Abstract: A single stranded nucleic acid biosensor for S-adenosylhomocysteine (SAH) is provided. The single stranded nucleic acid may include a SAH-binding riboswitch domain comprising a P2? stem and a contiguous Spinach aptamer domain terminated at a P2 stem that is operably connected to the P2? stem of the SAH-binding riboswitch domain via a P2/P2? stem comprising 5 base pairs or less. The SAH biosensor may further include a signaling chromophore specifically bound to the Spinach aptamer domain, where the sensor is configured to fluorescently activate the signaling chromophore upon specific binding of SAH to the SAH-binding riboswitch domain. Also provided are methods in which the subject SAH biosensors fmd use including methods for determining the level of SAH in a sample and methods for determining the level of methyltransferase activity in a cell. Nucleic acid constructs for the single stranded nucleic acid and host cells including the same are also provided.

Abstract: Peptide analogs in which one or more amino acids is replaced by a diaza- or triazacyclohexenone, or by an aza-, diaza-, or triazacyclohexenone that is substituted at the ?-position with a side chain of an amino acid, display an improved ability to assume a ?-strand conformation and to enter into ?-sheet-like interactions with peptides in an affinity-specific manner. The peptide analogs of this invention therefore have utility as ?-strand mimics offering advantages over both native peptides and ?-strand mimics of the prior art.