Phosphate-Rich Biomimetic Peptides Shed Light on High-Affinity Hyperphosphorylated Uranyl Binding Sites in Phosphoproteins

Some phosphoproteins such as osteopontin (OPN) have been identified as high-affinity uranyl targets. However, the binding sites required for interaction with uranyl and therefore involved in its toxicity have not been identified in the whole protein. The biomimetic approach proposed here aimed to decipher the nature of these sites and should help to understand the role of the multiple phosphorylations in UO₂²⁺ binding. Two hyperphosphorylated cyclic peptides, pS₁₆₈ and pS₁₃₆₈ containing up to four phosphoserine (pSer) residues over the ten amino acids present in the sequences, were synthesized with all reactions performed in the solid phase, including post-phosphorylation. These β-sheet-structured peptides present four coordinating residues from four amino acid side chains pointing to the metal ion, either three pSer and one glutamate in pS₁₆₈ or four pSer in pS₁₃₆₈ . Significantly, increasing the number of pSer residues up to four in the cyclodecapeptide scaffolds produced molecules with an affinity constant for UO₂²⁺ that is as large as that reported for osteopontin at physiological pH. The phosphate-rich pS₁₃₆₈ can thus be considered a relevant model of UO₂²⁺ coordination in this intrinsically disordered protein, which wraps around the metal ion to gather four phosphate groups in the UO₂²⁺ coordination sphere. These model hyperphosphorylated peptides are highly selective for UO₂²⁺ with respect to endogenous Ca²⁺, which makes them good starting structures for selective UO₂²⁺ complexation.     

Investigation of the Kr + Au system at 22 MeV/u

With laser-atomic-beam-spectroscopy the hyperfinestructure splitting constants A, B and the lifetimes τ of the Mn I levels 3d⁵4s4p z⁴p_3/2,5/2 were determined from the UV intercombination lines 321,7 nm and 322,5 nm. We obtained: A=?821(3)MHz, B=?40(30)MHz, τ=1120(50)nsec for the J=3/2 level and A=?607,8(1,5)MHz, B=+75(15)MHz, τ=970(50)nsec for the J=5/2 level.     

Elastic and inelastic scattering of carbon ions at intermediate energies

Elastic and inelastic scattering have been measured at E_lab = 360 MeV and 1016 MeV for the ¹²C + ¹²C system, as well as elastic scattering for ¹³C + ²⁰⁸Pb at 390 MeV. An optical-model analysis is reported and nuclear surface transparency effects are discussed, together with the energy dependence of the nuclear potential. A DWBA analysis of data on the 2⁺, 4.4 MeV state of ¹²C is reported and trends in the energy dependence of mean-field excitations are deduced.     

Projectile fragments from 86 MeV/nucleon 12C induced reactions

An 86 MeV/nucleon ¹²C beam has been used to bombard targets of C, Ag and Au. Energy spectra of reaction products with Z = 3?6 and A = 6?12 have been measured at angles between 3° and 20°. A simple fragmentation model, while predicting approximately the gross features of the data, fails to describe the results in detail.     

Observation of two-photon emission in nuclear pion capture

The emission of two photons above 25 MeV energy was observed in the capture of stopped pions by beryllium and carbon with a rate of (1.0 ± 0.1) × 10⁻⁵, respectively (1.4 ± 0.2) × 10⁻⁵ per capture. These rates are about two to four times greater than various free-nucleon estimates based on the π⁻+π⁺→γγ annihilation mechanism alone.     

States of 74Ge via the (p,p') inelastic scattering at 22 MeV

The ⁷⁴Ge(p, p') inelastic scattering has been studied at 22 MeV with an overall resolution of 10 keV using a tandem Van de Graaff and a split-pole magnetic spectrometer. Angular distributions have been obtained for about 40 levels in ⁷⁴Ge and comparisons with DWBA and CCBA calculations have allowed spin and parity assignments. The presence of an important collective component in the wave functions of many levels is required in order to explain the data. Possible unnatural-parity levels are populated.     

Particle field characterization by digital in-line holography: 3D location and sizing

Recent developments have shown the potential of digital in-line holography for diagnostics in fluids. This new method provides a low-cost and easy access method for measuring both size and velocity of small particles in a volume. Here it is shown that by applying traditional image processing tools on the particle images digitally reconstructed, statistically reliable results on particles size and location are provided. The method is experimentally illustrated by glass microspheres that are moving in a turbulent flow generated by an annular jet. A comparison with the histogram diameters provided by a common diffraction particle sizer are presented.     

Asymmetric synthesis of 6-alkyl- and 6-arylpiperidin-2-ones. Enantioselective synthesis of (S)-(+)-coniine

A variety of diolefinic hydrazides (1) have been assembled in a highly diastereoselective manner by addition of allyllithium to chiral SAMP hydrazones followed by N-acylation with acryloyl chloride. Substrates 1 undergo ring-closing metathesis to give the cyclic enehydrazides (5) which can be easily converted into virtually enantiopure 6-alkyl- or 6-arylpiperidin-2-ones (7). The versatility of this hydrazone addition-RCM protocol has been further exemplified by the conversion of the unsaturated heterocycle 5b into the piperidine alkaloid (S)-(+)-coniine.     

DNA-Based Asymmetric Inverse Electron-Demand Hetero-Diels–Alder

While artificial cyclases hold great promise in chemical synthesis, this work presents the first example of a DNA-catalyzed inverse electron-demand hetero-Diels–Alder (IEDHDA) between dihydrofuran and various α,β-unsaturated acyl imidazoles. The resulting fused bicyclic O,O-acetals containing three contiguous stereogenic centers are obtained in high yields (up to 99 %) and excellent diastereo- (up to >99:1 dr) and enantioselectivities (up to 95 % ee) using a low catalyst loading. Most importantly, these results show that the concept of DNA-based asymmetric catalysis can be expanded to new synthetic transformations offering an efficient, sustainable, and highly selective tool for the construction of chiral building blocks.