Design of safe and sustainable process for the synthesis of hydrogen peroxide (H 2 O 2 ) is a very important subject from the viewpoint of green chemistry. Photocatalytic H 2 O 2 production with earth-abundant water and molecular oxygen (O 2 ) as resources is an ideal process. A successful system has been proposed based on an organic semiconductor; however, it suffers from poor photostability. Here we report an inorganic photocatalyst for H 2 O 2 synthesis. Visible light irradiation (λ >420 nm) of semiconductor BiVO 4 loaded with Au nanoparticles (Au/BiVO 4 ) in pure water with O 2 successfully produces H 2 O 2 . The bottom of the Bi-VO 4 conduction band (0.02 V vs. NHE, pH 0) is more positive than the one-electron reduction potential of O 2 (−0.13 V), while more negative than the two-electron reduction potential of O 2 (0.68 V). This thus suppresses one-electron reduction of O 2 and selectively promotes two-electron reduction of O 2 , resulting in efficient H 2 O 2 formation.

Ammonia (NH 3 ), which is an indispensable chemical, is produced by the Haber−Bosch process using H 2 and N 2 under severe reaction conditions. Although photocatalytic N 2 fixation with water under ambient conditions is ideal, all previously reported catalysts show low efficiency. Here, we report that a metalfree organic semiconductor could provide a new basis for photocatalytic N 2 fixation. We show that phosphorus-doped carbon nitride containing surface nitrogen vacancies (PCN-V), prepared by simple thermal condensation of the precursors under H 2 , produces NH 3 from N 2 with water under visible light irradiation. The doped P atoms promote water oxidation by the photoformed valence-band holes, and the N vacancies promote N 2 reduction by the conduction-band electrons. These phenomena facilitate efficient N 2 fixation with a solar-to-chemical conversion (SCC) efficiency of 0.1%, which is comparable to the average solar-tobiomass conversion efficiency of natural photosynthesis by typical plants. Thus, this metal-free catalyst shows considerable potential as a new method of artificial photosynthesis.

O6-Methylguanine-DNA methyltransferase (MGMT; DNA-O6-methylguanine:protein-L-cysteine S-methyltransferase, EC 2.1.1.63), a unique DNA repair protein present in most organisms, removes the carcinogenic and mutagenic adduct O6-alkylguanine from DNA by stoichiometrically accepting the alkyl group on a cysteine residue in a suicide reaction. The mammalian protein is highly regulated in both somatic and germ-line cells. In addition, the toxicity of certain alkylating drugs in tumor and normal cells is inversely related to the levels of this protein. The cDNA of the human gene, henceforth named MGMT, has been cloned in an expression vector on the basis of its rescue of a methyltransferase-deficient (ada-) Escherichia coli host. A 22-kDa active methyltransferase encoded entirely by the cDNA contains an amino acid sequence of 61 residues that bears 60-65% similarity with segments of E. coli methyltransferase (products of the ada and ogt genes), which encompass the alkyl-acceptor residues. The human cDNA has no sequence similarity with the ada and ogt genes, due in part to differences in codon usage, and shows no detectable homology with E. coli genomic DNA. However, it hybridizes with distinct restriction fragments of human, mouse, and rat DNAs. The lack of methyltransferase observed in many human cell lines is due to the absence of the MGMT gene or to lack of synthesis and/or stability of its 0.95-kilobase poly(A)+ RNA transcript.

O6-methylguanine-DNA methyltransferase (MGMT) is a ubiquitous protein responsible for repair of O6-alkylguanine, a mutagenic, carcinogenic and toxic lesion. To characterize the elements responsible for the regulation of the MGMT gene, a 2.6 kb Sstl fragment isolated from a genomic clone, was shown to contain 5' flanking sequences of the gene. The promoter activity of this fragment as well as various subfragments were tested in NIH 3T3 mouse fibroblasts by transient expression of the bacterial chloramphenicol acetyltransferase (CAT) gene linked to these fragments. Maximal promoter activity was observed in a 1.2 kb 3' terminal fragment, which contains the first untranslated exon. The transcription initiation site was identified in this fragment by primer extension and S1 mapping. Sequence analysis of this fragment showed the absence of TATA and CAAT boxes but an abundance of extremely GC-rich sequences, including ten GC hexanucleotide motifs 5'CCGCCC. Reduced CAT expression with the minimal promoter sequence suggests the presence of multiple regulatory elements.