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1.
J Org Chem ; 89(11): 7541-7551, 2024 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-38725112

RESUMO

Cationic, anionic, and nonionic cyclophane dimers, 1a, 1b, and 1c, covalently linked with fluorescent perylene diimide were synthesized, respectively, as a host for aggregation-induced multivalent effects on guest-binding. These PDI-linked cyclophane dimers 1a and 1b, especially 1c, formed self-aggregates in H2O-rich solvents through π-stacking interactions. Critical aggregation concentrations of 1a, 1b, and 1c in H2O were 4.0 × 10-6, 4.0 × 10-6, and less than 0.1 × 10-6 M, respectively. The self-aggregates of the PDI-linked cyclophane dimers in H2O were several hundred nanometers in size by DLS and TEM measurements. In an aggregated state, 1a exhibited guest-binding abilities toward hydrophobic guests, such as 6-p-toluidinonaphthalene-2-sulfonate and 6-anilino-naphthalene-2-sulfonate. Moreover, anion-induced agglutination of 1a was observed upon the addition of phosphate ions, and its effectiveness was as follows: ATP > ADP > H2P2O72- > AMP ≈ PO43- > HPO42- > H2PO4-. The contribution of the adenine base of the nucleotides as a guest moiety used for effective agglutination was confirmed by 1H NMR spectroscopy.

2.
J Biol Chem ; 298(8): 102109, 2022 08.
Artigo em Inglês | MEDLINE | ID: mdl-35679897

RESUMO

Collagenase from the gram-negative bacterium Grimontia hollisae strain 1706B (Ghcol) degrades collagen more efficiently even than clostridial collagenase, the most widely used industrial collagenase. However, the structural determinants facilitating this efficiency are unclear. Here, we report the crystal structures of ligand-free and Gly-Pro-hydroxyproline (Hyp)-complexed Ghcol at 2.2 and 2.4 Å resolution, respectively. These structures revealed that the activator and peptidase domains in Ghcol form a saddle-shaped structure with one zinc ion and four calcium ions. In addition, the activator domain comprises two homologous subdomains, whereas zinc-bound water was observed in the ligand-free Ghcol. In the ligand-complexed Ghcol, we found two Gly-Pro-Hyp molecules, each bind at the active site and at two surfaces on the duplicate subdomains of the activator domain facing the active site, and the nucleophilic water is replaced by the carboxyl oxygen of Hyp at the P1 position. Furthermore, all Gly-Pro-Hyp molecules bound to Ghcol have almost the same conformation as Pro-Pro-Gly motif in model collagen (Pro-Pro-Gly)10, suggesting these three sites contribute to the unwinding of the collagen triple helix. A comparison of activities revealed that Ghcol exhibits broader substrate specificity than clostridial collagenase at the P2 and P2' positions, which may be attributed to the larger space available for substrate binding at the S2 and S2' sites in Ghcol. Analysis of variants of three active-site Tyr residues revealed that mutation of Tyr564 affected catalysis, whereas mutation of Tyr476 or Tyr555 affected substrate recognition. These results provide insights into the substrate specificity and mechanism of G. hollisae collagenase.


Assuntos
Proteínas de Bactérias , Colágeno , Colagenases , Vibrionaceae , Proteínas de Bactérias/química , Colágeno/química , Colagenases/química , Hidroxiprolina/química , Especificidade por Substrato , Vibrionaceae/enzimologia , Água/química , Zinco/química
3.
Molecules ; 26(11)2021 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-34067275

RESUMO

A water-soluble cyclophane dimer having two disulfide groups as a reduction-responsive cleavable bond as well as several acidic and basic functional groups as a pH-responsive ionizable group 1 was successfully synthesized. It was found that 1 showed pH-dependent guest-binding behavior. That is, 1 strongly bound an anionic guest, 6-p-toluidinonaphthalene-2-sulfonate (TNS) with binding constant (K/M-1) for 1:1 host-guest complexes of 9.6 × 104 M-1 at pH 3.8, which was larger than those at pH 7.4 and 10.7 (6.0 × 104 and 2.4 × 104 M-1, respectively), indicating a favorable electrostatic interaction between anionic guest and net cationic 1. What is more, release of the entrapped guest molecules by 1 was easily controlled by pH stimulus. Large favorable enthalpies (ΔH) for formation of host-guest complexes were obtained under the pH conditions employed, suggesting that electrostatic interaction between anionic TNS and 1 was the most important driving force for host-guest complexation. Such contributions of ΔH for formation of host-guest complexes decreased along with increased pH values from acidic to basic solutions. Upon addition of dithiothreitol (DTT) as a reducing reagent to an aqueous PBS buffer (pH 7.4) containing 1 and TNS, the fluorescence intensity originating from the bound guest molecules decreased gradually. A treatment of 1 with DTT gave 2, having less guest-binding affinity by the cleavage of disulfide bonds of 1. Consequently, almost all entrapped guest molecules by 1 were released from the host. Moreover, such reduction-responsive cleavage of 1 and release of bound guest molecules was performed more rapidly in aqueous buffer at pH 10.7.

4.
J Org Chem ; 85(8): 5493-5502, 2020 04 17.
Artigo em Inglês | MEDLINE | ID: mdl-32233372

RESUMO

Water-soluble cationic and anionic cyclophanes (1a and 2a, respectively) having a dabsyl group with a cleavable disulfide linkage were synthesized as a host-guest conjugate covalently bound with both host and guest components. Self-inclusion phenomena but not self-aggregation behaviors were observed for each cyclophane in aqueous media. Each cyclophane includes its own dabsyl moiety (guest component) in its macrocyclic cavity (host component) through hydrophobic interaction. When 1 equiv. of cationic 1a was added to an aqueous solution of anionic 2a, however, supramolecular coaggregates formed spontaneously through host-guest complexation. As regard the supramolecular coaggregates, the existence of larger particles was confirmed by DLS measurements and TEM observation. The hydrophobic interaction between the dabsyl moiety and macrocyclic cavity and electrostatic interactions between 1a and 2a play important roles in the supramolecular coaggregate formation. Each cyclophane having a cleavable disulfide linkage was easily transformed to the corresponding thiols by reducing reagents such as DTT, which was confirmed by MALDI-TOF MS. Disaggregation of the supramolecular coaggregates composed of 1a and 2a was successfully performed upon addition of DTT, with release of the thiol derivative of dabsyl. Such disaggregation of the coaggregates was also conducted by other external stimuli such as salts and competitive guests.

5.
Sci Rep ; 10(1): 3927, 2020 03 03.
Artigo em Inglês | MEDLINE | ID: mdl-32127566

RESUMO

Collagenase products are crucial to isolate primary cells in basic research and clinical therapies, where their stability in collagenolytic activity is required. However, currently standard collagenase products from Clostridium histolyticum lack such stability. Previously, we produced a recombinant 74-kDa collagenase from Grimontia hollisae, which spontaneously became truncated to ~60 kDa and possessed no stability. In this study, to generate G. hollisae collagenase useful as a collagenase product, we designed recombinant 62-kDa collagenase consisting only of the catalytic domain, which exhibits high production efficiency. We demonstrated that this recombinant collagenase is stable and active under physiological conditions. Moreover, it possesses higher specific activity against collagen and cleaves a wider variety of collagens than a standard collagenase product from C. histolyticum. Furthermore, it dissociated murine pancreata by digesting the collagens within the pancreata in a dose-dependent manner, and this dissociation facilitated isolation of pancreatic islets with masses and numbers comparable to those isolated using the standard collagenase from C. histolyticum. Implantation of these isolated islets into five diabetic mice led to normalisation of the blood glucose concentrations of all the recipients. These findings suggest that recombinant 62-kDa collagenase from G. hollisae can be used as a collagenase product to isolate primary cells.


Assuntos
Separação Celular/métodos , Colagenases/metabolismo , Proteínas Recombinantes/metabolismo , Vibrionaceae/enzimologia , Animais , Ilhotas Pancreáticas/citologia , Ilhotas Pancreáticas/metabolismo , Camundongos , Vibrionaceae/genética
6.
Org Biomol Chem ; 17(14): 3599-3603, 2019 04 03.
Artigo em Inglês | MEDLINE | ID: mdl-30912560

RESUMO

Cationic fluorophore homodimer probes 1 and 2 bearing 7-aminocoumarin and naphthalimide dyes, respectively, connected via diethylenetriamine (DETA) spacer, have been developed to demonstrate the validity of our modular probe design on the basis of the triamine-based spacer.

7.
FEBS Open Bio ; 8(10): 1691-1702, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30338219

RESUMO

The collagenase secreted by Grimontia hollisae strain 1706B is a 74 kDa protein that consists of two parts: the catalytic module and a C-terminal segment that includes the bacterial pre-peptidase C-terminal domain. Here, we produced a recombinant C-terminal segment protein and examined its ability to bind collagen and other characteristics as compared with collagen-binding domains (CBDs) derived from Hathewaya histolytica (Clostridium histolyticum) collagenases; these CBDs are the only ones thus far identified in bacterial collagenases. We found that the C-terminal segment binds to collagen only when the collagen is in its triple-helical conformation. Moreover, the C-terminal segment and the CBDs from H. histolytica have comparable characteristics, including binding affinity to type I collagen, substrate spectrum, and binding conditions with respect to salt concentration and pH. However, the C-terminal segment has a completely different primary structure from those of the CBDs from H. histolytica. As regards secondary structure, in silico prediction indicates that the C-terminal segment may be homologous to those in CBDs from H. histolytica. Furthermore, we performed collagenase assays using fluorescein isothiocyanate-labeled type I collagen to show that the C-terminal segment positively contributes to the collagenolytic activity of the 74 kDa collagenase from G. hollisae.

8.
J Agric Food Chem ; 66(33): 8737-8743, 2018 Aug 22.
Artigo em Inglês | MEDLINE | ID: mdl-30060651

RESUMO

Hydroxyproline (Hyp) is a collagen-specific amino acid formed by post-translational hydroxylation of Pro residues. Various Hyp-containing oligopeptides are transported into the blood at high concentrations after oral ingestion of collagen hydrolysate. Here we investigated the angiotensin-converting enzyme (ACE) inhibitory activity of X-Hyp-Gly-type tripeptides. In an in vitro assay, ginger-degraded collagen hydrolysate enriched with X-Hyp-Gly-type tripeptides dose-dependently inhibited ACE and various synthetic X-Hyp-Gly-type tripeptides showed ACE-inhibitory activity. In particular, strong inhibition was observed for Leu-Hyp-Gly, Ile-Hyp-Gly, and Val-Hyp-Gly with IC50 values of 5.5, 9.4, and 12.8 µM, respectively. Surprisingly, substitution of Hyp with Pro dramatically decreased inhibitory activity of X-Hyp-Gly, indicating that Hyp is important for ACE inhibition. This finding was supported by molecular docking experiments using Leu-Hyp-Gly/Leu-Pro-Gly. We further demonstrated that prolyl hydroxylation significantly enhanced resistance to enzymatic degradation by incubation with mouse plasma. The strong ACE-inhibitory activity and high stability of X-Hyp-Gly-type tripeptides highlight their potential for hypertension control.


Assuntos
Inibidores da Enzima Conversora de Angiotensina/química , Colágeno/química , Peptídeos/química , Animais , Hidroxilação , Hidroxiprolina/química , Cinética , Camundongos , Simulação de Acoplamento Molecular , Peptídeos/sangue , Renina/química , Renina/metabolismo
9.
Immun Inflamm Dis ; 6(2): 245-255, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29388365

RESUMO

INTRODUCTION: Collagen peptides have been widely used as a food supplement. After ingestion of collagen peptides, oligopeptides containing hydroxyproline (Hyp), which are known to have some physiological activities, are detected in peripheral blood. However, the effects of collagen-peptide administration on immune response are unclear. In the present study, we tested the effects of collagen-peptide ingestion on allergic response and the effects of collagen-derived oligopeptides on CD4+ T-cell differentiation. METHODS: BALB/c mice fed a collagen-peptide diet were immunized with ovalbumin (OVA), and their serum IgE and IgG levels, active cutaneous anaphylaxis, and cytokine secretion by splenocytes were examined. Naive CD4+ T cells were stimulated with anti-CD3 and anti-CD28 in the presence of collagen-derived oligopeptides, and the expression of IFN-γ, IL-4, and Foxp3 was analyzed. RESULTS: In an active anaphylaxis model, oral administration of collagen peptides suppressed serum OVA-specific immunoglobulin E (IgE) production and diminished anaphylaxis responses. In this model, the ingestion of collagen peptides skewed the pattern of cytokine production by splenocytes toward T-helper (Th) type 1 and regulatory T (Treg) cells. In vitro T-helper cell differentiation assays showed that Hyp-containing oligopeptides promoted Th1 differentiation by upregulating IFN-γ-induced signal transducer and activator of transcription 1 (STAT1) signaling. These oligopeptides also promoted the development of Foxp3+ Treg cells in response to antigen stimulation in the presence of TGF-ß. CONCLUSIONS: Collagen-peptide ingestion suppresses allergic responses by skewing the balance of CD4+ T cells toward Th1 and Treg cells and seems to be a promising agent for preventing allergies and inflammatory diseases.


Assuntos
Anafilaxia/prevenção & controle , Colágeno/administração & dosagem , Suplementos Nutricionais , Linfócitos T Reguladores/efeitos dos fármacos , Células Th1/efeitos dos fármacos , Administração Oral , Anafilaxia/sangue , Anafilaxia/dietoterapia , Anafilaxia/imunologia , Animais , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/imunologia , Colágeno/imunologia , Modelos Animais de Doenças , Humanos , Imunoglobulina E/sangue , Imunoglobulina E/imunologia , Ativação Linfocitária/efeitos dos fármacos , Ativação Linfocitária/imunologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Ovalbumina/imunologia , Peptídeos/administração & dosagem , Peptídeos/imunologia , Linfócitos T Reguladores/imunologia , Células Th1/imunologia
10.
Biosci Biotechnol Biochem ; 81(9): 1823-1828, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28675098

RESUMO

Wheat gluten is a Pro-rich protein complex comprising glutenins and gliadins. Previous studies have reported that oral intake of enzymatic hydrolysates of gluten has beneficial effects, such as suppression of muscle injury and improvement of hepatitis. Here, we utilized ginger protease that preferentially cleaves peptide bonds with Pro at the P2 position to produce a novel type of wheat gluten hydrolysate. Ginger protease efficiently hydrolyzed gluten, particularly under weak acidic conditions, to peptides with an average molecular weight of <600 Da. In addition, the gluten hydrolysate contained substantial amounts of tripeptides, including Gln-Pro-Gln, Gln-Pro-Gly, Gln-Pro-Phe, Leu-Pro-Gln, and Ser-Pro-Gln (e.g. 40.7 mg/g at pH 5.2). These gluten-derived tripeptides showed high inhibitory activity on dipeptidyl peptidase-IV with IC50 values of 79.8, 70.9, 71.7, 56.7, and 78.9 µM, respectively, suggesting that the novel gluten hydrolysate prepared using ginger protease can be used as a functional food for patients with type 2 diabetes.


Assuntos
Dipeptidil Peptidase 4/metabolismo , Inibidores da Dipeptidil Peptidase IV/metabolismo , Glutens/metabolismo , Oligopeptídeos/metabolismo , Peptídeo Hidrolases/metabolismo , Triticum/química , Zingiber officinale/enzimologia , Concentração de Íons de Hidrogênio , Hidrólise , Especificidade por Substrato
11.
J Org Chem ; 81(10): 4196-201, 2016 05 20.
Artigo em Inglês | MEDLINE | ID: mdl-27123640

RESUMO

A key compound, a precursor of water-soluble cyclophane hexamer, was prepared via Williamson ether synthesis of tetraaza[6.1.6.1]paracyclophane derivatives bearing a bromoacetamide moiety with triphenylene-2,3,6,7,10,11-hexaol as a core. A cationic cyclophane hexamer (1) was obtained by removing the protecting groups from the precursor. Fluorescence titration experiments proved that cationic cyclophane hexamer 1 showed macrocyclic multivalency effects; i.e., 1:1 host/guest binding constants (K) of 1 with anionic guests, 6-anilinonaphthalene-2-sulfonate and 6-p-toluidinonaphthalene-2-sulfonate, were increased about 63- and 62-fold, respectively, relative to those of monomeric cyclophane. Similarly, anionic cyclophane hexamer 2, which was easily prepared from 1, showed macrocyclic multivalency effects in K values with cationic guests such as hydrochlorides of doxorubicin and daunorubicin as an anticancer drug.

12.
J Org Chem ; 80(19): 9722-7, 2015 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-26360807

RESUMO

Cationic and anionic cyclophanes bearing a biotin moiety were synthesized as a water-soluble host (1a and 1b, respectively). Both hosts 1a and 1b were found to strongly bind avidin with binding constants of 1.3 × 10(8) M(-1), as confirmed by surface plasmon resonance measurements. The present conjugate of 1a with avidin (1a-avidin) showed an enhanced guest binding affinity toward fluorescence guests such as TNS and 2,6-ANS. The K values of 1a-avidin conjugate with TNS and 2,6-ANS were ~19-fold larger than those of monocyclic cyclophane 1a with the identical guests. Favorable hydrophobic and electrostatic interactions between 1a-avidin and TNS were suggested by computer-aided molecular modeling calculations. Moreover, addition of excess biotin to the complexes of 1a-avidin with the guests resulted in dissociation of 1a-avidin to avidin and 1a having less guest-binding affinity. Conversely, such enhancements in the guest-binding affinity were not obviously observed for the conjugate of anionic 1b with avidin (1b-avidin) due to electrostatic repulsion between anionic 1b and anionic guests.


Assuntos
Avidina/síntese química , Biotina/síntese química , Íons/química , Avidina/química , Sítios de Ligação , Biotina/química , Biotinilação , Interações Hidrofóbicas e Hidrofílicas , Cinética , Modelos Moleculares , Ligação Proteica
13.
J Org Chem ; 78(20): 10437-42, 2013 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-24047400

RESUMO

As a quencher-type host, dabsyl-appended cyclophanes bearing positively and negatively charged side chains (1a and 1b, respectively) were synthesized. Formation of cyclophane heterodimers of 1a with anionic fluorescent cyclophane bearing a pyrene moiety 2b was confirmed by fluorescence titration experiments. The 1:1 binding constant (K) of 1a toward 2b was calculated to be 1.6 × 10(5) M(-1). On the other hand, almost no complexation affinity of 1a toward cationic analogue of fluorescent cyclophane 2a was confirmed by the identical methods, indicating that electrostatic interactions became effective in the formation of cyclophane heterodimers. In addition, van't Hoff analysis applied to the temperature-dependent K values for the heterodimer formation gave negative enthalpy (ΔH) and entropy changes (ΔS). The large and negative ΔH values as well as small and also negative ΔS values showed that the complexation is an exothermic and enthalpy-controlled but not entropy-driven process. A similar trend of molecular recognition was also confirmed for formation of cyclophane heterodimers of 1b with 2a by the identical methods.

14.
J Org Chem ; 78(11): 5463-9, 2013 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-23679225

RESUMO

Water-soluble cationic cyclophane having diphenyl disulfide moieties (1a) was synthesized as a reduction-responsive degradable host. The stoichiometry for the complex of 1a with anionic fluorescence guests, such as 4,4'-bis(1-anilinonaphthalene-8-sulfonate) (Bis-ANS) and 4-(1-pyrene)-butanoic acid (PBA), was confirmed to be 1:1 host:guest by a Job plot. The binding constants (K) of 1a toward Bis-ANS and PBA were evaluated to be 6.7 × 10(3) and 4.5 × 10(4) M(-1), respectively, as confirmed by fluorescence spectroscopy. Reduction of disulfide bonds of 1a by dithiothreitol gave its reduced form having poor guest-binding affinity that led to release of the entrapped guest molecules to the bulk aqueous phase. Meanwhile, anionic cyclophane 1b, which was derived from 1a by a reaction with succinic anhydride, binds cationic anticancer drugs, such as daunorubicin hydrochloride (DNR) and doxorubicin hydrochloride (DOX), with a K of 2.1 × 10(3) and 7.5 × 10(2) M(-1), respectively. A similar reduction-responsive guest release feature was observed when DNR and DOX were employed as a guest for complexation with 1b.


Assuntos
Compostos Aza/química , Compostos Aza/síntese química , Dissulfetos/química , Compostos Macrocíclicos/química , Compostos Macrocíclicos/síntese química , Sítios de Ligação , Estrutura Molecular , Oxirredução , Solubilidade , Água/química
15.
J Bacteriol ; 193(12): 3049-56, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21515782

RESUMO

The collagenase gene was cloned from Grimontia (Vibrio) hollisae 1706B, and its complete nucleotide sequence was determined. Nucleotide sequencing showed that the open reading frame was 2,301 bp in length and encoded an 84-kDa protein of 767 amino acid residues. The deduced amino acid sequence contains a putative signal sequence and a zinc metalloprotease consensus sequence, the HEXXH motif. G. hollisae collagenase showed 60 and 59% amino acid sequence identities to Vibrio parahaemolyticus and Vibrio alginolyticus collagenase, respectively. In contrast, this enzyme showed < 20% sequence identity with Clostridium histolyticum collagenase. When the recombinant mature collagenase, which consisted of 680 amino acids with a calculated molecular mass of 74 kDa, was produced by the Brevibacillus expression system, a major gelatinolytic protein band of ~ 60 kDa was determined by zymographic analysis. This result suggested that cloned collagenase might undergo processing after secretion. Moreover, the purified recombinant enzyme was shown to possess a specific activity of 5,314 U/mg, an ~ 4-fold greater activity than that of C. histolyticum collagenase.


Assuntos
Brevibacillus/metabolismo , Clonagem Molecular , Colagenases/metabolismo , Regulação Bacteriana da Expressão Gênica/fisiologia , Regulação Enzimológica da Expressão Gênica/fisiologia , Vibrio/enzimologia , Vibrio/genética , Sequência de Aminoácidos , Sequência de Bases , Brevibacillus/genética , Colágeno Tipo I/metabolismo , Colagenases/genética , Hidrólise , Cinética , Dados de Sequência Molecular , Recombinação Genética , Vibrio/metabolismo
16.
Org Biomol Chem ; 6(17): 3166-70, 2008 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-18698476

RESUMO

Rotaxane-type receptors, which were composed of anionic cyclophane-based resorcinarene tetramers as the wheel and a 2,6-disubstituted naphthalene derivative having two fluorophore moieties, such as fluorescein and rhodamine residues, as the axle ( and , respectively), were prepared. Rotaxane-type receptors and bound histone, a small basic protein component of eukaryotic chromatins, with binding constants of 2.3 x 10(6) and 9.0 x 10(5) M(-1), respectively. The rotaxane-type receptors showed fluorescence sensing ability with remarkable histone selectivity. Moreover, fluorescence resonance energy transfer (FRET) between the fluorescein residues of and the rhodamine residues of took place in the presence of histone, which was a useful method for the detection of histone.


Assuntos
Calixarenos/química , Calixarenos/metabolismo , Fluoresceína/química , Corantes Fluorescentes/química , Histonas/química , Histonas/metabolismo , Fenilalanina/análogos & derivados , Rodaminas/química , Rotaxanos/química , Fluorescência , Transferência Ressonante de Energia de Fluorescência , Estrutura Molecular , Fenilalanina/química , Fenilalanina/metabolismo , Rotaxanos/metabolismo , Espectrometria de Fluorescência
17.
J Org Chem ; 73(8): 3205-11, 2008 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-18351779

RESUMO

Water-soluble cyclophane heptadecamers (17a and 17b), which were constructed with the core cyclophane heptadecamer and 36 polar side chains with a terminal galactose or glucose residue, respectively, were prepared. An analogous cyclophane pentamer (5a) was also prepared. The stoichiometry for the complex of the cyclophane oligomers with fluorescence guests such as TNS was confirmed to be 1:1 host:guest by a Job plot. The guest-binding affinity of cyclophane heptadecamers 17a and 17b was much enhanced relative to that of a corresponding monocyclic cyclophane (1a), i.e., the 1:1 binding constant (K) values for 17a with TNS, 2,6-ANS, and 1,8-ANS were ca. 1700-, 1600-, and 1500-fold larger than those of 1a for the identical guests, respectively, which reflects the multivalency effects in macrocycles. Meanwhile, the corresponding K values for the cyclophane pentamer 5a with TNS, 2,6-ANS, and 1,8-ANS were ca. 250-, 250-, and 110-fold larger than those of 1a for the identical guest, respectively.

18.
J Am Chem Soc ; 129(44): 13698-705, 2007 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-17929813

RESUMO

A cyclophane-based resorcinarene trimer (3) bearing a dansyl moiety as an environmentally sensitive fluorophore was prepared by stepwise condensation of a tetraaza[6.1.6.1]paracyclophane skeleton with a dansyl moiety and three resorcinarene derivatives having heptacarboxylic acid residues in this sequence. The dansyl-appended cyclophane exhibited the following fluorescence properties regarding solvent polarity dependency and histone surface recognition: With increasing dioxane contents in dioxane/water solvents, the fluorescence intensity originating from the dansyl moiety of 3 increased along with a concomitant blue shift of the fluorescence maximum (lambdaem). The microenvironmentally sensitive fluorescence properties of dansyl fluorophore were maintained, even when the dansyl moiety was covalently attached to a cyclophane. Most interestingly, the cyclophane-based resorcinarene trimer exhibited recognition and fluorescence sensing capabilities toward histone, a small basic protein of eukaryotic chromatins. The fluorescence intensity originating from 3 increased along with a concomitant blue shift of lambdaem upon the addition of histone, reflecting the formation of 3-histone complexes. A relatively large fluorescence polarization (P) value was obtained for the 3-histone complexes (0.15), reflecting highly restricted conformations of 3, and the obtained P value was much larger than that of 3 alone in aqueous medium (0.07). The binding constant (K) of 3 with histone (unit basis) was estimated to be 2.1 x 106 M-1. On the other hand, upon the addition of acetylated histone (Ac-histone) to an aqueous solution containing 3, the extent of change in fluorescence intensity originating from the dansyl group of 3 was almost negligible, indicating that the electrostatic interactions between 3 and Ac-histone were weak. In addition, the fluorescence spectral changes were also small or negligible upon the addition of other proteins such as albumin, ovalbumin, peanut agglutinin, myoglobin, concanavalin A, cytochrome c, and lysozyme, having isoelectric points of 4.7, 4.8, 5.7-6.7, 6.8, 7.1, 9, and 11.0, respectively, to an aqueous solution containing 3.


Assuntos
Calixarenos/química , Éteres Cíclicos/química , Histonas/química , Fenilalanina/análogos & derivados , Compostos Aza/química , Dimerização , Fluorescência , Compostos Macrocíclicos/química , Modelos Químicos , Conformação Molecular , Fenilalanina/síntese química , Fenilalanina/química , Sensibilidade e Especificidade , Propriedades de Superfície , Fatores de Tempo
19.
J Org Chem ; 72(2): 610-6, 2007 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-17221981

RESUMO

As a new class of host for both specific proteins and hydrophobic molecular guests, cyclophane-based resorcinarene oligomers were designed on the basis of a molecular design that allows the assembly of four or 12 anionic resorcinarenes on a cyclophane skeleton. We prepared a cyclophane-based resorcinarene tetramer (4), constructed with a tetraaza[6.1.6.1]-paracyclophane skeleton and four resorcinarenes bearing heptacarboxylic acid residues that connect to the macrocycle through amide linkages. In addition, we prepared an extended analogical dodecamer (12), which was constructed with a pentakis(cyclophane) skeleton and 12 resorcinarenes. The cyclophane-based resorcinarene oligomers exhibited potent recognition capabilities toward histone, a small basic protein of eukaryotic chromatins. The binding constants (K) of cyclophane-based resorcinarene tetramer 4 and dodecamer 12 with histone were determined to be 1.3x107 and 8.4x107 M-1, respectively, by means of surface plasmon resonance measurements. The K values of 4 and 12 with histone were 31- and 200-fold larger than that of an untethered reference resorcinarene, reflecting the multivalency effects in resorcinarenes. In addition to that, cyclophane-based resorcinarene tetramer 4 and dodecamer 12 captured hydrophobic guests such as 6-p-toluidinonaphthalene-2-sulfonate, with respective binding constants of 2.4x103 and 2.5x104 M-1 in an aqueous HEPES buffer as evaluated by fluorescence spectroscopy. Furthermore, the resorcinarene oligomers were also found to act as guest carriers from the bulk aqueous phase to histone surfaces, as confirmed by fluorescence spectroscopy.

20.
Org Biomol Chem ; 3(4): 654-60, 2005 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-15703803

RESUMO

Chiral macrocycles with eight (R)- and (S)-methylbenzylurea residues on the resorcinarene skeleton linked through a hexyl or dodecyl spacer having amide linkages have been prepared by the reactions of the corresponding octaamine derivative with (R)- and (S)-alpha-methylbenzylisocyanate, respectively. In chloroform, the urea-functionalized resorcinarenes with hexyl spacers form intramolecular hydrogen bonds by bundling the urea and amide residues in a cyclic fashion to give a self-folding cavitand. The urea and amide residues are cooperatively oriented in the same direction to result in asymmetric hydrogen-bonding belts. Unique circular dichroism (CD) bands are induced in the absorption wavelength ranges of the macrocyclic skeleton, caused by a chirality transmission from their chiral urea termini through hexyl spacers in the self-folded conformation. On the other hand, urea-functionalized resorcinarenes with a longer dodecyl spacer do not show such unique CD bands on the macrocycle, because of their weaker propensity for hydrogen bond formation. The characteristic CD bands of the urea-functionalized self-folding macrocycles disappeared upon complexation with anions such as chloride and bromide, reflecting breaking of the intramolecular hydrogen-bonding belts.

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