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Previous research on the protection of soil organic C from decomposition suggests that soil texture affects soil C stocks. However, different pools of soil organic matter (SOM) might be differently related to soil texture. Our objective was to examine how soil texture differentially alters the distribution of organic C within physically and chemically defined pools of unprotected and protected SOM. We collected samples from two soil texture gradients where other variables influencing soil organic C content were held constant. One texture gradient (16-60% clay) was located near Stewart Valley, Saskatchewan, Canada and the other (25-50% clay) near Cygnet, OH. Soils were physically fractionated into coarse- and fine-particulate organic matter (POM), silt- and clay-sized particles within microaggregates, and easily dispersed silt- and clay-sized particles outside of microaggregates. Whole-soil organic C concentration was positively related to silt plus clay content at both sites. We found no relationship between soil texture and unprotected C (coarse- and fine-POM C). Biochemically protected C (nonhydrolyzable C) increased with increasing clay content in whole-soil samples, but the proportion of nonhydrolyzable C within silt- and clay-sized fractions was unchanged. As the amount of silt or clay increased, the amount of C stabilized within easily dispersed and microaggregate-associated silt or clay fractions decreased. Our results suggest that for a given level of C inputs, the relationship between mineral surface area and soil organic matter varies with soil texture for physically and biochemically protected C fractions. Because soil texture acts directly and indirectly on various protection mechanisms, it may not be a universal predictor of whole-soil C content.

The deprotonation of substituted (methylthiophenylcarbene)pentacarbonyl tungsten(0) ((CO)5W=C(SC6H4Z)CH3) and (benzoxymethylcarbene)pentacarbonyl tungsten(0) ((CO)5W=C(OCH2C6H4Z)CH3) in aqueous acetonitrile is studied. This indicates a transition state imbalance in which the loss of the carbene complex lags behind the proton transfer.

Byline: Minoru Fujii (1), Shinichiro Murashige (1), Yuka Ohnishi (2), Atushi Yuzawa (3), Hitoshi Miyasaka (4), Yoshimi Suzuki (2), Hiroshi Komiyama (1) Keywords: Concentration; decomposition; phytoplankton; particulate organic matter; kinetics; cultivation Abstract: Decomposition experiments were conducted on cultured phytoplankton (Skeletonema costatum) in seawater containing decomposer and consumer of size less than 500 Aum. We determined the decomposition rates of bulk particulate organic matter (POM), the ratio of labile to semi-refractory fractions in the POM, and the POM carbon/ nitrogen (C/N) ratio during decomposition. To identify the kinetic mechanisms involved in the reactions of different order (e.g., first- and second-order), we studied the sensitivity of reaction rates to the initial concentration of POM, ranging from 2.4 to 71 mg-C L.sup.-1. The results showed that decomposition consists of two first-order reactions: decomposition of labile and of semi-refractory particulate organic carbon (POC). The decomposition rate constants found for labile (0.13 day.sup.-1 at 20degC), and semi-refractory POC (0.008 day.sup.-1 at 20degC), and the carbon weight ratio of semi-refractory POC (13% at 20degC), were insensitive to the initial organic matter concentration. The time-dependence of the C/N ratio was also independent of this initial concentration. The decomposition rate constants and the content of semi-refractory POC did not change, regardless of the absence or presence of 25--500 Aum organisms in natural seawater. Author Affiliation: (1) Department of Chemical System Engineering, School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan (2) Department of Biology and Geosciences, Faculty of Science, Shizuoka University, Shizuoka, 422-8529, Japan (3) Japan NUS Co., Ltd., LOOP-X BLDG., 8F 9-15 Kaigan 3-chome, Minato-ku, Tokyo, 108-0022, Japan (4) Technical Research Center, Kansai Electric Power Co., Inc., Amagasaki, Hyogo, 661-0974, Japan Article History: Registration Date: 12/10/2004

Research is presented into the rates of solvolysis of tertiary alkyl chlorides with different steric requirement and experimental gas-phase stabilities.

Kinetic studies were done to characterize the first stage of the hydrolysis of (CO)5Cr=C(OMe)Ph and (CO)5Cr=(OMe)CH=CHPh in aqueous acetonitrile. It was demonstrated that the rate limiting step is the nucleophilic attack by OH- at high pH and by water at low pH that lead to the formation of a tetrahedral intermediate. In the presence of buffers, there was an observed general base catalysis of water addition.

Energy landscape theory of protein folding is based on statistical mechanics. It describes a protein's potential surface and assumes that the folding occurs by the organization of a group of structures, not just based on the nature of some of the uniquely defined structural intermediates. The most accurate model of a protein according to this theory is a heteropolymer frustrated as little as possible and having a rough landscape. It would be rather like a funnel and tend toward the native structure. Fast folding experiments and protein structure prediction present special problems.

The kinetics of aminolysis of a Fischer metal carbene complex, (methoxy(phenyl)carbene)pentacarbonylchromium(O) in a polar solvent is examined. The transition metal carbene complex composed of five alipathic amines is measured in 20% acetonitrile and 80% water at 25 degrees centigrade. Results indicate a general base catalysis since the second order constants increased as amine and hydroxide ion concentrations increased. The mechanisms involved in the process of aminolysis are discussed.

Enantioselective catalysts produce organic compounds in enantiomerically enriched form. They are highly efficient tools for the syhthesis of biologically active materials, such as pharmaceuticals and crop-protection chemicals, in which enantiomeric purity can be critical. The design of chiral ligands is the key to developing new enantioselective catalysts. Three unusual families of ligands have been used to develop practical technology for enantioselective hydrocyanation of olefins, ring-opening of epoxides, and hydrogenation of various compounds., Enantioselective catalysis is bringing about a revolution in asymmetric synthesis. Seldom has there been an area of chemistry where the scientific goals are so challenging, the economic benefits so obvious, [...]

A two-state, four-orbital, independent electron analysis of the first optical molecular hyperpolarizability, Β, leads to the prediction that [vertical bar] Β [vertical bar] maximizes at a combination of donor and [...]

A variety of factors that contribute to the differences in carbene complexes with the most important ones being that 5H(super+1) and 6H(super+1) are cationic which makes the C5H5(NO)(PPh3) Re moiety a stronger acceptor than the (CO)(sub5)M moieties are discussed, coupled with the fact that the deprotonated forms of 5H(super+1) and 6H(super+1) are aromatic molecules.

Induction of an Antibody Tha Catalyzes the Hydrolysis of an Amide Bond ANTIBODIES ARE CAPABLE OF CATALYZING A VARIETY OF chemical transformation (1-14). Antigens can be fabricated that structurally resemble [...]

Direct Bronsted Analysis of the Restoration of Activity to a Mutant Enzyme by Exogenous Amines ENZYMOLOGISTS HAVE BEEN ABLE TO adapt most of the tools of the physical organic chemist [...]

Physical inclusion of small molecules in larger structural lattices is well known in the crystalline state and is a common feature of the chemistry of zeolites. In the liquid state, a variety of synthetic macrocyclic molecules are available to complex and contain smaller guest species. An alternative strategy for binding is explored: assembly of cavity-forming structures from smaller subunits. Encapsulation of small guest molecules such as methane can be achieved with a synthetic structure that assembles reversibly through hydrogen bonding., Studies of molecular recognition phenomena have led to increasingly sophisticated compounds--cryptands (1), cryptophanes (2), and carcerands (3)--for binding ions and small molecules. These covalently bound structures feature macrocyclic shapes with [...]

The spherical geometry of buckminster-fullerene may have forged an unbreakable link between chemistry and soccer, but a group of chemists has now come up with another contender for the chemico-athletic [...]

Research is presented describing the study of protein flexibility using backbone dynamic-based NMR simulations.

Recognition and Transport of Adenine Derivatives with Synthetic Receptors MODEL RECEPTORS HAVE BEEN useful for exploring the intermolecular forces invqlved in the molecular recognition of adenine derivatives. Watson-Crick and Hoogsteen [...]

Research is presented describing the use of pKappaa values for (CO)5M(H)C(SR,SR')C6H4Z to settle a mechanistic uncertainty in the hydrolysis of Fischer carbenes which have alpha-carbons with acidic protons.

'Abzymes' Make Their Mark? Mother Nature does not always provide biochemists with all the tools that they would like to have. They would say she has been lax, for example, [...]