11 research outputs found
2,3;5,6-Di-O-isopropylidene-1-O-(2-phenylacetyl)-α-d-mannofuranose
The title compound, C20H26O7, was prepared by esterification of 2,3;5,6-di-O-isopropylidene-α-d-mannofuranose with phenylacetic acid under standard DCC/DMAP (DCC = dicyclohexylcarbodiimide and DMAP = 4-dimethylaminopyridine) conditions. The solid-state structure confirms the retention of the α-configuration at the anomeric C atom. The compound is characterized by a relatively rigid framework with only a few degrees of freedom. Comparison with other di-O-isopropylidenemannofuranose derivatives shows the main differences to be associated with the flexible dimethyldioxolane ring, and that there are only small differences for the 2,3-O-isopropylidene-α-d-mannofuranose backbone. The packing is marked by a large number of weak C—H⋯O interactions
Effect of Steric Constraint at the γ-Backbone Position on the Conformations and Hybridization Properties of PNAs
Conformationally preorganized peptide nucleic acids (PNAs) have been synthesized through backbone modifications at the γ-position, where R = alanine, valine, isoleucine, and phenylalanine side chains. The effects of these side-chains on the conformations and hybridization properties of PNAs were determined using a combination of CD and UV-Vis spectroscopic techniques. Our results show that the γ-position can accommodate varying degrees of sterically hindered side-chains, reaffirming the bimodal function of PNAs as the true hybrids of “peptides” and “nucleic acids.
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Conformationally preorganized peptide nucleic acids (PNAs) have been synthesized through backbone modifications at the γ-position, where R = alanine, valine, isoleucine, and phenylalanine side chains. The effects of these side-chains on the conformations and hybridization properties of PNAs were determined using a combination of CD and UV-Vis spectroscopic techniques. Our results show that the γ-position can accommodate varying degrees of sterically hindered side-chains, reaffirming the bimodal function of PNAs as the true hybrids of "peptides" and "nucleic acids."
Gamma Peptide Nucleic Acids: As Orthogonal Nucleic Acid Recognition Codes for Organizing Molecular Self-Assembly
Nucleic acids are
an attractive platform for organizing molecular
self-assembly because of their specific nucleobase interactions and
defined length scale. Routinely employed in the organization and assembly
of materials <i>in vitro</i>, however, they have rarely
been exploited <i>in vivo</i>, due to the concerns for enzymatic
degradation and cross-hybridization with the host’s genetic
materials. Herein we report the development of a tight-binding, orthogonal,
synthetically versatile, and informationally interfaced nucleic acid
platform for programming molecular interactions, with implications
for <i>in vivo</i> molecular assembly and computing. The
system consists of three molecular entities: the right-handed and
left-handed conformers and a nonhelical domain. The first two are
orthogonal to each other in recognition, while the third is capable
of binding to both, providing a means for interfacing the two conformers
as well as the natural nucleic acid biopolymers (i.e., DNA and RNA).
The three molecular entities are prepared from the same monomeric
chemical scaffold, with the exception of the stereochemistry or lack
thereof at the γ-backbone that determines if the corresponding
oligo adopts a right-handed or left-handed helix, or a nonhelical
motif. These conformers hybridize to each other with exquisite affinity,
sequence selectivity, and level of orthogonality. Recognition modules
as short as five nucleotides in length are capable of organizing molecular
assembly
Synthesis and characterization of conformationally preorganized, (R)-diethylene glycol-containing γ-peptide nucleic acids with superior hybridization properties and water solubility.
Developed in the early 1990s, peptide nucleic acid (PNA) has emerged as a promising class of nucleic acid mimic because of its strong binding affinity and sequence selectivity toward DNA and RNA and resistance to enzymatic degradation by proteases and nucleases; however, the main drawbacks, as compared to other classes of oligonucleotides, are water solubility and biocompatibility. Herein we show that installation of a relatively small, hydrophilic (R)-diethylene glycol ("miniPEG", R-MP) unit at the γ-backbone transforms a randomly folded PNA into a right-handed helix. Synthesis of optically pure (R-MP)γPNA monomers is described, which can be accomplished in a few simple steps from a commercially available and relatively cheap Boc-l-serine. Once synthesized, (R-MP)γPNA oligomers are preorganized into a right-handed helix, hybridize to DNA and RNA with greater affinity and sequence selectivity, and are more water soluble and less aggregating than the parental PNA oligomers. The results presented herein have important implications for the future design and application of PNA in biology, biotechnology, and medicine, as well as in other disciplines, including drug discovery and molecular engineering.</p
Bionanocomposites: Differential Effects of Cellulose Nanocrystals on Protein Diblock Copolymers
We investigate the effects of mixing
a colloidal suspension of
tunicate-derived cellulose nanocrystals (t-CNCs) with aqueous colloidal
suspensions of two protein diblock copolymers, EC and CE, which bear
two different self-assembling domains (SADs) derived from elastin
(E) and the coiled-coil region of cartilage oligomeric matrix protein
(C). The resulting aqueous mixtures reveal improved mechanical integrity
for the CE+t-CNC mixture, which exhibits an elastic gel network. This
is in contrast to EC+t-CNC, which does not form a gel, indicating
that block orientation influences the ability to interact with t-CNCs.
Surface analysis and interfacial characterization indicate that the
differential mechanical properties of the two samples are due to the
prevalent display of the E domain by CE, which interacts more with
t-CNCs leading to a stronger network with t-CNCs. On the other hand,
EC, which is predominantly C-rich on its surface, does not interact
as much with t-CNCs. This suggests that the surface characteristics
of the protein polymers, due to folding and self-assembly, are important
factors for the interactions with t-CNCs, and a significant influence
on the overall mechanical properties. These results have interesting
implications for the understanding of cellulose hydrophobic interactions,
natural biomaterials and the development of artificially assembled
bionanocomposites