Development of the efficient preparation method for thermoresponsive elastin-like peptides using liquid-phase synthesis combined with fragment condensation strategy

Elastin-like peptides (ELPs) are synthetic peptides that mimic the characteristic hydrophobic amino acid repeat sequences of elastin and exhibit temperature-dependent reversible self-assembly properties. ELPs are expected to be used as temperature-responsive biomolecular materials across diverse industrial and research fields, and there is a requirement for a straightforward method to mass-produce them. Previously, we demonstrated that phenylalanine-containing ELP analogs, namely, (FPGVG)n , can undergo coacervation with short chains (n = 5). The Fmoc solid-phase peptide synthesis method is one strategy used to synthesize these short ELPs. However, owing to its low reaction efficiency, an efficient method for preparing ELPs is required. In this study, efficient preparation of ELPs was investigated using a liquid-phase synthesis method with a hydrophobic benzyl alcohol support (HBA-tag). Because HBA-tags are highly hydrophobic, they can be easily precipitated by the addition of poor solvents and recovered by filtration. This property allows the method to combine the advantages of the simplicity of solid-phase methods and the high reaction efficiency of liquid-phase methods. By utilizing liquid-phase fragment condensation with HBA-tags, short ELPs were successfully obtained in high yield and purity. Finally, the temperature-dependent response of the ELPs generated through fragment condensation was assessed using turbidity measurements, which revealed a reversible phase transition. Consequently, the ELPs exhibited a reversible phase transition, indicating successful synthesis of ELPs via fragment preparation with tags. These findings provide evidence of the potential for mass production of ELPs using this approach.

Enhancement of Aggregate Formation Through Aromatic Compound Adsorption in Elastin-like Peptide (FPGVG)5 Analogs

Elastin-like peptides (ELPs) exhibit temperature-dependent reversible self-assembly. Repetitive sequences derived from elastin, such as Val-Pro-Gly-Val-Gly (VPGVG), are essential for the self-assembly of ELPs. Previously, we developed (FPGVG)5 (F5), in which the first valine residue in the VPGVG sequence was replaced with phenylalanine, which showed strong self-aggregation ability. This suggests that interactions through the aromatic amino acid residues of ELPs could play an important role in self-assembly. In this study, we investigated the thermoresponsive behavior of F5 analogs in the presence of aromatic compounds. Turbidimetry, spectroscopy, and fluorescence measurements demonstrated that aromatic compounds interacted with F5 analogs below the transition temperature and enhanced the self-assembly ability of ELPs by stabilizing amyloid-like structures. Furthermore, quantitative high-performance liquid chromatography analyses showed that the F5 analogs could adsorb and remove hydrophobic aromatic compounds from aqueous solutions during aggregate formation. These results suggested that the F5 analogs can be applicable as scavengers of aromatic compounds.

Determining the Sequence Dependency of Self-Assembly of Elastin-Like Peptides Using Short Peptide Analogues with Shuffled Repetitive Sequences

Synthetic elastin-like peptides (ELPs) that possess characteristic tropoelastin-derived hydrophobic repetitive sequences, such as (VPGVG)n, exhibit thermoresponsive reversible self-assembly. Although their thermoresponsive properties have been well-studied, the sequence-dependent and structural requirements for self-assembly remain ambiguous. In particular, it is still unclear whether the amino acid sequences derived from tropoelastin are necessary for self-assembly. In this study, 11 sequence-shuffled ELP analogues based on (FPGVG)5, which is a previously developed short ELP (sELP), were designed to elucidate the sequence-dependent and structural requirements for their self-assembly. Among them, eight shuffled peptides exhibited self-assembling properties, whereas the other three peptides were difficult to dissolve in water. Structural analyses revealed that the structural characteristics of the three insoluble peptides were different from those of their thermoresponsive analogues. Furthermore, the secondary structures of the peptide analogues possessing the self-assembly abilities were different from each other. These results suggest that the potential for self-assembly and water solubility of sELPs depend on the primary structure in each repeated unit. Moreover, several shuffled analogues exhibited more potent self-assembling properties than the original (FPGVG)5, indicating that shorter ELPs can be obtained using their novel motifs as repetitive units. We also observed that the presence of Pro-Gly sequence in the repeating units was advantageous in terms of peptide solubility. Although further analysis will be necessary to elucidate the molecular mechanism underlying the self-assembly of these sELPs, this study provides insights into the relationship between the amino acid sequence and the self-assembling ability of the peptides for developing new sELPs for various applications.

Branched short elastin-like peptides with temperature responsiveness obtained by EDTA-mediated multimerization

Elastin-like peptides (ELPs) exhibit a reversible phase transition, known as coacervation, triggered by temperature changes. This property makes them useful as stimuli-responsive molecular materials for various applications. Among ELPs, short peptide chain lengths have some advantages over long peptide chain lengths because short ELPs can be easily obtained by chemical synthesis, allowing the use of various amino acids, including D-type and unnatural amino acids, at any position in the sequence. Moreover, the incorporated amino acids readily affect the temperature-responsive behavior of ELPs. However, to be utilized in various applications, it is necessary to develop short ELPs and to investigate their temperature-responsive properties. To obtain further insights into the temperature-responsive behavior of the short ELPs, we investigated branched short ELP analogs composed of (FPGVG)_n chains (n = 1 or 2, abbreviated as F1 and F2, respectively). We synthesized multimers composed of four F1 chains or two to four F2 chains using ethylenediaminetetraacetic acid (EDTA) as a central component of multimerization. Our results show that the multimers obtained exhibited coacervation in aqueous solutions whereas linear F1 or F2 did not. Furthermore, the structural features of the obtained multimers were the same as those of linear (FPGVG)₄ . In this study, we demonstrated that molecules capable of coacervation can be obtained by multimerization of F1 or F2. The temperature-responsive molecules obtained using short ELPs make it possible to use them as easy-to-synthesize peptide tags to confer temperature responsiveness to various molecules, which will aid the development of temperature-responsive biomaterials with a wide variety of functions.

Ugi Adducts as Novel Anti-austerity Agents against PANC-1 Human Pancreatic Cancer Cell Line: A Rapid Synthetic Approach

Pancreatic cancer cells have an inherent tolerance to withstand nutrition starvation, allowing them to survive in hypovascular tumor microenvironments that lack of sufficient nutrients and oxygen. Developing anti-cancer agents that target this tolerance to nutritional starvation is a promising anti-austerity strategy for eradicating pancreatic cancer cells in their microenvironment. In this study, we employed a chemical biology approach using the Ugi reaction to rapidly synthesize new anti-austerity agents and evaluate their structure-activity relationships. Out of seventeen Ugi adducts tested, Ugi adduct 11 exhibited the strongest anti-austerity activity, showing preferential cytotoxicity against PANC-1 pancreatic cancer cells with a PC50 value of 0.5 µM. Further biological investigation of Ugi adduct 11 revealed a dramatic alteration of cellular morphology, leading to PANC-1 cell death within 24 h under nutrient-deprived conditions. Furthermore, the R absolute configuration of 11 was found to significantly contribute to the preferential anti-austerity ability toward PANC-1, with a PC50 value of 0.2 µM. Mechanistically, Ugi adduct (R)-11 was found to inhibit the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway preferentially under nutrition starvation conditions. Consequently, Ugi-adduct (R)-11 could be a promising candidate for drug development targeting pancreatic cancer based on the anti-austerity strategy. Our study also demonstrated that the Ugi reaction-based chemical engineering of natural product extracts can be used as a rapid method for discovering novel anti-austerity agents for combating pancreatic cancer.

Flexible customization of the self-assembling abilities of short elastin-like peptide Fn analogs by substituting N-terminal amino acids

Elastin-like peptides (ELPs) are thermoresponsive biopolymers inspired by the characteristic repetitive sequences of natural elastin. As ELPs exhibit temperature-dependent reversible self-assembly, they are expected to be biocompatible thermoresponsive materials for drug delivery carriers. One of the most widely studied ELPs in this field is the repetitive pentapeptide, (VPGXG)_n . We previously reported that phenylalanine-containing ELP (Fn) analogs, in which the former Val residue of the repetitive sequence (VPGVG)_n is replaced by Phe, show coacervation with a short chain length (n = 5). Owing to their short sequences, Fn analogs are easily modified in amino acid sequences via simple chemical synthesis, and are useful for investigating the relationship between peptide sequences and temperature responsiveness. In this study, we developed Fn analogs by replacing Phe residue(s) with other amino acids or introducing another amino acid at the N-terminus. The temperature responsiveness of the Fn analogs changed drastically with the substitution of a single Phe residue, suggesting that aromatic amino acids play an important role in their self-assembly. In addition, the self-assembling ability of Fn was enhanced by increasing the bulkiness of the N-terminal amino acids. Therefore, the N-terminal residue was considered to be important for hydrophobicity-induced intermolecular interactions between the peptides during coacervation.

Metal ion scavenging activity of elastin-like peptide analogues containing a cadmium ion binding sequence

The development of simple and safe methods for recovering environmental pollutants, such as heavy metals, is needed for sustainable environmental management. Short elastin-like peptide (ELP) analogues conjugated with metal chelating agents are considered to be useful as metal sequestering agents as they are readily produced, environment friendly, and the metal binding domain can be selected based on any target metal of interest. Due to the temperature dependent self-assembly of ELP, the peptide-based sequestering agents can be transformed from the solution state into the particles that chelate metal ions, which can then be collected as precipitates. In this study, we developed a peptide-based sequestering agent, AADAAC-(FPGVG)₄, by introducing the metal-binding sequence AADAAC on the N-terminus of a short ELP, (FPGVG)₄. In turbidity measurements, AADAAC-(FPGVG)₄ revealed strong self-assembling ability in the presence of metal ions such as Cd²⁺ and Zn²⁺. The results from colorimetric analysis indicated that AADAAC-(FPGVG)₄ could capture Cd²⁺ and Zn²⁺. Furthermore, AADAAC-(FPGVG)₄ that bound to metal ions could be readily recycled by treatment with acidic solution without compromising its metal binding affinity. The present study indicates that the fusion of the metal-binding sequence and ELP is a useful and powerful strategy to develop cost-effective heavy metal scavenging agents with low environmental impacts.

Direct evidence of edge-to-face CH/π interaction for PAR-1 thrombin receptor activation

Heptapeptide SFLLRNP is a receptor-tethered ligand of protease-activated receptor 1 (PAR-1), and its Phe at position 2 is essential for the aggregation of human platelets. To validate the structural elements of the Phe-phenyl group in receptor activation, we have synthesized a complete set of S/Phe/LLRNP peptides comprising different series of fluorophenylalanine isomers (F_n)Phe, where n = 1, 2, 3, and 5. Phe-2-phenyl was strongly suggested to be involved in the edge-to-face CH/π interaction with the receptor aromatic group. In the present study, to prove this receptor interaction definitively, we synthesized another series of peptide analogs containing (F₄)Phe-isomers, with the phenyl group of each isomer possessing only one hydrogen atom at the ortho, meta, or para position. When the peptides were assayed for their platelet aggregation activity, S/(2,3,4,6-F₄)Phe/LLRNP and S/(2,3,4,5-F₄)Phe/LLRNP exhibited noticeable activity (34% and 6% intensities of the native peptide, respectively), whereas S/(2,3,5,6-F₄)Phe/LLRNP was completely inactive. The results indicated that, at the ortho and meta positions but not at the para position, benzene-hydrogen atoms are required for the CH/π interaction to activate the receptor. The results provided a decisive evidence of the molecular recognition property of Phe, the phenyl benzene-hydrogen atom of which participates directly in the interaction with the receptor aromatic π plane.

Bisphenol A derivatives act as novel coactivator-binding inhibitors for estrogen receptor β

Bisphenol A and its derivatives are recognized as endocrine disruptors based on their complex effects on estrogen receptor (ER) signaling. While the effects of bisphenol derivatives on ERα have been thoroughly evaluated, how these chemicals affect ERβ signaling is less well understood. Herein, we sought to identify novel ERβ ligands using a radioligand competitive binding assay to screen a chemical library of bisphenol derivatives. Many of the compounds identified showed intriguing dual activities as both ERα agonists and ERβ antagonists. Docking simulations of these compounds and ERβ suggested that they bound not only to the canonical binding site of ERβ but also to the coactivator binding site located on the surface of the receptor, suggesting that they act as coactivator-binding inhibitors (CBIs). Receptor-ligand binding experiments using WT and mutated ERβ support the presence of a second ligand-interaction position at the coactivator-binding site in ERβ, and direct binding experiments of ERβ and a coactivator peptide confirmed that these compounds act as CBIs. Our study is the first to propose that bisphenol derivatives act as CBIs, presenting critical insight for the future development of ER signaling-based drugs and their potential to function as endocrine disruptors.

Simple Regulation of the Self-Assembling Ability by Multimerization of Elastin-Derived Peptide (FPGVG) n Using Nitrilotriacetic Acid as a Building Block

Elastin comprises hydrophobic repetitive sequences, such as Val-Pro-Gly-Val-Gly, which are thought to be important for the temperature-dependent reversible self-association (coacervation). Elastin and elastin-like peptides (ELPs), owing to their characteristics, are expected to be applied as base materials for the development of new molecular tools, such as drug-delivery system carrier and metal-scavenging agents. Recently, several studies have been reported on the dendritic or branching ELP analogues. Although the topological difference of the branched ELPs compared to their linear counterparts may lead to useful properties in biomaterials, the available information regarding the effect of branching on molecular architecture and thermoresponsive behavior of ELPs is scarce. To obtain further insight into the thermoresponsive behavior of branched ELPs, novel ELPs, such as nitrilotriacetic acid (NTA)-(FPGVG) _n conjugates, that is, (NTA)-Fn analogues possessing 1-3 (FPGVG) _n (n = 3, 5) molecule(s), were synthesized and investigated for their coacervation ability. Turbidity measurement of the synthesized peptide analogues revealed that (NTA)-Fn analogues showed strong coacervation ability with various strengths. The transition temperature of NTA-Fn analogues exponentially decreased with increasing number of residues. In the circular dichroism measurements, trimerization did not alter the secondary structure of each peptide chain of the NTA-Fn analogue. In addition, it was also revealed that the NTA-Fn analogue possesses one peptide chain that could be utilized as metal-scavenging agents. The study findings indicated that multimerization of short ELPs via NTA is a useful and powerful strategy to obtain thermoresponsive molecules.

Bisphenol-C is the strongest bifunctional ERα-agonist and ERβ-antagonist due to magnified halogen bonding

We reported that bisphenol AF (BPAF) works as an agonist for estrogen receptor (ER) ERα but as an antagonist for ERβ. Similar results were observed for bisphenol E analogs (BPE-X) such as BPE-F, BPE-Cl, and BPE-Br, each consisting of a series of a tri-halogenated methyl group CX3 in the central alkyl moiety. It was demonstrated that the electrostatic halogen bond based on the dispersion force of halogen atoms is a major driving force in the activities of bifunctional ERα-agonist and ERβ-antagonist. Since the chlorine atoms present in bisphenol C (BPC) exist in a π-π conjugated system due to the presence of an adjacent C = C double bond, we intended to prove that BPC is also a bifunctional ERα-agonist and ERβ-antagonist exhibiting greatly enhanced agonist/antagonist activities. BPC was evaluated for its ability to activate ERα and ERβ in the luciferase reporter gene assay using HeLa cells. With high receptor-binding ability to both ERs, BPC was found to be fully active for ERα but inactive for ERβ. BPC's definite antagonist activity in ERβ was revealed by its inhibitory activity against 17β-estradiol. Thus, BPC is a bifunctional ERα-agonist and ERβ-antagonist. These agonist/antagonist activities were discovered to be extremely high among series of halogen-containing bisphenol compounds. This comparative structure-activity study revealed that the ascending order of ERα-agonist and ERβ-antagonist activities was BPE-F ≪ BPE-Cl ≲ BPAF < BPE-Br ≪ BPC. The highly intensified receptor interaction of BPC is attributable to the presence of an n-π-π-n conjugation system mediated through the >C = CCl2 double bond.

Mechanistic Insights into a DMSO-Perturbing Inhibitory Assay of Hyaluronidase

A hyaluronic acid-degrading enzyme (hyaluronidase; HAase) is involved in tumor growth and inflammation, and consequently, HAase inhibitors have received recent attention as potential pharmaceuticals. Previous studies have discovered a wide range of inhibitors; however, unfortunately, most of them are dissimilar to the original ligand hyaluronic acid, and their mode of inhibition remains ambiguous or seems promiscuous. This situation presents an urgent need for readily available and highly reliable assay systems identifying the promiscuous inhibitory properties of HAase inhibitors. We have previously proposed a unique method to identify promiscuous nonspecific binding inhibitors of HAase by using the DMSO-perturbing effect. Here, to obtain mechanistic insights into the DMSO-perturbing assay, we studied the addition effect of 11 water-compatible chemicals on HAase inhibitory assay. Intriguingly, the perturbing property was found to be highly specific to DMSO. Furthermore, kinetic analyses described characteristic description of the perturbing property of DMSO: DMSO displayed entropy-driven interactions with HAase, whereas nonperturbing agents such as ethanol and urea exhibited enthalpy-driven interactions. The enthalpy-driven tight interactions of ethanol and urea with HAase would lead to the irreversible denaturation of the enzymes, while the entropy-driven weak interactions caused structural and catalytic perturbation, generating nonproductive but nondenatured states of enzymes, that are key species of the perturbation assay. With these mechanistic understandings in hand, the present assay will enable rapid and reliable identification of HAase inhibitors with certain pharmaceutical potential.

Evaluation of the Influence of Halogenation on the Binding of Bisphenol A to the Estrogen-Related Receptor γ

Halogenation of organic compounds is one the most important transformations in chemical synthesis and is used for the production of various industrial products. A variety of halogenated bisphenol analogs have recently been developed and are used as alternatives to bisphenol A (BPA), which is a raw material of polycarbonate that has adverse effects in animals. However, limited information is available on the potential toxicity of the halogenated BPA analogs. In the present study, to assess the latent toxicity of halogenated BPA analogs, we evaluated the binding and transcriptional activities of halogenated BPA analogs to the estrogen-related receptor γ (ERRγ), a nuclear receptor that contributes to the growth of nerves and sexual glands. Fluorinated BPA analogs demonstrated strong ERRγ binding potency, and inverse antagonistic activity, similar to BPA. X-ray crystallography and fragment molecular orbital (FMO) calculation revealed that a fluorine-substituted BPA analog could interact with several amino acid residues of ERRγ-LBD, strengthening the binding affinity of the analogs. The ERRγ binding affinity and transcriptional activity of the halogenated BPAs decreased with the increase in the size and number of halogen atom(s). The IC₅₀ values, determined by the competitive binding assay, correlated well with the binding energy obtained from the docking calculation, suggesting that the docking calculation could correctly estimate the ERRγ binding potency of the BPA analogs. These results confirmed that ERRγ has a ligand binding pocket that fits very well to BPA. Furthermore, this study showed that the binding affinity of the BPA analogs can be predicted by the docking calculation, indicating the importance of the calculation method in the risk assessment of halogenated compounds.

Bisphenol AF: Halogen bonding effect is a major driving force for the dual ERα-agonist and ERβ-antagonist activities

17β-Estradiol (E2) is a natural steroid ligand for the structurally and physiologically independent estrogen receptors (ERs) ERα and ERβ. We recently observed that CF₃-containing bisphenol AF (BPAF) works as an agonist for ERα but as an antagonist for ERβ. Similar results were also observed for the CCl₃-containing bisphenol designated as HPTE. Both BPAF and HPTE are comprised of a tri-halogenated methyl group in the central alkyl moiety of their bisphenol structures, which strongly suggests that halogens contribute directly to the agonist/antagonist dual biological functions. We conducted this study to investigate the structure-activity relationships by assessing together newly synthesized CF₃- and CBr₃-containing bisphenol E analogs (BPE-X). We first tested bisphenols for their receptor binding ability and then for their transcriptional activities. Halogen-containing bisphenols were found to be fully active for ERα, but almost completely inactive for ERβ. When we examined these bisphenols for their inhibitory activities for E2 in ERβ, we observed that they worked as distinct antagonists. The ascending order of agonist/antagonist dual biological functions was BPE-F < BPE-Cl (HPTE) ≤ BPAF < BPE-Br, demonstrating that the electrostatic halogen bonding effect is a major driving force of the bifunctional ERα agonist and ERβ antagonist activities of BPAF.

Early identification of promiscuous attributes of aldose reductase inhibitors using a DMSO-perturbation assay

Aldose reductase (AR) inhibitors are used clinically to treat long-term diabetic complications. Previous studies reported a series of AR inhibitory candidates, but unfortunately the mode of inhibition was poorly described due mainly to the lack of readily available methods for evaluating the specificity. The present study examined the AR inhibitory effects of novel synthetic hydantoins and their structural relatives, some of which were obtained from chemically engineered extracts of natural plants, and discovered several novel AR inhibitors with moderate inhibitory activity. The identified inhibitors were then subjected to a two-step mechanistic characterization using a detergent-addition assay and our novel dimethyl sulfoxide (DMSO)-perturbation assay. The detergent-addition assay revealed aggregation-based inhibitors, and the subsequent DMSO-perturbation assay identified nonspecific binding inhibitors. Thus, the present study demonstrates the usefulness of the DMSO-perturbation screen for identifying nonspecific binding characteristics of AR inhibitors.

DMSO-Perturbing Assay for Identifying Promiscuous Enzyme Inhibitors

In search for enzyme inhibitors, we often encounter "promiscuous" enzyme inhibitors exhibiting nonspecific binding property toward enzyme active site. Therefore, inhibitory candidates should be mechanistically characterized as early as possible in discovery processes. However, there remains a lack of highly reliable and readily available methodology to evaluate specificity of initial hits inhibitors. The present study developed and established a novel DMSO-perturbing assay to identify promiscuous enzyme inhibitors. The assay successfully identified nonspecific binding inhibitors with a broad scope, typically by the attenuation of inhibitory activity by the influence of DMSO-addition. This attenuation would be attributed to the nonspecific binding property of inhibitors toward both productive and nonproductive (nondenatured) states of enzymes in perturbation solution. This working hypothesis was supported by spectroscopic analyses of enzyme conformations and analyses of solvent effects on perturbation. Overall, these results provided a novel concept of the DMSO-perturbing assay.

Receptor-binding affinities of bisphenol A and its next-generation analogs for human nuclear receptors

An endocrine-disrupting chemical Bisphenol A (BPA) binds specifically to a nuclear receptor (NR) named ERRγ. Although the importance of receptor-binding evaluation for human NRs is often stressed, the binding characteristics of so-called next-generation (NextGen) bisphenol compounds are still poorly understood. The ultimate objective of this investigation was to evaluate BPA and its NextGen analogs for their abilities to bind to 21 human NRs, the greatest members of NRs for which tritium-labeled specific ligands were available. After establishing the detailed assay conditions for each NR, the receptor binding affinities of total 11 bisphenols were evaluated in competitive binding assays. The results clearly revealed that BPA and the NextGen bisphenols of BPAF, BPAP, BPB, BPC, BPE, and BPZ were highly potent against one or more of NRs such as CAR, ERα, ERβ, ERRγ, and GR, with IC₅₀ values of 3.3-73 nM. These bisphenols were suggested strongly to be disruptive to these NRs. BPM and BPP also appeared to be disruptive, but less potently. BPF exhibited only weak effects and only against estrogen-related NRs. Surprisingly, most doubtful bisphenol BPS was supposed not to be disruptive. The NRs to which BPA and NextGen bisphenols did not bind were RARα, RARβ, RARγ, and VDR. PPARγ, RORα, RORβ, RORγ, RXRα, RXRβ, and RXRγ, exhibited very weak interaction with these bisphenols. The ten remaining NRs, namely, ERRγ, ERβ, ERα, CAR, GR, PXR, PR, AR, LXRβ, and LXRα, showed distinctly strong binding to some bisphenols in this order, being likely to have consequential endocrine-disruption effects.

Enhancement of Self-Aggregation Properties of Linear Elastin-Derived Short Peptides by Simple Cyclization: Strong Self-Aggregation Properties of Cyclo[FPGVG] n, Consisting Only of Natural Amino Acids

Elastin-like peptides (ELPs) consist of distinctive repetitive sequences, such as (VPGVG) _n, exhibit temperature-dependent reversible self-assembly (coacervation), and have been considered to be useful for the development of thermoresponsive materials. Further fundamental studies evaluating coacervative properties of novel nonlinear ELPs could present design concepts for new thermoresponsive materials. In this study, we prepared novel ELPs, cyclic (FPGVG) _n (cyclo[FPGVG] _n, n = 1-5), and analyzed their self-assembly properties and structural characteristics. Cyclo[FPGVG] _n ( n = 3-5) demonstrated stronger coacervation capacity than the corresponding linear peptides. The coacervate of cyclo[FPGVG]₅ was able to retain water-soluble dye molecules at 40 °C, which implied that cyclo[FPGVG]₅ could be employed as a base material of DDS (drug delivery system) matrices and other biomaterials. The results of molecular dynamics simulations and circular dichroism measurements suggested that a certain chain length was required for cyclo[FPGVG] _n to demonstrate alterations in molecular structure that were critical to the exhibition of coacervation.

Stepwise Mechanism of Temperature-Dependent Coacervation of the Elastin-like Peptide Analogue Dimer, (C(WPGVG)3)2

Elastin-like peptides (ELPs) are distinct, repetitive, hydrophobic sequences, such as (VPGVG) _n, that exhibit coacervation, the property of reversible, temperature-dependent self-association and dissociation. ELPs can be found in elastin and have been developed as new scaffold biomaterials. However, the detailed relationship between their amino acid sequences and coacervation properties remains obscure because of the structural flexibility of ELPs. In this study, we synthesized a novel, dimeric ELP analogue (H-C(WPGVG)₃-NH₂)₂, henceforth abbreviated (CW3)2, and analyzed its self-assembly properties and structural factors as indicators of coacervation. Turbidity measurements showed that (CW3)2 demonstrated coacervation at a concentration much lower than that of its monomeric form and another ELP. In addition, the coacervate held water-soluble dye molecules. Thus, potent and distinct coacervation was obtained with a remarkably short sequence of (CW3)2. Furthermore, fluorescence microscopy, dynamic light scattering, and optical microscopy revealed that the coacervation of (CW3)2 was a stepwise process. The structural factors of (CW3)2 were analyzed by molecular dynamics simulations and circular dichroism spectroscopy. These measurements indicated that helical structures primarily consisting of proline and glycine became more disordered at high temperatures with concurrent, significant exposure of their hydrophobic surfaces. This extreme change in the hydrophobic surface contributes to the potent coacervation observed for (CW3)2. These results provide important insights into more efficient applications of ELPs and their analogues, as well as the coacervation mechanisms of ELP and elastin.

Investigation of water-soluble elastin as a multifunctional cosmetic material: Moisturizing and whitening effects

Elastin and collagen are extracellular matrix proteins that are widely distributed in the body. Although elastin essentially functions as a skin moisturizer, there have been few reports on its other fundamental chemical and biological functions. In this study, we investigated the moisturizing and whitening (tyrosinase inhibition) effects of elastin to examine its usefulness as a cosmetic material. Water-soluble hot alkali pig aorta (HAPA)-elastin was prepared from pig aorta using the hot alkali method. HAPA-elastin showed a widely distributed molecular weight and had a coacervation property that mediated reversible self-assembly of its molecules with increasing temperature. Amino acid analysis of HAPA-elastin showed a high content (81.5%) of hydrophobic amino acids such as Gly, Ala, Val, and Pro. Des (desmosine) and Ide (isodesmosine), which are characteristic amino acids of elastin, accounted for more than 0.4% of the total amino acid content. HAPA-elastin showed a moisture-retaining property. The water content of skin samples treated with and without HAPA-elastin was 77.2% ± 7.8% and 49.4% ± 10.1%, respectively. HAPA-elastin also inhibited tyrosinase activity by 11.3% ± 3.9%. The results obtained indicate that elastin has a useful function as a cosmetic material.

Dimerization effects on coacervation property of an elastin-derived synthetic peptide (FPGVG)5

Elastin, a core protein of the elastic fibers, exhibits the coacervation (temperature-dependent reversible association/dissociation) under physiological conditions. Because of this characteristic, elastin and elastin-derived peptides have been considered to be useful as base materials for developing various biomedical products, skin substitutes, synthetic vascular grafts, and drug delivery systems. Although elastin-derived polypeptide (Val-Pro-Gly-Val-Gly)n also has been known to demonstrate coacervation property, a sufficiently high (VPGVG)n repetition number (n>40) is required for coacervation. In the present study, a series of elastin-derived peptide (Phe-Pro-Gly-Val-Gly)5 dimers possessing high coacervation potential were newly developed. These novel dimeric peptides exhibited coacervation at significantly lower concentrations and temperatures than the commonly used elastin-derived peptide analogs; this result suggests that the coacervation ability of the peptides is enhanced by dimerization. Circular dichroism (CD) measurements indicate that the dimers undergo similar temperature-dependent and reversible conformational changes when coacervation occurs. The molecular dynamics calculation results reveal that the sheet-turn-sheet motif involving a type II β-turn-like structure commonly observed among the dimers and caused formation of globular conformation of them. These synthesized peptide dimers may be useful not only as model peptides for structural analysis of elastin and elastin-derived peptides, but also as base materials for developing various temperature-sensitive biomedical and industrial products.

Role of individual disulfide bridges in the conformation and activity of spinoxin (α-KTx6.13), a potassium channel toxin from Heterometrus spinifer scorpion venom

Spinoxin (SPX; α-KTx6.13), isolated from venom of the scorpion Heterometrus spinifer, is a K⁺ channel-specific peptide toxin (KTx), which adopts a cysteine-stabilized α/β scaffold that is cross-linked by four disulfide bridges (Cys1-Cys5, Cys2-Cys6, Cys3-Cys7, and Cys4-Cys8). To investigate the role of the individual disulfide bonds in the structure-activity relationship of SPX, we synthesized four SPX analogs in which each pair of cysteine residues was replaced by alanine residues. The analysis of circular dichroism spectra and inhibitory activity against Kv1.3 channels showed that the SPX analogs lacking any of three specific disulfide bonds (Cys1-Cys5, Cys2-Cys6, and Cys3-Cys7) were unable to form the native secondary structure and completely lost inhibitory activities. Thus, we conclude that Cys1-Cys5, Cys2-Cys6, and Cys3-Cys7 are required for the inhibition of the Kv1.3 channel by SPX. In contrast, the analog lacking Cys4-Cys8 retained both native secondary structure and inhibitory activity. Interestingly, one of the isomers of the analog lacking Cys1-Cys5 also showed inhibitory activities, although its inhibition was ∼18-fold weaker than native SPX. This isomer had an atypical disulfide bond pairing (Cys3-Cys4 and Cys7-Cys8) that corresponds to that of maurotoxin (MTX), another α-KTx6 family member. These results indicate that the Cys1-Cys5 and Cys2-Cys6 bonds are important for restricting the toxin from forming an atypical (MTX-type) disulfide bond pairing among the remaining four cysteine residues (Cys3, Cys4, Cys7, and Cys8) in native SPX.

Design of Phenylalanine-Containing Elastin-Derived Peptides Exhibiting Highly Potent Self-Assembling Capability

In this study, we developed a series of Phe-containing elastin-derived peptide-analogs, (Phe-Pro-Gly-Val-Gly)n (n = 1-5) and analyzed their reversible coacervation properties. Compared to the native elastin-derived repeating peptide sequence ((Val-Pro-Gly-Val-Gly)10), one of the Phecontaining 5-mer repeating peptide sequences ((Phe-Pro-Gly-Val-Gly)5) clearly exhibited stronger coacervation properties. The coacervation of (Phe-Pro-Gly-Val-Gly)5 is nearly the same as that of polypeptides (Val-Pro-Gly-Val-Gly)n (n > 40). Although large molecular weights (>10,000 Da) are generally required for the coacervation of elastin-derived peptides, (Phe-Pro-Gly-Val-Gly)5 exhibited reversible coacervation properties despite its low molecular weight (MW = 2,305 Da). High performance liquid chromatography (HPLC) and circular dichroism (CD) analysis revealed that (Phe-Pro-Gly-Val-Gly)5 has high hydrophobicity and an ordered structure with a type II β-turn, which contributes to the strong coacervation ability of the peptide. In addition, (Phe-Pro-Gly-Val-Gly)5 exhibited an effective particle size distribution (60-70 nm) at body temperature (37°C) and a dispersed small particle size similar to that of the monomer peptides at low temperatures. These properties, along with its small size and simple design, render the peptide suitable for use in biomaterials, including drug-delivery carriers.

Active Sites of Spinoxin, a Potassium Channel Scorpion Toxin, Elucidated by Systematic Alanine Scanning

Peptide toxins from scorpion venoms constitute the largest group of toxins that target the voltage-gated potassium channel (Kv). Spinoxin (SPX) isolated from the venom of scorpion Heterometrus spinifer is a 34-residue peptide neurotoxin cross-linked by four disulfide bridges. SPX is a potent inhibitor of Kv1.3 potassium channels (IC50 = 63 nM), which are considered to be valid molecular targets in the diagnostics and therapy of various autoimmune disorders and cancers. Here we synthesized 25 analogues of SPX and analyzed the role of each amino acid in SPX using alanine scanning to study its structure-function relationships. All synthetic analogues showed similar disulfide bond pairings and secondary structures as native SPX. Alanine replacements at Lys(23), Asn(26), and Lys(30) resulted in loss of activity against Kv1.3 potassium channels, whereas replacements at Arg(7), Met(14), Lys(27), and Tyr(32) also largely reduced inhibitory activity. These results suggest that the side chains of these amino acids in SPX play an important role in its interaction with Kv1.3 channels. In particular, Lys(23) appears to be a key residue that underpins Kv1.3 channel inhibition. Of these seven amino acid residues, four are basic amino acids, suggesting that the positive electrostatic potential on the surface of SPX is likely required for high affinity interaction with Kv1.3 channels. This study provides insight into the structure-function relationships of SPX with implications for the rational design of new lead compounds targeting potassium channels with high potency.

Development of short and highly potent self-assembling elastin-derived pentapeptide repeats containing aromatic amino acid residues

Tropoelastin is the primary component of elastin, which forms the elastic fibers that make up connective tissues. The hydrophobic domains of tropoelastin are thought to mediate the self-assembly of elastin into fibers, and the temperature-mediated self-assembly (coacervation) of one such repetitive peptide sequence (VPGVG) has been utilized in various bio-applications. To elucidate a mechanism for coacervation activity enhancement and to develop more potent coacervatable elastin-derived peptides, we synthesized two series of peptide analogs containing an aromatic amino acid, Trp or Tyr, in addition to Phe-containing analogs and tested their functional characteristics. Thus, position 1 of the hydrophobic pentapeptide repeat of elastin (X(1)P(2)G(3)V(4)G(5)) was substituted by Trp or Tyr. Eventually, we acquired a novel, short Trp-containing elastin-derived peptide analog (WPGVG)3 with potent coacervation ability. From the results obtained during this process, we determined the importance of aromaticity and hydrophobicity for the coacervation potency of elastin-derived peptide analogs. Generally, however, the production of long-chain synthetic polypeptides in quantities sufficient for commercial use remain cost-prohibitive. Therefore, the identification of (WPGVG)3, which is a 15-mer short peptide consisting simply of five natural amino acids and shows temperature-dependent self-assembly activity, might serve as a foundation for the development of various kinds of biomaterials.

Comparison between coacervation property and secondary structure of synthetic peptides, Ile-containing elastin-derived pentapeptide repeats

A series of Ile-containing elastin-derived peptide-analogs, (Ile-Pro-Gly-Val-Gly)n (n = 7-10) possessing remarkable and reversible coacervation property were newly synthesized. In comparison with the known elastin-derived peptide-analogs, which were so-called polypeptides, the obtained 35 to 50 mer peptides, (IPGVG)n (n = 7-10) were significantly low molecular sized-polypeptides. However, they clearly exhibited coacervation property as same as the polypeptides did. Because of their low molecular size, spectrographic analyses of (IPGVG)n (n = 7-10) became feasible to carry out. As results of secondary structural analyses by CD and FT-IR, it was found that the coacervation property of the peptides is clearly attributed to the ordered secondary-structures, mainly, type II β-turn.

Highly potent binding and inverse agonist activity of bisphenol A derivatives for retinoid-related orphan nuclear receptor RORγ

The plastic chemical bisphenol A (BPA) has recently been suspected to be a base structure of endocrine disrupting chemicals, which achieve their adverse effects by interfering with human nuclear receptors. For instance, BPA, bisphenol AF, and tetrabromo- or tetrachloro-BPA (X₄-BPA) have been characterized as binders for ERRγ, ER, and PPARγ, respectively. This ongoing string of findings has led to apprehension that some other BPA derivatives might also perturb important human nuclear receptors. The retinoid-related orphan receptor RORγ has been strongly suspected to be a target of highly hydrophobic chemical substances because of its extreme affinity for lipophilic sterols. In the present study, we tested a series of BPA derivatives for their ability to bind to RORγ, and identified two distinctly potent derivatives having isopropyl or sec-butyl groups at positions adjacent to the BPA-4-hydroxyl group. In particular, di-sec-butyl-BPA has emerged as a considerably potent ligand (IC₅₀)=146 nM). In the reporter gene assay, these compounds suppressed the basal constitutive transcriptional activity originally induced by wild-type RORγ. The present results strongly suggested that RORγ, and perhaps also RORα and RORβ, binds highly hydrophobic and sterically hindered chemical substances, inducing some unspecified physiological and biochemical disruptions.

Localization of gelatinase activities in glioma tissues by film in situ zymography

Malignant gliomas are characterized by their invasiveness and angiogenesis, which are mediated by metalloproteinases (MMPs). In this study, localization of gelatinase activities in six cases of glioblastoma, two cases of anaplastic astrocytoma, and six cases of low-grade astrocytomas was investigated by film in situ zymography (FIZ). FIZ is a novel technique, because it allows preservation of tissue structure with gelatinolytic activity and can detect net MMP activity in tumor tissues. In malignant gliomas, gelatinolytic activities were extensively localized in the vessel walls in the viable tumor areas and peritumoral areas as well as the tumor cell itself. These findings suggest that FIZ is a useful tool not only to detect tumor net MMP activities but also to detect angiogenic features in the invading front of malignant gliomas.

Fine spatial assembly for construction of the phenol-binding pocket to capture bisphenol A in the human nuclear receptor estrogen-related receptor γ

Various lines of evidence have shown that bisphenol A (BPA) acts as an endocrine disruptor that affects various hormones even at merely physiological levels. We demonstrated recently that BPA binds strongly to human nuclear receptor estrogen-related receptor γ (ERRγ), one of 48 nuclear receptors. Based on X-ray crystal analysis of the ERRγ ligand-binding domain (LBD)/BPA complex, we demonstrated that ERRγ receptor residues, Glu275 and Arg316, function as the intrinsic-binding site of the phenol-hydroxyl group of BPA. If these phenol-hydroxyl↔Glu275 and Arg316 hydrogen bonds anchor the A-benzene ring of BPA, the benzene-phenyl group of BPA would be in a pocket constructed by specific amino acid side chain structures. In the present study, by evaluating the Ala-replaced mutant receptors, we identified such a ligand-binding pocket. Leu268, Leu271, Leu309 and Tyr326, in addition to the previously reported participants Glu275 and Arg316, were found to make a receptacle pocket for the A-ring, whereas Ile279, Ile310 and Val313 were found to assist or structurally support these residues. The results revealed that each amino acid residue is an essential structural element for the strong binding of BPA to ERRγ.

Recycled addition of CD4+ T cell-rich population for induction of human autologous cytotoxic T lymphocytes: A practically efficient method

When CD4(+) T cell-rich population appears in theinitial trial in induction cultures of humanautologous cytotoxic T lymphocytes (CTL), the cultureresults frequently in no or weak killing activity andtherefore usually be discarded as an ;unsuccessful'CTL induction culture. However, addition of theinitial CD4(+) T cell-rich population enabledefficient induction of the autologous CTL in theensuing trials. The CTL thus generated exhibitedstronger killing activities against autologous braintumor cells and ovarian tumor cells than previouslyobserved. This simple recycling of the primed butinert CD4(+) T cell-rich population for CTLinduction will promote clinical practice of adoptiveimmunotherapy of human tumors with autologous CTL.

Spare interactions of highly potent [Arg(14),Lys(15)]nociceptin for cooperative induction of ORL1 receptor activation

[Arg(14),Lys(15)]Nociceptin is a very potent for ORL1 receptor, showing a few times stronger binding activity and much more enhanced biological activity than endogenous nociceptin. This synergistic outcome has been suggested to be due to the interaction with the receptor aromatic and/or acidic amino acid residues crucial to receptor activation. In order to identify such receptor residues in the second ORL1 extracellular loop, we prepared a series of recombinant mutant receptors. The mutant receptor Gln205Ala was found to be as active as wild-type ORL1 for both nociceptin and [Arg(14),Lys(15)]nociceptin. In contrast, Asp206Ala and Tyr207Ala exhibited considerably reduced activity for [Arg(14),Lys(15)]nociceptin, exhibiting no synergistic activity enhancement. These results suggest that Asp206 and Tyr207 are directly involved in the interaction with nociceptin-[Arg(14),Lys(15)]. Trp208Ala was found to bind strongly both nociceptin and [Arg(14),Lys(15)]nociceptin, although it elicited no biological activity. All these results indicate that the consecutive amino acid residues Asp206, Tyr207, and Trp208 are critical to the activation of the ORL1 receptor, but not to nociceptin-binding.

Discriminatory synergistic effect of Trp-substitutions in superagonist [(Arg/Lys)(14), (Arg/Lys)(15)]nociceptin on ORL1 receptor binding and activation

ORL1 is an endogenous G protein-coupled receptor for neuropeptide nociceptin. [(R/K)(14), (R/K)(15)]nociceptin is a superagonist that strongly activates the ORL1 receptor. We have previously found that substituting with Trp can reproduce the potentiation induced by Arg or Lys at position 14. In the present study, in order to ensure the effect of Trp-substitution on the activities of [(R/K)(14), (R/K)(15)]nociceptin, we synthesized [W(14), (R/K)(15)]nociceptin and [(R/K)(14), W(15)]nociceptin. [W(14), (R/K)(15)]nociceptin was found to exhibit threefold higher binding activity and 10-fold greater potency in a functional [(35)S]GTPgammaS functional assay as compared to wild-type nociceptin. However, when only Trp was placed in position 15, the resulting analogues, [(R/K)(14), W(15)]nociceptin, showed only a moderate enhancement of binding and biological activity (2-3 fold in both). These results indicate that the placement of Trp at position 14, unlike at position 15, enhances in a synergistic fashion the interaction of nociceptin with the ORL1 receptor. The results indicate that specific interactions feasible for Arg/Lys and Trp in common must be there for aromatic residues in ORL1, thus forming a cation/pi interaction or pi/pi hydrophobic interaction. The necessity for a favorable electrostatic interaction appears strict in position 15.

Radar chart deviation analysis of prion protein amino acid composition defines characteristic structural abnormalities of the N-terminal octa-peptide tandem repeat

Analysis of the amino acid composition of prion protein using a newly developed program for radar-chart deviation analysis has identified an abnormality or irregularity of the N-terminal flexible domain. Aromatic amino acids Trp and His together with Gly are abnormally abounding in this N-terminal domain, in which octapeptide GQPHGGGW is connected four times in tandem. This tetrarepeat structure has been suggested to be essential for the prion protein not only to play an intrinsic functional role in the physiological condition, but also to bring on structural abnormalities in prion disease.

Synergistic effect of basic residues at positions 14-15 of nociceptin on binding affinity and receptor activation

Nociceptin is an endogenous ligand that activates a G protein-coupled receptor ORL1 and contains two indispensable Arg-Lys (RK) dipeptide units at positions 8-9 and 12-13. By replacing an additional RK unit at positions 6-7, 10-11, 14-15, or 16-17, of the peptide we have identified the analog, [RK(14-15)]nociceptin as a superagonist. In fact, this peptide exhibits 3-fold higher binding affinity and 17-fold greater potency in a functional GTPgammaS-binding assay compared to wild-type nociceptin. Here, we have further investigated the role of basic residues in position 14-15. The replacement of three other possible basic dipeptides, KR, RR, and KK, into nociceptin at positions 14-15 resulted in similar enhancements of binding affinity (3-5-fold) and biological potency (10-12-fold in the GTPgammaS assay). However, when only a single basic residue (Arg or Lys) was replaced in either position 14 or 15, all the resulting analogs showed moderate enhancements of binding and biological activity (2-4-fold in both). These results indicate that the addition of basic charges in positions 14 and 15 enhance in a synergistic fashion the interaction of nociceptin with the receptor and only the simultaneous presence of two adjacent basic residues yields an optimal effect. This suggests that specific electrostatic interactions between both amino acids present in 14-15 and corresponding residues in the receptor are responsible for the enhancement of nociceptin activity.

A docking modelling rationally predicts strong binding of bisphenol A to estrogen-related receptor gamma

A computer-aided docking study was carried out to quickly clarify the binding structure of the ligand-receptor complex between bisphenol A (BPA), a well-known endocrine disruptor, and estrogen-related receptor gamma (ERRgamma). The resulting complex indicated that BPA binds to the ligand-binding pocket of ERRgamma without any disruptions of the activation conformation.

Retreatment of cerebral aneurysms after guglielmi detachable coil embolization

SUMMARY

Of 175 patients with 181 aneurysms initially treated with Guglielmi Detachable Coils (GDC), 25 were retreated. All retreatments except one were performed on previously ruptured aneurysms. Thirteen aneurysms were retreated because of recurrence, and 12 aneurysms were retreated to complete initial insufficient embolization. Sixteen patients underwent re-embolization and 9 patients were operated upon surgically. No complications related to the retreatment were experienced. We consider that repeat embolization should be attempted before considering surgical treatment in case that additional therapy is required. However, it is difficult to retreat aneurysms having wide necks. In regard to surgical clipping, aneurysms without a coil in the neck are easier to treat with primary clipping, whereas aneurysms with a coil mass in the neck are difficult to surgical clip. We have never used temporary clipping and coil extraction if the distance between the coil and the parent artery was wider than 2 mm. Emerging new embolic agents or devices and technical improvement might decrease the need for retreatment and increase long-term efficacy after endovascular treatment.

Normal pressure hydrocephalus after gamma knife radiosurgery for cerebellopontine angle meningioma

There are no reports of hydrocephalus following radiosurgery for a meningioma. We report on a case where gamma knife therapy for a 4 cm diameter right cerebellopontine meningioma accelerated hydrocephalus three months post treatment. Examination of the cerebrospinal fluid (CSF) revealed a high protein level and thus, CSF malabsorption and CSF obstruction might have occurred after the radio surgery. It is important to consider this pathology, and the need for long term follow up.

Kernohan's phenomenon associated with left ruptured occipital arteriovenous malformation

A 23-year-old woman presented with ipsilateral hemiparesia due to rupture of a left occipital arteriovenous malformation (AVM). Emergency decompression (the onset-operation interval was 46 minutes,) was carried out and the patient could leave the hospital upon recovery without neurological deficits. In general, Kernohan's phenomenon is caused by the gradual displacement of the cerebral peduncle against the tentorial edge caused by compression by the contralateral mass. This phenomenon is very rare among the cases with spontaneous intracranial hemorrhage and only three cases including the present one have been reported in the literature. In all cases the onset-operation intervals of were very short. Kernohan's phenomenon associated with a ruptured AVM is a rare condition and emergency decompression is required.

Cervical spondylosis with thoracic level Brown-Séquard syndrome

Brown-Sequard Syndrome (BSS) caused by cervical spondylosis (CS) is rare. About 70% of patients with CS presenting with BSS show lesion-dermatome discrepancy, which may be due to spinal cord lamination. From the clinical point of view, this discrepancy should be carefully evaluated and these patients should be treated as an emergency.

Pitch perception abnormality as a side effect of carbamazepine

Carbamazepine (CBZ) is frequently used to treat patients with epilepsy, neuralgia, psychiatric diseases, etc. We prescribe it with care due to its side effects, mainly such as dizziness, sleepiness and cerebellar symptoms. But pitch perception abnormality is an uncommon side effect. We describe the case of a 12-year-old girl who exhibited half tone lowered pitch perception abnormality caused by CBZ. As CBZ acts as a central nervous system (CNS) inhibitor, we speculate that CBZ inhibits CNS and patients misperceive notes. We must prescribe CBZ with care to prevent pitch perception abnormalities.

Designed modification of partial agonist of ORL1 nociceptin receptor for conversion into highly potent antagonist

Nociceptin is an endogenous agonist ligand of the ORL1 (opioid receptor-like 1) receptor, and its antagonist is a potential target of therapeutics for analgesic and antineuropathy drugs. Ac-RYYRIK-NH(2) is a hexapeptide isolated from the peptide library as an antagonist that inhibits the nociceptin activities mediated through ORL1. However, the structural elements required for this antagonist activity are still indeterminate. In the present study, we evaluated the importance of the acetyl-methyl group in receptor binding and activation, examining the peptides acyl-RYYRIK-NH(2), where acyl (R-CO) possesses a series of alkyl groups, R=C(n)H(2n+1) (n=0-5). The isovaleryl derivative with the C(4)H(9) (=(CH(3))(2)CHCH(2)-) group was found to reveal a high receptor-binding affinity and a strong antagonist nature. This peptide achieved a primary goal of eliminating the agonist activity of Ac-RYYRIK-NH(2) and producing pure antagonist activity.

Differential receptor binding characteristics of consecutive phenylalanines in micro-opioid specific peptide ligand endomorphin-2

Endogenous opioid peptides consist of a conserved amino acid residue of Phe(3) and Phe(4), although their binding modes for opioid receptors have not been elucidated in detail. Endomorphin-2, which is highly selective and specific for the mu opioid receptor, possesses two Phe residues at the consecutive positions 3 and 4. In order to clarify the role of Phe(3) and Phe(4) in binding to the mu receptor, we synthesized a series of analogs in which Phe(3) and Phe(4) were replaced by various amino acids. It was found that the aromaticity of the Phe-beta-phenyl groups of Phe(3) and Phe(4) is a principal determinant of how strongly it binds to the receptor, although better molecular hydrophobicity reinforces the activity. The receptor binding subsites of Phe(3) and Phe(4) of endomorphin-2 were found to exhibit different structural requirements. The results suggest that [Trp(3)]endomorphin-2 (native endomorphin-1) and endomorphin-2 bind to different receptor subclasses.

The relationships of proteinuria, serum creatinine, glomerular filtration rate with cardiovascular disease mortality in Japanese general population

Proteinuria, high serum creatinine, and reduced glomerular filtration rate (GFR) have been associated with increased mortality from cardiovascular disease (CVD) and all causes. However, the combined effect of proteinuria with serum creatinine and GFR on CVD or all-cause mortality has not been well investigated. We conducted a 10-year prospective cohort study of 30,764 men and 60,668 women aged 40-79 years who participated in annual health checkups in 1993. The Cox proportional hazards model was used to estimate the relative risk (RR) after adjusting for age, smoking, and other cardiovascular risk factors. The multivariable RR (95% confidence interval (CI)) of CVD death for positive vs negative proteinuria was 1.38 (1.05-1.79) among men and 2.15 (1.64-2.81) among women. The respective RR for the highest vs lowest creatinine groups (> or = 1.3 vs < or = 0.8 mg/dl for men and > or = 1.1 vs < or = 0.6 mg/dl for women) was 1.56 (1.19-2.04) among men and 2.15 (1.58-2.93) among women. The respective RR for GFR < 60 vs > r = 100 ml/min/1.73 m2 was 1.65 (1.25-2.18) among men and 1.81 (1.39-2.36) among women. For individuals with proteinuria combined by hypercreatininemia or reduced GFR, the risk of CVD death was two-fold higher in men and 4-6-fold higher in women compared to those without proteinuria and with normal creatinine level or GFR. Similar associations were observed for stroke, coronary heart disease, and all-cause mortality. Proteinuria, and hypercreatininemia or reduced GFR and their combination were significant predictors of CVD and all-cause mortality.