Atom transfer radical polymerization in the presence of a thiol: more evidence supporting radical intermediates

Octanethiol, a free-radical chain transfer agent, was added to the atom transfer radical polymerization of methyl methacrylate. The molecular weight and polydispersity data of the polymers produced were consistent with the known chain transfer behaviour of octanethiol in conventional free-radical polymerization. These results, which clearly indicate a radical nature of the propagating species, can be explained by a simple kinetic model, which describes an otherwise "living" polymerization system in the presence of an added chain transfer agent

Suppression of human melanoma cell growth and metastasis by the melanoma-associated antigen CD63 (ME491)

CD63 has been identified in human melanoma cells by a number of different monoclonal antibodies (MAbs). Studies with MAbs have shown that expression is most marked in naevi and early forms of cutaneous melanoma and reduced in vertical growth phase and metastatic lesions. To investigate further the role of CD63 in progression of melanoma, genomic CD63 was transfected into a CD63 negative human melanoma cell line using an episomal vector. The stable transfected melanoma cells had similar growth rates to control transfected melanoma cells in vitro but much lower growth rates when injected intradermally into athymic nude mice. The CDb3-transfected cells also had a reduced number of metastases in the peritoneal cavity and subcutaneous sites when injected intravenously. MAb against CD63 did not influence the growth of CDb3-transfected melanoma cells in vitro. Our results confirm previous studies using H-ros-transformed NIH3T3 fibroblasts and suggest that CD63 may have a role as a tumor suppressor gene in human melanoma that acts to limit invasion and progression of melanoma. (C) 1995 Wiley-Liss, Inc