Characterization of novel antimicrobial peptoids.

Peptoids differ from peptides in that peptoids are composed of N-substituted rather than alpha-carbon-substituted glycine units. In this paper we report the in vitro and in vivo antibacterial activities of several antibacterial peptoids discovered by screening combinatorial chemistry libraries for bacterial growth inhibition. In vitro, the peptoid CHIR29498 and some of its analogues were active in the range of 3 to 12 microg/ml against a panel of gram-positive and gram-negative bacteria which included isolates which were resistant to known antibiotics. Peptoid antimicrobial activity against Staphylococcus aureus was rapid, bactericidal, and independent of protein synthesis. beta-Galactosidase and propidium iodide leakage assays indicated that the membrane is the most likely target of activity. Positional isomers of an active peptoid were also active, consistent with a mode of action, such as membrane disruption, that does not require a specific fit between the molecule and its target. In vivo, CHIR29498 protected S. aureus-infected mice in a simple infection model.

Cell-free DNA in human blood plasma: length measurements in patients with pancreatic cancer and healthy controls.

The amount of non-cell-associated DNA free in blood plasma from pancreatic cancer patients usually exceeds that from healthy donors. We have evaluated the plasma DNA by gel electrophoresis and measured the variation in length of soluble DNA fragments by electron microscopy in plasma from three patients with pancreatic cancer and from three healthy controls. Whereas electrophoresis of nick-translated DNA isolated from plasma obtained from healthy controls showed autoradiographic bands at sizes equivalent to whole-number multiples (1-5x) of nucleosomal DNA (185-200 bp), in the samples obtained from pancreatic cancer patients, stronger ladder patterns appeared. Likewise, strand length distributions of DNA (DNA-SL) in the two groups differ. The DNA-SL distribution data include 2,752 measurements made from cancer patient plasma and 3,291 for control plasma. The shortest DNA-SL measured approximately 30 nm (approximately 88 bp calculated at 0.34 nm/bp) and the largest approximately 28,000 nm (>80,000 bp), with 50% of all lengths measuring between 100 and 900 nm long. The average plasma DNA-SL in controls (311 nm; median, 273 nm) exceeded that in cancer patients (231 nm; median, 185 nm). Small excesses of DNA at approximately 63, approximately 126, approximately 189, approximately 252, and approximately 315 nm, corresponding to small multiples of lengths associated with nucleosomes, were more prominent in the cancer patient plasma than in the healthy control plasma. This study provides evidence indicating differences in non-cell-associated DNA in plasma between cancer patients and healthy controls and indicates that a significant amount of this DNA is probably derived from apoptosis in neoplastic and/or normal cells.