The study investigated the effect of the thylakoid membrane lipids monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulphoquinovosyldiacylglycerol (SQDG) and ...phosphatidylglycerol (PG) on the structure of two algal light‐harvesting complexes (LHCs). In contrast to higher plants whose thylakoid membranes are characterized by an enrichment of the neutral galactolipids MGDG and DGDG, both the green alga Mantoniella squamata and the centric diatom Thalassiosira pseudonana contain membranes with a high content of the negatively charged lipids SQDG and PG. The algal thylakoids do not show the typical grana–stroma differentiation of higher plants but a regular arrangement. To analyze the effect of the membrane lipids, the fucoxanthin chlorophyll protein (FCP) complex of T. pseudonana and the LHC of M. squamata (MLHC) were prepared by successive cation precipitation using Triton X‐100 as detergent. With this method, it is possible to isolate LHCs with a reduced amount of associated lipids in an aggregated state. The results from 77 K fluorescence and photon correlation spectroscopy show that neither the neutral galactolipids nor the negatively charged lipids are able to significantly alter the aggregation state of the FCP or the MLHC. This is in contrast to higher plants where SQDG and PG lead to a strong disaggregation of the LHCII whereas MGDG and DGDG induce the formation of large macroaggregates. The results indicate that LHCs which are integrated into thylakoid membranes with a high amount of negatively charged lipids and a regular arrangement are less sensitive to lipid‐induced structural alterations than their counterparts in membranes enriched in neutral lipids with a grana–stroma differentiation.
We investigate the complexity of basic symmetry breaking problems in multihop radio networks with multiple communication channels. We assume a network of synchronous nodes, where each node can be ...awakened individually in an arbitrary time slot by an adversary. In each time slot, each awake node can transmit or listen (without collision detection) on one of multiple available shared channels. The network topology is assumed to satisfy a natural generalization of the well-known unit disk graph model.
We study the classic wake-up problem and a new variant we call active wake-up. For the former we prove a lower bound that shows the advantage of multiple channels disappears for any network of more than one hop. For the active version however, we describe an algorithm that outperforms any single channel solution. We then extend this algorithm to compute a constant approximation for the minimum dominating set (MDS) problem in the same time bound. Combined, these results for the increasingly relevant multi-channel model show that it is often possible to leverage channel diversity to beat classic lower bounds, but not always.
A good imitation: Aryl‐1‐indanyl ketones are found to be highly efficient, reversible, cell‐penetrating inhibitors of the human peptidyl prolyl cis/trans isomerase Pin1. Owing to their structure 1, ...they are assumed to mimic the transition state 2 of the enzymatically catalyzed rotation about the imidic peptide bond preceding a proline residue.
The parvulin family of peptidyl-prolyl
cis/trans isomerases (PPIases) catalyzes the
cis/trans isomerization of the peptide bonds preceding Pro residues. Eukaryotic parvulin-type PPIases have been ...shown to be involved in cell proliferation and cell cycle progression. Here we present the biochemical and molecular characterization of a novel multi-domain parvulin-type PPIase from the human pathogenic
Trypanosoma cruzi, annotated as
TcPar45. Like most other parvulins, Par45 has an N-terminal extension, but, in contrast to human Pin1, it contains a forkhead-associated domain (FHA) instead of a WW domain at the N-terminal end. Par45 shows a strong preference for a substrate with the basic Arg residue preceding Pro (Suc-Ala-Arg-Pro-Phe-NH-Np:
k
cat/
K
M
=
97.1 /M/s), like that found for human Par14. In contrast to human Pin1, but similarly to Par14, Par45 does not accelerate the
cis/trans interconversion of acidic substrates containing Glu-Pro bonds. It is preferentially located in the parasite nucleus. Single RNA interference (RNAi)-mediated knock-down showed that there was a growth inhibition in procyclic
Trypanosoma brucei cells. These results identify Par45 as a phosphorylation-independent parvulin required for normal cell proliferation in a unicellular eukaryotic cell.
Parvulins are a conserved group of peptidyl-prolyl
cis/
trans isomerases (PPIases) that catalyze the
cis/
trans isomerization of proline-preceding peptide bonds. Parvulin-class PPIases are ...structurally unrelated to cyclophilins and FK506-binding proteins that are defined as receptors for immunosuppressive drugs. In
Trypanosoma cruzi we identified parvulin
TcPIN1 as a homolog of the human hPin1 PPIase. The 117 amino acids of the
TcPIN1 display 40% identity with the catalytic core of hPin1 and exhibit prolyl
cis/
trans isomerase activity.
TcPIN1 lacks the WW domain at the N-terminus, and is able to rescue the temperature-sensitive phenotype on a mutation in the
Saccharomyces cerevisiae hPin1 homolog, ESS1/PTF1. Western blot analysis revealed that the enzyme was present both in dividing and non-dividing forms of
T. cruzi. In epimastigote cells neither cell growth kinetics nor cell morphology was affected by the overexpression of the small parvulin
TcPIN1. These results suggest the occurrence of a supplementary conserved level of post-translational control in trypanosomatids.
Daum et al. PODC'13 presented an algorithm that computes a maximal independent set (MIS) within \(O(\log^2 n/F+\log n \mathrm{polyloglog} n)\) rounds in an \(n\)-node multichannel radio network with ...\(F\) communication channels. The paper uses a multichannel variant of the standard graph-based radio network model without collision detection and it assumes that the network graph is a polynomially bounded independence graph (BIG), a natural combinatorial generalization of well-known geographic families. The upper bound of that paper is known to be optimal up to a polyloglog factor. In this paper, we adapt algorithm and analysis to improve the result in two ways. Mainly, we get rid of the polyloglog factor in the runtime and we thus obtain an asymptotically optimal multichannel radio network MIS algorithm. In addition, our new analysis allows to generalize the class of graphs from those with polynomially bounded local independence to graphs where the local independence is bounded by an arbitrary function of the neighborhood radius.
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