Untapped Opportunities of Resin-to-Resin Transfer Reactions (RRTR) for the Convergent Assembly of Multivalent Peptide Conjugates

Handling of the individual fragments remains a bottleneck in the convergent assembly of peptides. Overlooked since the emergence of ligation chemistries during the past two decades, so-called resin-to-resin transfer reactions (RRTR) are here described as a strategic shortcut in this context. Condensation of the involved moieties at an acceptor resin is facilitated by shuttling peptide segments directly from a donor resin in a one-pot fashion. The straightforward synthesis of a sterically constrained 13-mer peptidosteroid model illustrates the utility of this approach, presenting the first successful application of the RRTR methodology in the field of multivalent design and bioconjugation. Relying on established procedures to generate, monitor and isolate intermediates and products, the solid-phase nature of the entire strategy allows for the fast construction of polypeptide adducts and libraries thereof. As such, a rejuvenated use and new opportunities for RRTR are reported.     

Self-Assembled,Highly Positively Charged,Allyl–Pd Crowns: Cavity-Pocket-Driven Interactions of Fluoroanions

A series of dodecanuclear highly positively charged homo- and heterometallamacrocycles [{Pd(η³-2-Me-C₃H₄)}₆(4-PPh₂py)₁₂{M₂(tpbz)}₃]¹⁸⁺ (M=Pd, Pt; tpbz=1,2,4,5-tetrakis(diphenylphosphanyl)benzene were synthesized by the quantitative self-assembly of {Pd(η³-2-Me-C₃H₄)}⁺, {M₂(tpbz)}⁴⁺ and 4-PPh₂py moieties in 2:1:4 molar ratio. The cationic assemblies were obtained as salts of different fluorinated anions with diverse sizes and electronic properties, namely BF₄⁻, PF₆⁻, SbF₆⁻ and CF₃SO₃⁻. The new crown-like metallamacrocycles showed remarkable differences in their NMR spectra due to the presence of the different counteranions. On the basis of the observed variations, the metallacycles have been tested as catalytic precursors in allylic alkylation reactions. The anion-dependent activity and selectivity has been analysed and compared with that of the corresponding monometallic allylic corners [Pd(η³-2-Me-C₃H₄)(4-PPh₂py)₂]X (X=BF₄⁻, PF₆⁻, SbF₆⁻, CF₃SO₃⁻). DFT calculations have been employed in order to help to the interpretation of the experimental data and to model the anion–crown interactions.     

Influence of the Flame Straightening Process on Microstructural, Mechanical and Fracture Properties of S235 JR, S460 ML and S690 QL Structural Steels

The flame straightening of steel components is based on heating a local region of the part by means of a torch in order to induce a permanent deformation through a field of residual stresses. Although this is a very common practice, it is not devoid of serious drawbacks. In this paper, the influence of the flame bending procedure on the microstructure of three very different structural steels (S235 JR, S460 ML and S690 QL, respectively), widely used for the construction of metallic structures, is analysed. The consequences of the heat treatment on the mechanical and fracture properties were characterised through micro-hardness Vickers and Charpy impact tests; in addition, some elastic-plastic fracture tests were performed on precracked Charpy specimens manufactured with the S235 JR steel. The relationship between the microstructural features and the material mechanical and fracture behaviour was studied in depth in all cases, correlating the changes induced by the flame heat treatment on the microstructure with the macroscopic mechanical and fracture response. For a proper understanding of the microstructural consequences of this straightening heat treatment, it was necessary to develop a Finite Element numerical model. Based on the experimental results, this study has revealed that the consequences of the flame straightening on the microstructure, mechanical or fracture behaviour strongly depend on the nature of the material; for this reason, it is not possible to establish general recommendations. Nevertheless, the paper proposes a series of guidelines for good practice for steels similar to those characterised here.     

EFFECT OF COMPOSITION AND PROCESSING CONDITION ON MICROSTRUCTURAL PROPERTIES AND DURABILITY OF FLUOROPOLYMER/ACRYLIC BLENDS

Fluoropolymer blends have been widely used as binders for exterior coatings because of their excellent resistance to ultra-violet (UV) radiation as well as to many corrosive chemical agents.It is known that the fluorinated component usually has a lower glass transition temperature and easily crystallizes in the final structure depending upon the blend composition and sample annealing condition.We investigated the effect of blend composition and annealing process (slow and fast cooling) on the surface mor...