A DNA sequencing system based on the use of a novel set of four chain-terminating dideoxynucleotides, each carrying a different chemically tuned succinylfluorescein dye distinguished by its fluorescent emission is described. Avian myeloblastosis virus reverse transcriptase is used in a modified dideoxy DNA sequencing protocol to produce a complete set of fluorescence-tagged fragments in one reaction mixture. These DNA fragments are resolved by polyacrylamide gel electrophoresis in one sequencing lane and are identified by a fluorescence detection system specifically matched to the emission characteristics of this dye set. A scanning system allows multiple samples to be run simultaneously and computer-based automatic base sequence identifications to be made. The sequence analysis of M13 phage DNA made with this system is described.

Determination of the compositional heterogeneity of polydisperse polymer samples by the coupling of size-exclusion chromatography and thermal field-flow fractionation van Asten, A.C.; van Dam, R.J.; Kok, W.T.; Tijssen, R.; Poppe, H. Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. An off-line coupling of size-exclusion chromatography (SEC) and thermal field-flow fractionation (ThFFF) was used successfully to cross-fractionate copolymers and polymer blends. Various fractions of different molecular mass were obtained from polydisperse polymer samples by SEC. Because the molecular diffusion coefficients were known, the ThFFF analysis of these fractions yielded directly thermal diffusion coefficients. As thermal difftcion is strongly affected by the chemical nature of the polymer, the chemical composition of polymer samples can be studied as function of the molecular mass with this technique. This is illustrated with the SEC-ThFFF crossfractionation of a polystyrene sample blended with a polybutadiene and a polytetrahydrofuran standard, and of butadiene-and styrene-methylmethacrylate copolymers.

Photoelectron micrographs of fixed, unstained, uncoated chicken embryo fibroblasts and absolute photoelectron quantum yields in the 180-230 nm wavelength band of L-fucose, D-galactose, D-glucose, N-acetyl-D-glucosamine, and the sucrose polymer Ficoll are reported. The quantum yields of the saccharides are low compared to the reference dye, phthalocyanine, and fall in the same range as those previously measured for amino acids and membrane phospholipids. Photoelectron micrographs of the unstained and uncoated cells inhibit considerable surface detail. The photoelectron quantum yield data and the micrographs indicate that surface relief is the dominant source of contrast.

The photoelectron quantum yields of 21 common amino acids and 15 polyamino acids were measured in the 180-240 nm wavelength region. On the average, the quantum yields of these two groups exhibit quite similar wavelength dependence. For lambda > 220 nm all amino acid and polyamino acid quantum yields are

The absolute PE quantum yield curves of chls u and b,.chln, and phytol were examined over the wavelength range 50G180 nm. In the long wavelength region (500-240 nm) quantum yields are below 5 x electrons per incident photon. Below 240 nm the quantum yields rise sharply. The chls and chln exhibit similar yield curves; measured yields were of order 5 x lO-"electrons per incident photon at 240 nm, 1 x at 220 nm, and 1 x at 180 nm. These yields are at least 2 orders of magnitude greater than those of the amino acids and more than three orders of magnitude greater than that of phytol over this wavelength region. Photoemission observed in chl thin films is due to the porphyrin moiety of the molecule. High contrast is obtained in PE micrographs of chln deposited on substrates of bovine serum albumin, dipalmitoyl phosphatidylcholine, or starch. Chl is expected to be the dominant photoemissive component of thylakoid membranes and accounts for the image contrast observed previously in PE micrographs of spinach chloroplasts.