Organic microcrystals ranging from several tens nm to µm in size of several chromophores were successfully prepared by simply dispersing ethanol solutions of compounds into stirred water, i.e. by a reprecipitation method. The size of microcrystals was found to depend on concentration of ethanol solutions, dispersing conditions, temperature and so on.

Ion Binding to Poly(oxyethylene) in Methanol latter for the p-nitroperbenzoic acid results could be appreciable. Effect of Brownian Motion of the LigandWhen the target area is smaller than the mean free path of the ligand, the diffusion-controlled rate constant cannot be deduced from a simple diffusion equation.36 However, the mean free path, L, calculated from the following equation36 is only 0.07 Á for p-nitroperbenzoic acid, where M is molecular weight and R is gas constant: L D( §iY Therefore, the effect of Brownian motion is almost negligible for the horseradish peroxidase-ligand system. Publication costs assisted by Tohoku UniversityThe binding of alkali metal cation with poly(oxyethylene) was studied by means of conductometry in methanol. Apparent binding constants, KA, were determined by assuming the existence of discrete binding sites distributed every a monomer units along the polymer chain. KA increased in the order Li < Na < K < Cs < Rb. For large anions, such as thiocyanate or perchlorate, the formation of an ion pair complex was indicated. KA and a increased rapidly with decreasing salt concentration. This result was interpreted by the increased electrostatic repulsion between bound ions. The linear relationship between a1/2 and Cs"1/2 conforms to the Gaussian distribution of the segment between charges as well as to the partial retention of crystalline conformation of the poly-(oxyethylene)-ion complex.Publication costs assisted by the National Science Foundation and the Petroleum Research Fund Two recent theories for ionic mobility, the Hubbard-Onsager theory which is based on a continuum model and the Wolynes theory which is based on a stochastic model, are critically tested by comparison with conductance data. Both theories predict finite mobilities as the ionic size decreases and thus can successfully account for many of the observed features of conductance data. The models upon which the theories are based are described in detail and the current state of ionic mobility theory is discussed.

A statistical model for the cooperative thermochromic transition of polysilanes is proposed. The basic assumption of this treatment is that the origin of the thermochromism is the conformational transition between two ordered states, i.e., all-trans and helix structures. We have calculated the partition function of a single polysilane chain by assuming that the total conformational energy of the chain can be described by a simple sum of the nearest-neighbor interaction energies and the energies of trans, gauche(+), and gauche(-) structures. A comparison of the theoretical results with the experimental intensity of absorption maxima has enabled us to estimate the free energy of stabilization of the ordered sequences. The calculation suggests that the transition-type thermochromism is observable only when the conformational stabilization energies of the ordered sequences are large.

Ring sideroblasts are a hallmark of sideroblastic anemia, although little is known about their characteristics. Here, we first generated mutant mice by disrupting the GATA-1 binding motif at the intron 1 enhancer of the ALAS2 gene, a gene responsible for X-linked sideroblastic anemia (XLSA). Although heterozygous female mice showed an anemic phenotype, ring sideroblasts were not observed in their bone marrow. We next established human induced pluripotent stem cell-derived proerythroblast clones harboring the same ALAS2 gene mutation. Through coculture with sodium ferrous citrate, mutant clones differentiated into mature erythroblasts and became ring sideroblasts with upregulation of metal transporters (MFRN1, ZIP8, and DMT1), suggesting a key role for ferrous iron in erythroid differentiation. Interestingly, holo-transferrin (holo-Tf) did not induce erythroid differentiation as well as ring sideroblast formation, and mutant cells underwent apoptosis. Despite massive iron granule content, ring sideroblasts were less apoptotic than holo-Tf-treated undifferentiated cells. Microarray analysis revealed upregulation of antiapoptotic genes in ring sideroblasts, a profile partly shared with erythroblasts from a patient with XLSA. These results suggest that ring sideroblasts exert a reaction to avoid cell death by activating antiapoptotic programs. Our model may become an important tool to clarify the pathophysiology of sideroblastic anemia.

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When a polymer strongly binds metal ions in solution, a substantial number of counterions can also be bound to it, if the polarity of the solvent is not too high. This is actually obeerved for poly(ethy1ene oxide) (PEO) and sodium thiocyanate in nitromethanel and PEO and barium salts in methanol.2 The phenomenon may be regarded as an ionic association between the cation of the PEO-metal complex and counteranion and resembles the ion condeneation of polyelectrolytes. Although our previous conductivity studies have disclosed directly the presence of ionic association, the analytical calculation is quite intricate because of the strong interactions between metal cations that were bound to the same PEO chain.t2 Thus the simultaneous use of a more straightforward analytical method may be desirable.1H and 1% NMR spectroscopy have frequently been applied to the investigation of ionic association, especially ion pair formation between alkali metal ions and carbanions.3~4 Downfield shifts of 1H and l3C signals were induced by the shift of the ion pair equilibrium toward tight ion pairs from free ions or solvent separated ion pairs. Here we wish to report the poseibility of estimating by lH NMR the ionic association between alkaline earth metal cations and counteranions on the PEO chain. It has been well established that PEO forms complexes with alkali and alkaline-earth metals in several organic solvents? A lH NMR study of PEO oligomers in methanol showed that a downfield shift of the methylene protons was induced by the complexation with potassium ion, although the absolute values of the chemical shift differences were small.6 On the other hand, a relatively large chemical shift was observed in the case of the complexation with alkaline-earth metal ions in the same s01vent.~ This was also considered to be induced by metal complexation, although the absolute chemical shift values were much different from those observed for alkali metalcations.Commercial PEO samples with an average molecular weight of 2 X 104 were used. lH NMR spectra were measured on a JEOL JNM-PMXGOSI spectrometer in deuterated methanol. The methylene protons of dioxane in benzene solution, which was added as an external standard, were taken as a reference. Chemical shift values were measured downfield with respect to the methylene signal of PEO in the absence of salt. Figure 1 shows a plot of the l H NMR chemical shift as a function of the [Ba2+1/[PE01 ratio for barium thiocyanate and barium chloride in deuterated methanol. As shown in the f i i e , the addition of barium salts causes a downfield shift of the methylene protons of PEO. Both curves seem to saturate at a certain value of the ratio [Ba2+]/[PEO]. These curves correspond well to the conductivity curves of our previous study,2 since the ratio [Ba2+]/[PE0] at which the chemical shift or conductivity approaches an asymptotic value is very similar. Thus it is natural to consider that the chemical shift is induced by the complexation of PEO with Ba2+ ion. However, it should be noted that the asymp...

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A 55-year-old woman suffered from hemorrhagic tendency. She had severe thrombocytopenia without any hematological or coagulatory abnormalities, and a bone marrow examination revealed an increased number of megakaryocytes without any abnormal cells or blasts. No lymphadenopathy or hepatosplenomegaly was observed on computed tomography. She was initially diagnosed with immune thrombocytopenic purpura (ITP). None of the treatments administered for ITP produced a response. However, abnormal cells were eventually found during the third bone marrow examination. The pathological diagnosis was mature B-cell lymphoma. Rituximab-containing chemotherapy produced a marked increase in the patient's platelet count, and her lymphoma went into complete remission.