Formation Of Molecular Assemblies Research Articles

Crystal Structure, quantum chemical analysis and apoptotic propensity of diaryl substituted α-aminophosphonates as selected C[sbnd]P bonded systems

Three component Kabachnik-Fields reaction under sonochemical conditions was utilized for synthesizing library of electronically diverse aryl substituted α-aminophosphonates as representative carbon phosphorus bonded systems. Single crystal X-ray structures of four novel α-aminophosphonate derivatives with comprehensive Hirshfeld surface analysis for highlighting influence of different functionalities over α-aminophosphonate motif on the crystal packing pattern and formation of molecular assemblies via supramolecular aggregation have been presented. Solid state absorption and photoluminescence studies corroborated electronic and crystal packing influences. The computational methodologies for evaluating quantum chemical descriptors of electronic properties of α-aminophosphonates were bench marked. The bioactivity potential of synthesized library of α- aminophosphonates was evaluated from their cytotoxic propensity towards human cancer lines in NCI-60 panel via SRB assay. The screened derivatives showed a range of cytotoxicity against cancer cell lines in NCI-60 panel. Compound 3 exhibited highest cell growth inhibition in prostate cancer cells with IC50 value of 10.94 μM. For mechanistic insights apoptotic propensity was evaluated using caspase-3 enzyme assay in PC-3 cells. The onset of apoptosis via caspase-3 activation was evidenced as a major pathway from morphological changes under fluorescence microscope with and without DAPI staining. The triggering of apoptosis via caspase 3 activation by the lead compound 3 was also confirmed from western blot analysis of PARP-1 in PC-3 cancer cells. Furthermore, the anti-metastatic potential of compound 3 can be predicted from its efficacy in restricting the migration of PC-3 cancer cells under in vitro conditions observed from wound healing assay.

Supramolecular Chemistry of a Moving Solution: Flow Drives New Non-covalent Bond Formation

The main concern in supramolecular chemistry is the creation of new non-covalent bonds because it leads to the formation of molecular assemblies with new functions. In organic synthesis, there are appropriate toolkits for creating a desired molecule; for example, catalysts produce a variety of new covalent bonds to extend the possible molecular structures. However, in supramolecular chemistry, self-assembly, a passive process, is still the sole method for forming non-covalent bonds. We demonstrated that when a solution moves in a microspace, a positive assembly occurs, leading to the formation of various new non-covalent bonds. Combining this strategy with the precise control of microenvironmental changes in a microflow space will expand the framework of supramolecular structures. New non-covalent bond formation should lead to the formation of molecular assemblies with new functions. In supramolecular chemistry, self-assembly, a passive process, is still the sole method for forming non-covalent bonds. One may consider that the motion of a solution has no significant influence on the molecular interactions; however, it can provide a driving force to induce non-covalent bonds at the molecular level. We demonstrated that when a solution moves in a microspace, a positive assembly occurs, leading to the formation of various new non-covalent bonds. In our system, microflow space serves as a catalyst for non-covalent bond formation; it remarkably accelerates non-covalent bond formation with favorable collision and energetic and steric effects.

Using Nanoscopic Solvent Defects for the Spatial and Temporal Manipulation of Single Assemblies of Molecules.

Here we report the use of defects in ordered solvents to form, manipulate, and characterize individual molecular assemblies of either small-molecule amphiphiles or polymers. The approach exploits nanoscopic control of the structure of nematic solvents (achieved by the introduction of topological defects) to trigger the formation of molecular assemblies and the subsequent manipulation of defects using electric fields. We show that molecular assemblies formed in solvent defects slow defect motion in the presence of an electric field and that time-of-flight measurements correlate with assembly size, suggesting methods for the characterization of single assemblies of molecules. Solvent defects are also used to transport single assemblies of molecules between solvent locations that differ in composition, enabling the assembly and disassembly of molecular "nanocontainers". Overall, our results provide new methods for studying molecular self-assembly at the single-assembly level and new principles for integrated nanoscale chemical systems that use solvent defects to transport and position molecular cargo.

Synergism and antagonism in plant acclimation to abiotic stress combinations

Acclimation of plants to their environment involves mechanisms at all molecular levels and only the complete temporal and spatial pattern adequately describes the acclimation state. The diversity of physiological states realized in plants increases by the essentially infinite combinations of abiotic and biotic stresses, considering duration, impact order, and strength. The interference between stressors involves phenomena of synergism, antagonism, and indifference. This review exemplarily sketches principles of interference considering posttranslational modifications, the formation of molecular assemblies in regulosomes, the regulation of gene expression, and the vast number of other posttranscriptional controls e.g., in RNA processing and recruitment to ribosomes. Small molecules such as hormones, reactive molecular species as ROS, ions, and metabolites are decisive players in this network. Available methodology for global analysis combined with machine learning approaches offers a perspective to identify the central regulatory modules, particularly if the multiple layers of molecular regulation are included in parallel, and to better understand the underlying mechanisms of stress interference in an unbiased manner.

Influence of electrospray deposition on C60 molecular assemblies.

Maintaining clean conditions for samples during all steps of preparation and investigation is important for scanning probe studies at the atomic or molecular level. For large or fragile organic molecules, where sublimation cannot be used, high-vacuum electrospray deposition is a good alternative. However, because this method requires the introduction into vacuum of the molecules from solution, clean conditions are more difficult to be maintained. Additionally, because the presence of solvent on the surface cannot be fully eliminated, one has to take care of its possible influence. Here, we compare the high-vacuum electrospray deposition method to thermal evaporation for the preparation of C60 on different surfaces and compare, for sub-monolayer coverages, the influence of the deposition method on the formation of molecular assemblies. Whereas the island location is the main difference for metal surfaces, we observe for alkali halide and metal oxide substrates that the high-vacuum electrospray method can yield single isolated molecules accompanied by surface modifications.

Temperature and salt controlled tuning of protein clusters.

The formation of molecular assemblies in protein solutions is of strong interest both from a fundamental viewpoint and for biomedical applications. While ordered and desired protein assemblies are indispensable for some biological functions, undesired protein condensation can induce serious diseases. As a common cofactor, the presence of salt ions is essential for some biological processes involving proteins, and in aqueous suspensions of proteins can also give rise to complex phase diagrams including homogeneous solutions, large aggregates, and dissolution regimes. Here, we systematically study the cluster formation approaching the phase separation in aqueous solutions of the globular protein BSA as a function of temperature (T), the protein concentration (cp) and the concentrations of the trivalent salts YCl3 and LaCl3 (cs). As an important complement to structural, i.e. time-averaged, techniques we employ a dynamical technique that can detect clusters even when they are transient on the order of a few nanoseconds. By employing incoherent neutron spectroscopy, we unambiguously determine the short-time self-diffusion of the protein clusters depending on cp, cs and T. We determine the cluster size in terms of effective hydrodynamic radii as manifested by the cluster center-of-mass diffusion coefficients D. For both salts, we find a simple functional form D(cp, cs, T) in the parameter range explored. The calculated inter-particle attraction strength, determined from the microscopic and short-time diffusive properties of the samples, increases with salt concentration and temperature in the regime investigated and can be linked to the macroscopic behavior of the samples.

Evidence of conformational landscape alteration and macromolecular complex formation in the early stages of in vitro human prion protein oxidation

Oxidative stress is proposed to be one of the major causes of neurodegenerative diseases. Cellular prion protein (PrP) oxidation has been widely studied using chemical reagents such as hydrogen peroxide. However, the experimental conditions used do not faithfully reflect the physiological environment of the cell. With the goal to explore the conformational landscape of PrP under oxidative stress, we conducted a set of experiments combining the careful control of the nature and the amount of ROS produced by a60Co γ-irradiation source. Characterization of the resulting protein species was achieved using a set of analytical techniques. Under our experimental condition hydroxyl radical are the main reactive species produced. The most important findings are i) the formation of molecular assemblies under oxidative stress, ii) the detection of a majority of unmodified monomer mixed with oxidized monomers in these molecular assemblies at low hydroxyl radical concentration, iii) the absence of significant oxidation on the monomer fraction after irradiation. Molecular assemblies are produced in small amounts and were shown to be an octamer. These results suggest either i) an active recruitment of intact monomers by molecular assemblies’ oxidized monomers then inducing a structural change of their intact counterparts or ii) an intrinsic capability of intact monomer conformers to spontaneously associate to form stable molecular assemblies when oxidized monomers are present. Finally, abundances of the intact monomer conformers after irradiation were modified. This suggests that monomers of the molecular assemblies exchange structural information with intact irradiated monomer. All these results shed a new light on structural exchange information between PrP monomers under oxidative stress.

Molecular basis for the distinct cellular functions of the Lsm1-7 and Lsm2-8 complexes.

Eukaryotes possess eight highly conserved Lsm (like Sm) proteins that assemble into circular, heteroheptameric complexes, bind RNA, and direct a diverse range of biological processes. Among the many essential functions of Lsm proteins, the cytoplasmic Lsm1–7 complex initiates mRNA decay, while the nuclear Lsm2–8 complex acts as a chaperone for U6 spliceosomal RNA. It has been unclear how these complexes perform their distinct functions while differing by only one out of seven subunits. Here, we elucidate the molecular basis for Lsm-RNA recognition and present four high-resolution structures of Lsm complexes bound to RNAs. The structures of Lsm2–8 bound to RNA identify the unique 2′,3′ cyclic phosphate end of U6 as a prime determinant of specificity. In contrast, the Lsm1–7 complex strongly discriminates against cyclic phosphates and tightly binds to oligouridylate tracts with terminal purines. Lsm5 uniquely recognizes purine bases, explaining its divergent sequence relative to other Lsm subunits. Lsm1–7 loads onto RNA from the 3′ end and removal of the Lsm1 carboxy-terminal region allows Lsm1–7 to scan along RNA, suggesting a gated mechanism for accessing internal binding sites. These data reveal the molecular basis for RNA binding by Lsm proteins, a fundamental step in the formation of molecular assemblies that are central to eukaryotic mRNA metabolism.

Luminescence and resonance energy transfer in the colloids of cyanine dyes and saponite modified with cationic surfactants

The luminescence and resonance energy transfer (RET) between two cyanine dyes, 3,3`-diethyl oxacyanine and 3,3`-diethyl thiacyanine, in organically-modified saponite colloids were investigated. It is known that the formation of molecular assemblies usually reduces the luminescence and photoactivity of organic dyes. Therefore, one of the objectives of this work was optimizing the properties of the colloids by using organic surfactants to prevent dye molecular aggregation. The organically-modified saponite colloids were prepared by an ion-exchange with n-alkyl(trimethyl)ammonium surfactants with alkyl chains having an even number of carbon atoms (from C6H13 to C18H37). The modification with the surfactants was adjusted to keep colloidal dispersions stable. Dye cations were added to the organically-modified saponite dispersions, and luminescence properties and the efficiency of RET were studied directly in these colloids using fluorescence spectroscopy. The properties of luminescent colloids were interpreted in terms of the structure of an organic phase present on the surface of saponite particles. The presence of the organophilic phase affecting dye aggregation in most cases led to the enhancement of luminescent properties and RET yields. The effect of the type of surfactant used for the modification on RET yields was observed. The formation of luminescent J-aggregates likely played a significant role.

Silver nanoparticle modulates the aggregation of beta-lactoglobulin and induces to form rod-like aggregates

Silver nanoparticles (SNPs) have been increasingly used in medicines and biomaterials as a drug carriers and diagnostic or therapeutic material due to their smaller size, large surface area and cell penetration ability. Here we report the preparation of SNPs of diameter 10 ± 3 nm by using silver nitrate and sodium borohydride and the interaction of synthesized SNPs with our model protein β-lactoglobulin (β-lg) in 10 mM phosphate buffer at pH 7.5 after thermal exposure at 75 °C. Heat exposed β-lg forms amyloidal fibrillar aggregates whereas this protein aggregates adopt rod-like shape instead of fibrillar structure in presence of SNP under the same conditions. Size of the synthesized SNPs is confirmed by UV–Visible spectroscopy, SEM and TEM. Interactions and subsequent formation of molecular assembly of heat stressed β-lg with SNP were investigated using Th-T assay and ANS binding assay, DLS, RLS, CD, FT-IR, SEM, TEM. Docking study parallely also support the experimental findings.

Exploring supramolecular aggregation behaviour of bioactive thiazolidine-4-carboxylic acid derivatives

A target synthesis of selected biocompatible chiral Thiazolidine-4-carboxylic acid derivatives was attempted to investigate the influence of number, type and position of hydrogen bonding functionalities and solvent molecules in the crystal lattice on the supramolecular aggregation behaviour leading to formation of molecular assemblies. The single crystal X-ray diffraction studies of (R)-thiazolidine-4-carboxylic acid (T4CA, zwitter ion form), 2-propionyl T4CA and (2S,4R)-3-(tert-butoxycarbonyl)-2-(4-methoxyphenyl)T4CA and other reported thiozolidine 4-carboxylic acid derivatives were used to establish the solid state aggregation behaviour. The 1D, 2D and 3D agregrational behaviour of synthesized thiozolidine-4-carboxylic acid derivatives was explored from their crystal packing diagrams and was further extended in light of some appropriate literature reported thiozolidine-4-carboxylic acid derivatives. The explored 1D, 2D and 3D supramolecular aggregrational behaviour in case of the thiazolidine-4-carboxylic acid derivatives can be explored for their further applications as biocompatible supramolecular assemblies towards gas storage, biosensing and template catalysis.

Photosensitive Electrified Water/Oil Interfaces Studied By Scanning Electrochemical Microscopy

The interface formed between two immiscible electrolytes solutions (ITIES) is a defect-free (down to the molecular level), self-healing, renewable and conductive substrate for the preferential and controlled formation of molecular assemblies and nano-objects.1 Similar to solid electrodes, modifier layer(s) can be formed and characterized by charge transfer processes across the interfaces. The potential drop across the interface can be controlled externally by using a potentiostat or chemically by dissolving a common salt in both phases. The polarization can be used to drive charged semiconductor nanoparticles to the interface. Polarization could also effectively drive the photo-induced charge transfer reaction by e- or h+ to control evolution of H2 with molecular photosensitizer2 and O2 semiconductor nanomaterials assembled at the ITIES.3 The jump in hydrophobicity at the soft interface supports the spatial separation of charge carriers on either side which partially restricts the recombination processes. Mechanistic studies of charge transfer in photoactivity of semiconductors at polarized ITIES are crucial for evaluation of such interfaces for fluidic systems with the ultimate goal of linking such interfaces to a z-scheme for water splitting. We probe the photo-induced electron transfer reaction at polarized soft interface by integrating it into scanning electrochemical microscope (SECM) as a tool to analyse the kinetics of the interfacial reaction at the nanostructured BiVO4|butyronitrile interphase under chemically controllable Galvani potential difference tuned by variation of ClO4 - concentration ration between the two liquid phases.4 This reaction occurs between electron in conduction band of BiVO4 and [Co(bpy)3]3+ in the organic electrolyte. SECM feedback approach curves are recorded based on the regeneration of the oxidized form of initial [Co(bpy)3]2+ by using the microelectrode (ME) in organic phase as probe. The current is enhanced under illumination with visible light (Scheme A). Furthermore, using substrate generation-tip/collection mode of SECM, O2 is probed as a main product of the photogenerated hole transfer in the aqueous phase under variable interfacial polarization (Scheme B). We also present a novel application of surface interrogation (SI) mode of SECM for in situ evaluate the surface of BiVO4 in photo-assisted water oxidation reaction (WOR). A micropipette (MP) filled with aqueous solution of dispersed nanostructured BiVO4, as a well-defined photosensitized substrate, is immersed into an immiscible organic solution containing perchlorate as common anion to generate the hydroxyl radicals (OH•) as intermediates of WOR under chemically controlled polarization. By the help of a ME as probe, surface concentrations of intermediates (Γ) and kinetics of their decay by bimolecular reactions (k) are analysed by recording the ME chronoamperograms transients enhanced by intermittent illumination of the substrate. Figure 1: Schematic of the SECM invetigation of photocatalysts asembled at liquid-liquid interfaces. A) Extraction of electons by SECM mediator, B) Detection of oxygen evolution, c) Surface interrogation of adobred intermediates. References L. Poltorak, A. Gamero-Quijano, G. Herzog, A. Walcarius, Appl Mater Today 2017, 9, 533-550. L. Rivier, P. Peljo, L.A.C. Vannay, H.H. Girault, Angew. Chem., Int. Ed. 2017, 56, 2324-2327.3. S. Rastgar, M. Pilarski, G. Wittstock, Commun. 2016, 52, 11382-11385.S. Rastgar, G. Wittstock, J. Phys. Chem. C 2017, 121, 25941-25948. Figure 1

Sorting of Molecular Building Blocks from Solution to Surface.

We demonstrate that molecular gradients on an organic monolayer is formed by preferential binding of ruthenium complexes from solutions also containing equimolar amounts of isostructural osmium complexes. The monolayer consists of a nanometer-thick assembly of 1,3,5-tris(4-pyridylethenyl)benzene (TPEB) covalently attached to a silicon or metal-oxide surface. The molecular gradient of ruthenium and osmium complexes is orthogonal to the surface plane. This gradient propagates throughout the molecular assembly with thicknesses over 30 nm. Using other monolayers consisting of closely related organic molecules or metal complexes results in the formation of molecular assemblies having an homogeneous and equimolar distribution of ruthenium and osmium complexes. Spectroscopic and computational studies revealed that the geometry of the complexes and the electronic properties of their ligands are nearly identical. These subtle differences cause the isostructural osmium and ruthenium complexes to pack differently on modified surfaces as also demonstrated in crystals grown from solution. The different packing behavior, combined with the organic monolayer significantly contributes to the observed differences in chemical composition on the surface.

PH-responsive molecular assemblies of pyridylbutadiene derivative with cucurbit[7]uril.

The interaction between red-emitting pyridinium derivative [4-((1E,3E)-4-(4-(dimethylamino)phenyl)buta-1,3-dien-1-yl)-1-methylpyridin-1-ium] (DABP) and cucurbit[7]uril was investigated using optical absorption, steady-state and time-resolved fluorescence and anisotropy measurements. The changes in the UV/Vis absorption, fluorescence spectral characteristics and lifetime, with a change in pH, reveal efficient binding of CB7 to the dye molecule. The cucurbit[7]uril encapsulated DABP brings ∼1.5 units upward pKa shift. The formation of supramolecular assemblies with 1 : 1 and 2 : 1 host–guest stoichiometries with CB7 at different pH conditions have been verified from 1H NMR, isothermal titration calorimetric studies and geometry optimization calculations. CB7-dye complexation and the ensuing morphological changes were revealed by SEM, AFM and optical microscopy images. This pH-responsive supramolecular assemblies of red-emitting DABP dye can find potential applications in biological imaging, optical pH-sensor and the construction of building blocks for the supramolecular architectures.

Model-independent counting of molecules in single-molecule localization microscopy.

Most biomolecular processes rely on tightly controlled stoichiometries, from the formation of molecular assemblies to cellular signaling. Single-molecule localization micro-scopy studies of fluorophore blinking offer a promising route to probe oligomeric states. Here we show that the distribution of the number of blinking events assumes a universal functional form, independent of photophysics, under relatively mild assumptions. The number of photophysical states, the kinetics of interconversion, and the fraction of active fluorophores enter as two or three constants. This essentially model-independent formulation allows us to determine molecule counts from fluorophore blinking statistics. The formulas hold even if the fluorophores have many different yet unresolved dark states, as long as there is only a single fluorescent state, or if there are different yet unresolvable fluorescent states, as long as there is only a single dark state. We demonstrate the practical applicability of this approach by quantifying the oligomerization states of membrane proteins tagged with the mEos2 fluorescent protein. We find that the model parameters, obtained by likelihood maximization, are transferable. With the counting statistics being independent of the detailed photophysics and its parameters being transferable, the method should be robust and broadly applicable to counting colocalized molecules in vivo and in vitro.

Regulating the Rate of Molecular Self‐Assembly for Targeting Cancer Cells

AbstractBesides tight and specific ligand–receptor interactions, the rate regulation of the formation of molecular assemblies is one of fundamental features of cells. But the latter receives little exploration for developing anticancer therapeutics. Here we show that a simple molecular design of the substrates of phosphatases—tailoring the number of phosphates on peptidic substrates—is able to regulate the rate of molecular self‐assembly of the enzyme reaction product. Such a rate regulation allows selective inhibition of osteosarcoma cells over hepatocytes, which promises to target cancer cells in a specific organ. Moreover, our result reveals that the direct measurement of the rate of the self‐assembly in a cell‐based assay provides precise assessment of the cell targeting capability of self‐assembly. This work, as the first report establishing rate regulation of a multiple‐step process to inhibit cells selectively, illustrates a fundamentally new approach for controlling the fate of cells.

Synthesis of Silica Nanotube Using Myelin Figure as Template and their Formation Mechanism.

Silica nanotubes are synthesized through a sol-gel reaction of tetraethyl orthosilicate (TEOS) using myelin figures of Pluronic P123 as the structure-directing agent. The simultaneous progression of the formation of molecular assemblies that act as templates and the formation of silica frameworks though a sol-gel reaction of the silica precursor is a characteristic of this reaction system. The synthesized silica nanotubes were characterized using transmission electron microscopy (TEM), nitrogen adsorption/desorption measurements, and Fourier-transform infrared spectroscopy (FT-IR). The silica nanotubes were unilamellar with diameters of approximately 30 nm, membrane thicknesses of approximately 10 nm, and lengths exceeding a few hundred nanometers. The Brunauer-Emmett-Teller (BET) specific surface area was 589.46 m(2)/g. Silica nanotubes can also be obtained using other Pluronic surfactants that can form myelin figures. In this work, we also investigated the formation mechanism of the silica nanotubes. The typical diameter of a myelin figure is a few tens of micrometers. However, myelin figures with diameters of approximately 10 µm can form in systems with TEOS because bifurcation is induced by minute silica nuclei that form during the initial reaction between TEOS and water. Freeze fracture TEM (FF-TEM) observations revealed the existence of myelin figures with diameters of 20 to 30 nm, which are the same size and shape as the synthesized silica nanotubes. These results indicate that bifurcation of the myelin figures is induced by the silica nuclei that form via the initial reaction of TEOS, which result in the formation of bifurcated myelin figures with diameters of ~10 µm. Myelin figures with diameters of 20 to 30 nm form on the surface, and they become templates where the reaction of TEOS progresses to form silica nanotubes with diameters of approximately 30 nm.

A Taco Complex Derived from a Bis-Crown Ether Capable of Executing Molecular Logic Operation through Reversible Complexation

As learned from natural systems, self-assembly and self-sorting help in interconnecting different molecular logic gates and thus achieve high-level logic functions. In this context, demonstration of important logic operations using changes in optical responses due to the formation of molecular assemblies is even more desirable for the construction of a molecular computer. Synthesis of an appropriate divalent as well as a luminescent crown ether based host 1 and paraquat derivatives, 2(PF(6))(2) and 3(PF(6))(2), as guests helped in demonstrating a reversible [3](taco complex) (1·{2(PF(6))(2)}(2) or 1·{3(PF(6))(2)}(2)) formation in nonpolar solvent. Detailed (1)H NMR studies revealed that two paraquat units were bound cooperatively by the two crown units in 1. Because of preorganization, the flexible host molecule 1 adopts a folded conformation, where each of two paraquat units remain sandwiched between the two aromatic units of each folded crown ether moiety in 1. Disassembly of the "taco" complex in the presence of KPF(6) and reassembly on subsequent addition of DB18C6 was initially demonstrated by (1)H NMR spectral studies, which were subsequently corroborated through luminescence spectral studies. Further, luminescence spectral responses as output signals with appropriate and two independent molecular inputs could be correlated to demonstrate basic logic operation like OR and YES gates, while the results of the three molecular inputs could be utilized to demonstrate important logic operation like an INHIBIT gate.

Photochemical Control of Molecular Assembly Formation in a Catanionic Surfactant System

Photochemical control of vesicle disintegration and reformation in aqueous solution was examined using a mixture of 4-butylazobenzene-4'-(oxyethyl)trimethylammonium bromide (AZTMA) as the photoresponsive cationic surfactant and sodium dodecylbenzenesulfonate (SDBS) as the anionic surfactant. Spontaneous vesicle formation was found in a wide-ranging composition of the trans-AZTMA/SDBS system. AZTMA molecules constituting vesicles underwent reversible trans-cis photoisomerization when irradiated with ultraviolet and visible light. Transmission electron microscopy observations using the freeze-fracture technique (FF-TEM) showed that UV light irradiation caused the vesicles to disintegrate into coarse aggregates and visible light irradiation stimulated the reformation of vesicles (normal control). A detailed investigation of the phase state and the effects of UV and visible light irradiation on the AZTMA/SDBS system with the use of electroconductivity, dynamic/static light scattering, and surface tension measurements and FF-TEM observations revealed that in the AZTMA-rich composition (AZTMA/SDBS 9:1) a micellar solution before light irradiation became a vesicular solution after UV light irradiation and visible light irradiation allowed the return to a micellar solution (reverse control). Thus, we could photochemically control the disintegration (normal control) and reformation (reverse control) of vesicles in the same system.

Rational design of peptide nanotubes for varying diameters and lengths

Amphiphilic helical peptides (Sar)(m) -b-(L-Leu-Aib)(n) (m = 22-25; n = 7, 8, 10) with a hydrophobic block as a right-handed helix were synthesized and their mixtures with (Sar)(25) -b-(D-Leu-Aib)(6) containing the hydrophobic block as a left-handed helix were examined in their molecular assembly formation. The single component (Sar)(25) -b-(D-Leu-Aib)(6) forms peptide nanotubes of 70 nm diameter and 200 nm length. The two-component mixtures of (Sar)(25) -b-(D-Leu-Aib)(6) with (Sar)(24) -b-(L-Leu-Aib)(7) , (Sar)(22) -b-(L-Leu-Aib)(8) , and (Sar)(25) -b-(L-Leu-Aib)(10) yield peptide nanotubes of varying dimensions with 200 nm diameter and 400 nm length, 70 nm diameter and several micrometer length (maximum 30 µm), and 70 nm diameter and 100-600 nm length, respectively. The right-handed and the left-handed helix were thus found to be molecularly mixed due to the stereo-complex formation and to generate nanotubes of different sizes. When the mismatch of the hydrophobic helical length between the two components was of four residues, the longest nanotube was generated. Correspondingly, the hydrophobic helical segments have to interdigitate with an anti-parallel orientation at the hydrophobic core region of the nanotube.