Translation of Deoxyribonucleic Acid into Synthetic Alpha Helical Peptides for Darwinian Evolution.

DNA-encoded libraries connect the phenotypes of synthetic molecules to a DNA barcode; however, most libraries do not tap into the potential of Darwinian evolution. Herein, we report a DNA-templated synthesis (DTS) architecture to make peptides that are stabilized into α-helical conformations via head-to-tail supramolecular cyclization. Using a pilot library targeting MDM2, we show that repeated screening can amplify a binder from the lowest abundance in the library to a ranking that correlates to binding affinity.

Suprastapled Peptides: Hybridization-Enhanced Peptide Ligation and Enforced α-Helical Conformation for Affinity Selection of Combinatorial Libraries.

Stapled peptides with an enforced α-helical conformation have been shown to overcome major limitations in the development of short peptides targeting protein-protein interactions (PPIs). While the growing arsenal of methodologies to staple peptides facilitates their preparation, stapling methodologies are not broadly embraced in synthetic library screening. Herein, we report a strategy leveraged on hybridization of short PNA-peptide conjugates wherein nucleobase driven assembly facilitates ligation of peptide fragments and constrains the peptide's conformation into an α-helix.

Structural basis of human separase regulation by securin and CDK1-cyclin B1.

In early mitosis, the duplicated chromosomes are held together by the ring-shaped cohesin complex. Separation of chromosomes during anaphase is triggered by separase-a large cysteine endopeptidase that cleaves the cohesin subunit SCC1 (also known as RAD21). Separase is activated by degradation of its inhibitors, securin and cyclin B, but the molecular mechanisms of separase regulation are not clear.

Biosupramolecular Systems: Integrating Cues into Responses.

Life is orchestrated by biomolecules interacting in complex networks of biological circuitry with emerging function. Progress in different areas of chemistry has made the design of systems that can recapitulate elements of such circuitry possible. Herein we review prominent examples of networks, the methodologies available to translate an input into various outputs, and speculate on potential applications and directions for the field.

Peptide nucleic acid (PNA) and its applications in chemical biology, diagnostics, and therapeutics.

Peptide nucleic acid (PNA) stands as one of the most successful artificial oligonucleotide mimetics. Salient features include the stability of hybridization complexes (either as duplexes or triplexes), metabolic stability, and ease of chemical modifications. These features have enabled important applications such as antisense agents, gene editing, nucleic acid sensing and as a platform to program the assembly of PNA-tagged molecules.

Clickable PNA Probes for Imaging Human Telomeres and Poly(A) RNAs.

The ability to bind strongly to complementary nucleic acid sequences, invade complex nucleic acid structures, and resist degradation by cellular enzymes has made peptide nucleic acid (PNA) oligomers as very useful hybridization probes in molecular diagnosis. For such applications, the PNA oligomers have to be labeled with appropriate reporters as they lack intrinsic labels that can be used in biophysical assays. Although solid-phase synthesis is commonly used to attach reporters onto PNA, development of milder and modular labeling methods will provide access to PNA oligomers labeled with a wider range of biophysical tags.

Probing the competition between duplex and G-quadruplex/i-motif structures using a conformation-sensitive fluorescent nucleoside probe.

Double-stranded segments of a genome that can potentially form G-quadruplex (GQ) and/or i-motif (iM) structures are considered to be important regulatory elements. Hence, the development of a common probe that can detect GQ and iM structures and also distinguish them from a duplex structure will be highly useful in understanding the propensity of such segments to adopt duplex or non-canonical four-stranded structures. Here, we describe the utility of a conformation-sensitive fluorescent nucleoside analog, which was originally developed as a GQ sensor, in detecting the iM structures of C-rich DNA oligonucleotides (ONs).

A Lucifer-Based Environment-Sensitive Fluorescent PNA Probe for Imaging Poly(A) RNAs.

Fluorescence-based oligonucleotide (ON) hybridization probes greatly aid the detection and profiling of RNA sequences in cells. However, certain limitations such as target accessibility and hybridization efficiency in cellular environments hamper their broad application because RNAs can form complex and stable structures. In this context, we have developed a robust hybridization probe suitable for imaging RNA in cells by combining the properties of 1) a new microenvironment-sensitive fluorescent nucleobase analogue, obtained by attaching the Lucifer chromophore (1,8-naphthalimide) at the 5-position of uracil, and 2) a peptide nucleic acid (PNA) capable of forming stable hybrids with RNA.

Responsive Fluorescent PNA Analogue as a Tool for Detecting G-quadruplex Motifs of Oncogenes and Activity of Toxic Ribosome-Inactivating Proteins.

Fluorescent oligomers that are resistant to enzymatic degradation and report their binding to target oligonucleotides (ONs) by changes in fluorescence properties are highly useful in developing nucleic-acid-based diagnostic tools and therapeutic strategies. Here, we describe the synthesis and photophysical characterization of fluorescent peptide nucleic acid (PNA) building blocks made of microenvironment-sensitive 5-(benzofuran-2-yl)- and 5-(benzothiophen-2-yl)-uracil cores. The emissive monomers, when incorporated into PNA oligomers and hybridized to complementary ONs, are minimally perturbing and are highly sensitive to their neighboring base environment.

A base-modified PNA-graphene oxide platform as a turn-on fluorescence sensor for the detection of human telomeric repeats.

Given the biological and therapeutic significance of telomeres and other G-quadruplex forming sequences in human genome, it is highly desirable to develop simple methods to study these structures, which can also be implemented in screening formats for the discovery of G-quadruplex binders. The majority of telomere detection methods developed so far are laborious and use elaborate assay and instrumental setups, and hence, are not amenable to discovery platforms. Here, we describe the development of a simple homogeneous fluorescence turn-on method, which uses a unique combination of an environment-sensitive fluorescent nucleobase analogue, the superior base pairing property of PNA, and DNA-binding and fluorescence quenching properties of graphene oxide, to detect human telomeric DNA repeats of varying lengths.