Biosensor Applications (Sweden)

<p>VOCs correspond to a large number of species which in turn can be categorized into different chemical groups such as: alkanes (e.g. methane, propane, butane etc.), alcohols (e.g. ethanol and propanol, alkenes (e.g. ethene and propene), aromatic hydrocarbons (e.g. benzene and toluene) and aldehydes (e.g. formaldehyde and acetaldehyde). VOCs contributes to the formation of ground level ozone, which is formed through atmospheric chemical reactions of volatile organic compounds and nitrogen oxides (NOx) in the presence of sunlight. Elevated ozone concentrations are known to reduce crop yields and constitute a public health concern and has a climate impact similar to N2O.</p> <p>Stationary sources such as refineries, storage depots, petrochemical facilities and oil production activities are the largest point sources of VOCs. The emissions are typically dominated by evaporative losses from storage tanks and process equipment, so-called diffuse emissions. Several VOCs are also toxic with direct impact on health such as benzene and formaldehyde.</p> <p>In this study, we will show results from measurements in 2021 of diffuse emissions of CH4 and NMVOCs from oil production sources in California using optical methods. At Chalmers, several unique optical techniques have been developed. Two of the techniques, the solar occultation flux (SOF) method, Fig 1, and mobile sky DOAS, measure the gas columns of VOCs and NO2, SO2, and formaldehyde, respectively, and from these measurements, it is possible to derive the gas emissions from a certain source by combining with wind speed. The other two techniques, Mobile extractive FTIR and Mobile extractive DOAS yield the ground concentration of multiple species. Emissions of VOCs, methane and air toxics from several of California’s largest-producing oil fields in Kern County were measured. A total of 4500 kg/h of alkanes and 8900 kg/h of methane were measured from 11 fields.  These data have been compared to emission models.</p>

The drain current-voltage (I-d-V-D) characteristics of a chemical gas sensor based on a catalytic metal insulator silicon carbide field effect transistor (SiC-FET) were measured in H-2 or O-2 ambient while applying negative substrate bias, V-sub, at temperatures up to 600degreesC. An increase in the negative V-sub gives rise to an increase of the drain voltage at a given drain current level, which can be used to adjust the device baseline. In addition, we found that the difference in drain voltage between H-2 and O-2 ambient at a given drain current level (the gas response to H-2) increases for an increased negative substrate bias. By modifying an equation for the drain current in a SIT (static induction transistor), the influence of substrate bias on the amplification factors, mu and eta, was estimated using the temperature dependence of the I-d-V-D characteristics. From this, the effect of substrate bias on the gas response to hydrogen was calculated. It was clarified that the increase in the gas response caused by the negative substrate bias is due to a substrate bias dependence of the amplification factor of the short channel device.

Abstract

We have studied quantitatively the effect of the corepressor, S-adenosylmethionine (SAM), on the interaction between the E. coli methionine repressor, MetJ, and an idealised operator fragment, by recording measurements of surface plasmon resonance using a BIAcore instrument. We have recorded kinetic binding data in the presence of SAM, which carries a net positive charge, and two corepressor analogues, adenosylornithine (AO) and aza-SAM, which differ in the location of the atom carrying the positive charge. Our data support the hypothesis that the effect of the corepressor is electrostatic in origin. The difference in electrostatic interaction energy between the SAM- and AO-repressor-operator complexes of approximately 3.5 kJ/mol calculated from the known three-dimensional structure is within the range of our experimentally determined values of 2.8-4.3 kJ/mol. These results illustrate the potential of SPR measurements for studying protein-nucleic acid interactions.

The authors have recently described the development of a carboxymethyl dextran-based sensor surface for biospecific interaction analysis by surface plasmon resonance. Ligands are immobilized via primary amine groups after activation of the carboxymethyl groups on the sensor surface with a mixture of N-hydroxysuccinimide and N-ethyl-N'-(dimethylaminopropyl) carbodiimide. Methods have now been developed for efficient immobilization via thiol/disulfide exchange, aldehyde coupling and biotin-avidin coupling. The specific activity of monoclonal antibodies immobilized by the four different methods was investigated by altering the immobilization conditions, e.g., activation time, protein concentration, ionic strength and the degree of modification, etc. Investigations have also been made concerning possible differences in the specific activity for antibodies immobilized using optimized conditions with respect to the four different chemistries. These studies show that, with the flexible carboxymethyl dextran matrix used here, the immobilization methods give rise to only minor differences in specific activity. Thus, with this solid support, a 'site directed' immobilization strategy for monoclonal antibodies has no advantage. In general the specific activity for optimized systems was approximately 75% for the binding of beta 2 mu-globulin to an immobilized monoclonal antibody directed against beta 2 mu-globulin. Reduced specific activities of immobilized antibodies induced by variation of the coupling conditions could be attributed to the deterioration of the active site of the antibody.

Journal Article Study of protein-DNA interactions by surface plasmon resonance (real time kinetics) Get access Jean-Pierre Jost, Jean-Pierre Jost Search for other works by this author on: Oxford Academic PubMed Google Scholar Oliver Munch, Oliver Munch Search for other works by this author on: Oxford Academic PubMed Google Scholar Thomas Andersson Thomas Andersson 1Pharmacia Biosensor ABRapsgatan 7, Hus F61, S-75182, Uppsala, Sweden Search for other works by this author on: Oxford Academic PubMed Google Scholar Nucleic Acids Research, Volume 19, Issue 10, 11 May 1991, Page 2788, https://doi.org/10.1093/nar/19.10.2788 Published: 25 May 1991 Article history Accepted: 27 March 1991 Published: 25 May 1991