Photocontrolled solid-phase extraction of guanine from complex samples using a novel photoresponsive molecularly imprinted polymer.

A novel photoresponsive molecularly imprinted polymer (MIP) was developed for the selective extraction of guanine from complex samples. The photoresponsive MIP was fabricated using guanine as the template, water-soluble 5-[(4-(methacryloyloxy)phenyl)diazenyl]isophthalic acid as the functional monomer, and water-soluble triethanolamine trimethacrylate as the cross-linker. The MIP displayed good selectivity toward guanine with a dissociation constant of (2.70 ± 0.16) × 10(-5) mol L(-1) in aqueous media. The density of the guanine-specific receptor sites in the MIP material was (4.49 ± 0.22)µmol g(-1). Quantitatively release and uptake of guanine by the MIP occurred with irradiation at 365 and 440 nm, respectively. The MIP could efficiently extract guanine from beer and then release it into aqueous media under photocontrol. This method could be used for selective separation and subsequent determination of a specific analytes from complex samples.

Rhodium(III)-catalyzed formal oxidative [4 + 1] cycloaddition of benzohydroxamic acids and α-diazoesters. A facile synthesis of functionalized benzolactams.

A Rh(III)-catalyzed oxidative [4 + 1] cycloaddition of benzohydroxamic acids and α-diazoesters is achieved to afford benzolactams in up to 93% yields. With the N-OAc amido moiety as a directing group, the ortho-C-H is selectively functionalized and the catalytic reaction exhibits excellent tolerance to different functional substituents. A notable rhodacyclic complex is isolated and structurally characterized, suggesting that C-H/N-H cyclometallation is a key step in the catalytic cycle.

Isolation of a full-length complementary DNA coding for human E1 alpha subunit of the pyruvate dehydrogenase complex.

A 1.5-kilobase cDNA clone for human pyruvate dehydrogenase E1 was isolated from a lambda gt11 expression library by screening with polyclonal antiserum to the E1 alpha subunit of the porcine pyruvate dehydrogenase complex, a polyclonal antibody against bovine pyruvate dehydrogenase complex and a synthetic oligonucleotide based on the known amino acid sequence of the amino-terminal of the bovine pyruvate dehydrogenase-E1 alpha subunit. Nucleotide sequence analysis of the cDNA revealed a 5'-untranslated sequence of 72 nucleotides, a translated sequence of 1170 nucleotides, and a 3'-untranslated sequence of 223 nucleotides with a poly(A) tail. The cDNA structure predicts a leader sequence of 29 amino acids and a mature protein of 362 amino acids comprising an amino-terminal peptide identical to that of the bovine E1 alpha subunit and three serine phosphorylation sites whose sequence was also identical to those in the bovine E1 alpha subunit. The translated sequence for the mature protein differs substantially from that described by Dahl et al. (Dahl, H. H., Hunt, S. M., Hutchison, W. M., and Brown, G. K. (1987) J. Biol. Chem. 262, 7398-7403) by virtue of a frameslip between bases 390 and 594. This amended sequence is confirmed by the presence of additional restriction sites for the enzymes NaeI and HaeII at the beginning and end, respectively, of this section. The leader sequence is typical for mitochondrial enzymes being composed of a combination of neutral and basic residues. The amino acid composition is strikingly similar to that of the bovine protein. This cDNA clone hybridizes with a 1.8-kilobase mRNA on a Northern blot analysis of human fibroblasts, and a second minor band of 4.4 kilobases is also detected.

Assignment of the alpha and beta chains of human propionyl-CoA carboxylase to genetic complementation groups.

Propionicacidemia is a metabolic disorder resulting from a deficiency of propionyl-CoA carboxylase activity. The enzyme is composed of two polypeptides: a 72,000-dalton alpha chain which contains the biotin ligand and a 56,000-dalton beta chain. It has been suggested that the two major complementation groups in this disorder, pccA and pccBC (with subgroups pccB and pccC), correspond to the genes encoding these two chains. To correlate gene product with complementation groups, 15 mutant and four normal human fibroblast strains were analyzed by [35S]methionine and [3H]biotin labeling. Immunoprecipitation and gel electrophoresis of the polypeptides revealed that alpha chains are synthesized by mutants of pccBC and both subgroups but not in four out of five pccA mutants. On the other hand, beta chains were detected only in pccB mutants. We suggest that pccA encodes the alpha chain of PCC while pccBC encodes the beta chain, and furthermore predict that the beta chain is unstable in the absence of the alpha chain.