Helical Organization Research Articles

Tuning the Liquid Crystallinity of Cholesteryl-o-Carborane Dyads: Synthesis, Structure, Photoluminescence, and Mesomorphic Properties

A set of mesomorphic materials in which the o-carborane cluster is covalently bonded to a cholesteryl benzoate moiety (mesogen group) through a suitably designed linker is described. The olefin cross-metathesis between appropriately functionalized styrenyl-o-carborane derivatives and a terminal alkenyl cholesteryl benzoate mesogen (all type I terminal olefins) leads to the desired trans-regioisomer, which is the best-suited configuration to obtain mesomorphic properties in the final materials. The introduction of different substituents (R = H (M2), Me (M3), or Ph (M4)) to one of the carbon atoms of the o-carborane cluster (Ccluster) enables the tailoring of liquid crystalline properties. Compounds M2 and M3 show the chiral nematic (N*) phase, whereas M4 do not show liquid crystal behavior. Weaker intermolecular interactions in the solid M3 with respect to those in M2 may allow the liquid crystallinity in M3 to be expressed as enantiotropic behavior, whereas breaking the stronger intermolecular interaction in the solid state of M2 leads directly to the isotropic state, resulting in monotropic behavior. Remarkably, M3 also displays the blue phase, which was observed neither in the chiral nematic precursor nor in the styrenyl-cholesterol model (M5) without an o-carborane cluster, which suggests that the presence of the cluster plays a role in stabilizing this highly twisted chiral phase. In the carborane-containing mesogens (M2 and M3), the o-carborane cluster can be incorporated without destroying the helical organization of the mesophase.

Collapsed mitochondrial cristae in goat spermatozoa due to mercury result in lethality and compromised motility along with altered kinematic patterns

Earlier we have reported mercury-induced alterations in functional dynamics of buck spermatozoa through free radicals-mediated oxidative stress and spontaneous acrosome reaction. Based on our earlier findings, we aimed to investigate the effect of mercury exposure on motility, kinematic patterns, DNA damage, apoptosis and ultra-structural alterations in goat spermatozoa following in vitro exposure to different concentrations (0.031–1.25 µg/ml) of mercuric chloride for 15 min and 3 h. Following exposure of sperm cells to 0.031 µg/ml of mercuric chloride for 3 h, livability and motility of sperms was significantly reduced along with altered kinematic patterns, significant increase in per cent necrotic sperm cells and number of cells showing DNA damage; and this effect was dose- and time-dependent. Contrary to up-regulation of Bax gene after 3 h in control group, there was significant increase in expression of Bcl-2 in mercury-treated groups. Transmission electron microscopy studies revealed rifts and nicks in plasma and acrosomal membrane, mitochondrial sheath, and collapsed mitochondria with loss of helical organization of mitochondria in the middle piece of spermatozoa. Our findings evidently suggest that mercury induces necrosis instead of apoptosis and targets the membrane, acrosome, mid piece of sperms; and the damage to mitochondria seems to be responsible for alterations in functional and kinematic attributes of spermatozoa.

Redox-Driven In Situ Helix Reversal of Graphene-Based Hydrogels.

Controlling the handedness of dynamic helical nanostructures of supramolecular assemblies by external stimuli is of great fundamental significance with appealing morphology-dependent applications. Significantly, access to in situ chirality transformation of dynamic multistimuli-responsive systems can provide channels for real-time monitoring of the transfer processes in biological systems. However, efforts to achieve helix inversion in an all-gel-state and to comprehend the phenomena at a molecular scale are scarce. Herein, we introduce an example of supramolecular hydrogel in which graphene oxide (GO) incorporation leads to opposite helicity of the l-phenylalanine derivative (LPFEG) upon UV irradiation. The gelator modulates different degrees of packing that are responsible for the initial construction of right-handed nanofibers in GO surfaces and for the change in helix to preferred left-handedness in RGO surfaces caused by GO reduction. Specifically, LPFEG shows a mixture of right- and left-handed nanofibers with an appropriate exposure to UV light. A thermal-reversible transformation of chirality is also discovered in the supramolecular assemblies, allowing a dynamic and invertible flip of helicity upon heating and cooling. The morphology transformation makes the hybrid an ideal candidate for application in a precisely controlled drug delivery process. It can unexpectedly serve as a photosensitizer and a carrier for enantioselective absorption of specific chiral drugs enantiomer (l-dopa and S-naproxen sodium) and also exhibit on-demand drug release due to the helix reversal induced by light irradiation. Our results illustrate how the surface reactivity can direct the helical organization of adsorbed fibers, which in turn provide control over enantioselective absorption of chiral drug enantiomers, further giving rise to on-demand drug release due to handedness inversion upon UV irradiation.

Three-dimensional alignment of microvasculature and cardiomyocytes in the developing ventricle

While major coronary artery development and pathologies affecting them have been extensively studied, understanding the development and organization of the coronary microvasculature beyond the earliest developmental stages requires new tools. Without techniques to image the coronary microvasculature over the whole heart, it is likely we are underestimating the microvasculature’s impact on normal development and diseases. We present a new imaging and analysis toolset to visualize the coronary microvasculature in intact embryonic hearts and quantify vessel organization. The fluorescent dyes DiI and DAPI were used to stain the coronary vasculature and cardiomyocyte nuclei in quail embryo hearts during rapid growth and morphogenesis of the left ventricular wall. Vessel and cardiomyocytes orientation were automatically extracted and quantified, and vessel density was calculated. The coronary microvasculature was found to follow the known helical organization of cardiomyocytes in the ventricular wall. Vessel density in the left ventricle did not change during and after compaction. This quantitative and automated approach will enable future cohort studies to understand the microvasculature’s role in diseases such as hypertrophic cardiomyopathy where misalignment of cardiomyocytes has been observed in utero.

Computational image analysis of the baseplate-tail complex of O1 ElTor vibriophage M4.

We performed an in-depth computational image analysis of the baseplate-tail complex of the M4 vibriophage and identified seven major densities in its baseplate, which notably share structural similarities with baseplate modules of a number of other bacteriophages belonging to different species. Employing computational analysis, we explained the helical organization of the sheath protein, wrapping the tail tube. Based on the results obtained in this work along with the proteomics information published previously, we are able to decipher the plausible roles assigned to the different components of the M4 baseplate during infection of the host.

Knotting a molecular strand can invert macroscopic effects of chirality.

Transferring structural information from the nanoscale to the macroscale is a promising strategy for developing adaptive and dynamic materials. Here we demonstrate that the knotting and unknotting of a molecular strand can be used to control, and even invert, the handedness of a helical organization within a liquid crystal. An oligodentate tris(2,6-pyridinedicarboxamide) strand with six point-chiral centres folds into an overhand knot of single handedness upon coordination to lanthanide ions, both in isotropic solutions and in liquid crystals. In achiral liquid crystals, dopant knotted and unknotted strands induce supramolecular helical organizations of opposite handedness, with dynamic switching achievable through in situ knotting and unknotting events. Tying the molecular knot transmits information regarding asymmetry across length scales, from Euclidean point chirality (constitutional chirality) via molecular entanglement (conformation) to liquid-crystal (centimetre-scale) chirality. The magnitude of the effect induced by the tying of the molecular knots is similar to that famously used to rotate a glass rod on the surface of a liquid crystal by synthetic molecular motors.

Assembly of Materials Building Blocks into Integrated Complex Functional Systems

Assembly of Materials Building Blocks into Integrated Complex Functional Systems

Metabotropic glutamate receptors (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

Metabotropic glutamate (mGlu) receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Metabotropic Glutamate Receptors [334]) are a family of G protein-coupled receptors activated by the neurotransmitter glutamate. The mGlu family is composed of eight members (named mGlu1 to mGlu8) which are divided in three groups based on similarities of agonist pharmacology, primary sequence and G protein coupling to effector: Group-I (mGlu1 and mGlu5), Group-II (mGlu2 and mGlu3) and Group-III (mGlu4, mGlu6, mGlu7 and mGlu8) (see Further reading).Structurally, mGlu are composed of three juxtaposed domains: a core G protein-activating seven-transmembrane domain (TM), common to all GPCRs, is linked via a rigid cysteine-rich domain (CRD) to the Venus Flytrap domain (VFTD), a large bi-lobed extracellular domain where glutamate binds. The structures of the VFTD of mGlu1, mGlu2, mGlu3, mGlu5 and mGlu7 have been solved [190, 262, 255, 386]. The structure of the 7 transmembrane (TM) domains of both mGlu1 and mGlu5 have been solved, and confirm a general helical organization similar to that of other GPCRs, although the helices appear more compacted [85, 415, 59]. mGlu form constitutive dimers crosslinked by a disulfide bridge. Recent studies revealed the possible formation of heterodimers between either group-I receptors, or within and between group-II and -III receptors [86]. Although well characterized in transfected cells, co-localization and specific pharmacological properties also suggest the existence of such heterodimers in the brain [422, 257]. The endogenous ligands of mGlu are L-glutamic acid, L-serine-O-phosphate, N-acetylaspartylglutamate (NAAG) and L-cysteine sulphinic acid. Group-I mGlu receptors may be activated by 3,5-DHPG and (S)-3HPG [29] and antagonized by (S)-hexylhomoibotenic acid [223]. Group-II mGlu receptors may be activated by LY389795 [256], LY379268 [256], eglumegad [337, 416], DCG-IV and (2R,3R)-APDC [338], and antagonised by eGlu [161] and LY307452 [408, 100]. Group-III mGlu receptors may be activated by L-AP4 and (R,S)-4-PPG [125]. An example of an antagonist selective for mGlu receptors is LY341495, which blocks mGlu2 and mGlu3 at low nanomolar concentrations, mGlu8 at high nanomolar concentrations, and mGlu4, mGlu5, and mGlu7 in the micromolar range [176]. In addition to orthosteric ligands that directly interact with the glutamate recognition site, allosteric modulators that bind within the TM domain have been described. Negative allosteric modulators are listed separately. The positive allosteric modulators most often act as ‘potentiators’ of an orthosteric agonist response, without significantly activating the receptor in the absence of agonist.

Investigations of Processing-Induced Structural Changes in Horse Type-I Collagen at Sub and Supramolecular Levels.

The aim of this work is to evaluate the effects of different extraction and material processing protocols on the collagen structure and hierarchical organization of equine tendons. Wide and Small Angle X-ray Scattering investigations on raw powders and thin films revealed that not only the extraction and purification treatments, but also the processing conditions may affect the extent of the protein crystalline domain and induce a nanoscale “shield effect.” This is due to the supramolecular fiber organization, which protects the atomic scale structure from the modifications that occur during fabrication protocols. Moreover, X-ray analyses and Fourier Transform Infrared spectroscopy performed on the biomaterial sheds light on the relationship between processing conditions, triple helical content and the organization in atomic and nanoscale domains. It was found that the mechanical homogenization of the slurry in acidic solution is a treatment that ensures a high content of super-organization of collagen into triple helices and a lower crystalline domain in the material. Finally, mechanical tensile tests were carried out, proving that the acidic solution is the condition which most enhances both mechanical stiffness and supramolecular fiber organization of the films.

Distinct Crystalline Aromatic Structural Motifs: Identification, Classification, and Implications.

Spatial noncovalent helical organization of nucleobases in DNA and radial organization of chromophores in natural light-harvesting systems are fascinating yet enigmatic. Understanding the numerous weak interactions that drive the formation of elegant supramolecular architectures in native natural systems and developing bioinspired design strategies have seen a surge of interest in recent decades. Self-assembly of functional chromophores in the crystalline phase is a definitive strategy to identify novel molecule-molecule interactions, in particular, atom-atom interactions, and to understand the synergistic nature of noncovalent interactions that stabilizes the supramolecular organization. This Account narrates our recent efforts in developing desirable supramolecular motifs employing weak interaction-based strategies and our observation of deviations from the common motifs chartered in aromatic systems. Modulation of long-range aromatic interactions through chemical modifications (acylation, benzoylation, haloacylation, and alkylation of chromophores) to attain a preferred stacking (herringbone, lamellar, or columnar) is presented. Particular attention has been given to attaining lamellar or columnar packing possessing potential interchromophoric electronic coupling mediated high charge mobility. Supramolecular arrangements of noncovalently or covalently associated donor-acceptor systems that open up additional possibilities of packing modes (segregated, mixed etc.) are explored. Our persistent efforts yielded distinct twisted-segregated and alternate distichous stacks for the nonparallel covalently linked donor-acceptor systems that favor a long-lived photoinduced charge-separated state. We further move on to discuss the unconventional packing motifs that were identified recently. The highly sought-after Greek cross (+) stacking of chromophores in crystalline phase and an elegant crystalline radial arrangement of chromophores are examined. The Greek cross (+) stacked architecture exhibits monomer-like emission characteristics owing to the absence of exciton coupling across the orthogonally stacked chromophores. Crystalline helical chromophore assembly is yet another emerging motif with far-reaching applications in domains ranging from asymmetric catalysis to chiral smart materials and has been accounted here by citing certain phenomenal examples from literature. Thus, this Account demonstrates that identifying and classifying new structural motifs based on topological aspects, such as interchromophoric orientation (cross) and extended chromophore arrangement in the crystal lattice (radial, helical, etc.), are crucial since such fundamental characteristics dictate the properties emerging out of the corresponding motifs. Encouraged from ours and others' works, we propose the addition of new aromatic supramolecular structural motifs, namely, cross-stacked, helical, and radial arrangements, in order to expand the classification. We believe that identifying new emergent property-based supramolecular motifs and investigating the methods to achieve the desired motif will eventually have implications in fundamental crystal engineering, supramolecular chemistry, and biomimetic design of functional materials.

Assessment of Chitosan Based Catalyst and their Mode of Action

Introduction:The popularity of chitosan is increasing among the researchers due to its environment friendly nature, high activity and easy approachability. Chitosan based catalysts are not only the most active and selective in catalytic reaction, but their “green” accessibility also makes them promising in organic catalysis. Chitosan is commonly extracted from chitin by alkaline deacetylation and it is the second abundant biopolymer in nature after cellulose. Chitosan based catalysts are advantageous by means of non-metallic activation as it involves small organic molecules. The robustness, nontoxicity, the lack of metal leaching possibility, inertness towards moisture and oxygen, easy handling and storage are the main advantages of organocatalysts. Traditional drawbacks associated with the metal-based heterogeneous catalysts, like longer reaction times during any synthesis, metal-leaching after every reaction and structural instability of the catalyst for prolonged recycling experiments are also very negligible for chitosan based catalysts. Besides, these catalysts can contribute more in catalysis due to their reusability and these special features increase their demand as the functionalized and profitable catalysts.Objective:The thorough description about the preparation of organocatalysts from chitosan and their uniqueness and novel activities in various famous reactions includes as the main aim of this review. Reusable and recycle nature of chitosan based organocatalysts gain the advantages over traditional and conventional catalyst which is further discussed over here.Methods and Discussions:In this article only those reactions are discussed where chitosan has been used both as support in heterogeneous catalysts or used as a catalyst itself without any co-catalyst for some reactions. Owing to its high biodegradability, nontoxicity, and antimicrobial properties, chitosan is widely-used as a green and sustainable polymeric catalyst in vast number of the reactions. Most of the preparations of catalyst have been achieved by exploring the complexation properties of chitosan with metal ions in heterogeneous molecular catalysis. Organocatalysis with chitosan is primarily discussed for carbon-carbon bond-forming reactions, carbon dioxide fixation through cyclo- addition reaction, condensation reaction and fine chemical synthesis reactions. Furthermore, its application as an enantioselective catalyst is also considered here for the chiral, helical organization of the chitosan skeleton. Moreover, another advantage of this polymeric catalyst is its easy recovery and reusability for several times under solvent-free conditions which is also explored in the current article.Conclusion:Important organocatalyzed reactions with either native chitosan or functionalized chitosan as catalysts have attracted great attention in the recent past. Also, chitosan has been widely used as a very promising support for the immobilization of catalytic metals for many reactions. In this review, various reactions have been discussed which show the potentiality of chitosan as catalyst or catalyst support.

Hybrid Nanocomposites for 3D Optics: Using Interpolymer Complexes with Cellulose Nanocrystals.

Manipulation of optical paths by three-dimensional (3D) integrated optics with customized stacked building blocks has gained considerable attention. Herein, we present functional thin films with assembly ability for 3D integrated optics based on nanocomposites made of cellulose nanocrystals (CNCs) embedded in hydrogen-bonded (H-bonded) interpolymer complexes (IPCs). We selected H-bonded IPC poly(ethylene oxide) and neutralized poly(acrylic acid) to render films assembly ability without undesired interplay with charge distribution in CNCs. The CNCs can form a stable chiral nematic liquid crystalline phase with long-range orientational order and helical organization. The resulting nanocomposites are characterized with a high elastic modulus of 8.8 GPa and an adhesion strength of 1.35 MPa through reversible intermolecular interactions at the contact interface upon exposure to acidic vapor. Instead, simply stacked into 3D optics, these functional thin films serve as a facile material for providing a conceptually simple approach to assemble 3D integrated optics with different liquid crystalline orderings to manipulate the light polarization state.

Photoresponsive Chiral Dopants: Light‐Driven Helicity Manipulation in Cholesteric Liquid Crystals for Optical and Mechanical Functions

AbstractThis Review focuses on recent advancements regarding the design of photoisomerizable chiral dopants which can switch the helical orientation in cholesteric liquid crystals upon light stimuli. Chiral dopants exhibiting conformational change in response to an external stimulus can provide dynamic control of the cholesteric pitch. Development of such responsive systems has been attempted since the 1970s. However, major advances on efficient chiral dopants exhibiting either high helical twisting power or large photoswitching have been achieved only in recent years. This Review covers photoresponsive low molecular weight cholesteric liquid crystal systems based on chiral dopants capable of photochemically “switching power to twist” surrounding liquid crystalline host molecules, “inverting” their handedness or even “inducing” helical organization from the racemic nematic phase.

Directing the Solid-State Organization of Racemates via Structural Mutation and Solution-State Assembly Processes.

Chirality plays a central role in biomolecular recognition and pharmacological activity of drugs and can even lead to new functions such as spin filters. Although there have been significant advances in understanding and controlling the helical organization of enantiopure synthetic molecular systems, rationally dictating the assembly of mixtures of enantiomer (including racemates) is nontrivial. Here we demonstrate that a subtle change in molecular structure coupled with the understanding of assembly processes of enantiomers and racemates, in both dilute solution and concentrated gels, acts as a stepping stone to rationally control the organization in the solid-state. We have studied trans-1,2-disubstituted cyclohexanes as model systems with carboxamide, thioamide, and their combination as functional groups. On comparing the gelation propensity of individual enantiomers and racemates, we find that racemates of carboxamide, thioamide, and their combination adopt self-sorting, coassembly, and mixed organization, respectively. Remarkably, these modes of assembly of racemates were also retained in solid-state. These results point out that studying the solution-phase assembly is a key link for connecting molecular structure with the assembly in the solid-state, even for racemates.

Confinement induces helical organization of chromosome-like polymers

Helical organization is commonly observed for a variety of biopolymers. Here we study the helical organization of two types of biopolymers, i.e., DNA-like semiflexible and bottle-brush polymers, in a cell-like confined space. A bottle-brush polymer consists of a backbone and side chains emanating from the backbone, resembling a supercoiled bacterial chromosome. Using computer simulations, we calculate ‘writhe’ distributions of confined biopolymers for a wide range of parameters. Our effort clarifies the conditions under which biopolymers are helically organized. While helical organization is not easily realized for DNA-like biomolecules, cylindrical confinement can induce spiral patterns in a bottle brush, similarly to what was observed with bacterial chromosomes. They also suggest that ring-shape bottle brushes have a stronger tendency for helical organization. We discuss how our results can be used to interpret chromosome experiments. For instance, they suggest that experimental resolution has unexpected consequences on writhe measurements (e.g., narrowing of the writhe distribution and kinetic separation of opposite helical states).

Chiral Photonic Cellulose Films Enabling Mechano/Chemo Responsive Selective Reflection of Circularly Polarized Light

AbstractStimuli‐responsive selective reflection of circularly polarized light in a broad wavelength range is of significance from scientific and technological viewpoints. Herein, chiral photonic cellulose films are fabricated which exhibit selective reflection of circularly polarized light responsive to mechanical and chemical stimuli. The chiral photonic cellulose films are highly deformable with the strain‐at‐break up to 40.8%, which is the highest among reported chiral photonic cellulose films. Selective reflection of left‐handed circularly polarized light responsive to bending and uniaxial tensioning across the entire visible spectrum is demonstrated, as well as reversible response to water vapor (10–100% relative humidity) from the visible to the near‐infrared region with Δλmax = 492 nm. The stimuli response is realized by alterable helical organization based on supramolecular chemistry. The current work provides a general strategy for rational design of multistimuli‐responsive selective reflection of circularly polarized light, and a soft material platform for scalable camouflaging and security materials.

Helical organization of microtubules occurs in a minority of tunneling membrane nanotubes in normal and cancer urothelial cells

Tunneling membrane nanotubes (TnTs) are membrane protrusions connecting nearby or distant cells in vitro and in vivo. Functions of TnTs in cellular processes are various and rely on TnT structure, which also depends on cytoskeletal composition. In the present study, we focused on the organization of microtubules (MTs) and intermediate filaments (IFs) in TnTs of urothelial cells. We analysed TnTs of normal porcine urothelial cells, which morphologically and physiologically closely resemble normal human urothelial cells, and of cancer cells derived from invasive human urothelial neoplasm. Wide-field fluorescence, confocal and super-resolution microscopy techniques, together with image analyses and 3D reconstructions enlightened specific MT-IF organization in TnTs, and for the first time revealed that MTs and IFs co-occur in the majority of normal and cancer urothelial cell TnTs. Our findings show that in the initiation segment of TnTs, MTs are cross-linked with each other into filamentous network, however in the middle and the attaching segment of TnT, MTs can helically enwrap IFs, the phenomenon that has not been shown before within the TnTs. In this study, we assess MT-IF co-occurrence in TnTs and present evidence that such helical organization of MTs enwrapping IFs is only occurring in a minority of the TnTs. We also discuss the possible cell-biological and physiological reasons for helical organization of MTs in TnTs.

Structural Studies of Alpha-Synuclein Amyloid Filaments

Amyloid filaments of the alpha-synuclein (alpha-Syn) protein are considered the hallmark of Parkinson's disease (PD) and no biomarkers for early diagnosis have yet been developed. Thioflavin T (ThT) is the most frequently used dye to detect amyloids. We are using cryo-EM of ThT-bound alpha-Syn fibrils of PD familial variants (e.g., A30P, E46K and, A53T) to understand its mechanism of binding. The heterogeneity of amyloid filaments has been one of the greatest obstacles to structural studies. We used the fluorescence of ThT to follow the kinetics of alpha-Syn fibril formation at different ionic strengths to control fibril length and sample homogeneity for cryo-EM studies. The results show we can modulate secondary nucleation events involved in filament growth (i.e., the fragmentation rate) using sodium chloride concentrations below 1mM. Controlled proteinase-K digestion coupled with electron-spray ionization mass spectrometry of the fibril variants revealed distinctly different filament structures. Additionally, the power spectra of A30P and A53T filaments showed the 1/4.7 Å-1 layer line typical of cross-beta amyloids but the two have distinctly different helical organization. The A53T power spectrum revealed that the 1/4.7 Å-1 layer line is not a meridional but arises from a 1-start helix. This shows that the two strands in the filament are staggered, with a rise per subunit of 4.7 Å within each protofilament. We have confirmed this symmetry using the Iterative Helical Real Space Reconstruction (IHRSR) method to generate near-atomic resolution density maps of these amyloid filaments. Understanding the molecular mechanism in which ThT binds to amyloids represents a first step for structure-guided design of small molecules that may act as biomarkers for early PD detection.

The dominant role of side chains in supramolecular double helical organisation in synthetic tripeptides

Peptide self-assembled nanostructures have attracted attention recently owing to their promising applications in diversified avenues. To validate the importance of sidechains in supramolecular architectural stabilization, herein this report describes the self-assembly propensities involving weak interactions in a series of model tripeptides Boc-Xaa-Aib-Yaa-OMe I–IV, (where Xaa = 4-F-Phe/NMeSer/Ile & Yaa = Tyr in peptide I–III respectively and Xaa = 4-F-Phe & Yaa = Ile in peptide IV) differing in terminal side chains. The solid state structural analysis reveals that tripeptide (I) displays supramolecular preference for double helical architecture. However, when slight modification has been introduced in the N-terminal side chains disfavour the double helical organisation (Peptide II and III). Indeed the peptides display sheet like ensemble within the framework. Besides replacement of C-terminal Tyr by Ile in peptide I even do not promote the architecture, emphasizing the dominant role of balance of side chains in stabilizing double helical organisation. The CD measurements, concentration dependant studies, NMR titrations and ROESY spectra are well in agreement with the solid state conformational investigation. Moreover the morphological experiments utilizing FE-SEM, support the heterogeneity present in the peptides. Thus this work may not only hold future promise in understanding the structure and function of neurodegenerative diseases but also assist in rational design of protein modification in biologically active peptides.

Impact of helical organization on the photovoltaic properties of oligothiophene supramolecular polymers.

Helical self-assembly of functional π-conjugated molecules offers unique photochemical and electronic properties in the spectroscopic level, but there are only a few examples that demonstrate their positive impact on the optoelectronic device level. Here, we demonstrate that hydrogen-bonded tapelike supramolecular polymers of a barbiturated oligo(alkylthiophene) show notable improvement in their photovoltaic properties upon organizing into helical nanofibers. A tapelike hydrogen-bonded supramolecular array of barbiturated oligo(butylthiophene) molecules was directly visualized by STM at a liquid-solid interface. TEM, AFM and XRD revealed that the tapelike supramolecular polymers further organize into helical nanofibers in solution and bulk states. Bulk heterojunction solar cells of the helical nanofibers and soluble fullerene showed a power conversion efficiency of 4.5%, which is markedly high compared to that of the regioisomer of butyl chains organizing into 3D lamellar agglomerates.