Isolation and characterization of the alkane-inducible NADPH-cytochrome P-450 oxidoreductase gene from Candida tropicalis. Identification of invariant residues within similar amino acid sequences of divergent flavoproteins.

The gene coding for the Candida tropicalis NADPH-cytochrome P-450 oxidoreductase (CPR, NADPH: ferricytochrome oxidoreductase, EC 1.6.2.4) was isolated by immunoscreening of a C. tropicalis lambda gt11 expression library and colony hybridization of a C. tropicalis genomic library. The C. tropicalis CPR gene produces a 2.35-kilobase mRNA transcript, levels of which were shown to be increased 16-fold in cells grown on tetradecane relative to cells grown on glucose as the sole carbon source. A 3-kilobase DNA fragment was sequenced, including 554 and 397 base pairs of 5'- and 3'-noncoding sequence, respectively. A single open reading frame of 2040 base pairs was identified and predicts a 76,683-Da polypeptide of 680 amino acid residues. The deduced C. tropicalis CPR amino acid sequence was compared with each of the CPR sequences reported from other organisms and invariant residues were identified. Multiple pairwise alignments of divergent members of protein families, previously recognized for their sequence similarities in their respective binding domains for FMN, FAD, and NADPH, have allowed identification of a subset of these invariant residues. From these analyses we infer the importance of 25 of the 680 amino acid residues

Advanced upconverter systems with spectral and geometric concentration for high upconversion efficiencies

In this paper we present an advanced upeonverter system concept to reduce the sub-bandgap losses of silicon solar cells. We address the issue of the narrow absorption range of common upconverter materials. This problem can be overcome by the combination of the upconverter with a broadly absorbing fluorescent material, which emits in the absorption range of the upconverter. However, possible fluorescent materials also absorb in the emission range of the upconverter. We therefore propose an advanced system setup, which avoids unwanted absorption by separating upconverter and fluorescent material with a selectively reflective photonic structure. The incorporation of the fluorescent material in a fluorescent concentrator allows for additional geometric concentration increasing the efficiency of the upconversion process. We estimate that a total system efficiency of up to 25% could be possible with an Er based upconverting system and a silicon solar cell