Fluorescent carbon nanodots (C-dots; 4.3 AE 0.8 nm) from fresh tender ginger juice provide high suppression of the growth of human hepatocellular carcinoma cells (HepG2), with low toxicity to normal mammary epithelial cells (MCF-10A) and normal liver cells (FL83B). The inhibition is selective to HepG2 over other tested cancer cells, including human lung cancer cell line (A549), human breast cancer cell line (MDA-MB-231), and human cervical cancer cell line (HeLa). Western blot results reveal that the C-dots up-regulate the expression of p53 protein only in the HepG2 cell line. The 50% inhibiting concentration (IC 50 ) value of the C-dots on HepG2 cells is 0.35 mg mL À1 . Image cytometry results show significant uptake of C-dots by HepG2 cells that induce intracellular production of reactive oxygen species (ROS, 18.2-fold increased), while other cells remain almost the same in ROS levels after treatment with C-dots (1.11 mg mL À1 ). The C-dots trigger the pro-apoptotic factor to promote HepG2 cell apoptosis. The C-dots effectively inhibit the growth of tumors in nude mice (104 AE 14 vs. 3.7 AE 0.2 mg with and without treatment within 14 days).

The isoprenoid pathway is a versatile biosynthetic network leading to over 23,000 compounds. Similar to other biosynthetic pathways, the production of isoprenoids in microorganisms is controlled by the supply of precursors, among other factors. To engineer a host that has the capability to supply geranylgeranyl diphosphate (GGPP), a common precursor of isoprenoids, we cloned and overexpressed isopentenyl diphosphate (IPP) isomerase (encoded by idi) from Escherichia coli and GGPP synthase (encoded by gps) from the archaebacterium Archaeoglobus fulgidus. The latter was shown to be a multifunctional enzyme converting dimethylallyl diphosphate (DMAPP) to GGPP. These two genes and the gene cluster (crtBIYZW) of the marine bacterium Agrobacterium aurantiacum were introduced into E. coli to produce astaxanthin, an orange pigment and antioxidant. This metabolically engineered strain produces astaxanthin 50 times higher than values reported before. To determine the rate‐controlling steps in GGPP production, the IDI‐GPS pathway was compared with another construct containing idi, ispA (encoding farnesyl diphosphate (FPP) synthase in E. coli), and crtE (encoding GGPP synthase from Erwinia uredovora). Results show that the conversion from FPP to GGPP is the first bottleneck, followed sequentially by IPP isomerization and FPP synthesis. Removal of these bottlenecks results in an E. coli strain providing sufficient precursors for in vivo synthesis of isoprenoids. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 62: 235–241, 1999.

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This letter reports experimental work involving use of an in-plane electric field to induce morphological patterns in a thin polymer film. The film was first spin coated onto a glass wafer. Then, it was heated to above its glass transition temperature to achieve mobility in the fluid. An in-plane electric field was applied using two parallel electrodes, spaced 10 mm apart, whereupon the initially flat polymer/air interface lost stability and formed islands. The self-assembled islands exhibited a narrow size distribution and demonstrated spatial ordering. We attribute the pattern formation to a combined mechanism of minimization of combined interface energy and electrostatic energy.

Specific peptides contained within the extracellular layer, or jelly coat, of a sea urchin egg have been hypothesized to play an important role in fertilization, though separate accounting of the effects of chemoattraction, chemokinesis, sperm agglomeration and the other possible roles of the jelly coat have not been reported. In the present study, we used a microfluidic device that allowed determination of the differences in the diffusion coefficients of sperm of the purple sea urchin Arbacia punctulata subjected to two chemoattractants, namely the jelly coat and resact. Our objectives were twofold: (1) to experimentally determine and compare the diffusion coefficients of Arbacia punctulata spermatozoa in seawater, jelly coat solution and resact solution; and (2) to determine the effect of sea urchin sperm diffusion coefficient and egg size on the sperm-egg collision frequency using stochastic simulations. Numerical values of the diffusion coefficients obtained by diffusing the spermatozoa in seawater, resact solution and jelly coat solution were used to quantify the chemotactic effect. This allowed direct incorporation of known enlargements of the egg, and altered sperm diffusion coefficients in the presence of chemoattractant, in the stochastic simulations. Simulation results showed that increase in diffusion coefficient values and egg diameter values increased the collision frequency. From the simulation results, we concluded that type of sperm, egg diameter and diffusion coefficient are significant factors in egg fertilization. Increasing the motility of sperm appears to be the prominent role of the jelly coat.