On the Stability of Clathrate Hydrates Encaging Polar Guest Molecules: Contrast in the Hydrogen Bonds of Methylamine and Methanol Hydrates

Abstract

The stability of clathrate hydrates encaging highly polar guests has been investigated in order to explain the experimental observation that some amines form clathrate hydrates but alcohols act as inhibitor to hydrate formation. We choose methylamine and methanol as guest species and examine the stable structure, at which the total potential energy has a minimum value. At the local minima of those two hydrates, the potential energies of water-water and guest-water, and their hydrogen bonded networks are compared. It is found that methanol does not retain the host lattice structure, while the host-network structure is kept in the presence of methylamine. It is shown that the difference in the magnitude of the partial charge on the hydrogen atom between the hydroxyl and amino groups plays a much more significant role on the stability of both clathrate hydrates than the difference in molecular geometry. This is supported from the result of a methylamine-like model that has the same partial charges on the atoms in the hydrophilic site as methanol.     

Spatial distribution and mortality process ofAnoplophora malasiaca (Coleoptera: Cerambycidae) eggs in citrus groves

The study was carried out in two (A and B) citrus groves to clarify the spatial distribution patterns of eggs and larvae, and to analyse the mortality process of eggs. From the analysis by using the mean density and the mean crowding, it was clarified that the distributions of eggs were contagious and that larvae were more contagiously distributed than eggs. The τ and z indices showed that the operation of egg mortality was inversely density-dependent in both groves, and that the degree of inverse density-dependence was greater in A than in B grove. The spatial correlations between the emergence holes and the eggs or larvae in each tree, which were analysed by using ω index, showed that the distributions were more overlapping between the emergence holes and the larvae than the eggs. As the result of dividing trees into several groups according to the number of emergence holes, it was clarified that the survival rates of eggs were positively correlated with the number of emergence holes. In conclusion, inversely density-dependent mortality process was considered to be caused by lower mortality rates of eggs in the trees with more emergence holes. Especially in A grove, because the trees with more emergence holes were larger in diameter and more egg oviposition, the inversely density-dependent mortality process was considered to be detected more conspicuously than in B grove.     

Aggregation of hemoglobin S modified by bifunctional imidoesters

Sickle hemoglobin (Hb S) was cross-linked by two types of bifunctional imidoesters, dimethyladipimidate (DMA) and dimethyl-3,3'-dithiobispropionimidate (DTBP). These modified hemoglobins were separated into monomer, dimer and polymer fractions by gel filtration. All of these modified hemoglobins showed extremely left-shifted oxygen equilibrium curves with no cooperativity. The stabilities of these hemoglobins were also decreased. The solubilities of these modified hemoglobins in high-phosphate buffers were lower than those of native Hb S. Studies on the kinetics of the aggregation of these modified hemoglobins showed that intracross-linked Hb S with DMA and DTBP (DMA- and DTBP-modified monomeric Hb S) still retained the capability of aggregation with a delay time, while intercross-linked Hb S with DMA and DTBP (DMA- and DTBP-modified oligomeric Hb S) aggregated without a delay time. When the kinetics of aggregation was measured for mixtures of modified and native deoxy-Hb S, DMA-modified monomeric deoxy-Hb S shortened the delay time prior to aggregation of native deoxy-Hb S. The other modified deoxy-Hb S did not affect the delay time, suggesting that these modified oligomeric hemoglobins neither participate in the formation of nuclei nor copolymerize with native deoxy-Hb S.     

Utilization of phosphate diester by the marine diatom Chaetoceros ceratosporus

Utilization of phosphate diester (PDE) and phosphodiesterase(PDEase) production by five marine phytoplankton species wereexamined in the laboratory to evaluate the contribution of PDEto the growth of phytoplankton. Among the five marine phytoplanktonspecies tested, only Chaetoceros ceratosporus was able to usethe PDE compound, bis(p-nitrophenyl) phosphate (bis-NPP), effectivelyas a sole phosphorus source. In addition, C. ceratosporus simultaneouslyproduced both PDEase and alkaline phosphatase (APase) at almostequal activity levels under the phosphate-deficient condition.These results suggest that PDE compounds presumably play animportant role as a phosphorus source for PDEase-producing phytoplanktonin coastal environments.     

Mechanisms of modulation of neuronal nicotinic receptors by substance P and OAG

Substance P is known to modulate neuronal nicotinicacetylcholine receptors (nAChRs) in the sympathetic nervous system.There are two conflicting proposals for the mechanism of this effect, an indirect action mediated by protein kinase C (PKC) and a direct interaction with receptor subunits. We studied the mechanisms of thiseffect in PC-12 cells. Substance P enhanced the decay of thenicotine-induced whole cell current. This effect was fast in its onsetand was not antagonized by guanosine5'-O-(2-thiodiphosphate), a G protein blocker, orstaurosporine, a nonselective PKC blocker. Staurosporine failed toreverse the inhibition by 1-oleoyl-2-acetyl-sn-glycerol (OAG), a synthetic diacylglycerol analog known to activate PKC. Theinhibitory effects of the peptide and OAG were preserved in excisedpatches, but substance P applied to the extra patch membrane wasineffective in the cell-attached patch configuration. We conclude thatsubstance P modulates neuronal nAChRs most likely by direct interactions with the receptors but independently from activation ofPKC or G proteins and that PKC does not participate in modulation by OAG.

     

Enhancement of γ-linolenic acid production by Mucor ambiguus with nonionic surfactants

Summary -Linolenic acid (GLA) production by Mucor ambiguus IFO 6742, immobilised in Biomass Support Particles (BSPs), has been investigated in a fluidized-bed fermenter in the presence of nonionic surfactants. In this system, repeated batch cultivation was achieved at higher yield and productivity than by conventional methods, since microbial lipids inlcuding GLA were significantly secreted into the culture broth and/or on the surface of the cell wall.     

Effect of amino acid at the beta 6 position on surface hydrophobicity, stability, solubility, and the kinetics of polymerization of hemoglobin. Comparisons among Hb A (Glu beta 6), Hb C (Lys beta 6), Hb Machida (Gln beta 6), and Hb S (Val beta 6)

Surface hydrophobicity, stability, solubility, and kinetics of polymerization were studied using hemoglobins with four different amino acids at the beta 6 position: Hb A (Glu beta 6), Hb C (Lys beta 6), Hb Machida (Gln beta 6), and Hb S (Val beta 6). The surface hydrophobicity increased in the order of Hb C, Hb A, Hb Machida, and Hb S, coinciding with the hydrophobicity of the amino acid at the beta 6 position. Solubility of the oxy-form of these hemoglobins decreased in relation to increases in their surface hydrophobicity, suggesting that the solubility is controlled by the strength of hydrophobicity of the amino acid at the beta 6 position. The solubility of the oxy-form of these hemoglobins is always higher than that of the deoxy-form. There is a similar linear relationship between the solubility and surface hydrophobicity among deoxyhemoglobins A, C, and Machida. However, the solubility of deoxy-Hb S deviated significantly from the expected value, indicating that the extremely low solubility of deoxy-Hb S is not directly related to the hydrophobicity of the beta 6 valine. Kinetic studies on the polymerization of deoxy-Hb Machida revealed a distinct delay time prior to polymerization. This confirms our previous hypothesis that beta 6 valine is not responsible for the delay time prior to gelation. The kinetics of the polymerization of 1:1 mixtures of sickle and non-sickle hemoglobins were similar to those of pure Hb S, suggesting that only one of the two beta 6 valines is involved in an intermolecular contact. In mixtures of equal amounts of Hb S and Hb A, Hb C, or Hb Machida, half of the asymmetrical AS, SC, and S-Machida hybrid hemoglobins behaved like Hb S during nucleation, while the other half behaved like the non-sickle hemoglobin.     

Inherited hydrocephalus in Csk: Wistar-Imamichi rats; Hyd strain: a new disease model for hydrocephalus

Hydrocephalic rats were found in a breeding colony of Csk: Wistar-Imamichi strain rats. In males, the hydrocephalus were serious and could be detected from 7 days after birth. Survival was 3-4 weeks. In females, the hydrocephalus was moderate, there was no abnormal external appearance, and the rats were able to mature. Ventricular dilatation was excessive in males but moderate in females. The total frequency of hydrocephalus was 34.3% in both males and females. Breeding data indicated that this disease is heritable and is single dominant and X-linked (symbol, Hyd). The female moderate hydrocephalics could be detected by progeny tests without examining brain sections. No evidence of developmental anomaly was observed in the ventricles. This hydrocephalus was classified as being of the communicating type, and this strain was named the Hyd strain as an animal model for human hydrocephalus.     

A method for detecting the optimum day for mating during the 4-day estrous cycle in the rat; measuring the value of electrical impedance of the vagina

A method for detecting the optimum day for mating in the rat was investigated. Cyclic changes of electrical impedance of vagina (EIV) were studied in the rats. EIV indicated high value (over 3,000 omega) only at proestrus, and it was lower (under 3,000 omega) at other stage of estrous cycle. These results apparently indicate that measuring the EIV made to distinguish proestrus from other phases of estrous cycle. The female caged with male showed high copulation rate (88 approximately 96%) when her EIV had been over 3,000 omega.