Molecular-level helical stack of a nucleotide-appended oligo(p-phenylenevinylene) directed by supramolecular self-assembly with a complementary oligonucleotide as a template

Phase behavior of polymer dispersed liquid crystals, comparison between mean-field theory, and coarse-grained molecular dynamics simulations

We report a simulation methodology to quantitatively predict the thermodynamic behaviour (phase diagrams) of polymer mixtures, that exhibit phases with broken orientational symmetry. Our system consists of a binary mixture of short oligomers (NA = 4) and long rod-like mesogens (NB = 8). Using coarse-grained molecular dynamics (CGMD) simulations we infer the topology of the temperature-dependent free energy landscape, from the probability distributions of the components for a range of compositions. The mixture exhibits nematic (N) and smectic phases (Sm-A) as a function of two temperature scales, Tc, that governs the demixing transition, and TNI the nematic-isotropic temperature. Thus in addition to the isotropic (I), a nematic (N) phases observed in simulations of similar systems earlier we report the formation of a new entropy-stabilized phase separated smectic-A (Sm-A) phase with alternating mesogen-rich and oligomer-rich layers. Using the mean-field free energy for polymer-dispersed liquid crystals (PDLCs), with suitably chosen parameter values, we construct a mean-field phase diagram that matches those obtained from CGMD simulations. Our results are applicable to mixtures of synthetic and biological macromolecules that undergo phase separation and are orientable, thereby giving rise to the liquid crystalline phases. Our proposed methodology has a distinct advantage over other computational techniques in its applicability to systems with complex molecular interactions and in capturing the coarsening dynamics of systems involving multiple order parameters.

Probing Molecular Chirality on the Self-Assembly and Gelation of Naphthalimide-Conjugated Dipeptides

In this work, 1,8-naphthalimide (NMI)-conjugated three hybrid dipeptides constituted of a β-amino acid and an α-amino acid have been designed, synthesized, and purified. Here, in the design, the chirality of the α-amino acid was varied to study the effect of molecular chirality on the supramolecular assembly. Self-assembly and gelation of three NMI conjugates were studied in mixed solvent systems [water and dimethyl sulphoxide (DMSO)]. Interestingly, chiral NMI derivatives [NMI-βAla-^lVal-OMe (NLV) and NMI-βAla-^dVal-OMe (NDV)] formed self-supported gels, while the achiral NMI derivative [NMI-βAla-Aib-OMe, (NAA)] failed to form any kind of gel at 1 mM concentration and in a mixed solvent (70% water in DMSO medium). Self-assembly processes were thoroughly investigated using UV-vis spectroscopy, nuclear magnetic resonance (NMR), fluorescence, and circular dichroism (CD) spectroscopy. A J-type molecular assembly was observed in the mixed solvent system. The CD study indicated the formation of chiral assembled structures for NLV and NDV, which were mirror images of one another, and the self-assembled state by NAA was CD-silent. The nanoscale morphology of the three derivatives was studied using scanning electron microscopy (SEM). In the case of NLV and NDV, left- and right-handed fibrilar morphologies were observed, respectively. In contrast, a flake-like morphology was noticed for NAA. The DFT study indicated that the chirality of the α-amino acid influenced the orientation of π-π stacking interactions of naphthalimide units in the self-assembled structure that in turn regulated the helicity. This is a unique work where molecular chirality controls the nanoscale assembly as well as the macroscopic self-assembled state.

Tuning of the Supramolecular Helicity of Peptide-Based Gel Nanofibers

Helical supramolecular architectures play important structural and functional roles in biological systems. The helicity of synthetic molecules can be tuned mainly by the chiral manipulation of the system. However, tuning of helicity by the achiral unit of the molecules is less studied. In this work, the helicity of naphthalimide-capped peptide-based gel nanofibers is tuned by the alteration of methylene units present in the achiral amino acid. The inversion of supramolecular helicity has been extensively studied by CD spectroscopy and morphological analysis. The density functional theory (DFT) study indicates that methylene spacers influence the orientation of π-π stacking interactions of naphthalimide units in the self-assembled structure that regulates the helicity. This work illustrates a new approach to tuning the supramolecular chirality of self-assembled biomaterials.

Photoswitchable architecture transformation of a DNA-hybrid assembly at the microscopic and macroscopic scale

Molecular recognition-driven self-assembly employing single-stranded DNA (ssDNA) as a template is a promising approach to access complex architectures from simple building blocks. Oligonucleotide-based nanotechnology and soft-materials benefit from the high information storage density, self-correction, and memory function of DNA. Here we control these beneficial properties with light in a photoresponsive biohybrid hydrogel, adding an extra level of function to the system. An ssDNA template was combined with a complementary photo-responsive unit to reversibly switch between various functional states of the supramolecular assembly using a combination of light and heat. We studied the structural response of the hydrogel at both the microscopic and macroscopic scale using a combination of UV-vis absorption and CD spectroscopy, as well as fluorescence, transmission electron, and atomic force microscopy. The hydrogels grown from these supramolecular self-assembly systems show remarkable shape-memory properties and imprinting shape-behavior while the macroscopic shape of the materials obtained can be further manipulated by irradiation.

From Interaction to Function in DNA-Templated Supramolecular Self-Assemblies

DNA-templated self-assembly represents a rich and growing subset of supramolecular chemistry where functional self-assemblies are programmed in a versatile manner using nucleic acids as readily-available and readily-tunable templates. In this review, we summarize the different DNA recognition modes and the basic supramolecular interactions at play in this context. We discuss the recent results that report the DNA-templated self-assembly of small molecules into complex yet precise nanoarrays, going from 1D to 3D architectures. Finally, we show their emerging functions as photonic/electronic nanowires, sensors, gene delivery vectors, and supramolecular catalysts, and their growing applications in a wide range of area from materials to biological sciences.

Molecular architectonics of DNA for functional nanoarchitectures

DNA is the key biomolecule central to almost all processes in living organisms. The eccentric idea of utilizing DNA as a material building block in molecular and structural engineering led to the creation of numerous molecular-assembly systems and materials at the nanoscale. The molecular structure of DNA is believed to have evolved over billions of years, with structure and stability optimizations that allow life forms to sustain through the storage and transmission of genetic information with fidelity. The nanoscale structural characteristics of DNA (2 nm thickness and ca. 40-50 nm persistence length) have inspired the creation of numerous functional patterns and architectures through noncovalent conventional and unconventional base pairings as well as through mutual templating-interactions with small organic molecules and metal ions. The recent advancements in structural DNA nanotechnology allowed researchers to design new DNA-based functional materials with chemical and biological properties distinct from their parent components. The modulation of structural and functional properties of hybrid DNA ensembles of small functional molecules (SFMs) and short oligonucleotides by adapting the principles of molecular architectonics enabled the creation of novel DNA nanoarchitectures with potential applications, which has been termed as templated DNA nanotechnology or functional DNA nanoarchitectonics. This review highlights the molecular architectonics-guided design principles and applications of the derived DNA nanoarchitectures. The advantages and ability of functional DNA nanoarchitectonics to overcome the trivial drawbacks of classical DNA nanotechnology to fulfill realistic and practical applications are highlighted, and an outlook on future developments is presented.

Control of helical chirality in supramolecular chromophore-DNA architectures

Four different d- and l-configured chromophore-2'-deoxyuridine conjugates were applied to elucidate the helical chirality of their non-covalent assemblies along the d- and l-configured DNA templates by optical spectroscopy. There is no configuration-selective recognition between these nucleosides and the DNA templates. The helicity of the DNA assemblies is either controlled by the configuration of the DNA template or by the nucleoside configuration.

Construction of a DNA-Based Supramolecular Nanosheet That Emits Bluish-White Light from Charge-Transfer Excited States of the Nucleobases

1,ω-Inosinic acid-bearing bolaamphiphiles dI(18), dI(19), and dI(20) with a 3'-phosphorylated inosine as a universal base connected to each end of an oligomethylene chain were synthesized for the first time. Single-component self-assemblies of these bolaamphiphiles and their binary self-assemblies with salmon sperm DNA were studied by AFM; temperature-dependent UV absorption, fluorescence, and circular dichroism spectroscopy; and gel electrophoresis. The binary self-assembly of dI(20) and salmon sperm DNA (dI(20)-DNA) had a nanosheet structure with a homogeneous thickness of about 6 nm and widths of several micrometers. Interestingly, an aqueous solution of the nanosheets showed a broad absorption band originating from the charge-transfer (CT) states of the nucleobase in the long-wavelength region (>300 nm), and the molar absorptivity per nucleobase was calculated to be approximately 150 times that of single-stranded (dT20 and dA20) and double-stranded (dT20-dA20) oligonucleotides. In addition, a continuous and broad emission band originating from CT excited states of the nucleobases was observed in the visible region. These observations indicate that CT states of the nucleobases were formed and stabilized in the supramolecular nanosheet and that bluish white light was emitted from CT excited states of the nucleobases.

Self-Assembled Porphyrazine Nucleosides on DNA Templates: Highly Fluorescent Chromophore Arrays and Sizing Forensic Tandem Repeat Sequences

The formation of chromophore arrays using a DNA templating approach leads to the creation of supramolecular assemblies, where the optical properties of the overall system can be fine-tuned to a large extent. In particular, porphyrin derivatives have been shown to be versatile building blocks; mostly covalent chemistry was used for embedding the units into DNA strands. Self-assembly of porphyrin modified nucleosides, on the other hand, has not been investigated as a simplified approach. We report on the synthesis of a magnesium(II) tetraaza porphine (MgTAP) coupled to deoxyuridine, and array formation on DNA templates which contain well-defined oligo(dA) segments showing strong fluorescence enhancement which is significantly larger than that with a Zn-porphyrin. The use of the deep-eutectic solvent glycholine is essential for successful assembly formation. The system allows for sizing of short tandem repeat markers with multiple adenosines, thus the concept could be adaptable to in vitro forensic DNA profiling with a suitable set of different chromophores on all nucleosides.

Expanded Theory of H- and J-Molecular Aggregates: The Effects of Vibronic Coupling and Intermolecular Charge Transfer

The electronic excited states of molecular aggregates and their photophysical signatures have long fascinated spectroscopists and theoreticians alike since the advent of Frenkel exciton theory almost 90 years ago. The influence of molecular packing on basic optical probes like absorption and photoluminescence was originally worked out by Kasha for aggregates dominated by Coulombic intermolecular interactions, eventually leading to the classification of J- and H-aggregates. This review outlines advances made in understanding the relationship between aggregate structure and photophysics when vibronic coupling and intermolecular charge transfer are incorporated. An assortment of packing geometries is considered from the humble molecular dimer to more exotic structures including linear and bent aggregates, two-dimensional herringbone and "HJ" aggregates, and chiral aggregates. The interplay between long-range Coulomb coupling and short-range charge-transfer-mediated coupling strongly depends on the aggregate architecture leading to a wide array of photophysical behaviors.

DNA-Templated N(Me)-Alkoxyamine Glycosylation

The potential of N(Me)-alkoxyamine glycosylation as a DNA-templated ligation has been studied. On a hairpin stem-template model, a notable rate enhancement and an increased equilibrium yield are observed compared to the corresponding reaction without a DNA catalyst. The N-glycosidic connection is dynamic at pH 5, whereas it becomes irreversible at pH 7. The N(Me)-alkoxyamine glycosylation may hence be an attractive pH controlled reaction for the assembly of DNA-based dynamic products.

Redox-Active Peptide-Functionalized Quinquethiophene-Based Electrochromic π-Gel

An electrochromic system based on a self-assembled dipeptide-appended redox-active quinquethiophene π-gel is reported. The designed peptide-quinquethiophene consists of a symmetric bolaamphiphile that has two segments: a redox-active π-conjugated quinquethiophene core for electrochromism, and peptide motif for the involvement of molecular self-assembly. Investigations reveal that self-assembly and electrochromic properties of the π-gel are strongly dependent on the relative orientation of peptidic and quinquethiophene scaffolds in the self-assembly system. The colors of the π-gel film are very stable with fast and controlled switching speed at room temperature.

Visualization of periodic electric polarizability of helical nanofibers formed by self-assembly of nucleotide-bearing bolaamphiphiles and natural-source DNA as a template

The possibility of fabricating DNA-based electronics has attracted considerable attention, but constructing robust, functional DNA nanowires on hard substrates has proven to be difficult. This paper describes the production of robust one-dimensional nanofibers by self-assembly of 1,18-nucleotide-bearing bolaamphiphiles templated by salmon sperm DNA. Electrostatic force microscopy measurements of the nanofibers on a highly oriented pyrolytic graphite substrate revealed that they showed electric polarizability that varied periodically with a pitch of 20-30 nm. Atomic force microscopy, gel electrophoresis, and circular dichroism spectroscopy suggested that the periodic polarizability was derived from right-handed helicity induced by the template DNA. Salmon sperm DNA itself did not show electric polarizability.

Pendant-Type Helicene Oligomers with p-Phenylene Ethynylene Main Chains: Synthesis, Reversible Formation of Ladderlike Bimolecular Aggregates, and Control of Intramolecular and Intermolecular Aggregation

Pendant-type (P)-helicene oligomers with p-phenylene ethynylene main chains up to a tetramer were synthesized by a building block method. The (P)-tetramer reversibly formed a ladderlike bimolecular aggregate upon cooling and disaggregated upon heating in (trifluoromethyl)benzene. Two bis(tetramer)s, in which two (P)-tetramers were connected by hexadecamethylene linkers, were also synthesized. The head-to-tail bis(tetramer) formed an intramolecular aggregate, and the head-to-head bis(tetramer) formed an intermolecular aggregate in toluene. The results suggest the antiparallel aggregation structure of the pendant-type (P)-tetramers. The structure of the linker was proven to be effective in controlling intramolecular and intermolecular aggregations.

Supramolecular Helical Systems: Helical Assemblies of Small Molecules, Foldamers, and Polymers with Chiral Amplification and Their Functions

In this review, we describe the recent advances in supramolecular helical assemblies formed from chiral and achiral small molecules, oligomers (foldamers), and helical and nonhelical polymers from the viewpoints of their formations with unique chiral phenomena, such as amplification of chirality during the dynamic helically assembled processes, properties, and specific functionalities, some of which have not been observed in or achieved by biological systems. In addition, a brief historical overview of the helical assemblies of small molecules and remarkable progress in the synthesis of single-stranded and multistranded helical foldamers and polymers, their properties, structures, and functions, mainly since 2009, will also be described.

Investigation of Supramolecular Nanofibers Formed from Multicomponent Nucleotide-Appended Bolaamphiphiles and Heteropolymeric DNA as a Template

A novel DNA-templated multicomponent self-assembly of well-defined, molecular-level-controlled nanostructures in aqueous solution is demonstrated by using a thermal cycling procedure. The strategy uses four building blocks comprising 1,18-nucleotide-appended bolaamphiphiles (3'-phosphorylated adenosine, thymidine, guanosine, or cytidine connected to each end of an oligomethylene chain) and a heteropolymeric 58-mer containing a palindromic sequence as the template DNA. Atomic force microscopic observations, circular dichroism, and temperature-dependent absorption spectra revealed that the multicomponent self-assembly of the four nucleotide bolaamphiphiles and template DNA formed right-handed helical nanofibers with complementary base pairs during thermal cycling. Nanofibers were not formed if one of the four nucleotide bolaamphiphiles was missing, suggesting that construction of the helical nanofiber resulted from self-assembly of all four bolaamphiphiles to form matched base pairs sorted according to the sequence of the template DNA.

Double zipper helical assembly of deoxyoligonucleotides: mutual templating and chiral imprinting to form hybrid DNA ensembles

Herein, the conventional and unconventional hydrogen bonding potential of adenine in APA for double zipper helical assembly of deoxyoligonucleotides is demonstrated under ambient conditions. The quantum mechanical calculations supported the formation of hybrid DNA ensembles.

From nucleobase to DNA templates for precision supramolecular assemblies and synthetic polymers

In this minireview, we report on the recent advances of utilization of nucleobases and DNA as templates to achieve well-defined supramolecular polymers, synthetic polymers, and sequence-controlled polymers.

Accumulation of supramolecular nanoparticles self-assembled from a bola-shaped cytidylic acid-appended fluorescein dye in cell nuclei

We examined the cellular uptake of the nanoparticles self-assembled from a bola-shaped cytidylic acid-appended fluorescein derivative (C-FLU-C). The accumulation of fluorescence in the Caco-2 cell nucleus was observed mainly after the plateau phase of cell growth, indicating that C-FLU-C permeated the nuclear envelope without nuclear-localizing tags.

A dynamic combinatorial approach for identifying side groups that stabilize DNA-templated supramolecular self-assemblies

DNA-templated self-assembly is an emerging strategy for generating functional supramolecular systems, which requires the identification of potent multi-point binding ligands. In this line, we recently showed that bis-functionalized guanidinium compounds can interact with ssDNA and generate a supramolecular complex through the recognition of the phosphodiester backbone of DNA. In order to probe the importance of secondary interactions and to identify side groups that stabilize these DNA-templated self-assemblies, we report herein the implementation of a dynamic combinatorial approach. We used an in situ fragment assembly process based on reductive amination and tested various side groups, including amino acids. The results reveal that aromatic and cationic side groups participate in secondary supramolecular interactions that stabilize the complexes formed with ssDNA.

Synthesis, optical properties, and electronic structures of nucleobase-containing π-conjugated oligomers

The molecular recognition properties of the nucleobases instruct the formation of complex three-dimensional architectures in natural and synthetic systems; relatively unexplored is their use as building blocks for π-conjugated materials where they might mutually tune electronic and supramolecular structures. Toward this goal, an introductory set (1a-d and 2a-d) of six purine-terminated and two pyrimidine-terminated π-conjugated oligomers has been synthesized and used to develop experimental electronic and photophysical structure-property trends. Unlike 2,2':5',2″-terthiophene (TTT) derivatives 2a-d, intramolecular charge transfer dominates oligomers 1a-d bearing a 4,7-bisthienylbenzothiadiazole (TBT) spacer due to the strong electron-accepting ability of its benzothiadiazole (BTD) ring. The resulting donor-acceptor-donor systems feature lower HOMO-LUMO gaps than the terthiophene-linked nucleobases (ΔE(g) ∼ 1.8 eV vs 2.4 eV based on electrochemical measurements), and the lowest so far for π-conjugated molecules that include nucleobases within the π-framework. Experiments reveal a dependence of photophysical and electronic structure on the nature of the nucleobase and are in good agreement with theoretical calculations performed at the B3LYP/6-31+G** level. Overall, the results show how nucleobase heterocycles can be installed within π-systems to tune optical and electronic properties. Future work will evaluate the consequences of these information-rich components on supramolecular π-conjugated structure.

Synthesis and structural analysis of tungsten-carbonyl dimers bridged with oligo(2,5-dialkoxy-1,4-phenylene vinylene)s through pyridine coordination

Synthesis, structural analysis and basic optical properties of tungsten carbonyl dimers bridged with oligo(2,5-dialkoxy-1,4-phenylene vinylene)s through coordination with pyridine have been explored.

Nanoarchitectonics of biomolecular assemblies for functional applications

The stringent processes of natural selection and evolution have enabled extraordinary structure-function properties of biomolecules. Specifically, the archetypal designs of biomolecules, such as amino acids, nucleobases, carbohydrates and lipids amongst others, encode unparalleled information, selectivity and specificity. The integration of biomolecules either with functional molecules or with an embodied functionality ensures an eclectic approach for novel and advanced nanotechnological applications ranging from electronics to biomedicine, besides bright prospects in systems chemistry and synthetic biology. Given this intriguing scenario, our feature article intends to shed light on the emerging field of functional biomolecular engineering.

Synthesis and Self-Assembly of a Mikto-Arm Star Dual Drug Amphiphile Containing both Paclitaxel and Camptothecin

Self-assembly of anticancer therapeutics into discrete nanostructures provides an innovative way to develop a self-delivering nanomedicine with a high, quantitative drug loading. We report here the synthesis and assembly of a mikto-arm star dual drug amphiphile (DA) containing both a bulky paclitaxel (PTX) and a planar camptothecin (CPT). The two anti-cancer drugs of interest were stochastically conjugated to a β-sheet forming peptide (Sup35) and under physiologically-relevant conditions the dual DA could spontaneously associate into supramolecular filaments with a fixed 41% total drug loading (29% PTX and 12% CPT). Transmission electron microscopy imaging and circular dichroism spectroscopy studies reveal that the bulkiness of the PTX, as well as the π-π interaction preference between the CPT units, has a significant impact on the assembly kinetics, molecular level packing, and nanostructure morphology and stability. We found that the DA containing two PTX units assembled into non-filamentous micelle-like structures, in contrast to the filamentous structures formed by the hetero dual DA and the DA containing two CPTs. The hetero dual DA was found to effectively release the two anticancer agents, exhibiting superior cytotoxicity against PTX-resistant cervical cancer cells. The presented work offers a potential method to generate well-defined entwined filamentous nanostructures and provides the basis for a future combination therapy platform.

The evolution of self-assemblies in the mixed system of oleic acid-diethylenetriamine based on the transformation of electrostatic interactions and hydrogen bonds

With the aid of pH variation, the fine control of the electrostatic interaction and hydrogen bond was realised in the mixed system of oleic acid and diethylenetriamine. Owing to the transformation of the intermolecular interactions, the corresponding building blocks changed from DETA(2+)@2OA(-)via the coexistence of DETA@2OA(-) and DETA(+)@OA(-) to DETA@2OA(-). Therefore, diverse microstructures and phase behaviors in this mixed surfactant system were obtained at the different pH values. It is found that the fine control of the electrostatic interaction and hydrogen bond is efficient for tailoring the self-assembled structures in this cationic-anionic surfactant system, including vesicles, bilayers, networks formed by aggregated vesicles and fibers.

Self-assembly of DNA-oligo(p-phenylene-ethynylene) hybrid amphiphiles into surface-engineered vesicles with enhanced emission

Surface-addressable nanostructures of linearly π-conjugated molecules play a crucial role in the emerging field of nanoelectronics. Herein, by using DNA as the hydrophilic segment, we demonstrate a solid-phase "click" chemistry approach for the synthesis of a series of DNA-chromophore hybrid amphiphiles and report their reversible self-assembly into surface-engineered vesicles with enhanced emission. DNA-directed surface addressability of the vesicles was demonstrated through the integration of gold nanoparticles onto the surface of the vesicles by sequence-specific DNA hybridization. This system could be converted to a supramolecular light-harvesting antenna by integrating suitable FRET acceptors onto the surface of the nanostructures. The general nature of the synthesis, surface addressability, and biocompatibility of the resulting nanostructures offer great promises for nanoelectronics, energy, and biomedical applications.

Syntheses, Structures, Characterisation, and Spectroscopic Properties of CuI and AgI Complexes with Extended C–H···π and π···π Interactions

Based on the ligands N,N′-bis(pyridin-2-ylmethylene)benzene-1,4-diamine (pmb) and N,N′-bis(pyridin-2-ylmethylene)biphenyl-4,4′-diamine (pmbb), the three compounds [Cu2(pmb) (PPh3)2(Cl)2] (1), [Cu2(pmbb)(CH3CN)2(PPh3)2](BF4)2·2DMF (2), and [Ag2(pmbb)(PPh3)2] (ClO4)2 (3) have been synthesised and characterised. Structural analysis reveals that all of these complexes contain 1D supramolecular arrays, with different variations in π-stacking patterns and intermolecular C–H···π interactions. Crystal structures of 1 and 2 contain 1D tape-like arrays formed by C–H···π and π···π interactions, and an ordered-layer-lattice of DMF and BF4– in 2 is located between the one-dimensional array. For 3, π-stacking interactions lead to the construction of 1D supramolecular arrays and a 2D network. The results indicate that C–H···π and π···π interactions play an important role in the construction of the supramolecular structure. In addition, the absorption peaks of complexes 1 and 3 in the solid state at room temperature show intraligand charge transfer and metal-to-ligand charge transfer absorptions. The optical and fluorescent properties of 2 were also studied in acetonitrile solution at room temperature.

Binding and supramolecular organization of homo- and heterotelechelic oligomers in solutions

Solvent can subtly influence the organization of supramolecular polymers.

Progressive macromolecular self-assembly: from biomimetic chemistry to bio-inspired materials

Macromolecular self-assembly (MSA) has been an active and fruitful research field since the 1980s, especially in this new century, which is promoted by the remarkable developments in controlled radical polymerization in polymer chemistry, etc. and driven by the demands in bio-related investigations and applications. In this review, we try to summarize the trends and recent progress in MSA in relation to biomimetic chemistry and bio-inspired materials. Our paper covers representative achievements in the fabrication of artificial building blocks for life, cell-inspired biomimetic materials, and macromolecular assemblies mimicking the functions of natural materials and their applications. It is true that the current status of the deliberately designed and obtained nano-objects based on MSA including a variety of micelles, multicompartment vesicles, and some hybrid and complex nano-objects is at their very first stage to mimic nature, but significant and encouraging progress has been made in achieving a certain similarity in morphologies or properties to that of natural ones. Such achievements also demonstrate that MSA has played an important and irreplaceable role in the grand and long-standing research of biomimetic and bio-inspired materials, the future success of which depends on mutual and persistent efforts in polymer science, material science, supramolecular chemistry, and biology.

Supramolecular hydrogels formed by the conjugates of nucleobases, Arg-Gly-Asp (RGD) peptides, and glucosamine

Here we report the generation of a novel class of supramolecular hydrogelators based on the integration of nucleobase, Arg-Gly-Asp (RGD) peptides, and glucosamine in a single molecule. These novel small molecule hydrogelators self-assemble in water to form stable supramolecular nanofibers/hydrogels and exhibit useful biostability. This approach provides a new opportunity for systematic exploration of the self-assembly of small biomolecules by varying any individual segment to generate a large array of supramolecular hydrogels for biological functions and for biomedical applications.

Porphyrin-DNA conjugates: porphyrin induced adenine-guanine homoduplex stabilization and interduplex assemblies

DNA has found widespread uses as a nanosized scaffold for assembly of patterned multichomophoric nanostructures. Herein we report the synthesis, self-assembly, stability, and spectroscopic studies of short alternating non-self-complementary DNA sequences 5'-(dGdA)(4) and 5'-(dAdG)(4) with non-charged tetraarylporphyrins covalently linked to the 5' position of deoxyadenosine or deoxyguanosine via a phosphate or amide linker. The linker, the metal in the porphyrin coordination center, and the neighboring nucleobase have very distinct effects on the duplex formation of porphyrin-deoxyguanosine-deoxyadenosine oligodeoxynucleotides. At ionic strength between 5 mM and 40 mM, free base trispyridylphenylporphyrin appended to the 5' termini of 5'-(dAdG)(4) oligonucleotide via short non-polar amide linker served as a hydrophobic molecular cap inducing deoxyadenosine-deoxyguanosine antiparallel homoduplex. At ionic strength of ≥60 mM, the free base porphyrin functioned as a molecular 'glue' and induced the formation of porphyrin-DNA inter-homoduplex assemblies with characteristic tetrasignate CD Cotton effects in the porphyrin Soret band region. When the porphyrin cap was covalently attached to 5' position of deoxyguanosine or deoxyadenosine via charged phosphate linker, no significant deoxyadenosine-deoxyguanosine hybridization was observed even at elevated ionic strengths.