Temperature Control of the Self-Assembly Process of 4-Aminoquinoline Amphiphile: Selective Construction of Perforated Vesicles and Nanofibers, and Structural Restoration Capability.

The construction of diverse and distinctive self-assembled structures in water, based on the control of the self-assembly processes of artificial small molecules, has received considerable attention in supramolecular chemistry. Cage-like perforated vesicles are distinctive and interesting self-assembled structures. However, the development of self-assembling molecules that can easily form perforated vesicles remains challenging. This paper reports a lower critical solution temperature (LCST) behavior-triggered self-assembly property of a 4-aminoquinoline (4-AQ)-based amphiphile with a tetra(ethylene glycol) chain, in HEPES buffer (pH 7.4). This property allows to form perforated vesicles after heating at 80 °C (> LCST). The self-assembly process of the 4-AQ amphiphile can be controlled by heating at 80 °C (> LCST) or 60 °C (< LCST). After cooling to room temperature, the selective construction of the perforated vesicles and nanofibers was achieved from the same 4-AQ amphiphile. Furthermore, the perforated vesicles exhibited slow morphological transformation into intertwined-like nanofibers but were easily restored by brief heating above the LCST.

Delivery of external proteins into the cytoplasm using protein capsules modified with IgG on the surface, created from the amphiphilic two helix-bundle protein OLE-ZIP.

This study explores a new method for delivering therapeutic proteins into specific cells using OLE-ZIP capsules that present IgG. OLE-ZIP capsules is a spherical caspules prepared from amphihilic dimetic coiled-coil peptide, OLE-ZIP. Upon presenting cetuximab, these capsules showed preferential uptake in A431 cells and increased cytotoxicity when loaded with RNase A.

Control of the stepwise self-assembly process of a pH-responsive amphiphilic 4-aminoquinoline-tetraphenylethene conjugate.

Controlling the kinetic processes of self-assembly and switching their kinetic properties according to the changes in external environments are crucial concepts in the field of supramolecular polymers in water for biological and biomedical applications. Here we report a new self-assembling amphiphilic 4-aminoquinoline (4-AQ)-tetraphenylethene (TPE) conjugate that exhibits kinetically controllable stepwise self-assembly and has the ability of switching its kinetic nature in response to pH. The self-assembly process of the 4-AQ amphiphile comprises the formation of sphere-like nanoparticles, a transition to short nanofibers, and their growth to long nanofibers with ∼1 µm length scale at room temperature (RT). The timescale of the self-assembly process differs according to the pH-responsivity of the 4-AQ moiety in a weakly acidic to neutral pH range. Therefore, after aging for 24 h at RT, the 4-AQ amphiphile forms metastable short nanofibers at pH 5.5, while it forms thermodynamically favored long nanofibers at pH 7.4. Moreover, the modulation of nanofiber growth proceeding spontaneously at RT was achieved by switching the kinetic pathway through changing the pH between 7.4 and 5.5.

Effects of Structural Isomers of Spermine on the Higher-Order Structure of DNA and Gene Expression.

Polyamines are involved in various biological functions, including cell proliferation, differentiation, gene regulation, etc. Recently, it was found that polyamines exhibit biphasic effects on gene expression: promotion and inhibition at low and high concentrations, respectively. Here, we compared the effects of three naturally occurring tetravalent polyamines, spermine (SPM), thermospermine (TSPM), and N4-aminopropylspermidine (BSPD). Based on the single DNA observation with fluorescence microscopy together with measurements by atomic force microscopy revealed that these polyamines induce shrinkage and then compaction of DNA molecules, at low and high concentrations, respectively. We also performed the observation to evaluate the effects of these polyamine isomers on the activity of gene expression by adapting a cell-free luciferase assay. Interestingly, the potency of their effects on the DNA conformation and also on the inhibition of gene expression activity indicates the highest for TSPM among spermine isomers. A numerical evaluation of the strength of the interaction of these polyamines with negatively charged double-strand DNA revealed that this ordering of the potency corresponds to the order of the strength of the attractive interaction between phosphate groups of DNA and positively charged amino groups of the polyamines.

Structure-Based Identification of Potent Lysine-Specific Demethylase 1 Inhibitor Peptides and Temporary Cyclization to Enhance Proteolytic Stability and Cell Growth-Inhibitory Activity.

Peptides are attractive drug candidates, but their utility is greatly limited by their inherent susceptibility to proteolytic degradation and their inability to pass through the cell membrane. Here, we employ a strategy of temporary cyclization to develop a cell-active lysine-specific demethylase 1 (LSD1/KDM1A) inhibitor peptide. We first identified a highly potent LSD1-inhibitory linear peptide, with the assistance of X-ray crystal structure data of inhibitor peptide-bound LSD1·CoREST. The peptide was converted to a redox-activatable cyclic peptide incorporating cell-penetrating peptide (CPP), expecting selective activation under intracellular reducing conditions. The cyclic peptide moiety exhibited enhanced stability to protease and was converted to the linear, unmodified LSD1 inhibitor peptide under reducing conditions. The cyclic peptide with CPP inhibited the proliferation of human acute myeloid leukemia cells (HL-60) in the low micromolar concentration range.

Fluorescence Response and Self-Assembly of a Tweezer-Type Synthetic Receptor Triggered by Complexation with Heme and Its Catabolites.

There is increasing interest in the development and applications of synthetic receptors that recognize target biomolecules in aqueous media. We have developed a new tweezer-type synthetic receptor that gives a significant fluorescence response upon complexation with heme in aqueous solution at pH 7.4. The synthetic receptor consists of a tweezer-type heme recognition site and sulfo-Cy5 as a hydrophilic fluorophore. The receptor-heme complex exhibits a supramolecular amphiphilic character that facilitates the formation of self-assembled aggregates, and both the tweezer moiety and the sulfo-Cy5 moiety are important for this property. The synthetic receptor also exhibits significant fluorescence responses to biliverdin and bilirubin, but shows very weak fluorescence responses to flavin mononucleotide, folic acid, and nicotinamide adenine dinucleotide, which contain smaller π-scaffolds.

Development of Cell-Penetration PG-Surfactants and Its Application in External Peptide Delivery to Cytosol.

Recently, development of techniques to deliver pharmacologically active biomacromolecules such as peptides and proteins to cytosol has gained much interest. Here, we applied the peptide gemini (PG)-surfactants to a novel platform to design cell penetration lipopeptides (CP-PGs), which can deliver exogenous peptides and proteins to cytosol. Among the number of candidate CP-PGs having different peptide sequences at the X-, Y-, and Z-positions, we focused on those having two C12 alkyl chains appended to the side chain of two Cys residues, the betaine sequence -Asp-Lys-Asp-Lys- between the alkylated Cys residues (i.e., at the X-position), and having different cationic peptide sequences of oligo-Lys or oligo-Arg at the Y- and/or Z-positions. With respect to cytotoxicity for mammalian cells such as NIH3T3 cells upon 1 h exposure, those having (Lys)3 (K3-DKDKC12 and DKCK12-K3) showed lower cytotoxicity (IC50 = 241 and 198 µM) among those having oligo-Lys, (Lys)n (n = 1, 3, 5; IC50 = 88-197 µM). Similar lower cytotoxicity was also observed for the CP-PG having two (Lys)3 at both N- and C-terminal sides (K3-DKDKC12-K3) (IC50 = 225 µM). In contrast, the CP-PG having (Arg)3 at the N-terminal side (R3-DKDKC12) showed higher cytotoxicity (IC50 = 88 µM). Carrier abilities of the CP-PGs for exogenous peptides were evaluated using the proapoptotic domain (PAD) peptide, which induces apoptosis by disturbing mitochondrial membranes after delivery into cytosol. As a result, the CP-PGs of K3-DKDKC12, DKCK12-K3, K3-DKDKC12-K3, DKCK12-K5, and R3-DKDKC12 exhibited micromolar range carrier ability (the necessary half concentration to induce cell death (EC50) by delivering PAD peptide to cytosol was 10, 6.2, 8.5, 5.8, and 11.5 µM, respectively). Especially, the carrier abilities of DKCK12-K3 and DKCK12-K5 were superior to the well-established cell penetration Arg-rich R8 peptide (EC50 = 6.8 µM). Together, our results indicate that the PG-surfactant molecular framework could be a potential new platform to design efficient cell penetration carrier materials.

Specific effects of antitumor active norspermidine on the structure and function of DNA.

We compared the effects of trivalent polyamines, spermidine (SPD) and norspermidine (NSPD), a chemical homologue of SPD, on the structure of DNA and gene expression. The chemical structures of SPD and NSPD are different only with the number of methylene groups between amine groups, [N-3-N-4-N] and [N-3-N-3-N], respectively. SPD plays vital roles in cell function and survival, including in mammals. On the other hand, NSPD has antitumor activity and is found in some species of plants, bacteria and algae, but not in humans. We found that both polyamines exhibit biphasic effect; enhancement and inhibition on in vitro gene expression, where SPD shows definitely higher potency in enhancement but NSPD causes stronger inhibition. Based on the results of AFM (atomic force microscopy) observations together with single DNA measurements with fluorescence microscopy, it becomes clear that SPD tends to align DNA orientation, whereas NSPD induces shrinkage with a greater potency. The measurement of binding equilibrium by NMR indicates that NSPD shows 4-5 times higher affinity to DNA than SPD. Our theoretical study with Monte Carlo simulation provides the insights into the underlying mechanism of the specific effect of NSPD on DNA.

Methylene chain ruler for evaluating the regioselectivity of a substrate-recognising oxidation catalyst.

Regioselective C-H oxidation of aliphatic molecules with synthetic catalysts is challenging. We incorporated substrate-recognition sites into a ruthenium porphyrin-heteroaromatic N-oxide catalytic system in order to characterise its regioselectivity for the oxidation of alkanes. This substrate-recognition catalytic reaction exhibits high regioselectivity and high reaction efficiency.

Stable Iron Porphyrin Intramolecularly Coordinated by Alcoholate Anion: Synthesis and Evaluation of Axial Ligand Effect of Alcoholate on Spectroscopy and Catalytic Activity.

We synthesized intramolecularly aliphatic alcoholate-coordinated iron porphyrins (1a, 1b) that retain their axial coordination in the presence of another ligand or oxidant. The electron-donative character of alcoholate was less than that of thiolate, and the coordination ability of a sixth ligand to 1a and 1b was very much lower than in the case of the thiolate-coordinated compounds. Density functional theory calculations indicated that the marked difference in coordination ability could be explained in terms of thermodynamic and steric factors. The catalytic oxidizing ability of the thiolate-coordinated compound, SR complex, was much higher than that of 1a.

Effect of the o-Acetamido Group on pH-Dependent Light Emission of a 3-Hydroxyphenyl-Substituted Dioxetane Luminophore.

A pioneering chemiluminescent molecule reported by Schaap and co-workers, 3-(2'-spiroadamantane)-4-methoxy-4-(3″-hydroxy)phenyl-1,2-dioxetane (AMPD), does not require enzymatic activation but is unsuitable for use under physiological conditions. To overcome this limitation, we have developed a new AMPD derivative that contains an acetamido group at the ortho position of the hydroxy group as an intramolecular hydrogen-bonding site in order to lower the p Ka value. This compound exhibits a superior chemiluminescence response to AMPD in the physiologically relevant pH range.

Potent Antimalarial Activity of Two Arenes Linked with Triamine Designed To Have Multiple Interactions with Heme.

Based on the idea that compounds designed to exhibit high affinity for heme would block hemozoin formation, a critical heme-detoxification process for malarial parasites, we synthesized a series of compounds with two π-conjugated moieties at terminal amino groups of triamine. These compounds exhibited moderate to high antimalarial activities in vitro toward both chloroquine-sensitive and chloroquine-resistant Plasmodium falciparum. In a P. berghei-infected mouse model, 3a and 12a showed potent antimalarial activities compared to artesunate, as well as a prolonged duration of antimalarial effect. We found a good correlation between protective activity against hemin degradation and antimalarial activity. Compounds 8b and 3a strongly inhibited hemozoin formation catalyzed by heme detoxification protein.

Design and synthesis of a 4-aminoquinoline-based molecular tweezer that recognizes protoporphyrin IX and iron(iii) protoporphyrin IX and its application as a supramolecular photosensitizer.

We report on the design and synthesis of a new type of 4-aminoquinoline-based molecular tweezer 1 which forms a stable host-guest complex with protoporphyrin IX (PPIX) via multiple interactions in a DMSO and HEPES buffer (pH 7.4) mixed solvent system. The binding constant for the 1 : 1 complex (K 11) between 1 and PPIX is determined to be 4 × 106 M-1. Furthermore, 1 also forms a more stable complex with iron(iii) protoporphyrin IX (Fe(iii)PPIX), the K 11 value for which is one order of magnitude greater than that for PPIX, indicating that 1 could be used as a recognition unit of a synthetic heme sensor. On the other hand, the formation of the stable PPIX·1 complex (supramolecular photosensitizer) prompted us to apply it to photodynamic therapy (PDT). Cell staining experiments using the supramolecular photosensitizer and evaluations of its photocytotoxicity indicate that the PDT activity of PPIX is improved as the result of the formation of a complex with 1.

Distinct modulation of group I ribozyme activity among stereoisomers of a synthetic pentamine with structural constraints.

Among cationic molecules that can modulate ribozyme activities, polyamines act as both activator and inhibitor of ribozyme reactions partly due to their structural flexibility. Restriction of structural flexibility of polyamines may allow them to emphasize particular modulation effects. We examined eight stereoisomers of a synthetic pentamine bearing three cyclopentane rings. In the reaction of a structurally unstable group I ribozyme, three stereoisomers exhibited distinct effects as inhibitor, an additive with a neutral effect, and also as an activator.

A small-molecule inhibitor of SOD1-Derlin-1 interaction ameliorates pathology in an ALS mouse model.

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder. Despite its severity, there are no effective treatments because of the complexity of its pathogenesis. As one of the underlying mechanisms of Cu, Zn superoxide dismutase (SOD1) gene mutation-induced ALS, SOD1 mutants (SOD1mut) commonly interact with an endoplasmic reticulum-resident membrane protein Derlin-1, triggering motoneuron death. However, the importance of SOD1-Derlin-1 interaction in in vitro human model and in vivo mouse model remains to be elucidated. Here, we identify small-molecular-weight compounds that inhibit the SOD1-Derlin-1 interaction by screening approximately 160,000 compounds. The inhibitor prevents 122 types of SOD1mut from interacting with Derlin-1, and significantly ameliorates the ALS pathology both in motoneurons derived from patient induced pluripotent stem cells and in model mice. Our data suggest that the SOD1-Derlin-1 interaction contributes to the pathogenesis of ALS and is a promising drug target for ALS treatment.

Branched-Chain Polyamine Found in Hyperthermophiles Induces Unique Temperature-Dependent Structural Changes in Genome-Size DNA.

A pentavalent branched-chain polyamine, N4 -bis(aminopropyl)spermidine 3(3)(3)4, is a unique polycation found in the hyperthermophilic archaeon Thermococcus kodakarensis, which grows at temperatures between 60 and 100 °C. We studied the effects of this branched-chain polyamine on DNA structure at different temperatures up to 80 °C. Atomic force microscopic observation revealed that 3(3)(3)4 induces a mesh-like structure on a large DNA (166 kbp) at 24 °C. With an increase in temperature, DNA molecules tend to unwind, and multiple nano-loops with a diameter of 10-50 nm are generated along the DNA strand at 80 °C. These results were compared to those obtained with linear-chain polyamines, homocaldopentamine 3334 and spermidine, the former of which is a structural isomer of 3(3)(3)4. These specific effects are expected to neatly concern with its role on high-temperature preference in hyperthermophiles.

Comparative study of polyethylene polyamines as activator molecules for a structurally unstable group I ribozyme.

Polyamines are a promising class of molecules that can modulate RNA enzyme activities. To analyze the effects of the number of amine moieties systematically, we employed four polyamines sharing dimethylene units to connect amine moieties. As a model RNA enzyme, we used a structurally unstable group I ribozyme, which was activated most and least efficiently by tetraethylenepentamine and diethylenetriamine respectively.

Biogenic triamine and tetraamine activate core catalytic ability of Tetrahymena group I ribozyme in the absence of its large activator module.

Group I intron ribozymes share common core elements that form a three-dimensional structure responsible for their catalytic activity. This core structure is unstable without assistance from additional factors that stabilize its tertiary structure. We examined biogenic triamine and tetraamine and also their fragments for their abilities to stabilize a structurally unstable group I ribozyme, ΔP5 ribozyme, derived from the Tetrahymena group I intron ribozyme by deleting its large activator module. Biogenic triamine (spermidine) and tetraamine (spermine) efficiently activated the ΔP5 ribozyme under conditions where the ribozyme was virtually inactive. These observations suggested that polyamines are promising small molecule modulators to activate and possibly inhibit the core catalytic ability of group I ribozymes.

Inhibition of FAD-dependent lysine-specific demethylases by chiral polyamine analogues.

Lysine-specific demethylases 1 and 2 (LSD1 and LSD2) are flavoenzyme demethylases, and their inhibitors are considered as potential chemical tools and anticancer agents. Here we report polyamine-based inhibitors of LSD1 and LSD2. In the initial screening, partially constrained polyamine 2 which contains three trans-cyclopentane units with a total of six stereogenic centers, showed the most potent LSD1-inhibitory activity. We then prepared a set of optical isomers of 2 and evaluated their inhibitory activities toward LSD1, LSD2, monoamine oxidases A and B (MAO-A and MAO-B). Optical isomers of 2 showed LSD1-inhibitory activity with K i values of 2.2 to 6.4 µM, and LSD2-inhibitory activity with K i values of 4.4 to 39 µM; there was a general preference for LSD1 to LSD2. All of them showed weak to negligible inhibition of MAO-A and MAO-B. This selectivity seemed to reflect the differences in the size and shape of the catalytic cavity of target enzymes, and our strategy of employing a set of optical isomers appears to be an effective approach for exploring the structural features of this family of enzymes. Polyamine 9 showed most potent LSD1-inhibitory activity (K i = 2.2 µM in vitro), and it also inhibited the proliferation of HL-60 cells (IC50 = 49 µM). On the other hand, 12 was the most potent inhibitors of LSD2 with in vitro K i values of 4.4 µM.