A novel urocanic acid derivative from skin tissue extracts; (E)-3-[1-(1,1-dimethyl-3-oxobutyl)imidazol-4-yl]propenoic acid

A novel derivative of urocanic acid ( 1 ) had been isolated from acetone extracts of rabbit skin tissue. It proved to be (E)-3-[1-(1,1-dimethyl-3-oxobutyl)imidazol-4-yl]propenoic acid ( 3c ), potentially a much better ultraviolet screening agent than urocanic acid. Sterical effect of dimethyl groups in the side chain adjacent to the imidazole ring of 3c on its solubility is also discussed.     

Selective separation of flavonoids with a polyvinyl alcohol membrane

In order to develop a selective membrane separation process for flavonoids, i.e. baicalin, baicalein and flavone extracted from a crude drug, “Wogon”, we have measured the permeabilities of these flavonoids through a polyvinyl alcohol membrane, together with their aqueous solubilities. The aqueous solubilities of baicalin and baicalein increase with increasing aqueous solution pH due to the acid dissociation of the saccharic carboxyl group of baicalin or the phenolic hydroxyl group of baicalein. The mass transfer coefficients of flavonoids experimentally obtained in both systems of single and mixed constituents agreed well with the calculated values based on a solution-diffusion model together with the acid dissociation of the carboxyl or hydroxyl groups of baicalin and baicalein, respectively. The selective mutual separation of flavonoids can be achieved from mixed solution of constituents in the neutral pH region. Furthermore, a quantitative discussion of the permeation behavior of flavonoids through the PVA membrane is provided from a molecular modelling computational viewpoint.     

Evaluation of concanavalin A-mannose interaction on the electrode covered with collagen film

An electrode covered with a lectin/collagen film was constructed to investigate whether the film was usable as a reaction field of binding between the lectin and sugar. The protein-sugar binding on cell surface plays an important role to various physiologic processes. The film is considered to be a cell surface, due to its biocompatibility. The immobilization of concanavalin A (Con A) which is one of proteins was attempted by an electrostatic interaction of the protonated functional groups of film to the negative charged Con A. The merit of this immobilization is that the interaction hardly causes any changes in the protein structure. Because Con A recognizes mannose moiety, the mannose was labeled with an electroactive compound. The binding was estimated from the changes of the electrode response based on the holding of electroactive moiety in the binding site of Con A to the mannose moiety. However, the electrode responses of glucose and galactose labeled with the same substance did not change. The result shows that Con A is immobilized on the film and combines with labeled mannose. Therefore, it is clear that the collagen film is suitable as the reaction field to evaluate the protein-sugar binding.     

Reaction of trist(trifluoromethyl)cyclopropenyl trifluoromethyl ketone with azo compounds in the presence of triphenylphosphine,and synthesis of tetrakis(trifluoromethyl)pyridazine.

The title cyclopropenylketone reacts with azo compounds and tri-phenylphosphine to give unique heterocycles; tricyclourazoles and a diazaoxacyclooctatriene. The formers were converted into a pyridazine.     

Dielectric study of low-temperature relaxations in poly(isobutyl methacrylate), poly(n-butyl methacrylate), poly(isopropyl methacrylate), and poly(4-methylpentene-1)

Isochronal measurements of dielectric constant and loss are made for poly(isobutyl methacrylate) (PiBMA), poly(n-butyl methacrylate) (PnBMA), poly(isopropyl methacrylate) (PiBMA), and poly(4-methylpentene-1) (P4MP1) at temperatures ranging from 4°K to 250°K. Loss peaks are found around 120°K (10–100 Hz) for PiBMA, PnBMA, and P4MP1. By comparing the activation energy with the calculated potential barrier for the internal rotation of alkyl group in the side chain, the motion responsible for the 120°K peak is concluded to be essentially the rotation of the isopropyl group as a whole for PiBMA and P4MP1 but, for PnBMA, the rotation of n-propyl group accompanied by the rotation of the end ethyl group. Multiple paths of internal rotation are involved with the 120°K peaks of PiBMA and, in particular, PnBMA, which explain differences between PiBMA and PnBMA in the broadness and the temperature location of the 120°K peak. The 120°K peak is in general assigned to a side chain including a sequence? O? C? C? C or ? C? C? C? C. PiPMA without this sequence in the side chain does not show the 120°K peak, but it exhibits the 50°K peak (1 kHz) like poly(ethyl methacrylate). The 50°K peak is assigned to the rotation of ethyl or isopropyl group attached to COO group. Poly-L-valine in which the isopropyl group is directly attached to carbon does not have the 50°K peak. An additional loss peak at 20°K (1 kHz) for P4MP1 is also discussed on the basis of the calculated potential.     

Higher Dimensional Rotating Black Hole Solutions in Quadratic f(R) Gravitational Theory and the Conserved Quantities

We explore the quadratic form of the f(R)=R+bR2 gravitational theory to derive rotating N-dimensions black hole solutions with ai,i≥1 rotation parameters. Here, R is the Ricci scalar and b is the dimensional parameter. We assumed that the N-dimensional spacetime is static and it has flat horizons with a zero curvature boundary. We investigated the physics of black holes by calculating the relations of physical quantities such as the horizon radius and mass. We also demonstrate that, in the four-dimensional case, the higher-order curvature does not contribute to the black hole, i.e., black hole does not depend on the dimensional parameter b, whereas, in the case of N>4, it depends on parameter b, owing to the contribution of the correction R2 term. We analyze the conserved quantities, energy, and angular-momentum, of black hole solutions by applying the relocalization method. Additionally, we calculate the thermodynamic quantities, such as temperature and entropy, and examine the stability of black hole solutions locally and show that they have thermodynamic stability. Moreover, the calculations of entropy put a constraint on the parameter b to be b<116Λ to obtain a positive entropy.     

Dielectric relaxations in polymers with pendent phenyl or pyridine groups at temperatures from 4°K to 80°K

Isochronal measurements of dielectric loss are made for polystyrene (PS), poly(4-vinyl pyridine) (P4VP), poly(2-vinyl pyridine) (P2VP), poly(L-phenylalanine) (PLPA), and poly(γ-benzyl-L-glutamate) (PBLG) at temperatures ranging from 4°K to 80°K and at frequencies from 10 Hz to 100 kHz. PS, P4VP, and PLPA show loss peaks around 50°K (10 kHz) while P2VP exhibits a loss peak around 20°K (10 kHz). PBLG has no detectable peak in this temperature range. The 50°K and 20°K peaks are ascribed to wagging and rotation, respectively, of phenyl or pyridine groups between two energy minima. The barrier height and energy difference between the minima evaluated from the experimental data are reasonably explained by assuming that the double minima are caused by interaction between a pair of phenyl or pyridine groups, each belonging to adjacent chains which pack irregularly.     

Microdroplet anodic stripping voltammetry at the in situ preparing antimony-modified rotating disk electrode for determination of Cd(II) and Pb(II)

A simple electroanalytical method for Cd(II) and Pb(II) detection based on differential pulse anodic stripping voltammetry (DPSV) with in situ prepared antimony-modified glassy carbon rotating disk electrode (in situ Sb-GC-RDE) was developed. The electrochemical detection was performed in a microdroplet (50 μL) of 0.01 M hydrochloric acid that is placed between the electrode surface (top) and a Parafilm®-covered glass slide to maintain a hydrophobic surface (bottom). This method includes a preconcentration process using a membrane filter (MF). The target metal ions were complexed with 1-(2-pyridylazo)-2-naphthol (PAN) as a chelating agent, which was accumulated on the MF via filtration. The RDE microdroplet anodic stripping voltammetry was suitable for the elution and determination of metal ions accumulated on the MF. The in situ preparation of antimony-modified electrode allows the use of common GC electrode with high performance. The detection limits for Cd(II) and Pb(II) were 1.4 and 1.1 μg/L, respectively. The proposed method was successfully used in natural water samples for the simultaneous determination of Cd(II) and Pb(II).