Surface plasmon resonance imaging measurements of antibody arrays for the multiplexed detection of low molecular weight protein biomarkers

This paper describes a simple methodology for the creation of high-density multiplexed antibody arrays on gold surfaces that can be used to detect low molecular weight protein biomarkers with surface plasmon resonance imaging (SPRI). A one-step carbonyldiimidazole (CDI) surface reaction was utilized to attach antibodies onto alkanethiol-modified gold surfaces and characterized with polarization modulation FT-IR reflection absorption spectroscopy. The CDI chemistry was then employed to create an antibody microarray with array element sizes varying from 750 microm down to 200 microm. As a demonstration, a three-component antibody array was employed to detect two clinically important protein biomarkers, beta2-microglobulin (11.8 kDa) and cystatin C (13.4 kDa). SPRI measurements could simultaneously detect both of these small unlabeled proteins with no cross talk at solution concentrations from 300 nM down to 1 nM. In addition, the adsorption strengths of these biomarkers onto an antibody array were measured with SPRI and compared to those obtained from the kinetic analysis of single-channel angle shift SPR measurements.     

Ethylene glycol ethers and risks of spontaneous abortion and subfertility

Potential reproductive effects from occupational exposures to ethylene glycol ethers (EGE) are of concern since these organic solvents have been used widely in industry, and their reproductive toxicity has been well documented in animal studies. For determination of whether occupational exposure to EGE was associated with increased risks of spontaneous abortion and subfertility (i.e., taking more than 1 year of unprotected intercourse to conceive), a retrospective cohort study was conducted among workers at two semiconductor manufacturing plants in the eastern United States in 1980-1989 as part of a larger evaluation of reproductive health. Reproductive and occupational histories were obtained from interviews of semiconductor manufacturing workers and spouses. Assessment of potential exposure to mixtures containing EGE (none, low, medium, and high) was based on reported processes and company records. There were 1,150 pregnancies to semiconductor manufacturers, 561 to female employees and 589 to wives of male employees. Among female manufacturers, potential exposure to mixtures containing EGE was associated with increased risks of spontaneous abortion (relative risk in the high exposure group = 2.8; 95% confidence interval (CI) 1.4-5.6) and subfertility (odds ratio in the high exposure group = 4.6; 95% CI 1.6-13.3). Both of these risks exhibited a dose-response relation with potential EGE exposure (p for trend = 0.02). Among spouses of male manufacturers potentially exposed to mixtures containing EGE, there was no increased risk of spontaneous abortion, but there was a nonsignificant increased risk of subfertility (odds ratio in the high exposure group = 1.7; 95% CI 0.7-4.3).     

A chromosome 14q11/TCR alpha/delta specific yeast artificial chromosome improves the detection rate and characterization of chromosome abnormalities in T-lymphoproliferative disorders

The rate of detection of chromosome abnormalities in T-cell proliferations is lower than that observed in B-cell malignancies. The former frequently involve the TCR alpha/delta locus at chromosome band 14q11. We have identified a YAC encompassing 70% of the TCR alpha/delta locus, which has been used as a fluorescence in situ hybridization probe to detect chromosome rearrangements involving 14q11, both at metaphase and within interphase nuclei, in patients with a variety of T-lymphoproliferative disorders. Its use allowed detection of previously unsuspected TCR alpha/delta rearrangements in 4/13 (30%) immature T-lineage acute leukemias, including two t(10;14) and 2 minor inversion 14s. It also clarified interpretation of complex chromosome 14 abnormalities in mature T-cell proliferations (T-prolymphocytic leukemia and ataxia telangiectasia). Use of this probe will aid the detection and characterization of abnormalities involving the TCR alpha/delta locus, particularly in cases with normal or complex karyotypes and in those proliferations for which mitoses are difficult to obtain.     

Intermediate-risk endometrial cancer. A management approach

In the United States, endometrial cancer remains the most frequently diagnosed tumor of the female genital tract. The Gynecologic Oncology Group (GOG) has previously included patients with disease confined to the uterus and moderately or poorly differentiated tumors that invade at least half the myometrium in protocols designed for "intermediate levels of risk". Although such patients are ideally staged surgically, the role of adjuvant therapies such as postoperative pelvic irradiation remains unclear. This report offers a management approach for these women based on opportunities for enhanced local control with an acceptable level of morbidity according to supportive data from the available literature.     

Active network management for electrical distribution systems: problem formulation,benchmark, and approximate solution

With the increasing share of renewable and distributed generation in electrical distribution systems, active network management (ANM) becomes a valuable option for a distribution system operator to operate his system in a secure and cost-effective way without relying solely on network reinforcement. ANM strategies are short-term policies that control the power injected by generators and/or taken off by loads in order to avoid congestion or voltage issues. While simple ANM strategies consist in curtailing temporary excess generation, more advanced strategies rather attempt to move the consumption of loads to anticipated periods of high renewable generation. However, such advanced strategies imply that the system operator has to solve large-scale optimal sequential decision-making problems under uncertainty. The problems are sequential for several reasons. For example, decisions taken at a given moment constrain the future decisions that can be taken, and decisions should be communicated to the actors of the system sufficiently in advance to grant them enough time for implementation. Uncertainty must be explicitly accounted for because neither demand nor generation can be accurately forecasted. We first formulate the ANM problem, which in addition to be sequential and uncertain, has a nonlinear nature stemming from the power flow equations and a discrete nature arising from the activation of power modulation signals. This ANM problem is then cast as a stochastic mixed-integer nonlinear program, as well as second-order cone and linear counterparts, for which we provide quantitative results using state of the art solvers and perform a sensitivity analysis over the size of the system, the amount of available flexibility, and the number of scenarios considered in the deterministic equivalent of the stochastic program. To foster further research on this problem, we make available at http://www.montefiore.ulg.ac.be/~anm/ three test beds based on distribution networks of 5, 33, and 77 buses. These test beds contain a simulator of the distribution system, with stochastic models for the generation and consumption devices, and callbacks to implement and test various ANM strategies.     

Long-range surface plasmon resonance imaging for bioaffinity sensors

A novel bioaffinity sensor based on surface plasmon resonance (SPR) imaging measurements of a multiple-layered structure that supports the generation of long-range surface plasmons (LRSPs) at the water-metal interface is reported. LRSPs possess longer surface propagation lengths, higher electric field strengths, and sharper angular resonance curves than conventional surface plasmons. LRSPR imaging is a version of SPR imaging that requires a symmetric dielectric arrangement around the gold thin film. This arrangement is created using an SF10 prism/Cytop/gold/water multilayer film structure where Cytop is an amorphous fluoropolymer with a refractive index very close to that of water. LRSPR imaging experiments are performed at a fixed incident angle and lead to an enhanced response for the detection of surface binding interactions. As an example, the hybridization adsorption of a 16-mer single-stranded DNA (ssDNA) onto a two-component ssDNA array was monitored with LRSPR imaging. The ssDNA array was created using a new fabrication technology appropriate for the LRSPR multilayers.     

Surface Plasmon Resonance Imaging Measurements of Electrostatic Biopolymer Adsorption onto Chemically Modified Gold Surfaces

A combination of in situ and ex situ surface plasmon resonance (SPR) imaging experiments is used to characterize the differential electrostatic adsorption of proteins and synthetic polypeptides onto photopatterned monolayers at gold surfaces. The nonspecific electrostatic adsorption of proteins onto negatively charged self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid (MUA) is found to depend on the protein pI, solution ionic strength, and solution pH. The pH dependence of the electrostatic adsorption of the protein avidin onto a MUA SAM indicates that a full monolayer adsorbs at a solution pH greater than 5.0, and an "effective pK(a)" of 3.6 is determined for the avidin adsorption. This effective pK(a) is a combination of the pK(a) of the MUA monolayer and the ion pairing adsorption coefficient for the avidin. Additional SPR imaging experiments show that the electrostatic adsorption of the synthetic polypeptide poly-l-lysine (PL) onto a MUA SAM varies with molecular weight, forming a full PL monolayer for polypeptides with more than 67 lysine residues.     

An integrated semantics for reasoning about SysML design models using refinement

SysML is a variant of UML for systems design. Several formalisations of SysML (and UML) are available. Our work is distinctive in two ways: a semantics for refinement and for a representative collection of elements from the UML4SysML profile (blocks, state machines, activities, and interactions) used in combination. We provide a means to analyse and refine design models specified using SysML. This facilitates the discovery of problems earlier in the system development lifecycle, reducing time, and costs of production. Here, we describe our semantics, which is defined using a state-rich process algebra and implemented in a tool for automatic generation of formal models. We also show how the semantics can be used for refinement-based analysis and development. Our case study is a leadership-election protocol, a critical component of an industrial application. Our major contribution is a framework for reasoning using refinement about systems specified by collections of SysML diagrams.     

Near infrared surface plasmon resonance phase imaging and nanoparticle-enhanced surface plasmon resonance phase imaging for ultrasensitive protein and DNA biosensing with oligonucleotide and aptamer microarrays

The techniques of surface plasmon resonance-phase imaging (SPR-PI) and nanoparticle-enhanced SPR-PI have been implemented for the multiplexed bioaffinity detection of proteins and nucleic acids. The SPR-PI experiments utilized a near-infrared 860 nm light emitting diode (LED) light source and a wedge depolarizer to create a phase grating on a four-element single-stranded DNA (ssDNA) microarray; bioaffinity adsorption onto the various microarray elements was detected via multiplexed real time phase shift measurements. In a first set of demonstration experiments, an ssDNA aptamer microarray was used to directly detect thrombin at concentrations down to 100 pM with SPR-PI. Two different ssDNA aptamers were used in these experiments with two different Langmuir adsorption coefficients, K(A1) = 4.4 × 10(8) M(-1) and K(A2) = 1.2 × 10(8) M(-1). At concentrations below 1 nM, the equilibrium phase shifts observed upon thrombin adsorption vary linearly with concentration with a slope that is proportional to the appropriate Langmuir adsorption coefficient. The observed detection limit of 100 pM is approximately 20 times more sensitive than that observed previously with SPRI. In a second set of experiments, two short ssDNA oligonucleotides (38mers) were simultaneously detected at concentrations down to 25 fM using a three-sequence hybridization format that employed 120 nm DNA-modified silica nanoparticles to enhance the SPR-PI signal. In this first demonstration of nanoparticle-enhanced SPR-PI, the adsorbed silica nanoparticles provided a greatly enhanced phase shift upon bioaffinity adsorption due to a large increase in the real component of the interfacial refractive index from the adsorbed nanoparticle. As in the case of SPR-PI, the detection limit of 25 fM for nanoparticle-enhanced SPR-PI is approximately 20 times more sensitive than that observed previously with nanoparticle-enhanced SPRI.