Carboxyl Cellular

One method (116) of producing cellular polymers from a variety of latexes uses primarily latexes of carboxylated styrene—butadiene copolymers, although other elastomers such as acryUc elastomers, nitrile mbber, and vinyl polymers can be employed. 

The biochemical basis for the toxicity of mercury and mercury compounds results from its ability to form covalent bonds readily with sulfur. Prior to reaction with sulfur, however, the mercury must be metabolized to the divalent cation. When the sulfur is in the form of a sulfhydryl (— SH) group, divalent mercury replaces the hydrogen atom to form mercaptides, X—Hg— SR and Hg(SR)2, where X is an electronegative radical and R is protein (36). Sulfhydryl compounds are called mercaptans because of their ability to capture mercury. Even in low concentrations divalent mercury is capable of inactivating sulfhydryl enzymes and thus causes interference with cellular metaboHsm and function (31—34). Mercury also combines with other ligands of physiological importance such as phosphoryl, carboxyl, amide, and amine groups. It is unclear whether these latter interactions contribute to its toxicity (31,36). 

Much of protein engineering concerns attempts to explore the relationship between protein stmcture and function. Proteins are polymers of amino acids (qv), which have general stmcture +H3N—CHR—COO , where R, the amino acid side chain, determines the unique identity and hence the stmcture and reactivity of the amino acid (Fig. 1, Table 1). Formation of a polypeptide or protein from the constituent amino acids involves the condensation of the amino-nitrogen of one residue to the carboxylate-carbon of another residue to form an amide, also called peptide, bond and water. The linear order in which amino acids are linked in the protein is called the primary stmcture of the protein or, more commonly, the amino acid sequence. Only 20 amino acid stmctures are used commonly in the cellular biosynthesis of proteins (qv). 

What is true for acetic acid is also true for other carboxylic acids at the ph ysiological pH that exists inside cells, carboxylic acids are almost entirely dissociated. To reflect this fact, we always refer to cellular carboxylic acids by the name of their anion—acetate, lactate, citrate, and so forth, rather than acetic acid, lactic acid, and citric acid. 

In addition to effects on biochemical reactions, the inhibitors may influence the permeability of the various cellular membranes and through physical and chemical effects may alter the structure of other subcellular structures such as proteins, nucleic acid, and spindle fibers. Unfortunately, few definite examples can be listed. The action of colchicine and podophyllin in interfering with cell division is well known. The effect of various lactones (coumarin, parasorbic acid, and protoanemonin) on mitotic activity was discussed above. Disturbances to cytoplasmic and vacuolar structure, and the morphology of mitochondria imposed by protoanemonin, were also mentioned. Interference with protein configuration and loss of biological activity was attributed to incorporation of azetidine-2-carboxylic acid into mung bean protein in place of proline. 

Yang, J. and Kramer, J.M. (1994) In vitro mutagenesis of Caenorhabditis elegans cuticle collagens identifies a potential subtilisin-like protease cleavage site and demonstrates that carboxyl domain disulfide bonding is required for normal function but not assembly. Molecular and Cellular Biology 14, 2722-2730. 

DCIA has been used to label numerous proteins and other biomolecules, including phospholipids (Silvius et al., 1987), to study the interaction of mRNA with the 30S ribosomal subunit (Czworkowski et al., 1991), in the investigation of cellular thiol components by flow cytometry (Durand and Olive, 1983), in the detection of carboxylate compounds using peroxyoxalate chemiluminescence (Grayeski and DeVasto, 1987), and for general sulfhydryl labeling (Sippel, 1981). 

In neurons and non-neuronal cells, kinesin is associated with a variety of MBOs, ranging from synaptic vesicles to mitochondria to lysosomes. In addition to its role in fast axonal transport and related phenomena in non-neuronal cells, kinesin appears to be involved in constitutive cycling of membranes between the Golgi and endoplasmic reticulum. However, kinesin is not associated with all cellular membranes. For example, the nucleus, membranes of the Golgi complex and the plasma membrane all appear to lack kinesin. Kinesin interactions with membranes are thought to involve the light chains and carboxyl termini of heavy chains. However, neither this selectivity nor the molecular basis for binding of kinesin and other motors to membranes is well understood. 

In the E-Screen bioassay, LAS was not effective in promoting cell proliferation (Table 7.3.3). This compound was tested at concentrations of up to 100 pM with no evidence of cellular toxicity. The antiestrogenic effect of this compound was also measured but all samples tested were negative. Because it has been suggested that surfactants of the alkylbenzene sulfonate type are readily degradable and transformed into sulfophenyl carboxylates or SPCs, an important number of SPCs were assayed in the E-Screen test. These SPCs did not induce cell proliferation of MCF7 cells. 

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