POLYMERIC SEQUESTERING

Dogutan, M., H. Filik, and I. Tor. 2003. Preconcentration and speciation of chromium using a melamine based polymeric sequestering succinic acid resin Its application for Cr(VI) and Cr(IH) determination in... 

Proteins that bind to actin monomers and inhibit polymerization are designated as profilins (12—15 kD) (Sun et al., 1995). In addition to functioning as an actin-monomer-sequestering protein, profilin binds at least three other... 

ILs have the potential to overcome many of the problems of associated with current C02 capture techniques. ILs are particularly applicable in absorption of C02 while effectively avoiding the loss of sequestering agents. Other advantage of ILs is that they can be combined into polymeric forms, increasing the C02 sorption capacity compared with other ILs and conventional solvents and greatly facilitates the separation and ease of operation. 

A critical property of minimum protocells in the prebiotic environment would be their ability to sequester other molecules, including macromolecules. [142] In 1982, Deamer and Barchfeld [143] subjected phospholipid vesides to dehydration-rehydration cycles in the presence of either monomeric 6-carboxyfluorescein molecules or polymeric salmon sperm DNA molecules as extraneous solutes. The experiment modeled a prebiotic tidal pool containing dilute dispersions of phospholipids in the presence of external solutes, with the dehydration-rehydration cydes representing episodic dry and wet eras. They found that the vesides formed after rehydration... 

As is true today, most phosphate in the primordial crust must have been sequestered in nearly insoluble calcium phosphates and carbonates or in basalts, and only dissolved monomeric phosphate was produced by weathering. [201] However, the volatile polyphosphate P4O10 is known to be a component of volcanic gases. [205] This material originates from the polymerization of phosphate minerals in mag-... 

In the absence of a sequestering protein, actin polymerization will proceed to equilibrium or it will reach a steady-state extent of polymerization, at which point d[Apoiy]/dt = 0. [A] 00 is the critical concentration, equal to kJk+. In the presence of a sequestering protein, [Atotai] = [Afree] + [Apoiy] + [AX], and after polymerization reaches equilibrium, the unpolymerized actin concentration [A]oo will equal [AX ] + [Afree]. Hence,... 

This equation clearly demonstrates that the observed critical concentration will be increased by the presence of sequestering protein. In this respect, addition of a sequestering protein should reduce both the rate and the extent of polymerization. See also ABM-1 ABM-2 Sequences in Actin-Based Motors Actin-Based Bacterial Motility Actin Assembly Kinetics... 

An important performance characteristic of passive samplers that operate in the TWA regime is the diffusion barrier that is inserted between the sampled medium and the sorption phase. This barrier is intended to control the rate of mass transfer of analyte molecules to the sorption phase. It is also used to define the selectivity of the sampler and prevent certain classes (e.g., polar or nonpolar compounds) of analytes, molecular sizes, or species from being sequestered. The resistance to mass transfer in a passive sampler is, however, seldom caused by a single barrier (e.g., a polymeric membrane), but equals the sum of the resistances posed by the individual media (e.g., aqueous boundary layer, biofilm, and membrane) through which analyte diffuses from the bulk water phase to the sorption phase.19 The individual resistances are equal to the reciprocal value of their respective mass transfer coefficients and are additive. They are directly proportional to the thickness of the barrier... 

Vesicle and micelles are considered to be useful models for minimum protocells that had emerged in prebiotic times [200]. One of their properties should have been to sequester other molecules, including macromolecules, for self-replication. A central enigma to be addressed is related to various routes by which the enantiopure homochiral biopolymers were formed within such architectures. Polymerization of NCA of natural hydrophobic amino acids in water in the presence of phospholipids by Luisi et al. [201] has demonstrated that the hydrophobic environment enhances their rate of polymerization. 

Three enzymes, sucrose sucrose 1-fructosyl transferase (1-SST), fructan fructan 1-fructosyl transferase (1-FFT), and 1-fructan-p-fructosidase (1-FEH), appear to control fructan polymerization and depolymerization in the Jerusalem artichoke. Each is sequestered in the vacuole of the cells in which they are expressed and has a pH optimum in the acid range (pH 5.0 to 5.5), in keeping with a vacuolar origin (Frehner et al., 1984). 

Flere MAO first generates the dimethyl complex 6.26 from 6.25. This reaction, of course, can also be brought about by Me3Al. It is the subsequent reaction (i.e., the conversion of 6.26 to 6.27 that is of crucial importance. The high Lewis acidity of the aluminum centers in MAO enables it to abstract a CH3 group from 6.26 and sequesters it in the anion, [CH3-MAO]. Although 6.27 is shown as ionically dissociated species, probably the anion, [CH3-MAO], weakly coordinates to the zirconium atom. It is this coordinatively unsaturated species, 6.27, that promotes the alkene coordination and insertion that are necessary for polymerization activity. 

Pilot Plant Scale-Up. All of the pilot plant polymerizations to produce a rubber latex or a graft polymer were carried out in a 10-gal, glass-lined Pfaudler kettle. A 50-gal, glass-lined kettle was used to prepare MMA/St copolymer. EDTA was used in all pilot plant runs to sequester iron. 

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