Cytotoxicity of asymmetric platinum complexes against L-1210 cells. Effect of bulky substituents

The asymmetric platinum complexes cis-Pt(LL')Cl2 (L = NH3, L' = CH3NH2, (CH3)2NH, C2H5NH2 and (C2H5)2NH and LL' = N,N-dimethylethylenediamine),--one of the NH3 groups of cis-Pt(NH3)2Cl2 was substituted by alkylamine--, were synthesized and their cytotoxic effects have been measured using L-1210 cells. The IC50 values of the asymmetric platinum complexes,--being obtained after 24 h exposure of L-1210 cells to the platinum complexes--, are almost comparable to the corresponding value of cis-Pt(NH3)2Cl2. In 2 h exposure, however, the IC50 values of the platinum complexes were dramatically changed, i.e., a marked difference was observed between those of L' = RNH2 and L' = R2NH. On the other hand, the amounts of platinum taken into the L-1210 cells is little affected by the alkylamino substitution. The results suggest that the bifunctional platinum binding to the target molecule may be responsible for the cytotoxicity.     

Sugar-sensitive thin films composed of concanavalin A and sugar-bearing polymers.

Layered thin films composed of concanavalin A (Con A) and sugar-bearing polymers were prepared by a layer-by-layer deposition of Con A and the polymer on a solid surface. The sugar-induced disintegration was studied. Con A-polymer layered films could be successfully prepared using a maltose-bearing polymer (PV-MA), while melibiose- and glucose-bearing polymers (PV-MEA and PV-G) did not afford a layered film, due to a weak affinity of PV-MEA and PV-G to Con A. The Con A/PV-MA layered film was stable in pH 7 and 8 solutions, while in a pH 6 medium the film was slightly unstable. The Con A/PV-MA film was disintegrated upon the addition of sugars in solution owing to a preferential binding of the sugars to the binding site of Con A in the film. The disintegration rate was dependent on the type of sugar and its concentration. The Con A/PV-MA film was disintegrated rapidly upon the addition of methyl alpha-D-mannopyranoside, while the rate was slower upon the addition of the same concentration of D-mannose, D-glucose and methyl alpha-D-glucopyranoside. The present system may be useful for constructing sensitive devices that can release a drug or other functional molecules in response to sugars.     

Elementary reaction analysis of the radical polymerization of α‐ethyl β‐N‐(α′‐methylbenzyl)itaconamates carrying (RS)‐ and (S)‐α‐methylbenzylaminocarbonyl groups

The polymerizations of α‐ethyl β‐N‐(α′‐methylbenzyl)itaconamates carrying (RS)‐ and (S)‐α‐methylbenzylaminocarbonyl groups (RS‐EMBI and S‐EMBI) with dimethyl 2,2′‐azobisisobutyrate (MAIB) were studied in methanol (MeOH) and in benzene kinetically and with electron spin resonance (ESR) spectroscopy. The initial polymerization rate (R_p) at 60 °C was given by R_p = k[MAIB]^{0.58 ± 0.05}[RS‐EMBI]^{2.4 ± 0.l} and R_p = k[MAIB]^{0.61 ± 0.05}[S‐EMBI]^{2.3 ± 0.l} in MeOH and R_p = k[MAIB]^{0.54 ± 0.05}[RS‐EMBI]^{1.7 ± 0.l} in benzene. The rate constants of initiation (k_df), propagation (k_p), and termination (k_t) as elementary reactions were estimated by ESR, where k_d is the rate constant of MAIB decomposition and f is the initiator efficiency. The k_p values of RS‐EMBI (0.50–1.27 L/mol s) and S‐EMBI (0.42–1.32 L/mol s) in MeOH increased with increasing monomer concentrations, whereas the k_t values (0.20?7.78 × 10⁵ L/mol s for RS‐EMBI and 0.18?6.27 × 10⁵ L/mol s for S‐EMBI) decreased with increasing monomer concentrations. Such relations of R_p with k_p and k_t were responsible for the unusually high dependence of R_p on the monomer concentration. The activation energies of the elementary reactions were also determined from the values of k_df, k_p, and k_t at different temperatures. R_p and k_p of RS‐EMBI and S‐EMBI in benzene were considerably higher than those in MeOH. R_p of RS‐EMBI was somewhat higher than that of S‐EMBI in both MeOH and benzene. Such effects of the kinds of solvents and monomers on R_p were explicable in terms of the different monomer associations, as analyzed by ¹H NMR. The copolymerization of RS‐EMBI with styrene was examined at 60 °C in benzene. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1819–1830, 2003     

Development of micromarkers with various photoluminescence colors as tracers for shadowing pursuits.

Micromarkers with five photoluminescence colors were developed as tracers for shadowing pursuits. The markers are colorless powders with particle diameters of several tens to several hundreds of micrometers, prepared using a cryogenic sample crusher. They were visualized using red, green, yellow, magenta or cyan photoluminescence under ultraviolet light at approximately 365 nm. The markers were composed of photoluminescent compounds dispersed in polyvinyl butyral. The photoluminescent compounds in the polyvinyl butyral were stable under ambient conditions for more than one year after application. The compounds with the red, green, yellow, magenta and cyan photoluminescence contained a europium (Eu(3+)) complex, a terbium (Tb(3+)) complex, a mixture of Tb(3+) and Eu(3+) complexes, a mixture of Eu(3+) complex and o-coumaric acid, and a mixture of Tb(3+) complex and 7-hydroxycoumarin along with a few drops of a sodium bicarbonate aqueous solution, respectively. Neodymium (Nd(3+)) and ytterbium (Yb(3+)) complexes with photoluminescence in the near-IR wavelength region can also be added to these visible photoluminescent compounds as secret markers for discrimination. The markers were non-destructively identified using a microscopic FT-IR spectrometer and a microscopic spectrometer equipped with a fluorescence detector.     

Sound attenuation in one-dimensional magnetic systems at finite temperatures

Sound attenuattion constants are calculated for the one-dimensional ferro- and antiferromagnetic systems at finite temperatures. Their frequency dependences, in both cases, turn out to be $\text{ω}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}{}_{\mathrm{<mtext>k</mtext>}}\text{if}\text{ω}{}_{\mathrm{<mtext>k</mtext>}}\text{? ω}{}_{\mathrm{c}}\text{and}\text{ω}{}^2{}_{\mathrm{<mtext>k</mtext>}}\text{if}\text{ω}{}_{\mathrm{<mtext>k</mtext>}}\text{?ω}{}_{\mathrm{c}}$, where ω_c is a “cut-off” frequency related to the three-dimensional anisotropic interactions.     

Lifetime distribution and estimation problems of consecutive-k-out-of-n:F systems

Explicit formula is given for the lifetime distribution of a consecutive-k-out-of-n:F system. It is given as a linear combination of distributions of order statistics of the lifetimes of n components. We assume that the lifetimes are independent and identically distributed. The results should make it possible to treat the parametric estimation problems based on the observations of the lifetimes of the system. In fact, we take up, as some examples, the cases where the lifetimes of the components follow the exponential, the Weibull, and the Pareto distributions, and obtain feasible estimators by moment method. In particular, it is shown that the moment estimator is quite good for the exponential case in the sense that the asymptotic efficiency is close to one.This research was partially supported by the ISM Cooperative Research Program (94-ISM-CRP-5).     

Estimation of parameters in the discrete distributions of order k

This paper considers estimating parameters in the discrete distributions of order k such as the binomial, the geometric, the Poisson and the logarithmic series distributions of order k. It is discussed how to calculate maximum likelihood estimates of parameters of the distributions based on independent observations. Further, asymptotic properties of estimators by the method of moments are investigated. In some cases, it is found that the values of asymptotic efficiency of the moment estimators are surprisingly close to one.