Cosmic Birefringence from the Planck Data Release 4.

We search for the signature of parity-violating physics in the cosmic microwave background, called cosmic birefringence, using the Planck data release 4. We initially find a birefringence angle of ß=0.30°±0.11° (68% C.L.) for nearly full-sky data. The values of ß decrease as we enlarge the Galactic mask, which can be interpreted as the effect of polarized foreground emission. Two independent ways to model this effect are used to mitigate the systematic impact on ß for different sky fractions. We choose not to assign cosmological significance to the measured value of ß until we improve our knowledge of the foreground polarization.

Model-independent test for scale-dependent non-Gaussianities in the cosmic microwave background.

We present a model-independent method to test for scale-dependent non-Gaussianities in combination with scaling indices as test statistics. Therefore, surrogate data sets are generated, in which the power spectrum of the original data is preserved, while the higher order correlations are partly randomized by applying a scale-dependent shuffling procedure to the Fourier phases. We apply this method to the Wilkinson Microwave Anisotropy Probe data of the cosmic microwave background and find signatures for non-Gaussianities on large scales. Further tests are required to elucidate the origin of the detected anomalies.

Energy transfer as a probe of protein dynamics in the proteins transferrin and calmodulin.

We have initiated an investigation into the usefulness of fluorescence energy transfer in probing protein dynamics. Our analysis involves measuring the energy transfer efficiency while perturbing the protein conformational equilibrium with heat. As the temperature increases, the amplitudes of vibrations increase, and fluorescence energy transfer should also increase if the donor and acceptor are in a flexible region of the protein. A theoretical analysis developed by Somogyi and co-workers for the temperature dependence of dipole-dipole energy transfer (Somogyi, B., J. Matko, S. Papp, J. Hevessey, G. R. Welch, and S. Damjanovich. 1984. Biochemistry. 23:3403-3411) was tested by the authors in one protein system. Energy transfer from tryptophan to a pyridoxamine derivatized side group in RNase increased 40% over 25 degrees C. Here we report further testing of this model in two additional protein systems: calmodulin, a calcium activated regulatory protein, and transferrin, a blood serum iron shuttle. Our studies show a slight differential sensitivity of the transfer efficiency to heat for the two systems. Normalized energy transfer over 6.5 A in calmodulin from a tyrosine donor to a Tb(III) acceptor increases 40% from 295 to 320 K. Normalized energy transfer over 42 A in transferrin from a Tb(III) donor to an Fe(III) acceptor increases 35% over the same temperature range. Whereas these results demonstrate that thermally induced fluctuations do increase energy transfer as predicted by Somogyi, they also appear rather insensitive to the nature of the protein host environment. In contrast to the Förster processes examined above, energy transfer over very short distances has shown an anomalously high temperature dependence.

Studies on the posttranslational migration and processing of thyroglobulin: use of inhibitors and evaluation of the role of phosphorylation.

A study of the synthesis and migration of thyroglobulin has been carried out by the incubation of calf thyroid slices in the presence of [14C]leucine followed by the separation of intracellular compartments from the colloid by differential and density gradient centrifugation. The effect of inhibitors on these processes has been examined and, moreover, the importance of phosphorylation as an additional posttranslational modification of thyroglobulin has been explored through the characterization of the radiolabeled constituents formed after slice incubation with [32P]phosphate. Movement of newly synthesized thyroglobulin through the cellular compartments was found to be rapid; after a 15-min incubation with [14C]leucine a substantial portion (30%) of the immunoprecipitable radiolabeled thyroglobulin was already present in the colloid (soluble) fraction. Incubations performed after brief pretreatment with colchicine resulted in the accumulation of radiolabeled thyroglobulin in the colloid, suggesting that in the uninhibited state a large proportion of the newly synthesized thyroglobulin is reabsorbed and degraded. Vinblastine and cytochalasin B had similar but smaller effects. More prolonged preincubation with colchicine led to a substantial decrease in thyroglobulin formation, suggesting that the synthetic and reabsorptive steps have different degrees of sensitivity to agents affecting the microtubule-microfilament apparatus. Uptake of radiolabeled thyroglobulin from the colloid was also inhibited by chloroquine, which caused a block in the lysosomal degradation of this protein but did not affect its synthesis. The sodium dodecyl sulfate-polyacrylamide gel electrophoretic pattern of immunoprecipitated thyroglobulin prepared after incubation of slices with radiolabeled substrates was that of a doublet. When, however, the incubation of either calf or rat thyroid segments was terminated by boiling in sodium dodecyl sulfate-2-mercaptoethanol, one band predominated, corresponding to the slowest of the immunoprecipitated components; it is suggested that the thyroglobulin molecule contains regions of great protease sensitivity which are responsible for the heterogeneous high mol wt pattern usually seen, but that physiologically this peptide trimming does not occur before secretion from the cell. Incubation of thyroid slices with [32P]phosphate led to incorporation of label into immunoprecipitable thyroglobulin associated with both the intracellular and colloid compartments.(ABSTRACT TRUNCATED AT 400 WORDS)