Single-molecule catalysis

Reaction Dynamics High-Resolution Spectroscopy Ultrafast Spectroscopy Biophysical Chemistry Heterogeneous Catalysis Single-Molecule Imaging and Electronics Surfaces and Interfaces Chemistry... 

The processes by which unsaturated monomers are converted to polymers of high molecular weight exhibit the characteristics of typical chain reactions. They are readily susceptible to catalysis, photoactivation, and inhibition. The quantum yield in a photoactivated polymerization in the liquid phase may be of the order of 10 or more, expressed as the number of monomer molecules polymerized per quantum absorbed. The efficiency of certain inhibitors is of a similar magnitude, thousands of monomer molecules being prevented from polymerizing by a single molecule of the inhibitor. ... 

When thiophene dioxide (106) was used as the diene component, true catalysis was observed with 107, affording the capsule bound adduct 108 (equation 32)93. The displacement of a single molecule of adduct by two molecules of starting material is, in principle, disfavored on entropic grounds, but turnover took place in this case due to the poorer affinity of the Diels-Alder adduct for the capsule. The rate enhancement of this reaction, based on the ratio of the half-life for the reaction outside vs inside the capsule, was 10-fold. 

A single molecule of ATP synthase catalyzes ATP synthesis by an irreversible mode of catalysis. 

A possibility that was proposed quite early for the glucose mutarotation, and that could conceivably be of importance for other reactions, is simultaneous catalysis by an acid and a base. It will be recalled from Section 8.1 that hydration requires addition of a proton at one site and removal of a proton from another. If both these processes were to occur in one step, either by means of separate acid and base molecules acting together or by action of a single molecule containing both an acidic and a basic center, we would designate the process as a concerted acid and base catalysis (Equation 8.39).60 Swain found that the rate of... 

Zhuang, X., et al. (2000). A single-molecule study ofRNA catalysis and folding. Science 288, 2048-2051. 

The modular architecture of RNA structure lends some support to the assumption that adding duplexes at the ends of the molecule will not generally perturb its behavior (Brion and Westhof, 1997 Tinoco and Bustamante, 1999). Single molecule studies demonstrated that the overall folding rate, substrate docking rate and catalysis by the Tetrahymena group I... 

Part V describes the electronic properties of single molecules at metal surfaces. In particular, M. L. Bocquet and coworkers focus on catalysis and reaction pathways from a theoretical point of view. Finally, R. Stadler s... 

Structural studies of the oxy-Cope catalytic antibody system reinforce the idea that conformational dynamics of both protein and substrate are intimately intertwined with enzyme catalysis, and consideration of these dynamics is essential for complete understanding of biologically catalyzed reactions. Indeed, recent single molecule kinetic studies of enzyme-catalyzed reactions also suggest that different conformations of proteins are associated with different catalytic rates (Xie and Lu, 1999). In addition, a number of enzymes are known to undergo conformational changes on binding of substrate (Koshland, 1987) that lead to enhanced catalysis two examples are hexokinase (Anderson and Steitz, 1975 Dela-Fuente and Sols, 1970) and triosephosphate isomerase (Knowles, 1991). 

The reaction is, in some way, being catalysed. Many say that the catalysis is by the iron metal, which is produced in the reaction. During catalysis, an intermediate single molecule is formed, which then breaks into the products. Therefore, the reaction is of the first order. 

The inner core of microemulsion can dissolve water to form water core called water pool [1], Little water pools of microemulsion surrounded by the single molecule interface formed by surfactants and co-surfactants can form particles whose sizes are from tens to hundreds of A [2], In this paper, a microemulsion-based method, and the formation conditions and growth mechanism of nanosized nickel sulfide particles are reported. This research is the base of application of ultrafme NiS particles on catalysis and optics. 

Homogeneous catalysis can be classified into single-species and complex catalysis, although the distinction is not always clear-cut. In the former, a single molecule or ion acts as the catalyst in the latter, the catalyst is a system of several species that interconvert into one another and differ in their catalytic properties. A further complication arises if significant fractions of the total catalyst material may be present in the form of reaction intermediates rather than free catalyst. If so, the concentration of the free catalyst is not known and may vary with conversion, and rate equations that instead contain the known, total amount of catalyst material are needed. 

The idea to analyze the catalysis by a single enzyme molecule was an obvious step. This was first demonstrated by Peter Lu and Sunney Xie [38]. They were able to show intensity fluctuation of the flavin cofactor of cholesterol oxidase using confocal single molecule detection. Our idea of single enzyme catalysis was to follow the turnover of a substrate into the product by catalysis of a single enz une molecule. We chose horse radish peroxidase and a non-fluorescence substrate dihydro-rhodamine which is turned over in the fluorescent product... 

K. Adachi, K. Oiwa, T. Nishizaka, S. Furuike, H. Noji, H. Itoh, M. Yoshida, K. Kinosita, Jr. Coupling of rotation and catalysis in Fi-ATPase revealed by single-molecule imaging and manipulation. Cell 130, 309-321 (2007)... 

In addition to the analysis of dynamic disorder, single-molecule approaches have the unique potential to reveal a number of processes that cannot be observed at the ensemble level. In the following, we wish to provide examples of how experiments with single enzymes can be extended beyond studies of dynamic disorder. We will show that single-molecule studies can identify rare events of enzyme inactivation, investigate cascade reactions, and determine the mechanism of interfacial catalysis at a phospholipid membrane. 

As another demonstration of control, we study a model in which there is more specific catalysis of molecule synthesis. Here, instead of single active molecule types forX and Y, we consider a system with k types of active X and Y molecules, X0t and Y ] (i 1.2. A). In this model, each active molecule type catalyzes the synthesis of only a few types (m < k) of the other species of molecules. Here we assume that both X and Y molecules have the same specificity (i.e., the same value of m) and study how this symmetry is broken. 

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