Enzymatically amplified surface plasmon resonance imaging detection of DNA by exonuclease III digestion of DNA microarrays

This paper describes a novel approach utilizing the enzyme exonuclease III in conjunction with 3'-terminated DNA microarrays for the amplified detection of single-stranded DNA (ssDNA) with surface plasmon resonance (SPR) imaging. When ExoIII and target DNA are simultaneously introduced to a 3'-terminated ssDNA microarray, hybridization adsorption of the target ssDNA leads to the direction-dependent ExoIII hydrolysis of probe ssDNA strands and the release of the intact target ssDNA back into the solution. Readsorption of the target ssDNA to another probe creates a repeated hydrolysis process that results over time in a significant negative change in SPR imaging signal. Experiments are presented that demonstrate the direction-dependent surface enzyme reaction of ExoIII with double-stranded DNA as well as this new enzymatically amplified SPR imaging process with a 16-mer target ssDNA detection limit of 10-100 pM. This is a 10(2)-10(3) improvement on previously reported measurements of SPR imaging detection of ssDNA based solely on hybridization adsorption without enzymatic amplification.     

Circadian rhythmic fractal scaling of heart rate variability in health and coronary artery disease

BACKGROUND: In clinical cardiology, heart rate variability is a putative index of autonomic cardiovascular function. Signs of reduced vagal activity are not only associated with an enhanced risk of sudden cardiac death, but such impaired heart rate variability became a new predictor of sudden cardiac death and other mortality in patients with a variety of diseased states. HYPOTHESIS: It is postulated (1) that the time structure (chronome) of heart rate variability in clinical health includes a circadian rhythm and deterministic chaos, the latter gauged by the correlation dimensions of RR intervals; and (2) that this chronome is altered in patients with coronary artery disease (CAD). METHODS: From 24-h Holter records of 11 healthy controls and 10 patients with CAD, 500-s sections around 02:00, 06:00, 10:00, 14:00, 18:00 and 22:00 hours were analyzed for smoothed RR intervals sampled at 4 Hz. Correlation integrals were estimated for embedding dimensions from 1 to 20 with a 1.0-s time lag, using an algorithm modified from Grassberger and Procaccia. The Wilcoxon signed-rank test compares circadian end points assessed by cosinor between the CAD patients and age-matched controls. RESULTS: A circadian rhythm characterizes the correlation dimension of healthy subjects peaking during the night (p < 0.005). Patients with CAD have a lowered correlation dimension (p < 0.05) and an altered circadian variation which requires the consideration of an approximately 12-h (circasemidian) component. CONCLUSION: The results demonstrate the sensitivity of circadian rhythms for the detection of disease. A partial 24- to 12-h (circadian-to-circasemidian) frequency multiplication (or partial variance transposition) in CAD of the correlation dimension, apart from being a potential clue to the etiology of the disease, adds a new feature to a chronocardiology combining, with the fractal scaling, an assessment of circadian and circasemidian components as measures of predictable variability to be tested for use in diagnosis, prognosis, and as putative guides to treatment timing.     

A Design-Based Structural Test Method for a Switched-Resistor DAC

In this paper, a design-based structural testing method is presented to enable a fast, low cost test for a switched-resistor digital-to-analogue converter (DAC). A 24-bit stereo DAC is used to demonstrate this. After schematic-level simulations and experimental verification, it is found that the dynamic parameter THD can be predicted by the static test. Practical production wafer test and final test results evaluate this structural test method by comparing it with the traditional THD test method. In this paper the simulation results, the relevant measurement results, and the testing results are discussed. Finally, the application recommendations are given.

Detection of protein biomarkers using RNA aptamer microarrays and enzymatically amplified surface plasmon resonance imaging

A methodology for the detection of protein biomarkers at picomolar concentrations that utilizes surface plasmon resonance imaging (SPRI) measurements of RNA aptamer microarrays is developed. The adsorption of proteins onto the RNA microarray is detected by the formation of a surface aptamer-protein-antibody complex. The SPRI response signal is then amplified using a localized precipitation reaction catalyzed by the enzyme horseradish peroxidase that is conjugated to the antibody. This enzymatically amplified SPRI methodology is first characterized by the detection of human thrombin at a concentration of 500 fM; the appropriate thrombin aptamer for the sandwich assay is identified from a microarray of three potential thrombin aptamer candidates. The SPRI method is then used to detect the protein vascular endothelial growth factor (VEGF) at a biologically relevant concentration of 1 pM. VEGF is a signaling protein that has been used as a serum biomarker for rheumatoid arthritis, breast cancer, lung cancer, and colorectal cancer and is also associated with age-related macular degeneration.     

Psychosocial factors and the development of breast cancer: A meta-analysis.

A meta-analysis examined the relationship between psychosocial factors and the development of breast cancer. Average effect sizes (Hedges's g) were calculated from 46 studies for 8 major construct categories: anxiety/depression, childhood family environment, conflict-avoidant personality, denial/repression coping, anger expression, extraversion-introversion, stressful life events, and separation/loss. Significant effect sizes were found for denial/repression coping (g?=?.38), separation/loss experiences (g?=?.29), and stressful life events (g?=?.25). Although conflict-avoidant personality style was also significant (g?=?.19), the effect size was less robust, and a moderate number of future studies with null results would reduce the significance. Results overall support only a modest association between specific psychosocial factors and breast cancer and are contrary to the conventional wisdom that personality and stress influence the development of breast cancer. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Wafer-scale fabrication of nanofluidic arrays and networks using nanoimprint lithography and lithographically patterned nanowire electrodeposition gold nanowire masters

Wafer scale (cm(2)) arrays and networks of nanochannels were created in polydimethylsiloxane (PDMS) from a surface pattern of electrodeposited gold nanowires in a master-replica process and characterized with scanning electron microscopy (SEM), atomic force microscopy (AFM), and fluorescence imaging measurements. Patterns of gold nanowires with cross-sectional dimensions as small as 50 nm in height and 100 nm in width were prepared on silica substrates using the process of lithographically patterned nanowire electrodeposition (LPNE). These nanowire patterns were then employed as masters for the fabrication of inverse replica nanochannels in a special formulation of PDMS. SEM and AFM measurements verified a linear correlation between the widths and heights of the nanowires and nanochannels over a range of 50 to 500 nm. The PDMS replica was then oxygen plasma-bonded to a glass substrate in order to create a linear array of nanofluidic channels (up to 1 mm in length) filled with solutions of either fluorescent dye or 20 nm diameter fluorescent polymer nanoparticles. Nanochannel continuity and a 99% fill success rate was determined from the fluorescence imaging measurements, and the electrophoretic injection of both dye and nanoparticles in the nanochannel arrays was also demonstrated. Employing a double LPNE fabrication method, this master-replica process was also used to create a large two-dimensional network of crossed nanofluidic channels.     

Chemical and genetic wrappers for improved phage and RNA display

An Achilles heel inherent to all molecular display formats, background binding between target and display system introduces false positives into screens and selections. For example, the negatively charged surfaces of phage, mRNA, and ribosome display systems bind with unacceptably high nonspecificity to positively charged target molecules, which represent an estimated 35% of proteins in the human proteome. Here we report the first systematic attempt to understand why a broad class of molecular display selections fail, and then solve the underlying problem for both phage and RNA display. Firstly, a genetic strategy was used to introduce a short, charge-neutralizing peptide into the solvent-exposed, negatively charged phage coat. The modified phage (KO7(+)) reduced or eliminated nonspecific binding to the problematic high-pI proteins. In the second, chemical approach, nonspecific interactions were blocked by oligolysine wrappers in the cases of phage and total RNA. For phage display applications, the peptides Lys(n) (where n=16 to 24) emerged as optimal for wrapping the phage. Lys(8), however, provided effective wrappers for RNA binding in assays against the RNA binding protein HIV-1 Vif. The oligolysine peptides blocked nonspecific binding to allow successful selections, screens, and assays with five previously unworkable protein targets.     

A brief review of environmentally benign antifouling and foul-release coatings for marine applications

Antifouling coatings for ship hulls are a very important topic in coating research. They are essential with respect to fuel consumption of ships: without antifouling coating, biological species start to adhere to the ship’s exterior, leading to a gradual increase in fuel consumption. To date, the working principle of most of the paint systems applied is based on slow release of toxins in time (self-polishing coatings). In this article, we discuss the environmental impact of marine antifouling coatings based on quantitative data available from literature. In addition, we critically review hydrophilic antifouling and hydrophobic foul-release coatings as toxin-free alternatives and discuss their potential for replacing self-polishing coatings.     

Epidemiological study of Campylobacter spp. in broilers: source, time of colonization, and prevalence

From October 1993 to August 1994, broiler chickens in four grow-out houses, two previously used (houses 1 and 2) and two newly constructed (houses 3 and 4), were used in a study to determine the source, time of infection, and prevalence of Campylobacter spp. Cecal droppings and cecal samples were obtained from the broilers. Samples were also obtained from water, feed, litter, soil, fans, and workers' boots. Samples were obtained from domestic animals and wildlife species (rectal swabs), including insects, on or near the premises. Broilers in houses 2, 3, and 4 became infected in the second or third week and were fully colonized by day 42. Campylobacter appeared in house 1 during week 2 in a low percentage of the birds, disappearing by the fourth week. Isolates were also recovered from domestic pigs and water on this farm. In house 3, the organism was isolated from workers' boots and a wild bird prior to isolation from the broilers. Following isolation from cecal droppings, the organism was isolated from water, feed, litter, feathers, flies, cattle, feces, and wild animals. In house 2, Campylobacter was isolated from cattle feces and wild birds prior to week 5, when the broilers first became infected, and thereafter from water, feed, insect, and wildlife, and cecal droppings. It was subsequently isolated from workers' boots, cattle feces, feathers, insects, and other wildlife. All ceca taken from 20 birds each from houses 2 and 3 were positive at time of slaughter (day 49). All ceca from house 1 were negative. No ceca were collected from birds originating in house 4. No specific source could be identified from the samples obtained, although apparently the organism permeates the environment and several potential sources are discussed in this paper.