Residue- and sequence-selective binding of nonaromatic dipeptides by bis(beta-cyclodextrin) with a functional tether.
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Binding Sites↗
Biomedical subjects
Fei Ding
Publications and source records attributed to Fei Ding.
Diastereo- and enantioselective dearomatization of rhenium-bound naphthalenes.
Dihapto-coordinated naphthalene complexes of the form TpRe(CO)(L)(eta(2)-naphthalene) (L = PMe(3), pyridine, or 1-methylimidazole) undergo electrophilic addition with dimethoxymethane and with various Michael acceptors to generate 1H-naphthalenium species. These naphthalenium complexes undergo intra- or intermolecular nucleophilic addition reactions with stabilized enolates, silyl ketene acetals, or enols to form the corresponding dihydronaphthalene complexes. Oxidative decomplexation generates the free dihydronaphthalene. When a resolved form of the rhenium dearomatization agent is used, these reactions can be performed enantioselectively. DFT calculations provide a useful guide in explaining the observed stereochemistry. Depending on reaction conditions, a Michael-Michael ring-closure sequence (MIMIRC) or a net [2 + 4] cycloaddition with the bound naphthalene is also observed, and the corresponding tricyclic molecules can be removed from the metal in high yield.
Catalysis↗
Solid-state induced control of kinetically unstable stereoisomers.
Arene complexes of the form TpM(pi-acid)(L)(eta2-arene) (Tp = hydridotris(pyrazolyl)borate, M = Re, Mo, or W, pi-acid = CO or NO, L = 1-alkylimidazole, pyridine, PMe3, arene is prochiral) exist as a dynamic equilibrium of coordination diastereomers in solution. In both crystalline and amorphous solid states, however, only one diastereomer is present. Reactions on the bound arenes in these complexes have been performed stereoselectively, by exploiting the homomorphic nature of the solid phase.
Borates↗
Thermodynamics of the molecular and chiral recognition of cycloalkanols and camphor by modified beta-cyclodextrins possessing simple aromatic tethers.
The complex stability constants (K(S)) and thermodynamic parameters (DeltaG degrees, DeltaH degrees, and TDeltaS degrees ) for 1:1 inclusion complexation of beta-cyclodextrin (beta-CD) derivatives, 6-O-phenyl-beta-CD (2) 6-O-(4-formyl-phenyl)-beta-CD (3), 6-O-(4-nitrophenyl)-beta-CD (4), 6-O-(4-bromophenyl)-beta-CD (5), 6-O-(4-chlorophenyl)]-beta-CD (6), and 6-O-(4-hydroxybenzoyl)-beta-CD (7) with representative guest molecules, cyclic alcohols (cyclopentanol, cyclohexanol, cycloheptanol, cyclooctanol), (+/-)-borneol, and (+/-)-camphor, have been determined by means of titration microcalorimetry in an aqueous phosphate buffer solution (pH = 7.20) at 298.15 K. The results obtained indicate that the introduction to beta-CD of an aromatic ring bearing different substituent groups significantly enhances the molecular binding ability and moderately alters the chiral discrimination ability for the guests examined here, displaying the highest enantioselectivity of up to 4.01 for the inclusion complexation of 6 with (+/-)-camphor. The enhanced molecular/chiral discrimination ability caused by derivatization is attributed solely to increased positive entropy changes due to the expanding hydrophobic interaction and desolvation effects. The binding modes of host-guest interactions derived from ROESY spectroscopy data show that the resulting complex of 4 and (+)-borneol possesses better induced-fit interaction as compared to (-)-borneol, which is responsible for the enhanced molecular/chiral recognition ability.
Alcohols↗
Diastereoisomer-selective inclusion complexation of Cinchona alkaloids with a modified beta-cyclodextrin: fluorescent behavior enhanced by chiral-tether binding. Short communication.
The molecular 1:1 complexation of cinchona alkaloids by mono(6-deoxy-6-{[(R)-1-(hydroxymethyl)propyl]amino})-beta-cyclodextrin (1) in aqueous solution has been investigated by 2D-NMR, fluorescence titration, and fluorescence-lifetime experiments. Generally, with 1 as the host, in contrast to beta-cyclodextrin proper, strong binding of quinine (2; Ka = 84,200 M(-1)) and quinidine (3; Ka = 27,300 M(-1)) at pH 6.8 was observed, as monitored by an increase in fluorescence intensity, with a fair degree of diastereoisomer discrimination (ca. 3:1). To rationalize these results, two possible cooperative complexation modes, including specific H-bonding interactions to the chiral tether of the cyclodextrin portion, are proposed.
Binding Sites↗
Expression of genes for collagen production and NF-kappaB gene activation of in vivo healing flexor tendons.
PURPOSE: Collagen production and reorientation are core events in the healing of tendons and are essential for gaining tensile strength. Intrasynovial flexor tendons are composed chiefly of type I collagen; however, type III collagen is the earliest to be laid down in the wounds. We investigated the expression of genes for type I collagen, type III collagen and its promoter, and nuclear transcription factor kappa B (NF-kappaB) in an in vivo tendon injury model in chickens. METHODS: Flexor digitorum profundus tendons of the long toes of 12 white leghorn chickens were transected partially and repaired with the modified Kessler method. The repaired tendon segments were harvested at 2, 4, and 8 weeks after surgery with 4 chickens used each time. The uninjured tendons from 4 other chickens were used as the controls. We determined the expression of the collagen and NF-kappaB genes in the tendons with reverse transcription and polymerase chain reaction and semiquantitative analysis of gene bands in gel electrophoresis. RESULTS: Expression of the type III collagen gene was enhanced significantly in the tendons at 2, 4, and 8 weeks after repair. Levels of expression of the type III collagen promoter gene were increased significantly in the healing tendons at 2 and 4 weeks. Increases in the expression of the type I collagen gene occurred later than those of the type III collagen and NF-kappaB genes and were significant in the tendons after 4 and 8 weeks. The NF-kappaB gene was activated in the tendons at all the healing periods. CONCLUSIONS: Expression of type III collagen and its promoter genes is enhanced remarkably during in vivo flexor tendon healing. The NF-kappaB gene is activated during the healing process. Expression of the type I collagen gene increases remarkably at later periods of in vivo tendon healing and is proportional to that of the NF-kappaB gene.
Animals↗
Supramolecular self-assemblies of beta-cyclodextrins with aromatic tethers: factors governing the helical columnar versus linear channel superstructures.
A series of 6-O-(p-substituted phenyl)-modified beta-cyclodextrin derivatives, i.e., 6-O-(4-bromophenyl)-beta-CD (1), 6-O-(4-nitrophenyl)-beta-CD (2), 6-O-(4-formylphenyl)-beta-CD (3), 6-phenylselenyl-6-deoxy-beta-CD (4), and 6-O-(4-hydroxybenzoyl)-beta-CD (5), were synthesized, and their inclusion complexation behavior in aqueous solution and self-assembling behavior in the solid state were comparatively studied by NMR spectroscopy, microcalorimetry, crystallography, and scanning tunneling microscopy. Interestingly, (seleno)ethers 1-4 and ester 5 displayed distinctly different self-assembling behavior in the solid state, affording a successively threading head-to-tail polymeric helical structure for the (seleno)ethers or a mutually penetrating tail-to-tail dimeric columnar channel structure for the ester. Combining the present and previous structures reported for the relevant beta-CD derivatives, we further deduce that the pivot heteroatom, through which the aromatic substituent is tethered to beta-CD, plays a critical role in determining the helix structure, endowing the 2-fold and 4-fold axes to the N/O- and S/Se-pivoted beta-CD aggregates, respectively. This means that one can control the self-assembling orientation, alignment, and helicity in the solid state by finely tuning the pivot atom and the tether length. Further NMR and calorimetric studies on the self-assembling behavior in aqueous solution revealed that the dimerization step is the key to the formation of linear polymeric supramolecular architecture, which is driven by favorable entropic contributions.
Benzene Derivatives↗
Determination of hydroxyl radical by capillary zone electrophoresis with amperometric detection.
Hydroxyl radical (OH*) can cause severe damage to cells and tissues. However, its analysis is very difficult for its high reactivity and very short half-life. In this paper, a simple and highly sensitive method, capillary zone electrophoresis with amperometric detection (CZE-AD) was introduced indirectly to determine OH* by determining its reaction products with salicylic acid (SAL), 2,3-dihydroxybenzoic acid (2,3-DHBA) and 2,5-dihydroxybenzoic acid (2,5-DHBA). The optimum conditions of CZE-AD for the determination of 2,3-DHBA and 2,5-DHBA were explored. Under the optimum conditions, SAL, 2,3-DHBA and 2,5-DHBA could be perfectly separated within 15 min, and the linearity ranges of 2,3-DHBA and 2,5-DHBA were between 1.0 x 10(-7) and 1.0 x 10(-4) mol l(-1). Their detection limits were as low as 2 x 10(-8) mol l(-1), which were much lower than that in CE-UV method. The method was also applied to study the free OH* scavenging activity of angelica polysaccharide. The experimental results showed that this CZE-AD method was very sensitive and practical in both the determination of free OH* and the evaluation of free OH* scavenging activities of antioxidants.
Electrochemistry↗
Overexpression of beta-1,4-galactosyltransferase I in rat Schwann cells promotes the growth of co-cultured dorsal root ganglia.
The cell surface beta-1,4-galactosyltransferase I (beta-1,4-GalT-I) functions as one of the receptors of laminin during the neurite outgrowth on basal lamina by binding to N-linked oligosaccharides in the laminin E8 domain. In this study, we demonstrated that the purified rat Schwann cells transfected with the expression plasmid of beta-1,4-GalT-I cDNA transiently promoted outgrowth and elongation of the neurites from co-cultured rat dorsal root ganglia, while those transfected with the antisense expression plasmid of beta-1,4-GalT-I had the opposite effects. These results suggested that the expression of beta-1,4-GalT-I in Schwann cells of peripheral nerve might promote both growth of developmental neuron and regeneration of injured nerve.
Animals↗
Determination of hydrochlorothiazide and rutin in Chinese herb medicines and human urine by capillary zone electrophoresis with amperometric detection.
In this paper, capillary zone electrophoresis with amperometric detection (CZE-AD) was firstly applied to the simultaneous determination of rutin (RT) and hydrochlorothiazide (HCT) in compound Chinese herb medicines and human urine samples. The two analytes could be perfectly analyzed within 12 min and showed significant current responses at carbon electrode under the optimum conditions. It was found that the linear range of HCT was from 2.0 x 10(-6) to 1.0 x 10(-4) mol l(-1) and that of RT was from 1.0 x 10(-6) to 1.0 x 10(-4) mol l(-1). Their sensitivity was determined by linear regression and calculated as 7.02 x 10(4) and 2.17 x 10(5) nA l mol(-1), respectively, and their detection limits were 5.0 x 10(-7) and 2.0 x 10(-7) mol l(-1), respectively (S/N=3). Above results demonstrated that this method was of high sensitivity, good repeatability, high selectivity and could be used in metabolic kinetics studies of medicines. Satisfactory results were obtained when this method was used to simultaneously analyze the amounts of RT and HCT in one general compound Chinese herb medicine-Zhen Ju jiang Ya Pian and human urine samples.
Drugs, Chinese Herbal↗
Determination of the compositions of polysaccharides from Chinese herbs by capillary zone electrophoresis with amperometric detection.
In this paper, capillary zone electrophoresis with amperometric detection (CZE-AD) was applied to determine the compositions of hetero-polysaccharides from Chinese herbs, Angelica sinensis and flax by analyzing their hydrolyzed monosaccharides: fucose, galactose, glucose, arabinose, rhamnose and xylose. Under the selected optimum conditions, the six monosaccharides could be perfectly separated within 25 min and showed significant current responses at copper electrodes. The linear ranges of the six monosaccharides were all from 5.0 x 10(-6) to 2.0 x 10(-4) mol L(-1) and their detection limits were lower or near 1.0 x 10(-6) mol L(-1) (S/N = 3). Experiments showed that the Angelica sinensis polysaccharide was composed of fucose, galactose, glucose, arabinose, rhamnose and xylose (mole ratio 1.0:13.6:15.0:8.7:21.3:3.7), and the flax polysaccharide was composed of galactose, glucose and arabinose (mole ratio 1.0:4.98:1.1). The purity of these polysaccharides leached by the introduced leaching method was 98.3 and 97.6%, respectively. Analyzing polysaccharides by this method has some merits of speed, simple instrumentation and operation, high sensitivity and high reproducibility.
Drugs, Chinese Herbal↗
Effect of diluting agent on sensitivity in capillary electrophoresis with amperometric detection.
Besides the running buffer, pH of buffer, separation voltage and sampling time, the diluting agent was studied in this paper as one of the important factors influencing the sensitivity in capillary electrophoresis (CE) with amperometric detection (AD) when electrokinectic sampling was used. Clonidine hydrochloride, hydrochlorothiazide and rutin, which are positively charged, neutral and negatively charged, respectively, in aqueous solutions, could be perfectly separated by CE with 25 mmol x L(-1) Na(2)B(4)O(7) - 50 mmol x L(-1) NaH(2)PO(4) as running buffer and detected by measuring their current responses with AD. Before CE running, some kinds of diluents including water, methanol, formamide, running buffer, hydrochloric acid and sodium hydroxide were, respectively, applied to dilute the stock solutions of above three analytes and their effects on the sensitivity of CE-AD were investigated. The results showed that for electrokinetic injection, the current responses of these three analytes were greatly affected in different ways when different diluting agents were used. This method was applied to simultaneously determine the active ingredients in one Chinese compound hypotensor named Zhen Ju Jiang Ya Pian, in which the contents of clonidine hydrochloride, hydrochlorothiazide and rutin is very different as 0.03 mg : 5 mg : 20 mg per tablet, and satisfactory results were obtained by adjusting their sensitivity by selecting the suitable diluting agent.
Buffers↗
Tendon healing in vitro: promotion of collagen gene expression by bFGF with NF-kappaB gene activation.
PURPOSE: Matrix synthesis of intrasynovial tendon cells and activation of nuclear transcription factors are pivotal to promotion of flexor tendon healing. We investigated the effects of basic fibroblast growth factor (bFGF) on synthesis of type I collagen and activation of nuclear transcription factor kappaB (NF-kappaB) in an in vitro culture model of intrasynovial tenocytes. METHOD: Tenocytes obtained from explant culture of rabbit intrasynovial tendon segments were treated with bFGF at concentrations of 0, 2, and 10 ng/mL. Expression of type I collagen and NF-kappaB genes was determined by quantitative analysis of products of reverse-transcription polymerase chain reactions. Proliferation of the cells was assessed by incorporation of bromodeoxyuridine into the DNA of the cells. RESULTS: Expression levels of type I collagen and NF-kappaB genes of tenocytes were increased significantly by bFGF. Cell proliferation as indicated by DNA labeling was promoted significantly by bFGF. Expression of the NF-kappaB gene increased proportionately to the amounts of bFGF stimulating the cells and was correlated with increases in proliferation rate of tenocytes. CONCLUSIONS: Results of this study show that expression of type I collagen and NF-kappaB genes is promoted manifestly by bFGF. The effects were proportionate to in vitro proliferation rates of tenocytes. The study indicated that matrix synthesis of flexor tendons can be promoted by bFGF and that NF-kappaB may play a pivotal role in initiating proliferation and type I collagen synthesis of tenocytes.
Analysis of Variance↗
Increased gene expression of beta-1,4-galactosyltransferase I in rat injured sciatic nerve.
During neurite outgrowth on basal lamina, cell-surface beta-1,4-galactosyltransferase I (beta-1,4-GalT-I) functions as one of the receptors of laminin by binding to N-linked oligosaccharides on the laminin E8 domain. In the present study, it was revealed that in rat injured sciatic nerves, the expression of beta-1,4-GalT-I mRNA reached its peak 2-3 d after axotomy in both proximal and distal stumps, and decreased thereafter as demonstrated by Northern blot analysis. In situ hybridization revealed that beta-1,4-GalT-I mRNAmainly localized in Schwann cells of the injured nerves. Moreover the Galbeta1-4GlcNAc (N-acetylglucosamine) group mainly localized in Schwann cells of the injured nerves by Ricinus communis agglutinin-I (RCA-I) lectin histochemistry. However, the changes in abundance of the Galbeta1-4GlcNAc group in injured nerves were not consistent with the expression of beta-1, 4-GalT-I mRNA. These findings indicate that beta-1,4-GalT-I might be involved in the regeneration of injured peripheral nerves at the early injury stage.
Animals↗
Dihapto coordination of carboxylic acid derivatives with an asymmetric rhenium pi-base: a new mechanism for amide isomerization?
The asymmetric pi basic metal fragment [TpRe(CO)(MeIm)] (Tp = hydridotris(pyrazolyl)borate, MeIm = 1-methylimidazole) forms thermally stable complexes with ethyl acetate, acetic anhydride, N-methylsuccinimide, N-acetylpyrrole, and N-methylmaleimide in which the metal binds a carbonyl group in a pi fashion. In all cases a single diastereomer is observed, indicating that one enantioface of the carbonyl is selectively coordinated. X-ray and NMR data for the compound TpRe(CO)(MeIm)(eta(2)-N-methylsuccinimide) indicate that metal coordination effectively removes the pi interaction between the bound carbonyl and the nitrogen of the succinimide ring.
Amides↗
Tandem 1,4-addition reactions with benzene and alkylated benzenes promoted by pentaammineosmium(II).
Electrophiles such as dimethoxymethane and 3-penten-2-one react with the complex [Os(NH(3))(5)(eta(2)-benzene)](2+) in the presence of triflic acid to form metastable benzenium intermediates. These benzenium intermediates further react with carbon nucleophiles including silyl ketene acetals, (silyloxy)alkenes, and phenyllithium in an overall tandem 1,4-addition sequence. The metal fragment controls the relative stereo- and regiochemistry for both electrophilic and nucleophilic addition steps. Upon oxidative demetalation with silver triflate, cis-1,4 cyclohexadienes are formed in yields ranging from 16 to 82%. This methodology can also be used to dearomatize toluene and ortho- and meta-xylene with unexpectedly high regio- and stereocontrol.
Benzene↗
ProbeMatchDB--a web database for finding equivalent probes across microarray platforms and species.
SUMMARY: ProbeMatchDB is a web-based database designed to facilitate the search of EST/cDNA sequences or STS markers that can be used to represent the same gene across different microarray platforms and species. It can be used for finding equivalent EST clones in the Research Genetics sequence verified clone set based on results from Affymetirx GeneChips. It will also help to identify probes representing orthologous genes across human, mouse and rat on different microarray platforms. AVAILABILITY: The database is accessible at http://brainarray.mhri.med.umich.edu/MARRAY/BC_ASP/brainarray.htm by clicking the 'Query ProbeMatchDB' link.
Animals↗
Molecular binding behavior of pyridine-2,6-dicarboxamide-bridged bis(beta-cyclodextrin) with oligopeptides: switchable molecular binding mode.
Bridged bis(beta-cyclodextrin) 1 with a pyridine-2,6-dicarboxamide linker was synthesized, and its inclusion complexation behavior with some aliphatic oligopeptides was investigated in aqueous buffer solution of pH 2.0 and 7.2 at 25 degrees C by means of circular dichroism, fluorescence, and 2D NMR techniques. The results show that the resulting inclusion complexes of 1 with oligopeptides adopt a cooperative "cyclodextrin-guest-cyclodextrin" sandwich binding mode in a neutral media, but a "guest-linker-cyclodextrin" coinclusion binding mode in an acidic media. These switchable binding modes consequently rationalize the binding ability of bis(beta-cyclodextrin) 1 at different pH values; that is, 1 shows the stronger association with oligopeptides in a neutral media. Because of the simultaneous contributions of hydrophobic, hydrogen bond, and electrostatic interactions, bis(beta-cyclodextrin) 1 affords length-selectivity up to 4.7 for the Gly-Gly/Gly-Gly-Gly pair at pH 2.0 and sequence-selectivity up to 4.2 for the Gly-Leu/Leu-Gly pair at pH 7.2. These phenomena are discussed from the viewpoint of the size-fit concept and the multipoint recognitions between host and guest.
Binding Sites↗