Chemistry & Biochemistry
Permanent URI for this communityhttp://hdl.handle.net/1903/11812
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Item Functionalized 3D DNA Crystals through Core-Shell and Layer-by-Layer Assembly(2019) McNeil, Ronald; Paukstelis, Paul; Biochemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A fundamental goal of DNA nanotechnology has been assembly of DNA crystals for use as molecular scaffolds to organize arrays of guest molecules. We use previously described 3D DNA crystals to demonstrate core-shell and layer-by-layer assembly of DNA crystals capable of accommodating tethered guest molecules within the crystals’ pervasive solvent channel network. We describe the first example of epitaxial biomacromolecular core-shell crystallization through assembly of the crystals in two or more discrete layers. The solvent channels also allow post-crystallization guest conjugation with layer-specific addressability. We present microfluidics techniques for core-shell crystal growth which unlock greater potential for finely tunable layer properties and assembling complex multifunctional crystals. We demonstrate assembly of these DNA crystals as nanoscale objects much smaller than previously observed. These techniques present new avenues for using DNA to create multifunctional micro- and nanoscale periodic biomaterials with tunable chemical and physical properties.Item A New Role for the CYT-18 N-Terminus and Three-Dimensional DNA Crystals as Vehicles for Biocatalysis(2014) Geng, Chun; Paukstelis, Paul J; Biochemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The bifunctional Neurospora crassa mitochondrial tyrosyl-tRNA synthetase (N. crassa mt TyrRS; CYT-18 protein) promotes the splicing of multiple group I introns by stabilizing the catalytically active intron structures. CYT-18, and mt TyrRS's from related fungal species, have evolved to promote group I intron splicing partly by accumulation of three N-terminal domain insertions that create a structure-stabilizing scaffold for critical tertiary interactions between the two major group I intron domains. The primarily alpha-helical N-terminal insertion, H0, contributes to protein stability and is necessary for splicing the N. crassa ND1 intron, but is dispensable for splicing the N. crassa mt LSU intron. Herein, I show CYT-18 with a complete H0 deletion retains residual ND1 intron splicing activity and addition of the missing N-terminus in trans restores a significant portion of its splicing activity. This peptide complementation assay revealed important characteristics of the CYT-18/group I intron interaction including the stoichiometry of H0 in intron splicing and the importance of specific H0 residues. Evaluation of truncated H0 peptides in this assay also suggests a previously unknown structural role of the first five N-terminal residues of CYT-18. These residues interact directly with another splicing insertion, making H0 a central structural element responsible for connecting all three N-terminal splicing insertions. Transitioning to a separate study, I have demonstrated that enzymes retain catalytic activity when captured in the solvent channels of three-dimensional (3D) DNA crystals. Using RNase A as a model enzyme system this work shows that crystals infused with enzyme can cleave a fluorescent dinucleotide substrate with similar kinetic restrictions as other immobilized enzyme systems, mainly limited by diffusion of substrate. This new vehicle for immobilized enzymes, created entirely from biomolecules, provides a platform for developing modular solid-state catalysts that could be both biocompatible and biodegradable.