DNA-single walled carbon nanotube (SWNT) conjugates are emerging nanomaterials for the development of optical probes for imaging biological analytes. Our most recent collaborative research has proposed that short single stranded DNA-SWNT sensors are highly sensitive to minute concentrations of neuromodulators such as dopamine and norepinephrine. We present a computational study of self-assembly of short DNA polymers around SWNT. The replica exchange molecular dynamics (REMD) technique is employed to perform free energy calculations. The free energy landscape of short DNA structures around SWNT reveals the self-assembly of a ring DNA structure around the SWNT, in contrast to the formation of a helical DNA structure around SWNT suggested by prior experimental and theoretical studies. The ring structure of DNA occupies one of the global minima in the free energy landscape, while other global minima are occupied by helical structures. Additionally, experiments show that the putative ring DNA conformation formed by short DNA structures leads to suppression of SWNT baseline fluorescence of ring DNA-SWNT hybrids, as opposed to the relatively high SWNT fluorescence of DNA-SWNT hybrids with conventional helical DNA conformations. We hypothesize that the ring and helical conformations of DNA wrapping SWNT strongly modulates the relaxation pathway of excitons in DNA-SWNT hybrids, which we exploit for applications in imaging neuromodulation.

Ring DNA-carbon nanotube conjugates

2019 Spring National Meeting

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