Facile preparation of visible light-sensitive layered g-C3N4 for photocatalytic removal of organic pollutants.

The graphite-phase carbon nitride (g-C3N4) photocatalytic materials were prepared by one-step calcination method to degrade methylene blue (MB) and potassium butyl xanthate (PBX) under visible light irradiation. The prepared g-C3N4 photocatalytic materials were investigated in detail by various characterizations, and the experiments showed that the graphitic phase carbon nitride photocatalytic materials were successfully prepared by the one-step calcination method. The material possesses excellent optical properties and strong visible light absorption, thus achieving photocatalytic degradation of MB and PBX. The catalyst dosage, pH, the initial concentration of pollutants have important effects on photocatalytic activity of MB and PBX. The photocatalytic degradation efficiency was 98.99% for MB and 96.83% for PBX under the optimal conditions (catalyst dosage, initial pollutant concentration and pH value were 500 mg L-1, 20 mg L-1 and 7, respevtively). The photocatalytic mechanisms on MB and PBX were elucidated. ·OH was the key specie for MB, while ·O2- was the key specie for PBX. This study advances the development of photocatalytic technology for mineral wastewater.

Structure, genomic organization, and phylogenetic implications of six new VH families in the channel catfish.

To define members of previously unknown VH gene families, a channel catfish immunoglobulin heavy chain cDNA library was constructed and screened with probes specific for the seven known catfish VH families. Reiterative screening and sequence studies defined six new VH families, designated VH8-VH13, which brings the total number of VH families in the catfish to 13. This is the highest number of VH families presently defined in a lower vertebrate. Sequence comparisons indicate there is extensive diversity between members of different families with the greatest variability encoded within the complementarity determining regions. Genomic libraries were screened, and germline VH segments representing each of these new families were identified. The VH segments are closely linked and interspersed with members of different VH families. Each of these germline gene segments shared characteristic structural features: an upstream region that contained transcriptional regulatory elements, a leader sequence split by a short intron, an open reading frame encoding readily identified framework and complementarity determining regions, and a terminal recombination signal sequence consisting of a consensus heptamer, a 22-24 bp spacer with conserved 5'- and 3'-ends, and a consensus A-rich nonamer. Southern blot analyses estimate the number of members within these new families ranges from small (2-7 members in VH9, VH10, and VH12) to medium (9-13 members in VH8, VH11, and VH13). Thus, there are between 165 and 200 germline VH segments represented by these combined 13 families with present analyses indicating that perhaps one-half of these are pseudogenes. Phylogenetic comparisons indicate that members of these different catfish VH families cluster within Groups C and D of vertebrate VH genes. These analyses also indicate that Group D is represented by two different branches and both branches include VH families from different lineages of bony fish that diverged early in vertebrate phylogeny.

The nucleotide targets of somatic mutation and the role of selection in immunoglobulin heavy chains of a teleost fish.

Sequence analysis of H chain cDNA derived from the spleen of an individual catfish has shown that somatic mutation occurs within both the VH- and JH-encoded regions. Somatic mutation preferentially targets G and C nucleotides with approximately balanced frequencies, resulting in the predominant accumulation of G-to-A and C-to-T substitutions that parallel the activation-induced cytidine deaminase nucleotide exchanges known in mammals. The overall mutation rate of A nucleotides is not significantly different from that expected by sequence-insensitive mutations, and a significant bias exists against mutations occurring in T. Targeting of mutations is dependent upon the sequence of neighboring nucleotides, allowing statistically significant hotspot motifs to be identified. Dinucleotide, trinucleotide, and RGYW analyses showed that mutational targets in catfish are restricted when compared with the spectrum of targets known in mammals. The preferential targets for G and C mutation are the central GC positions in both AGCT and AGCA. The WA motif, recognized as a mammalian hotspot for A mutations, was not a significant target for catfish mutations. The only significant target for A mutations was the terminal position in AGCA. Lastly, comparisons of mutations located in framework region and CDR codons coupled with multinomial distribution studies found no substantial evidence in either independent or clonally related VDJ rearrangements to indicate that somatic mutation coevolved with mechanisms that select B cells based upon nonsynonymous mutations within CDR-encoded regions. These results suggest that the principal role of somatic mutation early in phylogeny was to diversify the repertoire by targeting hotspot motifs preferentially located within CDR-encoded regions.

Vascular endothelial growth factor gene therapy in improvement of skin paddle survival in a rat TRAM flap model.

The use of growth factors in inducing angiogenesis and enhancing flap viability has provided promising results. Targeted gene therapy has evolved in hopes of increasing the longevity and effectiveness of these growth factor treatments. The purpose of this study was to examine the effect of preoperative treatment by vascular endothelial growth factor (VEGF) plasmid DNA on the survival of the skin paddle in a rat pedicled TRAM flap model. In part one of the study, VEGF plasmid DNA incorporated with lipofectamine was injected into the subcutaneous fascial layer of the upper abdominal walls of the rats. At 4 days postoperatively, biopsies were taken from the injected area for histology and VEGF protein quantification. In part two of the study, the rats were divided into three groups. In one experimental group, the VEGF plasmid DNA was injected into the subcutaneous fascial layer in the area where the TRAM flap would be elevated. In two control groups, the plasmid without VEGF DNA and saline were injected. The flaps were raised and replaced 4 days after injection. Flap survival was examined. Results showed that tissue receiving VEGF plasmid DNA injection revealed new vessel sprouting. The VEGF levels in these tissues were significantly higher than in the tissue not receiving VEGF plasmid DNA. In flap survival, the mean viable area of the skin paddles receiving preoperative VEGF plasmid DNA injection was significantly larger than that of flaps receiving no VEGF plasmid DNA and saline injection. This study demonstrated that preoperative subcutaneous injection of VEGF plasmid DNA could induce angiogenesis and improve TRAM skin paddle survival.