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L G Cooper

Publications and source records attributed to L G Cooper.

4 recordsLinked to original sources
PubMed1995

Helix formation in model peptides based on nucleolin TPAKK motifs.

The structures formed by peptide models of the N-terminal domain of the nucleolar protein nucleolin were studied by CD and nmr. The sequences of the peptides are based on the putative nucleic acid binding sequence motif TPAKK. The peptides TP1 and TP2 have the sequence acetyl-G(ATPAKKAA)nG-amide, with n = 1 and 2, respectively. CD measurements indicate structural changes in both peptides when the lysine side chains are uncharged by increasing the pH or acetylation of the side-chain amines. When trifluoroethanol (TFE) is added, more extensive structural changes are observed, resembling helical structure based on nmr nuclear Overhauser effect (NOE) and C alpha proton chemical shift changes, and CD spectra. The structure formed in 0.5M NaClO4 as observed by nmr is similar to that when the lysine side chains are acetylated, due presumably to interactions of perchlorate ion with side-chain charges on lysines. The helical structure observed in TPAKK motifs may be stabilized via N-capping interactions involving threonine. The structures observed in TFE suggest that the Thr-Pro sequence initiates short helical segments in TPAKK motifs, and these helical structures might interact with nucleic acids, presumably via interactions between lysines and threonines of nucleolin.

Amino Acid Sequence↗
PubMedDate not supplied

Effect of maternal age on birth outcomes among young adolescents.

This study examined the effect of maternal age on birth outcomes among young adolescents, ages 10 through 15. All records representing single births of primipara, Black or White adolescents, were selected for analysis from the 1983-1986 National Center for Health Statistics' Public Use Linked Live Birth-Infant Death Data File (n = 127,668). Logistic regression analyses controlled for effects of maternal race, marital status, prenatal care, gravidity, education, and metropolitan/nonmetropolitan residency. Univariate analyses indicated that the youngest adolescents were at greatest risk for negative birth outcomes including very preterm and preterm delivery, low birth weight, small for gestational age (SGA), and neonatal mortality. Logistic analyses showed similar results, with the exception that differences in SGA were insignificant. This study indicates the importance of examining age-specific birth outcomes among a population that has traditionally been studied in aggregate and underscores the need for increased prevention efforts.

Adolescent↗
PubMedDate not supplied

Amoeboid locomotion of Naegleria gruberi: the effects of cytochalasin B on cell-substratum interactions and motile behavior.

The major manifestations of amoeboid locomotion in Naegleria-cytoplasmic streaming, pseudopod production, cell polarity and focal contact production-require that the actin-based cytoskeleton be extremely dynamic. Whether these features are causally linked is unclear. In an attempt to answer this question we have used the fungal product cytochalasin B (cyt B) to dissect the motility process. This drug can perturb the organisation of actin filaments both in vivo and in vitro. Essentially cyt B acts as a molecule which can cap the barbed ends of actin filaments. Not surprisingly, therefore cyt B has an effect on rates of actin polymerization and the dynamic state of actin in the cytoplasm. We have found that cyt B has a profound effect on focal contact production and breakdown. Within minutes of addition of cyt B focal contact production ceases, existing focal contacts are stabilised but cytoplasmic streaming and pseudopod production are not blocked. In conclusion it is now clear that the state of actin required for focal contact production is different from that required for pseudopod extension and cytoplasmic streaming.

Actins↗