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.     

Plant wound compounds from oviposition scars used in host discrimination by a stem-galling sawfly

The stem-galling sawfly Euura lasiolepisuses one or more plant wound compounds resulting from oviposition scars as cues in host discrimination (avoiding sites occupied by conspecifics). Four experiments were conducted to test hypotheses about how Euurapartitions resources. Experiment 1 demonstrated that Euuraavoids ovipositing on nodes with scars from previous ovipositions. Experiment 2 showed no evidence that the sawfly uses oviposition-deterring pheromones and indicated there is a time lag following oviposition before the oviposition scar becomes a deterrent. Experiment 3 showed that sawflies avoid artificially formed scars, demonstrating that a plant cue alone can lead to host discrimination. Experiment 4 showed that visual or tactile cues are not necessary for host discrimination and indicated that a plant wound compound functions as an oviposition deterrent. Both experimental results and field surveys showed that Euuraoviposition scars were more uniformly distributed than expected if sawflies were ignoring previous ovipositions.     

Peroxyoxalate chemiluminescent assay for oxidase activities based on detecting enzymatically formed hydrogen peroxide

A sensitive peroxyoxalate chemiluminescent (PO-CL) assay for activities of oxidases (uricase, choline oxidase, cholesterol oxidase and xanthine oxidase) which catalyse a formation of hydrogen peroxide was developed using 4,4′-oxalyl-bis[(trifluoromethylsulphonyl)imino]trimethylene-bis(4-methylmorpholinium)trifluoromethanesulphonate as a chemiluminogenic reagent and 2,4,6,8-tetramorpholinopyrimido[5,4-d]pyrimidine as a fluorophore. The standard curve for hydrogen peroxide was linear over the range 1 × 10^?7-1 × 10^?4 mol/L. Relative standard deviations for oxidase assays were 5.1–12.7% (n = 10). Detection limits were 1 × 10^?3 U/mL for uricase, 5 × 10^?4 U/mL for choline oxidase, 5 × 10^?3 U/mL for cholesterol oxidase and 5 × 10^?4 U/mL xanthine oxidase (sample to blank ratio, 3).     

High-performance liquid chromatographic determination of short-chain aliphatic aldehydes using 4-(N,N-dimethylaminosulphonyl)-7-hydrazino-2,1,3-benzoxadiazole as a fluorescence reagent

High-performance liquid chromatographic determination of four short-chain aliphatic aldehydes using fluorescence detection was carried out with 4-(N,N-dimethylaminosulphonyl)-7-hydrazino-2,1,3-benzoxadiazole (DBD-H). DBD-H derivatives with three aliphatic aldehydes — formaldehyde, acetaldehyde and propionaldehyde — were synthesized and their fluorescence properties were examined. Relative fluorescence intensities of these compounds in acetonitrile were ca. ten-fold larger than those in aqueous acetonitrile. DBD-hydrazones could be separated by reversed-phase chromatography using aqueous acetonitrile as eluent and detection at 560 nm with excitation at 445 nm. Submicromolar levels of formaldehyde, acetaldehyde, propionaldehyde and butylaldehyde could be determined. The HPLC procedure using propionaldehyde as internal standard was applied to the measurement of acetaldehyde levels in normal human plasma before and 30 min after ingestion of ethanol.     

Induction of histidine decarboxylase activity in mouse skin after application of indole alkaloids,a new class of tumor promoter

The effects of various promoters in two-step carcinogenesis on the induction of histidine decarboxylase in the skin of mice was investigated. The potencies of various phorbol esters in inducing histidine decarboxylase activity were parallel with their tumor-promoting activities. Indole alkaloids such as dihydroteleocidin B and lyngbyatoxin A, which induced ornithine decarboxylase and promoted tumor development in the skin of mice with the same potency as 12-O-tetradecanoylphorbol-13-acetate (TPA), also induced histidine decarboxylase activity. These results suggest that histamine produced by this inducible histidine decarboxylase may play some role in tumor promotion.     

Preparation of a fluorescent derivative of benzoylecgonine, and preliminary studies of its application to the analysis of urine

A sensitive high-performance liquid chromatographic method using 3-bromomethyl-6,7-dimethoxy-1-methyl-2(1H)-quinoxalinone (Br-DMEQ) as a fluorescent labeling reagent is described for the determination of benzoylecgonine (BE) and ecgonine (EC). The Br-DMEQ derivatives of BE and EC were separated on a C₁₈ column and detected at 455 nm with excitation at 370 nm. The detection limits of the proposed method were 18.7 fmol for BE and 12.5 pmol for EC at a signal-to-noise ratio of 3. Relative standard deviations of five replicate measurements were 1.94% (10 pmol) and 2.98% (50 pmol) for BE and 6.3% (250 pmol) and 5.62% (1.25 pmol) for EC. This method was applied to the determination of BE in human urine. BE was extracted from urine by solvent extraction with chloroform—isopropyl alcohol (9:1, v/v) solution. Levels of 2.5 · 10⁻⁸ M BE in urine (25 pmol/ml) could be determined.     

Macaque monkeys show reversed ocular following responses to two-frame-motion stimulus presented with inter-stimulus intervals

Journal of Computational Neuroscience - When two-frame apparent motion stimuli are presented with an appropriate inter-stimulus interval (ISI), motion is perceived in the direction opposite to the...     

Apoptosis inhibitor of macrophage (AIM) expression in alveolar macrophages in COPD

Background

Marked accumulation of alveolar macrophages (AM) conferred by apoptosis resistance has been implicated in pathogenesis of chronic obstructive pulmonary disease (COPD). Apoptosis inhibitor of macrophage (AIM), has been shown to be produced by mature tissue macrophages and AIM demonstrates anti-apoptotic property against multiple apoptosis-inducing stimuli. Accordingly, we attempt to determine if AIM is expressed in AM and whether AIM is involved in the regulation of apoptosis in the setting of cigarette smoke extract (CSE) exposure.

Methods

Immunohistochemical evaluations of AIM were performed. Immunostaining was assessed by counting total and positively staining AM numbers in each case (n = 5 in control, n = 5 in non-COPD smoker, n = 5 in COPD). AM were isolated from bronchoalveolar lavage fluid (BALF). The changes of AIM expression levels in response to CSE exposure in AM were evaluated. Knock-down of anti-apoptotic Bcl-xL was mediated by siRNA transfection. U937 monocyte-macrophage cell line was used to explore the anti-apoptotic properties of AIM.

Results

The numbers of AM and AIM-positive AM were significantly increased in COPD lungs. AIM expression was demonstrated at both mRNA and protein levels in isolated AM, which was enhanced in response to CSE exposure. AIM significantly increased Bcl-xL expression levels in AM and Bcl-xL was involved in a part of anti-apoptotic mechanisms of AIM in U937 cells in the setting of CSE exposure.

Conclusions

These results suggest that AIM expression in association with cigarette smoking may be involved in accumulation of AM in COPD.