Pioloform F Instead of Formvar as a Support Film for TEM

Pioloform F (Wacker Chemie Co., Munich, Germany) is an excellent plastic for use as a support film for electron microscopy. The advantages of Pioloform F are high mechanical and thermal stability, and low material bulk (Stockem, 1970). Because of these properties, thinner films than Formvar or collodion may be used and remain stable under the electron beam without subsequent stabilization by carton coating. Thin support films of gray interference color are prepared by dissolving 0.5 grams of Pioloform F powder in 100 milliliters of anhydrous chloroform (Stockem, 1970), using the dip method described by Reimer (1967).

Synthetic oligopeptides as polymer precursors

By reacting N-carboxyanhydrides of L-phenylalanine, DL-phenylalanine, L-leucine or of a mixture of DL-phenylalanine and L-leucine with hexamethylenediamine (15-20 mol.% related to monomer) in absolute benzene at 25 °C, which was followed by an additional treatment with hexamethylenediamine (60 °C, 4 h), oligopeptides were prepared with the average functionality (Fn) 1.72-1.96 with respect to primary amino groups. The reaction between these oligopeptides and poly(oxyethylene) terminated with isocyanate groups (Fn 1.69-1.94) in anhydrous chloroform at 25 °C leads to copolymers of the type A-B and A-B-A with a minority content of copolymers (A-B)m for m ≥ 2. The low efficiency of the coupling reaction is attributed to the formation of an important amount of monofunctional oligopeptide in the preparation reaction.

THE PREPARATION OF LECITHIN FROM L-α-GLYCERYLPHOSPHORYLCHOLINE

L-α-Lecithin (dipalmitoyl) has been prepared from L-α-glycerylphosphoryl-choline by acylation with palmitoyl chloride in anhydrous chloroform in a yield of about 31%. This reaction also gives rise to two by-products having hemolytic activity. One of these, although not yet completely characterized, is chromatographically comparable with lysolecithin formed from lecithin by the action of snake venom lecithinase. The second by-product possessing hemolytic activity but chromatographically different from common lysolecithin was shown to be a monoacyl derivative of L-α-glycerylphosphorylcholine.

THE PREPARATION OF LECITHIN FROM L-α-GLYCERYLPHOSPHORYLCHOLINE

L-α-Lecithin (dipalmitoyl) has been prepared from L-α-glycerylphosphoryl-choline by acylation with palmitoyl chloride in anhydrous chloroform in a yield of about 31%. This reaction also gives rise to two by-products having hemolytic activity. One of these, although not yet completely characterized, is chromatographically comparable with lysolecithin formed from lecithin by the action of snake venom lecithinase. The second by-product possessing hemolytic activity but chromatographically different from common lysolecithin was shown to be a monoacyl derivative of L-α-glycerylphosphorylcholine.