Evaluation of photoluminescence quenching for assessing the binding of nitroaromatic compounds to a tyrosyl bolaamphiphile self-assembly.

Quenching of a fluorophore is significantly influenced by the molecular structure of the quencher. In this study, photoluminescence quenching by nitroaromatic compounds was evaluated to assess the molecular interaction between nitroaromatic molecules and the photoluminescent tyrosyl bolaamphiphile self-assembly, a nanoscale optical photoluminescent probe. Both the aromatic structure and hydrophilic functional groups of the nitroaromatic quencher molecules significantly enhanced the binding of quencher molecules to the photoluminescent probe.

Effect of mild-thiol reducing agents and alpha2,3-sialyltransferase expression on secretion and sialylation of recombinant EPO in CHO cells.

We have previously reported that N-acetylcysteine (NAC) not only delayed apoptosis but also enhanced the production of recombinant erythropoietin (EPO) in Chinese hamster ovary (CHO) cell culture. To investigate the production enhancement mechanism, the effects of similar thiolreducing agents were studied. Intriguingly, all mild reducing agents examined including mercaptoethanesulfonic acid (MESNA), thiolactic acid (TLA), and thioglycolate (TG) were shown to block apoptosis and increase EPO production.

Nonmonotonic Size-Dependent Carrier Mobility in PbSe Nanocrystal Arrays.

On the basis of a tight binding system-bath model, we investigated carrier mobility of PbSe nanocrystal (NC) arrays as a function of NC size and inter-NC separation. The size-dependent trend of calculated carrier mobilities are in excellent agreement with recent experimental measurements: electron mobility increased up to NC diameter of ∼6 nm and then decreased for larger NCs, whereas hole mobility showed a monotonic size-dependency. Carrier mobility increase was associated with reduced activation energy that governs charge-transfer processes.

The anti-biofouling effect of polyphenols against Streptococcus mutans.

Biofouling is a process of surface colonization by microorganisms through cell adhesion and production of extracellular polymers (polysaccharides and proteins). It often causes serious problems in the chemical, medical and pharmaceutical industries. Recently, it was demonstrated that some natural phenolic compounds found in plants and vegetables have an antibiofouling effect, reducing formation of biofilm by Gram-negative bacteria.

Enhanced sialylation of recombinant erythropoietin in CHO cells by human glycosyltransferase expression.

Sialylation, the attachment of sialic acid residues to a protein, can affect the biological activity and in vivo circulatory half-life of glycoproteins. Human alpha2,3- sialyltransferase (alpha2,3-ST) and beta1,4-galactosyltransferase (beta1,4-GT) are responsible for terminal sialylation and galactosylation, respectively. Enhanced sialylation of human erythropoietin (EPO) by the expression of alpha2,3-ST and beta1,4-GT was achieved using recombinant Chinese hamster ovary (CHO) cells (EC1).

Enhanced sialylation of recombinant erythropoietin in genetically engineered Chinese-hamster ovary cells.

Sialic acid, the terminal sugar in N-linked complex glycans, is usually found in glycoproteins and plays a major role in determining the circulatory lifespan of glycoproteins. In the present study we attempted to enhance the sialylation of recombinant EPO (erythropoietin) in CHO (Chinese-hamster ovary) cells. To enhance EPO sialylation, we introduced human alpha2,3-ST (alpha2,3-sialyltransferase) and CMP-SAS (CMP-sialic acid synthase) into recombinant human EPO-producing CHO cells.

Purification, characterization, and cloning of a Spodoptera frugiperda Sf9 beta-N-acetylhexosaminidase that hydrolyzes terminal N-acetylglucosamine on the N-glycan core.

Paucimannosidic glycans are often predominant in N-glycans produced by insect cells. However, a beta-N-acetylhexosaminidase responsible for the generation of paucimannosidic glycans in lepidopteran insect cells has not been identified. We report the purification of a beta-N-acetylhexosaminidase from the culture medium of Spodoptera frugiperda Sf9 cells (Sfhex).

N-glycan structures of human transferrin produced by Lymantria dispar (gypsy moth) cells using the LdMNPV expression system.

N-glycan structures of recombinant human serum transferrin (hTf) expressed by Lymantria dispar (gypsy moth) 652Y cells were determined. The gene encoding hTf was incorporated into a Lymantria dispar nucleopolyhedrovirus (LdMNPV) under the control of the polyhedrin promoter. This virus was then used to infect Ld652Y cells, and the recombinant protein was harvested at 120 h postinfection.