Three fluorescent organic compounds-furocoumarin (FC), dansyl aniline (DA), and 7-hydroxycoumarin-3-carboxylic acid (CC)-are mixed to produce almost pure white light emission (WLE). This novel mixture is immobilised in silica aerogel and applied as a coating to a UV LED to demonstrate its applicability as a low-cost, organic coating for WLE via simultaneous emission. In ethanol solution and when immobilised in silica aerogel, the mixture exhibits a Commission Internationale d'Eclairage (CIE) chromaticity index of (0.27, 0.33). It was observed that a broadband and simultaneous emission involving coumarin carboxylic acid, furocoumarin and dansyl aniline played a vital role in obtaining a CIE index close to that of pure white light.
Titanium dioxide (TiO2) is added in sunscreens due to its ability to absorb ultraviolet (UV) light. However, upon irradiation of UV light, reactive oxygen species particularly hydroxyl radical which can damage human skin will be generated. In this study, lignin/TiO2 composites were employed to quench the hydroxyl radicals generated by the TiO2. The lignin was extracted from oil palm empty fruit bunch (OPEFB) via kraft and soda pulping processes. The kraft lignin composite was labelled as KL/TiO2 whereas the soda lignin composite was labelled as SL/TiO2. The lignins and the composites were characterized by FTIR, UV spectroscopy, 13C NMR, SEM, EDX, and XRD. The relative hydroxyl radical production of composites and TiO2 were compared through photo-oxidation of coumarin to 7-hydroxycoumarin as a test medium. The effect of types and amounts of lignin used were studied. The KL/TiO2 composite showed the least radical production due to higher phenolic hydroxyl content of kraft lignin. The activity of the hydroxyl radicals will be quenched when it abstract hydrogen atoms from the phenolic hydroxyl groups.
Variation in CYP2A6 levels and activity can be attributed to genetic polymorphism and, thus, functional characterization of allelic variants is necessary to define the importance of CYP2A6 polymorphism in humans. The aim of the present study was to investigate the reported alleles CYP2A6*15, CYP2A6*16, CYP2A6*21, and CYP2A6*22, in terms of the functional consequences of their mutations on the enzyme catalytic activity. With use of the wild-type CYP2A6 cDNA as template, site-directed mutagenesis was performed to introduce nucleotide changes encoding K194E substitution in CYP2A6*15, R203S substitution in CYP2A6*16, K476R substitution in CYP2A6*21, and concurrent D158E and L160I substitutions in CYP2A6*22. Upon sequence verification, the CYP2A6 wild-type and mutant constructs were individually coexpressed with NADPH-cytochrome P450 reductase in Escherichia coli. A kinetic study using a coumarin 7-hydroxylase assay indicated that CYP2A6*15 exhibited higher V(max) than the wild type, whereas all mutant constructs, except for variant CYP2A6*16, exhibited higher K(m) values. Analysis of the V(max)/K(m) ratio revealed that all mutants demonstrated 0.85- to 1.05-fold differences from the wild type, with the exception of variant CYP2A6*22, which only portrayed 39% of the wild-type intrinsic clearance. These data suggested that individuals carrying the CYP2A6*22 allele are likely to have lower metabolism of CYP2A6 substrate than individuals expressing CYP2A6*15, CYP2A6*16, CYP2A6*21, and the wild type.