Enzyme Design from the Bottom Up: An Active Nickel Electrocatalyst with a Structured Peptide Outer Coordination Sphere

Catalytic, peptide‐containing metal complexes with a well‐defined peptide structure have the potential to enhance molecular catalysts through an enzyme‐like outer coordination sphere. Here, we report the synthesis and characterization of an active, peptide‐based metal complex built upon the well‐characterized hydrogen production catalyst [Ni(P^Ph₂N^Ph)₂]²⁺ (P^Ph₂N^Ph=1,3,6‐triphenyl‐1‐aza‐3,6‐diphosphacycloheptane). The incorporated peptide maintains its β‐hairpin structure when appended to the metal core, and the electrocatalytic activity of the peptide‐based metal complex (≈100,000 s^?1) is enhanced compared to the parent complex ([Ni(P^Ph₂N^APPA)₂]²⁺; ≈50,500 s^‐1). The combination of an active molecular catalyst with a structured peptide provides a scaffold that permits the incorporation of features of an enzyme‐like outer‐coordination sphere necessary to create molecular electrocatalysts with enhanced functionality.     

Some representations of solutions of elliptic equations

The Dirichlet problem for the region of the plane inside closed smooth curve C for second-order elliptic equations is considered. It is shown that under certain circumstances the solution u can be written uniquely in the form u(P) = ∝_cF(P, Q) g(Q) ds_Q, where F(P, Q) is the fundamental solution of the elliptic equation, and g?L² if the boundary value function f is absolutely continuous with square integrable derivative (f?W); and u(P) = p(F(P, ·)) where p is a unique bounded linear functional on W if f?L². These representations are valid in the exterior of C also. As special cases with slight modifications, the exterior Dirichlet problems for the Helmholtz and Laplace equations are mentioned.It is shown also that if kernel F(P′, Q), with P′ and Q on C, has a complete set of eigenfunctions {ψ_k(P′)} then u(P) can be expanded in a series of their extensions {ψ_k(P)}, where ψ_k(P) = λ_k ∝_cF(P, Q) ψ_k(Q) ds_Q.     

E2 nuclear resonance effects in pionic and kaonic atoms

The attenuation due to the E2 nuclear resonance effect has been measured in hadronic atoms using pions with ¹¹¹Cd and ¹¹²Cd, and for kaons with ¹²²Sn. Energies of the relevant X-ray and γ-ray transitions and of the X-ray cascade intensities have also been measured so as to give a self-consistent set of information. The results are found to be in very good agreement with theoretical calculations.     

On the genus of the semidirect product of ℤ9 by ℤ3

We show that the non-commutative semidirect product Γ of ?₉ by ?₃ has orientable genus 4. In other words, some Cayley graph of Γ embeds in an orientable surface of genus 4 (Euler characteristic ?6), but no Cayley graph of Γ embeds in an orientable surface of genus less than 4 (Euler characteristic greater than ?6). We also show that some Cayley graph of Γ embeds in a (non-orientable) surface of Euler characteristic ?3, but no Cayley graph of Γ embeds in a surface of Euler characteristic greater than ?3. Γ is the first known example of a group whose orientable Euler characteristic and non-orientable Euler characteristic differ by more than 1. Our results also complete the determination of the orientable genus of each group of order less than 32.     

A top-down LC-FTICR MS-based strategy for characterizing oxidized calmodulin in activated macrophages

A liquid chromatography-mass spectrometry (LC-MS)-based approach for characterizing the degree of nitration and oxidation of intact calmodulin (CaM) has been used to resolve ～250 CaM oxiforms using only 500 ng of protein. The analysis was based on high-resolution data of the intact CaM isoforms obtained by Fourier-transform ion cyclotron resonance mass spectrometry (FTICR MS) coupled with an on-line reversed-phase LC separation. Tentative identifications of post-translational modifications (PTMs), such as oxidation or nitration, have been assigned by matching observed protein mass to a database containing all theoretically predicted oxidation products of CaM and verified through a combination of tryptic peptide information (generated from bottom-up analyses) and on-line collisionally induced dissociation (CID) tandem mass spectrometry (MS/MS) at the intact protein level. The reduction in abundance and diversity of oxidatively modified CaM (i.e., nitrated tyrosines and oxidized methionines) induced by macrophage activation has been explored and semiquantified for different oxidation degrees (i.e., no oxidation, moderate, and high oxidation). This work demonstrates the power of the top-down approach to identify and quantify hundreds of combinations of PTMs for single protein target such as CaM and implicate competing repair and peptidase activities to modulate cellular metabolism in response to oxidative stress.     

Doppler-shifted nuclear gamma rays following stopped K− capture in aluminium

The Doppler broadened ²⁶Mg^* decay gamma peak hasma peak has been observed in coincidence with stopped kaons in an Al target. The results are compared with predictions based on single-nucleon absorption of the kaon.     

Kaonic Hydrogen atom X-rays

The X-ray spectrum obtained with kaons stopping in liquid hydrogen has been measured. Possible candidates for X-ray lines from kaonic hydrogen atoms have been identified and the results compared with previous experiments and with theoretical predictions. X-ray lines from σ^?p atoms may also have been observed.     

The ft value for the superallowed Fermi decay 38mK(β+)38Ar

The threshold energy for the reaction ³⁵Cl(α, n)^38mK has been measured to be 6674.8±3.2 keV and the Q-value for the reaction ³⁵Cl(α, p)³⁸Ar to be 837.2±2.4 keV. From the measurements a value of 5021.2±3.4 keV was obtained for the end-point energy of the decay ^38mK(b⁺)³⁸Ar. The half-life was measured as 925.6±0.7ms and hence an “effective” $\text{?t}$ value was calculated, giving the result 3106±10 s with the inclusion of outer radiative corrections to order Z²α³ and 3088±10 s allowing also for calculated charge-dependent effects.     

CrAsH: a biarsenical multi-use affinity probe with low non-specific fluorescence

CrAsH is a tetracysteine-binding probe which has improved properties in terms of signal-to-noise ratio and pH dependence of fluorescence compared to the parent compound.     

Tunable short-pulse beat-wave laser source operating at 1 microm

We have demonstrated a chirped-pulse-amplification system utilizing an air-spaced etalon inside a regenerative amplifier to produce two simultaneous 2.0-ps pulses, one centered at the gain peak of Nd:phosphate glass (1052 nm) and the other centered at the gain peak of Nd:silicate (1061 nm). Autocorrelations of the resulting beat wave demonstrate a beat frequency of 2.3 THz. We achieved wavelength tunability over a 10-nm range by electronically adjusting the etalon spacing and variable pulse width by changing the etalon rotation.