Assembly of flexuous plant viruses and their proteins.

Recent experiments on the disassembly and assembly of some flexuous plant viruses and their proteins are described. The properties of reconstituted potato virus X and those of assembled potato virus Y protein are considered as well as the suitability of other flexuous viruses for reconstitution studies.     

Effects of maternal thrombocytopenia on platelet counts of pre- and postnatal mice

The effects of maternal thrombocytopenia on platelet counts of pre- and postnatal mice were determined. Platelet counts of gravid mice were reduced at 2–3 days before parturition by injection of rabbit anti-mouse platelet serum (RAMPS). Marked rebound-thrombocytosis was observed after 4–6 days. Platelet counts of pre- and postnatal mice whose mothers were injected with RAMPS 3 days before parturition were unaltered except at 1 day before and at the time of birth when they were significantly (P<0.005) reduced. The results of immunodiffusion techniques showed that RAMPS crossed the placental barrier resulting in reduced platelet counts of the fetuses, but significant fetal rebound-thrombocytosis was not observed.     

Chemical and enzymic studies on biosynthesis of the natural porphyrin macrocycle: Formation and role of unrearranged hydroxymethylbilane and order of assembly of the pyrrole rings

Following a review of the background to current research, it is shown that the action of deaminase alone on porphobilinogen leads to release into the medium of the unrearranged hydroxymethylbilane (20), which (a) ring closes chemically to uro'gen-I and (b) is very rapidly converted by deaminase-cosynthetase into uro'gen-III. The biosynthetic role of this HOCH₂-bilane is studied, and the results show that deaminase is a builder of the unrearranged bilane system but is not a cyclizing enzyme. The work also shows that deaminase and cosynthetase have independent active sites but that they may work in close physical association. Finally, it is established that the tetrapyrrole macrocycle is assembled starting at ring A and building around to ring D.     

Small angle X-ray scattering of dimeric yeast hexokinase in solution.

Small angle x-ray scattering measurements on dimeric yeast hexokinase B at pH 5.5 in acetate buffer yield a radius of gyration of 31.28 +/- 0.23 angstrom. This measured value is comparable to the radius of gyration of 31.5 angstrom calculated from the refined coordinates of the dimer in the BII crystal form. The hexokinase dimer found in the BI crystal form has a radius of gyration of 42 angstrom calculated from the atomic coordinates. Thus, the measured radius of gyration is consistent with the BII dimer being the predominant species in solution and rules out the existence of the BI dimer as a major species under these conditions.     

Thienopyrimidine-based dual EGFR/ErbB-2 inhibitors

Two new series of potent and selective dual EGFR/ErbB-2 kinase inhibitors derived from novel thienopyrimidine cores have been identified. Isomeric thienopyrimidine cores were evaluated as isosteres for a 4-anilinoquinazoline core and several analogs containing the thieno[3,2-d]pyrimidine core showed anti-proliferative activity with IC₅₀ values less than 1 μM against human tumor cells in vitro.