Low Molecular Weight Organic Compound Research Articles

Association of fresh low-molecular-weight organic compounds with clay-sized mineral fraction in soils of different organic carbon loading

Although the association of minerals and organic matter (OM) in soil plays an important role in the sequestration of C, the factors driving the initial formation of mineral-associated OM (MAOM), and thus the retention of new C input in soils are not yet fully understood. In this study, we investigated how the soil C loading and the differences in the N content of low-molecular-weight organic compound (LMWOC) input foster the rapid C retention in the soil's fine mineral fractions (clay and fine silt-sized fraction). Two topsoils (0–10 cm) with different C loading due to different long-term management (direct seeding vs. bare fallow) derived from an agricultural research trial were used for the short-term incubation experiment. In a 24-hour incubation experiment, we used two labeled substrates (without N, glucose, > 99% 13C and with N, amino acid mixture, > 98% 13C, > 98% 15N) to investigate how the different N content delivered by the LMWOC input determine the fate of newly formed OM in the MAOM pool. Our results show that the soil with low C loading and thus a low C saturation level retained more freshly added LMWOC in the fine MAOM pool compared to the high C-loading soil, demonstrating that the soil C loading is a major factor controlling the retention of freshly added OM at the early stage of MAOM formation. The LMW OM containing N significantly enhanced the recovery of freshly added LMWOC in the low C-loading soil but not in the high C-loading soil. This points to the great importance of the N availability for the retention of freshly added OM in soils. Our study showed that the level of the native OM content affects the fast retention of freshly added OM in the clay-sized fraction to a greater extent than the N availability of the OM substrate.

Nano-assembly and optical properties of difluoroboron dibenzoylmethane-polysilane

Aggregation of various fluorophores is a useful approach to build highly sensitive and selective fluorescent sensors. In this work, the ability of oligomeric polydiphenylsilanes to associate with fluorescent low molecular weight organic compound is illustrated by the formation of stable aggregates between poly[diphenyl-co-methyl(H)]silane and dibenzoylmethanatoboron difluoride in solution. The formation of these nano-structures in solution was investigated both experimentally using gel permeation chromatography, σ spectroscopy and fluorescence spectroscopy, and theoretically by molecular modeling. Thin films obtained from this solution have a characteristic morphology in which the nano-aggregates undergo a self-organizing process and form crystalline spherulites. Association between the fluorescent polysilane and the fluorescent diketonato boron complex proceeds with an increase of fluorescence (amplification efficiency up to 90%) through a FRET mechanism as a result of aggregation, a phenomenon that could be used in the development of fluorescent sensors.

Advances in Application of Unexploited Plant Bio-regulators for Fruit Production: A Review

The term ‘bio-regulator’ has been used to encompass the natural and synthetic compounds that regulate various plant growth and developmental processes. Plant bio-regulators (PBRs) previously called plant growth regulators. Use of PBRs with a unique fact finding support assistance from biotechnology made a new approach of manipulating plant biological activities for enhancing growth, yield, quality, nutritive value and an important tool to reduce biotic and abiotic stress in plants. PBRs like jasmonic acid (JA) and its derivatives act as an omnipresent signaling molecules which mediate plant responses to biotic and abiotic stress. Salicylic acid (SA) and methyl salicylate are endogenous signal molecules, also playing pivotal roles in regulating stress responses. A polyamine is low-molecular weight organic compound having two or more primary amino groups, act as ethylene repressor. Prohexodione calcium is a new generation anti-gibberellin. Along with listed names several other bio-regulators are in vogue to improve plant growth, development, stress resistance, pathogenic defense and productivity. In this review, it’s an attempt to portray existing advanced knowledge about under utilized bio-regulators role and utility in cultivation of fruit crops.

Negative-tone molecular glass photoresist for high-resolution electron beam lithography.

A low molecular weight organic compound containing bis-phenol A backbone (BPA-6OH) is reported as a negative-tone photoresist. This material has a high glass transition temperature and excellent thermal stability. A good contrast, well-resolved line pattern around 73.4 nm and sensitivity of 52 µC cm−2 can be received for negative-tone molecular glass photoresist upon exposure in electron beam lithography system. It indicates that the negative-tone molecular glass photoresist is one of the promising candidates for use in electron beam lithography.

Investigation of the conditions for selenium determination by photochemical vapor generation coupled to graphite furnace atomic absorption spectrometry

In this study instrumental parameters and sample preparation methods for Se determination using photochemical vapor generation (PVG) coupled to graphite furnace atomic absorption spectrometry (GF AAS) were investigated. Coconut water was selected as sample due to its nutritional importance and matrix complexity. The PVG was performed in a flow injection mode. The Se volatile species, generated in the UV reactor, were separated from the condensed phase in a gas-liquid separator and introduced automatically in the graphite furnace. These species were trapped on the integrated graphite platform surface coated with Ir as permanent modifier. The PVG conditions such as concentration of low molecular weight organic compound (LMWC), sample and carrier gas flow rate, effect of reagents frequently used in sample preparation (HNO3 and H2O2) were investigated. Formic acid 0.44 mol L−1 was selected as LMWC. The addition of HNO3 (14 mmol L−1) and H2O2 (145 mmol L−1) increased the sensitivity. Pre-reduction of Se (VI) to Se (IV) was performed on-line in a quartz spiral tube coated with a thin film of TiO2. The insertion of Ar flow rate (115 mL min−1) before the reactor inlet has improved the sensitivity, comparing with the introduction of Ar after the reactor. UV-assisted photo-oxidation of coconut water samples was employed as an alternative sample preparation to avoid the NO3−/NO2−, and H2O2 interference. The figures of merit were: sensitivity 0.0680 s ng−1, limits of detection and quantification 0.65 μg L−1 and 2.2 μg L−1, respectively, and characteristic mass of 62 pg. The PVG efficiency was estimated as 79% when comparing with conventional hydride generation. Furthermore, a mass balance study was accomplished in order to identify possible analyte losses in the PVG system, which the overall recovery was up to 85%. The results of recovery tests accomplished with real samples of coconut waters varied between 80 and 103% for Se (IV), Se (VI), and selenomethionine.

MicroRNA-small molecule association identification: from experimental results to computational models.

Small molecule is a kind of low molecular weight organic compound with variety of biological functions. Studies have indicated that small molecules can inhibit a specific function of a multifunctional protein or disrupt protein-protein interactions and may have beneficial or detrimental effect against diseases. MicroRNAs (miRNAs) play crucial roles in cellular biology, which makes it possible to develop miRNA as diagnostics and therapeutic targets. Several drug-like compound libraries were screened successfully against different miRNAs in cellular assays further demonstrating the possibility of targeting miRNAs with small molecules. In this review, we summarized the concept and functions of small molecule and miRNAs. Especially, five aspects of miRNA functions were exhibited in detail with individual examples. In addition, four disease states that have been linked to miRNA alterations were summed up. Then, small molecules related to four important miRNAs miR-21, 122, 4644 and 27 were selected for introduction. Some important publicly accessible databases and web servers of the experimentally validated or potential small molecule-miRNA associations were discussed. Identifying small molecule targeting miRNAs has become an important goal of biomedical research. Thus, several experimental and computational models have been developed and implemented to identify novel small molecule-miRNA associations. Here, we reviewed four experimental techniques used in the past few years to search for small-molecule inhibitors of miRNAs, as well as three types of models of predicting small molecule-miRNA associations from different perspectives. Finally, we summarized the limitations of existing methods and discussed the future directions for further development of computational models.

Self-Assembled Coumarin Nanoparticle in Aqueous Solution as Selective Mitochondrial-Targeting Drug Delivery System.

The development of specifically targeted nanoparticles for subcellular organelles modified with a low-molecular-weight organic compound as drug nanocarriers can bring about wide applications in cancer therapy. However, their utility has been hampered by low selectivity, poor biodistribution, and limited efficiency. Herein, we report the aggregation behavior of a triphenylphosphonium-appended coumarin probe (TPP-C) in an aqueous solution and its applications as a mitochondria-targeting probe, and drug delivery carrier, which is a rare example for a low molecular-weight organic compound. The TPP-C formed homogeneous nanoparticles with small diameters in water as well as in mixtures of organic solvents and water. In pure water, the homogeneous nanoparticles induced J-aggregation, whereas in mixed solvents, the homogeneous nanoparticles induced H-aggregation. The luminescence intensities of nanoparticles originated from the aggregation-induced emission (AIE) effect in pure water and also in mixtures of organic solvents and water. These findings indicate that the AIE effect of TPP-C was dependent on the solvent. More interestingly, the TPP-C nanoparticles selectively accumulated in mitochondria. The TPP-C nanoparticles alone exhibited noncytotoxicity toward cancer cells. However, with the encapsulation of the anticancer drug doxorubicin (DOX) into the TPP-C nanoparticles, the DOX was efficiently delivered to the mitochondria. These results indicated that the proposed system demonstrates promise as a platform for future clinical medication, particularly for specific suborganelle-targeted drug delivery systems for cancer therapy.

The hypnotic bromovalerylurea ameliorates 6-hydroxydopamine-induced dopaminergic neuron loss while suppressing expression of interferon regulatory factors by microglia

The low molecular weight organic compound bromovalerylurea (BU) has long been used as a hypnotic/sedative. In the present study, we found that BU suppressed mRNA expression of proinflammatory factors and nitric oxide release in lipopolysaccharide (LPS)-treated rat primary microglial cell cultures. BU prevented neuronal degeneration in LPS-treated neuron-microglia cocultures. The anti-inflammatory effects of BU were as strong as those of a synthetic glucocorticoid, dexamethasone. A rat hemi-Parkinsonian model was prepared by injecting 6-hydroxydopamine into the right striatum. BU was orally administered to these rats for 7 days, which ameliorated the degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and alleviated motor deficits. BU suppressed the expression of mRNAs for interferon regulatory factors (IRFs) 1, 7 and 8 in the right (lesioned) ventral midbrain as well as those for proinflammatory mediators. BU increased mRNA expression of various neuroprotective factors, including platelet-derived growth factor and hepatocyte growth factor, but it did not increase expression of alternative activation (M2) markers. In microglial culture, BU suppressed the LPS-induced increase in expression of IRFs 1 and 8, and it reduced LPS-induced phosphorylation of JAK1 and STATs 1 and 3. Knockdown of IRFs 1 and 8 suppressed LPS-induced NO release by microglial cells. These results suggest that suppression of microglial IRF expression by BU prevents neuronal cell death in the injured brain region, where microglial activation occurs. Because many Parkinsonian patients suffer from sleep disorders, BU administration before sleep may effectively ameliorate neurological symptoms and alleviate sleep dysfunction.

A new method to constrain soil development time using both OSL and radiocarbon dating

The time over which a soil has developed since the parent materials were deposited and subaerially exposed, referred to here as soil development time, is of considerable interest to pedologists, geomorphologists, geologists, archeologist, and paleoclimatologists. Soil development time has been estimated both indirectly, based on the degree of soil development, and directly, by radiocarbon dating of soil organic matter, optically stimulated luminescence (OSL) dating of parent material deposition, and through exposure dating using cosmogenic nuclides. Here we propose a new model for estimating the soil development time by subtracting the low molecular weight (LMW) or pyrolysis-volatile 14C age of the uppermost A horizon of a soil from the OSL age of the C horizon of the parent material [soil time=OSL age(parent C horizon)−14C age(LMW fraction of uppermost A horizon)]. The LMW organic compound fraction represents the most mobile carbon compounds in the soil organic carbon pool, and is least resistant to physical, chemical, and biodegradation in the soil environment, potentially yielding the youngest 14C age. OSL dating of the C horizon provides an estimate of the time since deposition of unconsolidated parent material. Thus, the difference in the two ages can be used to estimate the time that has elapsed for pedogenic alteration from deposition of the parent material to the most recent additions of soil organic carbon. We applied this new approach in four scenarios: (1) in a modern soil that developed downward in loess; (2) in a buried soil developed in aggrading loess (a cumulative soil which grows upward); (3) in a buried soil formed in dune sand; and (4) in a counterexample showing that simple subtraction is not always appropriate because of changes in soil's parent materials from loess to sand. These case studies reveal that this approach constrains soil development time more reasonably than can be commonly done with either OSL or radiocarbon dating alone. The difference in 14C ages between the uppermost and lowermost sola of a soil profile almost certainly underestimates the time of soil development, and the difference in OSL ages taken from sediment units overlying and underlying a buried soil most likely overestimates it. A combination of OSL and radiocarbon dating better constrains soil development time, broadening the applications of these two dating methods beyond their use for cross-checking the accuracy of the other dating method.

Chiral discrimination by a cellulose polymer: differential crystallization inhibition of enantiomers in amorphous dispersions

With the goal of better understanding how polymers inhibit crystallization in amorphous solid dispersions, crystal growth rates of the R and S enantiomers of a model chiral compound in the presence of chiral and achiral polymers were evaluated. The crystal growth rates of enantiomers in undercooled melts were inhibited to different extents by the same mass fraction of a chiral polymer, hydroxypropylmethyl cellulose acetate succinate. This is most likely due to differences in the ability of each enantiomer to form hydrogen bonding interactions with the polymer, which in turn impacts the crystallization behavior of the low molecular weight organic compound. In contrast, the achiral polymer polyvinylpyrrolidone, and the chiral polymer, hydroxypropylmethylcellulose phthalate showed the same inhibitory impact on each enantiomer.

Вплив 2-(2-гідроксифенокси) ацетил-L-пролінат натрію на про- та антиоксидантний статус у слизовій оболонці шлунка щурів за умов стресу

We investigated the preventive effect of low molecular weight organic compound 2-(2-hydroxyphenoxy) acetyl-L-prolinat sodium on erosive and ulcerative lesions in the gastric mucosa caused by stress. It was established that prophylactic administration of this substance to rats at a dose of 1 mg/kg reduced the lesion area by 56.7%. 2-(2-hydroxyphenoxy) acetyl-L-prolinat sodium efficiently restored the impaired pro-/antioxidative balance in the gastric mucosa of rats under stress: the content of diene conjugates was reduced by 1.24 times, TBA-active products reduced by 1.31 times, Schiff's bases reduced by 1.28 times. This effect was accompanied by increased activities of the superoxide dismutase, catalase and of glutathione system.

Cholesteric colloidal liquid crystals from phytosterol rod-like particles

We report the first observation of chiral colloidal liquid crystals of rod-like particles from a low molecular weight organic compound—phytosterols. Based on the particles shape and crystal structure, we attribute this phenomenon to chiral distribution of surface charge on the surface of neighbouring rods.

Biodegradation of low molecular weight organic compounds and their contribution to heterotrophic soil respiration in three Japanese forest soils

Low molecular weight (LMW) organic compounds in soil solution could be important substrates for heterotrophic soil respiration. The importance of LMW organic compound mineralization in heterotrophi ...

Preparation of highly concentrated and stable suspensions of silver nanoparticles by an organic base catalyzed reduction reaction

Highly concentrated and stable suspensions of silver nanoparticles have been synthesized by chemical reduction from silver nitrate in a formaldehyde reductant using an organic base, triethylamine, as the reaction promoter. In this reaction, a low molecular weight organic compound, thiosalicylic acid (TSA), was used as the protecting agent. The average size of the silver nanoparticles prepared from this method was less than 10 nm, which allowed low-temperature sintering of the metal. The suspensions were further stabilized by the addition of excessive triethylamine, which forms an amine salt with TSA. A 50 wt%, stable suspension has been prepared. The suspensions of silver nanoparticles prepared by this method are free from any metal ion contamination, and are suitable for use in semiconductor industries.

Biaxial smectic A liquid crystal in a pure compound.

The synthesis and characterisation is reported of a low molecular weight organic compound to exhibit the biaxial smectic A (SmAb) phase, which shows a transition from the partial bilayer uniaxial SmAd phase to the SmAdb phase as the temperature is lowered.

A pseudo first order rate model for the adsorption of an organic adsorbate in aqueous solution

Five low rank, coal-based adsorbents, i.e. coal, grus, two chars, and an activated carbon were used to adsorb a low molecular weight organic compound from aqueous solution. The rates of adsorption were found to conform to pseudo first order kinetics with good correlation (r2 greater than 0.996). This kinetic model was used to calculate pseudo first order rate constants (k1′ min −1) and relative rate constants (rate constant/unit mass of adsorbent, k1″ min−1 g−1) for the adsorption process. Rate properties have been explained in terms of both a diffusion and chemically controlled rate determining step. Rate constants for the five adsorbents vary as expected on the basis of their physical properties, that is slowest for grus (compressed coal) and fastest for the activated carbon. © 1999 Society of Chemical Industry

Simultaneous ageing and crystallization processes within the glassy state of a low molecular weight substance

The superposition of physical aging and crystallization processes within the glassy state of a low molecular weight organic compound, a fulvene, at temperatures as far as 40 K below the glass transition temperature is reported. This behavior is not caused by impurities or decomposition. We attribute this effect to small scale translational and orientational motions allowing simultaneously the development of long range order and the relaxation of the glassy state.

Heterotrophic eubacteria isolated from cultures of the cyanobacterium, spirulina maxima

AbstractThree distinct heterotrophic eubacterial strains were isolated from mixotrophic cultures of the filamentous cyanobacterium, Spirulina maxima (Gom) Geitl. Spirulina spp. are considered to be prime candidates for the phototrophic production of biomass protein, particularly in developing countries. These cyanobacteria are extreme alkaliphiles and halophiles, making their production in arid regions promising.Most previous studies on the eubacteria which live in Spirulina culture systems have focused on determining the possible presence of pathogenic species in biomass protein. Little has been done to understand the symbiotic relationships between the cyanobacterium and its eubacterial cosymbionts. From the perspective of a heterotrophic eubacterium, autotrophic cultural systems of Spirulina have limited carbon and energy resources, being limited to cyanobacterial exudates.In this study, three eubacterial strains were isolated and studied. One strain, a Gram‐negative, non‐sporing, motile rod, grew exceptionally well in a mineral salts medium where only a small amount of a single low molecular weight organic compound (e.g., acetate) was supplied as sole energy source. This strain was also extremely euryresponsive with respect to salinity and alkalinity as well. Two less well‐adapted eubacterial strains are also described.

The osmotic role of mannitol in the Phaeophyta: an appraisal

Natural abundance 13C nuclear magnetic resonance spectroscopy (NMR) has shown mannitol to be the only major low molecular weight organic compound present in osmotically significant amounts within cells of the following marine brown algae: Alaria esculenta, Ascophyllum nodosum, Ectocarpus siliculosus, Fucus serratus, F. spiralis, F. vesiculosus, Halidrys siliquosa, Laminaria digitata, L. hyperborea, L. saccharina and Pilayella littoralis. Samples of the top-shore alga Pelvetia canaliculata were found to contain volemitol in addition to mannitol. Quantitative gas-liquid chromatographic analyses have confirmed the presence of mannitol, at concentrations ranging from 83.3 to 314.0 mmol kg−1 (expressed in terms of intracellular water content) for plants maintained in a full-strength (100%) sea water medium. A study of the changes in intracellular mannitol concentration of six marine brown macroalgae immersed in hyposaline and hypersaline media (20–150% EA 1 sea water medium) showed that mannitol concentration varied as a direct function of salinity in all cases, providing support for the hypothesis that mannitol is intimately involved in osmotic adjustment in response to changes in external water status. Plants of the filamentous form P. littoralis maintained in darkness also showed a marked sensitivity of intracellular mannitol concentration to alterations in the external salt concentration. Overall, the data support an osmotic, rather than a respiratory role for the large internal pools of mannitol in such algal cells.