Solution grown isotactic polystyrene crystals. I. Degree and distribution of crystallinity; thermal stability

The subject of this paper is the degree of crystallinity and annealing behavior of solution grown single crystals of isotactic polystyrene (IPS) in relation to the fold length, an enquiry which acquires special significance in view of the fact that previously the fold length had been found to be identical over a wide range of crystallization temperatures (T_c). It was found that both crystallinity and thermal stability increase with T_c even over the range of constant fold length thus invalidating the usual assumption that the fold length and crystal properties are uniquely correlated. Further, the crystallinity figures as measured by conventional calorimetry are very low (<50% throughout) which by conventional ideas would require an unrealistically thick amorphous surface layer. However, the “linear crystallinity” (crystal core thickness as determined from x-ray linewidths) is much larger, commensurate with crystallinities in single crystals from other materials. It is suggested that this is the more relevant figure for the subdivision of the lamellas into crystal core and surface layer. The additional amorphous content being otherwise accommodated. Further, this “linear crystallinity” is broadly unaffected by fold length changes induced by heat annealing. The thermal stability (including annealing ability) of the crystals differs markedly whether T_c is above or below ～60°C, a T_c value which is in the range where the fold length is constant, but corresponds to a maximum in the crystallization rate. Possible connections between crystallization conditions and the stability of the resulting crystals (fold length considerations apart) are pointed out.     

Synthesis and crystal structure of [(PhenH)(PhenH2)][BiCl6]·2H2O with different o-phenanthroline protonations

The reaction between bismuthate oxide and phen (1,10-phenanthroline) in acid medium led to the isolation of the unusual [(PhenH)(PhenH₂)][BiCl₆]·2H₂O derivative, which has been characterized by X-ray analysis and IR spectroscopy. The compound crystallizes in the triclinic space group with a = 8.313(2), b = 9.349(2), c = 9.807(3) Å, = 86.39(3), = 110.27(3) and = 106.48(3)°. The crystal structure is made of [BiCl₆]^3– anions and [(PhenH)(PhenH₂)]³⁺ cations. A network of hydrogen bond interactions involving the two clathrated water molecules, the phenanthroline moiety and the chlorines characterizes the entire structure.     

Nucleophilic substitutions in the isoindole series as a valuable tool to synthesize derivatives with antitumor activity

A novel synthetic approach to the synthesis of 3-substituted isoindoles through nucleophilic substitution of 3-halo derivatives by charged carbon, and neutral nitrogen, oxygen, and sulfur nucleophiles, assisted by a 1-acyl group, is reported. Aryl-thio-isoindoles, obtained through a direct nucleophilic substitution with sulfur nucleophiles, showed cytotoxic activity, with GI₅₀ values from micromolar to sub-micromolar concentrations, against the total number of cell lines investigated.     

Plasma proteomics for biomarker discovery: a study in blue

The performance of Cibacron Blue dye (HiTrapBlue or Affigel Blue) in depleting albumin from plasma, as a pre-treatment for biomarker searching in the low-abundance proteome, is here assessed. It is shown that (i) co-depletion of non-albumin species is an ever-present hazard; (ii) the only proper eluant able to release quantitatively the proteins bound to the dye is boiling 4% SDS-25 mM DTT, an ion shock (2 M NaCl) being quite ineffective in releasing the low-abundance species tightly bound to the dye moiety; (iii) the mechanism of dye-protein interaction, after an initial ion-ion docking, is a robust hydrophobic interaction, which progressively augments at lower and lower pH values; (iv) at pH 2.2 in the presence of 0.1% TFA, the blue resin behaves, for all practical purposes, just as a reverse-phase chromatography column, since all residual proteins present in plasma are completely harvested. However Cibacron Blue technology should not necessarily be discarded: As long as also the plasma fraction adsorbed is properly released and analyzed, together with the flow through, one should be able to perform a viable analysis of the low-abundance proteome.