The protein Ran is a small GTP-binding protein that binds to two types of effector inside the cell: Ran-binding proteins, which have a role in terminating export processes from the nucleus to the cytoplasm, and importin-beta-like molecules that bind cargo proteins during nuclear transport. The Ran-binding domain is a conserved sequence motif found in several proteins that participate in these transport processes. The Ran-binding protein RanBP2 contains four of these domains and constitutes a large part of the cytoplasmic fibrils that extend from the nuclear-pore complex. The structure of Ran bound to a non-hydrolysable GTP analogue (Ran x GppNHp) in complex with the first Ran-binding domain (RanBD1) of human RanBP2 reveals not only that RanBD1 has a pleckstrin-homology domain fold, but also that the switch-I region of Ran x GppNHp resembles the canonical Ras GppNHp structure and that the carboxy terminus of Ran is wrapped around RanBD1, contacting a basic patch on RanBD1 through its acidic end. This molecular 'embrace' enables RanBDs to sequester the Ran carboxy terminus, triggering the dissociation of Ran x GTP from importin-beta-related transport factors and facilitating GTP hydrolysis by the GTPase-activating protein ranGAP. Such a mechanism represents a new type of switch mechanism and regulatory protein-protein interaction for a Ras-related protein.

Increasing attention has been paid to developability assessment with the understanding that thorough evaluation of monoclonal antibody lead candidates at an early stage can avoid delays during late-stage development. The concept of developability is based on the knowledge gained from the successful development of approximately 80 marketed antibody and Fc-fusion protein drug products and from the lessons learned from many failed development programs over the last three decades. Here, we reviewed antibody quality attributes that are critical to development and traditional and state-of-the-art analytical methods to monitor those attributes. Based on our collective experiences, a practical workflow is proposed as a best practice for developability assessment including in silico evaluation, extended characterization and forced degradation using appropriate analytical methods that allow characterization with limited material consumption and fast turnaround time.

Although extensive efforts have been devoted to understanding electronic transport in conjugated polymers, little is known about their ionic conduction characteristics in relation to polymer chemistry, processing, and morphology. This work presents a combined computational and experimental study on morphology and ion transport in thin-film blends of polythiophene derivatives bearing oligoethylene glycol side-chains and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Using molecular dynamics (MD) simulation, we show that in the amorphous phase, the polythiophene derivative P3MEET bearing oligoethylene glycol side-chains with oxygen directly attached to the thiophene rings possesses lower Li + ionic conductivity compared to its analog P3MEEMT that has a methyl spacer between the oxygen and the thiophene rings. Structural characterization of P3MEET and P3MEEMT thin film upon blending with LiTFSI indicates that adding LiTFSI expands the side-chain domains of the polymer crystallites and reduces the total degree of crystallinity at the same time. Moreover, LiTFSI is found to infiltrate both the amorphous and crystalline regimes at low concentrations but preferably resides in the amorphous domain at high LiTFSI concentrations. Ionic transport measured by electrochemical impedance spectroscopy in both P3MEET-and P3MEEMT-LiTFSI thin films is found to occur predominately in the amorphous domain, and ionic conductivity in P3MEEMT-LiTFSI is always higher than in P3MEET-LiTFSI samples, consistent with predictions from MD simulations. Our work provides a platform to predict and study the influence of polymer chemistry on the ionic conductivity of conjugated polymers.

Forced degradation studies have become integral to the development of recombinant monoclonal antibody therapeutics by serving a variety of objectives from early stage manufacturability evaluation to supporting comparability assessments both pre- and post- marketing approval. This review summarizes the regulatory guidance scattered throughout different documents to highlight the expectations from various agencies such as the Food and Drug Administration and European Medicines Agency. The various purposes for forced degradation studies, commonly used conditions and the major degradation pathways under each condition are also discussed.

A second order phase transition for the three dimensional Gross-Neveu model is established for one fermion species N = 1. This transition breaks a parity-like discrete symmetry. It constitutes its peculiar universality class with critical exponent ν = 0.63 and scalar and fermionic anomalous dimension ησ = 0.31 and η ψ = 0.11, respectively. We also compute critical exponents for other N . Our results are based on exact renormalization group equations.An understanding of systems with many fermionic degrees of freedom is one of the big challenges in statistical physics. Due to the anticommuting nature of the variables numerical simulations are not straightforward-analytical methods are crucially needed. One typically has to solve a functional integral for a d dimensional system with Grassmann variables. Approximate solutions for "test models" would be of great value. The Gross-Neveu (GN) model [1] is one of the simplest fermionic models. In three dimensions a discrete symmetry forbids a mass term unless it is spontaneously broken. In the symmetric phase the GN model is therefore a realization of a statistical system of gapless fermions. For a large number N of fermion species it is known [2-5] that a second order phase transition separates the symmetric phase from an ordered phase where the symmetry is spontaneously broken and the fermions become massive. Using methods based on an exact renormalization group equation [6] a second order transition for N ≥ 2 was confirmed. We know, however, of no previous work which clarifies the existence and nature of the phase transition in the simplest model with only one fermion species. The model with one fermion species is inaccessible to lattice simulations due to the fermion doubling problem and the 1/N expansion is not expected to give reasonable results for N = 1. The case N = 1 is also of special interest since an order parameter ψ j ψ j = 0 leads to a ground state which does not admit any discrete symmetry involving the reflection of all coordinates, in contrast to the models with N ≥ 2.In this letter we improve the exact renormalization group approach and establish a second order phase transition for N = 1. We also compute the critical exponents. This is important beyond a possible relevance for real physical systems: the GN model constitutes a peculiar universality class due to the presence of massless fermions at the critical point. Just as the O(N )-Heisenberg models for bosons, the GN model could in the future become a benchmark for our understanding of critical systems in presence of fermions.The GN model describes N fermionic fields with local quartic interaction. Here ψj, j = 1...N , are irreducible representations of the group O(d) including parity reflections, i. e. 2 d/2 component Dirac spinors for d even and 2 (d−1)/2 for d odd.The classical Euclidean actionis symmetric under a coordinate reflection ψ(x) → −ψ(−x) ,ψ(x) →ψ(−x). (We note that ψ andψ are independent variables in an Eucidean formulation.) A nonvanishing expectation value ofψj ψ j spontaneously bre...

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The cytoplasmic disassembly of Ran.GTP.importin and Ran.GTP.exportin. cargo complexes is an essential step in the corresponding nuclear import and export cycles. It has previously been shown that such disassembly can be mediated by RanBP1 in the presence of RanGAP. The nuclear pore complex protein RanBP2 (Nup358) contains four Ran-binding domains (RanBDi) that might function like RanBP1. We used biophysical assays based on fluorescence-labeled probes and on surface plasmon resonance to investigate the dynamic interplay of Ran in its GDP- and GTP-complexed states with RanBDis and with importin-beta. We show that RanBP1 and the four RanBDis from RanBP2 have comparable affinities for Ran.GTP (10(8)-10(9) M(-1)). Deletion of Ran's C-terminal (211)DEDDDL(216) sequence weakens the interaction of Ran.GTP with RanBPis approximately 2000-fold, but accelerates the association of Ran.GTP with importin-beta 10-fold. Importin-beta binds Ran.GTP with a moderate rate, but attains a high affinity for Ran (K(D) = 140 pM) via an extremely low dissociation rate of 10(-5) s(-)(1). Association with Ran is accelerated 3-fold in the presence of RanBP1, which presumably prevents steric hindrance caused by the Ran C-terminus. In addition, we show that the RanBDis of RanBP2 are full equivalents of RanBP1 in that they also costimulate RanGAP-catalyzed GTP hydrolysis in Ran and relieve the GTPase block in a Ran.GTP.transportin complex. Our data suggest that the C-terminus of Ran functions like a loose tether in Ran.GTP complexes of importins or exportins that exit the nucleus. This flag is then recognized by the multiple RanBDis at or near the nuclear pore complex, allowing efficient disassembly of these Ran.GTP complexes.