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The rapid emergence of bacterial infections that are resistant to many drugs underscores the need for new therapeutic agents. Here we report that six- and eight-residue cyclic d,l-alpha-peptides act preferentially on Gram-positive and/or Gram-negative bacterial membranes compared to mammalian cells, increase membrane permeability, collapse transmembrane ion(More)
The production of amino acids and their condensation to polypeptides under plausibly prebiotic conditions have long been known. But despite the central importance of molecular self-replication in the origin of life, the feasibility of peptide self-replication has not been established experimentally. Here we report an example of a self-replicating peptide.(More)
A biosensor has been developed based on induced wavelength shifts in the Fabry-Perot fringes in the visible-light reflection spectrum of appropriately derivatized thin films of porous silicon semiconductors. Binding of molecules induced changes in the refractive index of the porous silicon. The validity and sensitivity of the system are demonstrated for(More)
Hollow tubular structures of molecular dimensions may offer a variety of applications in chemistry, biochemistry and materials science. Concentric carbon nanotubes have attracted a great deal of attention, while the three-dimensional tubular pore structures of molecular sieves have long been exploited industrially. Nanoscale tubes based on organic materials(More)
Naturally occurring membrane channels and pores are formed from a large family of diverse proteins, peptides and organic secondary metabolites whose vital biological functions include control of ion flow, signal transduction, molecular transport and production of cellular toxins. But despite the availability of a large amount of biochemical information(More)
Symbiosis is an association between different organisms that leads to a reciprocal enhancement of their ability to survive. Similar mutually beneficial relationships can operate at the molecular level in the form of a hypercycle, a collective of two or more self-replicating species interlinked through a cyclic catalytic network. The superposition of(More)
Almost all discussions of prebiotic chemistry assume that amino acids, nucleotides, and possibly other monomers were first formed on the Earth or brought to it in comets and meteorites, and then condensed nonenzymatically to form oligomeric products. However, attempts to demonstrate plausibly prebiotic polymerization reactions have met with limited success.(More)
The origin of homochirality in living systems is often attributed to the generation of enantiomeric differences in a pool of chiral prebiotic molecules, but none of the possible physiochemical processes considered can produce the significant imbalance required if homochiral biopolymers are to result from simple coupling of suitable precursor molecules. This(More)
The ability to monitor DNA polymerase activity with single-nucleotide resolution has been the cornerstone of a number of advanced single-molecule DNA sequencing concepts. Toward this goal, we report the first observation of the base-by-base DNA polymerase activity with single-base resolution at the single-molecule level. We describe the design and(More)