Addition Of CB Research Articles

Side‐chain polypseudorotaxanes by threading cucurbit[7]uril onto poly‐N‐n‐butyl‐N′‐(4‐vinylbenzyl)‐4,4′‐bipyridinium bromide chloride: Synthesis, characterization, and properties

AbstractA novel side‐chain polypseudorotaxanes P4VBVBu/CB[7] was synthesized from poly‐N‐n‐butyl‐N′‐(4‐vinylbenzyl)‐4,4′‐bipyridinium bromide chloride (P4VBVBu) and cucurbit [7]uril (CB[7]) in water by simple stirring at room temperature. CB[7] beads are localized on viologen units in side chains of polypseudorotaxanes as shown by 1H NMR, IR, XRD, and UV–vis studies, and it is considered that the hydrophobic and charge‐dipole interactions are the driving forces. TGA data show that thermal stability of the polypseudorotaxanes increases with the adding of CB[7] threaded. DLS data show that P4VBVBu and CB[7] could form polypseudorotaxanes, and the average hydrodynamic radius of the polypseudorotaxanes increases with increasing the concentration of CB[7]. The typical cyclic voltammograms indicate that the oxidation reduction characteristic of P4VBVBu is remarkably affected by the addition of CB[7] because of the formation of polypseudorotaxanes and the shielding effects of CB[7] threaded on the viologen units of polypseudorotaxanes. With the increase of the concentration of KBr or K2SO4, the formation of the polypseudorotaxanes was inhibited due to the shielding effects of both Br− or SO to viologen ion and K+ to CB[7] by UV–vis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2135–2142, 2010

Biological Catalysis Regulated by Cucurbit[7]uril Molecular Containers

We report the synthesis of two-faced inhibitors 1-5 that contain both enzyme inhibitor and cucurbit[n]uril binding domains. The enzyme binding domains of 1-5 bind to the active sites of bovine carbonic anhydrase (BCA) or acetylcholinesterase (AChE) and inhibit their catalytic activities. Addition of CB[7] to BCA*1 and BCA*2 results in the transient formation of the BCA*1*CB[7] and BCA*2*CB[7] ternary complexes that undergo rapid dissociation to form free catalytically active BCA along with CB[7]*1 and CB[7]*2. The on-off cycle can be performed repetitively by the sequential addition of competitive guest 8 and CB[7]. The detailed origins of this on-off switching of the catalytic activity of BCA is delineated by the combined inference of UV/vis catalytic assays, fluorescence displacement assays, (1)H NMR, along with measurement of the fundamental values of K(a), k(on), and k(off) for the various complexes involved. In contrast, addition of CB[7] to AChE*4(4) and AChE*5(4) results in the formation of thermodynamically stable ternary complexes AChE*4(4)*CB[7](4) and AChE*5(4)*CB[7](4) that are catalytically inactive. We highlight some of the advantages and disadvantages of the strategy, based on the direct competition between two receptors (e.g., enzyme and CB[7]) for a common inhibitor, used in this paper to control enzyme catalytic activity compared to the strategy employed by Nature involving the binding of an allosteric small molecule remote from the enzyme active site.

Toward supramolecular polymers incorporating double cavity cucurbituril hosts

We describe the synthesis of a series of guests ( 1– 6) containing two adamantylammonium ions separated by xylylene spacing groups and their complexation properties toward double cavity cucurbituril host bis- ns-CB[10]. We observed the preferential formation of 1:1, 2:2, and oligomeric complexes rather than the desired n: n supramolecular polymers. Guest 7, which contains a longer biphenyl spacer successfully precludes the formation of the 1:1 complex but results in the formation of the 2:2 complex (bis- ns-CB[10] 2· 7 2) rather than supramolecular polymer. Guest 8, which contains adamantylammonium, p-xylylene diammonium, and hexanediammonium ion binding regions is shown to reversibly form 2:2 and 1:2 complexes (bis- ns-CB[10] 2· 8 2 and bis- ns-CB[10]· 8 2) in response to changes in host:guest stoichiometry. Lastly, this equilibrium can be manipulated by the addition of exogenous CB[6], which selectively targets the hexanediammonium ion binding region of 8 and delivers the penta-molecular complex bis- ns-CB[10]· 8 2·CB[6] 2.

ANTIGENOTOXIC, FIBRINOLYTIC AND IMMUNOMODULATING ACTIVITY OF TRADITIONALLY FERMENTED SOY PRODUCT, CHUNGKUKJANG

Fibrinolytic, antigenotoxic and immunomodulating properties of chungkukjang were evaluated. The purified fibrinolytic enzyme was characterized as an alkaline serine protease with molecular weight of 22 kDa determined by fibrin zymography and stable over pH range 6.0-10.0 below 50C. The comet assay showed that N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced DNA damage level (190.8 AU) in 3T3 cells was considerably decreased to 121.2 AU with chungkukjang extracts (CB) showing 49.7% of protection. Incubation of the 3T3 cells with CB significantly reduced the cytotoxicity of MNNG. [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) assay revealed that the addition of CB enhanced the proliferation of RAW 264.7 (mouse leukemic monocyte macrophage cell line) macrophages up to about 150% of the control levels. RAW 264.7 macrophages incubated with CB induced a strong increase in nitric oxide (NO), tumor necrosis factor-a (TNF-a) and interleukin-1α (IL-1α) with a dose-dependent manner. After 24 h incubation with 1 mg/mL of CB, NO, TNF-a and IL-1α showed the highest production of 511, 2.46 and 0.258 ng/mL, respectively.

Stabilization of the base-off forms of vitamin B12 and coenzyme B12 by encapsulation of the α-axial 5,6-dimethylbenzimidazole ligand with cucurbit[7]uril

Cucurbit[7]uril (CB[7]) forms very stable complexes with the alpha-axial 5,6-dimethylbenzimidazole (alpha-DMB) nucleotide base when dissociated from the Co(III) center in vitamin B(12) (CNCbl, K(CB[7]) = (7.5 +/- 0.5) x 10(4) dm(3) mol(-1)) and coenzyme B(12) (AdoCbl, K(CB[7]) = (3.02 +/- 0.35) x 10(6) dm(3) mol(-1)). The inclusion of alpha-DMB ligand facilitates its release from the metal center and its subsequent protonation, with significantly higher pK(base-off) values of 3.77 and 6.61, than determined for the free CNCbl (0.11) and AdoCbl (2.67), respectively. Addition of CB[7] to the base-on form of CNCbl at pH 2 provides for a direct measurement of the rate constant for the dissociation of the alpha-DMB ligand from the Co center (k = (4.6 +/- 0.2) x 10(-2) s(-1), DeltaH = 93 +/- 2 kJ mol(-1), DeltaS = +41 +/- 6 J K(-1) mol(-1)). The beta-axial 5'-deoxyadenosyl ligand (beta-Ado) on coenzyme B(12) is bound more weakly by a second CB[7] host (K(CB[7]) = (1.1 +/- 0.2) x 10(3) dm(3) mol(-1)), however inclusion of the beta-Ado ligand has no effect on the kinetics of its heterolytic photodissociation from the Co(III) center.

Examination of Cucurbit[7]uril and Its Host−Guest Complexes by Diffusion Nuclear Magnetic Resonance

The self-diffusion of cucurbit[7]uril (CB[7]) and its host-guest complexes in D2O has been examined using pulsed gradient spin-echo nuclear magnetic resonance spectroscopy. CB[7] diffuses freely at a concentration of 2 mM with a diffusion coefficient (D) of 3.07 x 10(-10) m(2) s(-1). At saturation (3.7 mM), CB[7] diffuses more slowly (D = 2.82 x 10(-10) m(2) s(-1)) indicating that it partially self-associates. At concentrations between 2 and 200 mM, CsCl has no effect on the diffusion coefficient of CB[7] (1 mM). Conversely, CB[7] (2 mM) significantly affects the diffusion of 133Cs+ (1 mM), decreasing its diffusion coefficient from 1.86 to 0.83 x 10(-9) m(2) s(-1). Similar changes in the rate of diffusion of other alkali earth metal cations are observed upon the addition of CB[7]. The diffusion coefficient of 23Na+ changes from 1.26 to 0.90 x 10(-9) m(2) s(-1) and 7Li+ changes from 3.40 to 3.07 x 10(-9) m(2) s(-1). In most cases, encapsulation of a variety of inorganic and organic guests within CB[7] decreases their rates of diffusion in D2O. For instance, the diffusion coefficient of the dinuclear platinum complex trans-[[PtCl(NH3)2}2mu-dpzm](2+) (where dpzm is 4,4'-dipyrazolylmethane) decreases from 4.88 to 2.95 x 10(-10) m(2) s(-1) upon encapsulation with an equimolar concentration of CB[7].

Dynamic Switching between Single- and Double-Axial Rotaxanes Manipulated by Charge and Bulkiness of Axle Termini

Twin-axial [3]pseudorotaxanes, in which two multicharged axles simultaneously thread through the gamma-CD cavity, were formed for the first time in solution. The twin-axial [3]pseudorotaxane was converted exclusively to a CB [6]-stoppered [4]pseudorotaxane by the addition of CB[6] but regenerated from the [4]pseudorotaxane by the addition of spermine, implementing an unprecedented switching of single/twin-axial rotaxanation.

Refolding Foldamers: Triazene-Arylene Oligomers That Change Shape with Chemical Stimuli

We describe the preparation of five triazene-arylene oligomers (3, 4, 7, 8, and 11) and investigations of their folding properties in aqueous solution. These oligomers contain four 2-fold rotors and populate a conformational ensemble comprising at least 10 states. Extensive 1D and 2D NMR studies as well as X-ray crystallography establish that the presence of three members of the cucurbit[n]uril family (CB[n]), CB[10], CB[7], and CB[8], results in the selective population of the (a,a,a,a)-, (a,s,s,a)-, and (a,a,a,s)-conformers. As a result of the high affinity and highly selective binding properties of the CB[n] family, it is possible to fold a single foldamer strand (3) into the CB[8].(a,a,a,s)-3 conformer by the addition of CB[8], then unfold and refold it into the CB[7].(a,s,s,a)-3.CB[7] conformer by addition of CB[7] and 3,5-dimethylaminoadamantane (17), then unfold and refold it again into the CB[10].(a,a,a,a)-3 conformer by addition of CB[10].CB[5] and aminoadamantane (18). The transformation of CB[8].(a,a,a,s)-3 into CB[7].(a,s,s,a)-3.CB[7] proceeds through the intermediacy of CB [8].(a,a,s,a)-3.CB[7], which enhances the rate of dissociation of strand 3 from CB[8].

The Nucleation Effect of Grafted Carbon Black on Crystallization of Poly(Ethylene Terephthalate)/Grafted Carbon Black Composite

Poly(ethylene terephthalate)/grafted carbon black (PET/GCB) and poly(ethylene terephthalate)/carbon black (PET/CB) composites were prepared by melt blending. The nucleating effect of CB and GCB were investigated using differential scanning calorimetry (DSC) analysis. The morphologies of the spherulites in PET, PET/CB and PET/GCB composites were observed by means of scanning electron microscopy (SEM). All results showed that GCB had higher nucleating activity than CB in PET and PET/GCB composite had higher rate of nucleation and crystallization. The melting behaviors of neat PET, PET/CB and PET/GCB composites after non‐isothermal crystallization were investigated as well. It was evident that the melting behavior of PET is greatly influenced by addition of CB and GCB.

Influence of Carbon‐Black Nanoparticles on Poly(butylene terephthalate) Fractionated Crystallization in Bicomponent Poly(butylene terephthalate)/Poly[ethylene‐co‐(ethyl acrylate)] Blends

AbstractSummary: The crystallization of the PBT minor phase in an EEA continuous matrix has been studied by DSC and SEM. When PBT is the minor phase, PBT crystallizes at a lower temperature, as expected, near Tc,f1 = 105 °C. Introducing different CB nanoparticles into the EEA continuous phase at contents increasing from 0.02 to 5 wt.‐% leads to important modifications of the PBT crystallization. A new PBT exotherm appears at Tc,f2 = 144 °C on the addition of CB, becoming really visible at Tc,f3 = 158 °C and finally moving to Tc,n = 185 °C at high content. The areas corresponding to these new peaks were found to increase to the detriment of that of the fractionated crystallization at Tc,f1 = 105 °C. Morphological studies and interfacial tension measurements were made to understand the surprising activity of the CB. Moreover, the substitution of the EEA phase with the less polar LLDPE confirmed the importance of the strong interactions developed by EEA with CB aggregates.Melting and recrystallization DSC curves for the PBT/EEA 60/40 blend.magnified imageMelting and recrystallization DSC curves for the PBT/EEA 60/40 blend.

Anisotropy in the electrical behavior of immiscible polypropylene/nylon/carbon black blends processed slightly below the melting temperature of the nylon

AbstractCarbon black (CB) containing polypropylene/nylon (PP/Ny) blends, processed slightly below the melting temperature (Tm) of the dispersed Ny phase, leads to formation of fibrillar Ny phase and electrically anisotropic systems. CB containing PP/Ny blends were compounded (twin screw extruder) and processed (injection molding) slightly below the Tm of dispersed Ny phase at different blending sequences. To establish structure–property relationships scanning electron microscopy, high resolution scanning electron microscopy, differential scanning calorimeter were used and electrical properties were also studied. Addition of CB to binary PP/Ny blends, processed below the Ny Tm, altered the Ny fibrillation process forming an irregular continuous phase, containing the CB particles, rather than the fibrils formed in the PP/Ny blends. Yet, upon changing the processing sequence, i.e., compounding PP and CB and then adding Ny in the injection molding stage, Ny fibrils were attained, maintaining phase continuity, oriented in the flow direction and CB particles preferentially located on their surfaces. Blends exhibiting a fibrillar Ny network covered by CB particles exhibited electrical anisotropy. The Ny fibrils exhibited an additional higher crystalline melting peak and molecular orientation. The composites are conductive in the Ny fibril direction, while insulating in the perpendicular direction. Once the CB is located within both, the Ny and the PP matrix the electrical behavior is isotropic. POLYM. ENG. SCI., 46:1250–1262, 2006. © 2006 Society of Plastics Engineers

Fluorescence investigation of affinity interaction between bovine serum albumin and triazine dye in reversed micelles.

The effect of Cibacron Blue 3GA (CB) on the fluorescence emission spectra of bovine serum albumin (BSA) was investigated in cationic reversed micelles formed with cetyltrimethylammonium bromide (CTAB) compared with that in aqueous phase. The anionic CB had electrostatic interactions with cationic CTAB and affinity interactions with BSA in the reversed micelles. The addition of CB in the reversed micellar phase led to a great decrease in the fluorescence intensity of BSA and a remarkable red shift of the wavelength of emission maximum (lambda(max)). The fluorescence intensity of BSA decreased and the lambda(max) decreased 5 nm (blue shift) without the addition of CB in the reversed micellar phase. The fluorescence intensity of BSA with the addition of CB had the strongest value in the aqueous phase with the presence of CTAB, a less strong value in the reversed micellar phase, and a weak value in the aqueous phase without the presence of CTAB. The increase in lambda(max) of BSA with the addition of CB in the reversed micellar phase might indicate the decrease in the hydrophobic microenvironment of the Trp residue of BSA, contrary to those microenvironments in the absence of CB.

Effect of Cibacron Blue and Bovine Serum Albumin on Electrical Conductivity of Reversed Micelles

The effect of Cibacron Blue 3GA (CB) and bovine serum albumin (BSA) as guest molecules on the microstructure of reversed micelles has been investigated with electrical conductivity measurements. CB as an affinity ligand was directly introduced to reversed micelles formed with a cationic surfactant, cetyltrimethylammonium bromide. The anionic CB has electrostatic interactions with the cationic surfactant and also has a strong binding affinity to BSA. The conductivity of reversed micellar systems increases gradually with the increase of temperature either with or without the addition of CB. The conductivity of reversed micellar systems increases with the addition of tributyl phosphate to the organic phase. No electrical percolation appears with an increase of temperature or water concentration. The conductivity of reversed micellar systems decreases with the addition of CB and decreases further with the addition of both CB and BSA. The conductivity of the organic phase is 3 orders of magnitude lower than that of the aqueous phase under the same CB concentration, which indicates that CB is probably confined to the closed microdomains of reversed micellar systems. The conductivity behavior of reversed micelles has not shown much difference with the methods used for the addition of CB either by the injection method or by phase transfer.

Effect of triazine dye on electrical conductivity and extraction of bovine serum albumin in reversed micelles formed with cetyltrimethylammonium bromide

The effect of Cibacron Blue 3GA (CB) and bovine serum albumin (BSA) as guest molecules on the microstructure of reversed micelles has been investigated with electrical conductivity measurements. CB as an affinity ligand was directly introduced to reversed micelles formed with cationic surfactant, cetyltrimethylammonium bromide (CTAB). The anionic CB has electrostatic interactions with cationic surfactant and has affinity interaction with BSA. The conductivity of reversed micellar systems increases gradually with the increase of temperature either with or without the addition of CB. No electrical percolation appears with increase of temperature or water concentration. The conductivity of reversed micellar systems decreases with the addition of CB and decreases further with the addition of both CB and BSA. The conductivity of organic phase is three orders of magnitude lower than that of aqueous phase under the same CB concentration, which indicates that CB is probably confined to the closed microdomains of reversed micellar systems. The conductivity behavior of reversed micelles has not much difference with the addition of CB and BSA either by injection method or by phase transfer. For pH<p I, reversed micelles containing no CB solubilize no BSA due to electrostatic repulsion by phase transfer method. The enhancement of BSA transfer to the reversed micelles with addition of affinity CB indicates a strong interaction between the extracted BSA and the reversed micellar phase. The improvement of selectivity should be expected with the presence of biospecific CB because the affinity interaction is the unique driving force for BSA transfer.

Affinity-Based Reversed Micellar Bovine Serum Albumin (BSA) Extraction with Unbound Reactive Dye

A quick and simple method has been introduced for affinity extraction with an unbound reactive dye in a reversed micellar system. Bovine serum albumin (BSA) and Cibacron Blue 3GA (CB) were chosen, respectively, as a model protein and an unbound ligand. CB in the aqueous phase was directly transferred to the reversed micelles due to electrostatic interaction between anionic CB and cationic cetyltrimethylammonium bromide. The BSA transfer to the reversed micelles increases significantly by affinity interaction with the addition of a small amount of CB to the aqueous phase. For solutions with pH close to pI, the selectivity of proteins can be expected in the presence of affinity CB as very little BSA is extracted into the reverse micelles without the addition of CB. Most of the BSA (∼82%) extracted into the reversed micelles can be backextracted into the stripping aqueous phase by increasing of n-hexanol concentration in the organic phase while no CB is transferred to the aqueous solution at the same time.

Affinity extraction of BSA by mixed reversed micellar system with unbound triazine dye

The affinity extraction of proteins with unbound triazine dye in the mixed reversed micellar system has been studied. Bovine serum albumin (BSA) and Cibacron Blue 3GA (CB) were chosen, respectively, as a model protein and an unbound ligand. The affinity CB in the aqueous phase was directly transferred to the mixed reversed micelles formed with cationic surfactant cetyltrimethylammonium bromide (CTAB) and tributyl phosphate (TBP). The transfer of BSA to the reversed micelles increases significantly by the biospecific interaction with the addition of a small amount of CB to the aqueous phase. For solutions with pH < p I, the selectivity of proteins can be expected with the presence of affinity CB since no BSA was found to be extracted into the reverse micelles without the addition of CB. The BSA transfer to the reversed micelles increases significantly by the addition of TBP to the organic phase. Most of BSA (∼82%) extracted into the reversed micelles can be back extracted into the aqueous phase by the increase of n-hexanol concentration in the organic phase while no CB would be transferred into the stripping aqueous solution at the same time.

Determination of Protein Solubility in Oilseed Meals Using Coomassie Blue Dye Binding

Protein solubility in KOH has been shown to be a good indicator for overprocessing of oilseed meals. However, the conventional method requires determination of N, usually by the Kjeldahl method, which is time consuming and expensive. The current study evaluated the use of Coomassie blue dye (CB) to reduce the time and expense of conducting the protein solubility assay for different oilseed meals. Samples of solvent-extracted soybean meal, canola meal, and sunflower meal were autoclaved for 0 to 120 min at 121 C and 124 kPa. Protein solubility, in .2% KOH for soybean meal and sunflower meal and in .5% KOH for canola meal, was determined using Kjeldahl N or CB. In the CB assay, an aliquot of the soluble protein solution was mixed with CB and absorbance measured at 595 nm. Protein solubility decreased as autoclaving time increased for all oilseed meals, with the response being greatest for SBM. The results indicated that time after addition of CB to the soluble protein solution affected dye binding values and that spectrophotometer readings should be made within 1 min after mixing the CB with the soluble protein. It was also necessary to prepare a standard curve of dye binding versus soluble protein for each individual oilseed meal, because the amount of dye bound per unit of protein and the linear range in dye binding values varied among the oilseeds. Overall, protein solubility values determined by the Kjeldahl N method and the CB method were in very good agreement (r = .99).

Ultrastructure of 2-Bromergocryptine-Treated Human Prolactin-Secreting Microadenomas in Culture

Speculation concerning the mechanism by which 2-bromoergocryptine (CB 154) acts to decrease serum prolactin (PRL) levels has revolved around two basic hypotheses; one concerning the importance of primary hypothalamic effects; the other emphasizing direct hypophyseal effects. The potential for hypothalamic effects were reduced in these experiments by explanting PRL-secreting microadenomas in organ culture and short term monolayer tissue culture. Tissue was obtained immediately from the operating room from 6 patients operated on by the transphenoidal approach. Cultures were maintained in Ham's F12 Nutrient Medium, 90% by volume with 10% fetal calf serum. CB 154 was added at concentrations of 0, 0.5, or 5.0μg/ml. The organ cultures were maintained for 24 hours before the addition of CB 154 and then for 24 to 48 hours in the presence of inhibitor after which specimens were fixed at 4°C with 4% glutaraldehyde, 0.1M. Cacodylate, pH 7.2, and post-fixed with 1% osmium tetroxide.

Grain-boundary carbide precipitation during tempering of austenitic steel

1. Carbide precipitation in the steel studied during tempering was obstructed by a decrease of the carbon content from 0.09\2-0.12% to 0.04 and also by addition of Mo, Cb and Ta. The resistance to intercrystalline corrosion in a standard solution test was preserved in the low-carbon steel and in one containing tantalum (Ta:C=20:1). Additions of W and an increased Cb content (in excess of 10 times the carbon content) resulted in ferrite formation. 2. Beryllium accelerated carbide precipitation during tempering of a quenched steel; Ca, Ag and Ce within the limits studied had no effect on this process. 3. Between 0.003 and 0.10% B hampered carbide formation during tempering at 650\dgC but increased the tendency to carbide network formation at higher temperatures. The effect of boron depended on the quenching temperature and the carbon content of the steel.

異方性MK磁石の研究(I)

The MK permanent magnet Fe-Ni-Al ternary aloy was invented by Tokushichi Mishima (one of authors) in 1930. Since then the magnetic properties of this alloy underwent no mprovement to a remarkable degree for sometime. During the 2nd World War, it was disgovered that MK magnet containing the certain restricted range of comnosition could attain to excellent magnetic properties by the heat-treatment in magnetic field.In our country, the investigation of the magnetic treatment of MK magnet was kept on for a long time in Mishima's laboratory in University of Tokyo. In this report, the results of such investigation on the effects of chemical composition and additional elements on the magnetic properties of this anisotropic Mk magnet alloy will be described. The experimental results on the heat-treatment and industrial aspects mav be reported later. Briefly this report may be summarized as follows:According to the increase of Ni content up to 17%, the coercive force is improved, but the residual induction be omes inferior. Increase of Co content up to 28% is preferable for the residual induction, but its content is relative to Ni content and it is desirable to restrict the total content of Ni and Co to 38 or 39%. The magnetic properties is sensitive to Al content. The optimum composition is 7.8-8.4% and unfavourable effects become marked when Al contents reach to less than 7%. The optimum chemical composition of Al needs to be changed according to the additional Si and Ti contents. C content has to be kept under 0.05%, because it is apt to cause a remarkable deterioration of the magnetic properties. Addition of Ti is effective in overcoming its undesirable effects. As Si, Mn and P ill-effect on the magnetic properties, it is advisable that Si, Mn and P contents should be kept respectively lower than 0.2%, 0.3% and 0.02%. Addition of Cb and Zr is favourable to the magnetic properties, especially Cb is effective to improve the coercive force. The effects of other additional elements: B, Cr, W, Mo, V, Be and Sn, is unpreferable to the magnetic properties.