 ML thick GaAs film. The short diffusion length is attributed to an electrostatic barrier formed at the (Ga, Mn)As/GaAs interface.

Anomalous bismuth-stabilized (2x1) reconstructions on GaAs(100) and InP(100) surfaces.

First-principles phase diagrams of bismuth-stabilized GaAs- and InP(100) surfaces demonstrate for the first time the presence of anomalous (2x1) reconstructions, which disobey the common electron counting principle. Combining these theoretical results with our scanning-tunneling-microscopy and photoemission measurements, we identify novel (2x1) surface structures, which are composed of symmetric Bi-Bi and asymmetric mixed Bi-As and Bi-P dimers, and find that they are stabilized by stress relief and pseudogap formation.

Monte Carlo simulation in phylogenies: an application to test the constancy of evolutionary rates.

Monte Carlo simulation has commonly been used in phylogenetic studies to test different tree-reconstruction methods, and consequently, its application for testing evolutionary models can be considered as a natural extension of this usage. Repetitive simulation of a given evolutionary process, under the restrictions imposed by the model to be tested, along a determinate tree topology allow the estimate of probability distributions for the desired parameters. Next, the phylogenetic tree can be reconstructed again without the constraints of the model, and the parameter of interest, derived from this tree, can be compared to the corresponding probability distribution derived from the restricted, simulated trees. As an example we have used Monte Carlo simulation to test the constancy of evolutionary rates in a set of cytochrome-c protein sequences.

Heat stability and reactivation of mare milk lysozyme.

Mare milk and aqueous solution of mare milk lysozyme were incubated for variable times between 30 C and 100 C at pH 3, 6, or 9. Lysozyme activity was stable at acid and neutral pH and labile at alkaline pH. Some of the results show the existence of a reactivation process in mare's milk and in aqueous solution. reaching 30 to 40% after incubation of the aqueous solution at 4 C for 20 days at pH 3 or 6.

Polymorphism in high-affinity calcium-binding proteins from crustacean sarcoplasm.

The sarcoplasmic calcium-binding proteins (SCP) from crayfish, lobster and shrimp myogen have been purified to homogeneity. These proteins exist as dimers and dissociate in the presence of sodium dodecyl sulfate or urea in subunits of 22000 molecular weight. During the last step of purification (DEAE-cellulose chromatography), SCP emerges in three peaks in the ratio of 14:1.5:1 for crayfish, of 7:2:1 for lobster and of 3:2:1 for shrimp. Gel electrophoresis and isoelectrofocusing experiments, under native and denaturing conditions, indicate that among the three SCP isotypes there are only two different polypeptide chains, alpha and beta, which appear in the form of three dimers: alpha 2, alpha beta and beta 2. The alpha and beta subunits differ slightly in polypeptide chain composition as found by amino acid analyses of the crayfish and lobster SCPs, and also by comparison of tryptic peptides for crayfish SCPs. The polymorphism observed in crustacean SCPs, which is increased by their ability to form dimers, contrasts with the situation prevailing among other invertebrate SCPs and vertebrate parvalbumins where only monomeric isotypes are found. Equilibrium binding studies show that all three SCP isotypes from both crayfish and lobster display the same metal-binding properties. They have in their dimeric form six Ca2+-binding sites: two calcium-specific sites, two Ca/Mg sites that interact with positive cooperativity and two Ca/Mg sites that interact with negative cooperativity. Interactions between the two subunits of SCP seem to result in cooperative binding of Ca2+, which in turn may control more efficiently Ca2+ fluxes in crustacean muscle.

Unmasking frequency-dependent selection in tri-cultures of Drosophila melanogaster.

Larval-to-adult viability was measured for three strains of Drosophila melanogaster: a wild strain and two eye colour mutant strains (cardinal and sepia) starting from seventy different genotypic compositions. Analyses of a sub-set of the data (not considering all genotypic frequencies) demonstrate frequency-dependence in the three strains. These results suggest that in this experiment, frequency-dependent selection may be masked by other selective forces, only being apparent when specific analyses are carried out.

On the analysis of viability data: an example with Drosophila.

Larval competition experiments involving two wild type and eight mutant strains of Drosophila melanogaster have been carried out following the substitution procedure proposed by Mather and Caligari (1981). Our main goal has been to compare the competitive abilities of two phenotypically indistinguishable strains (wild and Oregon-R) by means of their responses with eight different mutants. Prior to the analyses of viability data, we have studied the normalizing effect of several transformations in order to determine which was best suited for the analyses. The differences found among the five transformations tested and the untransformed data were not very great. The folded power transformation (Mosteller and Tukey, 1977) was finally chosen. No constant pattern in the responses of the two wild type strains to the mutant competitors was detected. This leads us to conclude that the nature of the competition between the two wild type strains cannot be predicted from a knowledge of their competition with other strains.

Fast atom bombardment mass spectra of various peptides from sarcoplasmic calcium-binding protein.

The sarcoplasmic calcium-binding protein of the crayfish Astacus leptodactylus is a calciprotein. The primary structure of this protein has been determined. Tryptic digestion of the denaturated protein followed by high-performance liquid chromatographic separation identified essentially eight peptides. The structure of these peptides has been confirmed after amino acid analysis by fast atom bombardment spectra in positive mode.

Haemodialysis-associated amyloidosis: beta 2-microglobulin alone or associated with globin chains?

1. The protein constituents of amyloid fibrils were characterized in amyloid deposits extracted from surgical material obtained from a 66-year-old patient undergoing maintenance haemodialysis and operated for a carpal tunnel syndrome. 2. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis disclosed the presence of bands at 12 and 14 kDa. Two-dimensional electrophoresis and Western blotting confirmed that the proteins were beta 2-microglobulin (beta 2M) and globin chains. 3. When the effluent of high-performance gel filtration chromatography corresponding to molecular masses of 10-15 kDa was subjected to Edman degradation, only one amino acid residue was found at each step. The 18 residues determined corresponded to the N-terminal sequence of beta 2M. 4. Although globin chains were clearly present in the amyloid material, they were not accessible for sequence determination. The identification of the other protein constituents present in the amyloid material, along with beta 2M, should provide a better understanding of haemodialysis-associated amyloidosis, the mechanisms of formation of which have not yet been completely determined.

Acute colonic diverticulitis: prospective comparative evaluation with US and CT.

PURPOSE: To compare the accuracy of ultrasonographic (US) and computed tomographic (CT) findings for diagnosis of acute colonic diverticulitis. MATERIALS AND METHODS: US and CT were prospectively performed in 64 consecutive patients suspected of having acute colonic diverticulitis. Images were interpreted independently in a blinded fashion. Imaging data were compared with the final diagnosis, which was based on initial clinical and follow-up examination results (n = 64) and pathologic (n = 22), endoscopic (n = 21), and contrast enema (n = 15) examination findings. RESULTS: Final diagnosis was acute colonic diverticulitis (n = 33), other acute abdominal condition (n = 24), or unknown (n = 7). Both CT and US findings yielded 84% accuracy. US and CT findings were not statistically significant different in terms of sensitivity (85% and 91%, respectively) and specificity (84% and 77%, respectively). Positive predictive value was 85% for US and 81% for CT; negative predictive value was 84% for US and 88% for CT. When determining alternative diagnoses, US and CT findings yielded sensitivity of 33% and 50%, respectively (difference not statistically significant). CT scans depicted a small pneumoperitoneum overlooked on plain radiographs and US scans. Six pericolic abscesses were depicted with both techniques; three were depicted with CT only. CONCLUSION: US and CT findings result in similar accuracy for the evaluation of patients suspected of having diverticulitis.

Amino-acid sequence of an alpha-parvalbumin, pI = 4.88, from frog skeletal muscle.

The primary structure of the most basic (pI = 4.88) of the two major parvalbumins from frog skeletal muscle (Rana esculenta) has been determined by partial automatic sequencing of the protein which exhibits a free N terminus, and a study of overlapping peptides obtained by cyanogen bromide cleavage and digestion with trypsin, thermolysin and Armillaria mellea protease. This protein shows the typical structure of an alpha-parvalbumin. Comparison of the primary structure of ion-binding loops of alpha and beta-parvalbumins does not provide a clear-cut explanation of their differences in ion-binding properties.