arXiv subjects

Yi-Hsuan Lin

Publications and source records attributed to Yi-Hsuan Lin.

82 records · Page 5Linked to original sources

arXiv2017

Boundary determination of the Lamé moduli for the isotropic elasticity system

We consider the inverse boundary value problem of determining the Lamé moduli of an isotropic, static elasticity equations of system at the boundary from the localized Dirichlet-to-Neumann map. Assuming appropriate local regularity assumptions as weak as possible on the Lamé moduli and on the boundary, we give explicit pointwise reconstruction formulae of the Lamé moduli and their higher order derivatives at the boundary from the localized Dirichlet-to-Neumann map.

math.AP↗

arXiv2017

Phase separation and single-chain compactness of charged disordered proteins are strongly correlated

Liquid-liquid phase separation of intrinsically disordered proteins (IDPs) is a major undergirding factor in the regulated formation of membraneless organelles in the cell. The phase behavior of an IDP is sensitive to its amino acid sequence. Here we apply a recent random-phase-approximation polymer theory to investigate how the tendency for multiple chains of a protein to phase separate, as characterized by the critical temperature $T^*_{\rm cr}$, is related to the protein's single-chain average radius of gyration $\langle R_{\rm g} \rangle$. For a set of sequences containing different permutations of an equal number of positively and negatively charged residues, we found a striking correlation $T^*_{\rm cr}\sim \langle R_{\rm g} \rangle^{-γ}$ with $γ$ as large as $\sim 6.0$, indicating that electrostatic effects have similarly significant impact on promoting single-chain conformational compactness and phase separation. Moreover, $T^*_{\rm cr}\propto -{\rm SCD}$, where SCD is a recently proposed "sequence charge decoration" parameter determined solely by sequence information. Ramifications of our findings for deciphering the sequence dependence of IDP phase separation are discussed.

q-bio.BM↗

arXiv2016

Nearly cloaking for the elasticity system with residual stress

The nearly cloaking via transformation optics approach for the isotropic elastic wave fields is considered. This work extends the study of the nearly cloaking scheme to the elasticity system with residual stress in \mathbb{R}^{N} for N=2,3, which is an anisotropic elasticity system. It is worth to mention that there are no minor symmetric properties for the elastic tensor with residual stress and this system is invariant under a coordinate transformation. Therefore, we think the elasticity system residual stress model is more natural than the isotropic elasticity system in designing the elastic cloaking medium in the physical sense. In addition, the main difficulty of treating this problem lies in the fact that there are no layer potential theory for the residual stress system. Instead, we will derive suitable elliptic estimates for the elasticity system residual stress by comparing with the Lamé system to achieve desired results.

math.AP↗

arXiv2016

RBPBind: Quantitative prediction of Protein-RNA Interactions

Summary: We introduce RBPBind, a web-based tool for the quantitative prediction of RNA-protein interactions. Given a user-specified RNA and a protein selected from a set of several common RNA-binding proteins, RBPBind computes the binding curve and effective binding constant of the reaction in question. The server also computes the probability that, at a given concentration of protein, a protein molecule will bind to any particular nucleotide along the RNA. The software for RBPBind is adapted from the Vienna RNA package, whose source code has been modified to accommodate the effects of single stranded RNA binding proteins. RBPBind thus fully incorporates the effect of RNA secondary structure on protein-RNA interactions. Availability: Our web server is available at http://bioserv.mps.ohio-state.edu/RBPBind

q-bio.BM↗

arXiv2016

Random-phase-approximation theory for sequence-dependent, biologically functional liquid-liquid phase separation of intrinsically disordered proteins

Intrinsically disordered proteins (IDPs) are typically low in nonpolar/hydrophobic but relatively high in polar, charged, and aromatic amino acid compositions. Some IDPs undergo liquid-liquid phase separation in the aqueous milieu of the living cell. The resulting phase with enhanced IDP concentration can function as a major component of membraneless organelles that, by creating their own IDP-rich microenvironments, stimulate critical biological functions. IDP phase behaviors are governed by their amino acid sequences. To make progress in understanding this sequence-phase relationship, we report further advances in a recently introduced application of random-phase-approximation (RPA) heteropolymer theory to account for sequence-specific electrostatics in IDP phase separation. Here we examine computed variations in phase behavior with respect to block length and charge density of model polyampholytes of alternating equal-length charge blocks to gain insight into trends observed in IDP phase separation. As a real-life example, the theory is applied to rationalize/predict binodal and spinodal phase behaviors of the 236-residue N-terminal disordered region of RNA helicase Ddx4 and its charge-scrambled mutant for which experimental data are available. Fundamental differences are noted between the phase diagrams predicted by RPA and those predicted by mean-field Flory-Huggins and Overbeek-Voorn/Debye-Hückel theories. In the RPA context, a physically plausible dependence of relative permittivity on protein concentration can produce a cooperative effect in favor of IDP-IDP attraction and thus a significant increased tendency to phase separate. Ramifications of these findings for future development of IDP phase separation theory are discussed.

q-bio.BM↗

arXiv2016

Sequence-specific polyampholyte phase separation in membraneless organelles

Liquid-liquid phase separation of charge/aromatic-enriched intrinsically disordered proteins (IDPs) is critical in the biological function of membraneless organelles. Much of the physics of this recent discovery remains to be elucidated. Here we present a theory in the random phase approximation to account for electrostatic effects in polyampholyte phase separations, yielding predictions consistent with recent experiments on the IDP Ddx4. The theory is applicable to any charge pattern and thus provides a general analytical framework for studying sequence dependence of IDP phase separation.

q-bio.BM↗

arXiv2015

The enclosure method for the anisotropic Maxwell system

We develop an enclosure-type reconstruction scheme to identify penetrable and impenetrable obstacles in electromagnetic field with anisotropic medium in \mathbb{R}^{3}. The main difficulty in treating this problem lies in the fact that there are so far no complex geometrical optics solutions available for the Maxwell's equation with anisotropic medium in \mathbb{R}^{3}. Instead, we derive and use another type of special solutions called oscillating-decaying solutions. To justify this scheme, we use Meyers' L^{p} estimate, for the Maxwell system, to compare the integrals coming from oscillating-decaying solutions and those from the reflected solutions.

math.AP↗

arXiv2014

RNA structure generates natural cooperativity between single-stranded RNA binding proteins targeting 5' and 3'UTRs

In post-transcriptional regulation, an mRNA molecule is bound by many proteins and/or miRNAs to modulate its function. To enable combinatorial gene regulation, these binding partners of an RNA must communicate with each other, exhibiting cooperativity. Even in the absence of direct physical interactions between the binding partners, such cooperativity can be mediated through RNA secondary structures, since they affect the accessibility of the binding sites. Here we propose a quantitative measure of this structure-mediated cooperativity that can be numerically calculated for an arbitrary RNA sequence. Focusing on an RNA with two binding sites, we derive a characteristic difference of free energy differences, i.e. ΔΔG, as a measure of the effect of the occupancy of one binding site on the binding strength of another. We apply this measure to a large number of human and C. elegans mRNAs, and find that structure-mediated cooperativity is a generic feature. Interestingly, this cooperativity not only affects binding sites in close proximity along the sequence but also configurations in which one binding site is located in the 5'UTR and the other is located in the 3'UTR of the mRNA. Furthermore, we find that this end-to-end cooperativity is determined by the UTR sequences while the sequences of the coding regions are irrelevant.

q-bio.BM↗

arXiv2014

Reconstruction of penetrable obstacles in the anisotropic acoustic scattering

We develop reconstruction schemes to determine penetrable obstacles in a region of \mathbb{R}^{2} or \mathbb{R}^{3} and we consider anisotropic elliptic equations. This algorithm uses oscillating-decaying solutions to the equation. We apply the oscillating-decaying solutions and the Runge approximation property to the inverse problem of identifying an inclusion in an anisotropic elliptic differential equation.

math.AP↗

arXiv2013

Interplay between single-stranded binding proteins on RNA secondary structure

RNA protein interactions control the fate of cellular RNAs and play an important role in gene regulation. An interdependency between such interactions allows for the implementation of logic functions in gene regulation. We investigate the interplay between RNA binding partners in the context of the statistical physics of RNA secondary structure, and define a linear correlation function between the two partners as a measurement of the interdependency of their binding events. We demonstrate the emergence of a long-range power-law behavior of this linear correlation function. This suggests RNA secondary structure driven interdependency between binding sites as a general mechanism for combinatorial post-transcriptional gene regulation.

q-bio.BM↗