Yields of Free Ions in the X Radiolysis of Some Simple Saturated and Unsaturated Hydrocarbon Liquids: Effects of Molecular Structure and Temperature

1971 ◽  
Vol 49 (22) ◽  
pp. 3657-3664 ◽  
Author(s):  
M. G. Robinson ◽  
P. G. Fuochi ◽  
G. R. Freeman
Keyword(s):  
Molecular Structure ◽  
Interaction Model ◽  
Unsaturated Hydrocarbon ◽  
The Other ◽  
Coulombic Interaction ◽  
Secondary Electrons ◽  
Free Ions ◽  
Free Ion ◽  
Liquid Methane ◽  
Hydrocarbon Molecules

Pulse techniques were used at temperatures ranging from 120 to 293 °K. A quasifree electron conductance transient (k/u overshoot) was observed in liquid methane, but not in ethane, propane, cyclopropane, ethylene, propylene or butene-1. The free ion yield in methane, Gfi = 0.8 at 120 °K, is much larger than those in the other liquids, which at 183°K are: ethane, 0.13; propane, 0.076; cyclopropane, 0.04; ethylene, 0.017; propylene, 0.04; butene-1, 0.027. The activation energies of free ion formation are, in kcal/mol: ethane, 0.6; propane, 0.8; ethylene, 0.5; propylene, 1.0; butene-1, 1.0. The results are interpreted in terms of the coulombic interaction model. The distances that the secondary electrons penetrate the liquid away from their parent ions are greater when the hydrocarbon molecules are more sphere-like, and are reduced by the presence of a π bond in the molecule. Cyclopropane behaves somewhat like an olefin in this regard, a fact that is explained by the unusual bonding in the C3 ring. In the present liquids the only ionization events that contribute appreciably to the free ion yield are those in which the electron penetrates [Formula: see text] from the parent ion.

Activity of Plasmin and Streptokinase-Activator on Substituted Arginine and Lysine Esters

1966 ◽  
Vol 16 (01/02) ◽  
pp. 018-031 ◽  
Author(s):  
S Sherry ◽  
Norma Alkjaersig ◽  
A. P Fletcher
Keyword(s):  
Molecular Structure ◽  
Methyl Ester ◽  
Comparative Studies ◽  
Esterase Activity ◽  
Methyl Esters ◽  
Hydrolytic Activity ◽  
The Other ◽  
Other Hand

SummaryComparative studies have been made of the esterase activity of plasmin and the streptokinase-activator of plasminogen on a variety of substituted arginine and lysine esters. Human plasmin preparations derived by different methods of activation (spontaneous in glycerol, trypsin, streptokinase (SK) and urokinase) are similar in their esterase activity; this suggests that the molecular structure required for such esterase activity is similar for all of these human plasmins. Bovine plasmin, on the other hand, differs from human plasmin in its activity on several of the substrates studied (e.g., the methyl esters of benzoyl arginine and tosyl, acetyl and carbobenzoxy lysine), a finding which supports the view that molecular differences exist between the two animal plasmins. The streptokinase-activator hydrolyzes both arginine and lysine esters but the ratios of hydrolytic activity are distinct from those of plasmin and of other activators of plasminogen. The use of benzoyl arginine methyl ester as a substrate for the measurement of the esterase activity of the streptokinase-activator is described.

Binding of lead and copper(II) cations to hemicelluloses of rye bran

1986 ◽  
Vol 51 (10) ◽  
pp. 2250-2258 ◽  
Author(s):  
Rudolf Kohn ◽  
Zdena Hromádková ◽  
Anna Ebringerová
Keyword(s):  
Uronic Acid ◽  
Equilibrium Solution ◽  
Glucuronic Acid ◽  
The Other ◽  
Carboxyl Groups ◽  
Stoichiometric Ratio ◽  
Molar Ratios ◽  
Free Ions ◽  
Uronic Acid Content ◽  
The Relationship

Several fractions of acid hemicelluloses isolated from rye bran were characterized by molar ratios of saccharides (D-Xyl, L-Ara, D-Glc, D-Gal) and 4-O-methyl-D-glucuronic acid and protein content. Binding of Pb2+ and Cu2+ ions to these acid polysaccharides was considered according to function (M)b = f([M2+]f), expressing the relationship between the amount of metal (M)b bound to 1 g of the substance and the concentration of free ions [M2+]f in the equilibrium solution and according to the association degree β of these cations with carboxyl groups of uronic acid at a stoichiometric ratio of both components in the system under investigation. Acid hemicelluloses contained only a very small portion of uronic acid ((COOH) 0.05-0.18 mmol g-1); the model polysaccharide, 4-O-methyl-D-glucurono-D-xylan of beech, was substantially richer in uronic acid content ((COOH) 0.73 mmol g-1). Consequently, the amount of lead and copper bound to acid hemicelluloses is very small ((M)b 0.017-0.025 mmol g-1) at [M2+]f = 0.10 mmol l-1. On the other hand, much greater amount of cations ((M)f 0.09-0.10 mmol g-1) was bound to the glucuronoxylan. The association degree β was like with the majority of samples (β = 0.31-0.38). The amount of lead and copper(II) bound to acid hemicelluloses from rye bran is several times lower than that bound to dietary fiber isolated from vegetables (cabbage, carrot), rich in pectic substances.

2,5-Bis(3,7-dichloroquinolin-8-yl)-1,3,4-oxadiazole

2006 ◽  
Vol 62 (7) ◽  
pp. o2594-o2595 ◽  
Author(s):  
E Ye ◽  
Yong-Wei Zhang ◽  
Hui Wang ◽  
Yun-Yin Niu ◽  
Seik Weng Ng
Keyword(s):  
Molecular Structure ◽  
Dihedral Angle ◽  
Triazole Ring ◽  
The Other ◽  
Central Ring ◽  
Steric Crowding

In the title molecular structure, C20H8Cl4N4O, the 1,3,4-triazole ring is twisted with an r.m.s. deviation of 0.0035 Å. One of the quinolinyl substituents makes a dihedral angle of 55.8 (1)° with respect to the central ring, while the other is rotated by 71.7 (1)°; these twists are necessary to relieve steric crowding.

X-Radiolysis Ion Yields and Electron Ranges in Liquid Xenon, Krypton, and Argon: Effect of Electric Field Strength

1973 ◽  
Vol 51 (5) ◽  
pp. 641-649 ◽  
Author(s):  
Maurice G. Robinson ◽  
Gordon R. Freeman
Keyword(s):  
Field Strength ◽  
Gas Phase ◽  
Electric Fields ◽  
Zero Field ◽  
Energy Effect ◽  
Secondary Electrons ◽  
Total Ionization ◽  
Field Dependent ◽  
Free Ion ◽  
Ion Yields

X-Radiolysis ion yields were measured at electric fields between 1 and 60 kV/cm in argon at 87 °K, krypton at 148 °K, and xenon at 183 °K. The results were analyzed according to a theoretical model to obtain the total ion yields Gtot,the free ion yields at zero field strength Gfi0 and the most probable penetration ranges b of the secondary electrons in the liquids. The respective values were: Ar, 7.3, 2.9, 1330 Å; Kr, 13.0, 5.8, 880 Å; Xe, 13.7, 7.0, 720 Å. The total ionization yields in these substances are greater in the liquid than in the gas phase, probably due to smaller ionization potentials in the condensed phase (polarization energy effect). Field dependent electron mobilities are also reported.

(3-Acetylpyridine-κN)chlorobis(triphenylphosphine-κP)copper(I): a suitable candidate for absolute asymmetric synthesis?

2006 ◽  
Vol 62 (7) ◽  
pp. m1569-m1571
Author(s):  
Anders Lennartson ◽  
Kent Salo ◽  
Mikael Håkansson
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Title Compound ◽  
The Other ◽  
Nucleophilic Attack ◽  
Suitable Candidate ◽  
Π Interactions ◽  
Crystallization Conditions ◽  
Chiral Crystals ◽  
Triphenylphosphine Ligand

It was found that 3-acetylpyridine is capable of displacing triphenylphosphine from [CuCl(PPh3)3], forming the title compound, [CuCl(C7H7NO)(C18H15P)2]. The two triphenylphosphine ligands possess the same sense of chirality, and the molecules are therefore conformationally chiral. The compound was found to crystallize as a racemate (centrosymmetric space group) under the crystallization conditions employed. The molecular structure shows that the carbonyl C atom is blocked at one side by a triphenylphosphine ligand, while the other face is open for nucleophilic attack. Obtaining chiral crystals of the title compound is thus a future objective. In the crystal structure, C—H...O(=C)-bonded dimers are formed, which are further stabilized by π–π interactions. The dimers form infinite chains through weak C—H...π interactions.

Molecular Rotational Resonance Spectroscopy

1969 ◽  
Vol 23 (6) ◽  
pp. 575-581 ◽  
Author(s):  
Stuart Armstrong
Keyword(s):  
Molecular Structure ◽  
The Other ◽  
Resonance Spectroscopy ◽  
Rotational Resonance ◽  
Large Molecules ◽  
Intensity Measurements ◽  
Review Articles ◽  
Structure Determinations

A number of recent review articles have summarized the application of Molecular Rotational Resonance (MRR) spectroscopy to the area of molecular structure determinations and described how these applications have applied to chemistry. This article will briefly review this established area of MRR spectroscopy and describe two developments that offer the promise of expanding the applicability of MRR spectroscopy. The first development was the observation that some large molecules (by MRR standards) give a series of relatively intense, equally spaced bands that can be quickly recorded and assigned. The other development has been in the theory, procedures, and instrumentation required for accurate intensity measurements. These two developments, examples of each, and the implication of each for use by chemists, as well as molecular structure determinations, will be discussed. Spectrometers that are being used for studies in this established area and the two newer areas will be described in the Appendix.

Effects of cystment on cells of Oxytricha fallax possessing supernumerary dorsal bristle rows

Development ◽  
1981 ◽  
Vol 63 (1) ◽  
pp. 17-27
Author(s):  
Robert L. Hammersmith ◽  
Gary W. Grimes
Keyword(s):  
Molecular Structure ◽  
The Other ◽  
Basal Bodies ◽  
Resting Cyst

Cells of Oxytricha fallax possessing cytotactically inherited supernumerary dorsal bristle rows can redevelop those dorsal supernumerary rows after cystment, even though supernumerary ventral cortical structures are permanently lost through cystment. Previous work has demonstrated: (1) that cystment involves a complete dedifferentiation of all ciliary structures - all cilia, basal bodies, microtubules and fibres; and (2) that all ventral ciliary structures arise from a single ciliary primordium during excystment. These observations suggest the following conclusions. (1) The information for the redevelopment of supernumerary dorsal bristle rows during excystment is associated with some ultrastructurally unidentifiable molecular structure of the cyst cortex. (2) Cytotfrctic information for the development of cortical patterns is retained in at least two locations in the resting cyst; one location specifies the site of development of the ventral ciliature whereas the other specifies the location and pattern of the dorsal ciliature.

Macronutrients—Nitrogen

1999 ◽  
Author(s):  
Robert F. Keefer
Keyword(s):  
Molecular Structure ◽  
Amino Acids ◽  
Adenosine Triphosphate ◽  
Plant Tissue ◽  
The Other ◽  
Biochemical Reactions ◽  
Early Seedling ◽  
Pyrimidine Bases ◽  
Coloring Matter ◽  
Chlorophyll Molecule

Important considerations concerning nitrogen in plants include the amount of nitrogen required, the forms of nitrogen (inorganic and organic) present in plant tissue, the ways that nitrogen is used in plants and affected by fertilization, and symptoms plants show when nitrogen is deficient. After the nonmineral elements, N is found in the next largest amount. More N is needed by plants than all the other nonmineral elements combined, except for K. The range of N concentrations in plants is from 0.5 to 6.0%, with most plants having 1.5 to 3.0%. Inorganic forms of N in plants are NO3- (nitrate) and NH4+ (ammonium). These forms are usually present in relatively small amounts. Other inorganic forms of N do not accumulate without injury to the plants. Organic forms of N predominate in plants, mainly as amino acids and proteins. During and after absorption, N often follows this pathway: Proteins consist of a number of amino acids linked together into a large molecular structure. Once the proteins are formed in plants, N moves to other parts of the plant only if the proteins are split apart by hydrolysis into amino acids. The amino acids then flow freely to other parts of the plant where they can recombine into proteins again. Proteins consist of 12 to 19% nitrogen. Other complex proteins formed from amino acids are enzymes that act as catalysts in biochemical reactions. Proteins also act as reserve food in the seeds that is released during germination for early seedling growth. Another type of N-containing material is chlorophyll (the green coloring matter in leaves necessary for photosynthesis). In the center of a chlorophyll molecule is a Mg atom surrounded by four N atoms. Therefore, N is a part of the chlorophyll molecule and if N is deficient, then plants become yellow since there is insufficient chlorophyll produced. Other important N-complexes are purine and pyrimidine bases that can form adenosine triphosphate (ATP) during the respiration process as an energy carrier.

scholarly journals Bis(μ-diisopropylphosphanido-κ2 P:P)bis[hydrido(triisopropylphosphane-κP)platinum(II)]

2012 ◽  
Vol 68 (6) ◽  
pp. m808-m808
Author(s):  
Nicole Arnold ◽  
Holger Braunschweig ◽  
Alexander Damme
Keyword(s):  
Molecular Structure ◽  
Title Compound ◽  
The Other ◽  
Planar Structure ◽  
Square Planar

In the centrosymmetric molecular structure of the title compound [Pt2(C6H14P)2H2(C9H21P)2], each PtII atom is bound on one side to a phosphane ligand (PiPr3) and a hydrido ligand. On the other side, it is bound to two phosphanide ligands (μ-PiPr2), which engage a bridging position between the two PtII atoms, forming a distorted square-planar structure motif. The Pt...Pt distance is 3.6755 (2) Å. A comparable molecular structure was observed for bis(μ-di-tert-butylphosphanido)bis[hydrido(triethylphosphane)platinum(II)] [Itazaki et al. (2004). Organometallics, 23, 1610–1621].

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