822 research outputs found
SAF-A mutants disrupt chromatin structure through dominant negative effects on RNAs associated with chromatin
Here we provide a brief review of relevant background before presenting results of our investigation into the interplay between scaffold attachment factor A (SAF-A), chromatin-associated RNAs, and DNA condensation. SAF-A, also termed heterogenous nuclear protein U (hnRNP U), is a ubiquitous nuclear scaffold protein that was implicated in XIST RNA localization to the inactive X-chromosome (Xi) but also reported to maintain open DNA packaging in euchromatin. Here we use several means to perturb SAF-A and examine potential impacts on the broad association of RNAs on euchromatin, and on chromatin compaction. SAF-A has an N-terminal DNA binding domain and C-terminal RNA binding domain, and a prominent model has been that the protein provides a single-molecule bridge between XIST RNA and chromatin. Here analysis of the impact of SAF-A on broad RNA-chromatin interactions indicate greater biological complexity. We focus on SAF-A\u27s role with repeat-rich C0T-1 hnRNA (repeat-rich heterogeneous nuclear RNA), shown recently to comprise mostly intronic sequences of pre-mRNAs and diverse long non-coding RNAs (lncRNAs). Our results show that SAF-A mutants cause dramatic changes to cytological chromatin condensation through dominant negative effects on C0T-1 RNA\u27s association with euchromatin, and likely other nuclear scaffold factors. In contrast, depletion of SAF-A by RNA interference (RNAi) had no discernible impact on C0T-1 RNA, nor did it cause similarly marked chromatin changes as did three different SAF-A mutations. Overall results support the concept that repeat-rich, chromatin-associated RNAs interact with multiple RNA binding proteins (RBPs) in a complex dynamic meshwork that is integral to larger-scale chromatin architecture and collectively influences cytological-scale DNA condensation
Thermodynamics of Binding by Calmodulin Correlates with Target Peptide α-Helical Propensity
In this work, we have examined contributions to the thermodynamics of calmodulin (CaM) binding from the intrinsic propensity for target peptides to adopt an α-helical conformation. CaM target sequences are thought to commonly reside in disordered regions within proteins. Using the ability of TFE to induce α-helical structure as a proxy, the six peptides studied range from having almost no propensity to adopt α-helical structure through to a very high propensity. This despite all six peptides having similar CaM-binding affinities. Our data indicate there is some correlation between the deduced propensities and the thermodynamics of CaM binding. This finding implies that molecular recognition features, such as CaM target sequences, may possess a broad range of propensities to adopt local structure. Given that these peptides bind to CaM with similar affinities, the data suggest that having a higher propensity to adopt α-helical structure does not necessarily result in tighter binding, and that the mechanism of CaM binding is very dependent on the nature of the substrate sequence
The quantum non-linear Schrodinger model with point-like defect
We establish a family of point-like impurities which preserve the quantum
integrability of the non-linear Schrodinger model in 1+1 space-time dimensions.
We briefly describe the construction of the exact second quantized solution of
this model in terms of an appropriate reflection-transmission algebra. The
basic physical properties of the solution, including the space-time symmetry of
the bulk scattering matrix, are also discussed.Comment: Comments on the integrability and the impurity free limit adde
Graphical representation of the partition function for a 1-D delta-function Bose gas
One-dimensional repulsive delta-function bose system is studied. By only
using the Bethe ansatz equation, n-particle partition functions are exactly
calculated. From this expression for the n-particle partition function, the
n-particle cluster integral is derived. The results completely agree with those
of the thermal Bethe ansatz (TBA). This directly proves the validity of the
TBA. The theory of partitions and graphs is used to simplify the discussion.Comment: 15 page
Spontaneous symmetry breaking in the non-linear Schrodinger hierarchy with defect
We introduce and solve the one-dimensional quantum non-linear Schrodinger
(NLS) equation for an N-component field defined on the real line with a defect
sitting at the origin. The quantum solution is constructed using the quantum
inverse scattering method based on the concept of Reflection-Transmission (RT)
algebras recently introduced. The symmetry of the model is generated by the
reflection and transmission defect generators defining a defect subalgebra. We
classify all the corresponding reflection and transmission matrices. This
provides the possible boundary conditions obeyed by the canonical field and we
compute these boundary conditions explicitly. Finally, we exhibit a phenomenon
of spontaneous symmetry breaking induced by the defect and identify the
unbroken generators as well as the exact remaining symmetry.Comment: discussion on symmetry breaking has been improved and examples adde
Partisan Asymmetries in Online Political Activity
We examine partisan differences in the behavior, communication patterns and
social interactions of more than 18,000 politically-active Twitter users to
produce evidence that points to changing levels of partisan engagement with the
American online political landscape. Analysis of a network defined by the
communication activity of these users in proximity to the 2010 midterm
congressional elections reveals a highly segregated, well clustered partisan
community structure. Using cluster membership as a high-fidelity (87% accuracy)
proxy for political affiliation, we characterize a wide range of differences in
the behavior, communication and social connectivity of left- and right-leaning
Twitter users. We find that in contrast to the online political dynamics of the
2008 campaign, right-leaning Twitter users exhibit greater levels of political
activity, a more tightly interconnected social structure, and a communication
network topology that facilitates the rapid and broad dissemination of
political information.Comment: 17 pages, 10 figures, 6 table
Local correlations in a strongly interacting 1D Bose gas
We develop an analytical method for calculating local correlations in
strongly interacting 1D Bose gases, based on the exactly solvable Lieb-Liniger
model. The results are obtained at zero and finite temperatures. They describe
the interaction-induced reduction of local many-body correlation functions and
can be used for achieving and identifying the strong-coupling Tonks-Girardeau
regime in experiments with cold Bose gases in the 1D regime.Comment: 8 pages, REVTeX4, published in the New Journal of Physic
Universal correlations of trapped one-dimensional impenetrable bosons
We calculate the asymptotic behaviour of the one body density matrix of
one-dimensional impenetrable bosons in finite size geometries. Our approach is
based on a modification of the Replica Method from the theory of disordered
systems. We obtain explicit expressions for oscillating terms, similar to
fermionic Friedel oscillations. These terms are universal and originate from
the strong short-range correlations between bosons in one dimension.Comment: 18 pages, 3 figures. Published versio
Study experiences and the post-study intentions of female international undergraduate students
The number of female international students is increasing exponentially, and whilst international study may engender many benefits and challenges, little is known about their intentions once they complete their studies. This article reviews the literature on female international students with specific focus on exploring post-study intentions. A scoping review of four electronic databases was completed. After applying criteria to determine suitability, 30 publications were included in the final review. Analysis revealed three key foci: (1) the rationale for studying internationally; (2) the study experience; and (3) post-study intentions. The literature illustrates that an international study experience has the potential to be a powerful transformative opportunity if positive experiences outweigh the negatives. The findings also indicate that the post-study intentions of female international students are under-researched. The article contends that attention should be given to supporting the needs of this group, with a view to maximizing post-study opportunities
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