Quasi-one-dimensional molecular magnets based on derivatives of (fluorobenzyl)pyridinium with the [M(mnt)2] monoanion (M = Ni, Pd or Pt; mnt2- = maleonitriledithiolate): syntheses, crystal structures and magnetic properties.

The syntheses, structural characterizations and magnetic behaviors of three new complexes, 1-(3',4',5'-trifluorobenzyl)pyridinium [M(mnt)2]- [M = Ni (1), Pd (2) or Pt (3)], are reported. These complexes are isomorphous and their prominent structural character is that the [M(mnt)2]- anions form columnar stacks, in which the dimerization was observed. Complexes 2 and 3 are diamagnetic, while 1 possesses an energy gap of 2474 K. For crystal 4, 1-(4'-fluorobenzyl)pyridinium [Ni(mnt)2] (its structure and magnetic susceptibility were briefly reported earlier), the magnetic behavior can be divided into two regimes, namely, weakly ferromagnetic coupling above 93 K and strongly antiferromagnetic coupling below 93 K. A transition occurs at 93 K which switches the magnetic exchange nature from ferromagnetic to antiferromagnetic. A sharp thermal abnormality with lambda-shape, associated with the transition, appears from its heat capacity measurement to indicate that the transition is first order. The temperature dependences of the superlattice diffractions revealed the existence of the pretransitional phenomena up to at least 140 K. The unusual magnetic behavior of 4, such as the origin of the ferromagnetic interaction in the high temperature phase and what causes the spin transition, are discussed further.

Structural and magnetic investigations for the doping effect of nonmagnetic impurity on the spin-Peierls-like transition in a quasi-one-dimensional magnet: 1-(4'-nitrobenzyl)pyridinium bis(maleonitriledithiolato)nickelate.

A nonmagnetic compound, [NO(2)BzPy][Au(mnt)(2)] (NO(2)BzPy(+) = 1-(4'-nitrobenzyl)pyridinium; mnt(2-) = maleonitriledithiolate), was synthesized and characterized structurally, which is isostructural with [NO(2)BzPy][Ni(mnt)(2)] that is a quasi-one-dimensional magnet and possesses a spin-Peierls-like transition with J = 192 K in the gapless state and spin energy gap = 738 K in the dimerization state, respectively. Further, ten nonmagnetic impurity doped compounds with a formula [NO(2)BzPy][Au(x)Ni(1-x)(mnt)(2)] (x = 0.01-0.73) were prepared and investigated by crystal structural determinations and magnetic susceptibility measurements. The nonmagnetic doping causes the suppression of the spin transition with an average rate of 221(12) K/percentage of dopant concentration. From the plots of chi(m)-T, the transition collapse (the characteristic of the transition is the sudden drop of chi(m) upon cooling, and the disappearance of this characteristic is considered as the criterion for the transition collapse) is estimated at around x > 0.27. In heavier doped system x = 0.49, the spin gap vanishes and a gapless phase is achieved again.

Design of a magnetic bistability molecular system constructed by H-bonding and pi...pi-stacking interactions.

Crystal structures and magnetic properties were determined for two novel polymorphs of the complex [H2DABCO][Ni(mnt)2] [(H2DABCO)2+ = diprotonated 1,4-diazabicyclo[2.2.2]octane; mnt2- = maleonitriledithiolate]. For each polymorph, anions form a layered structure in which two kinds of dimers were observed. The adjacent anionic sheets are held together by cations via H-bonding interactions between protons of cations and CN groups of anions. Two polymorphs possess spin bistability; namely, upon cooling, a magnetic transition happens at around 120 K with about 1 K hysteresis on heating for the alpha phase and at 112 K with about 10 K hysteresis for the beta phase. Above the transition, the magnetic behaviors of two polymorphs can be approximately interpreted by a singlet-triplet model of an antiferromagnetically coupled S = 1/2 dimer, which is supported by the crystal structures and spin dimer analyses based on extended Hückel molecular orbital calculations.

[Preliminary screening for antiviral AIDS drugs. VIII. Report for fiscal year 1995].

Preliminary screening of antiviral AIDS drugs has been carried out using three different in vitro assay systems. Among 96 samples of different origin tested, two were shown to inhibit the growth of HIV in vitro. One of the positive samples (plant origin) has hopeful signs, as the ranges of effective doses are wider than those of most of positive samples which had been found by us.

[Preliminary screening for antiviral AIDS drugs. VI. Report for fiscal year 1993].

Preliminary screening of antiviral AIDS drugs has been carried out using three different in vitro assay systems. Among 138 samples tested, two were found to inhibit the growth of HIV in vitro. Neither of the positive samples has hopeful signs, as the ranges of effective doses of the samples are very narrow.

[Preliminary screening for antiviral AIDS drugs. VII. Report for fiscal year 1994].

Preliminary screening of antiviral AIDS drugs has been carried out using three different in vitro assay systems. Among 246 samples of different origin tested, six were shown to inhibit the growth of HIV in vitro. Two of the positive samples have hopeful signs, as the ranges of effective doses are wider than those of most of positive samples which had been found by us.

[Preliminary screening for antiviral AIDS drugs. IV. Report on fiscal year 1992].

Preliminary screening of antiviral AIDS drugs has been carried out using three different in vitro assay systems. Among 191 samples tested, seven were found to inhibit the growth of HIV in vitro. Four of seven have hopeful signs, as the ranges of effective doses of the samples are wide.

[Preliminary screening for antiviral AIDS drugs. IV. Report on fiscal year 1991].

Preliminary screening for antiviral AIDS drugs has been carried out using three different in vitro assay systems. Among 154 samples tested, nine were found to inhibit the growth of HIV in vitro. One of nine has a hopeful sign, as the range of effective doses of the sample is wide.

Antibody responses of swine to type A influenza viruses in the most recent several years.

A serological survey was conducted on 4,080 swine sera collected for the years 1985-90. The swine sera positive to A/New Jersey/8/76 (swine type H1N1) strain were observed in annual (10-20%) and monthly (20-40%) incidences during the observation period except for occasional months. Antibodies to recent human H1N1 viruses in swine were recognized in relation to the human H1N1 influenza epidemics. Antibody responses of swine to human H3N2 strains appeared irrespective of human epidemics with the virus in the years 1985-87. However, in 1988 almost no antibodies to three human H3N2 isolates of 1983-88 were observed for this year except a few months though the human epidemic occurred in the area. Although in 1989-90 many swine had antibodies to the three strains in the percentage of 3 to 35, no antibody to the latest isolate, A/Hokkaido/20/89 (H3N2), was found for almost all the months of both years. These findings differed markedly from the possible relationship between the prevalence of H3N2 virus-antibodies in swine and the human influenza epidemics, which were described previously in many reports including our studies.

[Preliminary screening for antiviral AIDS drugs. III. Report on fiscal year 1990].

Preliminary screening for antiviral AIDS drugs has been carried out using three different in vitro assay systems. Among 106 samples tested, five were found to inhibit the growth of HIV in vitro. Two of five have a hopeful sign, as the range of effective doses of the samples is wide.

[Preliminary screening for antiviral AIDS drugs. II. Report on fiscal year 1989].

Preliminary screening for antiviral AIDS drugs was carried out using three different in vitro assay systems. Among 104 samples tested, six were found to inhibit the growth of HIV in vitro. Four of six were acidic polysaccharides of sea weed origin and one was a well-known anti HIV chemical whose anti-HIV activity has not been reported.

Antibody responses of swine to type A influenza viruses during the past ten years in Japan.

A total of 6346 swine sera collected at an abattoir in the city of Obihiro, Hokkaido during the years 1978-87 were tested for the presence of antibodies to swine and human influenza viruses. A high incidence of antibody to A/New Jersey/8/76 (swine type H1N1) virus was observed throughout the 10 years except for the occasional month and a single long period of 15 months. Antibodies to human H3N2 virus in swine appeared to be related to the epidemics of human influenza which occurred in the study area during the years 1980-3, but unrelated to the epidemics during the years 1984-7. A large number of swine were found to be antibody positive to a human H1N1 virus during the period April to June 1964, and a smaller number, during the period November 1986 to June 1987. Both were in relation to human influenza epidemics. However, there were long periods where human H1N1 antibodies in swine could not be found.

Prevalence of human (H1N1) influenza virus-antibody in Japanese swine.

A total of 571 swine sera collected at an abattoir in the city of Obihiro, Hokkaido during the period February-November 1984 were tested for antibody against human (H1N1) influenza virus strains. A high prevalence of antibody was observed for only 3 months from April to June in that year, in 81/180 sera (45.0%) to A/USSR/92/77 strain and in 50/180 sera (27.8%) to a current epidemic strain (A/Hokkaido/1/84). Some cross-reactions were observed between the A/USSR/92/77 and A/Hokkaido/1/84 antibodies (r = 0.75). Only minor relationships were noted between the A/New Jersey/8/76 (swine type H1N1) and A/USSR/92/77 (r = 0.35) or A/Hokkaido/1/84 (r = 0.51) antibodies. Absorption of sera positive for antibody to the A/Hokkaido/1/84 strain with the homologous virus strain removed all detectable antibodies, while the absorption of the sera with the A/New Jersey/8/76 strain produced incomplete absorption in one half of the sera tested. These results strongly suggest that the swine became infected with a human H1N1 virus as piglets during an epidemic of influenza which occurred in the human population during January and February 1984.

Preparation of single bilayer liposomes by an electrocapillary emulsification method.

The single bilayer liposomes have been prepared by an electrocapillary emulsification technique based on interfacial fluctuation in the absence of surfactant. Electron microscopy showed the liposome to be a unilamellar vesicle with a size generally in the range 60-120 nm.

Examination of the Sephadex G10 beads uptake method for determination of bile salt monomer concentration in taurocholate-lecithin solutions.

Experiments have been undertaken to examine the validity of the method of Ammon and Walter for the determination of bile acid monomer concentrations in taurocholate-lecithin (TC-L) solutions. The procedure involves, basically, the uptake of the bile acid monomer by Sephadex G10 beads (exclusion limits 700 Da) in the presence of a suitable aqueous phase marker (raffinose). Several of the experimental variables involved in the bead-washing technique have been critically studied, and good precision in data (SD in the range of +/- 2-5% of the mean value) has been obtained. Monomer concentrations determined in the absence of lecithin over a wide range (10-70 mM) of TC were found to be in agreement with those obtained by Ammon. Most important, however, is the finding that TC monomer concentrations at constant NMBS were found to be constant in all solutions containing or not containing lecithin [here, the nonmixed micelle bile salt (NMBS) is the total bile salt concentration, but not including species involving lecithin, and is determined by dialysis equilibrium experiments].