Reversible control of enzymatic transglycosylations in supercritical fluoroform using a lipid-coated beta-D-galactosidase

The transgalactosylation rate catalyzed by the lipid-coated beta-d-galactosidase in supercritical fluoroform (scCHF3) can be reversibly controlled by changing temperature or pressure (reflecting polarity changes) without damaging enzymes.     

Selective and Efficient Iodination of the p-Positions of Calix[4]arene Derivatives

Selective and very convenient methods of iodination of calix[4]arenes using ICl or NIS have been demonstrated, preparing mono(p-iodo) and 1,3-di(p-iodo) derivatives of calix[4]arenecrown-4 and -5, as well as mono(p-iodo) derivative of tris(O-propyl)calix[4]arene in good yields.     

Reverse zymography using fluorogenic substrates for protease inhibitor detection

A novel, sensitive method for detecting protease inhibitors by using fluorescent protease substrates in gels is described. The protease inhibitors were separated on sodium dodecyl sulfate (SDS)-polyacrylamide gels containing a copolymerized peptide substrate, namely 4-methyl-coumaryl-7-amide (MCA). As the incorporated substrates in the gel, Boc-Phe Ser-Arg-MCA was used for trypsin, Suc-Ala-Ala-Pro-Phe-MCA for alpha-chymotrypsin, and Z-Phe-Arg-MCA for papain. After electrophoresis, washing and incubating the gel with the target protease solutions allowed the substrate to be cleaved by the protease, and the release of the fluorescent 7 amino-4 methyl-coumarin (AMC), which was detected under a UV transilluminator. The uncleaved peptide-MCA substrate remained where the inhibitors were present, and was visualized as dark blue bands on the light-green fluorescent background gel. This new method offers several advantages over other previous methods including: (i) greatly increased sensitivity can be achieved in a shorter period of time, which may be useful for discovering new protease inhibitors in small amounts of crude material; (ii) the procedure is quite simple and quick since the incubation period is very short and no time is needed for staining and destaining steps; (iii) since these probes using substrate specificity/target proteases, they are excellent tools for detection and discrimination of unknown protease inhibitors for various target proteases.     

Determination of sulfates of androsterone and epiandrosterone in human serum using isotope diluted liquid chromatography-electrospray ionization-mass spectrometry

A promising liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) for analysis of the sulfates of 5alpha-androgen, androsterone and epiandrosterone (A-S and EpiA-S) in human serum was developed. The method was used to assess one of the markers of 5alpha-reductase activity of males including patients with prostate cancer (PC). After deproteinization with acetonitrile, the androgen sulfates and the internal standard, [7,7,16,16-2H4]dehydroepiandrosterone-S, were extracted from human serum using a solid-phase extraction cartridge and washed with hexane. The extract was reconstituted and applied to the LC/ESI-MS system operated in the selected ion monitoring mode. The method was validated over the range 0.02-5 microg/mL (A-S) and 0.005-1.5 microg/mL (EpiA-S) using 10 microL of human serum. The method was a concise procedure without chemical or enzymatic hydrolysis of the conjugates, purification by high-performance liquid chromatography and/or derivatization, and proved to be satisfactory in its reproducibility and accuracy. The levels of these androgen sulfates tended to decrease during aging, and the A-S levels in the sera obtained from both healthy males and patients with PC were correlated with their EpiA-S levels.     

Electronic structures of exohedral lanthanide-C60 clusters

We have studied the electronic structures of several gas phase exohedral lanthanide (Ln)-C(60) clusters, Ln(n)C(60) (Ln=Pr, Ho, Tb, Tm, Eu, and Yb) with n=1-4, by photoionization spectroscopy of the neutrals and photoelectron spectroscopy of their anions. Both of the spectroscopic analyses reveal that most of the Ln atoms preferably take +3 oxidation states, while Eu atoms alone assume +2 oxidation states, and that C(60) accepts up to twelve donated electrons in Ln(n)C(60). An additional photoionization examination of the oxygen atom mixing into the Ln(n)C(60) clusters demonstrated that each oxygen atom reduces two electrons from C(60). This result implies that the number of accepted electrons in C(60) can be varied by a suitable choice of the number of Ln atoms and O atoms.     

The effect of the presence of foreign salts on the formation of gaseous ions for electrospray and laser spray

The effect of the presence of foreign salts (NaCl, aerosol OT, tetra-n-hexylammonium bromide, and CH3COONH4) on the formation of gaseous ions for electrospray (ES) and laser spray (LS) was studied in the positive and negative modes of operations. The ion signals for amino acids show sudden decrease with the concentration of foreign salts greater than 10(-5) M for both ES and LS. When the surface-active counter ions were added, the signal intensities showed a marked decrease for both ES and LS. This may be due to the enrichment of the surface-active counter ions on the surface of the charged droplets. When CH3COONH4 was added to an aqueous solution of 10(-6) M lysozyme chloride, an increase of the signal intensities for (lysozyme+nH)n+ and a decrease in the values of n were observed. The decrease in n may be due to the salt formation of (lysozyme+nH)n+ with the negative acetate ion leading to the reduction of positive charges.     

Thermosensitive poly(methyl methacrylate) emulsion prepared in the presence of poly(vinyl alcohol) with a cloud point as a protective colloid

An emulsion of poly(methyl methacrylate) (PMMA) was prepared using poly(vinyl alcohol) (PVA) of low degree of hydrolysis with a cloud point as a protective colloid. The behaviour of an aqueous solution of PVA with 80% degree of hydrolysis was first investigated in terms of the Huggins constant in viscometry. MMA was polymerized using the PVA at 20 °C, where no abnormality in the aqueous PVA was observed. The change in transmittance of the emulsion observed with a UV–vis photometer revealed that in the case of UV light of wavelength 370 nm, the transmittance decreased markedly at around 30 °C with an increase in temperature, and then increased with a decrease in temperature. The thermosensitive property resulted from PVA with a low degree of hydrolysis with a cloud point, at a higher temperature of which the PVA loses solubility in water owing to weakening of the hydrogen bond between PVA molecules and water.     

A theory of adsorption kinetics with time delay and its application to overshoot and oscillation in the surface tension of gelatin solution

A theory of adsorption kinetics with time delay [Ohshima et al. (1992) Colloid Polym. Sci. 270:707] is developed and applied to the surface tension of a polymer solution. It is found that the general appearance of the overshoot and oscillation in the time course of the surface tension of aqueous gelatin solution observed by Sato and Ueberreiter [(1979) Makromol. Chem. 180:829, 1107; (1979) Polym. Prepr. Am. Chem. Soc. Div. Polym. Chem. 20:907) can be explained by the present theory.     

The hydrophilization of polystyrene substrates by 172-nm vacuum ultraviolet light

This paper describes the photochemical surface modification of polystyrene (PS) substrates using vacuum ultraviolet (VUV) light 172 nm in wavelength. We have particularly focused on the effects of atmospheric pressure during VUV irradiation on the obtained surface's wettability and the stability of the wettability, in addition to its chemical structure, morphology, and photooxidation rate. Samples were photoirradiated with VUV light under pressures of 10, 10(3), or 10(5) Pa. Although, in each case, the originally hydrophobic PS surface became highly hydrophilic, the final water-contact angle and photooxidation rate depended on the atmospheric pressure. The samples treated at 10 Pa were less wettable than those prepared at 10(3) and 10(5) Pa due to the shortage of oxygen molecules in the atmosphere. The minimum water-contact angles of the samples treated at 10, 10(3), and 10(5) Pa were about 8 degrees, 0 degrees, and 0 degrees, respectively. With the samples prepared at 10 and 10(3) Pa, photooxidation reactions proceeded in the topmost region closest to the surface, while at 10(5) Pa photooxidation was found to be greatly enhanced in the deeper regions, as evidenced by angle-resolved X-ray photoelectron spectroscopy. Photoetching rates were determined through atomic force microscope observation of microstructured PS samples prepared by a simple mesh-contact method. As estimated from AFM images of the latticed microstructures obtained, the rates of samples prepared at 10(3) and 10(5) Pa were about 1.5 and 1.3 nm/min, respectively. However, no photoetched features were observable on the sample surface prepared at 10 Pa. Hydrophilic stability also varied greatly depending on atmospheric pressure. The hydrophilicity of samples treated at 10 and 10(3) Pa gradually decreased as they were exposed to air. On the other hand, the sample surface prepared at 10(5) Pa showed excellent hydrophilicity even after being left in air for 30 days.     

Cooperative motions of protein and hydration water molecules: molecular dynamics study of scytalone dehydratase

Two molecular dynamics (MD) simulations totaling 25 ns of simulation time of monomeric scytalone dehydratase (SD) were performed. The enzyme has a ligand-binding pocket containing a cone-shaped alpha+beta barrel, and the C-terminal region covers the binding pocket. Our simulations clarified the difference in protein dynamics and conformation between the liganded protein and the unliganded protein. The liganded protein held the ligand molecule tightly and the initial structure was maintained during the simulation. The unliganded protein, on the other hand, fluctuated dynamically and its structure changed largely from the initial structure. In the equilibrium state, the binding pocket was fully solvated by opening of the C-terminal region, and the protein dynamics was connected with hydration water molecules entry into and release from the binding pocket. In addition, the cooperative motions of the unliganded protein and the hydration water molecules produced the path through the protein interior for ligand binding.