Counting the ions surrounding nucleic acids.

Nucleic acids are strongly negatively charged, and thus electrostatic interactions-screened by ions in solution-play an important role in governing their ability to fold and participate in biomolecular interactions. The negative charge creates a region, known as the ion atmosphere, in which cation and anion concentrations are perturbed from their bulk values. Ion counting experiments quantify the ion atmosphere by measuring the preferential ion interaction coefficient: the net total number of excess ions above, or below, the number expected due to the bulk concentration. The results of such studies provide important constraints on theories, which typically predict the full three-dimensional distribution of the screening cloud. This article reviews the state of nucleic acid ion counting measurements and critically analyzes their ability to test both analytical and simulation-based models

Effects of Heparin and Enoxaparin on APP Processing and Aβ Production in Primary Cortical Neurons from Tg2576 Mice

BACKGROUND Alzheimer's disease (AD) is caused by accumulation of Aβ, which is produced through sequential cleavage of β-amyloid precursor protein (APP) by the β-site APP cleaving enzyme (BACE1) and γ-secretase. Enoxaparin, a low molecular weight form of the glycosaminoglycan (GAG) heparin, has been reported to lower Aβ plaque deposition and improve cognitive function in AD transgenic mice. METHODOLOGY/PRINCIPAL FINDINGS We examined whether heparin and enoxaparin influence APP processing and inhibit Aβ production in primary cortical cell cultures. Heparin and enoxaparin were incubated with primary cortical cells derived from Tg2576 mice, and the level of APP and proteolytic products of APP (sAPPα, C99, C83 and Aβ) was measured by western blotting. Treatment of the cells with heparin or enoxaparin had no significant effect on the level of total APP. However, both GAGs decreased the level of C99 and C83, and inhibited sAPPα and Aβ secretion. Heparin also decreased the level of β-secretase (BACE1) and α-secretase (ADAM10). In contrast, heparin had no effect on the level of ADAM17. CONCLUSIONS/SIGNIFICANCE The data indicate that heparin and enoxaparin decrease APP processing via both α- and β-secretase pathways. The possibility that GAGs may be beneficial for the treatment of AD needs further study.This work was funded by a project grant (490031) from the National Health and Medical Research Council of Australia (http://www.nhmrc.gov.au). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Pbp1p, a factor interacting with Saccharomyces cerevisiae poly(A)-binding protein, regulates polyadenylation

The poly(A) tail of an mRNA is believed to influence the initiation of translation, and the rate at which the poly(A) tail is removed is thought to determine how fast an mRNA is degraded. One key factor associated with this 3\u27-end structure is the poly(A)-binding protein (Pab1p) encoded by the PAB1 gene in Saccharomyces cerevisiae. In an effort to learn more about the functional role of this protein, we used a two-hybrid screen to determine the factor(s) with which it interacts. We identified five genes encoding factors that specifically interact with the carboxy terminus of Pab1p. Of a total of 44 specific clones identified, PBP1 (for Pab1p-binding protein) was isolated 38 times. Of the putative interacting genes examined, PBP1 promoted the highest level of resistance to 3-aminotriazole (\u3e100 mM) in constructs in which HIS3 was used as a reporter. We determined that a fraction of Pbp1p cosediments with polysomes in sucrose gradients and that its distribution is very similar to that of Pab1p. Disruption of PBP1 showed that it is not essential for viability but can suppress the lethality associated with a PAB1 deletion. The suppression of pab1Delta by pbp1Delta appears to be different from that mediated by other pab1 suppressors, since disruption of PBP1 does not alter translation rates, affect accumulation of ribosomal subunits, change mRNA poly(A) tail lengths, or result in a defect in mRNA decay. Rather, Pbp1p appears to function in the nucleus to promote proper polyadenylation. In the absence of Pbp1p, 3\u27 termini of pre-mRNAs are properly cleaved but lack full-length poly(A) tails. These effects suggest that Pbp1p may act to repress the ability of Pab1p to negatively regulate polyadenylation

Poly(A)-binding proteins: multifunctional scaffolds for the post-transcriptional control of gene expression

Most eukaryotic mRNAs are subject to considerable post-transcriptional modification, including capping, splicing, and polyadenylation. The process of polyadenylation adds a 3' poly(A) tail and provides the mRNA with a binding site for a major class of regulatory factors, the poly(A)-binding proteins (PABPs). These highly conserved polypeptides are found only in eukaryotes; single-celled eukaryotes each have a single PABP, whereas humans have five and Arabidopis has eight. They typically bind poly(A) using one or more RNA-recognition motifs, globular domains common to numerous other eukaryotic RNA-binding proteins. Although they lack catalytic activity, PABPs have several roles in mediating gene expression. Nuclear PABPs are necessary for the synthesis of the poly(A) tail, regulating its ultimate length and stimulating maturation of the mRNA. Association with PABP is also a requirement for some mRNAs to be exported from the nucleus. In the cytoplasm, PABPs facilitate the formation of the 'closed loop' structure of the messenger ribonucleoprotein particle that is crucial for additional PABP activities that promote translation initiation and termination, recycling of ribosomes, and stability of the mRNA. Collectively, these sequential nuclear and cytoplasmic contributions comprise a cycle in which PABPs and the poly(A) tail first create and then eliminate a network of cis- acting interactions that control mRNA function

Dyon Spectrum in Generic N=4 Supersymmetric Z_N Orbifolds

We find the exact spectrum of a class of quarter BPS dyons in a generic N=4 supersymmetric Z_N orbifold of type IIA string theory on K3\times T^2 or T^6. We also find the asymptotic expansion of the statistical entropy to first non-leading order in inverse power of charges and show that it agrees with the entropy of a black hole carrying same set of charges after taking into account the effect of the four derivative Gauss-Bonnet term in the effective action of the theory.Comment: LaTeX file, 39 pages; minor change

Ultrasound Findings of Delayed‐Onset Muscle Soreness

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135570/1/jum201635112517.pd

Linear constraints from generally covariant systems with quadratic constraints

How to make compatible both boundary and gauge conditions for generally covariant theories using the gauge symmetry generated by first class constraints is studied. This approach employs finite gauge transformations in contrast with previous works which use infinitesimal ones. Two kinds of variational principles are taken into account; the first one features non-gauge-invariant actions whereas the second includes fully gauge-invariant actions. Furthermore, it is shown that it is possible to rewrite fully gauge-invariant actions featuring first class constraints quadratic in the momenta into first class constraints linear in the momenta (and homogeneous in some cases) due to the full gauge invariance of their actions. This shows that the gauge symmetry present in generally covariant theories having first class constraints quadratic in the momenta is not of a different kind with respect to the one of theories with first class constraints linear in the momenta if fully gauge-invariant actions are taken into account for the former theories. These ideas are implemented for the parametrized relativistic free particle, parametrized harmonic oscillator, and the SL(2,R) model.Comment: Latex file, revtex4, 18 pages, no figures. This version includes the corrections to many misprints of v1 and also the ones of the published version. The conceptual and technical parts of the paper are not altere