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Biomedical subjects

J G Quinn

Publications and source records attributed to J G Quinn.

At least 19 recordsLinked to original sources
PubMed2001

Biosensor-based estimation of kinetic and equilibrium constants.

The steady-state affinity constant for the interaction of glutathione S-transferase (GST) with anti-GST immunoglobulin (IgG) was determined by solution-phase equilibrium analysis. A Biacore concentration assay for the determination of free anti-GST IgG was employed giving a Kd value of 6.83 x 10(-10) M. A simple 1:1 solution-phase, equilibrium model approximated the data well. Furthermore, saturation studies showed a maximum occupation of approximately 50%. The choice of affinity-capture ligand, used to anchor anti-GST IgG to the hydrogel, influenced the interaction curves, as evidenced by contact-time-dependent dissociation-phase curves. This was apparent when performing the analysis on anti-mouse Fc-coated surfaces. When the interaction was conducted on a protein A-coated CM5 sensor chip, the interaction conformed well to ideal behavior and was selected for kinetic analysis of the GST interaction.

Biosensing Techniques↗
PubMed2001

Relationships among total lipid, lipid classes, and polychlorinated biphenyl concentrations in two indigenous populations of ribbed mussels (Geukensia demissa) over an annual cycle.

Two indigenous ribbed mussel (Geukensia demissa) populations were sampled approximately every four weeks during 1997 to investigate the relationships among concentrations of total lipid, lipid classes, and polychlorinated biphenyls (PCBs). One population was located in a highly contaminated area near a Superfund site (New Bedford Harbor, MA, USA), while the other population was located at a relatively clean site (West Island, Fairhaven, MA, USA). Mussel tissue total PCB concentrations (quantified as the sum of 18 congeners) from the contaminated site were two orders of magnitude greater than those at the clean site. Total lipid and triacylglycerol (TG) also were higher at the contaminated site. No significant relationship (p > 0.05) was observed between total PCBs and total lipid at either location; however, the correlations at both sites increased when total PCBs were compared with total TG or, to a lesser extent, total nonpolar lipid. Principal component analysis and linear discriminatory analysis indicated that the two mussel populations could be distinguished by the proportions of their lipid classes, particularly the concentration of nonpolar lipids, which consisted mainly of TG. These results suggest that the standard method of normalizing organism PCB concentrations to total lipid may not be appropriate as a routine practice, especially when the organism has a relatively low total lipid content (<6% dry wt in this study).

Animals↗
PubMed2000

Development and application of surface plasmon resonance-based biosensors for the detection of cell-ligand interactions.

Surface plasmon resonance (SPR)-based biosensors were investigated with a view to providing a portable, inexpensive alternative to existing technologies for "real-time" biomolecular interaction analysis of whole cell-ligand interactions. A fiber optic SPR-based (FOSPR) biosensor, employing wavelength-dependent SPR, was constructed to enable continuous real-time data acquisition. In addition, a commercially available integrated angle-dependent SPR-based refractometer (ISPR) was modified to facilitate biosensing applications. Solid-phase detection of whole red blood cells (RBCs) using affinity-captured blood group specific antibodies was demonstrated using the BIACORE 1000, BIACORE Probe, FOSPR, and ISPR sensors. Nonspecific binding of RBCs to the hydrogel-based biointerface was negligible. However, the background noise level of the FOSPR-based biosensor was approximately 25-fold higher than that of the widely used BIACORE 1000 system while that of the ISPR-based biosensor was over 100-fold higher. Nevertheless, the FOSPR biosensor was suitable for the analysis of macromolecular analytes contained in crude matrices.

Biosensing Techniques↗
PubMed2000

Interference in visual working memory.

This paper uses the theoretical distinction that has recently developed between the passive visual store and the active spatial rehearsal mechanism of the visuo-spatial component of working memory (VSSP). It examines the circumstances under which visual fields gain functional access to the passive visual store and seeks to cast light on the circumstances under which irrelevant visual fields interfere with concurrent visual processing. Experiment 1 contrasts a dynamic visual noise field with a static noise field and shows that the static field, in contrast to the dynamic noise field, causes no interference when presented concurrently with a visual task. Experiment 2 investigates the reason for this contrast and concludes that the static field is susceptible to decay and so fails to cause interference. Experiment 3 investigates further the circumstances under which dynamic visual noise causes interference and shows that manipulation of the number of changes within the noise field is also of importance in causing interference. The results allow further consideration of the characteristics of the VSSP.

Adult↗
PubMed1997

Detection of blood group antigens utilising immobilised antibodies and surface plasmon resonance.

Surface plasmon resonance (SPR) detection using the BIAcore biosensing system was employed for the detection of blood group-associated antigens (BGAA) on whole erythrocytes. The quantitative detection of erythrocytes was accomplished by covalently immobilising blood group-specific antibodies (IgM) to a dextran matrix and monitoring the cell binding response. Non-specific binding of erythrocytes to the IgM coated surface was not detected. Relatively mild regeneration conditions (20 mM NaOH) were employed to elute bound erythrocytes in order to preserve the activity of the immobilised antibody and allow the surface to be used repeatedly. Regeneration of the surface was particularly difficult when a high IgM immobilisation level was used and when the number of bound cells was high. Despite these considerations, a quantitative relationship between the cell binding response and erythrocyte concentration was confirmed. Erythrocyte preparations, diluted by a factor of ten as compared to physiological concentrations, were detectable. The occurrence of non-specific false positives appears to be minimal and allows the system to be used for blood typing. As a model study, the lectin concanavalin A (ConA) was covalently immobilised onto a hydrophilic dextran matrix and successfully used to support the capture of erythrocytes from suspension.

Antibodies, Monoclonal↗
PubMed1996

Bispecific multivalent antibody studied by real-time interaction analysis for the development of an antigen-inhibition enzyme-linked immunosorbent assay.

A bispecific antibody with specificities for both 7-hydroxycoumarin (7-OHC) and alkaline phosphatase (AP) was produced by chemically cross-linking two parental polyclonal antibodies. Real-time interaction analysis of the bispecific multivalent antibody (bsMAb) was performed using BIAcore, a surface plasmon resonance (SPR)-based biosensor, in order to confirm its bispecific nature. A 7-OHC-BSA conjugate was covalently immobilized to a dextran matrix to serve as the reaction surface and unconjugated bovine serum albumin (BSA) was immobilized on to a separate dextran matrix as a control surface. Immunoaffinity-purified bsMAb, parental anti-7-OHC antibody and AP were injected over both surfaces. The bsMAb was shown to bind both antigens, 7-OHC and AP, simultaneously. Comparison of the ratio of mass bound for bsMAb and AP (5:1) with the ratio of the molecular masses of bsMAb (approximately 300 kDa) and AP (85 kDa) (3.5:1) suggests that most of the bsMAb species possess both specificities. The bsMAb was employed in a one-step antigen-inhibition ELISA for the detection of 7-OHC. The assay was compared with a conventional ELISA approach employing an AP-labelled secondary antibody. The bispecific antibody approach proved to be faster and more sensitive, with a detection limit of 6 ng ml-1 as compared with approximately 50 ng ml-1 for the conventional approach. The assay was used for the quantification of free and total 7-OHC in urine samples from two healthy volunteers who had been administered coumarin. The accuracy and precision of the assay were assessed. The bispecific antibody-based assay gave similar results, accuracy and precision, but proved to be far more sensitive (limit of determination 6 ng ml-1 for total 7-OHC). It is concluded that real-time interaction analysis using BIAcor provides a rapid method for the evaluation of the bsMAb and it was verified that the bispecific product formed by chemical cross-linking of two parental antibodies offers a simple alternative for the development of a highly sensitive ELISA.

Alkaline Phosphatase↗
PubMed1996

Irrelevant pictures in visual working memory.

The aim of the paper is to establish firmly the phenomenon of an irrelevant picture effect and to demonstrate that the phenomenon can be used to investigate the characteristics of the visuo-spatial sketchpad. Experiment 1 introduces the use of dynamic visual noise as an interfering technique. This technique is shown to cause interference with a word list learned under visual mnemonic mediation instructions but to cause no interference when the word list is learned under verbal mediation instructions. Experiment 2 serves both to replicate this selective interference effect and to illustrate how the dynamic visual noise technique can be used to characterize further the nature of interference in the visuo-spatial sketchpad. Experiment 3 confirms the robustness of the dynamic visual noise technique. Additionally, this experiment demonstrates a double dissociation between two types of interference, dynamic visual noise and irrelevant speech, and two types of mediation, rote and visual mnemonic.

Adult↗
PubMed1994

Towards a clarification of spatial processing.

Three experiments that adopt an interference paradigm to investigate characteristics of a type of movement causing interference with spatial processing are reported. Experiment 1 illustrates the importance of distinguishing between movement and attention to movement when investigating the movement characteristics of spatial processing. The technique of passive movement is used to minimize attention in the subsequent experiments. Experiment 2 confirms earlier experiments showing that passive movement causes interference in spatial processing. However, it extends the previous findings by demonstrating that passive movement is detrimental to spatial processing only when the movement is to a sequence of locations known in advance by the subjects. Experiment 3 demonstrates that the movement interference cannot be interpreted as a general interference effect but that it is selective for spatial processing. The results of these experiments permit a more precise delineation of the disruptive effects of movement in spatial processing and allow an explicit definition of spatial processing to be put forward.

Attention↗
PubMed1972

Enrichment of heavy metals and organic compounds in the surface microlayer of Narragansett Bay, Rhode Island.

Concentrations of lead, iron, nickel, copper, fatty acids, hydrocarbons, and chlorinated hydrocarbons are enriched from 1.5 to 50 times in the top 100 to 150 micrometers of Narragansett Bay water relative to the bulk water 20 centimeters below the surface. Trace metal enrichment was observed in the particulate and organic fractions but not in the inorganic fraction. If these substances are concentrated in films only a few molecular layers thick on the water surface, the actual enrichment factor in the films may be well over 10(4), resulting in extremely high localized pollutant concentrations in the surface microlayer.

Copper↗