Rational Structure‐Based Design of Bright GFP‐Based Complexes with Tunable Dimerization

Fluorescent proteins are transformative tools; thus, any brightness increase is a welcome improvement. We invented the “vGFP strategy” based on structural analysis of GFP bound to a single‐domain antibody, predicting tunable dimerization, enhanced brightness (ca. 50 %), and improved pH resistance. We verified all of these predictions using biochemistry, crystallography, and single‐molecule studies. We applied the vsfGFP proteins in three diverse scenarios: single‐step immunofluorescence in vitro (3× brighter due to dimerization); expression in bacteria and human cells in vivo (1.5× brighter); and protein fusions showing better pH resistance in human cells in vivo. The vGFP strategy thus allows upgrading of existing applications, is applicable to other fluorescent proteins, and suggests a method for tuning dimerization of arbitrary proteins and optimizing protein properties in general.     

Switching time optimization for a PDE constrained optimal control problem of bang-bang type

We consider a well-known optimal control problem subject to the heat equation where the control variable appears linearly as a boundary control in a Robin type boundary condition. Here, we describe an alternative numerical method to solve the problem by a switching time optimization approach. The method has so far been successfully applied to ODE problems and offers several advantages according to second order sufficient conditions and sensitivity analysis. We discuss theoretical aspects and present numerical results to illustrate the effectiveness of the method. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

A note on the initial identification of scalar component models

This paper solves an open theoretical question in the identification stage of Scalar Component Models, posed initially by Tiao and Tsay and noted by several researchers, specifically as it refers to the choice of a certain parameter present in the process and which they denote h. The theoretical concept of sure overall orders, instead of the so-called overall orders, is useful in addressing this issue. Using simple examples, we justify the need for our theoretical results. Moreover, we use a Ranks Table and its properties to complement the SCM identification stage with interesting theoretical information without adding significant calculations to the procedure initially proposed by Tiao and Tsay.     

Deuterium‐induced isotope effects on the 13C chemical shifts of α‐d‐glucose pentaacetate

1,2,3,4,6‐Penta‐O‐acetyl‐α‐d ‐glucopyranose and the corresponding [1‐²H], [2‐²H], [3‐²H], [4‐²H], [5‐²H], and [6,6‐²H₂]‐labeled compounds were prepared for measuring deuterium/hydrogen‐induced effects on ¹³C chemical shift ⁿΔ (DHIECS) values. A conformational analysis of the nondeuterated compound was achieved using density functional theory (DFT) molecular models that allowed calculation of several structural properties as well as Boltzmann‐averaged ¹³C NMR chemical shifts by using the gauge‐including atomic orbital method. It was found that the DFT‐calculated C–H bond lengths correlate with ¹Δ DHIECS. Copyright © 2013 John Wiley & Sons, Ltd.     

Evaluation of piezoelectric poly(vinylidene fluoride) polymers for use in space environments. I. Temperature limitations

Smart materials, such as thin‐film piezoelectric polymers, are interesting for potential applications on Gossamer spacecraft. This investigation aims to predict the performance and long‐term stability of the piezoelectric properties of poly(vinylidene fluoride) (PVDF) and its copolymers under conditions simulating the low‐Earth‐orbit environment. To examine the effects of temperature on the piezoelectric properties of PVDF, poly(vinylidenefluoride‐co‐trifluoroethylene), and poly(vinylidenefluoride‐co‐hexafluoropropylene), the d₃₃ piezoelectric coefficients were measured up to 160 °C, and the electric displacement/electric field (D–E) hysteresis loops were measured from ?80 to +110 °C. The room‐temperature d₃₃ coefficient of PVDF homopolymer films, annealed at 50, 80, and 125 °C, dropped rapidly within a few days of thermal exposure and then remained unchanged. In contrast, the TrFE copolymer exhibited greater thermal stability than the homopolymer, with d₃₃ remaining almost unchanged up to 125 °C. The HFP copolymer exhibited poor retention of d₃₃ at temperatures above 80 °C. In situ D–E loop measurements from ?80 to +110 °C showed that the remanent polarization of the TrFE copolymer was more stable than that of the PVDF homopolymer. D–E hysteresis loop and d₃₃ results were also compared with the deflection of the PVDF homopolymer and TrFE copolymer bimorphs tested over a wide temperature range. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1310‐1320, 2005     

New bromotyrosine alkaloids from the marine sponge Psammaplysilla purpurea

Seven new bromotyrosine alkaloids Purpurealidin A, B, C, D, F, G, H and the known compounds Purealidin Q, Purpurealidin E, 16-Debromoaplysamine-4 and Purpuramine I have been isolated from the marine sponge Psammaplysilla purpurea. Their structure was elucidated on the basis of detailed 1D, 2D NMR and MS spectroscopic data. Purpurealidin B, 16-Debromoaplysamine-4 and Purpuramine I exhibited in vitro antimicrobial activities against E. coli, S. aureus, and V. cholerae. In addition, Purpurealidin B and 16-Debromoaplysamine-4 were also active against Shigella flexineri and Salmonella typhi while Purealidin Q was bactericidal only against Salmonella typhi.     

Lifetime predictions for semi-crystalline cable insulation materials: I. Mechanical properties and oxygen consumption measurements on EPR materials

Long-term accelerated aging studies (up to 7 years of aging) were conducted on four typical EPR materials used as cable insulation in nuclear power plant safety applications with the goal of establishing lifetime estimates at typical aging conditions of ∼50 °C. The four materials showed slow to moderate changes in mechanical properties (tensile elongation) until just before failure where abrupt changes occurred (so-called “induction-time” behavior). Time-temperature superposition was applied to derive shift factors and probe for Arrhenius behavior. Three of the materials showed reasonable time-temperature superposition with the empirically derived shift factors yielding an approximate Arrhenius dependence on temperature. Since the elongation results for the fourth material could not be successfully superposed, consistency with Arrhenius assumptions was impossible. For this material the early part of the mechanical degradation appeared to have an Arrhenius activation energy E_a of ∼100 kJ/mol (24 kcal/mol) whereas the post-induction degradation data had an E_a of ∼128 kJ/mol. Oxygen consumption measurements were used to confirm the 100 kJ/mol E_a found from early-time elongation results and to show that the chemistry responsible before the induction time is likely to remain unchanged down to 50 °C. Reasonable extrapolations of the induction-time results indicated 50 °C lifetimes exceeding 300 years for all four materials.     

Oxidation profiles of thermally aged nitrile rubber

The thermal degradation of a commercial, stabilized, unfilled nitrile (Buna-N) rubber material was investigated at temperatures in the range 85–140 °C. The resulting heterogeneous oxidation, due to diffusion limitations in oxygen availability, was studied using infrared microscopy and modulus profiling. Degradation-related spectral changes were observed primarily in the hydroxyl, carbonyl and ester regions; quantitative analysis revealed identical oxidation profiles for these chromophores. These chemical oxidation profiles (carbonyl formation) were correlated with mechanical modulus (hardness) profiles. Degradation of the sample proceeds via a linear increase in the carbonyl concentration, but an exponential increase in the modulus with time. It is concluded that the profile development and aging behavior can be described by a diffusion-limited autoxidation mechanism which can be modeled computationally. The results are compared to those of a previously studied carbon-black-filled material.     

Condition monitoring methods applied to degradation of chlorosulfonated polyethylene cable jacketing materials

Three promising polymer material condition monitoring (CM) methods were applied to eight commercial chlorosulfonated polyethylene cable jacket materials aged under both elevated temperature and high-energy radiation conditions. The CM methods examined, cross-sectional modulus profiling, solvent uptake and NMR T₂ relaxation time measurements of solvent-swelled samples, are closely related since they are all strongly influenced by the changes in overall crosslink density of the materials. Each approach was found to correlate well with ultimate tensile elongation measurements, the most widely used method for following degradation of elastomeric materials. In addition approximately universal failure criteria were found to be applicable for the modulus profiling and solvent uptake measurements, independent of the CSPE material examined and its degradation environment. For an arbitrarily assumed elongation “failure” criterion of 50% absolute, the CSPE materials typically reached “failure” when the modulus increased to ∼35 MPa and the uptake factor in p-xylene decreased to ∼1.6.