Two‐fold Bioorthogonal Derivatization by Different Formylglycine‐Generating Enzymes

Formylglycine‐generating enzymes are of increasing interest in the field of bioconjugation chemistry. They catalyze the site‐specific oxidation of a cysteine residue to the aldehyde‐containing amino acid C^α‐formylglycine (FGly). This non‐canonical residue can be generated within any desired target protein and can subsequently be used for bioorthogonal conjugation reactions. The prototypic formylglycine‐generating enzyme (FGE) and the iron‐sulfur protein AtsB display slight variations in their recognition sequences. We designed specific tags in peptides and proteins that were selectively converted by the different enzymes. Combination of the different tag motifs within a single peptide or recombinant protein enabled the independent and consecutive introduction of two formylglycine residues and the generation of heterobifunctionalized protein conjugates.     

A finite-element approach in order to avoid ill-conditioning in thin-sheet problems in frequency domain—Application to magneto-quasistatics

In this work, a new thin-sheet approach in the finite-element method is derived. The focus is on the condition number of the system matrix, namely, to keep this measure preferably independent of the thickness of the sheet. Constant sheet elements are used for the tangential variation in the sheet. However, the information about the discontinuity in normal direction is incorporated into the basis functions of the volume elements that are connected to the sheet elements. The determination of the normal variation can be reduced to a 1D problem which can be solved analytically. No double layers or global asymptotic expansions are required. The advantages with respect to the condition number of the system matrix are shown for a magneto-quasistatic test scenario.     

A key to improved ion core confinement in the JET tokamak: ion stiffness mitigation due to combined plasma rotation and low magnetic shear

New transport experiments on JET indicate that ion stiffness mitigation in the core of a rotating plasma, as described by Mantica et al. [Phys. Rev. Lett. 102, 175002 (2009)] results from the combined effect of high rotational shear and low magnetic shear. The observations have important implications for the understanding of improved ion core confinement in advanced tokamak scenarios. Simulations using quasilinear fluid and gyrofluid models show features of stiffness mitigation, while nonlinear gyrokinetic simulations do not. The JET experiments indicate that advanced tokamak scenarios in future devices will require sufficient rotational shear and the capability of q profile manipulation.     

Noncritically phase-matched fourth harmonic generation of Nd:glass lasers in partially deuterated KDP crystals

Noncritically phase-matched (NCPM) fourth harmonic generation (FHG) of Nd:glass laser radiation in partially deuterated dihydrogen phosphate (KD*P) crystals has been demonstrated. At an Nd:glass laser wavelength of 1053.0 nm, NCPM FHG is achieved in 70% deuterated KD*P at a crystal temperature of 18.5±0.1 °C. Tuning the fundamental laser wavelength from 1052.9 to 1053.2 nm, FHG in KD*P is NCPM by changing the crystal temperature from 17.9 °C to 20.5 °C. When driven with 2.4 J of second harmonic radiation in a 3 ns flat-top pulse, corresponding to 1 GW/cm(2) 2ω drive intensity, 1.9 J of fourth harmonic radiation was generated in a 6 mm long KD*P crystal, yielding a second to fourth harmonic energy conversion efficiency of 79%.     

Temporal discretization choices for stable boundary element methods in electromagnetic scattering problems

Diverse alternative temporal discretization schemes are analyzed for stable numerical solution of the surface integral equations in obtaining the transient scattering response of arbitrarily shaped conducting bodies. Streamlined formulations for three main categories including using either the conventional time integrators or the subdomain temporal basis functions, or the entire-domain time bases are presented in conceptually similar frameworks for solving types of the electric, magnetic, and combined field integral equations. To this end, first compatible temporal interpolations with conveniently usable time integrators are introduced based on stability analysis of the delay differential equations (DDE). Detailed guidelines for effective implementation of appropriate subdomain time basis functions are then studied. It is demonstrated that since in the latter approach the time derivatives are handled analytically, the extension of the stable region tremendously enhances while approaching small time step sizes. Eventually, the orthogonal weighted Laguerre polynomials are set forth to provide unconditionally stable schemes. Besides, adaptive partitioning of triangular patches is proposed to efficiently control the precision of numerical quadratures over the surface of source distribution. Numerical results are verified through comparison with the results obtained using the finite integration technique (FIT). Convergence behaviour of the widely used schemes is also investigated.     

A Chiral Macrocyclic Oligothiophene with Broken Conjugation – Rapid Racemization through Internal Rotation

A macrocyclic oligothiophene with an integrated pseudo‐para substituted [2.2]paracyclophane has been achieved. The synthetic sequence relies on alternating steps of halogenation‐ and Suzuki‐coupling conditions. By employing a modified Eglinton reaction under high dilution conditions, the macrocycle is closed and the obtained diacetylene is efficiently transferred to the corresponding thiophene. The molecule is fully characterized and its dynamic racemization is analyzed by variable temperature NMR experiments. The racemization barrier hints with 38 kJ/mol at rapid enantiomerization at room temperature by Mislow’s ‘Euclidian rubber glove’ enantiomerization process. Macrocycle formation results in red‐shifted absorption and emission spectra, hinting at increased conjugation through the oligothiophene versus the trough space conjugation through the [2.2]paracyclophane.     

Wave energy in a beam plasma system

The question of the sign of the energy of the electrostatic wave which is excited in a beam plasma system is discussed. The relevance of this sign for the existence of an explosively unstable coupling to two positive energy waves is investigated. Weakly explosive instabilities are expected.     

The Molecular and Crystal Structure of 3β-O-(2′,3′ -O-isoropylidene-α-L-rhamnopyranosyl) — digitoxigenin

3β-O-(2′,3′ -O-isoropylidene-α-L-rhamnopyranosyl) — digitoxigenin crystallizes in the monoclinic space group P 2₁ with two molecules C₃₂H₄₈O₈ per unit cell and the lattice constants a = 7.865, b = 6.470, c = 29.803 Å, β = 93.95°. The structure was solved by direct methods of phases determination and subsequently refined by least squares technique to the final R-value 0.06. The position of the lactone ring is disordered in the crystal.     

Silicon‐modified surfactants and wetting: V. The spreading behaviour of trimethylsilane surfactants on energetically different solid surfaces

The spreading behaviour of defined trimethylsilane‐based surfactants of general formula (CH₃)₃Si(CH₂)₆(OCH₂CH₂) _nOCH₃, n = 2–6, on five different solid surfaces at 21 °C has been investigated. Compounds bearing short diethylene and triethylene glycol hydrophiles do not spread. For the longer‐chained tetraethylene to hexaethylene glycol derivatives, the ability to spread depends on the surface energy. Rapid spreading is restricted to the slightly polar surface of 40 mN m⁻¹ surface energy. Lower or higher surface energies considerably reduce the spreading rates. The phase behaviour of the solutions substantially influences the spreading process. The dispersed systems of the tetraethylene glycol derivative spread constantly over long time intervals. The dispersions of the pentaethylene glycol analogue are very close to the temperature for a transition into the one‐phase state. A retardation of the spreading process occurs after a few seconds. Micellar solutions of the hexaethylene glycol derivative either spread very slowly or stop spreading after a few seconds. The largest spreading areas and highest initial spreading rates were found for the 0.1 wt% solutions. Copyright © 1999 John Wiley & Sons, Ltd.