A Correlation of the Solubility of Water in Hydrocarbons as a Function of Temperature Based on the Corresponding Vapor Pressure of Pure Water

A method of estimating the solubility of water in hydrocarbons as a function of temperature is given here. Hydrocarbons, lacking strong permanent dipoles or traditional hydrogen bonding, do not strongly attract water molecules. The extreme case of a medium bereft of attractive forces is a vacuum, into which water, nonetheless, evaporates. The solubility of water in hydrocarbons at various temperatures can be correlated to the vapor pressure of water at those temperatures. A simple thermodynamic explanation of the dependence on vapor pressure is offered

Coffee Stirrers and Drinking Straws as Disposable Spatulas

While metal spatulas are damaged through everyday use and become discolored and corroded by chemical exposure, drinking straws are inexpensive and disposable, reducing the risk of cross contamination during laboratory experiments. Drinking straws are also useful because they come in a variety of sizes; narrow sample containers such as NMR and EPR tubes can easily be filled using small diameter coffee stirrers, while bulk material can be transferred using larger drinking straws. Several types of drinking straws and coffee stirrers were cut at various angles and the amount of material picked up in a single scoop was massed thirty times. Standard deviations of the thirty measurements per straw indicate that approximately the same amount of material will be scooped each time by the same operator

Nicotinamide complex of silver(III) with expanded coordination number

In strongly alkaline media ([OH-] ≥ 0.12 M), nicotinamide (nica) forms a complex with square-planar Ag(OH)4- [nica] ≥ 0.05 M. The complex decomposes in seconds to nicotinamide N-oxide. The correlation of maximum absorbance of the complex with concentrations of nicotinamide and hydroxide requires that the complex is either the five-coordinate Ag(OH)4(H-1nica)2- or the six-coordinate Ag(OH)5(nica)2-. Comparison with the reactions of Ag(OH)4- with nicotinate ion (nic-) and acetamide under similar conditions indicates that nicotinamide coordinates with Ag(OH)4- by the amido group rather than the nitrogen on the pyridine ring or the amido oxygen. Kinetics of the Ag(III)- nica redox reaction are consistent with direct reaction between nicotinamide and uncoordinated Ag(OH4)-. Oxidation takes place at the pyridine ring, yielding nicotinamide N-oxide. Silver(III) is reduced to monovalent silver

Glucitol-core containing gallotannins inhibit the formation of advanced glycation end-products mediated by their antioxidant potential

Glucitol-core containing gallotannins (GCGs) are polyphenols containing galloyl groups attached to a 1,5-anhydro-D-glucitol core, which is uncommon among naturally occurring plant gallotannins. GCGs have only been isolated from maple (Acer) species, including the red maple (Acer rubrum), a medicinal plant which along with the sugar maple (Acer saccharum), are the major sources of the natural sweetener, maple syrup. GCGs are reported to show antioxidant, α-glucosidase inhibitory, and antidiabetic effects, but their antiglycating potential is unknown. Herein, the inhibitory effects of five GCGs (containing 1–4 galloyls) on the formation of advanced glycation end-products (AGEs) were evaluated by MALDI-TOF mass spectroscopy, and BSA–fructose, and G.K. peptide-ribose assays. The GCGs showed superior activities compared to the synthetic antiglycating agent, aminoguanidine (IC50 15.8–151.3 vs. \u3e300 μM) at the early, middle, and late stages of glycation. Circular dichroism data revealed that the GCGs were able to protect the secondary structure of BSA protein from glycation. The GCGs did not inhibit AGE formation by the trapping of reactive carbonyl species, namely, methylglyoxal, but showed free radical scavenging activities in the DPPH assay. The free radical quenching properties of the GCGs were further confirmed by electron paramagnetic resonance spectroscopy using ginnalin A (contains 2 galloyls) as a representative GCG. In addition, this GCG chelated ferrous iron, an oxidative catalyst of AGE formation, supported a potential antioxidant mechanism of antiglycating activity for these polyphenols. Therefore, GCGs should be further investigated for their antidiabetic potential given their antioxidant, α-glucosidase inhibitory, and antiglycating properties

Phenol Nitration Induced by an {Fe(NO)\u3csub\u3e2\u3c/sub\u3e}\u3csup\u3e10\u3c/sup\u3e Dinitrosyl Iron Complex

Cellular dinitrosyl iron complexes (DNICs) have long been considered NO carriers. Although other physiological roles of DNICs have been postulated, their chemical functionality outside of NO transfer has not been demonstrated thus far. Here we report the unprecedented dioxygen reactivity of a N-bound {Fe(NO)2}10 DNIC, [Fe(TMEDA)(NO)2] (1). In the presence of O2, 1 becomes a nitrating agent that converts 2,4,-di-tert-butylphenol to 2,4-di-tert-butyl-6-nitrophenol via formation of a putative iron-peroxynitrite [Fe(TMEDA)(NO)(ONOO)] (2) that is stable below −80 °C. Iron K-edge X-ray absorption spectroscopy on 2 supports a five-coordinated metal center with a bound peroxynitrite in a cyclic bidentate fashion. The peroxynitrite ligand of 2 readily decays at increased temperature or under illumination. These results suggest that DNICs could have multiple physiological or deleterious roles, including that of cellular nitrating agents

Anti-glycation and anti-oxidative effects of a phenolic-enriched maple syrup extract and its protective effects on normal human colon cells

Oxidative stress and free radical generation accelerate the formation of advanced glycation endproducts (AGEs) which are linked to several chronic diseases. Published data suggest that phenolic-rich plant foods, show promise as natural anti-AGEs agents due to their anti-oxidation capacities. A phenolic-enriched maple syrup extract (MSX) has previously been reported to show anti-inflammatory and neuroprotective effects but its anti-AGE effects remain unknown. Therefore, herein, we investigated the anti-glycation and anti-oxidation effects of MSX using biochemical and biophysical methods. MSX (500 μg mL−1) reduced the formation of AGEs by 40% in the bovine serum albumin (BSA)–fructose assay and by 30% in the BSA–methylglyoxal (MGO) assay. MSX also inhibited the formation of crosslinks typically seen in the late stage of glycation. Circular dichroism and differential scanning calorimeter analyses demonstrated that MSX maintained the structure of BSA during glycation. In the anti-oxidant assays, MSX (61.7 μg mL−1) scavenged 50% of free radicals (DPPH assay) and reduced free radical generation by 20% during the glycation process (electron paramagnetic resonance time scan). In addition, the intracellular levels of hydrogen peroxide induced reactive oxygen species were reduced by 27–58% with MSX (50–200 μg mL−1) in normal/non-tumorigenic human colon CCD-18Co cells. Moreover, in AGEs and MGO challenged CCD-18Co cells, higher cellular viabilities and rapid extracellular signal-regulated kinase (ERK) phosphorylation were observed in MSX treated cells, indicating its protective effects against AGEs-induced cytotoxicity. Overall, this study supports the biological effects of MSX, and warrants further investigation of its potential as a dietary agent against diseases mediated by oxidative stress and inflammation

Mimicking the Neurotrophic Factor Profile of Embryonic Spinal Cord Controls the Differentiation Potential of Spinal Progenitors into Neuronal Cells

Recent studies have indicated that the choice of lineage of neural progenitor cells is determined, at least in part, by environmental factors, such as neurotrophic factors. Despite extensive studies using exogenous neurotrophic factors, the effect of endogenous neurotrophic factors on the differentiation of progenitor cells remains obscure. Here we show that embryonic spinal cord derived-progenitor cells express both ciliary neurotrophic factor (CNTF) and brain-derived neurotrophic factor (BDNF) mRNA before differentiation. BDNF gene expression significantly decreases with their differentiation into the specific lineage, whereas CNTF gene expression significantly increases. The temporal pattern of neurotrophic factor gene expression in progenitor cells is similar to that of the spinal cord during postnatal development. Approximately 50% of spinal progenitor cells differentiated into astrocytes. To determine the effect of endogenous CNTF on their differentiation, we neutralized endogenous CNTF by administration of its polyclonal antibody. Neutralization of endogenous CNTF inhibited the differentiation of progenitor cells into astrocytes, but did not affect the numbers of neurons or oligodendrocytes. Furthermore, to mimic the profile of neurotrophic factors in the spinal cord during embryonic development, we applied BDNF or neurotrophin (NT)-3 exogenously in combination with the anti-CNTF antibody. The exogenous application of BDNF or NT-3 promoted the differentiation of these cells into neurons or oligodendrocytes, respectively. These findings suggest that endogenous CNTF and exogenous BDNF and NT-3 play roles in the differentiation of embryonic spinal cord derived progenitor cells into astrocytes, neurons and oligodendrocytes, respectively

Reduction of the Tetrahydroxoargentate(III) Ion by Thiocyanate in Aqueous Alkaline Media

The reduction of Ag(OH)4- by thiocyanate ion in the range 5 × 10-4 ≤ [SCN-] ≤ 0.25 M was studied in aqueous alkaline media at 25 °C and μ = 1.2 M by stopped-flow spectrophotometry. At [SCN-] ≤ 0.01 M, the reaction was found to be first-order in each reactant, with an apparent second-order rate constant of 21.7 ± 0.3 M-1 s-1. At higher thiocyanate concentrations, silver(III) disappearance continues to appear pseudo first order, but the thiocyanate dependence becomes complex. Oxidation products are SO42-, OCN-, and (at high SCN- only) cyanide ion. A mechanism is proposed consisting of a series of two-electron redox steps. Competition between SCN- and reaction intermediates for remaining silver(III) accounts for changes in both rate and product distribution. The activation enthalpy and entropy for the initial step are 28.3 ± 1.2 kJ mol-1 and -129 ± 7 J mol-1 K-1 respectively. Numerical simulation and reaction with potential intermediates have been used to support the conclusions. © 1991, American Chemical Society. All rights reserved

Oxidation of organic compounds by silver(II). Reactions with aliphatic diols and α-hydroxy acids

The rate of oxidation by silver(II) of succinic, malic, tartaric, glycolic and lactic acids and 1,2- ethanediol, 1,2-propanediol, 1,3-propanediol, and 1,2-ethanediol monomethyl ether has been investigated in acidic perchlorate media by the stopped-flow technique. For all substrates (S) except 1,2-ethanediol and 1,3-propanediol reactions were first order in total silver and in S with an observed rate constant kobs=2(k1 + k2Kh[H+]-1) reflecting parallel oxidations by aquasilver(II)(k1) and AgOH+ (k2). In the case of 1,2-ethanediol and 1,3-propanediol, plots of the pseudo first order rate constant kobs versus [S] showed a levelling off behavior which is indicative of an association process prior to redox. The proposed mechanism involves formation of a Ag(I)-diol complex, rapidly oxidized by aquasilver(II) to Ag(II)-diol, which, in turn, undergoes redox decomposition. Stoichiometry, nature of the intermediate species, and reactivity patterns are discussed. © 1987