Native Serotonin Membrane Receptors Recognize 5-Hydroxytryptophan-Functionalized Substrates: Enabling Small-Molecule Recognition

Abstract

Recognition of small diffusible molecules by large biomolecules is ubiquitous in biology. To investigate these interactions, it is important to be able to immobilize small ligands on substrates; however, preserving recognition by biomolecule-binding partners under these circumstances is challenging. We have developed methods to modify substrates with serotonin, a small-molecule neurotransmitter important in brain function and psychiatric disorders. To mimic soluble serotonin, we attached its amino acid precursor, 5-hydroxytryptophan, via the ancillary carboxyl group to oligo(ethylene glycol)-terminated alkanethiols self-assembled on gold. Anti-5-hydroxytryptophan antibodies recognize these substrates, demonstrating bioavailability. Interestingly, 5-hydroxytryptophan-functionalized surfaces capture membrane-associated serotonin receptors enantiospecifically. By contrast, surfaces functionalized with serotonin itself fail to bind serotonin receptors. We infer that recognition by biomolecules evolved to distinguish small-molecule ligands in solution requires tethering of the latter via ectopic moieties. Membrane proteins, which are notoriously difficult to isolate, or other binding partners can be captured for identification, mapping, expression, and other purposes using this generalizable approach.

Creating Favorable Geometries for Directing Organic Photoreactions in Alkanethiolate Monolayers

“…Moonhee Kim, 1,2 J. Nathan Hohman, 1,2 Yang Cao, 1 Kendall N. Houk, 1 * Hong Ma, 3 Alex K.-Y. Jen, 3 * Paul S. Weiss 1,2,4 * The products of photoreactions of conjugated organic molecules may be allowed by selection rules but not observed in solution reactions because of unfavorable reaction geometries.…”

“…In the context of surface reactions, the formation of adsorbed monolayers can restrict the relative motion of molecules and may afford a route to regioselective chemistry. For example, n-alkanethiolate self-assembled monolayers (SAMs) on gold surfaces have been used to prepare well-defined matrices for studying molecules or nanoparticles in locally controlled environments (1)(2)(3). The stability, simple fabrication, and fundamental understanding of alkanethiolate SAMs provide an excellent system to control the placement, orientation, and reactions of molecules.…”

“…I n mammals, metabolic processes in peripheral organs display robust circadian rhythms, coordinated with the daily cycles of light and nutrient availability (1,2). Circadian misalignment causes metabolic dysfunction, and people engaged in night-shift work suffer from higher incidences of obesity, diabetes, and metabolic syndrome (3)(4)(5). The molecular basis of this is unknown, but genetic disruption of circadian clock components in mice leads to altered glucose and lipid metabolism (6)(7)(8)(9)(10).…”

Controlled DNA Patterning by Chemical Lift-Off Lithography: Matrix Matters

“…33,38,62 We have previously targeted and reached surface densities between ∼2 Â 10 12 molecules/cm 2 and 8 Â 10 13 molecules/cm 2 via insertion. 38,39 In comparison to the backfilling method, correlation analysis of XPS atomic percentages and fluorescence hybridization intensities showed improved hybridization efficiency associated with lower DNA probe surface coverages when using the insertion approach. Thus, we expect that the numbers of DNA probes inserted into post-liftoff MCU or MCHD SAMs are below the upper limit determined for backfilling.…”

Aptamer Recognition of Multiplexed Small-Molecule-Functionalized Substrates

“…23–25 Optimization entailed (1) spacing small-molecules for improved recognition by larger biomolecules via dilute solution deposition of tethering thiols during the preparation of mixed self-assembled monolayers (SAMs) or through the insertion of tethers into naturally existing or engineered defects in SAMs. 26–29 (2) We utilized the amino acid precursors of neurotransmitters for tethering via the additional carboxyl moiety to render amino groups more accessible for molecular recognition.…”